Reliability improvement of Semitool SAT-post CMP cleans

A brief overview of Chemical Mechanical Polishing (CMP) and post oxide polish wafer cleaning, and a summary of the tool reliability and process control improvements are presented in this paper. Semitool´s Spray Acid Tool (SAT) is used in AMD´s Fab25 for post oxide polish wafer cleaning with APM (Ammonium Peroxide Mix). This paper discussed the critical role of the post polish chemical cleaning process and the dramatic improvements to tool reliability, wafer cleaning effectiveness, and repeatability of tool performance in order to meet the aggressive tool utilization and stringent defect density requirements of Fab25. A key element of this improvement was the implementation of an in situ concentration monitor that uses NIR (Near Infrared) absorption spectroscopy to guarantee the integrity of the APM solution and provide real time concentration monitoring of NH₄OH and H₂O₂. With the improvements, the Cp_k of the oxide etch rate improved greatly from 0.162 to 12.9 with the same spec limits, and the mean particle count went from 32.93 defect/wafer with 46% downtime to 1.40 with 1% downtime