A Study on Bevel Metal Film Removal for Bevel Peeling Defect Reduction

With logic technology reached 28nm and beyond, wafer bevel peeling defect is becoming one of the major yield killers. One of the most important sources is the mismatched stress induced by BEOL bevel metal films. In this work, firstly, the mechanism of wafer bevel peeling defects caused by bevel metal films is studied. Then, backside wet etching process is introduced to remove the bevel metal films to reduce the peeling defect. Thirdly, we successfully solve the undercut issue generated during backside wet etching process via optimize the process conditions. Finally, a good result with better bevel metal film removal with defect count has been reduced by 200% and free of undercut is achieved through optimizing process conditions of backside wet etching process.