Journal of Vacuum Science & Technology B, Vol.19, No.6, 2494-2498, 2001
Effect of resist sensitivity ratio on T-gate fabrication
The need for short length T gates with good process control is demanding because pattern resolution is required in the lower level of resist. This article considers different resist systems and uses the resist sensitivity ratio between the head and foot defining layers to build two models. These are useful for determining the optimum parameters for T-gate fabrication and associated gate feeds. We show that the optimum resist sensitivity ratio is about 6 at 50 kV where bloating is negligible and good footwidth control is obtained. We also show that further improvements can be obtained by moving to 100 kV where a sensitivity ratio of 14 can be used. Sensitivity ratios between 6 and 14 can be achieved using either the poly(methylmethacrylate)/UVIII or ZEP520/UVIII bilayers since in both cases the sensitivity ratio can be varied by changing the development times and the bake temperatures.