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    • 专利摘要:
    A semiconductor fabrication process for forming a contact structure with a tungsten plug is shown. The holes of the contact structure are suitably filled with tungsten to avoid plug loss, increase in resistance and trenching as a result of the conventional method. According to one embodiment, a titanium film 003 such as an ion metal plasma method or the like is laminated by an anisotropic sputtering method. The titanium film 003 has a thickness outside the contact hole 020 that is 100 nm or more. However, due to the anisotropic sputtering, the titanium film 003 in the contact hole 020 is thinner than the outside of the contact hole 020. Thereafter, the contact hole 020 is embedded in the tungsten film 005. Thereafter, the tungsten film 005 and the titanium film 003 are etched back to leave a tungsten plug having the shape of the upward protrusion.
    公开号:KR20010030091A
    申请号:KR1020000047157
    申请日:2000-08-16
    公开日:2001-04-16
    发明作者:코바야시미가쿠
    申请人:니시가키 코지；닛뽄덴끼 가부시끼가이샤；
    IPC主号:
    专利说明:

    Method of fabricating a semiconductor device
    BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a contact and / or a bias including a conductive plug.
    The continuous development of the semiconductor manufacturing process has resulted in miniaturization and improved integration. Among the many properties that can be included in semiconductor devices are contact structures (including vias) that generally provide electrical connections between circuit devices and / or layers. The foregoing advances lead to smaller and higher aspect ratio contact structures. Contact aspect ratio refers to the ratio between the depth and width of a contact.
    A typical contact structure includes forming a contact hole in an insulating layer and then embedding such contact hole. A contact structure having a small contact size and a high aspect ratio is more difficult to purchase than a contact structure having a large contact size and a low aspect ratio. Therefore, contact embedding materials are often selected that can appropriately embed contact holes.
    Two types of conductive materials that can be included in the semiconductor manufacturing process are aluminum and copper. The material is contained in a wiring pattern or the like. However, it is not easy to form a compact and high aspect ratio contact made of aluminum. Similarly, copper can also be advantageously provided for low resistance, but it is believed that technical problems must be overcome before the copper contact structure can be put to practical use. In view of the above disadvantages for materials such as aluminum and copper, many conventional contact formation methods include tungsten as the contact embedding material.
    One method of forming a contact structure from tungsten is selective chemical vapor deposition (W-CVD). In the above selective W-CVD method, tungsten can be deposited only on the silicon exposed on the bottom of the contact hole. It is believed that conventional selective W-CVD methods do not have sufficient reproducibility of satisfactory results in the manufacturing process. In addition, the opposite result can occur when the selective W-CVD method is used to embed a depth varying contact. More specifically, contact holes that are shallow for other contact holes are damaged from the overgrowth of tungsten in the contact holes. Excess growth of tungsten can then be corrected with an etch back process that removes only overgrown portions. However, such an etching back process leads to a complicated manufacturing process and a high cost.
    In view of the problems present in the approach by the selective W-CVD method, the blanket W-CVD method is widely used for embedding contact holes. In the blanket W-CVD method, contact holes may be formed in the insulating layer. Tungsten is then deposited on the surface of the insulating layer to fill in the coltact holes. The deposited tungsten is then etched back to remove tungsten from the top surface of the insulating layer, but the tungsten in the contact holes remains. Tungsten remaining in the contact hole is often called a tungsten plug.
    Hereinafter, a conventional technique of forming a tungsten plug in a contact hole by a blanket W-CVD method will be described with reference to FIGS. 3A and 4A.
    In a conventional contact forming process, an interlayer insulating layer film 002 is formed on a silicon substrate 001 having an impurity diffusion layer 011. The interlayer insulating film 002 may include SiO 2 , for example. The contact hole 020 is then formed through the interlayer insulating film 002 to the impurity diffusion layer 001. The structure after the formation of such a contact hole is shown in FIG.
    In FIG. 3B, the titanium film 003 is laminated on the surface of the interlayer insulating film 002 including the contact hole 020 therein. The titanium film 003 may be laminated by a conventional sputtering method with a thickness of about 20 to 50 nm. The conventional sputtering method is isotropic. The titanium film 003 later functions as a barrier film for the contact material to prevent the materials from diffusing into the semiconductor substrate 001.
    In FIG. 3C, after the deposition of the titanium film 003, the titanium nitride film 004 is laminated on the exposed surface to include the contact holes 020 therein. The titanium nitride film 004 is laminated by reaction sputtering to a film thickness of about 20 to 50 nm. In the above reaction sputtering method, the titanium target is a source of titanium. Titanium particles from the target react with nitrogen prior to reaching the surface of the device to provide titanium nitride as a sputtered material.
    The laminated film made of titanium / titanium nitride (003/004) serves as an adhesion layer for the next laminated material, such as tungsten. After lamination of the titanium film / titanium nitride film (003/004), heat treatment may be used to improve the adhesion of the laminated film as described above. As one example, a lamp anneal is performed under heat treatment conditions of 650 占 폚 for 30 seconds. Such annealing of the lamp leads to a reaction between the film material as well as the reaction between the titanium film 003 and the interlayer insulating film 002 which promote the adhesion of the laminated film.
    In Fig. 3D, a tungsten layer 005 is then deposited on the laminated film 003/004 of titanium / titanium nitride. The tungsten deposition process includes, but is merely illustrative of, a source gas comprising tungsten, such as tungsten hexafluoride (WF 6 ). The lamination process as described above forms a layer of tungsten (005) on the laminated film (003/004) of titanium / titanium nitride, and embeds the contact hole (020).
    Thereafter, an etch back step of removing the tungsten portions on the interlayer insulating film 002 and leaving tungsten in the contact hole 020 is performed to form a tungsten plug. Such tungsten etch back process includes a fluorine-containing gas. For example, tungsten is plasma etched with SF 6 as source gas.
    After the tungsten etch back process described above, the exposed portion of the laminated titanium / titanium nitride laminated film 003/004 is removed with a gas containing chlorine. The contact structure after such a process is shown in FIG. The result is a contact structure with a tungsten plug.
    After the formation of the tungsten plug, a wiring film is formed on the semiconductor substrate including the top of tungsten. The wiring film may include aluminum, for example. The wiring film as described above is patterned to form the wiring structure 006. The semiconductor device after formation of the wiring structure 006 is shown in FIG. 4B.
    As such, a conventional W-CVD process is used to form tungsten that connects the wiring structure 006 to the semiconductor substrate 001.
    A disadvantage of the conventional approach as shown in FIGS. 3 a-d and 4 a-d is the result from the shape of the tungsten plug. More specifically, as shown in FIG. 4A, the upper tungsten 005 formed inside the contact hole 020 has a recess. Such a recess is formed when the tungsten film 005 and the stacked titanium / titanium nitride film 003/004 are etched back. More specifically, the above layer is essentially overetched in order not to leave residual tungsten and titanium / titanium nitride on the surface of the interlayer insulating film 002. By the above over etching, the upper portion of the tungsten in the contact hole 020 can be removed.
    If a recess is formed in the upper portion of the tungsten plug (so-called plug loss increases), the step coverage of the upper wiring structure 006 becomes worse. Figure 4b shows the shape as described above. The wiring structure 006 should extend into a part of the contact hole 020 on a step formed when the upper surface of the tungsten 005 is lower than the upper surface of the interlayer insulating film 002. Such a structure results in an unnecessary increase in the resistance of the wiring structure 006. In addition, in the above structure, the material of the wiring layer 006 is liable to cause electromigration.
    In addition, the plug loss causes a difficulty in the following structure. For example, the wiring structure 006 formed on the top of the tungsten plug having the recess has an uneven surface. The second interlayer insulating film is formed on the wiring structure 006. Thereafter, the via holes are etched through the second insulating film to the wiring structure 006. The non-planar surface of the wiring structure 006 makes it difficult to remove all of the second insulating films. If all of the second insulating film is not removed, the via will have a high contact resistance.
    10 shows a conventional sputtering apparatus. Such a device is used to deposit the film of titanium shown in b of FIG. The conventional sputtering apparatus includes a substrate holder 031. The substrate holder 031 supports the semiconductor substrate 032 to be processed so as to be oriented in parallel with the target 035. The target 035 may be formed from the material to be stacked (eg, titanium).
    A magnet is disposed on one surface of the target 035, and the opposite side thereof faces the semiconductor substrate 032. The target 035 may also be connected to the DC power supply 034.
    When a voltage is applied to the target 035, the sputtering particles 037 are released from the target 035. In the conventional approach described, sputtering particles 037 are incident on the semiconductor substrate 032 from various directions due to scattering. Thus, the sputtering apparatus shown in FIG. 10 can provide isotropic sputtered particles.
    One approach for dealing with plug loss is disclosed in Japanese Patent Laid-Open No. 9-321141. In particular, the publication shows a technique in which the thickness of the titanium nitride film is thicker than the thickness by the conventional method described previously. The titanium nitride layer has a thickness of about 100 to 200 nm instead of 20 to 50 nm. The above description will be described with reference to FIGS. 5 a to d and FIGS. 6 a to d.
    In FIGS. 5A to 5 and FIGS. 6A to 6, the interlayer insulating film 002 is formed on the silicon substrate 001 including the impurity diffusion region 011. The interlayer insulating film 002 may include, for example, SiO 2 . Thereafter, a contact hole 020 is formed through the interlayer insulating film 002 to the impurity region 011. The structure after formation of the contact hole 020 is shown in FIG.
    In FIG. 5B, the titanium film 003 may be stacked on the surface of the interlayer insulating film 002 including the contact hole 020 therein. The titanium film 003 may be laminated up to a thickness of about 30 nm by a conventional sputtering method. Conventional sputtering methods are isotropic.
    In FIG. 5C, after the formation of titanium 003, titanium nitride film 004 may be deposited on the exposed surface including contact holes 020 therein. The titanium nitride film 004 may be laminated to a thickness of about 150 to 200 nm by a reaction sputtering method. Conventional reaction sputtering methods are also isotropic.
    In FIG. 5D, a layer of tungsten 005 is then stacked on the layer 003/004 made of titanium / titanium nitride to fill in the contact hole 020.
    In Fig. 6A, an etch back process is then performed to remove portions of tungsten of the interlayer insulating film 002 until the titanium nitride layer 004 is exposed. The tungsten etch back process may include reactive plasma etching with SF 6 and Ar as source gas.
    After the etch back of tungsten, the exposed portion of the titanium / titanium nitride layer (003/004) is etched. The above etching is a two step process. In the first step, the titanium / titanium nitride layer (003/004) is etched with reactive ion etch (RIE) with high selectivity to titanium nitride. The RIE process removes titanium nitride 004 and exposes titanium layer 003. The structure after the first process is shown in b of FIG. 6.
    In the second process, the titanium film / titanium nitride (003/004) is etched by the reactive ion etching method having a lower reactivity than the first reactivity. By way of example only, the second etching process sets the flow rate ratio of Cl 2 gas and Ar gas to 1:30 and the high frequency power to about 450W. By the second process, portions of the titanium film / titanium nitride (003/004) on the interlayer insulating film 002 are removed to form a tungsten plug as shown in FIG.
    As in the conventional example described above, after the formation of the tungsten plug, a wiring film including an aluminum film on the entire surface is formed on the semiconductor substrate 001. The wiring film contains aluminum as an example. The wiring film is then patterned to form the wiring structure 006. The semiconductor device after the wiring structure 006 is formed is shown in FIG.
    As such, a tungsten plug is formed having no top and recessed top as in the case of the method in which plug loss occurs.
    While the techniques of FIGS. 5 a-d and 6 a-d provide a method for solving plug losses, such an approach is not without drawbacks. The disadvantage will be described with reference to a and b of FIG. 9.
    The first problem is insufficient purchase of contact holes. If the thickness of the titanium nitride 004 is increased, the remaining space of the contact holes 020 to be embedded with tungsten 005 is significantly reduced. As mentioned above, the titanium nitride deposition method is essential isotropic. Therefore, a thicker titanium nitride film 005 may be formed on the sidewall of the contact hole 020. As a result, the reduced contact space is shown in a of FIG. 9. It is more difficult to embed such reduced contact spaces in conventional tungsten lamination processes.
    In addition, isotropic lamination of titanium nitride results in a shape that overhangs on top of the contact hole. An example of such a protruding shape is shown in b of FIG. 9. The protruding shape reduces the size of the top of the opening of the contact hole, making it difficult to later embed the contact hole.
    As manufacturing technology advances, contact holes (including via holes) become smaller in size. For example, a contact hole of 0.3 μm or less may be formed. Therefore, in view of the above-mentioned disadvantages, the embedding of such small contact holes becomes increasingly difficult.
    A second problem is the increase in plug resistance. In the technique as shown in Figs. 5A to 5 and 6A to 6, a thicker titanium nitride film is formed on the inner wall of the contact hole. Thus, the contacts may comprise more titanium nitride in cross section than in the case of other conventional methods. Since titanium nitride has a higher resistance than tungsten, the contact structure according to Figs. 5A to 6 and 6A to 6 has higher resistance than other conventional techniques.
    A third problem is the problem of trenching (so-called gouging) on top of the contact structure. The trenching occurs when titanium nitride is removed by etching. More specifically, when an adhesion layer such as titanium / titanium nitride (003/004) is etched, a portion of the adhesion layer on top of the contact structure is removed leaving a recess. The formation of the recess is often called trenching. In the case where the adhesive layer is relatively thin, the above stretching is relatively small. However, when the layer is thick in the method according to Figs. 5 a to d and Figs. 6 a to d, the trenching is large for other conventional techniques. If large trenches occur, the contacts are high in wiring resistance and reduced in electron migration.
    In the process according to a to d of FIG. 5 and a to d of FIG. 6, the two-step etching to remove the adhesive film reduces the trenching in some cases. However, this two step approach can complicate the manufacturing process. Also effective in some cases, the above approach may be ineffective in other cases. In particular, in contact holes with a diameter of 0.3 mu m or less, the effect of trenching is increased, which may not be a sufficient solution.
    In view of the foregoing, there is a need to devise a method of forming a contact hole capable of preventing plug loss without the disadvantages of increased resistance, trenching on top of the contact hole structure, and insufficient embedding of the contact hole. have.
    In accordance with the present invention, a semiconductor manufacturing process includes forming an insulating film on a semiconductor substrate. Thereafter, contact holes are formed in the first insulating film. Thereafter, a titanium film is laminated on the front surface and the contact hole of the first insulating film. The titanium film is laminated on the outer side of the contact hole with a thickness of 100 nm or more by anisotropic sputtering. Thereafter, a titanium nitride film is formed on the entire surface of the titanium film. Thereafter, a tungsten film including a contact hole therein is laminated on the entire surface of the titanium nitride film. Thereafter, tungsten is removed by the first etching step to expose the titanium nitride film on the outside of the contact hole. Thereafter, the titanium film / titanium nitride film is removed from the outside of the contact hole by one or more subsequent etching processes to form a tungsten plug. Thereafter, a wiring conductive film is formed on the entire surface of the tungsten plug.
    According to one aspect of the present invention, by forming the titanium layer by the anisotropic sputtering method, the thickness of the titanium film outside the contact hole may be 100 nm or more, and the thickness of the above film in the contact hole is substantially smaller. This causes tungsten to be deposited in contact holes with few defects. Further, when the titanium film / titanium nitride film is removed, it is formed with the tungsten plug upwardly protruding upper portion.
    1 a to d are side cross-sectional views of the first embodiment.
    2a to c are side cross-sectional views of the first embodiment.
    3A to 3D are side cross-sectional views of a first conventional method for forming a contact.
    4A and 4B are side cross-sectional views of a first conventional method for forming a contact.
    5A to 5D are side cross-sectional views of a second conventional contact formation method.
    6A to 6D are side cross-sectional views of a second conventional contact forming method.
    7 a to d are side cross sectional views of a second embodiment;
    8A to 8C are side cross-sectional views of the second embodiment.
    9A and 9B are side cross-sectional views illustrating problems with the second conventional contact forming method.
    10 is a diagram of a conventional sputtering apparatus.
    11 is a diagram of an ion metal plasma sputtering apparatus.
    12 is a diagram of a collimate sputtering apparatus.
    13 is a diagram of a long throw sputtering device.
    Hereinafter, various embodiments of the present invention will be described in detail with reference to the drawings.
    Hereinafter, a method of forming a contact structure according to the first embodiment will be described with reference to a series of side cross-sectional views shown in FIGS. 1 a to d and FIGS. 2 a to d.
    In FIG. 1A, the first embodiment includes forming an interlayer insulating film 002 on the entire surface of the substrate 001. The interlayer insulating film 002 includes, for example, SiO 2 . The semiconductor substrate 001 includes silicon and an impurity region 011 formed therein.
    As shown in FIG. 1A, the contact hole 020 is formed to the impurity region 011 through the interlayer insulating film 002 of the semiconductor substrate 001. The contact hole 020 has an aspect ratio of 5 or more, more specifically about 6 or more. The contact hole 020 also has an internal diameter of 0.3 μm, more specifically about 0.2 μm, a depth of 1.0 μm or more, and more specifically about 1.2 μm.
    As shown in FIG. 1B, a titanium film 003 including a contact hole 020 therein is then formed on the surface of the interlayer insulating film 002. The titanium film / titanium nitride film 003 has a thickness of about 100 nm or more, preferably 150 nm or more, on the outside of the contact hole 020. The thickness of the titanium film 003 is selected in consideration of the thickness of the contact hole. For example, the upper limit of the film thickness is 300 nm or less, preferably 250 nm or less.
    The thickness of the titanium film 003 must be large enough to prevent recesses in the subsequently formed plug, as described in more detail below. In this way, the problem of plug loss shown in the conventional approach can be overcome. If the thickness of the titanium film 003 on the outer side of the contact hole 020 is too thin, a recess occurs, which causes the above-mentioned problem.
    Note that the titanium film 003 must have a certain thickness in the contact hole 020. If the thickness of the titanium film 003 is too thin, it may not serve as a suitable barrier between the semiconductor substrate 001 and other contact materials. In addition, when the titanium film 003 inside the contact hole 020 is too thin, the adhesion is inadequate. On the other hand, if the titanium film 003 is too thick, the opening of the contact hole 020 is too narrow, which causes a problem in the subsequent embedding of the contact hole 020.
    According to one embodiment, the titanium film 003 is laminated by anisotropic sputtering. The above method generates sputtered particles which are incident almost perpendicularly to the semiconductor substrate. Thus, in the anisotropic sputtering method, the sputtered particles have a large vertical incident component. Under such circumstances, the number of sputtered particles in close contact with the vertical wall of the contact hole is reduced compared to the isotropic sputtering method. As a result, the thickness of the titanium film 003 outside the contact hole 020 is thicker than the thickness of the titanium film 003 inside the contact hole 020.
    It will be recalled that the above-described conventional approach by isotropic sputtering forms a titanium film having almost the same thickness at both the inside and outside of the contact hole. Thicker membranes inside the contact holes have increased contact resistance, which makes it difficult to embed contact holes. The anisotropic sputtering method according to the present invention can overcome the above problems.
    It may be recalled that an isotropic stack of contact materials forms an overhanging structure on top of the contact holes. The protruding structure limits the size of the opening of the contact hole, making it more difficult to embed the contact hole. The anisotropic sputtering approach according to the present invention can also overcome the above problem.
    Although there are several approaches to the anisotropic sputtering scheme according to the present invention, certain possible embodiments may include a collimated sputtering method, a long throw sputtering method, an ion metal plasma method, or the like.
    Among the various mentioned methods, ion metal plasma methods are preferred for contacts and via holes having aspect ratios of 5 or more. The ion metal plasma method can form a film in which the film thickness outside the contact hole is substantially larger than the film thickness on the side wall inside the contact hole. Other such thicknesses may be particularly suitable for forming the contact structure according to the invention. In addition, the ion metal plasma method can provide more efficient sputtering than other anisotropic sputtering methods.
    An example of the ion metal plasma method will be described in more detail below.
    The ion metal plasma method is a physical vapor deposition method including a coil driven by RF energy. The coil is ionized with the sputtered particles located in the sputtering chamber and released from the target.
    An ion metal plasma sputtering apparatus is shown in FIG. 11. The ion metal plasma sputtering apparatus includes a substrate holder 031. The substrate holder 031 supports the semiconductor substrate 32 to be processed in a substantially parallel orientation to the target 035. The target 035 is formed from the material to be stacked (eg titanium).
    The target 035 is connected to the DC power supply 034, and the substrate holder 031 is grounded. A magnet 033 is disposed on one surface of the target 035, and the opposite surface thereof faces the semiconductor substrate 032. The apparatus in Fig. 11 is arranged between the semiconductor substrate 382 and the target 035. A coil 036 is disposed, and the coil 036 is connected to an RF power supply (not shown).
    Sputtering particles are generated due to the application of a voltage to the target 035. Coil 036 generates a high density inductively coupled RF plasma, which ionizes the sputtered particles 039. The ionized sputtered particles are then influenced by an electric field between the target 035 and the substrate semiconductor substrate 032 and are incident on the semiconductor substrate 032 in the vertical direction. As such, in the ion metal plasma method, the sputtered particles are ionized and then influenced by an electric field to provide essential anisotropic sputtering of a material (for example, titanium).
    As one specific example, the ion metal plasma method can adopt the following conditions. The pressure of the sputtering chamber 030 is 20 mTor. The substrate temperature is 150 ° C. The DC power supply is about 2.3 kW. The RF power source for the coil 036 is about 2.8 kW.
    In FIG. 1C, after the essential anisotropic sputtering of titanium, a titanium nitride film 004 is formed. Like the titanium film 003, the titanium nitride film 004 serves as a barrier between the semiconductor substrate 001 and a plug material (for example, tungsten) formed later. Titanium nitride 004 also improves the adhesion of later formed plasma materials.
    In one particular approach, the titanium nitride film 004 is deposited by reaction sputtering. In the above reaction sputtering method, the titanium target becomes a raw material of titanium, and the titanium particles from the target react with nitrogen before reaching the surface of the apparatus.
    In this way, a laminated film of titanium / titanium nitride (003/004) is formed that functions as a barrier layer or adhesion layer for a later stacked material such as tungsten.
    After lamination of the laminated film of titanium / titanium nitride (003/004), temperature cycling conditions are used to further improve the adhesion of the laminated film as described above. By way of example only, lamp annealing is performed at 650 ° C. for 30 seconds. The above lamp annealing leads not only to the reaction between the titanium film 003 and the interlayer insulating film 002 but also to the reaction between the film materials, thereby improving the adhesion of the laminated film.
    In Fig. 1D, a tungsten film 005 is formed on the entire surface of the laminated film of titanium / titanium nitride (003/004). The tungsten lamination process includes a mixed gas comprising a tungsten source gas such as WF 6 . In one specific configuration, the tungsten film 005 is laminated by CVD with a temperature of 400 ° C. and a pressure of about 6 Torrt. The tungsten (W) CVD process as described above forms a layer of tungsten (005) on the entire surface of the laminated film of titanium / titanium nitride (003/004) and embeds the contact hole 020 accordingly.
    After lamination of the tungsten film 005, the tungsten film 005 is etched back to form a plug. Preferably, the tungsten back etching process is such that it has a selectivity between tungsten and titanium nitride.
    As one example, the tungsten etch back process can be performed under the following conditions. Each source gas contains WF 6 flowing at standard cubic centimeters per minute and Ar flowing at about 90 sccm per minute. The etching chamber has a pressure of about 280 mTorr. Such etching is reactive plasma etched with an RF power of about 600 W.
    The tungsten etch back process is performed until the titanium nitride film 004 is exposed outside the contact hole. The contact structure after the tungsten etch back process is shown in FIG. In order to prevent residual tungsten from outside the contact hole 020, the tungsten etch back process needs to be over etched. Thus, as shown in FIG. 2A, the tungsten 005 remaining in the contact hole 020 is recessed with respect to the top surface of the laminated film of titanium / titanium nitride (003/004).
    After the etching back of the tungsten film 005, the titanium film 003 and the titanium nitride film 004 are etched. Such etching is selective between the laminated film of tungsten (005) and titanium / titanium nitride (003/004). A portion of the titanium / titanium nitride film 003/004 at the outside of the contact hole is removed, leaving a contact structure with a tungsten plug 005 having a protruding shape as shown in b of FIG.
    In order to form the tungsten 005 having a protruding shape, the laminated thickness of the laminated film of titanium / titanium nitride (003/004) may be equal to or larger than the recesses generated when the tungsten 005 is etched back.
    One example of etching of the laminated film of titanium / titanium nitride (003/004) can be carried out under the following conditions. The etching gas may include Cl 2 flowing at about 10 sccm and Ar flowing at 30 sccm. The pressure in the etch chamber is about 200 mTorr. The etch is a reactive plasma etch with an RF power source of about 300 W.
    After the formation of the tungsten plug having the protruding shape, a wiring film including the tungsten front surface is formed on the front surface of the semiconductor substrate 001. The wiring film contains, for example, aluminum. The wiring film is then patterned to form the wiring structure 006. The semiconductor device after formation of the wiring structure 006 is shown in FIG. 2C.
    As such, according to the first embodiment, the contact structure is formed of a tungsten plug 005 having a protruding shape as opposed to the recess. This advantageous shape is formed by stacking thicker titanium films 003 for other conventional approaches. In this way, plug loss is prevented.
    In addition, since the titanium film 003 of the first embodiment is laminated by the anisotropic sputtering method, the thickness of the titanium film 003 inside the contact hole 020 is smaller than the thickness of the outer side of the contact hole 020. Thus, a thicker titanium film 003 is provided without narrowing the opening of the contact hole 020 as in the prior art. Since the opening of the contact hole 020 is not reduced, the contact hole 020 is easily buried and does not result in the same high resistance in the above-mentioned prior art.
    One particular embodiment of the formation of a contact structure extending between the interconnect structure 006 and the semiconductor substrate 001 has been described, and a second embodiment of forming a contact structure between two interconnect layers (eg, vias) is described. Will be described.
    In FIG. 7A, the second embodiment includes forming the lower layer wiring 009 on the first interlayer insulating film 007. A second interlayer insulating film 008 is then formed over the entire lower wiring 009. By way of example only, the second interlayer insulating film 008 includes SiO 2 and the lower wiring 009 includes aluminum.
    As shown in FIG. 7A, a via hole 021 is formed through the second interlayer insulating film 008 to the lower wiring 009. The via hole 021 has an aspect ratio of 4 or more, more specifically, 5 or more. The via hole 021 also has an internal diameter of 0.3 μm or less, more specifically 0,2 μm, a depth of 0.8 μm or more and more specifically about 1.0 μm.
    As shown in FIG. 7B, a titanium film 003 including a via hole 021 therein is formed on the surface of the second interlayer insulating film 008. The titanium film 003 has a thickness outside the via hole 021 of about 100 nm or more, and more specifically 150 nm or more. Similar to the first embodiment, the thickness of the titanium film 003 is selected in consideration of the diameter of the via hole. For example, the via holes may have a diameter of 300 nm or less, more specifically 250 nm or less.
    Similar to the first embodiment, the titanium film 003 must be large enough to prevent recession in subsequent plug formation. Titanium film 003 should also have a sufficient thickness in via hole 021. If the film thickness of the titanium film 003 is too thin, it will not function as a suitable barrier between the semiconductor substrate 001 and other via materials, resulting in inadequate adhesion. On the contrary, if the titanium film 003 is not too thick, the opening of the via hole 021 becomes too narrow, so that it is difficult to embed the via hole 021 later.
    According to the second embodiment, the titanium film 003 is laminated by anisotropic sputtering. The above method generates sputtered particles that are incident almost perpendicularly to the semiconductor substrate.
    Several anisotropic sputtering methods are previously known. In a particular second embodiment described herein, the collimated sputtering method will be described in more detail.
    The collimated stuttering method is shown in FIG. The collimating stuttering apparatus includes a substrate holder 031 supporting the semiconductor substrate 032 in parallel with the target 035. The target 035 is formed from a material to be laminated (e.g., titanium).
    The target 035 is connected to the DC power supply 034, and the substrate holder 031 is grounded. The magnet 033 is disposed on one surface of the target 035, and the opposite side faces the semiconductor substrate 032. The apparatus of FIG. 12 includes a shielding plate, referred to herein as collimates. The collimate 038 is disposed between the target 035 and the semiconductor substrate 032.
    Collimates 038 differentiate sputter particles 037. That is, among the various sputtering particles 037 emitted from the target 035, the collimates 038 only allow certain sputtering particles 039 to pass through the semiconductor substrate 001. The specific sputtering particles 039 are sputtering particles which enter the semiconductor substrate 001 just vertically. As such, in the collimated sputtering method, certain sputtering particles 039 are selectively passed through the semiconductor substrate, thereby providing essential anisotropic sputtering of the material (eg, titanium).
    As an example, the collimated stuttering method has the following conditions. The sputtering chamber has an aspect ratio of about two. The pressure of the sputtering chamber is about 2 mTorr. The temperature of the substrate is about 200 ° C. DC power is 1.5 kW.
    In FIG. 7C, after the essential anisotropic sputtering of titanium, a titanium nitride film 004 is formed. The temperature cycling process is then also performed to improve the adhesion of the laminated film of titanium / titanium nitride (003/004). The temperature cycling process is by way of example only a lamp anneal.
    In d of FIG. 7, a tungsten film 005 is laminated. The tungsten sulphide lamination process includes a mixed gas comprising a tungsten source gas such as WF 6 .
    After lamination of the tungsten film 005, the tungsten film 005 is etched to form a plug. Preferably, the tungsten etch back process has a degree of selectivity between tungsten and titanium nitride. The tungsten etching back process is reactive ionic etching with an etching gas containing fluorine.
    The tungsten etch back process is performed until the titanium nitride film 004 on the outside of the via hole 021 is exposed. The contact structure after the tungsten etch back process is shown in FIG.
    After the etching back of the tungsten film 005, the titanium film 003 and the titanium nitride film 004 are etched. Such etching is optional between the tungsten 005 and titanium film 003 / titanium nitride 004. A portion of the laminated film of titanium / titanium nitride (003/004) outside the via holes 021 is removed. The contact structure with tungsten having a protruding shape as shown in b of 8 is left.
    In order to form the tungsten plug 005 having a protruding shape, the thickness of the laminated film of titanium / titanium nitride (003/004) may be equal to or larger than the recesses generated when the tungsten 005 is etched back. The etching of the laminated film of titanium / titanium nitride (003/004) is a reactive plasma etching using a source gas containing chlorine gas.
    After the formation of the tungsten plug having the protruding shape, a second wiring film including the top surface of the tungsten plug 005 is formed on the front surface of the semiconductor substrate 001. The second wiring film contains aluminum as an example. The second wiring film as described above is then patterned to form a second wiring structure. The semiconductor device after formation of the second wiring structure is shown in Fig. 8C.
    As such, according to the second embodiment, the via structure may be formed of a tungsten plug 005 having a protruding shape opposite to the recess. Such a shape is formed by stacking a thick titanium film 003 for another film than the conventional approach. In this way, plug loss of the via is prevented.
    In addition, since the titanium film 003 of the second embodiment is laminated by the essential anisotropic sputtering method, the thickness of the titanium film 003 in the via hole 021 is smaller than the thickness outside the via hole 021. In this way, a thicker titanum film 003 may be provided without narrowing the opening of the via hole 021 as in other conventional approaches. Since the opening of the via hole 021 is not reduced, the via hole 021 is easily buried and can avoid the high resistance as in other conventional cases as described above.
    As described above, the first and second implementations described a method of sputtering anisotropically a particle layer (eg, titanium), but other methods may be used. For example, the third embodiment follows various processes of the first or second embodiment, but may include other methods of sputtering the titanium film anisotropically.
    A long throw sputtering apparatus is shown in FIG. 13. The long throw sputtering apparatus includes a substrate holder 031 capable of supporting the semiconductor substrate 032 in parallel with respect to the target 035. The target 035 is formed from laminated material (eg titanium).
    The target 035 is connected to the DC power supply 034, and the substrate holder 031 is grounded. The magnet 033 is disposed on one surface of the target 035, and the opposite side thereof faces the semiconductor substrate 932. Application of voltage to the target 035 generates sputtering particles.
    The long throw sputtering apparatus differs from the conventional sputtering apparatus in the chamber pressure and the distance between the target 035 and the semiconductor substrate 032. For example, in the conventional sputtering method as shown in FIG. 10, sputtering is generally performed at a pressure of about 2.0 to 10.0 mTorr. In contrast, according to one embodiment, the long throw sputtering method is performed at a low pressure such as 1.0 mTorr or less. In addition, the distance between the target 035 and the semiconductor substrate 001 is about 3 to 6 times higher than that in the conventional sputtering apparatus.
    Low sputtering chamber pressures lead to longer mean free paths for sputtered particles. Thus, the sputtered particles 039 emitted from the target 035 have a more straight path and do not become multiscatter as in the conventional sputtering process.
    The longer distance between the target 035 and the semiconductor substrate 001 leads to more anisotropy of the sputtered particles. More specifically, the particles released at an inclined angle with respect to the semiconductor substrate 032 (ie, have a nearly non-vertical pass component) are attached to the sidewall of the sputtering chamber. Thus, almost all of the sputtered particles that reach the semiconductor substrate 001 are incident vertically, thereby providing an essential anisotropic sputtering of the material (eg, titanium).
    Although various embodiments have been described for contact holes or via holes having a diameter of 0.3 μm or less, such specific contact sizes and shapes should not be taken as limiting the invention.
    However, the present invention provides an advantage suitable for the size of such a relatively small contact hole. In particular, other methods of the present invention have advantages in contact holes / via holes of 0.3 μm or less, and more particularly in particular contact holes / via holes of 0.25 μm or less in diameter. For such small contact / via holes, tungsten is often used as the plug material, which is likely to cause defects as described above. Although it is possible to seek to improve the lamination properties, such an improvement limits the degree of freedom in the process, such as the selection of a particular barrier metal film. Therefore, for the size of the small contact / via hole, it is difficult to simultaneously provide satisfactory lamination characteristics and it is difficult to realize the reduction of plug loss. The present invention seeks to provide satisfactory lamination properties while simultaneously reducing plug loss.
    Various embodiments provide configurations and methods for forming a contact structure (including via holes) comprising a first film (eg, titanium) that is previously anisotropically stacked (eg, tungsten) before the hole buried film (eg, tungsten) to form a plug. Described. Anisotropic lamination includes an ion metal plasma method and the like. In one configuration, the first film thickness outside the contact hole is at least 100 nm. Thus, after the etching back of the hole embedding film and the first film, the plug has a shape having an upward protrusion. As such, the contact / via holes can be embedded without causing an increase in plug loss and resistance.
    While the various specific embodiments described herein have been described in detail, the invention includes various changes, substitutions, modifications and the like without departing from the spirit of the invention. Accordingly, the invention is not limited to only those defined by the appended claims.
    权利要求:
    Claims (20)
    [1" claim-type="Currently amended] In the contact hole forming method,
    Forming a first insulating film,
    Forming a hole through the first insulating film;
    Laminating the titanium layer in an essential anisotropic manner,
    Forming a titanium nitride film;
    Forming a tungsten film,
    Etching the tungsten film,
    And etching the titanium and tungsten films.
    [2" claim-type="Currently amended] The method of claim 1,
    The step of depositing a titanium layer in an essential anisotropic manner comprises the step of depositing titanium according to a method selected from one consisting of ion metal plasma method, collimated sputtering method and long throw method. Hole formation method.
    [3" claim-type="Currently amended] The method of claim 1,
    Forming a contact hole comprises forming a contact hole having a width of 0.25 μm or less.
    [4" claim-type="Currently amended] Anisotropically laminating a first conductive layer on the entire surface of the first insulating layer having a hole having a contact structure formed therein;
    And forming a conductive embedding layer including a hole of a contact structure therein in front of the first conductive layer.
    [5" claim-type="Currently amended] The method of claim 4, wherein
    And laminating the first conductive layer comprises an ion metal plasma physical lamination method.
    [6" claim-type="Currently amended] The method of claim 5,
    The ion metal plasma method for lamination comprises applying a power source of RF in the range of about 2.0 to 3.5 kilowatts to the chamber coil.
    [7" claim-type="Currently amended] The method of claim 5,
    An ion metal plasma method for lamination comprises applying a DC power source in the range of 2.0 to 3.0 kilowatts to a target comprising a first conductive layer material.
    [8" claim-type="Currently amended] The method of claim 4, wherein
    And laminating the first conductive layer comprises a collimated sputtering method.
    [9" claim-type="Currently amended] The method of claim 8,
    The collimated sputtering method includes moving the sputtered particles through a collimator having an aspect ratio of about 2.
    [10" claim-type="Currently amended] The method of claim 8,
    The method of collimating sputtering comprises applying a DC power source in the range of 1.0 to 2.0 kilowatts to a target comprising a first conductive layer material.
    [11" claim-type="Currently amended] The method of claim 4, wherein
    And laminating the first conductive layer comprises a long throw sputtering method.
    [12" claim-type="Currently amended] The method of claim 11,
    Wherein said long throw sputtering method comprises sputtering in a sputtering chamfer at a pressure of only 1.0 mTorr.
    [13" claim-type="Currently amended] The method of claim 4, wherein
    And the first conductive layer comprises titanium.
    [14" claim-type="Currently amended] The method of claim 4, wherein
    Forming the conductive buried layer comprises depositing tungsten by chemical vapor deposition (CVD).
    [15" claim-type="Currently amended] The method of claim 4, wherein
    Etching the conductive buried layer to expose the first conductive layer.
    [16" claim-type="Currently amended] The method of claim 15,
    Etching the first conductive layer to form the first insulating layer, and forming a plug from the conductive embedding layer.
    [17" claim-type="Currently amended] In the contact structure forming method,
    Forming a first conductive layer on the entire surface of the insulating layer having contact holes formed therein having a first thickness on the outside of the contact hole that is thicker than a second thickness on the surface of the contact hole;
    And forming a conductive buried layer on a front surface of the first conductive layer including a contact hole therein.
    [18" claim-type="Currently amended] The method of claim 17,
    And wherein said first conductive layer comprises titanium and said first thickness is at least 100 nm.
    [19" claim-type="Currently amended] The method of claim 17,
    And forming a second conductive layer on the first conductive layer prior to forming the conductive embedding layer.
    [20" claim-type="Currently amended] The method of claim 17,
    Etching the conductive buried layer by etching having a selectivity between the conductive buried layer and the first conductive layer;
    And forming the first conductive layer by etching with a selectivity ratio between the first conductive layer and the conductive buried layer.
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    同族专利:
    公开号 | 公开日
    US20020081850A1|2002-06-27|
    JP3408463B2|2003-05-19|
    US6610597B2|2003-08-26|
    JP2001053026A|2001-02-23|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1999-08-17|Priority to JP23050099A
    1999-08-17|Priority to JP?11-230500
    2000-08-16|Application filed by 니시가키 코지, 닛뽄덴끼 가부시끼가이샤
    2001-04-16|Publication of KR20010030091A
    2007-05-10|First worldwide family litigation filed
    优先权:
    申请号 | 申请日 | 专利标题
    JP23050099A|JP3408463B2|1999-08-17|1999-08-17|Manufacturing method of semiconductor device|
    JP?11-230500|1999-08-17|
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