Low temperature wafer bonding for micromechanical applications

A new class of modified silicon direct bonding processes is presented. The new process step within the bonding procedure involves the use of thin, intermediate layers to decrease the required process temperatures. The bonding process was characterized using oxidized silicon wafers. It was found that very strong bonds at temperatures around 200 degrees C or 350 degrees C can be achieved. Using ammonia-silica solutions, the surface energies achieve values of about 1.6 J/m/sup 2/. The lower bonding strength is compensated by offering a full IC-compatible bonding process. The influence of chemical and temperature treatment on the surface energies is described in detail.<
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