LCOS IC Metal Pits Defect Mechanism And Improvement

In semiconductor manufacture, metal pits defect always exists in Al film, which badly degrades HD (High Definition) LCOS (Liquid Crystal On Silicon) surface flatness and reflectivity, impacts backend assembly testing yield, and induces reliability issue. Mostly think that metal pits defect is induced by Al-Cu galvanic cell reaction. However, up to now no integrated improvement methods, especially for LCOS process development. In this paper, will start from metal pits defect structure and component, combine its mechanism and find out three effective methods: wet clean time decrease, SiO2 layer and O2 treatment application to improve it, based on LCOS wafer split experiment. The integrated application of the three methods is very helpful to increase LCOS product yield and much valuable for LCOS product development and CMOS process improvement.