Influence of the Atmosphere on Ultra - Thin Oxynitride Film for Precisely Controled Plasma Nitridation Process

Abstract

Influence of the atmosphere on ultra-thin oxynitride film was investigated for the precisely controlled plasma nitridation process. Some organic contaminant adsorb on the wafer before plasma nitridation process in clean room atmosphere. The adsorbed organic contaminant reduces the efficiency of plasma nitridation and increases the electrical thickness. The TDDB characteristic of ultra-thin oxynitride film was degraded due to the adsorbed organic contaminant. On the other hand, nitrogen concentration decreases due to exposure to an atmosphere after plasma nitridation process. The drop of nitrogen concentration causes Vth shift and Vth variation in MOSFET. The atmosphere and waiting time for post nitridation anneal affect on the drop of nitrogen concentration. It was demonstrated that the suppression of organic contamination before plasma nitridation and the control of the waiting time and atmosphere before post nitridation are the most important factors for the precise control of ultra-thin oxynitride film.