Fabrication of piezoelectric MEMS devices-from thin film to bulk PZT wafer

Integrating patterned functional piezoelectric layer onto silicon substrate is a key technique challenge in fabrication of piezoelectric Micro Electro Mechanical System (pMEMS) devices. Different device applications have different requirements on the thickness and in-plane geometry of the piezoelectric layers and thus have their own processing difficulties. In this paper, the techniques of integrating piezoelectric function into pMEMS has been discussed together with some diaphragm-based pMEMS devices which have relatively lenient requirement on patterning of the piezoelectric layers. Sol-gel thin film can meet the requirement of most of the sensor applications. The composite thick film is one of the promising solutions for thick film devices due to its good processing compatibility. Si/Pb(Zr _x Ti_1 − x )O₃ wafer bonding technique makes it possible to thin down the ceramic wafer to less than 10 μm by using chemical mechanical polishing, which, therefore, provide us another approach to integrate thick piezoelectric layer on silicon to cover the need of most of the thick film devices. Directly make double side aligned electrode patterns on bulk piezoelectric wafer/plate by using photolithography opens up a new area of pMEMS. The advantage of using bulk piezoelectric wafer/plate in pMEMS is that we can select commercial available ceramics or single crystals with excellent piezoelectric properties and thus ensure the overall performance of the devices.