Quencher gradient resist process for low k process

摘要

To accomplish minimizing feature size to sub 70 nm, new light sources for photolithography are emerging, such as F2(157nm), and EUV(13nm). However there are many problems that should be solved for real device production. So extension of ArF(193nm) is necessary until the maturity of new lithography technique will be prepared. In this paper, we tested the feasibility of quencher gradient resist process (QGRP) to low k process. To compare with normal patterning process, QGRP needs additional step, over-coating. But this over-coating material differs from the normal over-coating materials in that over-coating material of QGRP has acid quencher sources. After the exposure, these quencher materials diffuse into the photoresist and quench excess acid that causes a sloped resist profile. As a result, vertical profile pattern can be obtained with QGRP. Using this QGRP, 70nm process, of which k value is 0.27, is possible with 0.75NA ArF scanner. For contact hole pattern, we could get direct 70 nm C/H with QGRP. The exposure latitude of 70nm contact hole was improved more than 50% in case of QGRP compared with normal process. In addition, QGRP is applicable for immersion lithography.