Implementation of a low temperature wafer bonding process for acceleration sensors

The paper describes a low temperature bond process based on an oxygen plasma pretreatment followed by 200°C and 400°C annealing which was to be integrated in our technological process flow to produce micromechanical devices in bulk and surface micromachining like acceleration sensors, gyroscopes and mirror arrays [1]. The results of infrared transmission and the measured bond strengths of the prepared test wafers will be presented in dependence on various pre-treatments and annealing times as well as temperatures. First die separation tests as well as additional detailed investigations showed that the bonding process has the potential to replace an anodic bonding process. During the development of the low temperature bond process it was shown that it is possible to reach a bond strength between 1.5 J/m2 and 2.8 J/m 2 depending on the annealing conditions. To optimize the necessary size of the bond frame and to quantify the bond strength limits of the process a test patt ern was designed with different arrangements of sensor structures like bond frames, spaces and chevron notch structures. The investigation showed the achieved bond yield in dependence on different sensor structures and bond conditions.