High Topography Polyimide CMP Process

This paper reports a process of filling and planarization of microstructures for MEMS and wafer level packaging application. In this work, cavities of 5-10mm depth and 20-100mm in length/width are filled using multiple coatings of polyimide with kinematic viscosities in the range of 20-130St. Such filling results in overfilling of polyimide in the range of 2 to 10mm due to variation in density and geometry of microstructure. A chemical and mechanical polishing (CMP) based planarization process, to achieve polyimide thickness variation <0.2mm in varied structures is presented.