Effects of photosensitive film sidewall profile with different exposure wavelength and process characteristics of plating bump technology

Wafer bumping is growing in importance with the increasing used of flip chip package. In this study, we tried to determine which factors at photosensitive film lithography process had an effect on photosensitive film sidewall profile. The analysis of the experiment indicates that different exposure wavelength between G,H and I line wavelength or exposure energy and DOF (deep of focus) can affect the photosensitive film sidewall angle and are significant to a 80 % level. The use of projection optics have the ability to focus the image as various depths (80 mum or greater) photosensitive films; this enables straighter sidewall angles and especially critical to control UBM CD (critical dimension) for plating bump process. The effect of photosensitive film scumming has a major concern on bump shear and reliability of wafer bump performance the well process control by lithography process will keep as lower yield loss of solder bump. The scanning electron microscopy (SEM) cross-section profile analysis was performed on the different via opening of photosensitive film with un-plated bump wafers and tries to figure out the process window and using optical microscope (OM) and EDX analyzed also show out observed results of scumming remainders. The best lithography procedure well control before solder plating deposition process is addressed to make the flip chip package success