• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    In a semi-insulated bulk single crystal of silicon carbide, having a resistivity of at least 5000 Ω-cm at room temperature and a concentration of trapping elements that create at least 700 meV from a valence or conduction band. The valence band or conduction band is lower than the amount affecting the resistivity of the single crystal, and preferably lower than the detectable level. The method of forming such a single crystal is also disclosed with some of the resulting devices that take advantage of the microwave frequency capability of the device formed using the substrate according to the invention.
    公开号:KR20040012861A
    申请号:KR10-2003-7015400
    申请日:2002-05-23
    公开日:2004-02-11
    发明作者:카터칼빈에이취.주니어；브래디마크；츠베르코브발레리에프.；뮤엘러스테판；홉굳허드슨엠.
    申请人:크리 인코포레이티드；
    IPC主号:
    专利说明:

    Semi-insulating silicon carbide without vanadium {SEMI-INSULATING SILICON CARBIDE WITHOUT VANADIUM DOMINATION}
    [2] The term “microwave” refers to electromagnetic energy at a frequency that covers a range from about 0.1 gigahertz (GHz) to 1,000 GHz with a corresponding wavelength from about 300 centimeters to about 0.3 millimeters. While “microwaves” are perhaps most widely associated with the general public as cooking devices, those skilled in electronic devices include a variety of communication devices for various electronic purposes, and corresponding electronic devices and associated circuit elements and circuits for operating such electronic devices. It is recognized that microwave frequencies are used in. As in the case of many other semiconductor electronics and the resulting circuits, the ability of a device (or circuit) to clearly display its desired or required performance characteristics is wide, and often depends on the material often produced overall. Suitable candidate materials for microwave devices include silicon carbide, which provides a major advantage for microwave applications in the field of very high electrical breakdown. The silicon carbide feature allows devices such as metal semiconductor field effect transistors (MESFETs) to operate at drain voltages 10 times higher than field effect transistors formed in gallium arsenide (GaAs).
    [3] Additionally, silicon carbide has a significant advantage at 4.9 watts of thermal conductivity (W / K-cm) per absolute temperature centimeter, which is 3.3 times higher than silicon and 10 times higher than previous gallium arsenide or sapphire. This property provides high power density for silicon carbide with respect to the gate periphery measured in watts per millimeter (W / mm) and extremely high power handling capability with respect to die area (W / mm). This is particularly advantageous for high power, high frequency applications because die size is limited by wavelength. Thus, due to the excellent thermal and electronic properties of silicon carbide, silicon carbide MESFETs are capable of at least five times the power of devices made from gallium arsenide at any given frequency.
    [4] As will be appreciated by those skilled in the microwave device, the device requires a high resistivity (semi-insulated) substrate to achieve its purpose, since conductive substrates tend to cause significant problems at microwave frequencies. to be. As used herein, the terms "high resistivity" and "semi-insulation" may be considered synonymous for most purposes. In general, both terms describe a semiconductor material having a resistivity greater than about 1500 Ohm-cm.
    [5] Such microwave devices are particularly important for monolithic microwave integrated circuits (MMICs), which are generally widely used in communication devices such as pagers and cellular phones and generally require high resistivity substrates. Therefore, the following characteristics are desired for a microwave device substrate. High crystalline quality, good thermal conductivity, good electrical insulation between devices and substrates, low resistance loss characteristics, low crosstalk characteristics, and large wafer diameters, suitable for very complex and high performance circuit elements.
    [6] Wide bandgaps (3.2 eV in 4H silicon carbide at 300K) of a given silicon carbide, such as semi-insulating properties, are theoretically possible. As a result, a suitable high resistivity silicon carbide substrate can increase its efficiency and performance while reducing the size of power and passive devices installed on the same integrated circuit ("chip"). Silicon carbide also provides other favorable qualities, including the ability to operate at high temperatures without physical, chemical, or electrical breakdown.
    [7] However, as recognized by those skilled in silicon carbide, silicon carbide grown by most technologies is generally too conductive to achieve this goal. In particular, normal or unintentional nitrogen concentrations in silicon carbide tend to be high enough to provide sufficient conductivity in sublimation growth crystals (1-2 x 10 17 cm -3 ), making such silicon carbide unusable in microwave devices. do.
    [8] In order to be specifically used, silicon carbide devices must have a substrate resistivity of at least 1500 Ohm-cm (mm-cm) to achieve RF passive action. In addition, 5000 μm-cm or better resistivity is required to minimize device transmission line loss to an acceptable level of less than 0.1 dB / cm. Current work argues that the semi-insulating action of silicon carbide substrates is the result of energy level depth within the silicon carbide bandgap, i.e., the valence and conduction bands are farther away than the energy levels produced by p-type and n-type dopants. And US Patent No. 5,611,955, for example. According to the '955 patent, the depth level in the silicon carbide between the valence and conduction bands can be produced by a selected element of the transition metal or a controlled introduction of a passivating element such as hydrogen, chlorine or fluorine or the silicon carbide To form a deep level center in silicon carbide, see, for example, column 3, lines 37-53. In addition, in June 1998 by Mitchel, The 1.1 eV Deep Level in 4H-SiC, Berkley CA; Hobgood, Semi-Insulating GH-SiC Grown by Physical Vapor Transport, Appl. Phys. Lett. Vol. 66, No. 11 (1995); WO 95/04171; Sriram, RF Performance of SiC MESFETs on High Resistivity Substrates, IEEE Electron Device Letters, Vol. 15, No. 11 (1994); Schneider, Infrared Spectra and Electron spin Resonance of Vanadium Deep Level Impurities in Silicon Carbide, Appl. Phys. Lett. 56 (12) (1990); And Allen, Frequency and Power Performance of Microwave SiC FET's, Proceedings of International Conference on Silicon Carbide and Related Materials 1995, Institute of Physics.
    [9] In addition to conventional concepts, such deep level elemental impurities (also known as deep level trapping elements) can be incorporated by introducing during high temperature sublimation growth or chemical vapor deposition (CVD) growth of high purity silicon carbide. In particular, vanadium is considered to be a transition metal suitable for this purpose. According to the 955 'patent and the prior art, vanadium compensates for silicon carbide material and produces the high resistivity (ie, semi-insulating) properties of silicon carbide.
    [10] However, the introduction of vanadium as a compensating element for producing semi-insulating silicon carbide inevitably introduces disadvantages. First, the presence of any electronically significant amount of dopant, including vanadium, can negatively affect the crystal quality of the resulting material. Thus, to the extent that vanadium or other elements can be significantly reduced or eliminated, the crystal quality and the corresponding electronic quality of the resulting material can be improved. In particular, the amount of vanadium compensation can cause growth defects such as inclusion and micropipes in silicon carbide.
    [11] A second disadvantage is that the introduction of vanadium compensation amounts can reduce yields and incur additional costs in the production of semi-insulating silicon carbide substrates. Third, the proactive compensation of silicon carbide or any other semiconductor element is somewhat complicated and unpredictable and thus complicated to manufacture, which should preferably be avoided if compensation can be avoided. do.
    [12] In patent application 09 / 313,802, filed May 18, 1999 and serial 09 / 757,950, filed January 10, 2001, an improved semi-insulating silicon carbide is disclosed, including vanadium The concentration of is maintained below the detectable (eg, SIMS-detectable) level in the compensating silicon carbide single crystal. In describing related dopings, along with many prior art, the 802 'application sometimes refers to a particular dopant as "deep" or "shallow". The term "deep" or "shallow" may have exemplary values in describing situations and energy levels associated with a given dopant, which are to be understood as relative rather than limiting concepts.
    [13] For example, in some situations, level 300 meV or more from the band edge is referred to as "deep." However, any elements that generate levels in that range (eg, boron) can also operate as "shallow", ie those elements can produce conductive levels rather than levels that increase resistivity. In addition, as in the case of boron (B), individual elements can produce more than one level in the bandgap.
    [1] The present invention is a partial continuation of 09 / 757,950, filed Jan. 10, 2001, which is also a continuation of 09 / 313,802, filed May 18, 1999, which is now US Patent No. 6,218,680. Patented. FIELD OF THE INVENTION The present invention relates to the growth of high quality silicon carbide crystals for special purposes, and in particular to the production of high quality semi-insulating silicon carbide substrates useful in microwave devices. The invention was made in the department of Air Force Agreement No. F335615-95-C-5426. The government may specify certain rights in the invention.
    [19] 1 to 3 are plots for Hall effect measurements performed on a wafer made in accordance with the present invention.
    [20] 4 is a plot of natural log versus carrier concentration versus reversible temperature (Kelvin temperature) for semi-insulated silicon carbide according to the present invention.
    [21] 5 is a plot of natural log versus resistivity versus reversible temperature for semi-insulated silicon carbide according to the present invention.
    [22] 6-8 are plots of natural logs taken from other portions of the substrate wafer but at the same temperatures as in FIGS.
    [23] FIG. 9 is another plot of natural logs versus carrier concentration versus reversible temperature for the samples shown in the natural logs of FIGS. 6-8.
    [24] 10 is another plot of natural log versus resistivity versus reversible temperature corresponding to the sample measurements of FIGS. 6-8.
    [25] 11-13 are another set of plots performed in the same manner as FIGS. 1-3 and 6-8 for another measurement performed on another portion of the semiconducting silicon carbide material.
    [26] FIG. 14 is another plot of natural log versus resistivity versus reversible temperature for the samples shown in FIGS. 11-13.
    [27] 15, 16 and 17 are plots of secondary ion mass spectrometry for various sample materials in accordance with the present invention and the prior art.
    [14] It is therefore an object of the present invention to provide a semi-insulating silicon carbide substrate that is not generally characterized as a particular dopant, such as "deep" or "shallow", while also providing advantages for the required performance and high frequency operation. It is to provide a semi-insulating silicon carbide substrate that avoids the disadvantages in materials and techniques.
    [15] The present invention conforms to the above object, a semi-insulated bulk single crystal of silicon carbide having a resistivity of at least 5000 kV-cm and a concentration of transition metal less than 1E16 at room temperature.
    [16] In another aspect, the invention provides a half of silicon carbide having a concentration of trapping elements that produces a state of at least 700 meV from a valence band or conduction band that is less than an amount affecting the resistivity of at least 5000 ohm-cm and the electrical properties of a single crystal at room temperature Insulated bulk single crystal.
    [17] In another aspect, the present invention includes a device for incorporating semi-insulating silicon carbide according to the present invention, including a MESFET, certain MOSFETs, and High Electron Mobility Transistors (HEMT).
    [18] The above objects, other objects and advantages of the present invention, and methods of achieving the same will become more apparent based on the following detailed description with reference to the accompanying drawings.
    [28] In a first embodiment, the present invention is a semi-insulated bulk single crystal of silicon carbide having a concentration of transition elements, the concentration of such a element being lower than the level that governs the resistivity of the single crystal and preferably in cubic centimeters (cm -3). Concentrations less than 10-16 , ie less than 1E16.
    [29] In another embodiment, the present invention has a resistivity of at least 5000 ohm-cm at room temperature and a concentration of trapping elements that creates a state of at least 700 meV from a valence band or conduction band, The semi-insulated bulk single crystal of silicon carbide, the valence band or conduction band is lower than the amount affecting the electrical properties of the single crystal.
    [30] As used herein, the term “transition element”, when coupled to silicon carbide as a dopant, at the level between the valence and conduction bands of silicon carbide, is used in conduction and consumer electronics than conventional p-type or n-type dopants. Refers to an element from the periodic table that forms a state far from both sides of the magnetic field. As mentioned in the art and in the background, vanadium is a common transition element having this property.
    [31] As further used herein, a concentration defined as "below a detectable level" refers to an element provided in an amount not detectable by modern complex analytical techniques. In particular, since one of the more common techniques for detecting small amounts of elements is secondary ion mass spectrometry ("SIMS"), the detectable limits mentioned herein are based on the amount of elements such as vanadium and the amount of 1 x 10 16 cm -3. The amount of elements, such as other transition metals, provided in an amount less than (1E16), in other cases less than about 1E14. These two quantities exceed the detection limits common to most trace elements (particularly vanadium) using SIMS techniques, such as SIMS theory-sensitivity and detection limits, Charles Evans and Associates (1995), www.cea.com. Indicates.
    [32] As mentioned above, vanadium (V) is one of the more common elements that produce semi-insulating silicon carbide. Thus, the present invention is characterized in that in the absence or presence of vanadium, it is provided in an amount lower than an amount substantially affecting the resistivity of the single crystal, preferably in an amount lower than 1E16.
    [33] Although other polytypes (ie crystal structures) are possible, the silicon carbide single crystal according to this embodiment of the present invention preferably has a polytype selected from the group consisting of 3C, 4H, 6H and 15R polytypes.
    [34] In addition, in order to avoid the problems associated with the provision of nitrogen and the resulting need to attempt to compensate for the nitrogen, the silicon carbide single crystal according to this embodiment of the present invention preferably has a concentration of nitrogen atoms of about 1 x 10 17. less than cm −3 (1E17). More preferably, in the silicon carbide semi-insulated single crystal according to the present invention, the concentration of nitrogen is 5E16 or less. The concentration of vanadium is less than 1E16 atoms per cubic centimeter, most preferably less than 1E14 atoms per cubic centimeter. In addition, the resulting bulk silicon carbide single crystal has a resistivity of at least 10,000 kPa-cm at room temperature and most preferably a resistivity of at least 50,000 kPa-cm at room temperature.
    [35] For the purpose of providing a semi-insulating silicon carbide substrate in a high frequency MESFET, the 4H polytype with high bulk electron mobility is preferred. For other devices, other polytypes may be preferred. Thus, one of the more preferred embodiments of the present invention is a semi-insulated bulk single crystal of 4H silicon carbide, having a resistivity of at least 10,000 mW-cm and a vanadium atom concentration of less than 1E14 at room temperature.
    [36] Preferably, the method of producing a semi-insulated bulk single crystal of silicon carbide is adapted to sublimate the silicon carbide source powder while heating and maintaining the silicon carbide seed crystal at a temperature lower than the temperature of the silicon carbide source powder. When heated, at temperatures lower than the temperature of the source powder, sublimed species from the source powder condense on the seed crystals. The method then continues to heat the silicon carbide source powder until the desired amount of single crystal bulk growth is on the seed crystals. The method comprises (1) the amount of transition elements in the source powder (as described above) is less than the relevant amount, (2) the source powder contains 5E16 or less nitrogen, and (3) during sublimation growth, The source powder and the seed crystals are at a temperature high enough to significantly reduce the amount of nitrogen since the amount of nitrogen is incorporated into the bulk growth on the seed crystals unless the amount of nitrogen is significantly reduced. And maintained at a temperature that increases the number of point defects (often referred to as intrinsic point defects) in the bulk growth on the seed crystals to an amount that results in the resulting silicon carbide being in a bulk single crystal semi-insulated state. Preferably and conceptually, by keeping the amount of nitrogen or other dopant as low as possible, the number of point defects required to produce semi-insulated crystals can be minimized. As mentioned above, typically the detectable level is characterized according to the level which can be measured using SIMS. In other words, the amount of vanadium in the source powder is preferably less than 1E16 atoms per cubic centimeter, and most preferably less than 1E14 atoms per cubic centimeter.
    [37] In a preferred embodiment, the use of high priority graphite as one of the starting materials for SiC and the use of purified graphite parts within the reactor itself minimizes nitrogen. Generally, graphite (for source powder or reactor parts) is heated in a halogen gas state and, if necessary, further heated in an inert atmosphere (eg, Ar) at about 2500 ° C., to potentially doping elements such as boron or aluminum. Can be purified. Suitable purification techniques are known in the art (eg, US Pat. Nos. 5,336,520, 5,505,929 and 5,705,139) and can be performed as needed without undue experimentation.
    [38] According to the present invention, the amount of nitrogen in the resulting bulk single crystals uses the high purity technique mentioned in the prior art (which may be acceptable to some extent as part of the original technique), as well as relative It was further found that it can be reduced by performing sublimation at high temperatures, and by performing any bulk growth on the seed crystals at a temperature lower than the temperature of the source powder while maintaining the temperature of the seed crystals. Good techniques for sublimation growth (not modified as described herein) are disclosed in US Pat. No. 34,861, the content of which is incorporated herein by reference ("'861 patent").
    [39] Sublimation is carried out in a suitable crucible, typically formed of graphite, as disclosed in the '861 patent. The crucible includes a seed holder, all of which are located inside the sublimation furnace. The SiC source powder is selected and purified as needed so that the nitrogen concentration is below about 1E17 and preferably below about 5E16. In addition, the source powder has a concentration of vanadium, or other heavy metal or transition element, which concentration is lower than the amount that will affect the electrical properties of the resulting crystal. Such amounts include those below the SIMS-detectable level, with the use of SIMS currently available, such amounts are at least less than 1E16 atoms per cubic centimeter and preferably less than 1E14 atoms. Sauce powders also preferably meet other beneficial properties disclosed in the '861 patent.
    [40] When a small amount of boron is added as an acceptor, it is best added in the form of a source material (powder) containing the desired amount.
    [41] In practical terms, silicon carbide sublimation can be performed in a source temperature range of about 2360 ° C. to about 2500 ° C., and the temperature of the seed crystals is kept proportionally low. For the materials described herein, the source was maintained between about 2360 ° C and 2380 ° C and the seed crystals were kept low at 300-350 ° C. As is known to those skilled in the art of such procedures and measurements, the temperatures indicated may depend on how and where the system is measured and may vary slightly from system to system.
    [42] Since vanadium is the element of choice in conventional attempts to produce compensated semi-insulating silicon carbide, the present invention can be expressed as a bulk SiC single crystal, in which the method of making vanadium is more than the detectable and numerical levels mentioned above low. However, those skilled in the art of silicon carbide growth and silicon carbide properties as used for semiconductor purposes may likewise consider in the present invention the absence of any other element that leads to the same functional properties (and potential advantages) as vanadium. Of course it is.
    [43] By avoiding the use of such elements, the present invention likewise eliminates the need to compensate such elements with other elements, thereby reducing the complexity of introducing such compensation into the crystal growth process.
    [44] 1 through 17 illustrate various measurements performed on a semi-insulated substrate according to the present invention, with some comparisons with many conventional compensated and non-compensated silicon carbide materials.
    [45] 1-3 illustrate corresponding series of measurements performed on a substrate wafer grown at Cree Research Incorporated, North Hams, according to the present invention. As disclosed herein in the "experimental" section, the properties of these materials were tested at Air Force Research Laboratories, Dayton, Ohio. 1 shows carrier concentration versus reversible temperature for a semi-insulated substrate wafer according to the present invention (concentration being a logarithmic calculator). The slope of the resulting line represents an activation energy of approximately 1.1 electron volts (eV).
    [46] Figure 2 shows that the resistivity increases with decreasing temperature in a manner consistent with other anticipated properties of the semi-insulating material according to the invention.
    [47] 3 shows the mobility with respect to absolute temperature. FIG. 4 shows the natural log (ln) versus reversible temperature (absolute temperature) versus carrier concentration. As known to those skilled in the art, the slope of the natural logarithm to carrier concentration versus reversible temperature represents the activation energy. As indicated in the insertion box of Figure 4, the active energy of such a sample according to the invention is on the order of 1.1 eV, which is in agreement with the results of Figure 1. In comparison, as is known to those skilled in the art familiar with semi-insulating silicon carbide When vanadium is used as a deep level trapping element, the activation energy for semi-insulating silicon carbide is about 1.6 eV under the same circumstances.
    [48] Data was measured over a temperature range of about 569 K to about 1,012 K under a magnetic field of 4 kilologs on a sample thickness of 0.045 centimeters.
    [49] 5 shows the natural log of the reversible temperature versus resistivity of absolute temperature. Similarly, these data and these plots can be used to determine the active energy of the semi-insulating silicon carbide material. The value of 1.05667 eV determined from this plot can confirm the active energy of 1.1 eV previously measured. In other words, the difference in activation energy as measured in FIGS. 4 and 5 is within the expected experimental range and the data confirm with each other.
    [50] 6-10 show the same type of measurements and plots as done in FIGS. 1-5, but the samples are different. Specifically, the area is the same as the wafer measured in FIGS. 1 to 5 but different. Thus, Figures 6-8 are consistent with the results shown in Figures 1-3. More specifically, FIG. 9, another plot of natural log versus carrier concentration versus reversible temperature, shows the calculated activation energy of 1.00227 eV. Again, this value is within the experimental limit of 1.1 eV previously measured.
    [51] In a similar manner, FIG. 10 shows the natural log versus resistivity versus reversible temperature and similarly provides an active energy of 1.01159, which is likewise within the experimental limit of 1.1 eV. Figures 11-13 show the results obtained from another part of the wafer, which part of the wafer is considered to be less good than the results seen in the previous measurements. In particular, the plot of FIG. 11 does not form a straight line in the desired manner, and the data is less good than that shown in the previous results. Similarly, FIG. 14, which shows the natural log versus resistivity versus reversible temperature, shows a calculated active energy of only 0.63299, which is very far from 1.1 eV, irrespective of the uncertainty of the experiment.
    [52] 15, 16, and 17 show secondary ion mass spectra (SIMS) for various comparative samples and tend to show impurities and other materials of elements in semi-insulating silicon carbide substrates. 15 is a SIMS spectrum of a semi-insulating silicon carbide material in accordance with the present invention and can confirm the presence of vanadium or any other transition metal in the sample. This confirms that the activation energy and the mid-gap state provided by the present invention do not result from the presence of vanadium or other transition metals.
    [53] FIG. 16 is a SIMS spectrum of silicon carbide of an N-type wafer included for comparison purposes and not semi-insulated and not made in accordance with the present invention, but instead represents a conductive silicon carbide sample. Vanadium is not present in the mass spectrum because there is no reason to include vanadium for N-type substrates.
    [54] FIG. 17 provides a comparison of previous versions for semi-insulated silicon carbide compensated with vanadium. Vanadium peaks are strongly provided in about 51 atomic mass units in the spectrum. This vanadium peak is certainly not present in both FIGS. 15 and 16.
    [55] Of course, while the phrase “less than detectable amount” is a generally appropriate description in the present invention, it is understood by those skilled in the art that this amount is also lower than the amount that affects the electronic properties of silicon carbide crystals, especially the resistivity. Of course.
    [56] Thus, according to another aspect, the present invention includes a donor dopant, an acceptor dopant, and a semi-insulating silicon carbide single crystal having intrinsic point defects. According to this aspect of the invention, the number of donor dopants in the silicon carbide crystal (N d ) is greater than the number of acceptor dopants (N a ) and the number of intrinsic point defects in the silicon carbide (N dl ) functioning as an acceptor ) Is greater than the numerical difference between these donor and acceptor dopants. In addition to this point of view, the concentrations of transition elements and heavy metals are lower than those affecting the electrical properties of silicon carbide single crystals and preferably lower than 1E16. The resulting silicon carbide single crystal has a resistivity of at least 5000 m 3 -cm at room temperature and preferably at least 10,000 m 3 -cm, most preferably at least 50,000 m 3 -cm.
    [57] This aspect of the invention also applies to auxiliary situations where the number of acceptor dopant atoms is greater than the number of donor dopant atoms. In such a case, the number of inherent caking charges serving as donors is larger than the numerical difference between the number of donor impurities and the number of acceptor impurities.
    [58] In other words, shallow n-type and p-type dopants compensate for each other using n-type or p-type predominant in a predetermined range. The number of intrinsic point defects in an electrically activated crystal is greater than the pure amount of n-type or p-type dopant atoms that dominates others in the crystal. It can be written as the following formula.
    [59] N dl ＞ (N d -N a )
    [60] The donor here is superior to the acceptor.
    [61] or
    [62] N dl ＞ (N d -N a )
    [63] The acceptor here is superior to the donor. In the first case, the crystal can be compensated with dopant atoms based on the n-type. However, such pure donors are compensated again by acceptor type caking to produce semi-insulated crystals. In the second case, point defects function as donor types and compensate for pure excess acceptors in the crystal.
    [64] As used herein, the term “dopant” is used in a broad sense, ie to describe atoms other than silicon (Si) or carbon (C) present in the crystal lattice or to provide extra electrons (donors) or Used as a term to provide extra holes (acceptors). According to the invention, the dopant may be provided either manually or in advance, ie the term "dopant" means neither a "doping" step nor an absence of doping.
    [65] In a preferred embodiment, the acceptor is boron. In this embodiment, boron over-compensates nitrogen and point defects function as donors for overcompensating boron to produce semi-insulating silicon carbide crystals. The action of boron as an acceptor is in contrast to previous concepts that were considered as deep trapping elements (eg, column 8 lines 49-51 of commonly assigned US Pat. No. 5,270,554). Indeed, boron can produce trapping levels in SiC at 700 eV, but not in time. Thus, in the present invention, boron has been found to be a suitable acceptor dopant of semi-insulating silicon carbide of the type described herein.
    [66] In this preferred embodiment, silicon carbide is grown under conditions that reduce the active nitrogen concentration to a point where a relatively small amount of boron, preferably about 1E15 boron, forms a p-type crystal. By controlling the growth conditions, it is possible to overcompensate boron and produce semi-insulated crystals by setting the point defect concentration to about 5E15. By reducing the concentration of nitrogen and the corresponding boron compensation amount, the present invention avoids the aforementioned disadvantages of transition-metal dominance and high doping and compensation. Because crystal growth of SIC is a relatively complex process, the exact parameters may vary depending on the local or individual environment, such as the particular temperature used within the appropriate range and the characteristics of the equipment being used. Nevertheless, based on the description herein, those skilled in the art can expect to be able to practice the invention successfully.
    [67] Irradiation of silicon carbide with neutrons, high-energy electrons, or gamma rays is expected to control the number of point defects to some extent and produce the desired number of point defects to achieve results consistent with the above formula.
    [68] Determining the exact number of point defects is difficult, but techniques such as electron paramagnetic resonance (EPR), deep level transient spectroscopy (DLTS), and position annihilation spectroscopy exist It provides the most useful indication of the number. As will be further described herein, Hall effect measurement also identifies the desired properties for the crystal.
    [69] According to another aspect, the present invention can be integrated with active devices, in particular active microwave devices, thereby taking advantage of semi-insulating silicon carbide substrates. As noted above and as would be appreciated by those skilled in the art of active semiconductor microwave devices, the frequency at which the microwave device can operate is ideal for situations where the carrier is limited to a particular channel and other functional parts of the microwave device. In contrast, may be interrupted by any interaction of the carrier with the substrate.
    [70] A feature of the silicon carbide semi-insulating material according to the invention is that it has excellent performance characteristics in a suitable device. Such materials are not limited to MESFETs, but are not limited to specific MOSEFTS, and current US Pat. And Application No. 08 / 891,221, filed Jul. 10, 1997, and Application No. 09 / 082,554, filed May 21, 1998, and entitled "Structure for Increasing the Maximum Voltage of Silicon" Carbide Power Transistors ", filed Feb. 7, 1997, application number 08 / 797,536, filed with the application" Structure to Reduce the On-resistance of Power Transistors ", filed February 7, 1997 08 / 795,135, and other devices such as those disclosed in International Patent PCT / US98 / 13003, filed June 23, 1998, entitled " Power Devices in Wide Bandgap Semiconductors, " Is incorporated herein in its entirety.
    [71] Experiment
    [72] Two wafers of semi-insulated SiC were tested using high temperature Hall effect and SIMS at the Air Force Research Laboratory in Ohio (Light-Patterson Air Force Base) data. Incomprehensible results were obtained on one of the wafers (possibly due to unsatisfactory ohmic contact), but both hole samples from the second wafer provided the same results, giving the results significant reliability.
    [73] Both wafers were semi-insulated at room temperature. The measurable wafer was thermally activated at elevated temperatures and the carrier concentration was measurable, but this is not always possible in semi-insulating materials due to the low mobility due to the high temperatures involved. The carrier concentration was about 10 15 cm −3 at 1000 K, where the resistivity was about 103 μs-cm. Such carrier concentrations are about one to two orders of magnitude lower than those seen with conventional semi-insulating materials or vanadium doped materials at the same temperature. However, n to 1 / T suitability could not be achieved, so the total concentration of the active layer was not available. The activation energy was about 1.1 eV.
    [74] SIMS was performed on the samples using a high resolution system. With some of the hydrogen, nothing near the detection limit was seen with some of the copper, which was inferred from the height of the mass 47 peak. Thus, the mass 47 peak resulted in SiOH. Mass scans for the present invention along with scans for two comparative samples are hereby incorporated as shown in FIGS. 18-20. Titanium (Ti) is shown at about 1 × 10 16 cm −3 in FIGS. 19 and 20 but not in the sample of the invention (FIG. 18). Vanadium also appears in a standard semi-insulated sample (FIG. 20) with a SiOH line representing hydrogen.
    [75] From these results, the first wafer was considered to be a very high pure material and considered to be insulating because any other vanadium impurity is based on the 1.1 eV level and any residual vanadium impurity This is because the concentration appears larger so that the 1.1 eV level compensates for the shallow impurities. The Fermi level is fixed at 1.1 eV, so it is metal semi-insulated. If the presence of hydrogen is necessary, it can mean that hydrogen compensation occurs but such compensation selectively compensates or neutralizes shallower impurities but is not expected to do so at deeper levels.
    [76] In the drawings and specification, exemplary embodiments of the present invention have been disclosed, and specific terms are used, but such terms are merely used generally and not for the purpose of limitation, and the scope of the present invention is set forth in the appended claims. do.
    权利要求:
    Claims (15)
    [1" claim-type="Currently amended] In semi-insulating silicon carbide single crystal,
    Including donor dopants, acceptor dopants, and intrinsic point defects in the silicon carbide single crystal,
    The number of dopants of the first conductivity type is greater than the number of dopants of the second conductivity type,
    The number of intrinsic point defects in the silicon carbide single crystal, which serves to compensate for the predominantly first conductive dopant, is a numerical difference in which the dopant of the first conductivity type is superior to the dopant of the second conductivity type. Greater than)
    The concentration of the transition element is less than 1E16,
    The silicon carbide single crystal has a resistivity of at least 5000 m 3 -cm at room temperature.
    Semi-insulating silicon carbide single crystal.
    [2" claim-type="Currently amended] In semi-insulated bulk silicon carbide single crystal,
    Trapping elements that generate at least 700 meV state from a valence band or conduction band below a resistivity of at least 5000 m-cm at room temperature and below an amount affecting the electrical properties of the single crystal. Semi-insulated bulk silicon carbide single crystal with a concentration of
    [3" claim-type="Currently amended] The silicon carbide single crystal according to claim 1 or 2 having a concentration of nitrogen atoms of less than 1 × 10 17 cm −3 .
    [4" claim-type="Currently amended] 3. The silicon carbide single crystal according to claim 1, wherein the concentration of vanadium is less than 1 × 10 16 cm −3 .
    [5" claim-type="Currently amended] The semi-insulating silicon carbide single crystal of claim 1, wherein the first conductivity type dopant is a donor, the second conductivity type dopant is an acceptor, and the intrinsic point defect serves as an acceptor.
    [6" claim-type="Currently amended] The semi-insulating silicon carbide single crystal of claim 5 wherein the acceptor comprises boron.
    [7" claim-type="Currently amended] The semi-insulating silicon carbide single crystal of claim 1, wherein the first conductivity type dopant is an acceptor, the second conductivity type dopant is a donor, and the intrinsic point defects act as donors.
    [8" claim-type="Currently amended] The silicon carbide single crystal according to claim 1 or 2, wherein the polytype of the silicon carbide is selected from the group consisting of 3C, 4H, 6H and 15R polytypes.
    [9" claim-type="Currently amended] The silicon carbide single crystal according to claim 1 or 2, wherein the concentration of nitrogen is 1 × 10 16 cm −3 or less.
    [10" claim-type="Currently amended] The silicon carbide single crystal according to claim 1 or 2, wherein the concentration of vanadium is below a level that can be detected by secondary ion mass spectrometry (SIMS).
    [11" claim-type="Currently amended] 3. The silicon carbide single crystal according to claim 1, wherein the concentration of vanadium is less than 1 × 10 14 cm −3 .
    [12" claim-type="Currently amended] The silicon carbide single crystal according to claim 1 or 2, having a resistivity of at least 10,000 kPa-cm at room temperature.
    [13" claim-type="Currently amended] The silicon carbide single crystal according to claim 1 or 2 having a resistivity of at least 50,000 kPa-cm at room temperature.
    [14" claim-type="Currently amended] A transistor comprising a substrate comprising the bulk single crystal according to claim 1.
    [15" claim-type="Currently amended] 15. The method of claim 14, wherein the metal-semiconductor field-effect transistors, metal-insulator field effect transistors, and high electron mobility transistors are selected from the group consisting of: Transistor selected.
    类似技术:
    公开号 | 公开日 | 专利标题
    Higashiwaki et al.2016|Recent progress in Ga2O3 power devices
    Higashiwaki et al.2016|Temperature-dependent capacitance–voltage and current–voltage characteristics of Pt/Ga2O3 | Schottky barrier diodes fabricated on n––Ga2O3 drift layers grown by halide vapor phase epitaxy
    Ingebrigtsen et al.2018|Iron and intrinsic deep level states in Ga2O3
    JP2014133701A|2014-07-24|One hundred millimeter high purity semi-insulating single crystal silicon carbide wafer
    Larkin et al.1994|Site‐competition epitaxy for superior silicon carbide electronics
    Chung et al.2001|Improved inversion channel mobility for 4H-SiC MOSFETs following high temperature anneals in nitric oxide
    Binari et al.1997|Fabrication and characterization of GaN FETs
    Choi et al.2006|The effect of an Fe-doped GaN buffer on off-state breakdown characteristics in AlGaN/GaN HEMTs on Si substrate
    Hobgood et al.1995|Semi‐insulating 6H–SiC grown by physical vapor transport
    US5323022A|1994-06-21|Platinum ohmic contact to p-type silicon carbide
    Edgar1992|Prospects for device implementation of wide band gap semiconductors
    Ueda et al.2006|Diamond FET using high-quality polycrystalline diamond with f T of 45 GHz and f max of 120 GHz
    Lebedev2006|Heterojunctions and superlattices based on silicon carbide
    US8785946B2|2014-07-22|Low 1C screw dislocation 3 inch silicon carbide wafer
    Samuelson et al.1981|Electrical and optical properties of deep levels in MOVPE grown GaAs
    US9222198B2|2015-12-29|SiC single crystal wafer and process for production thereof
    Kimoto et al.2001|Reduction of doping and trap concentrations in 4H–SiC epitaxial layers grown by chemical vapor deposition
    Redwing et al.1996|Two‐dimensional electron gas properties of AlGaN/GaN heterostructures grown on 6H–SiC and sapphire substrates
    Mohammad2002|Electrical characteristics of thin film cubic boron nitride
    JP4921694B2|2012-04-25|Delta-doped silicon carbide metal semiconductor field effect transistor and method for manufacturing delta-doped silicon carbide metal semiconductor field effect transistor
    Rao et al.1995|Al and B ion‐implantations in 6H‐and 3C‐SiC
    US6956239B2|2005-10-18|Transistors having buried p-type layers beneath the source region
    Higashiwaki et al.2017|State-of-the-art technologies of gallium oxide power devices
    Hobgood et al.1994|Large diameter 6H-SiC for microwave device applications
    US5463978A|1995-11-07|Compound semiconductor and controlled doping thereof
    同族专利:
    公开号 | 公开日
    US6396080B2|2002-05-28|
    WO2002097173A3|2003-04-17|
    JP4309247B2|2009-08-05|
    JP2005508821A|2005-04-07|
    US20010023945A1|2001-09-27|
    EP1392895B1|2005-08-03|
    AU2002344217A1|2002-12-09|
    ES2243764T3|2005-12-01|
    CN100483739C|2009-04-29|
    EP1392895A2|2004-03-03|
    DE60205369T2|2006-05-24|
    AT301205T|2005-08-15|
    WO2002097173A2|2002-12-05|
    DE60205369D1|2005-09-08|
    CA2446818A1|2002-12-05|
    CN1695253A|2005-11-09|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2001-05-25|Priority to US09/866,129
    2001-05-25|Priority to US09/866,129
    2002-05-23|Application filed by 크리 인코포레이티드
    2002-05-23|Priority to PCT/US2002/016274
    2004-02-11|Publication of KR20040012861A
    优先权:
    申请号 | 申请日 | 专利标题
    US09/866,129|2001-05-25|
    US09/866,129|US6396080B2|1999-05-18|2001-05-25|Semi-insulating silicon carbide without vanadium domination|
    PCT/US2002/016274|WO2002097173A2|2001-05-25|2002-05-23|Semi-insulating silicon carbide without vanadium domination|
    [返回顶部]