Numerically controlled sacrificial plasma oxidation using array-type electrode toward high-throughput deterministic machining

Deterministic machining processes, in which the removal distribution is programmed on the basis of surface figure error, are used for fabricating ultra-precision optics. In these processes, numerically controlled (NC) machining is performed by the dwell-time control of a small removal spot by controlling the scan speed of the work table. Although their accuracy is very high, their throughput is low because of the long path of a raster scan. Thus, we propose an array-type removal system that can control the dwell time to realise high-throughput deterministic machining. We focused on plasma-process-based deterministic methods, and NC sacrificial plasma oxidation was selected as the method for use in the prototype apparatus with an electrode array system. Using the system, the thickness range of the top silicon layer of a silicon-on-insulator wafer was successfully improved by the NC process, and it was demonstrated that the electrode array system can be used for deterministic machining.