A variety of backside damage techniques are available for gettering heavy-metal contaminants in silicon wafers. These include mechanical damage, ion implantation, thin film deposition, and pulsed–laser surface melting. In each case, strain fields and microscopic defects induced by the processing trap impurities as they diffuse through the wafer during subsequent high–temperature processing steps. We examine the defect structures produced by CW laser gettering, describe the dependence of gettering efficiency on wafer oxygen content and processing conditions, and demonstrate that CW laser processing can be an effective gettering technique even when the number of laser scan lines is reduced to make wafer processing acceptably rapid.
Expitaxial Ge/GaAs heterostructures have been produced by scanned cw argon laser annealing of 440-nm-thick amorphous Ge films on (100) semi-insulating GaAs substrates. Depending on the incident laser power and scan rate, two modes of film regrowth were observed. At low powers (between ∼1.6 and 4.0 W for a beam diameter of ∼40μm) and scan rates between 1 and 400 cm/sec, polycrystalline Ge with a (100) preferred orientation was formed by an ’’explosive’’ crystallization mechanism. At higher powers, and over a scan rate range of 20–400 cm/sec, single-crystal films containing some dissolved GaAs in solution were obtained by liquid phase regrowth. Typical film resistivities ρ were as follows: as-deposited, ρ = 180 Ω cm; polycrystalline films, ρ = 3×10−2 cm; single-crystal films, ρ = 9×10−4Ω cm.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.