Metal gate work function modulation by ion implantation for multiple threshold voltage FinFET devices

Abstract

FinFET has emerged as a device structure to enable the device scaling at and beyond the 22nm technology node due to increasingly stringent demands for maximum device speed, lower leakage current and control of random dopant fluctuation effects. High-k dielectric (Hik)/metal gate (MG) technology makes it feasible to obtain improved Effective Oxide Thickness (EOT) scaling and reduced leakage. Replacement metal gate (RMG) flows have been used for high performance logic volume production at and beyond 45nm node [1]. Precise threshold voltage (Vt) control and multiple Vt are required for FinFET device architectures for future devices. This paper proposes an ion implantation approach for modulating metal gate work function for both n-metal and p-metal gate used in a HiK last and replacement gate process. This approach offers simplified integration flow where no additional mask is needed and resist mask can be used. The effective work function (eWF) was measured along with the EOT and Gate Leakage (Jg). Stress Induced Leakage Current (SILC) method was used for testing HiK stack reliability. The results showed up to 200mV eWF modulation by ion implantation with fine control and without EOT and Jg degradation. The effect of implant species and dose on the eWF was studied in this paper. SIMS analysis of HKMG stack on the blanket wafer was used to determine the dopant distribution and explore the possible mechanism for metal gate work function modulation by ion implantation.