Problems of Microsystems Reliability Design with Redistribution Layers in Wafer Level Packaging

The article is devoted to the problems of reliability of microsystem designs created by the technology of internal mounting of semiconductor dies in compound with redistribution layers at the wafer level packaging. The problems of thermomechanical stresses occurrence in redistribution layers made of materials with different coefficients of thermal expansion and ways of their reduction are considered. A new dependence of the value of thermomechanical stresses in redistribution layers on the geometrical dimensions of copper commutation and polymeric materials is revealed. The paper describes the problems of adhesion of polyimide layers to copper and silicon in redistribution layers of microsystems with embedded dies. The results of experimental studies on increasing the adhesion strength of copper commutation to polyimide by pretreatment of the dielectric with adhesion promoters based on aminosilanes and epoxysilanes are presented. The choice of application of polyamide acid based on aromatic diamine and dianhydride of aromatic tetracarboxylic acid for giving plasticity to polyimide microstructures and providing the highest adhesion to semiconducting silicon die was substantiated. The influence of the value of adhesion strength of the die to polyimide depending on the method of silicon surface treatment and the lifetime of polyamide acid from the moment of application of the material to the temporary carrier was determined.