PREDICTIVE MODEL-BASED CONTROL OF CRITICAL OXIDE ETCHES FOR SUB-100NM PROCESSES IN A SINGLE WAFER WET PROCESSING SYSTEM

摘要

The etching kinetics of thermally grown SiO_2 were investigated in dilute HF solutions (100:1 to 500:1) as a function of temperature, HF concentration, and fluid dynamics. Results from this study support a model with surface chemical reaction-controlled kinetics with an activation energy of about 32 kJ/mole. As expected, the oxide etch rate strongly depends upon HF concentration. The etching mechanism is briefly discussed with regard to species distribution considerations. Based on these experimental results, a predictive model has been developed for critical oxide etch process control. The model takes etch target as the sole operator input and automatically determines the required etch time, depending upon real-time process conditions. These conditions include HF temperature, HF concentration, and the number of wafers that have been processed through the system. Results using this model based control show excellent WIW and WTW etch uniformity for thin oxide etch process in a single wafer immersion processing system.