Extension of U^* to electro-static problem and its application to structural design for porous low-k dielectric film

Higher performance large scale integration (LSI) requires copper (Cu) instead of aluminum (AD as a wiring metal because of its superior electrical conductivity. These LSI also requires lower dielectric constant to decrease line-to-line capacitance. Recently, porous low-k dielectrics are introduced for low-k dielectrics because of its ultra lower dielectric constant. However, their poor mechanical strength causes fractures of low-k dielectrics during Chemical Mechanical Polishing (CMP) process. Therefore, it is important to keep the mechanical strength of porous low-k dielectrics during increasing porosity. In this paper, we studied the mechanical strength and dielectric constant of porous low-k dielectrics by finite element method and U^* method. The U^* method expresses a degree of connection between a loading point and an internal arbitrary point. The effects of porosity of porous low-k dielectrics on the mechanical strength and dielectric constant were discussed.