This paper proposed a new direction for the miniaturization of silicon bulk-machined sensors. Herein, the glass substrate bonded with the silicon wafer substitutes the role of the silicon wafer itself. Then the whole silicon wafer with sensing portions, whatever piezo-resistive or capacitive types, could be all machined to the membrane structure without chip-area wasting on the (111)-face slopes. Basically, the chip size by this semi-SOI method would be as small as the surface-machined one in principle, if the silicon-glass bonding process is guaranteed. The other advantages of this strategy include the process compatibility with the different sensing principles and the different techniques of membrane machining. The on-chip circuitry of sensors could be also preserved. Another important issue is that the surface- machining-link membrane now is mono-crystalline, which means the stable mechanical properties and reproducible characteristics. This new strategy practically augmented the mass production of piezoresistive pressure sensors using in tire pressure gauges and other industrial pressure meters. The 1.0 mm X 0.8 mm X 0.5 mm of sensor size with chip density exceeds 5,000 per 4-inch wafer was successfully fabricated. Some engineering applications used this new pressure sensor to solve their corresponding problems.
SPIE's symp. on micromachining and microfabrication v.3876-32