Study of optimization condition for spin coating of the photoresist film on 3 inches wafer by taguchi design of an experiment

Abstract

This paper reports the study in suitable conditions of 5 parameters in order to spin coat positive photoresist AZ-P4620 on 3 inches silicon wafers. The design of experiments (DOE) is Taguchi L₁₆(4⁵ ) which can reduce number of experiments from 1024 to 16. By analyzing the main impact plot of signal to noise ratio (SNR or S/N), it is found that the most suitable values of the 5 parameters that give the desired thickness and uniformity is photoresist dispense time of 25 seconds then spin at the speed of 500 rpm for 5 seconds, accelerate the spin speed at 200 rpm per seconds until the speed reaches 1500 rpm. The speed is maintained at 1500 rpm for 60 seconds with the exhaust pressure of 300 Pascal. The wafer is later baked at 100^o C for 90 seconds. The calculated thickness of the final film is 70274±908.233 Angstroms. This DOE can be applied to the Air Bearing Surface (ABS) of a read/write heads in the hard disk drive industry.