A feasibility study on the micro electro-discharge machining process for photomask fabrication

A feasibility study of micro electro-discharge machining (micro-EDM) techno logy has been conducted for its possible contribution in the photomask indu stry. A series of experimental runs was performed on three specimens using a micro-EDM system with built-in wire electro-discharge grinding. Different thicknesses of chromium films were coated on borosilicate glass substrates . Unwanted chromium metal was machined through to the transparent glass sub strate, leaving behind the desired pattern. In this study, lines were machi ned at different voltages, using electrodes of 20 gin in diameter, and no s ignificant wear of electrodes was observed. The machined regions on the specimens were quantified in terms of linewidth deviation and light transmission. The experimental results showed that the linewidth deviations for all three specimens are below the 10% cut-off thr eshold. The best average light transmission obtained from this experiment w as 75.8% at 90 V. The results gathered so far, suggests that the applicatio n of micro-EDM to produce a photomask is an acceptable process.