Integration and packaging technology of MEMS-on-CMOS tactile sensor for robot application using molded thick BCB layer and backside-grooved electrical connection

This paper describes a novel integration and packaging process for a chip-size-packaged integrated tactile sensor. A MEMS wafer and a CMOS wafer were bonded with a thick (50 µm thick) BCB (benzocyclobutene) layer, which also works as the dielectric layer of sensing electrodes. The large thickness is advantageous to reduce parasitic capacitance to the CMOS circuit. The thick BCB layer was formed on the CMOS wafer and molded with a glass mold to make a flat surface with via holes. For surface mounting, bond pads are located on the backside of the senor chip by drawing electrical feed lines through the chip edge. To make the feed lines in wafer level, tapered grooves were fabricated along the scribe lines by TMAH wet etching, and half dicing was done along the grooves to access electrodes on the BEOL layer. Finally, the tactile senor was completed and preliminarily evaluated.