2.3.2.1 Commercially Available Wafers

After years of development of the sublimation growth process, Cree, Inc. became the first company to sell 25 mm diameter semiconductor wafers of 4H-SiC in 1989 [51]. Only with the development of the modified Lely seeded sublimation growth technique acceptably large and reproducible single-crystal SiC wafers of usable electrical quality have become available. Correspondingly, the vast majority of silicon carbide semiconductor electronics development has taken place since 1990. The preeminence of SiC as a wide bandgap substrate material has led to the emergence of a number of substrate suppliers.

In terms of market share, currently the dominant source is Cree, Inc., which offers 3 inch 4H and 6H wafers. 3 inch 6H along with 2 inch 6H and 4H wafers can be obtained from multiple suppliers. N-type, p-type, and semi-insulating SiC wafers are commercially available at different prices. Wafer size, cost, and quality are all very critical to the manufacturability and process yield of mass-produced semiconductor microelectronics. Compared to commonplace silicon and GaAs wafer standards, present-day 4H- and 6H-SiC wafers are still small, expensive, and of relatively inferior quality. In addition to high densities of crystalline defects such as micropipes and closed-core screw dislocations discussed in Subsection 2.3.2.2, commercial SiC wafers also exhibit significantly rougher surfaces, and larger warpage and bow than is typical for silicon and GaAs wafers[52]. This disparity is not surprising considering that silicon and GaAs wafers have undergone several decades of commercial process refinement, and that SiC is an extraordinarily hard material making it very difficult to properly saw and polish. Nevertheless, on-going wafer sawing and polishing process improvements should eventually alleviate wafer surface quality deficiencies.

T. Ayalew: SiC Semiconductor Devices Technology, Modeling, and Simulation