5-4-1 Historical Lack of SiC Wafers

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. Prior to 1980, experimental

SiC electronic devices were confined to small (typically ~1 ), irregularly shaped SiC crystal platelets

grown as a byproduct of the Acheson process for manufacturing industrial abrasives (e.g., sandpaper)

or by the Lely process . In the Lely process, SiC sublimed from polycrystalline SiC powder at

temperatures near 2500°C are randomly condensed on the walls of a cavity forming small, hexagonally

shaped platelets. While these small, nonreproducible 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.