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    • 专利摘要:
    The present invention relates to a method and method for using dry etching to obtain a surface free of contamination for a material selected from the group comprising GaAs, GaAlAs, InGaAsP, and InGaAs to obtain a nitride layer on any structure for a GaAs-based laser. Therefore, the present invention relates to a manufactured GaAs laser. The laser surface is provided with a mask that masks its surface portions to be protected from dry etching. Next place the laser in vacuum. Next, dry etching is performed using a material selected from the group containing chemically reactive gases, inert gases, mixtures between chemically reactive gases and inert gases. A nitrogen containing plasma is used to create the natural nitride layer. A protective layer and / or mirror coding is added.
    公开号:KR20040035729A
    申请号:KR10-2004-7002006
    申请日:2002-08-09
    公开日:2004-04-29
    发明作者:린드스트롬엘.카르스텐브이.；블릭스트피터엔.；쇼더홀름스반테에이치.；크룸메나체르라우렌트；실프베니우스크리스토퍼；스리니바산아난드；칼스트롬칼-프레드릭
    申请人:컴라세 에이비；
    IPC主号:
    专利说明:

    Method for Baas-based lasers and Baas-based lasers TECHNICAL FIELD
    [4] High power 980 nm laser diodes are commonly used in erbium-doped fiber amplifiers (EDFAs). Other applications could be thulium doped fiber amplifiers and waveguides using Er / Yb doped fibers and rare earth metal transitions in the 900 ... 1100 nm band. There are two major failure mechanisms for GaAs-based pump lasers called laser surface degradation and defects in the waveguide. Degradation of the laser plane due to light absorption is known to cause sudden failure due to sudden optical damage (COD) and was one of the major causes of device failure. If the COD can be handled by a suitable laser face passivation technique, waveguide defects will be suppressed.
    [5] The loss in the waveguide is:
    [6] Light scattering due to roughness in the waveguide;
    [7] Resulting from non-radiative recombination by impurities at the surface or by recombination by surface conditions.
    [8] Wet chemical etching processes typically provide good smoothness to the waveguide. Previous dry etching methods, such as reactive ion etching (RIE) or chemically assisted ion beam etching (CAIBE), result in very high process control in terms of both etch depth and wall phase. However, these dry etching methods provide a rougher surface than the wet etching method. Rougher surfaces increase surface recombination as well as light scattering. Both effects are detrimental to modern pump lasers. Scattering will reduce efficiency. Impurities entering through rough, non-blocked surfaces are even more harmful to pump lasers. Impurities and surface conditions will promote non-radiative recombination that generates heat. Heat can further degrade the material and surface, and more heat will be generated. This process will be accelerated and eventually the device will fail.
    [9] Related technology
    [10] US 4448633 discloses a passivation method by exposing a type III-V compound semiconductor surface to low pressure nitrogen plasma. Element III forms element III-nitride. This process is called nitriding. The resulting article has a III element-nitride surface layer, which protects the article from environmental degradation while lowering the surface state density and allowing reversal of the surface layer. Nitriding is carried out in two steps. The first occurs at low temperatures (400-500 ° C), which prevents surface degradation due to the loss of element V. Exposure to nitrogen plasma with a pressure of 0.01-10 Torr results in an initial III-nitride layer with a thickness of about 20-100 kPa. The second step is performed at elevated temperature (500-700 ° C.) under the same plasma conditions. Here, nitriding proceeds at a faster rate, resulting in a thicker nitride layer (200-1000 kPa). Under the conditions of the present invention, if the plasma pressure is in the range of 0.01 to about 0.5 Torr, the resulting III-coating is polycrystalline and single crystal when the pressure is in the range of 1 to 10 Torr.
    [11] US 5780120 describes a method of making the side of a laser based on III-V compound. The method includes the following tasks:
    [12] 1) Cut the surface of the laser
    [13] 2) The face of the laser is placed in an enclosure containing a pressure of about 10-7 millibars to about 10-8 millibars, and they enter the stage of cleaning by irradiating with a pulsed laser.
    [14] 3) The same pulsed laser is used to remove the target to direct the exposed side to passivation, which deposits 2-20 μs of Si or GaN.
    [15] Deposition can be performed by pulsed laser ablation of liquid gallium targets in a nitrogen atmosphere with an Electro Cyclotron resonance (ECR) plasma. Deposition of additional films such as Diamond Like Carbon (DLC), silicon carbide SiC, or silicon nitride Si 3 N 3 can be deposited using the same pulsed laser. These coatings are transparent and oxidation resistant at the wavelength of the laser. The washing step prior to the passivating step may be performed in an atmosphere of chlorine or bromine, using a pulsed excimer laser. This document suggests that if GaN is deposited instead of Si, no additional coating is needed. This also suggests that the III-N layers are oxygen-proof.
    [16] US 5834379 describes a process for synthesizing a wide band gap material, in particular GaN, using plasma-assisted thermal nitriding with NH 3 to convert GaAs to GaN. This method can be used to form layers of significant thickness (in order of 1 micron) of GaN on a GaAs substrate. Plasma-assisted nitriding with NH 3 predominantly results in the formation of cubic GaN. The purpose of this document is to create a sufficiently thick GaN layer and is not directly involved in laser face passivation. However, the basic principle relies on nitriding using a plasma source. Such an approach is used for the growth of GaN films.
    [17] The patents emphasize the concept of nitriding III-V semiconductors using nitrogen plasma.
    [18] US4331737 describes oxynitride films containing Ga and / or Al and having an O / N ratio of at least 0.15. This film is obtained, for example, by relying on chemical vapor deposition (CVD) techniques. The ratio of O / N in the film can be changed, for example, by changing the distance between the substrate and the material-source or by changing the proportion of oxidizing gas contained in the carrier gas. Such a film is used as a surface passivation film of a III-V compound semiconductor such as GaAs or as an insulating film for an active surface portion of an IG-FET, or as an optical antireflection film.
    [19] EP0684671 describes a method comprising oxide reduction, hydrogen passivation and deposition of a protective coating layer. The method involves the same PECVD reactor for all steps to avoid oxygen exposure. The cut surface (exposed to air and thus oxidized) is loaded into the reactor. The first step uses a hydrogen plasma, which all reduces the Group V oxide content and passivates the non-radiative recombination center. Group III oxides are removed by ammonia plasma and the laser side has their composition stoichiometry restored and free of contaminants. The coating is then done by depositing SiN (x) or AlN (x). Minimum stress can also be obtained through the generation of compositional nitrogen gradients.
    [20] US 5668049 describes a method of making a GaAs-based semiconductor laser. Fully processed wafers are typically cut with a laser bar in the atmosphere. The laser bar is loaded into a dischargeable deposition chamber (preferably an ECR CVD chamber) and exposed to an H 2 S plasma. Hydrogen is believed to remove native oxides, while sulfur combines with Ga and As, thereby lowering the surface state density. After exposure, the split sides are coated with a protective dielectric (eg, silicon nitride) layer in the chamber. The patent allows the method to be run at high throughput and yield a laser that can operate at high power.
    [21] US5144634 discloses a method of passivating a mirror in the process of fabricating a semiconductor laser diode. The main steps of the method are:
    [22] (1) providing a mirror surface free of contamination, and then
    [23] (2) Applying a continuous, insulating (or low conductivity) passivation layer in-situ.
    [24] This layer is formed of a material that acts as a diffusion barrier for impurities that can react with the semiconductor but do not react with the mirror surface itself. The contamination free mirror surface is obtained by cutting in a pollution free environment or by cutting in air, then mirror etching and then cleaning the mirror surface. The passivation layer is composed of Si, Ge or Sb. Si layers with a second layer containing Si 3 N 4 are also claimed.
    [25] EP0474952 proposes another method of passivating the etched mirror surface of a semiconductor laser diode to improve the reliability of the device. The etched mirror surface is first sent to a wet etching process to substantially remove any natural oxides as well as any surface layer that could have been mechanically damaged during the previous mirror etching process. Thereafter, the passivation pre-treatment agent is applied and thereby any residual oxygen is removed and a sub-single-layer is formed which permanently reduces the non-radiative recombination of minority carriers in the mirror plane. As pre-treatment agent, Na 2 S or (NH 3 ) 2 S solution can be used. Sulfur passivates the surface electronic state, which otherwise becomes an effective non-recombination center. Finally, the pre-treated mirror surface is coated with Al 2 O 3 or Si 3 N 4 to avoid any environmental impact.
    [26] EP0774809 describes a method for providing a novel passivation layer that can result in improved reliability of a semiconductor laser having a laser cavity defined by the laser plane. In a preferred embodiment, the passivation layer is essentially a zinc selenide layer, formed on the contamination-free laser surface (eg 5 nm). More generally, the passivation layer comprises at least one of Mg, Zn, Cd and Hg, and at least one of S, Se and Te. Typically, the faces are formed by cutting in vacuo followed by in situ deposition of a new passivation layer material on the face.
    [27] US5851849 describes a method for passivating a semiconductor laser structure at a strict stage in surface topography. The technique involves atomic layer deposition to produce passivation layers with excellent coverage and uniformity, even for trench appearances with trench aspect ratios as high as five. In addition, the passivation produced by this process has excellent environmental stability and provides protection against quality degradation caused by airborne contamination. The coating process is carried out in a vacuum chamber. The main feature of the process is the formation of a coating by multiple process cycles, each cycle essentially making an equivalent monolayer of passivation film. In certain embodiments described herein the passivation film was Al 2 O 3 and the reaction gas was trimethylaluminum [(CH 3 ) 3 Al].
    [28] The patent mainly addresses other passivation methods. Typically, the process is complex and involves at least two steps. In some cases, special techniques and / or materials (gases, precursors, etc.) are used. Nevertheless, most of these deal with measures to reduce surface state density, which is one of the important factors that inhibits COD.
    [29] "Cleaning of GaAs Surfaces with Low-Damage Effects Using Ion-Beam Milling" by C. Lindstrom and P. Tihanyi, the Journal IEEE Trans.on electron Devices, Vol.ED-30, NO.6, June 1983. The etch depth of 50-100 mm 3 with ion-beam milling of the surface reduces the percent of oxygen atoms by 97-99% as determined by Auger depth profiling. The same report demonstrated the difference between milling to heavier Ar ions and lighter N ions. An important result was that milling with Ar ions negatively affected performance in the milling process, while N ions had no measurable detrimental effect on laser diode performance. After 140 kW milling depth with Ar ions, the power output and power conversion efficiency began to decrease. However, the introduction of N ions in the milling process showed no parameter change for the milling depths studied, ie 200 mm 3.
    [30] The effect on laser performance of Ar ion milling followed by N ion milling is also described in this paper. Here, the lighter N ions eliminate the damage caused by the heavier Ar ions and restore deteriorated power output performance. The conclusion from these observations is that N ion milling smooths the mirror plane, resulting in a uniform surface similar to that observed for mechanically cut surfaces in the crystal plane, with a correspondingly reduced number of surface states.
    [31] Paper "Low resistance ohmic contacts an nitrogen ion bombarded InP", Ren et al, Appl. Phys. Lett. 65, 2165 (1994) report the electrochemical properties of InP surfaces milled by low energy (100-300 eV) nitrogen ions. Incorporation of nitrogen was demonstrated by Secondary Ion Mass Spectroscopy (SIMS) analysis and polycrystalline InN formed was confirmed by transmission electron microscopy (TEM). In the process, the native oxide on the sample surface is also removed by milling.
    [32] The article "Nitridatoin of an InP (100) surface by nitrogen ion beams", Suzuki et al, Appl. Surf. Sci. 162-163, 172 (2000) describe the study of nitriding of InP 100 by low energy nitrogen ion milling. The researchers used X-ray photoelectron microscopy (XPS) for chemical analysis and to confirm the binding state. Ion energy ranged between 100 eV and 1 KeV. The milled surface shows In-N, In-N-P and P-N bonding states. Loss of In-N-P when annealed (400 ° C.) suggests a lower binding energy for these bonds compared to In-N. However, the nitriding efficiency decreases with increasing ion energy due to sputter corrosion.
    [33] Paper "Characterization of damage in InP dry etched using nitrogen containing chemistries", C. F. Carlstrom and S. Anand, submitted to J. Vac Sci. Technol. B (March 2001) emphasizes the etching of InP using other processes containing nitrogen in etch-chemistry, including nitrogen ion milling. The surface is very smooth with milling rms. Roughness <1 nm with milling at 75 eV. There is a nitrogen containing layer near the thin surface. High temperature treatment under phosphine (650 ° C.) removes most of the entrained nitrogen.
    [34] Paper "Synthesis of InNxP1-x thin films by N ion implantation", Yu et al, Appl. Phys. Lett. 78, 1077 (2001) describes the injection of nitrogen, which is performed to form dilute InNxP1-x layers. Nitrogen ions were sequentially implanted with selected energy to form 350 nm thick layers, and an InNP alloy layer was formed upon rapid thermal annealing (RTA) in flowing nitrogen (with an adjacent cap).
    [35] Although the papers focus on other issues, the message is the incorporation of nitrogen into InP during nitrogen ion milling. In addition, the results suggest that N binds to both In and P, the latter being less stable. The nitriding process needs to be optimized to predominantly have In-N in the layer. At the same time the surface should be smooth. The last work listed above (Yu et al.) Provides another means of forming a nitrided layer, but with the limitation that not all In—N layers are obtained. However, it suggests that after nitriding by ion milling, it may be an additional step that may require RTA.
    [36] Nitriding of GaAs received great attention. One of the main concerns has been to reduce surface state density and the focus is often on metal insulator semiconductor (MIS) structures. (However, the methodology and / or results could also be effective for laser-face fabrication.) Below are a few selected references that have more interest in plasma assisted nitriding configurations.
    [37] The article "Nitridation of GaAs using helicon-wave excited and inductively coupled nitrogen plasma", Hara et al, J. Vac. Sci. Technol. B 16, 183 (1998) describes the nitriding of GaAs by special plasma treatments containing nitrogen and argon and / or a mixture of nitrogen and oxygen. However, no pure nitrogen plasma is mentioned. The authors show that by X-ray photoelectron spectroscopy (XPS) analysis, Ga-N bonds are formed and only a small amount of Ga and As-dependent oxides are found under certain conditions. Shows. The author used this procedure to study the C-V characteristics of MIS devices and found improvements. Moreover, photoluminescence yield is high for treated samples that exhibit lower surface / interface density. This work obviously focuses on the MIS perspective and there is no mention that the same process is applicable to pump lasers.
    [38] The article "Surface cleaning and nitridation of compound semiconductors using gas-decomposition reaction in Cat-CVD method ', Izumi et al, Proc. Int. Vac. Congress, Aug. 31-Sep. 4, Burmingham, UK 1998, cleaned the GaAs surface. We describe the use of gas-decomposition reactions involving ammonia in a catalytic CVD (cat-CVD) system for the purpose of sintering and nitriding, and the authors use XPS to study the state of chemical bonding near the surface. The suggestion is that the loss of ammonia results in the removal of oxides, generating hydrogen to clean the surface, and the exchange reaction to produce nitrogen that forms Ga-N, ie nitrogen efficiently This task refers only to MIS applications.
    [39] The article "Nitridation of GaAs (110) using energetic N + and N2 + ion beams", L. A. DeLouise, J. Vac. Sci. Technol. A 11, 609 (1993) and "Reactive N 2+ ion bo millibarment of GaAs (110): A method for GaN thin film growth", J. Vac. Sci. Technol. A10, 1637 (1992) analyzes the nitriding of GaAs 110 when bombarded using nitrogen ion-beams (500 eV to 3 KeV) using XPS. Lower surface densities are obtained in nitrogen compared to Ar and prove to contribute to the formation of predominantly stable Ga-N bonds. In addition, both of these papers mention MIS-like applications and have relatively high ion energies.
    [40] Paper "NH 3 plasma nitridation process of 100-GaAs surface observed by XPS", Masuda et al, JJ Appl. Phys. Part 1, 34 1075 (1995) describes an XPS study of the nitriding of GaAs showing the formation of a Ga-As-N layer using ammonia plasma. However, under certain conditions, the authors claim the formation of the only Ga-N layer due to the desorption of As. They also report that the layer is oxidation resistant.
    [41] Paper "XPS investigation of GaAs nitridation mechanism with an ECR plasma source", Sauvage-Simkin et al, Phys. Stat. Solidi A176, 671 (1999) describes the formation of beta-GaN in GaAs samples exposed to nitrogen ECR plasma from XPS studies. Amorphous layer formation is demonstrated, which can support nitrogen incorporation, but must be controlled to stabilize Ga-N bonds.
    [42] Paper "III-V surface plasma nitridation: A challenge for III-V nitride epigrowth", Losurdo et al, J. Vac. Sci. Technol. A17, 2194 (1999) describes the efficiency of increased nitriding in the presence of hydrogen. It is proposed that hydrogen improves the desorption of group V elements.
    [43] "Nanometer scale studies of nitride / arsenide heterostructures produced by nitrogen plasma exposure of GaAs", Goldman et al, J. Electronic Mat. 26, 1342 (1997) describe the use of a scanning tunneling microscope (STM), a complex tool for investigating the plasma nitridation of GaAs. The authors found that the nitrided layer was not a continuous membrane and also found some other work reported above. Instead it consists of defects (As-N) and clusters (GaN with dilution As). These results show that defects can also be formed that can be detrimental to device performance. However, if proper nitriding conditions and possible annealing steps are used, defects can be minimized.
    [44] Paper "Surface passivation of GaAs by ultra-thin cubic GaN layer", Anantathasaran et al, Appl. Surf. Sci. 159-160, 456 (2000) describe the use of nitrogen plasma to form thin cubic GaN layers and the use of XPS and RHEED to analyze samples. All these processes were performed under Ultra High Vacuum (UHV) conditions. PL measurements show an order of grade increase in strength compared to grown samples that exhibit good passivation properties of the nitrided layer.
    [45] The main importance from the literature is that nitriding of GaAs is possible using nitrogen plasma. Some of these papers also highlighted nitriding by nitrogen-ion bombardment. Most reported work mentions the MIS structure for stimulation and makes no explicit mention of pump-laser plane passivation by nitriding. Some reports also show that the nitrided layers formed are non-uniform and require some additional process steps such as annealing.
    [46] Two papers describe the passivation of the laser plane.
    [47] Paper "Reliability improvement of 980 nm laser diodes with a new facetpassivation process", Horie et al, IEEE Jour. of selected topics in quantum electronics 5, 832 (1999) describe improved laser performance with three-stage face fabrication. The laser bar is cut in air, thus increasing the yield. However, the cotton manufacturing process involves three steps achieved under vacuum, which makes the process somewhat complicated. The process itself involves low energy Ar-ion milling followed by Si-layer deposition followed by AlOx coating layer deposition. The problem here is that after Ar-milling, the surface cannot be exposed to the ambient air. Nothing is mentioned about nitrogen milling.
    [48] The paper "A highly reliable GaInAs-GaInP 0.98 [mu] m window laser", Hashimoto et al, IEEE J of quantum electronics 36, 971 (2000), induces nitrogen injection and subsequently in-diffusion near the active region in terms of Describe the use of the RTA. The basic mechanism is the generation of defects by selective nitrogen injection. When RTA, defects help increase atomic in-diffusion and increase band-gap near the plane (window laser). However, in this work the authors do not give details such as injection. The nitriding effect, more precisely the formation of dilute nitrogen containing alloys, is not explained. Nevertheless, their process of nitrogen injection and RTA shows a band gap increase of about 100 meV as can be seen from the photo-luminescence (PL) measurements.
    [49] L. Houlet et al., "Simulation of mesa structures for III-V semiconductors under ion beam etching", Eur. Phys. J. AP Vol 6, p. 273-278 (1999) discusses other forms obtained by ion-milling on mesa using several schematic examples. Those related to angle dependence on milling, mask erosion, mask-edge face exposure and their etch profile development are discussed.
    [1] The present invention relates to a method for obtaining a nitride layer on an arbitrary structure for a GaAs-based laser, and to a GaAs-based laser provided by the method.
    [2] The present invention primarily refers to a method for processing losses in a waveguide of a GaAs-based laser.
    [3] A method for dealing with problems associated with deterioration of the laser plane is disclosed in co-pending US patent application Ser. No. 09/924605.
    [115] For a more complete understanding of the invention and further objects and their advantages, reference is made to the following description of these embodiments, as shown in the accompanying figures, in which:
    [116] 1A-1D show a process for manufacturing a semiconductor laser;
    [117] 2 shows a cross section perpendicular to the laser beam direction for the laser of the first embodiment according to the invention and shows a ridge on the active laser layer;
    [118] 3 is a perspective view in partial cross section of a wafer according to the laser structure of a second embodiment according to the invention;
    [119] 4 shows a cross section parallel to the laser beam direction for the laser of the third embodiment according to the invention and shows a corrugated surface over the active laser layer;
    [120] 5A and 5B show a cross section parallel to the laser beam direction for the laser of the fourth embodiment according to the present invention, showing a surface provided with a hole over the active laser layer and a perspective on the same embodiment;
    [121] 6 shows a cross section parallel to the laser beam direction for a wafer of a fifth embodiment that includes a laser chip performed directly on the wafer.
    [50] Problem description
    [51] Two methods, called dry and wet etching, are basically used for forming a laser waveguide of a GaAs-based pump laser, a GaAs substrate having a ternary system such as a GaAlAs active layer or a quaternary system such as an InGaAsP active layer, or a GalnP active layer.
    [52] Dry etching methods are typically:
    [53] Rough surface providing scattering loss of laser beam which reduces output power.
    [54] Absence of a passivation layer that blocks impurities from reaction with the semiconductor material.
    [55] It is hindered by a large number of surface conditions and rough surfaces which will result in high non-radiative recombination.
    [56] Wet chemical etching has the following problems:
    [57] Bad process control.
    [58] The phase is very limited due to the isotropic etch rate.
    [59] Wet chemicals contain large amounts of impurities. Lack of precise cleaning of the surface.
    [60] Hindered by the absence of a natural passivation layer to block impurities.
    [61] The present invention
    [62] It is an object of the present invention to provide a method for obtaining a nitride layer over any structure for a GaAs-based laser through dry etching that minimizes scattering losses.
    [63] It is another object of the present invention to provide a method for obtaining a nitride layer over any structure for a GaAs-based laser through dry etching that blocks any impurities that react with the active material.
    [64] It is still another object of the present invention to provide a method for obtaining a nitride layer over any structure for a GaAs-based laser via dry etching with low surface state density.
    [65] Yet another object of the present invention is to provide a method for obtaining a nitride layer over any structure for a GaAs-based laser through dry etching that provides a smooth surface and low surface recombination rate.
    [66] Yet another object of the present invention is to provide a method for obtaining a nitride layer over any structure for a GaAs-based laser via dry etching, which provides a laser structure that causes minimal heat generation.
    [67] The method in the present application refers to dry etching the structure on the epitaxial layer side of the wafer and then forming a natural nitride layer on the same structure.
    [68] Several structures that can be formed by the dry etching method according to the invention, also known as:
    [69] Ridge or mesa-structures for forming waveguides
    [70] Trenches, for example to form waveguides, cut off current, or for improved thermal conductivity.
    [71] A corrugated periodic structure with sub-micron resolution, such as, for example, DFB and DBR structures.
    [72] Etched face exists
    [73] Additional nitride layers are:
    [74] (i) filling the pinhole;
    [75] (ii) flattening: and
    [76] (iii) has a thermal conductivity that is better than GaAs and air and can be applied to remove heat.
    [77] The method according to the invention is preferably carried out after the etching process, such as milling with a gas containing atomic nitrogen or nitrogen ions in a vacuum chamber, while the first fabricated several laser chips are still present on the wafer. Nitriding the surface. The etching process begins to form the laser channel (s) to make mesas, ridges, trenches, corrugations, facets, and the like against the laser surface. The introduction of a reactive gas such as nitrogen during the etching process will necessarily affect the crystalline surface properties because it reacts with the crystalline element to produce a nitrided surface layer.
    [78] Thus, the etching process is carried out using chemically reactive gases and inert gases and mixtures therebetween, in particular argon, nitrogen, hydrogen and chlorine. Subsequent nitriding is performed by a plasma containing nitrogen in ionic or atomic form.
    [79] The essential concept behind this nitriding is the laser surface / face
    [80] (a) prevent chemical contamination (eg oxidation),
    [81] (b) provide a higher band-gap surface layer, and
    [82] (c) if possible also the formation of a nitride layer that reduces the rate of surface / interface carrier recombination.
    [83] By laser surface is meant a surface comprising ridges, mesas, corrugations, trenches, and the like. By laser plane is meant the front and rear laser planes most often perpendicular to the laser surface.
    [84] During ion milling the laser surface / surface, hydrogen gas
    [85] (a) because hydrogen is known to be effective in removing surface oxides, it helps to clean the laser surface surfaces, especially oxidized areas more effectively,
    [86] (b) assist in the removal of group V elements from the III-V crystals, making the formation of group III-nitrides more advantageous.
    [87] The nitrided surface layer thus formed on the laser surface during nitrogen ion milling, if possible, by subsequent deposition of an additional nitride film, which may contain metals in groups 3a and 4a, such as any of the following elements: Si, Ga, In particular, it can be improved to flatten surface obstacles and pinholes.
    [88] Surfaces without contamination are any of the following:
    [89] (a) a surface nitrided layer so formed by nitrogen ion milling (with or without hydrogen),
    [90] (b) with an additional layer of surface nitrided layer and deposited nitride film so formed by nitrogen ion milling (with or without hydrogen), or
    [91] (c) gentle nitrogen ion milling followed by nitriding with neutral atomic nitrogen.
    [92] Prior to coating, the so-generated, contamination-free surface may be enclosed by a passivation layer having properties that minimize the non-radiative carrier recombination at the nitride-passivating layer coating interface. In contrast, direct deposition of the coating onto such a non-contaminated surface may result in proper non-radio carrier recombination by the interface state at the nitride-mirror coating interface.
    [93] Accordingly, the present invention provides a dry etch for obtaining a contamination-free (GaAlAs-InGaAs) surface for materials selected from the group comprising GaAs, GaAlAs, InGaAs, InGaAsP and InGaAs to obtain a nitride layer on any structure for a GaAs-based laser. To a method, wherein the method
    [94] Providing a mask on the laser surface that masks its surface portions to be protected from dry etching;
    [95] Leaving the laser in the vacuum;
    [96] The following materials: performing dry etching using a chemically reactive gas, an inert gas, a mixture between the chemically reactive gas and the inert gas;
    [97] Generating a natural nitride layer using the extracted beam and using a plasma containing nitrogen;
    [98] Adding a protective layer and / or a mirror coating.
    [99] Processes are chemically inert and reactive such as nitrogen, hydrogen, argon and halogen compounds (eg Cl, Br, or I-based compounds) and hydrocarbon gases (eg CH 4 and C 2 H 6 ), and mixtures thereof. The method may further include initiating a dry etch using a material assisted plasma comprising one or more materials from the group comprising the gas. The cotton may be passivated after using a nitrogen assisted plasma to obtain a surface free of contamination. Dry etching may be performed with a nitrogen assisted plasma, or a plasma in which the material is a mixture of nitrogen and other gases, and the other gases are gradually replaced with nitrogen until only a nitrogen plasma is provided. Dry etching may also be performed with a gas free of nitrogen, which is gradually replaced by nitrogen until a nitrogen plasma is provided. The nitrogen plasma may contain nitrogen ions, atomic nitrogen or molecular nitrogen.
    [100] Hydrogen may be added to the material assisted plasma to enhance the removal of oxides.
    [101] The milling mass may be argon. The nitride layer then begins to grow on the uncontaminated surface while introducing elements from the group comprising ionized nitrogen, atomic nitrogen, and molecular nitrogen into the material assisted plasma, and during reaction with the uncontaminated surface. In order to minimize interfacial recombination between the different layers, natural nitriding is used to gradually create an interface between the unpolluted surface and the grown nitride layer.
    [102] The nitride layer uses a plasma, preferably containing nitrogen, with the extracted beam, and the nitride layer is comprised of one or more materials selected from the group comprising AlN, GaN, InN, InAsN. Further in-situ or ex-situ deposition of a thin nitride film over the natural nitride layer using a reactive plasma in combination with one or more elements from groups 2b, 3a, 4a, and 5a such as Si, Ga, Zn, Al. It is preferably provided. One or more additional films may be added to further reduce interfacial surface recombination prior to the addition of the protective layer and / or mirror coating. Additional thin films or films may be added after the in-situ or ex situ deposition of thin films to further reduce interfacial surface recombination prior to providing the protective layer and / or mirror coating.
    [103] The vacuum may be between 10 Torr and 10 −11 Torr, preferably less than 10 −7 Torr. The gas may be selected from one or more elements from the group containing argon, nitrogen, hydrogen and chlorine. In dry etching, the smooth surface shape can be enhanced to a specific energy range 0 to 2000 eV, in combination with alternating beam incidence angles from 0 ° to 90 ° from the normal angle of incidence. The smooth surface morphology in dry etching can also be done in a specific energy range of 50 to 500 eV in combination with alternating beam incidence angles from 0 ° to 85 ° from the normal angle of incidence. Nitrogen impinging on the laser surface is nitrogen ions accelerated by an electric field, for example a high frequency region or a microwave region. Nitrogen ions may be composed of nitrogen ions in the form of atoms or molecules, mixtures thereof. Nitrogen impinging on the laser surface may be a neutral nitrogen atom impinging on the surface with thermal energy.
    [104] The nitride layer may include one or more elements selected from the group consisting of AlN, GaN, InN, InAsN. Subsequently, the deposited and nitrided layers can be prepared in combination and subsequently annealed. The process can be performed on multiple GaAs-based lasers simultaneously before being separated from the wafer containing the GaAs-based lasers held together. Patterns formed by standard lithography processes can be provided on the wafer. The pattern preferably comprises a photo-resist material to prevent dry-etching in certain areas, such as ridges or mesa tops. Dry etching and nitriding may form one or more of the following structures with sub-micron resolution to form waveguide faces: mesas, ridges, trenches, corrugated periodic structures. Periodic structures can have sub-micron resolution, such as DFB and DBR structures. Photon band gap structure (PB) can be used as an alternative to DFB and DBR structures.
    [105] Additional nitride layers may be provided to fill the pinholes, planarize the surface and / or have higher thermal conductivity than GaAs and air to remove heat. Each dry laser chip by dry etching and nitriding is:
    [106] A second smooth surface inclined to a vertical cut in which each cut has a triangular shape with one face perpendicular to the wafer surface through the active area and is provided with a laser chip and a highly reflective layer for bending the laser beam emitted from the front layer. A first type of glove / trench beneath the wafer surface through the provided active region;
    [107] At a wafer front side including a second type of glove / trench below through the active region having a high reflective layer of about 95% reflectivity and having one or more faces perpendicular to the surface of the wafer and directed to the active region; Etched can be formed:
    [108] The present invention also provides
    [109] An active region having a quantum well between the first n-doped layer, the second p-doped layer and the first and second layers, each layer comprising a material selected from the group comprising GaAs, GaAlAs, InGaAsP and InGaAs To;
    [110] Laser channel in the active region;
    [111] A surface structure on the outer surface of the first layer forming the channel;
    [112] A natural nitride layer next to the outer surface of the first layer except on a predetermined location on the structure;
    [113] A GaAs laser comprising a protective layer on the outer surface of the natural layer and / or a mirror coating.
    [114] Further in-situ or ex-situ deposition nitride films may be provided over the natural nitride layer, the nitride films comprising one or more elements from groups 2b, 3a, 4a, and 5a such as Si, Ga, Zn, Al. . One more thin film or thin films may be provided over the thin nitride film of in-situ or ex-situ deposition. One or more additional membranes are provided to further reduce the interfacial surface recombination provided under the protective layer and / or the mirror coating. It comprises a crowd of structures including a DBR (Distributed Bragg Reflector), DFR (Distributed Feedback) and Photon Band Gap for forming a laser wavelength. DBR (Distributed Bragg Reflector) and DFR (Distributed Feedback) are one-dimensional in periodicity. Photon band gap (PBC) effects are provided by the use of two-dimensional photonic crystals (2D-PC) to provide a mirror (photonic crystalline mirror) for a given wavelength. Holes of triangular gratings may be provided in the two-dimensional structure of the semiconductor grating to periodically change the dielectric constant. The grating constant and hole-diameter can be adjusted for a given wavelength. The holes may be provided at periodic rates d in the range of about 150 to 400 nm in the material to form a wavelength-selective mirror for providing wavelength stabilized laser-light from the plane side of the laser. The cross section of the holes is a triangle with their base on the substrate surface, and the holes are preferably nitrided.
    [122] Referring to FIG. 1, in semiconductor laser fabrication, a wafer W of semiconductor diode is produced, each diode having an n-doped layer, a p-doped layer and an active region therebetween. For example, the n-doped layer may comprise n-doped GaAs and the p-doped layer may comprise p-doped GaAs. The active region should preferably be non-doped but may contain some doped species from the surrounding layer. Thus, it can be low-doped and include multiple thin layers.
    [123] The active region may contain an AlGaAs and / or InGaAs layer. As shown in FIGS. 1A and 1B, this wafer may be divided into several smaller wafer portions WP. Each wafer portion is scribed with a scribe line SL, where a cut must be made. As shown in FIG. 1C, the wafer portion WP must next be cut into bars B along the scribe line SL. The other side of the wafer is placed over the edge and broken at each scribed line. To make a laser chip for the bar, a mirror plane is provided at each end of the cut section of the bar. As shown in Fig. 1D, each bar is subsequently cut into chips CH. In the case of a pump laser, one of the mirror faces is high reflectivity (HR) coated and the other is non-reflective (AR) coated. The laser beam is emitted obliquely into the active region in the active region of each semiconductor diode chip through a non-reflective coated laser mirror. The manufacturing process briefly described above is conventional.
    [124] The present invention is directed to obtaining a nitride layer over any structure for a GaAs-based laser via dry etching, preferably made on a wafer or wafer portion just before being cut.
    [125] The laser wafer shown in the first embodiment of FIG. 2 comprises a p-doped layer 2, an n-doped layer 3, and an active layer 4 having a quantum well.
    [126] The contamination-free (GaAlAs-InGaAs) surface on layer 3 comprises a material selected from the group comprising GaAs, GaAlAs, InGaAs, InGaAsP and InGaAs. The nitride layer should be obtained on any structure for GaAs based lasers.
    [127] In the active layer 4 there is a ridge or mesa 6 in front of and parallel to the channel 5 with respect to the laser beam, whereby the channel is formed. Mesa is shown in FIG. Angled sloped surface surfaces 7 and 8, which may be arbitrary with respect to the horizontal plane by dry etching, are provided on the ridge or mesa. The ridge or mesa also has an upper surface 9, which is essentially parallel to the wafer surface.
    [128] The first surface treatment is cleaning. As a result, dry etching to the wafer surface is initiated in the vacuum chamber, for example by theoretical beam etching using a plasma of inert and / or reactive gases and mixtures thereof, such as nitrogen, hydrogen, argon, and chlorine gas. Adding a reactive gas or hydrocarbon gas (eg CH 4 and C 2 H 6 ), such as a halogen gas (eg Cl, Br, or I-based compound) to the dry etching step, may be followed by the next nitriding process It may help to ensure that the surface is well formed, smooth and stoichiometric after the step begins. This is because the reactive gas promotes the removal of Ga to prevent physical etching, ie preferential etching of As occurring under ion milling.
    [129] Thus, dry etching may include ion milling using an argon plasma at the start. This is a preferred embodiment because the argon plasma is effected effectively in the milling process and followed by nitrogen milling. Furthermore, the crystalline structure may also consist of the following elements: Se and Sb to have a surface free of contamination in the crystalline mirror plane.
    [130] Other examples of dry etching techniques that can be used for both dry etching and nitriding steps include parallel plate reactive ion etching (RIE), inductively coupled plasma reactive ion etching (ICP), electron cyclotron resonance plasma reactive ion etching (ECR), There is a barrel reactor and a downstream reactor. Other dry etching techniques that are well known to those skilled in the art (including those mentioned above) may also be used. Plasma excitation can be performed, for example, by supplying microwave power, high frequency power or DC power.
    [131] Hydrogen gas during ion milling to the laser side helps to reduce surface contamination and specifically oxidized areas in some way because hydrogen reacts with oxides to remove oxygen in the form of water. This process continues until a surface free of contamination is obtained. If an argon plasma is used for ion milling, nitrogen gas is added to the argon plasma to passivate the laser surface and gradually remove argon until only nitrogen plasma is provided in the same step. Thus, ion milling is completed by nitrogen milling to obtain an extremely smooth surface shape as the final plasma in the ion beam milling process.
    [132] After applying the deposition layer 10 to the wafer surface containing the natural nitride layer closest to the layer 3, the layer 11 of electrically conductive material, described below, is electrically connected to a controllable current source. To the upper surface 9 of the ridge 6 with bonded wires (not shown). The laser is pumped with regulation of the current source. Thus, no nitride layer 10 is provided on the top surface 9.
    [133] The invention is not limited to a gradual interface, although it is desirable. It can of course be insulated. Milling can then be provided by using only nitrogen (either ions or atoms) and possibly with the addition of hydrogen. However, an important feature is that a natural nitride layer 10 is provided after dry etching, and thus is not a nitride layer comprising other components besides that provided at the cut surface. Preferably, there is no interface between the other layers. The first natural nitrided layer may comprise GaN / InN / AlN / AlGaN / InAsN. Since the concentration of nitrogen entrained varies continuously for direct nitrogen ion milling and also into the crystals, nitriding without any actual adiabatic interfacial layer is also possible without any other dry etching prior to or without any other gas added to the nitrogen ion milling process. Can be obtained by performing nitrogen ion milling directly.
    [134] The natural nitride layer so formed on the surface during nitrogen assisted ion milling could be reinforced with one or more extra layers 13, 14 of deposited nitride, in particular to level surface barriers and possible pinholes in the first nitride film. These extra films or these extra films may include the same nitrides, but may also include nitrides other than natural ones, for example SiN, GaN and the like. Another extra film 15 may also be provided to remove heat by bringing higher thermal conduction than GaAs and air.
    [135] A method for obtaining very smooth surface morphology can be provided by using nitrogen as the final plasma in the ion-beam milling process. The use of nitrogen compared to argon in the plasma resulted in very smooth surfaces in other semiconductor materials such as GaAs and InP.
    [136] The protective layer 12 is provided over the deposition layers 10, 13, 14 and 15.
    [137] A mask is provided on the ridge top surface 9 before the nitride layer is performed.
    [138] Thus, in summary, the wafer is subjected to the following process steps:
    [139] 1. The wafer is placed in a vacuum between 10 Torr and 10 -11 Torr, preferably less than 10 -7 Torr.
    [140] 2. The wafer should have a pattern formed by standard lithography processes. The pattern may include a photo-resist material to prevent dry-etching in certain areas, such as over the ridges.
    [141] 3. Dry etching will be performed using chemically reactive and inert gases and mixtures containing them, in particular argon, nitrogen, hydrogen and chlorine.
    [142] 4. The smooth surface shape is enhanced to a specific energy range of 50 to 500 eV in combination with alternating beam incidence angles from 0 ° to 85 ° from the normal angle of incidence.
    [143] 5. Create the passivation nitride layer 10 using the extracted beam and using a plasma containing nitrogen. Nitrogen impinging on the laser surface may be nitrogen ions or neutralized nitrogen ion beams accelerated by an electric field (plus optical high frequency (RF) and microwave regions), and nitrogen atoms impinge on the surface with thermal energy.
    [144] 6. A nitride layer consisting of AlN, GaN, InN, InAsN and combinations thereof.
    [145] 7. Additional in situ or ex situ deposition of thin nitride films using reactive plasma in combination with materials such as Si, Ga, Zn and Al.
    [146] 8. Add one thin film or thin films 14 to further reduce interfacial surface recombination prior to providing the protective layer 12 and / or the mirror coating.
    [147] 9. All these deposition and nitriding steps can be carried out with or before the annealing process.
    [148] 10. Addition of protective layer 12 and / or mirror coating (in M6, M9 in FIG. 6).
    [149] Is done through.
    [150] Temperature control
    [151] It is possible to leave the temperature changed during and after nitriding. Suitable temperature ranges are between about -180 ° C and + 600 ° C. Because temperature is an important parameter for water vapor-pressure, etch-yield and the likelihood of incorporation of other materials, active temperature control by cooling and / or heating the sample during nitriding provides a better balance of III / V-quota of the surface. Can give Heat treatment after nitriding, so-called "annealing" and "rapid heat annealing" can almost completely treat possible defects. The temperature range can be here from +200 ° C to 600 ° C.
    [152] Ion-current density
    [153] Ion-current density indicates how many ions hit the GaAs-surface per unit time. Optimization of the surface structure can be achieved by changing the ion-current density as a function of time. A batch (total amount of ions per unit surface) is an integrated ion flow over time. By pulsing an ion-current, for example, it is possible to avoid local heating of the surface and thus obtain better nitriding, for example also stress-free. As an alternative, it is also possible to intentionally momentarily heat the surface intentionally using a strong flow with a longer duration to slow diffusion.
    [154] Thus, the beam is preferably moved at alternating beam incidence angles in order to etch mesa or ridge before and during coating with the deposition layer. In this way, much better results will be obtained than when the beam angle of incidence is vertical. The passivation nitride layer closest to layer 3 will be natural. The essential concept hidden in this aspect is that the formation of the nitride layer provides a layer that prevents chemical contamination (eg oxidation) and also reduces the higher band gap surface layer and / or interfacial carrier recombination rate.
    [155] Etching may be performed by any well known dry etching process, such as Ar / Cl 2 based chemical auxiliary ion beam etching (CAIBE), reactive ion beam etching (RIBE), or Ar to first form a ridge or mesa profile in the manner described above. It may also proceed with other types of etching, including ion milling. The steps then take place with the possibility of nitrogen ion milling and varying the angle of incidence and energy. Optionally, it is possible to mill directly with nitrogen ions and, depending on the profile obtained, to again mill at different angles and rotations relative to the wafer to complete the last etching step.
    [156] Additional nitride layers
    [157] (iv) filling the pinhole;
    [158] (v) flattening; And
    [159] (vi) It has higher thermal conductivity than GaAs and air and can be applied to remove heat.
    [160] These layers may be provided for all embodiments shown herein, although not shown. However, the extra layer or film mentioned above the nitride layer 10 need not always be present.
    [161] Face wall damage can occur with dry etching. This can be minimized using low energy processes. It is also possible to remove the damage created by the lowest energy ion milling, incorporate nitrogen, and at the same time remove the damaged layer in the previous ridge or mesa formation process.
    [162] In accordance with a second embodiment of the present invention, FIG. 3 shows a portion of a wafer having a ridge-structure 20 for each laser unit. The ridge-structure has trenches 21 and 22 on each side, for example to form waveguide 23 for the laser beam causing current interruption or for improved thermal conductivity. A deposition layer 24 is provided over the ridge-structure 20 and in the trenches 21, 22. Each beam incident and extracted to have a trench of the vertical plane dry-etched and coated with the deposition layer is moved at an alternate beam angle.
    [163] The wafer portion has a scribe line SL, which should be cut directly from here. 2 shows a wafer without a protective layer provided on the deposition layer in the same manner as in the embodiment shown.
    [164] There is a ridge forming a waveguide. Current limiting is used to provide a single crossing mode under the ridge or mesa. Trench also affects the mode and can provide a more stable single mode.
    [165] With reference to FIG. 4, a third embodiment is shown here. 4 shows the shear plane of FIG. 3 perpendicular to that shown in FIG. 2. A mesa or ridge profile 30 parallel to the laser channel in the active layer 31 is provided with a corrugated periodic structure having sub-micron resolution, for example distributed feedback (DFB) and distributed Bragg reflector (DBR) structures. . The sides are preferably evenly inclined in this embodiment.
    [166] The active layer 31 may include an alternate passive layer 31A having a high band gap quantum wall and an active layer 31B having a quantum wall for, for example, AlGaAs or InGaP, as in all embodiments shown.
    [167] At each end, which is the smooth portion 33, a band wire 34 connected to an adjustable current source is fixedly connected. A nitride layer 35 is provided at the straight end, perpendicular to the active layer 31. This distal end represents the front parsec of the laser. However, the rear end of the laser can be erected in the same way. Mirror layers may be provided inside or outside the nitride layer 35.
    [168] However, the profile of nitride layer 30 with corrugation does not necessarily need to be ridged, and corrugation can also be provided for the construction of a flat plate. In the structure of the plate, the active region 31 is sealed with a material having a low reflection index, which requires re-growth. The quaternary material InGaAsP is a suitable material for regrowth. This fourth embodiment is not shown as a separate drawing since such a drawing is not different from FIG.
    [169] The corrugated structure will preferably be located above the active layer 31 in both the third and fourth embodiments. The corrugated structure allows to provide a periodic refractive index change, which then determines the wavelength through resonant coupling. Thus, periodic corrugated structures are fabricated by in situ, natural nitriding by dry etching and the use of nitrogen in ion beams.
    [170] It is also possible for the laser part to have a corrugated structure that is passive, ie free of induced emission. The structure is called a distributed Bragg reflector (DBR). It does not matter whether the corrugated structure is provided only in the laser portion, above or below the active layer (not shown), or if the corrugation is etched in the active layer. The dry etching method according to the invention can be used to provide any of the corrugation structures mentioned above.
    [171] A fourth embodiment of the laser structure is shown in FIGS. 5A and 5B.
    [172] The so-called photon band gap structure can be used as a replacement for the DBR (distributed Bragg reflector) and DFB (distributed feedback) structures for forming the laser wavelength. Photon band gap (PBG) effects using two-dimensional photonic crystals (2D-PC) can be used to provide a mirror (photonic crystalline mirror-PC mirror) for a given wavelength. 2D-PC is a structure in which the dielectric constant changes periodically, for example by providing a deep hole 37A of triangular defects in a semiconductor host lattice (see FIG. 5B). The hole 37A is etched into the top surface of the laser wafer with periodicity d in the range of about 150-400 nm to the substrate to form the wavelength-selective mirror 37. This mirror 37 can reflect up to 100% for the selected wavelength. Thus, various wavelength-stable laser-lights can be obtained at the side 35 of the laser.
    [173] The laser channel 38 is of the same kind of grating provided with a hole 37A for the mirror 37, ie the first grating 39A provided on one side of the laser channel 38 and on the other side, i.e., in the horizontal direction. Formed by the second grating 39B in the array. The front mirror 36 having the same kind of lattice as the hole 37A as the rear mirror 37 is placed near the nitride layer 35.
    [174] Originally, the same etching process is used as for other embodiments of the laser structure. The difference is that another mask is used for the photon band-gap, for example for DFB- or DBR-structures. Photon band-gap has a two-dimensional structure, while DBR and DFB are one-dimensional in periodicity.
    [175] The depth of etching is about 600-1000 nm. In FIG. 5B the hole 37B is shown larger in the actual substrate. The cross section of the hole 37A is preferably a triangle with their base on the substrate surface for practical reasons as well. However, other forms such as rectangles and the like can also be envisioned. The hole 37 is nitrided 37B to prevent oxidation and penetration of other impurities into the active region 31. In addition, the space between the holes 37A is preferably nitrided (not shown).
    [176] PC mirrors 37 and 36 can be used to (a) form a lasing mode longitudinally by placing them at both ends of the laser cavity, where one end 37 has a high reflectivity and the other It has a low reflectance 36 and is either an output end or (b) one end 37 serves only as a reflector and the other end 36 is typically made of a laser output face (not shown). The reflectivity of the PC mirror depends on the amount of periodicity, and the larger the number of periods, the higher the reflectivity. The grating constant and hole-diameter are adjusted for a given wavelength so that this wavelength lies in the middle of the stop band of the PC mirror.
    [177] PC mirrors can also be used to define the horizontal length of the lasing mode. In this case, the two end-faces 37 and 36 may typically be faceted or provided to the PC mirror by a suitable design.
    [178] The PC mirror is formed in one step by a suitable dry etching process. This step follows the nitriding process and passivates the electrically chemically etched surface.
    [179] The laser is also calibrated to provide several desired features by drilling some extra holes in the wafer surface, for example closer to calibration values and the like.
    [180] Referring to FIG. 6, a fifth embodiment is described, wherein each entire laser chip is etched at the front of the wafer. The whole laser is centered. The laser portions are shown on their respective faces to show that they are provided one by one in the string at the wafer. It will also be appreciated that the wafer contains many such parallel laser strings in a direction perpendicular to the paper plane.
    [181] The laser wafer M1 with the p-doped laser M2, the active region M3 and the n-doped laser M4 has several globes M5. Each of them has a triangular form with one side M6 perpendicular to the wafer facing the active region M3 and one side M7 preferably at 45 ° to the vertical surface M6 to function as the front side of the laser chip. Have
    [182] The face M6 is the laser front face to the laser beam in the active region M3, dry etched and treated in the same manner as described above. Next, a non-reflective layer (AR-layer) or transparent dielectric by ZeSe or GaN is provided to serve as the front mirror of the laser from which the laser beam is emitted. Surface M7 represents an inclined mirror that redirects the laser beam LB perpendicular to the wafer surface. This face M7 therefore becomes particularly smooth and has a high reflective surface overlayer.
    [183] Many vertical gloves M8 are provided, each of which has one or more faces M9 directed to the active region M3 perpendicular to the wafer surface. This side serves as the back mirror side of the laser chip. Therefore, as described above, dry etching is performed in the same manner. Next, it has a high reflective layer, about 95% reflectivity.
    [184] It can be seen that passivation layer treatment for both front and back side mirrors can be provided simultaneously in this embodiment. The entire upward facing surface in FIG. 6 is thus treated in the same way as a mirror, so that the resulting overall surface is dry etched and the natural nitride layer is braked. However, in each laser bar a non-reflective layer of face M6 and a high reflective layer of face M9 are provided while shielding other portions of the wafer surface. The high reflection mirror M7 is also provided with its reflective layer while the remaining surface is shielded.
    [185] While the invention has been described with respect to exemplary embodiments, it is apparent that changes can be made without departing from the scope thereof. Therefore, the invention should not be limited to the described embodiments but should be formed by the following claims to cover all equivalents thereof.
    [186] The novel process according to the invention is based on ion milling using nitrogen as one important component. For example, the use of this method to form a laser waveguide structure has five advantages.
    [187] The surface will be much smoother than conventional wet and dry etching methods, minimizing the resulting scattering losses.
    [188] The nitrogen ion beam milling process can form a natural nitride layer that blocks any impurities from reacting with the active material.
    [189] The natural nitride layer will have a lower surface state density than the ex-situ deposited nitride layer, thereby minimizing the resulting recombination rate.
    [190] Improved phases can be etched like ridges, trenches, distributed feedback (DFB) and distributed Bragg reflectors (DBR) and faces.
    [191] Optical nitride layers (eg AlN, SiN, GaN, InN, InAsN) or any other layer that does not alter or damage the semiconductor surface can be deposited over the natural nitride layer for planarization and heat dissipation.
    权利要求:
    Claims (42)
    [1" claim-type="Currently amended] A method of using dry etching to obtain a contamination-free surface for a material selected from the group comprising GaAs, GaAlAs, InGaAsP, and InGaAs to obtain a nitride layer on any structure for a GaAs-based laser, the method comprising:
    Providing a mask on the laser surface that masks its surface portions to be protected from dry etching;
    Leaving the laser in the vacuum;
    Performing a dry etch using a material selected from the group containing a chemically reactive gas, an inert gas, a mixture between a chemically reactive gas and an inert gas;
    Generating a natural nitride layer (10; 24; 35) using a plasma containing nitrogen;
    Adding a protective layer (12) and / or a mirror coating (to M6, M9).
    [2" claim-type="Currently amended] The method of claim 1,
    Chemically inert and reactive compounds such as nitrogen, hydrogen, argon and halogen compounds (eg, Cl, Br, or I-based compounds) and hydrocarbon gases (eg, CH 4 and C 2 H 6 ) and mixtures thereof Initiating the dry etch using a material assisted plasma comprising one or more materials from the group comprising a gas
    Passivating the face after obtaining a surface free of contamination using a nitrogen assisted plasma.
    [3" claim-type="Currently amended] The method of claim 1 or 2, wherein the dry etching is performed with a nitrogen assisted plasma.
    [4" claim-type="Currently amended] The method of claim 1 or 2, wherein the dry etching is performed with a plasma in which the material is a mixture of nitrogen and another gas, wherein the other gas is gradually replaced with nitrogen until only a nitrogen plasma is provided. How to.
    [5" claim-type="Currently amended] The method of claim 1 or 2, wherein the dry etching is performed with a gas free of nitrogen, wherein the gas is gradually replaced with nitrogen until only a nitrogen plasma is provided.
    [6" claim-type="Currently amended] 6. The method of claim 2, wherein the nitrogen plasma contains nitrogen ions, atomic nitrogen or molecular nitrogen or mixtures of two or more thereof. 7.
    [7" claim-type="Currently amended] 7. The method of any of claims 2-6, further comprising adding hydrogen to the material assisted plasma to enhance removal of oxides.
    [8" claim-type="Currently amended] 8. A method according to any one of claims 2 to 7, wherein said substance is argon.
    [9" claim-type="Currently amended] The method according to any one of claims 1 to 8,
    The nitride layer (10; 24) on the non-contaminated surface while introducing elements from the group comprising ionized nitrogen, atomic nitrogen, and molecular nitrogen into the material assisted plasma and reacting with the non-contaminated surface To start growing
    Progressively creating an interface between the unpolluted surfaces and the grown nitride layer using natural nitriding to minimize interfacial recombination between other layers.
    [10" claim-type="Currently amended] 10. The nitride layer (10) according to any one of claims 1 to 9, comprising at least one material selected from the group comprising AlN, GaN, InN, InAsN using a plasma comprising nitrogen with the extracted beam. 24) further comprising the step of generating the same.
    [11" claim-type="Currently amended] The natural nitride layer according to any one of claims 1 to 10, using a reactive plasma in combination with one or more elements from groups 2b, 3a, 4a, and 5a, such as Si, Ga, Zn, Al. Providing further in-situ or ex-situ deposition of the thin nitride film (13) thereon.
    [12" claim-type="Currently amended] 12. The method of claim 11, further comprising adding one or more additional films 14 to further reduce interfacial surface recombination prior to adding the protective layer 12 and / or mirror coating. Way.
    [13" claim-type="Currently amended] 12. The additional thin film or thin films of claim 11 after the in-situ or ex-situ deposition of the thin film to further reduce interfacial surface recombination prior to providing the protective layer 12 and / or mirror coating. Adding (14).
    [14" claim-type="Currently amended] 14. Process according to any of the preceding claims, characterized in that the vacuum is between 10 Torr and 10 -11 Torr, preferably less than 10 -7 Torr.
    [15" claim-type="Currently amended] The method of claim 1, wherein the gas for performing dry etching is selected from one or more elements from the group containing argon, nitrogen, hydrogen and chlorine.
    [16" claim-type="Currently amended] 16. The method according to any one of claims 1 to 15, in combination with alternating beam incidence angles from 0 ° to 90 ° from the normal angle of incidence, and with respect to temperature and current density as a function of time in a specific energy range of 0 to 2000 eV. Improving the smooth surface shape during the dry etching.
    [17" claim-type="Currently amended] The method according to any one of claims 1 to 15, in combination with alternating beam incidence angles from 0 ° to 85 ° from the normal angle of incidence, and with respect to temperature and current density as a function of time, in a specific energy range of 50 to 500 eV. Improving the smooth surface shape during the dry etching.
    [18" claim-type="Currently amended] 18. The method of any one of claims 1 to 17, wherein the plasma containing nitrogen impinging on the laser surface is nitrogen ions accelerated by an electric field.
    [19" claim-type="Currently amended] 19. The method of claim 18, wherein the nitrogen ions consist of nitrogen ions in the form of atoms or molecules, or mixtures thereof.
    [20" claim-type="Currently amended] 20. The method of claim 18 or 19, wherein the electric field is a high frequency region or a microwave region.
    [21" claim-type="Currently amended] 18. The method according to any one of claims 1 to 17, wherein the plasma containing nitrogen impinging on the laser surface is a neutral nitrogen atom impinging on the surface with thermal energy.
    [22" claim-type="Currently amended] 22. The method of any one of claims 1 to 21, wherein the nitride layer comprises one or more elements selected from the group consisting of AlN, GaN, InN, InAsN.
    [23" claim-type="Currently amended] 23. The method of any one of claims 1 to 22, further comprising the step of fabricating and subsequently annealing the deposited and nitrided layers.
    [24" claim-type="Currently amended] 24. The method of any one of claims 1 to 23, comprising performing the process on a plurality of GaAs based lasers simultaneously before being separated from the wafer containing the GaAs based lasers held together.
    [25" claim-type="Currently amended] 25. The method of claim 24, comprising providing a pattern formed by a standard lithography process on the wafer.
    [26" claim-type="Currently amended] 27. The method of claim 25, wherein the pattern comprises a photo-resist material to prevent dry etching in certain areas, such as ridges or mesa tops.
    [27" claim-type="Currently amended] 27. The structure according to any one of claims 1 to 26, having the following sub-micron resolution for forming the waveguide face: mesa 9, ridge 20, trenches 21, 22, 24, corrugation And forming one or more of the cyclic periodic structures (30) and photon band-gap structures (37) by said dry etching and nitriding.
    [28" claim-type="Currently amended] 28. The method of claim 27, wherein the periodic structure has sub-micron resolution, such as DFB, DBR, and photon band-gap structures.
    [29" claim-type="Currently amended] 29. Method according to one of the preceding claims, characterized in that it comprises an additional nitride layer (13; 37A) for filling the holes and / or pinholes.
    [30" claim-type="Currently amended] 30. A method according to claims 1 to 29, comprising an additional nitride layer (14) to planarize the surface.
    [31" claim-type="Currently amended] 31. The method according to any one of the preceding claims, characterized in that it comprises an additional nitride layer (15) to remove heat by having higher thermal conductivity than GaAs and air.
    [32" claim-type="Currently amended] The method of claim 27,
    Each of the cuts has a triangular shape with one face perpendicular to the wafer surface through the active area and is inclined to a vertical cut with a laser chip and a highly reflective layer for bending the laser beam emitted from the front layer. A first type of glove / trench M5 below the wafer surface through active region M3, provided with two smooth sides M7;
    A second type of glove / trench below through the active region M3 having a high reflective layer of about 95% reflectivity and having one or more faces perpendicular to the surface of the wafer and directed to the active region, Forming each entire laser chip etched from the front side of a wafer by said dry etching and nitriding.
    [33" claim-type="Currently amended] An active region (4; 31) having a first n-doped layer (3), a second p-doped layer (2) and a quantum well between said first and second layers, each layer comprising GaAs, GaAlAs, A material selected from the group comprising InGaAsP and InGaAs;
    A laser channel 5 in the active region 4; 31;
    A surface structure (6; 38) on the outer surface of the first layer forming the channel;
    A natural nitride layer (10; 30A; 37A) next to the outer surface of the first layer except above a predetermined position (9) on the structure;
    A GaAs laser comprising a protective layer 12 and / or a mirror coating (at M6, M7; at M9) on the outer surface of the natural layer.
    [34" claim-type="Currently amended] 34. The method of claim 33, further comprising an additional in situ or ex situ thin nitride film 13 on the natural nitride layer 10, wherein the nitride film is 2b, 3a, such as Si, Ga, Zn, Al. And at least one element from group 4a, and group 5a.
    [35" claim-type="Currently amended] 35. The GaAs-based laser of claim 34, further comprising an additional thin film or thin films (14) on the thin nitride film of the in-situ or x-situ deposition.
    [36" claim-type="Currently amended] 36. The apparatus of any one of claims 33 to 35, further comprising one or more additional thin films 15 to further reduce interfacial surface recombination provided under the protective layer 12 and / or mirror coating. GaAs laser.
    [37" claim-type="Currently amended] 37. The apparatus of any of claims 33 to 36, comprising a crowd of structures comprising a distributed Bragg reflector (DBR), a distributed feedback (DFR) and a photon band gap to form a laser wavelength. GaAs laser.
    [38" claim-type="Currently amended] 38. The GaAs laser according to claim 37, wherein the DBR (distributed Bragg reflector) and DFR (distribution feedback type) are one-dimensional in periodicity.
    [39" claim-type="Currently amended] 38. The GaAs system of claim 37, wherein the photon band gap (PBC) effect is provided by using two-dimensional photonic crystals (2D-PC) to provide a mirror (photonic crystalline mirror) for a given wavelength. laser.
    [40" claim-type="Currently amended] 40. The semiconductor device of claim 39, further comprising holes for the triangular lattice 37 in the two-dimensional structure of the semiconductor lattice to periodically change the dielectric constant; And
    GaAs-based laser, characterized in that the lattice constant and hole-diameter are adjusted for a given wavelength.
    [41" claim-type="Currently amended] 41. The method of claim 40, wherein the hole 37 is provided at a periodic rate d in the range of about 150 to 400 nm in the material to form a wavelength-selective mirror for providing wavelength stabilized laser-light from the side of the laser. GaAs laser.
    [42" claim-type="Currently amended] 42. The GaAs laser according to any one of claims 39 to 41, wherein the cross section of the holes (37) is a triangle having their base on the substrate surface, and the holes are nitrided (37A).
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    同族专利:
    公开号 | 公开日
    US20030032297A1|2003-02-13|
    WO2003015185A1|2003-02-20|
    EP1421631A1|2004-05-26|
    US6803605B2|2004-10-12|
    RU2004106535A|2005-03-27|
    JP2004538651A|2004-12-24|
    CA2456142A1|2003-02-20|
    US20030047739A1|2003-03-13|
    CN1541419A|2004-10-27|
    US6734111B2|2004-05-11|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2001-08-09|Priority to US09/924,448
    2001-08-09|Priority to US09/924,448
    2002-08-09|Application filed by 컴라세 에이비
    2002-08-09|Priority to PCT/SE2002/001444
    2004-04-29|Publication of KR20040035729A
    优先权:
    申请号 | 申请日 | 专利标题
    US09/924,448|US6734111B2|2001-08-09|2001-08-09|Method to GaAs based lasers and a GaAs based laser|
    US09/924,448|2001-08-09|
    PCT/SE2002/001444|WO2003015185A1|2001-08-09|2002-08-09|A method to gaas based lasers and a gaas based laser|
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