Variation reduction of a closed-loop precision ceramic micromachining process

Abstract

This report details the investigation of the micromachining of a TiC.A1203 ceramic using a closed-loop lapping process. Currently the micromachining process laps a ceramic bar with only a priori flatness adjustment. Bar flatness is adjusted prior to the lap using optical measurement of lithography targets. The average value of a critical dimension determines lap completion. The critical dimension is determined with an embedded electronic lapping guide (ELG). The problem with this technique, as it is currently employed, is high product loss due to large variance of the critical dimension across the bar. A six microinch standard deviation is desired. Any product above or below specified critical dimension limits are scrapped, so the variance reduction directly impacts immediate and downstream process yields. An alternative approach is proposed using electrostrictive actuators in a closed control loop to deform the bar during lap processing. The closed-loop lapping (CLL) process significantly decreases critical dimension process variance.