SBIR-STTR Award

Absence of low defect density large diameter (~100mm) silicon carbide (SiC) wafers is a major barrier for the commercial production of SiC based devices. This phase I program is aimed at demonstrating a novel technique that will significantly reduce the mechanical stress in SiC during boule growth. In phase I, we will demonstrate that by the proposed method, a significant reduction in the mechnical stress is achieved in the growth of a 75 mm diameter 4H-SiC boule. Also, in Phase I, we will slice the boule into wafers, lap and polish the wafers, and provide comparison of mechanical stress between wafers produced by the proposed and conventional approaches. In Phase II, the technique will be refined to demonstrate the production of commercially viable 4H-n SiC boules, 100 mm in diameter, with a significant reduction in mechanical stress compared to those achieved by the conventional method.

Absence of low defect density large diameter (~100 mm) silicon carbide (SiC) wafers is a major barrier for the commercial production of SiC-based devices. Hence, the development of a process to produce large diameter bulk SiC boules with low defect density offers a significant impetus for the widespread commercialization of SiC-based devices. An approach that will simultaneously increase wafer diameter and decrease defect density is expected to result in SiC-based devices that are larger in diameter and devices with improved characteristics, performance, and yield. In the Phase I program, the feasibility of growing 75 mm diameter 4H-SiC boules with significant reduction in mechanical stress due to boule diameter expansion from smaller diameter seeds was convincingly demonstrated. The objective of the proposed Phase II program is to take the Phase I demonstration of this new approach "of minimizing the thermal stress during growth thtat involves boule diameter expansion" to the systematic development of a process to produce 4H-SiC wafers > 75 mm in diameter with low mechanical stress, in turn improving the material quality. Further, in Phase II, the growth process will be optimized for cost effectiveness, yield, and crystal quality, especially a significant improvement in polytype homogeneity, to develop a commercial product. Further, the wafers derived from boules will be characterized for micropipes and other defects.

Keywords:
Silicon Carbide, Sublimation, Rf Digitization, High Power Switching, Sic, Micropipes, Widebandwidthshighpowerelectronics