Uniformalization of AT cut quartz crystal wafer thickness using open‐air type plasma CVM process

Abstract

AbstractImprovement of thickness variation of the AT cut quartz crystal wafer is very important to advance the performance of the quartz resonator and to improve the productivity. However, conventional machining cannot exceed its technical limit any more, because quartz crystal is brittle and the wafer having thickness less than several tens of micrometers is required. We have newly developed the chemical finishing process to correct the thickness variation of the quartz crystal wafer, which utilizes localized atmospheric pressure plasma without gas replacing process. In the case of the atmospheric pressure plasma, high‐density plasma region is localized in the vicinity of the electrode because of its small mean free path. Removal volume is proportional to the dwelling time of the plasma on the workpiece surface. Therefore, free figuring without mask pattern is realized by numerically controlled scanning of the localized reactive area. By applying our proposed correcting process, thickness variation of the commercially available AT cut quartz crystal wafer was improved from 270 to 40 nm. Copyright © 2008 John Wiley & Sons, Ltd.