2.3.2 Sublimation Growth of Wafers

In the late 1970s, Tairov and Tzvetkov established the basic principles of a modified seeded sublimation growth process for growth of 6H-SiC [49,7]. This process, also referred to as the modified Lely process, was a breakthrough for SiC in that it offered the first possibility of reproducibly growing acceptably large single-crystals of SiC that could be cut and polished into mass-produced SiC wafers. The basic growth process is based on heating polycrystalline SiC source material to $\sim$2400$~^{\circ}$C under conditions where it sublimes into the vapor phase and subsequently condenses onto a cooler SiC seed crystal. This produces a somewhat cylindrical boule of single-crystal SiC that grows taller at a rate of a few millimeters per hour. To date, the preferred orientation of the growth in the sublimation process is such that vertical growth of a taller cylindrical boule proceeds along the [0001] crystallographic c-axis direction (vertical direction in Fig. 2.3). Circular c-axis wafers with surfaces that lie normal (perpendicular) to the c-axis can be sawed from the roughly cylindrical boule. While other growth orientations (such as growth along the a-axis) continue to be investigated, the electronic quality of these material has been proven inferior to c-axis grown wafers [50].

Subsections

• 2.3.2.1 Commercially Available Wafers
• 2.3.2.2 Wafer Crystal Defects

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