USH28H - Chemical vapor deposition (CVD) of cubic silicon carbide SiC - Google Patents
Chemical vapor deposition (CVD) of cubic silicon carbide SiC Download PDFInfo
- Publication number
- USH28H USH28H US06/752,290 US75229085A USH28H US H28 H USH28 H US H28H US 75229085 A US75229085 A US 75229085A US H28 H USH28 H US H28H
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title abstract description 45
- 229910010271 silicon carbide Inorganic materials 0.000 title abstract description 43
- 238000005229 chemical vapour deposition Methods 0.000 title abstract description 14
- 239000000758 substrate Substances 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 17
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims abstract description 7
- 239000013078 crystal Substances 0.000 claims description 15
- 235000012431 wafers Nutrition 0.000 claims description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 8
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 6
- 229910002804 graphite Inorganic materials 0.000 claims description 6
- 239000010439 graphite Substances 0.000 claims description 6
- 238000010791 quenching Methods 0.000 claims description 6
- 230000000171 quenching effect Effects 0.000 claims description 6
- 238000001039 wet etching Methods 0.000 claims description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 239000010453 quartz Substances 0.000 claims description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N hydrofluoric acid Substances F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims 1
- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 claims 1
- 238000005530 etching Methods 0.000 abstract description 5
- 238000000151 deposition Methods 0.000 abstract description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 2
- 229910052710 silicon Inorganic materials 0.000 abstract description 2
- 239000010703 silicon Substances 0.000 abstract description 2
- 239000007789 gas Substances 0.000 description 15
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000005350 fused silica glass Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000001294 propane Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000012776 electronic material Substances 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/02—Pretreatment of the material to be coated
- C23C16/0272—Deposition of sub-layers, e.g. to promote the adhesion of the main coating
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/02—Pretreatment of the material to be coated
- C23C16/0227—Pretreatment of the material to be coated by cleaning or etching
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
- C23C16/32—Carbides
- C23C16/325—Silicon carbide
Definitions
- the present invention relates to the growth of cubic silicon carbide crystals. More specifically, the present invention relates to the growth of cubic silicon carbide by Chemical Vapor Deposition (CVD).
- CVD Chemical Vapor Deposition
- Cubic silicon carbide (SiC) is considered an excellent candidate for use as a high temperature electronic material because of its large band gap, good carrier mobility and excellent physical stability.
- a primary reason, though, why development of cubic SiC has not been carried further is the lack of a reproducible process for producing the single crystal substrates necessary for device fabrication.
- Nishino et al. teach etching of the Si substrates, on which the cubic SiC crystals are grown in the apparatus used for the CVD, using hydrogen chloride (HCl) vapor at a temperature of about 1200° C. Etching of the substrates in the CVD reactor with hot HCl vapor results in considerable erosion of the graphite susceptor housing the Si substrates. This, in turn, results in random deposition of carbon particles on the Si substrates, with the consequence that there is poor duplicability of the results and impurities are introduced into the cubic SiC as it is grown. Another reason the method of Nishino et al.
- Nishino et al. teach mixing H 2 and C 3 H 8 at room temperature, flowing the mixture over the Si substrates at room temperature, then bringing the temperature to 1360° C. and maintaining the temperature for about 1 minute, followed by cooling.
- the buffer layers formed by this technique are stated to be mainly polycrystalline cubic SiC, by Nishino et al., supra. This is because C 3 H 8 is present throughout the heating step causing different growth conditions for cubic SiC that forms as the temperature is raised from room temperature to 1360° C.
- Nishino et al. also teach to carry out CVD on the buffer layers at a temperature of about 1360° C. This temperature is not the ideal temperature for formation of perfect cubic single crystal layers.
- one object of the present invention is to provide a novel method for the production of cubic SiC for high temperature electronic devices.
- Another object of the present invention is to provide a novel method for the production of highly pure, single crystal cubic SiC that is duplicable.
- Another object of the present invention is to provide a novel method for the production of large-area single-crystal wafers of cubic SiC.
- a method for producing large-area cubic SiC wafers comprising the steps of wet-etching an Si substrate for 10-60 seconds; heating the Si substrate to between 1370° C. and 1405° C. in H 2 gas; exposing the Si substrate to C 3 H 8 for 5-30 seconds, after temperature equilibrium in the heating step has been reached, to form a buffer layer of single crystal cubic SiC on the Si substrate, the amount of C 3 H 8 being no greater than 1 percent by volume of the H 2 gas; quenching the Si substrate having a cubic SiC buffer layer in H 2 to room temperature; heating the Si substrate with the SiC buffer layer to between 1370° C. and 1405° C.
- FIG. 1 is a side view of the apparatus for cubic SiC growth via the CVD process.
- the Si layer 16 during the preparation of the perform is rested atop a graphite susceptor 20 located inside a fused quartz tube 12 and surrounded by an induction coil 15.
- the induction coil 15 raises the temperature of the graphite susceptor near the Si wafer to about 1400° C. causing a gas mixture that has been introduced upstream into the tube 12, to chemically react and deposit the layer of cubic SiC 18 on the Si wafer 16.
- CVD is begun by wet etching the silicon substrate prior to its insertion in the reactor 12 followed by rinsing in de-ionized water and drying.
- the etchant used is a mixture of nitric, hydroflouric and acetic acid usually in the volume ratio 5:3:3, respectively.
- the etchant is used at room temperature, and the etching time is 10-60 seconds, and preferably 30 seconds.
- the Si wafer 16 is placed atop a graphite susceptor 20 located inside a fused quartz tube 12.
- the susceptor 20 is raised at one edge by post 25 so as little of the susceptor 20 as possible is touching the tube 12.
- This susceptor 20 is propped up to minimize heat loss by conduction through the tube 12 since the tube 12 is cooler than its interior and acts as a heat sink.
- a stream of pure hydrogen (H 2 ) gas is introduced into the interior of tube 12 housing the Si wafer.
- the induction coil 15 is turned on and the Si wafer 16 and the area therearound is brought to between 1370° C. and 1405° C.
- propane gas, C 3 H 8 is added to the H 2 stream.
- the C 3 H 8 added to the H 2 stream should be no greater than 1 percent by volume of the H 2 stream.
- the inclusion of C 3 H 8 in the H 2 stream is for 5-30 seconds and preferably 15 seconds, followed by exclusion of the C 3 H 8 and quenching to room temperature of the Si wafer 16 in pure H 2 .
- the carbon in the C 3 H 8 chemically reacts with the Si wafer 16 to form SiC according to the following equations:
- the SiC that forms is cubic and single crystal. Care should be taken to avoid going higher than 1405° C. because hexagonal, 2H SiC crystals form, or lower than 1370° C. because crystal quality becomes very poor.
- the Si substrate now supporting the SiC buffer layer is re-heated to between 1370° C. and 1405° C. in pure H 2 gas. Again, thermal equilibrium is allowed to occur after which time silane (SiH 4 ) and propane are introduced into the H 2 that is flowing past the Si substrate with the SiC buffer layer.
- silane (SiH 4 ) and propane are introduced into the H 2 that is flowing past the Si substrate with the SiC buffer layer.
- the amount of SiH 4 in the H 2 should be 1% by volume of the H 2
- the amount of C 3 H 8 in the H 2 should be 1% volume of the H 2 .
- the presence of SiH 4 and C 3 H 8 is continued for as long as desired, usually between 0.25 and 5 hours, depending on how thick a cubic SiC layer is wanted.
- the growth rate of cubic SiC on the buffer layer is about 4 m/hr and is large enough to obtain cubic SiC layers of the thickness needed for device fabrication in less than an hour.
- the presence of C 3 H 8 and SiH 4 in the gas flowing around the Si substrate is discontinued after the desired time has elapsed.
- the Si substrate with the cubic SiC layer is then quenched in H 2 gas to room temperature. It should be noted that a higher temperature during the CVD process favors formation of more perfect cubic single crystal layers.
- a preferred embodiment of many possible embodiments requires the CVD process to take place in a horizontal, water cooled, rf induction-heated quartz-tube reactor 12 with an internal diameter of 40 mm.
- An open 35-mm-i.d. quartz liner 33 contains the susceptor 20.
- the susceptor is machined from high-density, isotropic, high-purity graphite. Prior to the susceptor's first use, it is coated with SiC.
- the Si substrate 16 rests within a 0.25 mm deep cavity (not shown) in the susceptor 20.
- the substrate 16 is often (100)-oriented P-type Si, with resistivity of about 150 ohm-cm, measuring 12 mm ⁇ 25 mm ⁇ 0.38 mm.
- the substrate 16 is heated to 1400° C. with a flow of 0.6 liters per minute of H 2 passing around the substrate 16. At thermal equilibrium 0.2 milliliters per minute of C 3 H 8 is added to the flow of H 2 for 15 seconds to form the buffer layer, after which time, the C 3 H 8 flow is discontinued and the substrate 16 is quenched to room temperature in the H 2 gas that has continued to flow.
- the cubic SiC buffer layer that forms is about 300 A thick.
- the substrate with the buffer layer is then heated to 1400° C. in the H 2 gas which is flowing at 1.4 liters per minute through the tube 12.
- H 2 gas which is flowing at 1.4 liters per minute through the tube 12.
- C 3 H 8 and SiH 4 are added to the flow of H 2 .
- This mixture is maintained for 2 hours forming an 8 m thick cubic SiC layer.
- the C 3 H 8 and SiH 4 flow is the H 2 gas is discontinued and the Si substrate with a cubic SiC layer is quenched to room temperature in the H 2 gas.
- the Si may be melted at 1420° C. (SiC does not) or the Si may be dissolved in white etch (the SiC does not dissolve) in order to remove the SiC layer 18 from the Si layer 16 after completion of CVD.
Abstract
A method for chemical vapor deposition (CVD) of cubic Silicon Carbide (SiC) comprising the steps of etching silicon substrates having one mechanically polished face; depositing a thin buffer layer of cubic SiC formed by reaction between a heated Si substrate and a H2 C3 H8 gas mixture; and depositing SiC on the buffer layer at high temperature using H2 +C3 H8 +SiH4 mixture.
Description
The present invention relates to the growth of cubic silicon carbide crystals. More specifically, the present invention relates to the growth of cubic silicon carbide by Chemical Vapor Deposition (CVD).
A great need has developed to produce high-temperature electronic devices for advanced turbine engines, geothermal wells, and other applications. Cubic silicon carbide (SiC) is considered an excellent candidate for use as a high temperature electronic material because of its large band gap, good carrier mobility and excellent physical stability. A primary reason, though, why development of cubic SiC has not been carried further is the lack of a reproducible process for producing the single crystal substrates necessary for device fabrication.
A method that attempts to remedy this problem is presented by S. Nishino, J. A. Powell, and H. A. Will, "Production of large-area single-crystal wafers of cubic SiC for semiconductor devices," Appl. Phys. Lett. Vol. 42, No. 5, Pages 460-462, March 1983. However, the method of Nishino et al. results in cubic SiC crystals that are not of a high purity and have poor duplicability. (See A. Addamiano and J. A. Sprague, "Buffer-layer technique for the growth of single crystal SiC on Si," Appl. Phys. Lett. Vol. 44, No. 5, March 1984).
There are several reasons why the method of Nishino et al. is not adequate. Nishino et al. teach etching of the Si substrates, on which the cubic SiC crystals are grown in the apparatus used for the CVD, using hydrogen chloride (HCl) vapor at a temperature of about 1200° C. Etching of the substrates in the CVD reactor with hot HCl vapor results in considerable erosion of the graphite susceptor housing the Si substrates. This, in turn, results in random deposition of carbon particles on the Si substrates, with the consequence that there is poor duplicability of the results and impurities are introduced into the cubic SiC as it is grown. Another reason the method of Nishino et al. is not adequate is because in the formation of a buffer layer of cubic SiC on the Si substrate Nishino et al. teach mixing H2 and C3 H8 at room temperature, flowing the mixture over the Si substrates at room temperature, then bringing the temperature to 1360° C. and maintaining the temperature for about 1 minute, followed by cooling. The buffer layers formed by this technique are stated to be mainly polycrystalline cubic SiC, by Nishino et al., supra. This is because C3 H8 is present throughout the heating step causing different growth conditions for cubic SiC that forms as the temperature is raised from room temperature to 1360° C.
Nishino et al. also teach to carry out CVD on the buffer layers at a temperature of about 1360° C. This temperature is not the ideal temperature for formation of perfect cubic single crystal layers.
Accordingly, one object of the present invention is to provide a novel method for the production of cubic SiC for high temperature electronic devices.
Another object of the present invention is to provide a novel method for the production of highly pure, single crystal cubic SiC that is duplicable.
Another object of the present invention is to provide a novel method for the production of large-area single-crystal wafers of cubic SiC.
These and other objects of the present invention can be achieved by a method for producing large-area cubic SiC wafers comprising the steps of wet-etching an Si substrate for 10-60 seconds; heating the Si substrate to between 1370° C. and 1405° C. in H2 gas; exposing the Si substrate to C3 H8 for 5-30 seconds, after temperature equilibrium in the heating step has been reached, to form a buffer layer of single crystal cubic SiC on the Si substrate, the amount of C3 H8 being no greater than 1 percent by volume of the H2 gas; quenching the Si substrate having a cubic SiC buffer layer in H2 to room temperature; heating the Si substrate with the SiC buffer layer to between 1370° C. and 1405° C. in H2 gas; exposing the Si substrate having the buffer layer to C3 H8 and SiH4, after thermal equilibrium has been reached for 0.25 to 5 hours to make a thicker layer of cubic SiC, the amount of C3 H8 and SiH4 each being no greater than 1 percent by volume of the H2 gas; quenching the Si substrate having the thicker layer of SiC in H2 gas to room temperature.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing, wherein:
FIG. 1 is a side view of the apparatus for cubic SiC growth via the CVD process.
Referring now to the drawing, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, there is shown an Si wafer (16) of structure (100), e.g., for the preparation of a preform 10 comprised of a layer of cubic SiC 18 deposited atop said highly pure wafer of Si 16. The Si layer 16 during the preparation of the perform is rested atop a graphite susceptor 20 located inside a fused quartz tube 12 and surrounded by an induction coil 15. The induction coil 15 raises the temperature of the graphite susceptor near the Si wafer to about 1400° C. causing a gas mixture that has been introduced upstream into the tube 12, to chemically react and deposit the layer of cubic SiC 18 on the Si wafer 16.
More specifically, CVD is begun by wet etching the silicon substrate prior to its insertion in the reactor 12 followed by rinsing in de-ionized water and drying. The etchant used is a mixture of nitric, hydroflouric and acetic acid usually in the volume ratio 5:3:3, respectively. The etchant is used at room temperature, and the etching time is 10-60 seconds, and preferably 30 seconds.
After the etching process is completed, the Si wafer 16 is placed atop a graphite susceptor 20 located inside a fused quartz tube 12. The susceptor 20 is raised at one edge by post 25 so as little of the susceptor 20 as possible is touching the tube 12. This susceptor 20 is propped up to minimize heat loss by conduction through the tube 12 since the tube 12 is cooler than its interior and acts as a heat sink.
When the Si wafer is in place on the susceptor 20 a stream of pure hydrogen (H2) gas is introduced into the interior of tube 12 housing the Si wafer. The induction coil 15 is turned on and the Si wafer 16 and the area therearound is brought to between 1370° C. and 1405° C. After thermal equilibrium is established in the tube 12, propane gas, C3 H8, is added to the H2 stream. The C3 H8 added to the H2 stream should be no greater than 1 percent by volume of the H2 stream. The inclusion of C3 H8 in the H2 stream is for 5-30 seconds and preferably 15 seconds, followed by exclusion of the C3 H8 and quenching to room temperature of the Si wafer 16 in pure H2. While the C3 H8 is present in the tube 12, the carbon in the C3 H8 chemically reacts with the Si wafer 16 to form SiC according to the following equations:
C.sub.3 H.sub.8 =3C+4H.sub.2 (I)
3C+3Si=3SiC (II).
At the temperature of between 1370° C. and 1405° C., the SiC that forms is cubic and single crystal. Care should be taken to avoid going higher than 1405° C. because hexagonal, 2H SiC crystals form, or lower than 1370° C. because crystal quality becomes very poor.
After quenching, the Si substrate now supporting the SiC buffer layer is re-heated to between 1370° C. and 1405° C. in pure H2 gas. Again, thermal equilibrium is allowed to occur after which time silane (SiH4) and propane are introduced into the H2 that is flowing past the Si substrate with the SiC buffer layer. The amount of SiH4 in the H2 should be 1% by volume of the H2, and the amount of C3 H8 in the H2 should be 1% volume of the H2. The presence of SiH4 and C3 H8 is continued for as long as desired, usually between 0.25 and 5 hours, depending on how thick a cubic SiC layer is wanted. For instance, at 1400° C., the growth rate of cubic SiC on the buffer layer is about 4 m/hr and is large enough to obtain cubic SiC layers of the thickness needed for device fabrication in less than an hour. The presence of C3 H8 and SiH4 in the gas flowing around the Si substrate is discontinued after the desired time has elapsed. The Si substrate with the cubic SiC layer is then quenched in H2 gas to room temperature. It should be noted that a higher temperature during the CVD process favors formation of more perfect cubic single crystal layers.
A preferred embodiment of many possible embodiments, requires the CVD process to take place in a horizontal, water cooled, rf induction-heated quartz-tube reactor 12 with an internal diameter of 40 mm. An open 35-mm-i.d. quartz liner 33 contains the susceptor 20. The susceptor is machined from high-density, isotropic, high-purity graphite. Prior to the susceptor's first use, it is coated with SiC. The Si substrate 16 rests within a 0.25 mm deep cavity (not shown) in the susceptor 20. The substrate 16 is often (100)-oriented P-type Si, with resistivity of about 150 ohm-cm, measuring 12 mm×25 mm×0.38 mm. The substrate 16 is heated to 1400° C. with a flow of 0.6 liters per minute of H2 passing around the substrate 16. At thermal equilibrium 0.2 milliliters per minute of C3 H8 is added to the flow of H2 for 15 seconds to form the buffer layer, after which time, the C3 H8 flow is discontinued and the substrate 16 is quenched to room temperature in the H2 gas that has continued to flow. The cubic SiC buffer layer that forms is about 300 A thick.
The substrate with the buffer layer is then heated to 1400° C. in the H2 gas which is flowing at 1.4 liters per minute through the tube 12. At thermal equilibrium 1.2 milliliters per minute of C3 H8 and 0.6 milliliters per minute of SiH4 are added to the flow of H2. This mixture is maintained for 2 hours forming an 8 m thick cubic SiC layer. The C3 H8 and SiH4 flow is the H2 gas is discontinued and the Si substrate with a cubic SiC layer is quenched to room temperature in the H2 gas. The Si may be melted at 1420° C. (SiC does not) or the Si may be dissolved in white etch (the SiC does not dissolve) in order to remove the SiC layer 18 from the Si layer 16 after completion of CVD.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
Claims (3)
1. A method for producing large-area cubic SiC wafers comprising the steps of:
wet-etching an Si substrate;
heating the Si substrate to between 1370° C. and 1405° C. in H2 gas;
exposing the Si substrate to C3 H8 for 5-30 seconds, after temperature equilibrium in the heating step has been reached, to form a buffer layer of single crystal cubic SiC on the Si substrate, the amount of C3 H8 being no greater than 1% by volume of the H2 gas;
quenching to room temperature the Si substrate having a cubic SiC buffer layer in a gas of H2 ;
heating the Si substrate with the SiC buffer layer to between 1370° C. and 1405° C. in H2 gas;
exposing the Si substrate having the buffer layer to C3 H8 and SiH4 after thermal equilibrium has been reached in the second heating step for 0.25 to 5 hours to make a thicker layer of cubic SiC, the amount of C3 H8 and SiH4 each being no greater than 1% by volume of the H2 gas; and
quenching the Si substrate having the thicker layer of SiC in H2 gas to room temperature.
2. A method as described in claim 1 wherein the wet-etching step is carried out in a mixture of nitric, hydrofluoric and acetic acid in a volume ratio of 5:3:3, respectively.
3. A method as described in claim 2 wherein after the wet-etching step, there is an additional step of placing the wet-etched Si substrate on a graphite susceptor inside an rf-induction heated quartz tube.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US06/752,290 USH28H (en) | 1985-07-03 | 1985-07-03 | Chemical vapor deposition (CVD) of cubic silicon carbide SiC |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US06/752,290 USH28H (en) | 1985-07-03 | 1985-07-03 | Chemical vapor deposition (CVD) of cubic silicon carbide SiC |
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USH28H true USH28H (en) | 1986-02-04 |
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US06/752,290 Abandoned USH28H (en) | 1985-07-03 | 1985-07-03 | Chemical vapor deposition (CVD) of cubic silicon carbide SiC |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5363798A (en) * | 1993-09-29 | 1994-11-15 | The United States Of America As Represented By The Secretary Of The Navy | Large area semiconductor wafers |
US20100032857A1 (en) * | 2005-02-28 | 2010-02-11 | Saint-Gobain Ceramics & Plastics, Inc. | Ceramic components, coated structures and methods for making same |
-
1985
- 1985-07-03 US US06/752,290 patent/USH28H/en not_active Abandoned
Non-Patent Citations (3)
Title |
---|
"Buffer-layer" technique for the growth of single crystal SiC on Si," A. Addamiano and J. A. Sprague, NRL, Wash., DC Appl. Phys. Lett. 44 (5) 3/1/84. |
"Chemically-Formed Buffer Layers for Growth of Cubic Silicon Carbide on Silicon Carbide on Silicon Single Crystals" Arrigo Addamiano and Philipp Klein, NRL, Paper presented at ACCG-6 Meeting, Atlantic City, N.J., Jul. 17 and 19, 1984. |
"Reproducible Preparation of Cubic-SiC Single Crystals by Chemical Vapor Deposition," Shigehiro Nishino, Hajime Suhara and Hiroyuki Matsunami, Kyoto University, Kyoto 606, Japan, Abstract of the 15th Conference on Solid State Devices & Materials, Tokyo 1983, pp. 317-320. |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US5363798A (en) * | 1993-09-29 | 1994-11-15 | The United States Of America As Represented By The Secretary Of The Navy | Large area semiconductor wafers |
US20100032857A1 (en) * | 2005-02-28 | 2010-02-11 | Saint-Gobain Ceramics & Plastics, Inc. | Ceramic components, coated structures and methods for making same |
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