Development and Optimization of Contact Module Process for MicroBridge Structure based MEMSSensor Application* In this work, trench first process integration scheme was used to develop MEMS contact module, and local surface planarization was realized by the optimized design and process control. Thin electrode layer was deposited on the sidewall and bottom of contact hole to form the electrical connection from microbridge surface to bottom readout circuit without any metal or dielectric plug filling in the contact. Dark spot problem was found in nonuniformity electrical output map for one of the products with large scale array, which was corresponding to the increase of contact parasitic resistance. Failure analysis was done, and it was found seriously bottom and sidewall lateral corrosion problem on the bottom of the contact structure, which had caused thinning or even discontinuity of the electrode layer. After comparative experiments design and results analysis, contact wet cleaning process was found to be the root cause. During contact wet cleaning process, the reactive solution in the deep contact may not easily be removed, and the residue solution will damage the metal on the bottom and sidewall of contact and cause lateral corrosion problem. Based on the analysis results, optimized process has been developed, and the waferlevel yield test result shows that the dark spot problem has been greatly improved.

A Novel Piezoresistive MEMS Pressure Sensors Based on Temporary Bonding Technology A miniature piezoresistive pressure sensor fabricated by temporary bonding technology was reported in this paper. The sensing membrane was formed on the device layer of an SOI (SiliconOnInsulator) wafer, which was bonded to borosilicate glass (Borofloat 33, BF33) wafer for supporting before releasing with CuCu bonding after boron doping and electrode patterning. The handle layer was bonded to another BF33 wafer after thinning and etching. Finally, the substrate BF33 wafer was thinned by chemical mechanical polishing (CMP) to reduce the total device thickness. The copper temporary bonding layer was removed by acid solution after dicing to release the sensing membrane. The chip area of the fabricated pressure sensor was of 1600 xcexbcm xc3x97 650 xcexbcm xc3x97 104 xcexbcm, and the size of a sensing membrane was of 100 xcexbcm xc3x97 100 xcexbcm xc3x97 2 xcexbcm. A higher sensitivity of 36 xcexbcV(Vxe2x88x99kPa) in the range of 0xe2x80x93180 kPa was obtained. By further reducing the width, the fabricated miniature pressure sensor could be easily mounted in a medical catheter for the blood pressure measurement.