New optimization guidelines for sub-0.1 μm CMOS technologies with 2 nm NO gate oxynitrides

Abstract

This paper reports the issues and limitations in CMOSFET characteristics with 2 nm NO oxynitrides through investigation of the nitrogen concentration dependence on the device parameters. It is shown that threshold voltage (V/sub T/) spread rather than V/sub T/ shift is the restricting parameter which determines the minimum nitrogen concentration required in NO oxynitrides. Significant current drive reduction with increasing nitrogen concentration is observed in p-MOSFETs, and thus, compensation of penetrated boron by additional channel doping is beneficial to achieve high performance, since it pushes the minimum limitation of nitrogen concentration lower. For n-MOSFETs, it is shown that the reverse short-channel effect is suppressed in NO oxynitrides due to lower channel dopant redistribution, resulting in worse short-channel effects for high nitrogen concentrations. Accordingly, while the effective mobility under a high normal field is enhanced with increasing nitrogen concentration in n-MOSFETs, short-channel device degradation due to nitridation dominates I/sub on/ vs. I/sub off/ characteristics. Optimization of the I/sub on//I/sub off/ ratio for n-MOSFETs requires careful design of super halo profiles to control short-channel behaviour in oxynitrided devices.