Study of assembly processes for liquid crystal on silicon (LCoS) microdisplays

The critical processes that were developed include the lamination of cover glass on silicon and liquid crystal filling process. The critical objective behind the development of the lamination process was to attach a cover glass onto a silicon tile and to achieve a cell gap of 3 μm between them. The lamination process is similar to the fluids problem of flow between parallel plates. An analytical model was developed to estimate the time needed to achieve the cell gap by applying different pressures on the cover glass. The next process in the assembly is filling of liquid crystal (LC) material in the cavity between cover glass and silicon. The process works on the principle of flow of fluid in a capillary. The flow rate was enhanced by applying vacuum in the cavity. To estimate the time needed to fill a cavity by applying a certain vacuum pressure, an analytical model was developed. From the model it was observed that the fill time is a function of gap between glass and silicon, vacuum pressure applied, cavity length and the viscosity of the material being used for filling.