TEL Epion Inc. (TEI) provides systems for corrective etching of thin films such as silicon, silicon nitride, silicon dioxide, aluminum nitride, and various metals. The Ultratrimmertm processes substrates from 100mm to 200mm and is used to trim critical layers for SAW, BAW, and Hard Disk Drive Heads. It can also be used to smooth optical thin films. TEI also provides a trimming process in its nFusiontm product capable of trimming substrates from 200mm to 300mm.

The trimming process includes two steps. First a map of the film thickness is used to calculate the corrective etching parameters or electrical properties. Then the wafer is etched with the scan speed (dwell time) of the substrate is controlled to result in a variable etch amount as a function of position on the substrate. Thus, thickness variation can be reduced with sub-nanometer resolution.