FACTORS INFLUENCING THE THRESHOLD VOLTAGES OF METAL OXIDE CMOS DEVICES

摘要

Scaling MOSFETs to improve performance results in higher gate leakage as the silicon dioxide gate dielectric becomes thinner. Furthermore, polysilicon depletion becomes a significant portion of the gate capacitance and limits the scalability of the overall capacitance. To address these issues, there has been much interest in replacing the silicon dioxide with a higher permittivity dielectric and the polysilicon with a metal gate electrode. Unfortunately, new materials can cause significant threshold voltage shifts that are unacceptable for CMOS devices. In this paper, we review the factors influencing the threshold voltages and discuss options for addressing the threshold voltage shifts.