Low-Cost and Reliable Packaging Technology for Stacked MCP with MEMS and Control IC Chips

摘要

This paper reports a wafer-level package (WLP) encapsulation and a stacked multi-chip package (MCP) forrnelectrostatically actuated MEMS variable capacitor and control IC chips.rnSince the MEMS capacitor needs to be operated in dry atmosphere, we developed the WLP encapsulation structurernwith four thin-film layers fabricated by conventional back-end-of-the-line (BEOL) LSI technologies.rnFurthermore, since a MEMS chip is actuated by a control IC chip that provides high voltage, we developed thernstacked MCP to integrate the MEMS chip and the control IC chip. In order to handle relatively fragile WLPrnencapsulation, the stacked MCP process was optimized. The stacked MCP has 4.5×4.5mm size and 0.8mm thickness,rnwhich is the thinnest package for stacked MEMS and IC chips.rnNormal operation of the MEMS variable capacitor in the stacked MCP confirmed up to 85%RH after reliability tests,rni.e. temperature cycling, accelerated moisture resistance, and moisture/reflow sensitivity.