Defocus Simulation Using Observed Dissolution Rate in Photolithography.

This paper reports a simulation of the profile of the photoresist in a defocused situation via the measured values of the dissolution rate. The authors used the model based on Mack et al. as a model of the light intensity distribution within the photoresist in the defocused situation. On the other hand, the dissolution rate was measured from the variation of the interference light intensity due to the change of the photoresist film thickness. By combining these parameters, the appropriateness of the Mack and Bernard models was verified by improvement using Grindle's method. As an experiment to verify the validity of the present simulation method, high-resolution positive resist for the i-line (365 nm) was used and a patterning was carried out by changing the amount of defocus within NA 0.50 i-line stepper. In addition to SEM observation, corresponding simulations were carried out for comparison of the shape. In the case when the resist shape is the best (or in the case of the so-called best focus situation), it was studied at what location in the resist film the focus point exists. It was found that the SEM observation results and the profiles obtained by simulation agreed and the difference of the shape in the plus defocusing and minus defocusing was reproduced by computation. This indicates the validity of the defocusing model by Mack et al. [ABSTRACT FROM AUTHOR]