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Patents of Silicon Carbide

Despite a cumulative raw wafers + epi wafers market that won't exceed $80M in 2012, the corpus of related patents comprises over 1772 patent families and more than 350 companies since 1928. 83% of patents represent a method while 17% of them claim an apparatus.  

Since 1978 the main technique to grow bulk single-crystals of silicon carbide is PVT: Physical Vapor Transport (seeded sublimation method) which represents 36% of published patents. This PVT technique mostly deals with the hexagonal polytype nH-SiC (n=2,4,6). Liquid Phase Epitaxy (LPE) is an alternative route to grow SiC (early efforts date back to 1961). It allows crystals to grow with low dislocation densities and at relatively low temperatures (attractive for cubic polytype 3C-SiC).  

About 37% of patents claim a Chemical Vapor Deposition technique (CVD) which is almost exclusively used today to manufacture SiC epiwafer. The Molecular Beam Epitaxy (MBE) is only mentioned within 1% of patents. The polytype (hexagonal or cubic) is explicitly claimed in 15% of patents. Numerous strategies to reduce crystal defects (micropipes, carrots .) and make semi-insulating material are proposed in 23% and 10% of patents respectively  


About 350 applicants are involved in SiC crystal/epiwafer technology. They are mainly located in Japan (72% of patents) and USA (12% of patents). The five major applicants based on their patents number are Denso, Sumitomo, Nippon Steel, Bridgestone and Toyota. They represent about 35% of studied patents. The first US firm Cree Inc. occupies the 6th position. This balance is totally uncorrelated from the reality of the market where 75% of the SiC wafer business is generated by US-based companies, namely CREE, II-VI or Dow Corning. Japan is only responsible for 5% of the revenues (at least before SiCrystal Acquisition by Rohm). Same observations are seen in Europe and Asia (out of Japan) where the [# of patents/revenues] ratio is very weak at the moment.  


Japan is increasingly involved in SiC technology since the 1980's. United States was the early player and still is active. In contrast, only 3 Japanese companies are commercially active in SiC material: Showa Denko (epiwafer), Bridgestone (wafer) and Nippon Steel (wafer and epiwafer).  
China and Korea emerged as new players during the last five years along with the establishment of companies such as PAM-XIAMEN(CN), SKC (KR).However, these companies market shares remain very low at the moment.  

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