CO2 laser annealing of low-hole-concentration polycrystalline germanium for the fabrication of enhancement-mode nMOSFET

Abstract

A p-type polycrystalline Ge (poly-Ge) film processed by UV and CO2 laser annealing reduces the hole concentration from 6 x 10(18) to 2 x 10(16) cm(-3), accompanied by poly-grain growth. The decrease in hole concentration arises from the defect annealing using a CO2 laser, as demonstrated by the changes in the work function, that is, the valence-band maximum (VBM). The laser processes reduce the thermal budget for the fabrication of an enhancement-mode poly-Ge nMOSFET, which has a l(on)/l(off) ratio of 5 x 10(3), a Vth of 2V, and a subthreshold swing of 250 mV/dec., and will be potential fabrication methods for monolithic 3D integrated circuits in the future. (C) 2018 The Japan Society of Applied Physics