The Role of Preamorphization and Activation for Ultra Shallow Junction Formation on Strained Si Layers Grown on SiGe Buf
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The Role of Preamorphization and Activation for Ultra Shallow Junction Formation on Strained Si Layers Grown on SiGe Buffer B.J. Pawlak1, W. Vandervorst2, R. Lindsay2, I. De Wolf2, F. Roozeboom3, R. Delhougne2, A. Benedetti2, R. Loo2, M. Caymax2, K. Maex2, N.E.B. Cowern4 1
Philips Research Leuven, Kapeldreef 75, 3001 Leuven, Belgium Tel.:+32.16281060, Fax.:+32.16.281214, email: [email protected] 2 IMEC, Kapeldreef 75, 3001 Leuven, Belgium 3 Philips Research Labs, WAG-p321, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands 4 Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH, UK INTRODUCTION In advanced CMOS technology nodes one may achieve further enhancement of device performance by carrier mobility modification in the transistor channel. The carrier mobility enhancement can be realized by formation of strained silicon layers on a Si1-xGex strain relaxed buffer. Formation of source and drain extensions on such structures need to satisfy one additional requirement, the formation process, including the activation related thermal budget should not relax the strain in the channel. In this paper we separately investigate the role of amorphization during implantation, different doping impurities and thermal budget on the junction and the transistor channel regions properties. Two approaches of dopant activation are discussed: low temperature solid phase epitaxial regrowth and high temperature conventional spike. EXPERIMENTAL DETAILS 8 nm strained silicon layers were epi-grown by chemical vapor deposition (CVD) on Strain Relaxed Si0.8Ge0.2 Buffer Layers (SRB). The SRB was grown as thick as 400 nm and included Crich layer to enable high relaxation condition and maximum stress induced in the top silicon layer. For the implantation the 8 inch n-type Si (100) wafers were used and implanted at the angle of 7° tilt and 27° twist. All implants were done on the Applied Materials XR80 LEAP. The Ge pre-amorphization condition varied between 4 and 20 keV for the standard dose of 1x1015 at./cm2. B was implanted at 0.5 keV with dose 7x1014 at./cm2 and 1.5 keV with dose 7x1014 at./cm2. A separate F implant was performed with energy 6 keV with the dose 1x1015 at./cm2. In such a way the F projected range could be positioned behind the B implant in the optimal place [1, 2]. N-type doping was done by As at energies between 1 and 10 keV, and doses from 5x10 14 up to 3x1015 at./cm2. Two P implants were performed: 2 keV, 5x1014 at./cm2 and 4 keV, 1.5x1015 at./cm2. Anneals were done on wafer pieces in the medium ramp-up and -down rate tool (Mattson SHS1000), for the solid phase epitaxial regrowth experiments (SPER). The fast ramp-up and down rate spike anneals were done on whole 8 inch wafers in an ASM LEVITOR tool [3]. The first one is the lamp based rapid thermal anneal (RTA) tool with the ramp-up rate around 40 °C/s and the ramp-down around 75 °C/s. The heat conduction in ASM LEVITOR was performed by helium gas, the ramp-up rate was 800 °C/s and the ramp-down around 100 °C/s.
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