SHAPE OF THICK POSITIVE PHOTORESIST PATTERNS

The shape and the sidewall taper angle of positive photoresist patterns 2-5-mu-m in width and 1.5-9.3-mu-m in thickness were investigated to achieve a steep sidewall profile. Both experimental and calculated results showed that the taper angle increases with increased coated photoresist thickness, because the exposure dose is low at the bottom of a rather thick photoresist. The sidewall taper angle of a photoresist pattern 5-mu-m wide and 9.3-mu-m thick reached 84-degrees when using inorganic alkaline developer. The taper angles simulated by sample agreed with the experimental results within one degree.