3× hole mobility enhancement in epitaxially grown SiGe PMOSFETs on (110) Si substrates with high k/metal gate for hybrid orientation technology

摘要

Demonstration of a 3× enhancement in hole mobility, in comparison to the universal Si/SiO{sub}2 curve, is reported for epitaxially grown SiGe layers on (110) silicon substrates. This channel material is targeted for applications in high performance MOSFETs in a hybrid orientation technology using the (110) surface for PMOS devices. It may be envisioned that using epitaxial SiGe, while retaining the Si-like band structure at mole fractions below ～80% Ge, and using the (110) crystal surface could provide enhancements over and above the benefits accrued due to the use of Si (110) layers alone. Prior results using Si{sub}0.7Ge{sub}0.3 indicate an enhancement of about 75% over universal Si, with a peak mobility of 210 cm{sup}2/V-s. In this report, we demonstrate a higher Ge mole fraction (Si{sub}0.4Ge{sub}0.6) grown on a (110) Si wafer using a dislocation blocking technique and achieve a peak hole mobility of 340 cm{sup}2/V-s which is an enhancement of 3× over the universal Si/SiO{sub}2 hole mobility. Consistent with other reports in the literature, a much lower epitaxial growth rate on the (110) surface was observed. Both strained and relaxed SiGe films have been fabricated on (110) Si wafers as observed from X Ray Diffraction data and the epitaxial growth process is currently under further optimization. Raman spectroscopy using a blue laser was used to confirm the presence of Si-Si and Si-Ge phonon peaks from the SiGe/strained Si cap layer grown on (110) Si.