PROCESS FOR MANUFACTURING A SILICON CARBIDE COATED BODY

Abstract

The present invention relates to a new process for manufacturing a silicon carbide (SiC) coated body by depositing SiC in a chemical vapor deposition method using dimethyldichlorosilane (DMS) as the silane source on a graphite substrate. A further aspect of the present invention relates to the new silicon carbide coated body, which can be obtained by the new process of the present invention, and to the use thereof for manufacturing articles for high temperature applications, susceptors and reactors, semiconductor materials, and wafer.

Claims

1. A method of depositing a silicon carbide substrate by chemical vapor deposition (CVD), using a dimethyldichlorosilane precursor material, wherein the dimethyldichlorosilane precursor material comprises: (A) dimethyldichlorosilane as a main component and (B) at least one further component being different from dimethyldichlorosilane and being a siloxane compound or a mixture of siloxane compounds, wherein a content of the at least one further component (B) is >0 to 2.00 wt. %, relating to the dimethyldichlorosilane precursor material.

2. The method of claim 1 wherein the dimethyldichlorosilane precursor material comprises a content of siloxane compounds (B) of >0 to 1.500 wt. %.

3. The method of claim 1, wherein the dimethyldichlorosilane precursor material comprises a content of siloxane compounds (B) of not more than 0.500 wt. %.

4. The method of claim 1, wherein the dimethyldichlorosilane precursor material comprises: >0 to 1.000 wt. % 1,3-dichloro-1,1,3,3,-tetramethyldisiloxane; >0 to 0.200 wt. % 1,3-dichloro-1,1,3,5,5,5,-hexamethyltrisiloxane; >0 to 0.200 wt. % octamethylcyclotetrasiloxane; or a combination thereof.

5. The method of claim 1, wherein the dimethyldichlorosilane precursor material further comprises: (C) one or more metal elements selected from the group consisting of Na, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and W, wherein a content of the one or more metal elements (C) is <30.00 ppm wt.

6. The method of claim 5, wherein the one or more metal elements is Mn, and a content of the Mn metal element (C) is <150 ppb wt., relating to the dimethyldichlorosilane precursor material.

7. The method of claim 5, wherein the one or more metal elements is Cu, and a content of the Cu metal element (C) is <50 ppb wt., relating to the dimethyldichlorosilane precursor material.

8. The method of claim 5, wherein the one or more metal elements is Zn, and a content of the Zn metal element (C) is <50 ppb wt., relating to the dimethyldichlorosilane precursor material.

9. The method of claim 5, wherein: the one or more metal elements are Mn, Cu and Zn; a content of Mn (C) is <150 ppb wt., relating to the dimethyldichlorosilane precursor material; a content of Cu (C) is <50 ppb wt., relating to the dimethyldichlorosilane precursor material; and a content of Zn (C) is <50 ppb wt., relating to the dimethyldichlorosilane precursor material.

10. The method of claim 1, wherein the chemical vapor deposition is carried out using H.sub.2 as purge gas.

11. The method of claim 1, wherein the dimethyldichlorosilane precursor material further comprises one or more of the following elements in an amount of: calcium <60.00 ppb by weight, magnesium <10.00 ppb by weight, aluminium <12.00 ppb by weight, titanium <1.00 ppb by weight, chromium <60.00 ppb by weight, iron <25000 ppb by weight, cobalt <1.00 ppb by weight, nickel <30.00 ppb by weight, zinc <40.00 ppb by weight, or molybdenum <10.00 ppb by weight.

12. A body, having a substantially tetrahedral crystalline silicon carbide layer formed thereon, the substantially tetrahedral crystalline silicon carbide layer obtained by chemical vapor deposition of silicon carbide onto the body using dimethyldichlorosilane and one or more siloxane compounds, wherein a content of the one or more siloxane compounds is >0 to 2.00 wt. % as compared to a quantity of a dimethyldichlorosilane precursor material.

13. The body of claim 12, substantially tetrahedral crystalline silicon carbide layer is in a form of tendrils extending with a length of at least 50 m.

14. The body of claim 12, further comprising a substrate, wherein the substrate is a porous graphite substrate having pores therein, having an open porosity with a porosity degree of degree of 6% to 15%, and tendrils of connected crystalline silicon carbide material extend inwardly of at least one of the pores of the porous graphite substrate.

15. The body of claim 14 configured to manufacture articles for high temperature applications, including susceptors and reactors, semiconductor materials, and semiconductor wafers.

16. A silicon carbide coated body, comprising: a coating, the coating comprising a chemical vapor deposited film layer using a dimethyldichlorosilane precursor material, wherein the dimethyldichlorosilane precursor material comprises: (A) dimethyldichlorosilane; and (B) one or more siloxane compounds, wherein a content of the one or more siloxane compounds is >0 to 2.00 wt. %, relating to the dimethyldichlorosilane precursor material.

17. The silicon carbide coated body of claim 16, wherein the content of the one or more siloxane compounds (B) as compared to the content of the dimethyldichlorosilane is from >0 wt. % to 1.500 wt. %.

18. The silicon carbide coated body of claim 16, wherein the dimethyldichlorosilane precursor material comprises a content of siloxane compounds (B) of not more than 0.500 wt. %.

19. The silicon carbide coated body of claim 16, wherein the dimethyldichlorosilane precursor material comprises: >0 to 1.000 wt. % 1,3-dichloro-1,1,3,3,-tetramethyldisiloxane; >0 to 0.200 wt. % 1,3-dichloro-1,1,3,5,5,5,-hexamethyltrisiloxane; >0 to 0.200 wt. % octamethylcyclotetrasiloxane; or a combination thereof.

20. The silicon carbide coated body of claim 16, wherein the dimethyldichlorosilane precursor material further comprises: (C) one or more metal elements selected from the group consisting of Na, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and W, wherein a content of the one or more metal elements (C) is <30.00 ppm by weight, relating to the dimethyldichlorosilane precursor material.

Description

DESCRIPTION OF THE FIGURES AND THE REFERENCE SIGNS

[0503] FIG. 1 shows a SEM image with a 680 fold magnification of a silicon carbide coated body according to the present invention with a graphite substrate (1) and SiC tendrils (4) in the interfacial layer (3) thereof as well as the SiC coating layer (2). It can be seen that the interfacial layer (3) has a thickness of approximately 200 m, i.e. SiC tendrils (4) extend into the porous graphite substrate (1) with a length of at least 50 m. The SiC coating layer (2) has a thickness of approximately 50 m

[0504] FIG. 2 shows a SEM image with a 1250 fold magnification of a silicon carbide coated body with a multilayer SiC coating of different density. The different SiC coating layers exhibit different thickness with a first SiC layer (2-A) of approximately 43 m thickness, a second SiC layer (2-B) of approximately 7 m thickness, and a third SiC layer (2-C) of approximately 50 m thickness. The image further shows the tendrils (4) with the SiC pore filling in the form of a SiC coating of the inner walls of the open pores (5) in the interfacial layer (3).

[0505] FIG. 3 shows a SEM image of a silicon carbide coated body with a SiC coating layer (2) of nearly 100 m thickness on the porous graphite substrate (1) but without formation of tendrils and an interfacial layer. The open pores (6) of the graphite substrate (1) are well apparent.

[0506] FIG. 4 shows a SEM image with a 510 fold magnification of a silicon carbide coated body with a SiC coating layer (2) of more than 50 m thickness on the porous graphite substrate (1) but without formation of tendrils and an interfacial layer due to the use of argon as purge gas. The open pores (6) of the graphite

[0507] FIGS. 5a and 5b show a SEM image with a 500 fold magnification of a top view on the SiC tendrils (4); therefore, the graphite substrate was burnt off in air, morphology and distribution of the tendrils is visible, the distribution of tendril is very uniform and dense

[0508] FIG. 6a shows a SEM image with a 390 fold magnification of a cross-sectional view of SiC tendrils (4), which connect with the SiC coating layer (2) very firmly

[0509] FIG. 6b shows a SEM image with a 2000 fold magnification of the cross-sectional view of SiC tendrils (4), which connect with the SiC coating layer (2) very firmly

[0510] FIGS. 7a and 7b show a SEM image with a 2000 fold magnification of a porous graphite material prior to the purification and activation process of the present invention (pre-product) having quite small pores wherein the pores have a pore size/diameter <10 m

[0511] FIG. 7c shows the pore distribution and the average pore size of said porous graphite material prior to the purification and activation process of the present invention (pre-product)

[0512] FIGS. 8a and 8b show a SEM image with a 2000 fold magnification of a porous graphite material after the activation process of the present invention clearly showing the modified surface porosity with the significantly enlarged surface pores, now comprising a significant amount of enlarged pores having a pore size/diameter 10 m

[0513] FIG. 8c shows the pore distribution and the average pore size of said porous graphite material after the activation process of the present invention illustrating the increased porosity degree and the increased average pore size compared to the graphite material prior to the activation process

[0514] FIG. 9 illustrates the critical temperature dependency and its influence on SiC nucleation, growth and crystal formation in a CVD process

[0515] FIG. 10 shows a SEM image with a 3500 fold magnification of a top view on the improved SiC material of the present invention with the substantially tetrahedral crystallinity and the crystal size up to 10 to 30 m being clearly visible

[0516] FIG. 11 shows an XRD pattern of the improved SiC material of the present invention showing a very sharp p-sic crystallinity peak and showing very little side-product peaks or amorphous SiC, which confirms the high purity and crystallinity of the SiC formed in the process of the present invention

[0517] (1) porous graphite substrate
(2) SiC coating layer
(2-A), (2-B), (2-C) SiC coating layers of different density
(3) interfacial layer with
(4) tendrils formed in open pores
(5) SiC coating on the inner walls of open pores
(6) open pores in the graphite substrate
(7) tight connection between tendrils and coating layer
(8) tetrahedral crystals

VI. Examples

Example 1Activation and Chlorination of a Graphite Member and Tendril Formation

[0518] A porous graphite member was activated, purified and subjected to a chlorination treatment as described in the present invention.

[0519] The following chlorine content was measured in the chlorinated graphite member:

TABLE-US-00001 element graphite member Cl 0.06 ppm wt.

[0520] The formation of activated graphite with enlarged surface porosity has been shown in

[0521] FIGS. 7a to c compared to FIGS. 8a to c. The SEM has been prepared as described above.

[0522] The chlorinated graphite member was used as a porous graphite substrate (1) in a CVD deposition method as described herein.

[0523] In the CVD method SiC tendrils (4) according to the present invention were formed in the pores (6) of the accordingly chlorinated graphite substrate, as shown in FIGS. 1, 2, 3, 4, 5a, 5b, 6a and 6b.

[0524] The SiC characteristics and quality described herein has been shown in FIGS. 10 and 11.

Example 2Influence of the Purge Gas

[0525] A silicon carbide coated body was prepared with the process of the present invention using H.sub.2 as the purge gas.

[0526] As a comparative Example, argon was used as purge gas.

[0527] As becomes apparent from FIGS. 1 and 4, the use of argon does not lead to the formation of tendrils (4).

Example 3Multilayer SiC-Coating

[0528] A silicon carbide coated body was prepared with the process of the present invention, therein varying the amounts of DMS for preparing a multilayer SiC coating having varying densities (2-A), (2-B), (2-C) etc.

[0529] Therein, the following DMS amounts were introduced into the process chamber of a laboratory size test reactor using H.sub.2 as the carrier gas in the deposition phases:

TABLE-US-00002 Deposition phase DMS amount 1. approximately 0.5 g/minute 2. approximately 1.0 g/minute 3. approximately 1.5 g/minute 4. approximately 2.0 g/minute

[0530] The SiC coatings deposited in the first to fourth deposition phase showed varying crystal sizes, which increased with increasing DMS amounts, leading to SiC coating layers with decreasing density.

[0531] A further example, illustrating the SiC multilayer structure due to varying DMS amounts is shown in FIG. 2.

Example 4DMS Purity (Siloxanes)

[0532] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying siloxane impurities.

[0533] DMS with the following amounts of siloxane impurities were used:

TABLE-US-00003 Siloxane compound DMS Sample A DMS Sample B DMS Sample C 1,3-dichloro-1,1,3,3,- 0.193 wt. % 0.103 wt. % 0.710 wt. % tetramethyldisiloxane 1,3-dichloro-1,1,3,5,5,5,- 0.042 wt. % 0.072 wt. % 0.110 wt. % hexamethyltrisiloxane octamethylcyclotetrasiloxane 0.112 wt. % 0.157 wt. % 0.156 wt. % total amount of siloxane 0.389 wt. % 0.375 wt. % 1.04 wt. % impurities total amount of impurities 0.119 wt. % 0.580 wt. % 1.239 wt. %

[0534] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0535] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0536] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00004 Total Siloxane Content Tendril formation >2.00 wt. % 0.50 to 2.00 wt. % + <0.50 wt. % ++ represents no or insufficient tendril formation in the open pores + represents moderate to low tendril formation in the open pores ++ represents adequate to optimum tendril formation in the open pores

Example 5DMS Purity (Mn)

[0537] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying manganese impurities.

[0538] DMS with the following amounts of manganese impurities were used:

TABLE-US-00005 metal element DMS Sample A DMS Sample B DMS Sample C manganese (Mn) 2 ppb wt. 11 ppb wt. 150 ppb wt.

[0539] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0540] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0541] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00006 Total Manganese Content Tendril formation 150 ppb wt. 40 to 150 ppb wt. + <40 ppb wt. ++ represents no or insufficient tendril formation in the open pores + represents moderate to low tendril formation in the open pores ++ represents adequate to optimum tendril formation in the open pores

Example 6DMS Purity (Cu)

[0542] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying copper impurities.

[0543] DMS with the following amounts of copper impurities were used:

TABLE-US-00007 metal element DMS Sample A DMS Sample B DMS Sample C copper (Cu) 1 ppb wt. 18 ppb wt. 41 ppb wt.

[0544] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0545] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0546] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00008 Total Copper Content Tendril formation 50 ppb wt. 30 to <50 ppb wt. + <30 ppb wt. ++ represents no or insufficient tendril formation in the open pores + represents moderate to low tendril formation in the open pores ++ represents adequate to optimum tendril formation in the open pores

Example 7DMS Purity (Zn)

[0547] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying zinc impurities.

[0548] DMS with the following amounts of zinc impurities were used:

TABLE-US-00009 metal element DMS Sample A DMS Sample B DMS Sample C zinc (Zn) 1 ppb wt. 19 ppb wt. 42 ppb wt.

[0549] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0550] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0551] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00010 Total Zinc Content Tendril formation 50 ppb wt. 30 to <50 ppb wt. + <30 ppb wt. ++ represents no or insufficient tendril formation in the open pores + represents moderate to low tendril formation in the open pores ++ represents adequate to optimum tendril formation in the open pores

Example 8DMS Purity (Siloxane Plus Mn Plus Cu Plus Zn)

[0552] The following ranges of total siloxane content in the presence of Mn, Cu and Zn metal impurities were found as effective with respect to the desired tendril formation:

TABLE-US-00011 Total Siloxane Total Manganese Total Copper Total Zinc Tendril Content Content Content Content formation >2.00 wt. % 150 ppb wt. 50 ppb wt. 50 ppb wt. 0.50 to 2.00 wt. % 40 to 150 ppb wt. 30 to <50 ppb wt. 30 to <50 ppb wt. + <0.50 wt. % <40 ppb wt. <30 ppb wt. <30 ppb wt. ++ represents no or insufficient tendril formation in the open pores + represents moderate to low tendril formation in the open pores ++ represents adequate to optimum tendril formation in the open pores