Investigation of SiGeB Epitaxy on Different Film Substrates

Abstract

Selective epitaxial embedded SiGe(B) (e-SiGe) is widely used for Source/Drain in advanced CMOS technologies for introducing compressive strain to the PMOS channel which improves the hole mobility. In this paper, we investigated SiGeB epitaxy on different substrates including SiGe, Si:B, SiGeB and also dielectric films including ALD/ CVD SiN, thermal/CVD SiO2. For SiGeB epitaxy on crystallized film substrates, results show that Germanium would prevent Boron inter-diffusion between the substrate and the following deposited SiGeB. Growth Rate (GR) of the epitaxy eSiGe film is also investigated. A combination of the SiGeB film concentration and GR study shows that Boron concentration and strain introduced by lattice mismatch between the substrate and the epitaxial film are two competitive factors to the GR. The film grows faster when Boron concentration is higher while larger strain would degrade the GR. Selectivity study shows that CVD SiN film have the best selectivity. We also investigated the film selectivity before and after thermal anneal. Results show that film selectivity become worse after thermal anneal. IntroductionWith continuous scaling down trend in semiconductor devices, stress technology was introduced in CMOS transistor process to boost device performance. While performance of n-MOS was improved by applying SMT, CESL process to introduce tensile stress in the channel region, selective Embedded SiGeB S/D[1] was introduced for improving the recent short channel p-MOS performance since the induced compressive strain within the channel area enhance hole mobility. The compressive strain comes from both lattice and thermal mismatch between epitaxial SiGe(B) and Si substrates. Thus, it is necessary to understand the growth mechanism of epitaxy SiGeB on different substrates. On the other side, selectivity of SiGeB epitaxy on different dielectric films is critical for a robust process control. Non-selectivity process would result in defects then decrease the device yield.In this paper, we investigated SiGeB epitaxy on different substrates including SiGe, Si:B, SiGeB substrates and also dielectric films including ALD/ CVD Si 3 N 4 , thermal/CVD SiO 2 . For SiGeB epitaxy on crystallized film substrates, Germanium and Boron concentration of the film were performed by Secondary Ion Mass Spectrum (SIMS). It shows that Germanium would prevent Boron inter-diffusion between the substrate and the following deposited SiGeB. Growth Rate (GR) of the epitaxy e-SiGe film is also investigated. A combination of the SiGeB film concentration and GR study