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 an activated graphite substrate with a modified surface porosity, comprising: i) positioning a porous graphite substrate in a process chamber, the porous graphite substrate having an open porosity comprising pores with a surface pore diameter of less than 30 m; ii) purging the porous graphite substrate with nitrogen; iii) heating the porous graphite substrate in the process chamber to a first temperature; and iv) continuing purging with nitrogen in the process chamber and heating the porous graphite substrate to a second temperature.

2. The method of claim 1, further comprising annealing the porous graphite substrate at a third temperature after purging the porous graphite substrate with nitrogen and heating of the porous graphite substrate to the second temperature until the process chamber reaches a first oxygen content.

3. The method of claim 1, further comprising directly subjecting the porous graphite substrate to a chemical vapor deposition treatment after continuing purging with nitrogen in the process chamber and heating of the porous graphite substrate to the second temperature, without cleaning the porous graphite substrate before the chemical vapor deposition treatment.

4. The method of claim 1, wherein before heating the porous graphite substrate in the process chamber to the first temperature, nitrogen is flowed in the process chamber until an oxygen content in the process chamber is 3.0%.

5. The method of claim 1, wherein after heating the porous graphite substrate in the process chamber to the first temperature, heating is continued until an oxygen content is reduced to 0.3% or less, wherein the first temperature is at least 1000 C.

6. The method of claim 1, wherein the porous graphite substrate, prior to being placed in the process chamber, has a chlorine content of at least 20.00 ppb by weight, wherein said chlorine content is present in the graphite substrate being 50 m or more below a surface.

7. The method of claim 1, wherein the first temperature and the second temperature are between 1000 and 1500 C., and wherein the porous graphite substrate has a modified surface porosity comprising pores with an average pore diameter of >10 m at a surface of the activated graphite substrate.

8. The method of claim 1, wherein after continuing purging with nitrogen in the process chamber and heating of the porous graphite substrate to the second temperature, the pores of the porous graphite substrate have an average pore diameter which is enlarged compared to the pores thereof prior to being placed in the process chamber, wherein the second temperature is more than 1000 C., a first oxygen content is less than 0.5%, and the porous graphite substrate having a first average grain size less than 0.05 mm.

9. The method of claim 1, wherein the porous graphite substrate has a total amount of impurities of 10.00 ppm or less by weight.

10. A method of processing a porous graphite substrate, comprising: i) positioning a porous graphite substrate in a process chamber; ii) purging the porous graphite substrate with nitrogen; iii) heating the porous graphite substrate in the process chamber to a first temperature; and iv) continuing purging with nitrogen in the process chamber and heating the porous graphite substrate to a second temperature; heating of the porous graphite substrate to a third temperature greater than the second temperature and initiating purging with chlorine gas to form a chlorine atmosphere; and heating the porous graphite substrate in the chlorine atmosphere to a fourth temperature of greater than the third temperature.

11. The method of claim 10, wherein the porous graphite substrate has an open porosity comprising pores with a surface pore diameter of less than 30 m and the porous graphite substrate has a total amount of impurities of 10.00 ppm or less by weight, and wherein the porous graphite substrate has a first average grain size.

12. The method of claim 10, wherein after continuing purging with nitrogen in the process chamber and heating of the porous graphite substrate to the second temperature, the porous graphite substrate having a modified average pore diameter which is enlarged compared to an average pore diameter prior to being placed in the process chamber.

13. The method of claim 10, wherein the porous graphite substrate, prior to being placed in the process chamber, has a chlorine content of at least 20.00 ppb by weight, wherein said chlorine content is present in the porous graphite substrate being 50 m or more below a surface of the porous graphite substrate.

14. A silicon carbide coated body used in a process chamber, comprising: a graphite substrate comprising pores having an average pore diameter of >10 m at a surface of the graphite substrate a surface; and a silicon carbide layer on a surface of the graphite substrate,, the silicon carbide layer extending into the pores relative to the surface.

15. The silicon carbide coated body used in a process chamber of claim 14, wherein the graphite substrate has a chlorine content of at least 20.00 ppb by weight, wherein said chlorine content is present in the graphite substrate being more than 50 m below an outer surface thereof.

16. The silicon carbide coated body used in a process chamber of claim 14, the graphite substrate having modified pores and unmodified pores, the modified pores having a diameter of two to eight times a diameter of the unmodified pores.

17. The silicon carbide coated body used in a process chamber of claim 14, wherein the graphite substrate a first average grain size is from about 0.015 mm to about 0.04 mm.

18. The silicon carbide coated body used in a process chamber of claim 14, wherein the graphite substrate has a density of 1.50 g/cm.sup.3 to 1.75 g/cm.sup.3.

19. The silicon carbide coated body used in a process chamber of claim 14, wherein the graphite substrate comprises one or more of the following elements in an amount of: calcium being less than 50.00 ppb by weight, magnesium being less than 50.00 ppb by weight, aluminum being less than 50.00 ppb by weight, titanium being less than 10.00 ppb by weight, chromium being less than 100.00 ppb by weight, manganese being less than 10.00 ppb by weight, copper being less than 50.00 ppb by weight, iron being less than 10.00 ppb by weight, cobalt being less than 10.00 ppb by weight, nickel being less than 10.00 ppb by weight, zinc being less than 50.00 ppb by weight, or molybdenum being less than 150.00 ppb by weight.

20. The silicon carbide coated body used in a process chamber of claim 15, wherein the silicon carbide layer is derived from dimethyldichlorosilane, and the silicon carbide layer comprises substantially tetrahedral crystalline silicon carbide tendrils having a length of at least 50 m.

Description

DESCRIPTION OF THE FIGURES AND THE REFERENCE SIGNS

[0509] 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

[0510] 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).

[0511] 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.

[0512] 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.

[0513] 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

[0514] 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

[0515] 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

[0516] 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

[0517] 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)

[0518] 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

[0519] 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

[0520] FIG. 9 illustrates the critical temperature dependency and its influence on SiC nucleation, growth and crystal formation in a CVD process

[0521] 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

[0522] FIG. 11 shows an XRD pattern of the improved SiC material of the present invention showing a very sharp B-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

TABLE-US-00001 (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

[0523] A porous graphite member was activated, purified and subjected to a chlorination treatment as described in the present invention.

[0524] The following chlorine content was measured in the chlorinated graphite member:

TABLE-US-00002 element graphite member Cl 0.06 ppm wt.

[0525] 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.

[0526] The chlorinated graphite member was used as a porous graphite substrate (1) in a CVD deposition method as described herein.

[0527] 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.

[0528] The SiC characteristics and quality described herein has been shown in FIGS. 10 and 11.

Example 2Influence of the Purge Gas

[0529] A silicon carbide coated body was prepared with the process of the present invention using H.sub.2 as the purge gas.

[0530] As a comparative Example, argon was used as purge gas.

[0531] 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

[0532] 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.

[0533] 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-00003 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

[0534] 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.

[0535] A further example, illustrating the SiC multilayer structure due to varying DMS amounts is shown in FIG. 2.

Example 4DMS Purity (Siloxanes)

[0536] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying siloxane impurities.

[0537] DMS with the following amounts of siloxane impurities were used:

TABLE-US-00004 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. %

[0538] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0539] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0540] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00005 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)

[0541] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying manganese impurities.

[0542] DMS with the following amounts of manganese impurities were used:

TABLE-US-00006 metal element DMS Sample A DMS Sample B DMS Sample C manganese (Mn) 2 ppb wt. 11 ppb wt. 150 ppb wt.

[0543] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0544] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0545] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00007 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)

[0546] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying copper impurities.

[0547] DMS with the following amounts of copper impurities were used:

TABLE-US-00008 metal element DMS Sample A DMS Sample B DMS Sample C copper (Cu) 1 ppb wt. 18 ppb wt. 41 ppb wt.

[0548] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0549] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0550] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00009 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

[0551] Example 7DMS Purity (Zn)

[0552] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying zinc impurities.

[0553] DMS with the following amounts of zinc impurities were used:

TABLE-US-00010 metal element DMS Sample A DMS Sample B DMS Sample C zinc (Zn) 1 ppb wt. 19 ppb wt. 42 ppb wt.

[0554] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0555] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0556] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00011 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

[0557] Example 8DMS Purity (Siloxane Plus Mn Plus Cu Plus Zn)

[0558] 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-00012 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