X‐ray Microscopy Studies of Electromigration in Advanced Copper Interconnects

X‐rays have the advantage that they penetrate samples which are several micrometers thick without significant sample damage, and that they provide a chemical image contrast between different dielectric layers of the Cu/low‐k on‐chip interconnect stack. Therefore, x‐ray microscopy is an ideal tool for quantitative 3‐D investigations of void dynamics with high spatial resolution of 20 nm. Using the BESSY full‐field transmission x‐ray microscope (TXM), we performed electromigration studies of advanced backend‐of‐line (BEoL) stacks of high‐performance microprocessors containing copper interconnects and low‐k materials. We observed void movement along the top copper/dielectric (SiN_x) interface which is found to be the main pathway for electromigration‐induced atomic copper transport.