A Glass-in-Silicon Reflow Process for Three-Dimensional Microsystems

• Published in: Journal of microelectromechanical systems 2013-12, Vol.22 (6), p.1470-1477
• Main Authors: Haque, Razi-ul M., Wise, Kensall D.
• Format: Article
• Language: English
• Subjects: anodic bonding; Biological and medical sciences; Biosensors; Biotechnology; Borosilicate glass; Etching; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Glass; glass etching; glass molding; glass reflow; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; Medical sciences; Methods. Procedures. Technologies; Micromechanical devices; Micromechanical devices and systems; Physics; Planarization; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Rough surfaces; Silicon; silicon molding; Technology. Biomaterials. Equipments. Material. Instrumentation; Various methods and equipments; vertical interconnect
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2013.2265851

This paper reports a new batch-mode fabrication process that combines glass and silicon into a single wafer. The technique requires only a single mask to lithographically define recesses in silicon using deep reactive ion etching. The patterned silicon wafer is anodically bonded to a glass wafer, and a high-temperature step reflows the glass into this silicon mold. The reflowed wafer stack is then planarized and thinned. Through-glass vias can be realized in this manner while additional process-flow modifications enable features such as molded cavities in the glass. A capacitive pressure sensor and a hermetically sealed resonator are described to illustrate applications of the process. Finally, a three dimensional packaging technique for implantable biomedical microsystems is shown by vertically stacking glass-in-silicon wafers.