Topography-induced thickness variation anomalies for spin-coated thin films

Abstract

A low-pass frequency filter model for predicting thickness variations on complex topography is investigated for several spin-coated thin films. Frequency weighting parameters are presented for PMMA, HPR204, HPR206, OFPR800, MPR resist coatings and a spun-on glass coating (X-600). One weighting parameter a tends to be inversely proportional to the solution viscosity and indicates the conformality of the coating. The other parameter Pmin depends on the spun-on film thickness and the step height. Simulated coated topography contours are compared to experimental profilometer traces to demonstrate the validity of the modeling technique. Effects of topography orientation with respect to the wafer center are also examined. More uniform spun-on coatings on topography are obtained at lower spin speeds. PMMA and HPR206 coatings are compared. Simulations of two- and three-dimensional coated topography are presented to indicate coating thicknesses variations within complex arrays and at the edge of large arrays.