Poly-Si gate engineering for advanced CMOS transistors by germanium implantation H. Bourdon * , M. Juhel, B. Oudet, N. Breil, D. Lenoble STMicroelectronics, 850 Rue Jean Monnet, 38926 Crolles Cedex, France Available online 16 June 2005 Abstract Standard gate materials are compared to Ge implanted poly-Si and deposited poly-SiGe. It is demonstrated in this paper that the electrical resistance of the gate is significantly reduced via the use of poly-SiGe (from 30% to 40% decrease in resistance). Similarly, we show via specific optimization that localized Ge implantation is also suitable to reduce gate resistance. Physical characterizations are performed to determine the ‘‘root’’ causes at the origin of these improvements. In line with future publications showing strong benefits on CMOS device performance, grain size effects seem to be the main mechanisms explaining the measured improvement. Ó 2005 Elsevier B.V. All rights reserved. PACS: 61.72.Ss; 61.72.Tt Keywords: Ge co-implantation; CMOS gate; Poly-SiGe; Grain size; Sheet resistance 1. Introduction The doping depletion of poly-silicon gate at the dielectric interface is one of the major performance limitations in the standard advanced CMOS tran- sistors. Previous studies [1–3] have shown some performance improvement (electrical oxide thick- ness reduction and sheet resistance, R s , decrease) with poly-SiGe gates. In this study, we propose to evaluate the capability of germanium implanta- tion to modify the electrical behavior of poly- silicon gates. Bang et al. [4] worked on poly-SiGe with 25% and 50% of Ge. They show R s diminu- tion for boron implanted wafers increased with Ge concentration and R s augmentation for phos- phorus implantation. First, we study the electrical characteristic amelioration by using poly-Si (1y) Ge y (y < 25%) instead of poly-Si. The physical mechanisms responsible for this amelioration are determined. As poly-SiGe gate may induce some integration issues (gate etching, silicide formation, gate oxide integrity...), we have chosen to study 0168-583X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.04.090 * Corresponding author. Tel.: +33476926212. E-mail address: helene.bourdon@st.com (H. Bourdon). Nuclear Instruments and Methods in Physics Research B 237 (2005) 148–154 www.elsevier.com/locate/nimb