Mechanical stress modeling for silicon fabrication processes

Two finite element methods are implemented to investigate localized mechanical stress fields generated during multiple stages of silicon IC fabrication. The boundary loading method (BL) uses the oxide interface stresses as a boundary condition for the substrate solution. In the fully integrated method (FI), the strains in substrate are calculated along with the oxide stress computation. Both of the methods can be used to couple stresses generated by oxidation volume expansion to strains present from other sources such as thermal expansion, dopants, and intrinsic film stresses. They are then evaluated on computational intensiveness and in stress solution variation. It is found that the BL method computes nearly the same oxide solution as the FI method and the oxide solution corresponds very well in the oxide and surface films for a LOCOS process.