An Investigation of Processes for Glass Micromachining

This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are simple processes but face difficulties in small and high-aspect-ratio structures. A sandblasted 2 cm x 2 cm Tempax glass wafer with an etching depth of approximately 150 mu m is demonstrated. The Tempax glass structure with an etching depth and sides of approximately 20 mu m was observed via the wet etching process. The most important aspect of this work was to develop RIE and glass reflow techniques. The current challenges of these methods are addressed here. Deep Tempax glass pillars having a smooth surface, vertical shapes, and a high aspect ratio of 10 with 1-mu m-diameter glass pillars, a 2-mu m pitch, and a 10-mu m etched depth were achieved via the RIE technique. Through-silicon wafer interconnects, embedded inside the Tempax glass, are successfully demonstrated via the glass reflow technique. Glass reflow into large cavities (larger than 100 mu m), a micro-trench (0.8-mu m wide trench), and a micro-capillary (1-mu m diameter) are investigated. An additional optimization of process flow was performed for glass penetration into micro-scale patterns.