Laser Assisted Solder Bump Mold Fabrication

Sold bump mold fabrication using Excimer laser (KrF, 248 nm) source for patterning method is presented. The mold is designed to make reflowed solder bump with diameter of 115 ¿m for 8 inch wafer. We have developed CrOx / Cr binary metal masks which allow for obtaining circular cavities with diameter of 160 ¿m, depth of 50 ¿m and pitch of 300 ¿m. We have obtained the characteristics of patterned etch mask with diameter of 60 ± 3 ¿m, pitch of 300± 2 ¿m by laser method. Cavities are performed with a dilute hydrofluoric acid (HF) solution, having the diameter of 160 ± 3 ¿m, depths of 50 ±1 ¿m. These results indicate that solder bump mold fabrication using laser method enables cavity formation with good uniformity.