Morgan Technical Ceramics’ Offers Pure CVD Silicon Carbide Wafer Carriers
Oct 27, 2009 Morgan Technical Ceramics (MTC) business has introduced its chemical vapor deposition silicon carbide (CVD SiC) wafer carriers for high temperature metal organic chemical vapor deposition (MOCVD) processing. The pure CVD SiC wafer carriers significantly increase the yield for manufacturers of high brightness light emitting diodes (LEDs) using gallium nitride (GaN) deposition.
The CVD SiC is 99.999+ percent pure, and exhibits high thermal conductivity and thermal shock resistance. It is a solid monolithic material that achieves theoretical density, generating minimal particulates and exhibiting very high corrosion and erosion resistance. The material can vary opacity and electrical conductivity without introduction of metallic impurities. The wafer carriers are typically about 17 inches in diameter, holding up to 40 2 to 4-inch wafers.
MTC pure CVD SiC wafer carriers significantly outperform traditional GaN wafer carriers, which are made of graphite, and then coated with a layer of CVD SiC. These coated graphite-based carriers cannot stand up to the high temperatures (1,100°C to 1,200°C) required in GaN deposition for today’s high brightness blue and white LEDs. The high temperatures cause the coating to develop tiny pinholes through which process chemicals can attack the underlying graphite. Graphite particles can then flake off and contaminate the GaN. A typical coated graphite wafer carrier may have to be replaced as often as monthly, depending on usage conditions.
The pure CVD SiC wafer carriers transmit heat efficiently, with a very high thermal conductivity. For example, CVD SiC has a thermal conductivity of 250 to 300 watts per meter kelvin (W m-1 K-1). By comparison, sintered SiC’s thermal conductivity is about 100 to 140 W m-1 K-1 and pure graphite is only about 85 W m-1 K-1. CVD SiC’s higher thermal conductivity results in a uniform temperature across the wafer’s entire diameter, improving the GaN deposition process, and significantly increasing the yield of the target wavelength of LEDs compared to coated graphite wafer carriers.
In addition to the increased LED yields with the use of the pure CVD SiC wafer carriers, the pure monolithic SiC is very long-lived, resists warpage, and only needs to be replaced when the carrier is broken, chipped, or damaged due to handling. This can result in real cost savings for semiconductor manufacturers.
Author: Ray Andersson
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