Mobility and current drive improvements associated with biaxial tensile stress in Si nand p-MOSFETs are briefly reviewed. Electron mobility enhancements at high channel doping (up to 6 x IO" cm-') 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,.,Ge, enables improved doping profile control, the diffusivity of the n-type dopants is dramatically enhanced in Sia.nGea.2.

Si–Ge interdiffusivity in epitaxial strained Si∕Si1−yGey/strained Si/relaxed Si1−x0Gex0 heterostructures is extracted for Ge fractions between 0 and 0.56 over the temperature range of 770–920°C. Boltzmann-Matano analysis is applied to determine interdiffusivity from diffused Ge profiles in strained Si/relaxed Si1−x0Gex0 heterostructures [L. Boltzmann, Wiedemanns Ann. Phys. 53, 959 (1894) and C. Matano, Jpn. J. Phys. 8, 109 (1933)]. A model for the interdiffusivity suitable for use in the process simulator TSUPREM-4 is constructed. Si–Ge interdiffusivity increases by 2.2 times for every 10% increase in Ge fraction for interdiffusion in strained Si/relaxed Si1−x0Gex0 samples. Significantly enhanced Si–Ge interdiffusion is observed for Si1−yGey layers under biaxial compressive strain. Si–Ge interdiffusivity is found to increase by 4.4 times for every 0.42% increase in the magnitude of biaxial compressive strain in the Si1−yGey, which is equivalent to a decrease in the Ge percentage in the substrate by 10at.%. These results are incorporated into an interdiffusion model that successfully predicts experimental interdiffusion in various SiGe heterostructures. The extracted activation energy and prefactor for the interdiffusivity are 4.66eV and 310cm2∕s, respectively, for the temperature and Ge fraction ranges of this study. Threading dislocation densities on the order of 107cm−2 are shown to have negligible effect on Si–Ge interdiffusion in Si∕Si0.69Ge0.31 structures. Substituting the strained Si layers surrounding the Si1−yGey peak layer with SiGe layers is shown to have little effect on the Si–Ge interdiffusivity. The implications of these findings for the design and process integration of enhanced mobility strained Si/strained SiGe metal-oxide-semiconductor field-effect transistors are discussed.

An interdiffusivity model was established for SiGe interdiffusion under tensile or relaxed strain over the full Ge content (xGe) range (0 ≤ xGe ≤ 1), which is based on the correlations between self-diffusivity, intrinsic diffusivity, and interdiffusivity. It unifies available interdiffusivity models over the full Ge range and applies to a wider temperature range up to 1270 °C at the xGe = 0 end and to 900 °C at the high xGe = 1 end. Interdiffusion experiments under soak and spike rapid thermal annealing conditions were conducted to verify the model. Literature interdiffusion data under furnace annealing conditions were also used for the same purpose. The interdiffusivity model of this work has been implemented in major process simulation tools, and the simulation results showed good agreement with experimental data under furnace annealing and soak and spike rapid thermal annealing conditions. This work demonstrated a new approach in studying SiGe interdiffusion, which has the advantage of studying interdiffusion under non-isothermal annealing conditions.

In this work, we reported uniform layer-by-layer sublimation of black phosphorus under heating below 600 K. The uniformity and crystallinity of BP samples after thermal thinning were confirmed by Raman spectra and 2D Raman imaging. A uniform and crystalline bilayer black phosphorus flake with an area of 180 µm 2 was prepared with this method. No micron scale defects were observed. The sublimation rate of BP was around 0.18 nm / min at 500 K and 1.5 nm / min at 550 K. Both room and high temperature Raman peak intensity ratio Si A 2 g as functions of BP thickness were established for in-situ thickness determination.The sublimation thinning method was shown to be a controllable and scalable approach to prepare few-layer black phosphorus.

The strain dependence of Si–Ge interdiffusion in epitaxial Si∕Si1−yGey∕Si heterostructures on relaxed Si1−xGex substrates has been studied using secondary ion mass spectrometry, Raman spectroscopy, and simulations. At 800 and 880 °C, significantly enhanced Si–Ge interdiffusion is observed in Si∕Si1−yGey∕Si heterostructures (y=0.56, 0.45, and 0.3) with Si1−yGey layers under compressive strain of −1%, compared to those under no strain. In contrast, tensile strain of 1% in Si0.70Ge0.30 layer has no observable effect on interdiffusion in Si∕Si0.70Ge0.30∕Si heterostructures. These results are relevant to the device and process design of high mobility dual channel and heterostructure-on-insulator metal oxide semiconductor field effect transistors.