Enhanced Antimony Activation for Ultra-Shallow Junctions in Strained Silicon
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0912-C02-03
Enhanced Antimony Activation for Ultra-Shallow Junctions in Strained Silicon N. S. Bennett1, A. J. Smith1, C. S. Beer2, L. O'Reilly3, B. Colombeau4, G. D. Dilliway5, R. Harper6, P. J. McNally3, R. Gwilliam1, N. E. B. Cowern1, and B. J. Sealy1 1 Advanced Technology Institute, University of Surrey, Guildford, United Kingdom 2 Dept. of Physics, University of Warwick, Coventry, United Kingdom 3 School of Electronic Engineering, Dublin City University, Dublin, Ireland 4 Chartered Semiconductor Manufacturing Ltd., 60 Woodlands, Singapore 5 IMEC, Leuven, Belgium 6 IQE Silicon Compounds Ltd., Cardiff, United Kingdom ABSTRACT Sheet resistance (Rs) reductions are presented for antimony and arsenic doped layers produced in strained Si. Results re-emphasise the Rs reduction for As comes purely as a result of mobility improvement [1,2] whereas for Sb, a superior lowering is observed from improvements in both mobility and activation. For the first time, strain is shown to enhance the activation of dopant atoms whilst Sb is seen to create stable ultra-shallow junctions. Our results propose Sb as a viable alternative to As for the creation of highly activated, low resistance ultra-shallow junctions for use with strain-engineered CMOS devices.
INTRODUCTION To fulfil industry’s drive for ever-increasing CMOS performance the use of strain engineering is now an inevitable approach to device improvement [3]. The capability of strain to bring mobility enhancement to the channel is now empirical fact, however the extent to which strain engineering can be successfully combined with conventional doping of ultra-shallow source/drain regions will depend on the effects of strain on dopant activation at high concentrations. Arsenic is the favoured n-type dopant species in conventional Si and scientific literature discussing As implants in bulk- and strained-Si layers have shown a reduction in sheet resistance in the strained material. This appears to be a direct result of mobility enhancement, with no evidence to date for any improvement in activation [1,2]. Because of its greater mass Sb is considered a feasible alternative to As due to improvements in junction depth and abruptness. Similarly, we have previously shown Sb to be highly activated following low-temperature thermal processing with complete dopant stability for temperatures
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