Particle control in dielectric etch chamber

A methodology for evaluating and controlling particle performance in a dielectric etch system is developed and presented. Analysis of particle samples, collected from premature chamber failures for out-of-control particle levels, suggests sputtering of the upper electrode during etching is a key modulator to this problem. To eliminate such sputtering, we designed a series of experiments with the objective of identifying a between-lot conditioning (BLC) process capable of creating a uniform and solid layer of polymer coating that covers the entire upper electrode of a parallel plate, RF, magnetically enhanced reactive ion etch system. An approach comprising a series of short wafer processing marathon runs, with polymer coverage and particle performance as the two main responses, was then used to identify a candidate process for BLC recipe and usage frequency. Adequate non flaking polymer coverage of the upper electrode was achieved by utilizing a BLC process based on octafluoro-cyclobutane/oxygen/argon/carbonmonoxide [C₄F₈/O₂/Ar/CO] chemistry at high RF power and short transit time settings. The candidate process was then optimized and tested in a manufacturing pilot involving multiple production etch chambers and was subjected to extensive process performance metrics. Based on this methodology, the optimized BLC was successful in controlling defects and in attaining the mean wafer between wet clean goal for the etch system under investigation.