BCB Wafer Bonding Technologies for Wafer-Level Packaging with an Integrated MEMS Resonator

摘要

As preliminary steps towards a smart wafer-level packaging, i.e. a wafer-level packaging integrating test devices, we investigated wafer bonding with photosensitive Benzo Cyclo Butene (BCB) firstly for cap sealing, and secondly, to simplify and reduce the fabrication cost of MEMS test devices in order to integrate them in the cap wafer of a wafer-level package. In a general way BCB technology allows low temperature Si/Si or Si/Glass wafer bonding with a high tolerance to surface topography. In this work we also show that BCB Si-Si wafer bonding can be combined with Si wafer thinning to obtain SOI-like substrates from which MEMS test devices can be fabricated by fully dry surface micromachining. This technology was used to fabricate Si cantilever beam microresonators that were characterized by quantitative stroboscopic optical microscopy with image processing. Results of Q factor measurements as function of pressure in the 10{sup}(-4)-1000 mbar range show that such devices can be used for pressure control inside a wafer-level package.