Study and improvement approach to 193-nm radiation damage of attenuated phase-shift mask

摘要

The exposure tools have been advanced for finer patterns and higher throughput. However, it causes the increase of accumulation of exposure dose on mask, which induces the mask CD growth. This issue has been reported as the radiation damage and brought the low yield of device chips [1, 2, 3]. As the solution, the radiation damage can be reduced by the ultra extreme dry air in exposure tool [4]. It is difficult to adopt dry air to all exposure tool due to cost. In this work, we tried to solve the radiation damage from photomask making approach. The attenuated phase-shift mask (art. PSM) was chosen for this evaluation because its damage is severest. The test plates of att. PSM were exposed by ArF laser, and the amount of CD degradation and the composition change in damage area were investigated. By the analyses of TEM and EDX, it was confirmed that the root cause of radiation damage is oxidation of MoSi film. Therefore, the approaches from mask process and material were tried to prevent MoSi film from oxidation. As a result, the approach from mask material, especially modification of MoSi film is effective. And the characteristics of new MoSi film, such as CD performances, cross section, and cleaning durability, were compared with conventional att. PSM. These results show the characteristics of two masks are equivalent. Att. PSM with new MoSi film is promising solution to improve radiation damage.