Integration of non photosensitive polyimide into an existing crossover photoresist process

A wafer fabrication process required a 6 μm thick polyimide coating over the final passivation to produce fringe capacitance shift for final electrical trimming prior to final hybrid packaging. This article discusses the methodology used in the development of the spin coating process, polyimide softbake temperature determination and integration of the nonphotoimagable polyimide into an existing crossover photoresist process. A unique method of determining the polyimide´s etch rate in a positive developer solution is discussed along with the use of FTIR to characterize the high temperature imidization process