Mobility and performance enhancement in compressively strained SiGe channel PMOSFETs

Abstract We report that drive current enhancement and higher mobilities than the universal mobility in compressively strained Si1−xGex on Si surface-channel p-type metal-oxide–semiconductor field-effect-transistors (PMOSFETs) with HfO2 gate dielectric, for gate lengths (LG) down to 180 nm. 36% drive current enhancement was achieved for Si0.8Ge0.2 channel PMOSFETs compared to Si with HfO2 gate dielectric. We demonstrate that using SiGe in the channel may be one way to recover the mobility degradation due to the use of HfO2. Buried-channel PMOSFETs with a Si cap layer and SiO2 gate dielectrics were also studied. 41% peak mobility enhancement in Si1−xGex channel PMOSFETs was observed compared to Si channel PMOSFETs. 17% drive current enhancement was achieved for 70 nm channel length (LG) Si0.9Ge0.1 PMOSFETs with SiO2 gate dielectric. This shows the impact of increased hole mobility even for ultra-small geometry of MOSFETs and modest Ge mole fractions. Comparable short channel effects (SCE) were achieved for the buried-channel Si1−xGex devices with LG=70 nm, by controlling Si cap thickness, compared to the Si channel devices. Drive current enhancement without significant SCE and leakage current degradation was observed in this work.