A SiGe strain layer for gettering Fe in SIMOX

Device processing introduces metallic contaminants that result in a reduction of device yields and reliability as well as higher gate oxide failure rates. Fortunately, these contaminants can be removed or neutralized at gettering sites associated with bulk oxygen precipitates and backside defects formed by a doped polysilicon layer. The problem with SIMOX, on the other hand, is the gettering sites are isolated by the buried oxide and additional metals can be introduced during O⁺ ion implantation and high temperature annealing. Here, we describe a new gettering process; the removal of metal contaminants from SIMOX using an MBE epitaxial SiGe alloy strain layer grown on a SIMOX silicon film. A SiGe alloy, with the desired germanium concentration and layer thickness, provides a highly strained region that acts as a sink(getter) for metals. With thermal cycling metals diffuse to or are driven into the surface strain layer for later removal. To demonstrate this effect and test the SiGe gettering strain layer effectiveness in SIMOX, we introduced a source of Fe⁵⁴ by implantation which is then diffused into the strain layer with an anneal. We analyzed the resulting material using TXRS (low angle surface reflection total X-ray fluorescence analysis), SIMS (Secondary Ion Mass Spectroscopy), and DLTS (Deep Level Transient Spectroscopy) measured on backgate on n-FET