Source/Drain Engineering with Ge Large Angle Tilt Implantation and Pre-Amorphization to Improve Currrent Drive and Alleviate Floating Body Effects of Thin Film SOI MOSFETs

Abstract

This work presents an advanced salicide technology for thin film SiliconOn-Insulator (SOI) MOSFET s. Germanium large angle tilt implantation is applied to amorphize the silicon films prior to silicidation. This novel salicide technology greatly reduces the silicide formation energy and effectively controls the silicide depth. As a result, source/drain parasitic resistances are substantially reduced. In addition, due to the formation of a metal semiconductor barrier near the source/channel junction, the floating body effects are alleviated. fabricated using Ge pre-amorphization [1] [2]. A lower silicide formation thermal cycle is chosen so that the silicide is formed within the amorphous layer. The I-V characteristics of two different salicide processes with 0.3 μm effective channel lengths are shown in Fig. 1. Process flow for Ge pre-amorphization is also included. In addition to reducing source/drain resistance, Ge implantation improves the breakdown characteristics. Fig. 2 shows the measured breakdown voltage versus effective channel length for SOI devices with TSOI equal to 90 nm. Devices with Ge implantation increase the breakdown voltage by 0.3 V compared to devices without Ge implantation. In this work, a large angle Ge implantation was used to amorphize the silicon