Wafer-level vacuum package of two-dimensional micro-scanner

We present wafer-level vacuum package of two-dimensional (2-D) micro-scanner based on glass-silicon anodic bonding. To form the sacrificial gap for evacuating air in the package cavity before hermetically sealed, the reflow process of Au/Sn/Cr posts due to low-melting temperature of Sn metal is introduced. Structures in Pyrex glass wafers are patterned using wet etching in the 49% HF solution. The 2-D micro-scanner is fabricated by the SOI-based micromachining technology. The resonant frequencies of 2-D micro-scanner after packaged in vacuum are 30 kHz and 290 Hz for the inner mirror and the gimbal frame respectively. The rotation angle of packaged 2-D micro-scanner is 25° at driving voltages of 20 and 17 V for the inner mirror and the gimbal frame respectively. The pressure in the package is estimated in terms of measuring the quality factor of packaged 2-D micro-scanner. The effect of packaging on the performance of the 2-D micro-scanner such as squeeze film air damping caused by the optical window and the substrate is also analyzed in this paper.