2.3.1 Historical Lack of Wafers

Most of silicon carbide's superior intrinsic electrical properties have been known for decades. At the genesis of the semiconductor electronics era, SiC was considered an early transistor material candidate along with germanium and silicon. However, reproducible wafers of reasonable consistency, size, quality, and availability are a prerequisite for commercial mass-production of semiconductor electronics. Many semiconductor materials can be melted and reproducibly recrystallized into large single-crystals with the aid of a seed crystal, such as in the Czochralski method employed in the manufacture of almost all silicon wafers, enabling reasonably large wafers to be mass-produced. However, because SiC sublimes instead of melting at reasonably attainable pressures, SiC cannot be grown by conventional melt-growth techniques. This prevented the realization of SiC crystals suitable for mass production until the late 1980s. Prior to 1980, experimental SiC electronic devices were confined to small (typically $\sim$1 cm$^2$), irregularly shaped SiC crystal platelets grown as a by-product of the Acheson process for manufacturing industrial abrasives (e.g., sandpaper) [3] or by the Lely process [5]. In the Lely process, SiC sublimed from polycrystalline SiC powder at temperatures near 2500$~^{\circ}$C are randomly condensed on the walls of a cavity forming small-hexagonally shaped platelets. While these small, non-reproducible crystals permitted some basic SiC electronics research, they were clearly not suitable for semiconductor mass production. As such, silicon became the dominant semiconductor fueling the solid-state technology revolution, while interest in SiC-based microelectronics was limited.

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