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 manufacturing a silicon carbide coated graphite body by chemical vapor deposition, comprising: providing as a porous graphite body is a porous graphite substrate having an open porosity into a reaction chamber; exposing the porous graphite body to dimethyldichlorosilane and gaseous H.sub.2; and depositing a substantially stoichiometric silicon carbide, having a Si:C ratio of 1:1, with substantially tetrahedral silicon carbide crystals on the porous graphite substrate, wherein the the depositing is carried out at a temperature in a range of 1000 to 1200 C. at atmospheric pressure.

2. The method of claim 1, further comprising at least one of: exposing the porous graphite substrate to a silane gas other than dimethyldichlorosilane while exposing the porous graphite substrate to dimethyldichlorosilane and gaseous H.sub.2; and exposing the porous graphite substrate to a methane gas while exposing the porous graphite substrate to dimethyldichlorosilane and gaseous H.sub.2.

3. The method of claim 1, wherein exposing the porous graphite body to dimethyldichlorosilane and gaseous H.sub.2 is performed for at least 30 minutes.

4. The method of claim 1, wherein the dimethyldichlorosilane is flowed into the reaction chamber in a gaseous mixture with H.sub.2 to form a mixture of dimethyldichlorosilane and H.sub.2.

5. The method of claim 4, wherein the mixture of dimethyldichlorosilane and H.sub.2 is obtained by introducing the H.sub.2 into a volume containing the dimethyldichlorosilane, bubbling the H.sub.2 through the dimethyldichlorosilane and flowing a resulting mixture of dimethyldichlorosilane and H.sub.2 into the reaction chamber by pressure in the volume, over the dimethyldichlorosilane, pushing the mixture of dimethyldichlorosilane and H.sub.2 from the volume through an outlet provided therefor.

6. The method of claim 1, wherein the dimethyldichlorosilane comprises siloxane mixed therewith at a value of 0 to 2.000 by weight.

7. The method of claim 1, wherein the dimethyldichlorosilane comprises a metal element included therewith at a value of <150 ppb by weight.

8. The method of claim 1, wherein the porous graphite substrate has an open porosity of 6% to 15%.

9. The method of claim 1, wherein the porous graphite substrate comprises pores with a diameter of 10 to 30 pm, where the pore opens to an outer surface of the porous graphite substrate.

10. The method of claim 1, wherein the substantially stoichiometric silicon carbide with substantially tetrahedral silicon carbide crystals is formed on an outer surface of the porous graphite substrate and in pores of the porous graphite substrate to form tightly connected crystalline silicon carbide material in a form of tendrils extending from a surface of the porous graphite substrate into the pores of the porous graphite substrate and is connected with the porous graphite substrate.

11. The method of claim 1, wherein the amount of free silicon in the silicon carbide deposited on the porous graphite substrate and into pores of the porous graphite substrate comprises not more than about 7 wt. %.

12. A silicon carbide coated component of a high temperature processing apparatus, comprising: a porous graphite substrate having pores extending inwardly of an outer surface of the porous graphite substrate; and a substantially stoichiometric silicon carbide layer, having a Si:C ratio of 1:1 and substantially tetrahedral silicon crystal structure formed on the outer surface of the porous graphite substrate and anchored thereto by tendrils of silicon carbide extending into the pores of the porous graphite substrate.

13. The silicon carbide coated component of claim 12, wherein tetrahedral SiC crystals extend commonly within the substantially stoichiometric silicon carbide layer and a tendril extending therefrom and into a pore of the porous graphite substrate.

14. The silicon carbide coated component of claim 12, wherein the porous graphite substrate has an open porosity of 6% to 15%.

15. The silicon carbide coated component of claim 12, wherein the porous graphite substrate comprises pores with a diameter of 10 to 30 pm where the pore opens to the outer surface of the porous graphite substrate.

16. The silicon carbide coated component of claim 12, wherein the substantially stoichiometric silicon carbide layer includes trace elements of at least one metal therein.

17. A semiconductor processing chamber component, comprising: a porous graphite substrate having pores extending inwardly of an outer surface of the porous graphite substrate; and a substantially stoichiometric silicon carbide layer, having a Si:C ratio of 1:1 and substantially tetrahedral SiC crystal structure formed on the outer surface of the porous graphite substrate and anchored thereto by tendrils of silicon carbide extending into the pores of the porous graphite substrate.

18. The semiconductor processing chamber component of claim 17, wherein tetrahedral SiC crystals extend commonly within the substantially stoichiometric silicon carbide layer and a tendril extending therefrom and into a pore of the porous graphite substrate.

19. The semiconductor processing chamber component of claim 17, wherein the porous graphite substrate has an open porosity of 6% to 15%.

20. The semiconductor processing chamber component of claim 17, wherein the porous graphite substrate comprises pores with a diameter of 10 to 30 pm where the pore opens to the outer surface of the porous graphite substrate.

Description

DESCRIPTION OF THE FIGURES AND THE REFERENCE SIGNS

[0508] 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

[0509] 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).

[0510] 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.

[0511] 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 substrate (1) are well apparent.

[0512] 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

[0513] 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

[0514] 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

[0515] 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

[0516] 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)

[0517] 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

[0518] 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

[0519] FIG. 9 illustrates the critical temperature dependency and its influence on SiC nucleation, growth and crystal formation in a CVD process

[0520] 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

[0521] 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

[0522] (1) porous graphite substrate [0523] (2) SiC coating layer [0524] (2-A), (2-B), (2-C) SiC coating layers of different density [0525] (3) interfacial layer with [0526] (4) tendrils formed in open pores [0527] (5) SiC coating on the inner walls of open pores [0528] (6) open pores in the graphite substrate [0529] (7) tight connection between tendrils and coating layer [0530] (8) tetrahedral crystals

VI. Examples

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

[0531] A porous graphite member was activated, purified and subjected to a chlorination treatment as described in the present invention.

[0532] The following chlorine content was measured in the chlorinated graphite member:

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

[0533] The formation of activated graphite with enlarged surface porosity has been shown in FIGS. 7a to c compared to FIGS. 8a to c. The SEM has been prepared as described above.

[0534] The chlorinated graphite member was used as a porous graphite substrate (1) in a CVD deposition method as described herein.

[0535] 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.

[0536] The SiC characteristics and quality described herein has been shown in FIGS. 10 and 11.

Example 2Influence of the Purge Gas

[0537] A silicon carbide coated body was prepared with the process of the present invention using H.sub.2 as the purge gas.

[0538] As a comparative Example, argon was used as purge gas.

[0539] 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

[0540] 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.

[0541] 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

[0542] 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.

[0543] A further example, illustrating the SiC multilayer structure due to varying DMS amounts is shown in FIG. 2.

Example 4DMS Purity (Siloxanes)

[0544] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying siloxane impurities.

[0545] 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. %

[0546] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0547] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0548] 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)

[0549] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying manganese impurities.

[0550] 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.

[0551] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0552] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0553] 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)

[0554] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying copper impurities.

[0555] 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.

[0556] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0557] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0558] 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)

[0559] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying zinc impurities.

[0560] 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.

[0561] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0562] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0563] 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)

[0564] 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