WO2010087518A1 - エピタキシャル炭化珪素単結晶基板及びその製造方法 - Google Patents
エピタキシャル炭化珪素単結晶基板及びその製造方法 Download PDFInfo
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- WO2010087518A1 WO2010087518A1 PCT/JP2010/051655 JP2010051655W WO2010087518A1 WO 2010087518 A1 WO2010087518 A1 WO 2010087518A1 JP 2010051655 W JP2010051655 W JP 2010051655W WO 2010087518 A1 WO2010087518 A1 WO 2010087518A1
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- single crystal
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- epitaxial
- silicon carbide
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- 239000000758 substrate Substances 0.000 title claims abstract description 128
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 97
- 239000013078 crystal Substances 0.000 title claims abstract description 68
- 230000003746 surface roughness Effects 0.000 claims abstract description 28
- 239000010409 thin film Substances 0.000 claims abstract description 19
- 238000004519 manufacturing process Methods 0.000 claims abstract description 12
- 239000007789 gas Substances 0.000 claims description 59
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 55
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 55
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 55
- 238000000034 method Methods 0.000 claims description 32
- 239000000460 chlorine Substances 0.000 claims description 24
- 238000002230 thermal chemical vapour deposition Methods 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 8
- 229910052710 silicon Inorganic materials 0.000 claims description 8
- 239000010703 silicon Substances 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 125000001309 chloro group Chemical group Cl* 0.000 claims description 3
- 239000010408 film Substances 0.000 abstract description 77
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 230000004888 barrier function Effects 0.000 description 16
- 230000000694 effects Effects 0.000 description 12
- 239000010410 layer Substances 0.000 description 12
- 230000007547 defect Effects 0.000 description 11
- 238000005530 etching Methods 0.000 description 10
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- 238000007796 conventional method Methods 0.000 description 6
- 238000000879 optical micrograph Methods 0.000 description 6
- 230000015556 catabolic process Effects 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000000089 atomic force micrograph Methods 0.000 description 4
- 238000005229 chemical vapour deposition Methods 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 125000004429 atom Chemical group 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 239000011856 silicon-based particle Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- 239000006061 abrasive grain Substances 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000011982 device technology Methods 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 238000002513 implantation Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 235000019592 roughness Nutrition 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 230000002459 sustained effect Effects 0.000 description 1
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 description 1
- 239000005052 trichlorosilane Substances 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
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- 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
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- 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
- C23C16/42—Silicides
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- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
- C30B25/14—Feed and outlet means for the gases; Modifying the flow of the reactive gases
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- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
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- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
Definitions
- the present invention relates to an epitaxial silicon carbide (SiC) single crystal substrate and a manufacturing method thereof.
- SiC Silicon carbide
- a SiC thin film is epitaxially grown on the substrate by a method called thermal CVD (thermochemical vapor deposition) or ion implantation is usually performed.
- thermal CVD thermal chemical vapor deposition
- ion implantation ion implantation
- a dopant is directly implanted by a method, but in the latter case, annealing at a high temperature is required after implantation, and therefore thin film formation by epitaxial growth is frequently used.
- SiC epitaxial substrates with higher quality and larger diameter have been demanded.
- a substrate with an off-angle is used from the viewpoint of stability and reproducibility of epitaxial growth, and is usually 8 °.
- Such a SiC substrate is produced by cutting out a desired angle from a SiC ingot whose surface is a (0001) plane, and the larger the off-angle, the greater the number of substrates that can be obtained from one ingot.
- an off-angle of 6 ° or less is currently required.
- the substrate with the mainstream is the mainstream, and research on epitaxial growth using the substrate has been conducted.
- step-flow growth is less likely to occur during epitaxial growth, and as a result, steps are gathered together. So-called step-bunching occurs.
- Non-Patent Document 1 discloses a method of reducing the atomic ratio (C / Si ratio) of carbon and silicon contained in a material gas (raw material gas) during epitaxial growth. It has been reported. Further, in Patent Document 1, by reducing the C / Si ratio in the initial stage of growth to 0.5 to 1.0, the generation of spiral growth starting from screw dislocation is suppressed, and the probability of being covered by a large amount of surrounding step flow It is said that the epitaxial defects can be reduced by increasing.
- Patent Document 2 discloses that an epitaxial layer is grown in an atmosphere to which hydrogen chloride gas is added in order to obtain an epitaxial thin film having a low crystal defect density and good crystallinity. This is to improve the crystallinity of the epitaxial thin film simply by reducing the crystal defect density by the etching action (cleaning of the substrate surface) of the added hydrogen chloride.
- a SiC substrate having an off angle of 8 ° contains 3 to 30 mL / min HCl and 0.3 mL / min SiH 4 gas (when the Cl / Si ratio is 10 to 100). That is, the epitaxial growth is performed under the condition that the etching action is promoted by increasing the proportion of hydrogen chloride having a Cl / Si ratio of 100 during the growth.
- Patent Document 3 in the case of epitaxial growth by a thermal CVD method, there is a problem that a cubic (3C structure) SiC is formed, and in order to solve the above problem, a hydrogenation gas of silicon, It is disclosed that HCl gas is supplied simultaneously with a hydrocarbon gas and a carrier gas, and it is said that a SiC epitaxial layer can be grown using a tilted substrate tilted at a tilt angle smaller than before (off angle is small).
- patent document 4 discloses that the surface of the SiC substrate is etched and smoothed using Cl 2 gas or HCl gas.
- Patent Document 5 has a problem that silicon particles are formed in a gas phase when the CVD method is performed at a low temperature of about 1200 ° C.
- HCl gas is added. Is disclosed to stabilize the reaction and prevent silicon particles from forming in the gas phase.
- HCl gas is mixed with the source gas in order to promote the reaction of the source gas in the low temperature CVD method and form a SiC crystal film even in a low temperature region of 900 ° C. or lower. Further, since it is a low temperature CVD method, it is said that mirror growth is possible at a substrate temperature of 1400 ° C. or lower.
- HCl gas is added to the source gas in order to flatten the surface of the silicon carbide single crystal film, and a film having a surface roughness of about 5 nm is produced.
- This surface roughness is a CVD method in which the substrate temperature is 1350 ° C., and the flow rate of HCl gas is 3 CCM (Cl / Si ratio is 15) with respect to the flow rate of silane (SiH 4 ) 0.2 CCM. Is obtained.
- the state-of-the-art technology is an epitaxial film in which step-bunching remains.
- the device will be fabricated on top.
- the present inventors made a device on a substrate with a small off-angle and examined it in detail, and as a result, the following became clear.
- a number of irregularities are formed on the surface of such an epitaxial film, and it is easy to cause electrolytic concentration under the device electrode.
- this concentration of electrolysis becomes prominent as a gate leakage current, which degrades device characteristics.
- JP 2008-74664 A JP 2000-001398 A JP 2006-321696 A JP 2006-261563 A JP-A-49-37040 JP-A-2-157196 Japanese Patent Laid-Open No. 4-214099
- a SiC substrate having a small off-angle obtained by the prior art that is, a SiC substrate having an off-angle of 6 ° or less, does not provide a high-quality epitaxial film in which occurrence of step-bunching is suppressed, and device characteristics and It has become clear that there is a problem of insufficient device yield.
- Patent Documents 2 and 3 do not disclose that generation of step-bunching is suppressed when epitaxial growth is performed on a SiC substrate having an off angle of 6 ° or less. Actually, the present inventors examined the conditions disclosed in these documents, and with a SiC substrate having an off angle of 6 ° or less, a high-quality epitaxial film with suppressed generation of step-bunching cannot be obtained. Device characteristics and device yield are not sufficient. Similarly, the same conditions as in Patent Documents 5 to 7 were examined.
- An object of the present invention is to provide an epitaxial single crystal substrate having a high-quality epitaxial film in which generation of step-bunching is suppressed in epitaxial growth using a substrate having an off angle of 6 ° or less and a method for manufacturing the same.
- the present invention has been completed by finding that the above-mentioned problems can be solved by adding hydrogen chloride gas under specific conditions to a material gas (raw material gas) flowing during epitaxial growth. Furthermore, as a result of suppressing the occurrence of step-bunching by the above method, an epitaxial SiC single crystal substrate using an SiC substrate having an off angle of 6 ° or less can be produced. Using the epitaxial SiC single crystal substrate, The device characteristics and device yield were examined in detail. Since an epitaxial SiC single crystal substrate using an SiC substrate having an off angle of 6 ° or less, a silicon carbide single crystal thin film surface having a surface roughness (Ra value) of 0.5 nm or less was not obtained.
- Ra value surface roughness
- the present inventors examined using the epitaxial SiC single crystal substrate produced by the above method, the silicon carbide single crystal thin film surface, It has been found that device characteristics and device yield are remarkably improved when the surface roughness (Ra value) is 0.5 nm or less.
- the gist of the present invention is as follows.
- An epitaxial silicon carbide single crystal substrate in which a silicon carbide single crystal thin film is formed on a silicon carbide single crystal substrate having an off angle of 6 ° or less, and the surface roughness (Ra value) of the silicon carbide single crystal thin film surface. ) Is 0.5 nm or less.
- a source gas containing carbon and silicon is flowed simultaneously with hydrogen chloride gas.
- a ratio of the number of chlorine atoms in the hydrogen chloride gas to the number of silicon atoms in the source gas (Cl / Si ratio) is greater than 1.0 and less than 20.0; Production method.
- (3) The atomic ratio (C / Si ratio) of carbon and silicon contained in the source gas when epitaxially growing the silicon carbide single crystal thin film is 1.5 or less
- an SiC single crystal substrate having a high-quality epitaxial film that suppresses generation of step-bunching and has a small surface roughness Ra value even when the off-angle of the substrate is 6 ° or less. Is possible.
- the manufacturing method of the present invention is a thermal CVD method, an epitaxial film with an easy apparatus configuration, excellent controllability, and high uniformity and reproducibility can be obtained.
- the device using the epitaxial SiC single crystal substrate of the present invention is formed on a high quality epitaxial film having a small surface roughness Ra and excellent flatness, its characteristics and yield are improved.
- 2 shows a growth sequence of a SiC epitaxial film according to an example of the present invention.
- the optical microscope image of the surface state of the SiC epitaxial film grown by the example of this invention is shown.
- 2 shows a surface AFM image of a SiC epitaxial film grown according to an example of the present invention.
- 3 shows forward characteristics of a Schottky barrier diode formed on a SiC epitaxial film grown according to an example of the present invention.
- the optical microscope image of the surface state of the SiC epitaxial film grown by other examples of this invention is shown.
- the growth sequence of the SiC epitaxial film by a prior art is shown.
- the optical microscope image of the surface state of the SiC epitaxial film grown by the prior art is shown.
- 2 shows a surface AFM image of a SiC epitaxial film grown by the prior art.
- the apparatus preferably used for epitaxial growth in the present invention is a horizontal thermal CVD apparatus.
- the thermal CVD method has a simple apparatus configuration and can control growth by turning gas on / off. Therefore, the thermal CVD method is excellent in controllability and reproducibility of the epitaxial film.
- FIG. 6 shows a typical growth sequence in performing conventional epitaxial film growth together with gas introduction timing.
- a substrate is set in a growth furnace, the inside of the growth furnace is evacuated, and hydrogen gas is introduced to adjust the pressure to 1 ⁇ 10 4 to 3 ⁇ 10 4 Pa.
- the temperature of the growth furnace is raised while keeping the pressure constant, and the substrate is etched in hydrogen chloride by introducing hydrogen or hydrogen chloride at about 1400 ° C. for 10 to 30 minutes. This is for removing the altered layer on the surface of the substrate due to polishing or the like, and providing a clean surface.
- the substrate etching step is preferable for cleaning the substrate surface before the growth of the silicon carbide single crystal film, but the effect of the present invention can be obtained without this step.
- the substrate etching step may be omitted. Thereafter, the temperature is raised to a growth temperature of 1500 to 1600 ° C. or 1500 to 1650 ° C., and SiH 4 and C 2 H 4 as material gases (raw material gases) are introduced to start growth (ie, at 1500 ° C. or higher). It is a thermal CVD method of growing.) SiH 4 flow rate per minute 40 ⁇ 50cm 3, C 2 H 4 flow rate per minute 20 ⁇ 40 cm 3 or 30 ⁇ 40 cm 3, the growth rate is per hour 6 ⁇ 7 [mu] m. This growth rate is determined in consideration of productivity because the film thickness of the normally used epitaxial layer is about 10 ⁇ m.
- the introduction of SiH 4 and C 2 H 4 is stopped, and the temperature is lowered while only hydrogen gas is allowed to flow. After the temperature has dropped to room temperature, the introduction of hydrogen gas is stopped, the growth chamber is evacuated, an inert gas is introduced into the growth chamber, the growth chamber is returned to atmospheric pressure, and the substrate is taken out.
- the contents of the present invention will be described with reference to the growth sequence of FIG.
- the process up to the setting of the SiC single crystal substrate and the etching in hydrogen or hydrogen chloride is the same as in FIG. Thereafter, the growth temperature is increased to 1500 to 1600 ° C. or 1500 to 1650 ° C., and SiH 4 and C 2 H 4 which are material gases are flowed to start growth. At this time, HCl gas is also introduced.
- the growth rate is almost the same as when HCl gas is not flown, and the introduction of SiH 4 , C 2 H 4 and HCl is stopped when a desired film thickness is obtained.
- the subsequent procedure is the same as that when no HCl gas is flowed.
- Patent Documents 2 and 3 there is a method proposed in Patent Documents 2 and 3 that uses HCl when epitaxial growth is performed on a SiC substrate with a small off-angle.
- the method of Patent Document 2 aims at improving the quality of the epitaxial film (decreasing the etch pit density) by cleaning the substrate surface.
- a substrate with an off angle of 8 ° is used, and it does not relate to prevention of step-bunching when epitaxial growth is performed on a substrate with an off angle of 6 ° or less.
- the method of Patent Document 3 includes the case of epitaxial growth on a substrate having an off angle of 6 ° or less, but as an effect of adding HCl, a step is forcibly applied to the substrate surface by etching of HCl.
- the formation of 3C-SiC on the surface can be prevented by increasing the number of steps. Therefore, the present invention is basically different from the present invention in which the surface roughness Ra is 0.5 nm or less by utilizing the reaction between Cl and Si generated by the decomposition of HCl.
- HCl gas is introduced together with the source gas during epitaxial growth.
- the etching action of HCl is not used, but Si— Since it takes the form of Cl and uses the action of suppressing the bonding between Si, the growth rate of the epitaxial film is sufficiently large as in the case where HCl is not introduced.
- the condition is such that the amount of HCl introduced is small (Cl / Si ratio is in the range of 1.0 to 20.0) so that the etching action hardly occurs.
- Patent Document 2 as described above, although the SiC substrate has an off-angle of 8 °, HCl is introduced during growth in a range of 10 to 100 in terms of the Cl / Si ratio.
- the above-described effect of the present invention cannot be obtained because it includes conditions for introducing a large amount of HCl such that the Cl / Si ratio exceeds 20 during growth.
- the present invention even on a substrate having a small off angle of 6 ° or less (that is, an off angle of 0 ° to 6 °), the occurrence of surface step-bunching is suppressed.
- An epitaxial film can be obtained, but the thickness of the grown epitaxial layer is preferably 5 ⁇ m or more and 50 ⁇ m or less in consideration of the breakdown voltage of a normally formed device, the productivity of the epitaxial film, and the like.
- a substrate having an off angle exceeding 0 ° and an off angle is preferable from the viewpoint of easy growth of the epitaxial film. Furthermore, if the off-angle of the substrate is 1 ° or less, the number of steps existing on the surface is reduced, and the effects of the present invention are hardly exhibited.
- the Cl / Si ratio contained in the gas during growth is smaller than 1.0, the effect of adding HCl gas does not appear, and if it is larger than 20.0, etching with HCl gas is performed. It is preferably between 0.0 and 20.0, but more preferably between 4.0 and 10.0. A more preferable Cl / Si ratio is 4.0 or more and less than 10.0.
- the C / Si ratio in the material gas is preferably 1.5 or less in order to promote step-flow growth, but if it is less than 1.0, the so-called site-competition effect takes in the residual nitrogen. Is increased, and the purity of the epitaxial film is lowered. Therefore, it is more preferably between 1.0 and 1.5.
- the effect of the present invention is more remarkably obtained when the SiC substrate having an off angle of 6 ° or less is 2 inches or more in diameter (50 mm or more in diameter).
- the SiC substrate is small (for example, less than 2 inches in diameter (diameter 50 mm))
- the effect of suppressing the occurrence of step-bunching may not be exhibited.
- the heating method is not uniform even with a small SiC substrate, step-bunching is likely to occur, so that the effects of the present invention are remarkably obtained.
- the SiC substrate becomes large and becomes 2 inches in diameter (diameter 50 mm) or more, it becomes difficult to uniformly heat the entire substrate surface (maintain a uniform temperature). As a result, step-bunching is likely to occur. Therefore, in a large SiC substrate in which such step-bunching is likely to occur, the effect of suppressing the occurrence of step-bunching can be sufficiently exhibited by introducing HCl under the conditions of the present invention.
- a high-quality SiC single layer having a surface roughness (Ra value) of 0.5 nm or less is obtained by allowing HCl gas at a predetermined flow rate to exist.
- a crystalline thin film can be obtained.
- the surface roughness Ra is an arithmetic average roughness based on JIS B0601: 2001. If the conditions are more optimal in the production method of the present invention, a higher quality SiC single crystal thin film having a surface roughness (Ra value) of 0.4 nm or less can be easily obtained.
- SiC single crystal substrates having various epitaxial films with different surface roughnesses including a surface roughness (Ra value) of 0.5 nm or less were fabricated, and the device characteristics and device yields were examined. .
- a surface roughness (Ra value) of 0.5 nm or less
- device characteristics and device yield are reduced. It has been found that it is significantly improved.
- Devices suitably formed on the epitaxial substrate grown in this manner are devices used for power control, such as Schottky barrier diodes, PIN diodes, MOS diodes, MOS transistors, and the like.
- Example 1 From a SiC single crystal ingot for a 2-inch (50 mm) wafer, sliced at a thickness of about 400 ⁇ m, and subjected to rough grinding and normal polishing with diamond abrasive grains, on the Si surface of a SiC single crystal substrate having a 4H type polytype, Epitaxial growth was performed. The off angle of the substrate is 4 °.
- a substrate was set in a growth furnace, the inside of the growth furnace was evacuated, and then the pressure was adjusted to 1.0 ⁇ 10 4 Pa while introducing 150 L of hydrogen gas per minute.
- FIG. 3 An optical micrograph of the surface of the film epitaxially grown in this way is shown in FIG. 3, and a surface AFM image is shown in FIG. It can be seen from FIG. 2 that the surface is a mirror and no step-bunching has occurred. Further, FIG. 3 shows that the Ra value of the surface roughness is 0.21 nm, which is almost equal to the value of the epitaxially grown film on the 8 ° off substrate.
- FIG. 4 shows the forward characteristics of a diode when a Schottky barrier diode (diameter 200 ⁇ m) is formed using such an epitaxial film. From FIG.
- Example 2 Epitaxial growth was performed on the Si surface of a 2 inch (50 mm) SiC single crystal substrate having a 4H-type polytype, which was sliced, roughly ground, and normally polished in the same manner as in Example 1. The off angle of the substrate is 4 °.
- An optical micrograph of the grown epitaxial film is shown in FIG. From FIG.
- the film is a good film with no step-bunching.
- the Ra value of the surface roughness was 0.16 nm.
- a Schottky barrier diode is formed in the same manner as in Example 1, and HCl is not added during the growth, and withstand voltage in the reverse direction together with the Schottky barrier diode formed on the epitaxial film on the 4 ° off substrate by the conventional method. Evaluated.
- the breakdown voltage (median value) of the diode on the epitaxial film according to the present invention is 340 V
- the breakdown voltage of the diode on the epitaxial film (Ra value of surface roughness: 2.5 nm) according to the conventional method was 320 V
- the diode on the epitaxial film according to the present invention exhibited superior characteristics.
- All 100 diodes fabricated on the epitaxial film according to the present invention were free from defects. Of the 100 diodes fabricated on the epitaxial film by the conventional method, 5 defects occurred.
- Example 3 Epitaxial growth was performed on the Si surface of a 2 inch (50 mm) SiC single crystal substrate having a 4H-type polytype, which was sliced, roughly ground, and normally polished in the same manner as in Example 1. The off angle of the substrate is 4 °.
- the grown epitaxial film was a good film with no step-bunching, and the Ra value of the surface roughness was 0.23 nm.
- a Schottky barrier diode was formed in the same manner as in Example 1 and the n value was obtained, it was 1.01, and it was found that almost ideal characteristics were also obtained in this case.
- 100 Schottky barrier anodes were further produced on the same substrate and subjected to the same evaluation, all showed the same characteristics without any defects.
- Example 4 Epitaxial growth was performed on the Si surface of a 2 inch (50 mm) SiC single crystal substrate having a 4H-type polytype, which was sliced, roughly ground, and normally polished in the same manner as in Example 1.
- the off angle of the substrate is 2 °.
- the grown epitaxial film was a good film with no step-bunching, and the Ra value of the surface roughness was 0.26 nm.
- the n value of the Schottky barrier diode formed in the same manner as in Example 1 was 1.02, and it was found that almost ideal characteristics were also obtained in this case. Similarly to the above, when 100 Schottky barrier anodes were further produced on the same substrate and subjected to the same evaluation, all showed the same characteristics without any defects.
- Example 5 Epitaxial growth was carried out on the Si surface of a 2 inch (50 mm) SiC single crystal substrate having a 4H type polytype that had been sliced, roughly ground, and normally polished as in Example 1. The off angle of the substrate is 6 °.
- the grown epitaxial film was a good film with no step-bunching, and the Ra value of the surface roughness was 0.19 nm.
- 50 reverse breakdown voltages of Schottky barrier diodes were evaluated in the same manner as in Example 2.
- the withstand voltage (median value) of the diode on the epitaxial film according to the present invention is 350 V
- the withstand voltage (median value) of the diode on the epitaxial film (surface roughness Ra value: 2 nm) according to the conventional method is 330 V.
- the diode on the epitaxial film using the invention showed superior characteristics. All 100 diodes fabricated on the epitaxial film according to the present invention were not defective. Of the 100 diodes fabricated on the epitaxial film by the conventional method, 5 defects occurred.
- Example 6 to 17 Epitaxial growth was performed on the Si surface of a 2 inch (50 mm) SiC single crystal substrate having a 4H-type polytype, which was sliced, roughly ground, and normally polished in the same manner as in Example 1.
- the growth procedure, temperature, and the like were the same as in Example 1, and the epitaxial layer was grown to 10 ⁇ m with the substrate off-angle, C / Si ratio, and Cl / Si ratio changed as shown in Table 1.
- the grown epitaxial film is a good film with no step-bunching.
- Table 1 shows the Ra value of the surface roughness of the grown epitaxial film and the n value of the Schottky barrier diode formed in the same manner as in Example 1. Is also shown.
- Ra values were all 0.4 nm or less, and a film having excellent flatness was obtained. Also, an n value was 1.03 or less, and almost ideal diode characteristics were obtained.
- the substrate was etched with hydrogen chloride before growth. However, even if this process was omitted, the Ra value after growth was not changed.
- the Ra value is 0.4 nm and the n value is 1.03. However, since the substrate has no off-angle, the crystal growth rate is low and the substrate has an off-angle. It takes a long time to form a film having a thickness of 10 ⁇ m as compared with the case of using the film.
- the surface after growth has a hook shape and step-bunching occurs.
- the Ra value of the surface roughness was 1.9 nm, which was about one digit larger than Examples 1-5.
- Example 5 when a Schottky barrier diode was formed on such an epitaxial film and the reverse breakdown voltage was evaluated, the characteristics were inferior to those of the diode on the epitaxial film according to the present invention. It was. Similarly, 100 Schottky barrier diodes were produced, of which 8 defects occurred.
- a SiC single crystal substrate having a substrate off-angle of 7 ° was fabricated in the same manner as in Example 1, and the case where HCl was flowed simultaneously with the source gas and the case where HCl was not flowed were epitaxially formed as in Example 1.
- a film was grown. Since the off-angle is large, step-bunching hardly occurs in the first place. Therefore, the growth surface is flat without adding HCl, and the growth surface has the same flatness even when HCl is added.
- Example 1 the temperature at the time of crystal growth in Example 1 is 1600 ° C., and the same crystal growth was performed at 1500 ° C. and 1650 ° C., respectively, but the same result was obtained. Crystal growth was carried out at 1450 ° C. in the same manner as in Example 1. However, when a Schottky barrier diode was manufactured, the defect occurrence rate increased. In addition, crystals were grown at 1700 ° C. in the same manner as in Example 1, but only those having an Ra value of surface roughness exceeding 0.4 were obtained. Therefore, the temperature range during crystal growth is preferably 1500 to 1650 ° C.
- the present invention it is possible to produce an epitaxial SiC single crystal substrate having a high-quality epitaxial film with less step-bunching in epitaxial growth on the SiC single crystal substrate. Therefore, if an electronic device is formed on such a substrate, it can be expected that the characteristics and yield of the device are improved.
- SiH 4 and C 2 H 4 are used as the material gas, but the same applies to the case where trichlorosilane is used as the Si source and C 3 H 8 is used as the C source.
Abstract
Description
(1)オフ角度が6°以下である炭化珪素単結晶基板上に炭化珪素単結晶薄膜を形成したエピタキシャル炭化珪素単結晶基板であって、前記炭化珪素単結晶薄膜表面の表面粗さ(Ra値)が0.5nm以下であることを特徴とするエピタキシャル炭化珪素単結晶基板。
(2)オフ角度が6°以下である炭化珪素単結晶基板上に、熱化学蒸着法で炭化珪素単結晶薄膜をエピタキシャル成長させる際に、炭素と珪素を含む原料ガスを流すと同時に塩化水素ガスを流し、原料ガス中の珪素原子数に対する塩化水素ガス中の塩素原子数の比(Cl/Si比)が1.0より大きく20.0より小さくすることを特徴とするエピタキシャル炭化珪素単結晶基板の製造方法。
(3)前記炭化珪素単結晶薄膜をエピタキシャル成長する際の、原料ガス中に含まれる、炭素と珪素の原子数比(C/Si比)が1.5以下であることを特徴とする上記(2)に記載のエピタキシャル炭化珪素単結晶基板の製造方法。
まず、SiC単結晶基板上へのエピタキシャル成長について述べる。
本発明で好適にエピタキシャル成長に用いる装置は、横型の熱CVD装置である。熱CVD法は、装置構成が簡単であり、ガスのon/offで成長を制御できるため、エピタキシャル膜の制御性、再現性に優れた成長方法である。
2インチ(50mm)ウェーハ用SiC単結晶インゴットから、約400μmの厚さでスライスし、粗削りとダイヤモンド砥粒による通常研磨を実施した、4H型のポリタイプを有するSiC単結晶基板のSi面に、エピタキシャル成長を実施した。基板のオフ角は4°である。成長の手順としては、成長炉に基板をセットし、成長炉内を真空排気した後、水素ガスを毎分150L導入しながら圧力を1.0×104Paに調整した。その後、圧力を一定に保ちながら成長炉の温度を上げ、1550℃に到達した後、塩化水素を毎分1000cm3流し、20分間基板のエッチングを行った。エッチング後、温度を1600℃まで上げ、SiH4流量を毎分40cm3、C2H4流量を毎分22cm3(C/Si=1.1)、HCl流量を毎分200cm3(Cl/Si=5.0)にしてエピタキシャル層を10μm成長した。この時の成長速度は毎時7μm程度であった。
実施例1と同様にスライス、粗削り、通常研磨を行った、4H型のポリタイプを有する2インチ(50mm)のSiC単結晶基板のSi面に、エピタキシャル成長を実施した。基板のオフ角は4°である。成長手順、温度等は、実施例1と同様であるが、ガス流量は、SiH4流量を毎分40cm3、C2H4流量を毎分22cm3(C/Si=1.1)、HCl流量を毎分400cm3(Cl/Si=10.0)にして、エピタキシャル層を10μm成長した。成長後のエピタキシャル膜の光学顕微鏡写真を図5に示す。図5から、この条件の場合もステップ−バンチングの生じていない良好な膜であることが分かる。また、AFM評価から、表面粗さのRa値は0.16nmであった。成長後、実施例1と同様にショットキーバリアダイオードを形成し、成長中にHClを添加しない、従来の方法による4°オフ基板上のエピタキシャル膜上に形成したショットキーバリアダイオードと共に逆方向の耐圧を評価した。それぞれのダイオードを100個評価した結果は、本発明によるエピタキシャル膜上のダイオードの耐圧(中央値)が340V、従来方法によるエピタキシャル膜(表面粗さのRa値:2.5nm)上のダイオードの耐圧(中央値)が320Vであり、本発明によるエピタキシャル膜上のダイオードの方が優れた特性を示していた。本発明によるエピタキシャル膜上に作製した100個のダイオードは、全て不良のないものであった。従来方法によるエピタキシャル膜上に作製した100個のダイオードの内、5個の不良が発生した。
実施例1と同様にスライス、粗削り、通常研磨を行った、4H型のポリタイプを有する2インチ(50mm)のSiC単結晶基板のSi面に、エピタキシャル成長を実施した。基板のオフ角は4°である。成長手順、温度等は、実施例1と同様であるが、ガス流量は、SiH4流量を毎分40cm3、C2H4流量を毎分28cm3(C/Si=1.4)、HCl流量を毎分200cm3(Cl/Si=5.0)にして、エピタキシャル層を10μm成長した。成長後のエピタキシャル膜はステップ−バンチングの生じていない良好な膜であり、表面粗さのRa値は0.23nmであった。実施例1と同様にショットキーバリアダイオードを形成し、n値を求めると1.01であり、この場合もほぼ理想的な特性が得られていることが分かった。また、前記と同様に、同基板上にショットキーバリアオードを更に100個作製して同じ評価を行ったところ、全て不良なく同様の特性を示した。
実施例1と同様にスライス、粗削り、通常研磨を行った、4H型のポリタイプを有する2インチ(50mm)のSiC単結晶基板のSi面に、エピタキシャル成長を実施した。基板のオフ角は2°である。成長手順、温度等は、実施例1と同様であるが、ガス流量は、SiH4流量を毎分40cm3、C2H4流量を毎分20cm3(C/Si=1.0)、HCl流量を毎分400cm3(Cl/Si=10.0)にして、エピタキシャル層を10μm成長した。成長後のエピタキシャル膜はステップ−バンチングの生じていない良好な膜であり、表面粗さのRa値は0.26nmであった。実施例1と同様に形成したショットキーバリアダイオードのn値は1.02であり、この場合もほぼ理想的な特性が得られていることが分かった。また、前記と同様に、同基板上にショットキーバリアオードを更に100個作製して同じ評価を行ったところ、全て不良なく同様の特性を示した。
実施例1と同様にスライス、粗削り、通常研磨を行った、4H型のポリタイプを有する2インチ(50mm)のSiC単結晶基板のSi面に、エピタキシャル成長を実施した。基板のオフ角度は6°である。成長手順、温度等は、実施例1と同様であるが、ガス流量は、SiH4流量を毎分40cm3、C2H4流量を毎分22cm3(C/Si=1.1)、HCl流量を毎分200cm3(Cl/Si=5.0)にして、エピタキシャル層を10μm成長した。成長後のエピタキシャル膜はステップ−バンチングの生じていない良好な膜であり、表面粗さのRa値は0.19nmであった。このエピタキシャル膜と、従来の方法により形成した6°オフ基板上のエピタキシャル膜を用い、実施例2と同様にショットキーバリアダイオードの逆方向耐圧を50個評価した。結果は、本発明によるエピタキシャル膜上のダイオードの耐圧(中央値)が350V、従来方法によるエピタキシャル膜(表面粗さのRa値:2nm)上のダイオードの耐圧(中央値)が330Vであり、本発明を用いたエピタキシャル膜上のダイオードの方が優れた特性を示していた。本発明によるエピタキシャル膜上に作製した100個のダイオードは、全て不良ないものであった。従来方法によるエピタキシャル膜上に作製した100個のダイオードの内、5個の不良が発生した。
実施例1と同様にスライス、粗削り、通常研磨を行った、4H型のポリタイプを有する2インチ(50mm)のSiC単結晶基板のSi面に、エピタキシャル成長を実施した。成長手順、温度等は、実施例1と同様であり、基板のオフ角度、C/Si比、Cl/Si比を表1のように変えてエピタキシャル層を10μm成長した。成長後のエピタキシャル膜はステップ−バンチングの生じていない良好な膜であり、表1には成長後のエピタキシャル膜表面粗さのRa値および実施例1と同様に形成したショットキーバリアダイオードのn値も示してある。Ra値は全て0.4nm以下と、平坦性に優れた膜が得られていることが分かり、また、n値も1.03以下で、ほぼ理想的なダイオード特性が得られていた。なお、実施例1~17においては、成長前に塩化水素による基板のエッチングを行っているが、このプロセスを省略しても、成長後のRa値に変化は見られなかった。また、実施例6は、Ra値が0.4nmで、n値が1.03となっているが、基板のオフ角度が付いていないので、結晶成長速度が遅く、オフ角度が付いている基板を用いた場合に比べて10μmの厚さに成膜するのに長時間かかっている。
比較例として、実施例1と同様にスライス、粗削り、通常研磨を行った、4H型のポリタイプを有する2インチ(50mm)のSiC単結晶基板のSi面に、エピタキシャル成長を実施した。基板のオフ角度は6°である。成長手順、温度等は、実施例1と同様であるが、ガス流量は、SiH4流量を毎分40cm3、C2H4流量を毎分22cm3(C/Si=1.1)にして、HClは流さずにエピタキシャル層を10μm成長した。成長後のエピタキシャル膜の光学顕微鏡写真を図7に、表面AFM像を図8に示す。図7、図8から、成長後の表面は皺状になっており、ステップ−バンチングが生じていることが分かる。また、図8から、表面粗さのRa値は1.9nmであり、実施例1~5に比べ、約一桁大きい値であった。実施例5の場合に示したように、このようなエピタキシャル膜上にショットキーバリアダイオードを形成し、逆方向の耐圧を評価したところ、本発明によるエピタキシャル膜上のダイオードに比べ、特性は劣っていた。同様に100個のショットキーバリアダイオードを作製し、その内8個の不良が発生した。
Claims (3)
- オフ角度が6°以下である炭化珪素単結晶基板上に炭化珪素単結晶薄膜を形成したエピタキシャル炭化珪素単結晶基板であって、前記炭化珪素単結晶薄膜表面の表面粗さ(Ra値)が0.5nm以下であることを特徴とするエピタキシャル炭化珪素単結晶基板。
- オフ角度が6°以下である炭化珪素単結晶基板上に、熱化学蒸着法で炭化珪素単結晶薄膜をエピタキシャル成長させる際に、炭素と珪素を含む材料ガスを流すと同時に塩化水素ガスを流し、材料ガス中の珪素原子数に対する塩化水素ガス中の塩素原子数の比(Cl/Si比)が1.0より大きく20.0より小さくすることを特徴とするエピタキシャル炭化珪素単結晶基板の製造方法。
- 前記炭化珪素単結晶薄膜をエピタキシャル成長する際の、材料ガス中に含まれる、炭素と珪素の原子数比(C/Si比)が1.5以下であることを特徴とする請求項2に記載のエピタキシャル炭化珪素単結晶基板の製造方法。
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
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EP10735972.1A EP2395133B1 (en) | 2009-01-30 | 2010-01-29 | Method for producing epitaxial silicon carbide single crystal substrate |
CN201080005900.5A CN102301043B (zh) | 2009-01-30 | 2010-01-29 | 外延碳化硅单晶基板及其制造方法 |
KR1020117013379A KR101333337B1 (ko) | 2009-01-30 | 2010-01-29 | 에피텍셜 탄화규소 단결정 기판 및 그 제조 방법 |
JP2010523229A JP4719314B2 (ja) | 2009-01-30 | 2010-01-29 | エピタキシャル炭化珪素単結晶基板及びその製造方法 |
US13/138,270 US20110278596A1 (en) | 2009-01-30 | 2010-01-29 | Epitaxial silicon carbide monocrystalline substrate and method of production of same |
US14/547,838 US20150075422A1 (en) | 2009-01-30 | 2014-11-19 | Epitaxial silicon carbide monocrystalline substrate and method of production of same |
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US14/547,838 Division US20150075422A1 (en) | 2009-01-30 | 2014-11-19 | Epitaxial silicon carbide monocrystalline substrate and method of production of same |
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Cited By (12)
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WO2012127748A1 (ja) * | 2011-03-22 | 2012-09-27 | 住友電気工業株式会社 | 炭化珪素基板 |
JP2015510691A (ja) * | 2012-01-30 | 2015-04-09 | クラッシック ダブリュビージー セミコンダクターズ エービーClassic WBG Semiconductors AB | 塩素化の化学系を用いたcvdリアクタ内での炭化ケイ素結晶の成長 |
JP2014047090A (ja) * | 2012-08-30 | 2014-03-17 | Fuji Electric Co Ltd | 炭化珪素半導体装置の製造方法 |
WO2014157332A1 (ja) * | 2013-03-27 | 2014-10-02 | 住友電気工業株式会社 | 炭化珪素半導体基板の製造方法 |
JP2014189442A (ja) * | 2013-03-27 | 2014-10-06 | Sumitomo Electric Ind Ltd | 炭化珪素半導体基板の製造方法 |
US9269572B2 (en) | 2013-03-27 | 2016-02-23 | Sumitomo Electric Industries, Ltd. | Method for manufacturing silicon carbide semiconductor substrate |
CN103715069A (zh) * | 2013-12-02 | 2014-04-09 | 中国电子科技集团公司第五十五研究所 | 一种减少碳化硅外延薄膜中缺陷的方法 |
KR20170102021A (ko) | 2015-03-03 | 2017-09-06 | 쇼와 덴코 가부시키가이샤 | SiC 에피택셜 웨이퍼, SiC 에피택셜 웨이퍼의 제조 방법 |
US10865500B2 (en) | 2015-03-03 | 2020-12-15 | Showa Denko K.K. | SiC epitaxial wafer and method for manufacturing SiC epitaxial wafer |
WO2017110550A1 (ja) * | 2015-12-24 | 2017-06-29 | 昭和電工株式会社 | SiCエピタキシャルウェハの製造方法 |
JP2017117907A (ja) * | 2015-12-24 | 2017-06-29 | 昭和電工株式会社 | SiCエピタキシャルウェハの製造方法 |
US10774444B2 (en) | 2015-12-24 | 2020-09-15 | Showa Denko K.K. | Method for producing SiC epitaxial wafer including forming epitaxial layer under different conditions |
Also Published As
Publication number | Publication date |
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US20150075422A1 (en) | 2015-03-19 |
KR20110093892A (ko) | 2011-08-18 |
EP2395133A4 (en) | 2014-04-16 |
CN102301043B (zh) | 2014-07-23 |
US20110278596A1 (en) | 2011-11-17 |
JPWO2010087518A1 (ja) | 2012-08-02 |
JP4719314B2 (ja) | 2011-07-06 |
KR101333337B1 (ko) | 2013-11-25 |
EP2395133B1 (en) | 2020-03-04 |
EP2395133A1 (en) | 2011-12-14 |
CN102301043A (zh) | 2011-12-28 |
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