Contactless Endpoint Detection of Gold Etching Using Quartz-Based Capacitive Detector

A method for the contactless endpoint detection of gold etching using a quartz-based capacitive detector is reported herein. To design a microfabrication process, the etch rates of materials to be used must be determined to control the etch depth. However, the etch rate changes gradually when the etching solution is used repeatedly. An endpoint and/or etch rate detection method is required to ensure process repeatability in a manufacturing environment. This method should be contactless because the etchants for metals are typically highly corrosive. In this study, a 32 MHz quartz-crystal oscillator is used to detect changes in the concentration of specific ions. The developed method can detect nanometer-order thickness changes during gold etching.