The effects of post-process techniques and sacrificial layer materials on the formation of free standing polysilicon microstructures

Through designed experimental analysis (ANOVA), the etchant concentration, percentage of overetch, and rinse agent used in the undercut process are shown to have significant effects on the size that polysilicon microstructures can be fabricated without collapse. This analysis is carried out for a variety of sacrificial layer materials, with results dependent on the material used. It is shown that these effects are so dramatic that the resulting strain level of the film may be difficult to determine without further analytical study. When microbridges, cantilevers, and proof rings are used to measure the local strain of thin films optically, it is shown that great care must be taken when interpreting the local strain and that further work is needed to develop procedures to eliminate this problem and formulate a theoretical explanation for the physical forces behind the results observed.<>