Conformal photoresist coating for critical dimension improvement

3D surface topography of read / write head fabrication is difficult for lithography process. Photoresist deposition by using the conventional spin coating method is troubled. Spray coating is a replacement technique that eliminates the problem by producing micro-resist droplets that adhere firmly to the deposition location; thus, spray coating with optimal parameters from designed experiment is a suitable method for photoresist deposition on structures with high aspect ratio. By using proper nitrogen flow rate to spread out AZ4999 resist to be micro-droplet in the same time with proper traveling nozzle speed, the photoresist turbulence will perform good resist coverage over all surfaces. From design of experiment show the optimum condition for conformal deposition is 0.8 Bar at 117 mm/s for nitrogen pressure and nozzle speed, respectively. Photoresist thickness was dropped at 30um far away from groove or edge of the head.