Frequency trimming of silicon resonators after package with integrated micro-evaporators

This paper presents for the first time a novel method to trim the resonant frequency of a silicon bulk acoustic resonator after package with an integrated micro-evaporator. The micro-evaporator is bonded to the silicon resonator face to face. During trimming, an electric power is applied to heat the micro-evaporator locally to evaporate the top aluminum layer. The resonant frequency of MEMS resonator is trimmed permanently by the deposition of Al. The trimming rate is sensitive to the electric power and can be adjusted from -0.3 ppm/min to -12.2 ppm/min. The method can be used for both the coarse and the fine trimming.