Pure CVD silicon carbide wafer carriers

Paul Boughton

Morgan Technical Ceramics (MTC) has launched pure chemical vapour deposition silicon carbide (CVD SiC) wafer carriers for high temperature metal organic chemical vapour deposition (MOCVD) processing.

Pure CVD SiC wafer carriers enable manufacturers of high brightness light emitting diodes (LEDs) using gallium nitride (GaN) deposition to significantly increase their yield and to meet the growing industry demand for LEDs.

The pure CVD SiC wafer carriers significantly outperform traditional wafer carriers used in this process, which are graphite and coated with a layer of CVD SiC.  These coated graphite-based carriers cannot withstand the high temperatures (1100 to 1200 degrees 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 causing the coated wafer carrier to be replaced. 

The CVD SiC is 99.999+ percent pure and has high thermal conductivity and thermal shock resistance.  As a result it can withstand the high temperatures and harsh environment found in high brightness LED manufacture.  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 17 inches in diameter and can hold up to 40 2-4 inch wafers.

The pure CVD SiC wafer carriers transmit heat efficiently, with a very high thermal conductivity.  For example, CVD SiC has a thermal conductivity of 250-300 watts per metre kelvin.  By comparison, sintered SiC’s thermal conductivity is 100-140 watts per meter kelvin and pure graphite is typically only 85 watts per meter kelvin.  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 production yields, compared to coated graphite wafer carriers. 

In addition, the pure monolithic SiC has a long life.  It resists warpage and only needs to be replaced when the carrier is broken, chipped, or damaged due to handling.  This will provide opportunities for cost savings for semiconductor manufacturers.
For more information, viit www.morgantechnicalceramics.com