Thickness control by ion beam milling in acoustic resonator devices

In this paper, practical aspects of production worthy methods for film uniformity adjustment (trimming) used in manufacturing of Film Bulk Acoustic Resonator (FBAR) filters have been presented. Two-step trimming in conjunction with thickness "smoothing" technique control total thickness range to within less than 8 A on product wafers with variable surface film etch rates even with difficult to measure film thickness. Trimming processes were used to allow using one wafer from a batch to provide compensation feedback in the FBAR devices. Combining ion mill with deposition in the same tool produces <;0.1% uniformity in the deposited films.