Effective mobilities in pseudomorphic Si/SiGe/Si p-channel metal-oxide-semiconductor field-effect transistors with thin silicon capping layers

Si/Si(0.64)Ge(0.36)/Si pMOSFETs with Enhanced Voltage Gain and Low 1/f Noise

“…An increase of germanium content is accompanied by increased strain and the requirement for lower thermal budgets. Thinning of the Si cap has been associated with a poor quality oxide interface due to the segregation and diffusion of germanium into the Si cap during growth and processing [1]. It is encouraging that the requirements for low noise and high transconductance are the same, but these concerns must be addressed if further improvements in device performance are to be realised.…”

“…Equation 1 can be directly applied to the 2nm cap heterostructure, because all the mobile charge is retained in the alloy layer with no parallel conduction in the Si cap for carrier sheet densities < 10 13 [1].…”

“…Full details are given in a previous paper [1] but are summarised here. Oxide growth was by dry thermal oxidation at 800 o C with a final oxide thickness of 9.5nm±0.5nm.…”

Strained-SiGe Complementary MOSFETs Adopting Different Thickness of Silicon Cap Layers for Low Power and High Performance Applications

“…This improvement may be explained by two main reasons. One reason is due to the hole confinement in the Si 0.8 Ge 0.2 buried channel, which separates the channel charge from the oxide traps at the gate oxide surface [17]. Since the probability of direct tunneling is known to be low even at a 1 nm thick unconsumed Si-cap thickness [14], the 3 nm thick Si cap is sufficient to prevent the direct tunneling to the oxide traps.…”

Design and optimization of a buried channel PMOS integrable in a Si1−xGex BiCMOS process

“…Secondly, as the buried channel moves closer to Table 1 Effect of Ge content on hole confinement Ge fraction (%) SiGe thickness (nm) V co (V) V TO (V) V hc (V) 15 20 the interface, surface roughness scattering for holes in Si 1Àx Ge x channel increases, and the benefit of mobility enhancement due to strain may diminish. It has been shown that the peak mobility in the buried Si 1Àx Ge x channel increases as the cap thickness is increased [31]. Interface roughness scattering is less in devices with thicker cap layers, not only because of increased distance from the interface, but also because the lower amplitude of the Ge segregation tail at the Si-SiO 2 boundary leads to a smoother interface.…”