Thermal stress and debonding in Cu/low k damascene line structures

In this study, the thermal stress and debond characteristics of Cu damascene structures were investigated using X-ray diffraction and 3D finite element analysis (FEA). First, X-ray diffraction was used to measure thermal stresses in Cu line structures embedded in TEOS and low k SiLK™ dielectrics. In FEA, an efficient 3D model was developed and verified by checking with X-ray stress data of Cu lines and results obtained from a multi-line 3D model. This simplified model was employed to calculate the effect of scaling line width on thermal stress characteristics of Cu lines and ILD in TEOS and SiLK structures. Compared with TEOS, the SiLK ILD was found to have significantly larger thermal strains that approach a nearly hydrostatic state with decreasing line width. The energy release rates G for the barrier/low k interfaces were calculated for both single and dual damascene structures and compared with the 4-point bending test results.