Microcontamination control in a Lam 4400 plasma etcher: 15X reduction in particle defect densities during SF6/He silicon trench etch

摘要

Particles from the Lam 4400 blocked the etching of nitride and silicon during the trench etch for semi-recessed LOCOS field oxidation. This trench etch resulted in poor mean time between cleans (MTBC) of less than 500 wafers, reduced availability of the system, wafer scrappage up to 2.5%, and masked KLA defect source analysis at subsequent steps. EDX analysis of the particles showed them to be AlF$-x$/, the source of which we determined to be the Al chamber parts reacting with the F plasma. This unique paper shows the benefits of various improvements to plasma cleans, chamber cleans, and equipment hardware upgrades (such as DI water sealed, anodized chamber parts). We compare the performance of the tool before and after the improvements, resulting in a 10 fold increase in MTBC, 20% increase in system availability, 15X reduction in particle defect densities, and resultant zero wafer scrappage due to blocked trench etc. Detailed system performance data (MTBC, availability, particle data), KLA defect trend charts, and SEM/EDX data is presented.