HIGH PERFORMANCE, HIGHLY RELIABLE GATE OXIDE FORMED WITH RAPID THERMAL OXIDATION IN-SITU STEAM GENERATION (ISSG) TECHNIQUE

摘要

Gate dielectric thickness in the range of 20 A is needed for devices with an operating voltage of 1.2 V (0.12 μm technology node). The main problems for such thin gate dielectrics are degraded quality, high leakage current and boron penetration for dual gate CMOS devices. This paper is about our new approach to significantly improve gate oxide reliability while the drive current is enhanced by 15-20 % on PMOS devices. 20 A gate oxide was formed under sub-atmospheric pressure with Rapid Thermal Oxidation technique using both oxygen and hydrogen as precursors (In-Situ Steam Generation (ISSG)). Devices were fabricated with Shallow Trench Isolation scheme and poly-silicon/Wsi gate electrodes. Gate oxide reliability was evaluated with Time Dependent Dielectric Breakdown (TDDB). Significant lifetime extension was observed. In order to understand the mechanism of the improvement, SiO_2/Si interfacial structure was analyzed with X-ray Photoelectron Spectroscopy (XPS) while Silicon surface roughness was analyzed with Atomic Force Microscopy (AFM) and High Resolution Transmission Electron Microscopy (HRTEM) techniques. Hydrogen content and bonding structures were analyzed with Fourier Transfer Infrared Spectroscopy (FTIR).