Abstract
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 × 2 cm Tempax glass wafer with an etching depth of approximately 150 µm is demonstrated. The Tempax glass structure with an etching depth and sides of approximately 20 μm 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-μm-diameter glass pillars, a 2-μm pitch, and a 10-μm 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 μm), a micro-trench (0.8-μm wide trench), and a micro-capillary (1-μm diameter) are investigated. An additional optimization of process flow was performed for glass penetration into micro-scale patterns.
Highlights
Due to the superior material properties of glass, including transparency, mechanical robustness, and dielectric properties, the glass has been widely used for micro-nano mechanical systems [1,2], micro-nano fluidic devices [3,4], and optical MEMS (Microelectromechanical systems) devices [5].The glass substrate can be joined to a silicon substrate via the anodic bonding process without any additional adhesive, whereas these bond seals show good hermetic vacuum [6,7] and high bonding strength [8]
Deep Tempax glass pillars having a smooth surface, vertical shapes, and a high aspect ratio of 10 with 1-μm-diameter glass pillars, a 2-μm pitch, and a 10-μm etched depth were achieved via the reactive ion etching (RIE) technique
The patterning silicon structures with high aspect ratios can be achieved via deep RIE techniques [9]
Summary
Due to the superior material properties of glass, including transparency, mechanical robustness, and dielectric properties, the glass has been widely used for micro-nano mechanical systems [1,2], micro-nano fluidic devices [3,4], and optical MEMS (Microelectromechanical systems) devices [5]. The patterning silicon structures with high aspect ratios can be achieved via deep RIE techniques [9]. Low aspect ratio, low etching rate, limited mask selectivity, and high surface roughness are still current problems in glass micromachining. An etched cavities in silicon is bonded with thin glass wafer. This wafer is heated inside a furnace at a high temperature. Four techniques for glass micromachining are investigated and evaluated, including sandblast, wet etching, RIE, and glass reflow techniques. Sandblast and wet etching techniques are simple processes but they face difficulties with small and high-aspect-ratio structures. Deep Tempax glass pillar structures with smooth surfaces, vertical shapes, and high aspect ratios by using RIE are studied. Glass reflow into large cavities, a micro-trench and a micro-capillary is investigated
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