Distribution of elastic stress as a function of temperature in a 2-μm redistribution line of Cu measured with X-ray nanodiffraction analysis

Authors：Hsu, Wei-You; Tseng, I-Hsin; Chiang, Ching-Yu^*; Tu, K. N.; Chen, Chih^*

Source：Journal of Materials Research and Technology-JMR&T, 2022, 20: 2799-2808.

DOI：10.1016/j.jmrt.2022.08.049

• Synchrotron radiation
• X-ray nanodiffraction
• Thermal strain map
• Redistribution lines

We investigated the lattice strain of nano-twinned Cu (nt-Cu) and regular Cu redistribution lines (RDLs) at 215, 300, 375 and 434 K using x-ray nanodiffraction; this technique has spatial resolution 100 nm. We found that the largest thermal strain or stress appeared at the corner of a Cu line at which the line turns 90 degrees. As the maximum thermal stress in both Cu lines did not exceed the yield strength of Cu, there was no plastic deformation at the highest temperature, 434 K. There was, however, a stress gradient in the corner, which might cause early failure in thermal cyclic tests. In nt-Cu lines, the stress value in the corner is 4.5% greater than the neighbor area at 375 K, and 7.4% greater at 434 K. The maximum stress of nt-Cu is 344.6 MPa at 434 K; the maximum stress of regular Cu is 363.8 MPa.