Improvement of deteriorated resolution caused by polarization phenomenon with TARC process

As the feature size becomes smaller, the diffracted light angles get larger, which makes polarization phenomenon severer. As the diffracted light angel becomes larger, the contrast of optical image by p-polarization becomes worse than that by s-polarization. So, it is desirable for better resolution that more s-polarization can be absorbed in resist film than p-polarization. As one of the approaches, we investigated the way of controlling the property of an overcoat on resist called TopARC, or TARC. The ratio of dose in resist film by s-polarization to total dose was calculated by simulation and the optical property and thickness of TARC was optimized to make the ratio of s-polarization largest. Experimentally the alternating PSM was used to make the 2 diffracted lights pass through only the outmost area of pupil, which makes the polarization phenomenon most prominent. ArF scanner with 0.75NA was used. The experimental data showed that the exposure latitude was improved by TARC process optimized to compensate polarization phenomenon.