Strained silicon MOSFET technology

Mobility and current drive improvements associated with biaxial tensile stress in Si n- and p-MOSFETs are briefly reviewed. Electron mobility enhancements at high channel doping (up to 6 /spl times/ 10/sup 18/ cm/sup -3/) are characterized in strained Si n-MOSFETs. For low inversion layer carrier concentrations, channel-dopant ionized impurity scattering does reduce the strain-induced mobility enhancement, but the enhancement is recovered at higher inversion charge concentrations, where screening is efficient. Mobility enhancement in strained Si p-MOSFETs is also discussed. There are process integration challenges and opportunities associated with this technology. Dopant diffusion, and its impact on profile engineering in strained Si CMOS structures, is one example. While the slower diffusion of B in Si/sub 1-x/Ge/sub x/ enables improved doping profile control, the diffusivity of the n-type dopants is dramatically enhanced in Si/sub 0.8/Ge/sub 0.2/.