Transient behavior during film removal in diffusion-controlled plasma etching

A mathematical model is formulated to analyze transient behavior during film removal from closely spaced wafers in a barrel plasma etching reactor. The model incorporates diffusion and simultaneous reactions which include the etching process as well as recombination reactions of both volume and surface types. The analysis relates the effect of geometric and operating variables to process characteristics such as etch uniformity, over-etch exposure, and throughput. Dimensionless system parameters are identified and are used to express computed results in general form. Regions of operating conditions that permit etch uniformity within specified tolerances are found, and optimum settings for inter-wafer spacing and reactor pressure to achieve maximum throughput are calculated.