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 body comprising at least two silicon carbide layers of different densities, comprising: A) positioning a porous graphite substrate having an open porosity in a process chamber; B) heating the porous graphite substrate in the process chamber to a temperature in a range of 1000 to 1200 C. under atmospheric pressure in a presence of a flow of H.sub.2 gas; C) depositing on the porous graphite substrate in a first deposition phase crystalline silicon carbide grains to form a silicon carbide coated graphite substrate by introducing a mixture of dimethyldichlorosilane and H.sub.2 into the process chamber with a first amount of dimethyldichlorosilane in the process chamber; D) increasing or reducing an amount of dimethyldichlorosilane in the process chamber and depositing in a second deposition phase crystalline silicon carbide grains on the silicon carbide coated graphite substrate by introducing a mixture of DMS and H.sub.2 into the process chamber with a second amount of dimethyldichlorosilane; E) optionally repeating step D) one or more times, thereby carrying out one or more additional steps of depositing, in one or more additional deposition phases, crystalline silicon carbide grains on the silicon carbide coated graphite substrate by introducing a mixture of dimethyldichlorosilane and H.sub.2 into the process chamber with one or more further amounts of dimethyldichlorosilane; and F) cooling the silicon carbide coated body resulting from step E).

2. The method of claim 1, further comprising prior to step C) the following step: B-2) introducing a mixture of dimethyldichlorosilane and H.sub.2 for at least 30 minutes into the process chamber and depositing an infusion phase crystalline silicon carbide grains in open pores of the porous graphite substrate by chemical vapor deposition and allow growing of the crystalline silicon carbide grains to silicon carbide crystals until a connected crystalline silicon carbide material in a form of silicon carbide tendrils extending with a length of at least 50 m into the porous graphite substrate is formed.

3. The method of claim 1, further comprising the following steps G) and H) following step F): G) changing a position of the silicon carbide coated body resulting from step F); and H) repeating step C) and optionally steps D) and E), thereby depositing crystalline silicon carbide grains on a surface of the porous graphite substrate resulting from step F) by chemical vapor deposition and allow growing of the crystalline silicon carbide grains to substantially tetrahedral silicon carbide crystals until one or more further silicon carbide layers are formed, followed by cooling the silicon carbide coated body resulting from step H).

4. The method of claim 3, wherein in step D) and in optional step E) the amount of dimethyldichlorosilane in the process chamber is gradually increased.

5. The method of claim 1, wherein in step D) the second amount of dimethyldichlorosilane in the process chamber is twice as much as the first amount of dimethyldichlorosilane in the process chamber in step C).

6. The method of claim 1, wherein in step E) a third deposition phase is carried out with a third amount of dimethyldichlorosilane in the process chamber, which is three times as much as the first amount of dimethyldichlorosilane in the process chamber in step C), and optionally a fourth deposition phase is carried out with a fourth amount of dimethyldichlorosilane in the process chamber, wherein the fourth amount of dimethyldichlorosilane is four times as much as the first amount of dimethyldichlorosilane in the process chamber in step C).

7. The method of claim 6, wherein the amounts of dimethyldichlorosilane in the process chamber are changed to effect formation of smaller silicon carbide crystals having smaller particle size by introducing a decreased amount of dimethyldichlorosilane into the process chamber and to effect formation of larger silicon carbide crystals having a larger particle size by introducing an increased amount of dimethyldichlorosilane into the process chamber.

8. The method of claim 1, wherein the porous graphite substrate of step A) has a porosity of greater than or equal to 6% and <15%, and comprises pores with a surface pore diameter of up to 30 m.

9. The method of claim 1, wherein during the depositing on the porous graphite substrate in a first deposition phase crystalline silicon carbide grains by introducing a mixture of dimethyldichlorosilane and H.sub.2 into the process chamber with a first amount of dimethyldichlorosilane in the process chamber, the dimethyldichlorosilane including as an impurity therein siloxane in an amount of >0 to 2.00 wt. %.

10. The method of claim 2, wherein the connected crystalline silicon carbide material in a form of silicon carbide tendrils extending with a length of at least 75 m is formed in step B-2.

11. The method of claim 2, wherein the depositing an infusion phase crystalline silicon carbide grains of step B-2) is carried out until an interfacial layer of silicon carbide having a thickness of at least 50 m is formed and the interfacial layer of silicon carbide extends inwardly of pores of the porous graphite substrate, wherein the interfacial layer of silicon carbide is located between the porous graphite substrate and silicon carbide surface layer formed in steps C) to E) and step H).

12. The method of claim 2, wherein the connected crystalline silicon carbide material in a form of silicon carbide tendrils extending with a length of 75 to 150 m is formed.

13. A silicon carbide coated body comprising: a porous graphite substrate having a porosity of 6% to 15% and pores with a diameter, where a pore opens at a surface of the porous graphite substrate, of 10 to 30 m; and at least two silicon carbide layers of different densities from one another covering the porous graphite substrate.

14. The silicon carbide coated body of claim 13, further comprising interfacial layer located between the porous graphite substrate and the at least two silicon carbide layers, the interfacial layer comprising pores of the porous graphite substrate including therein tightly connected substantially tetrahedral crystalline silicon carbide material in a form of silicon carbide tendrils extending a length of at least 50 m from a first silicon carbide layer of the at least two silicon carbide layers and into the porous graphite substrate.

15. The silicon carbide coated body of claim 13, wherein the at least two silicon carbide layers comprise silicon carbide crystals, and sizes of the silicon carbide crystals in the at least two silicon carbide layers are different from each other.

16. The silicon carbide coated body of claim 14, wherein the silicon carbide tendrils extend integrally from the first silicon carbide layer of the at least two silicon carbide layers covering the porous graphite substrate.

17. A component of a semiconductor processing chamber, comprising: a silicon carbide coated body comprising a porous graphite substrate having a porosity of 6% to 15% and pores with a diameter, where a pore opens at a surface of the porous graphite substrate, 10 to 30 m; and at least two silicon carbide layers of different densities from one another covering the porous graphite substrate.

18. The component of a semiconductor processing chamber of claim 17, further comprising interfacial layer located between the porous graphite substrate and the at least two silicon carbide layers, the interfacial layer comprising pores of the porous graphite substrate including therein tightly connected substantially tetrahedral crystalline silicon carbide material in a form of silicon carbide tendrils extending a length of at least 50 m from a first silicon carbide layer of the at least two silicon carbide layers and into the porous graphite substrate.

19. The component of a semiconductor processing chamber of claim 18, wherein the silicon carbide tendrils extend integrally from the first silicon carbide layer of the at least two silicon carbide layers covering the porous graphite substrate.

20. The component of a semiconductor processing chamber of claim 17, wherein the at least two silicon carbide layers comprise silicon carbide crystals, and sizes of the silicon carbide crystals in the at least two silicon carbide layers are different from each other.

Description

DESCRIPTION OF THE FIGURES AND THE REFERENCE SIGNS

[0484] 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

[0485] 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).

[0486] 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.

[0487] 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.

[0488] 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

[0489] 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

[0490] 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

[0491] 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

[0492] 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)

[0493] 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

[0494] 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

[0495] FIG. 9 illustrates the critical temperature dependency and its influence on SiC nucleation, growth and crystal formation in a CVD process

[0496] 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

[0497] FIG. 11 shows an XRD pattern of the improved SiC material of the present invention showing a very sharp -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

[0498] (1) porous graphite substrate

[0499] (2) SiC coating layer

[0500] (2-A), (2-B), (2-C) SiC coating layers of different density

[0501] (3) interfacial layer with

[0502] (4) tendrils formed in open pores

[0503] (5) SiC coating on the inner walls of open pores

[0504] (6) open pores in the graphite substrate

[0505] (7) tight connection between tendrils and coating layer

[0506] (8) tetrahedral crystals

VI. EXAMPLES

Example 1

Activation and Chlorination of a Graphite Member and Tendril Formation

[0507] A porous graphite member was activated, purified and subjected to a chlorination treatment as described in the present invention.

[0508] The following chlorine content was measured in the chlorinated graphite member:

TABLE-US-00005 element graphite member Cl 0.06 ppm wt.

[0509] 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.

[0510] The chlorinated graphite member was used as a porous graphite substrate (1) in a CVD deposition method as described herein.

[0511] 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.

[0512] The SiC characteristics and quality described herein has been shown in FIGS. 10 and 11.

Example 2

Influence of the Purge Gas

[0513] A silicon carbide coated body was prepared with the process of the present invention using H.sub.2 as the purge gas.

[0514] As a comparative Example, argon was used as purge gas.

[0515] As becomes apparent from FIGS. 1 and 4, the use of argon does not lead to the formation of tendrils (4).

Example 3

Multilayer SiC-Coating

[0516] 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.

[0517] 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-00006 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

[0518] 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.

[0519] A further example, illustrating the SiC multilayer structure due to varying DMS amounts is shown in FIG. 2.

Example 4

DMS Purity (Siloxanes)

[0520] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying siloxane impurities.

[0521] DMS with the following amounts of siloxane impurities were used:

TABLE-US-00007 DMS DMS DMS Siloxane compound Sample A Sample B 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 octamethyl- 0.112 wt. % 0.157 wt. % 0.156 wt. % cyclotetrasiloxane 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. %

[0522] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0523] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0524] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00008 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 5

DMS Purity (Mn)

[0525] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying manganese impurities.

[0526] DMS with the following amounts of manganese impurities were used:

TABLE-US-00009 metal element DMS Sample A DMS Sample B DMS Sample C manganese (Mn) 2 ppb wt. 11 ppb wt. 150 ppb wt.

[0527] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0528] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0529] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00010 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 6

DMS Purity (Cu)

[0530] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying copper impurities.

[0531] DMS with the following amounts of copper impurities were used:

TABLE-US-00011 metal element DMS Sample A DMS Sample B DMS Sample C copper (Cu) 1 ppb wt. 18 ppb wt. 41 ppb wt.

[0532] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0533] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0534] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00012 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 7

DMS Purity (Zn)

[0535] A silicon carbide coated body was prepared with the process of the present invention with DMS of varying zinc impurities.

[0536] DMS with the following amounts of zinc impurities were used:

TABLE-US-00013 metal element DMS Sample A DMS Sample B DMS Sample C zinc (Zn) 1 ppb wt. 19 ppb wt. 42 ppb wt.

[0537] With DMS according to sample A and B the formation of SiC tendrils occurred according to the present invention.

[0538] With DMS according to sample C no sufficient formation of SiC tendrils occurred.

[0539] Further, the following ranges were found as effective with respect to the desired tendril formation:

TABLE-US-00014 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 8

DMS Purity (Siloxane Plus Mn Plus Cu Plus Zn)

[0540] 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-00015 Total Total Siloxane 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 40 to 150 30 to <50 30 to <50 + wt. % ppb wt. ppb wt. 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