Influence of packaging on frequency drift in MEMS resonators-Dynamic effect of packaging on MEMS device performance

In order to clarify the source of resonant frequency drift in MEMS resonators, thermal expansion effect of packaging on MEMS devices was investigated. The strain in a silicon plate bonded on an aluminum plate with temperature was precisely measured. Increasing amount of strain in the aluminum plate was as large as 200 micro-strain with increase in only 20 degrees of temperature. The strain in the silicon plate was in a same order of change, however, compressive. Thermal expansion coefficient in Al is approximately ten times of that in Si. The reason of the opposite tendency in strain was speculated to be caused by bending in a Si-Al plate.