PZT driven micromachined 2-D membrane arrays

We present a 2D micro-actuator array and its potential for programmable acoustic radiation forces. The actuator array is a hybrid stack that consists of VLSI die at the bottom, bulk PZT actuator array as the intermediate layer, and a MEMS die on top to enable controlled actuation of the surface of the top die. The PZT actuator is organized in a rectilinear array of PZT pillars flip-chip bonded to a VLSI die. They provide localized off-chip actuation of the MEMS die which can also have sensors to provide feedback to the VLSI die. This paper presents fabrication and electrical test results from a prototype, which implements metal routing to desired PZT pillars at the VLSI die level and membrane formation at the MEMS die level, in order to maximize displacement. The paper also presents driving schemes to achieve mode control of acoustic fields on the chip surface.