Blistering kinetics in H-implanted 4H-SiC for large-area exfoliation

Abstract

Layer transfer of single-crystalline SiC based on layer splitting and wafer bonding on an alternate substrate is a viable approach to fabricate SiC power devices at a lower cost. Dependence of implantation-induced surface blistering and exfoliation of thin layers, on the implantation parameters and subsequent annealing conditions, for large area exfoliation of 4H-SiC have been studied. We report the optimization of the annealing process (one-step or two-step) and annealing parameters like temperature and time to achieve large area exfoliation of SiC. Using the Föppl-von Karman (FvK) theory, the pressure inside the blister cavities and implantation-induced stress inside the damage region have been studied. We deduce that pressure inside the blister depends primarily on the blister size. HRXRD analysis has been used to determine the strain relaxation behavior as a function of annealing conditions. Raman spectroscopy and STEM measurements revealed the formation of defects inside the material due to ion implantation. AFM, Nomarski, and SEM were used to measure the size and depth details of the blisters as a function of annealing temperature and time. We have successfully exfoliated large area (up to 500 μm) in a two-step annealing process. The results reported in this paper are useful for SiC layer transfer on an arbitrary substrate by the Smart Cut process.