Bulge Test Investigation of The Influence of Moisture on Mechanical Properties of Thin Polymer Layers

Abstract

AbstractThin polymer layers gain importance as interlevel dielectrics in microelectronic devices. One major drawback of this class of material is instability of mechanical properties under changing climatic condition. The paper deals with evaluation of the bulge test as complementary method for investigation of humidity induced alterations of mechanical properties. It describes measurement of intrinsic as well as humidity induced stress in polymer layers. The given results agree very well with those obtained by substrate bending. Furthermore, bulge testing proved the assumption of earlier work, that change of mechanical stress is due to a humidity induced swelling process that can be described phenomenologically by expansion coefficient and a biaxial Young's modulus independent from relative humidity. Results are given and discussed for two types of polyimide.