Demonstration of a high‐performance SiGe alloy channel considering Ge fraction, D it and BTB leakage

Abstract

The electrical properties of a SiGe alloy channel from Si to Ge, for electron and hole mobilities are investigated. Although SiGe NMOS shows degraded electron mobility until 85% because of alloy scattering, abrupt mobility improvement with the high composition SiGe channel is observed because of a band structure modification. A linearly improved hole mobility with Ge and channel strain increase was also observed. Focusing on PMOS, on-current gain matching off-current target shows slightly different behavior. Even if the effective current improvement due to strain is similar with that of mobility, the Ge concentration effect is much smaller because of band-to-band leakage degradation. In case of strain, relatively smaller band offset compared to the Ge mole fraction is evaluated by simulation. Finally, when measured hardware is compared between Ge 30, 40 and 50%, the highest SiGe alloy channel shows the lowest effective current. As Ge concentration increase, degraded sub-threshold swing and capacitance reduction which come from high inter-face trap, negative Vth shift and band-to-band leakage via the conduction band offset is observed. In conclusion, sustaining the high strain at channel and low D it are critical in the development of high-performance, high concentration SiGe alloy PMOS.