Ozonated water, as an alternative to a Sulfuric – Peroxide Mixture (SPM), was introduced to the resist strip and cleaning processes to prevent surface haze formation through the elimination of sulfuric acid from these processes. [1] [2] [3] [4] [5] However, it also was found to cause significant change of optical characteristics and CD-linewidth shift on ArF6% attenuation phaseshift masks (AttPSM). Although the use of 172nm Excimer UV light irradiation treatment before the cleancouldimprove the above-mentioned shifts, after several clean cycle, this phase/CD preservation effect would be dramatically degraded.[6] [7] [8] In this paper, a novel approach of phase preservationto usedry treatments based on reactive plasma Asher as part of acid-free resist strip or cleaning process is introduced. [9][10] We have investigated on the surface material integrity and CD stability of MoSi based shifters and compared with above-mentioned approach of 172nm UV light irradiation treatment, and tried to illustrate and explain the principle. Not only Asher process but also UV irradiation, is supposed to be kind of oxygen activation process to accelerate oxidization on MoSi based shifter of ArF AttPSM masks, and created passivation layer would stand out for wet cleaning; furthermore, plasma Asher process is in prior to UV irradiation. As shown in Cross-section profiles on the masks without and with Asher process, although the deference is very limited, it may be proved that a thin passivation layer was created on the surface and side of MoSi based shifter after Asher process.

Date Published: 9 September 2013
PDF: 10 pages
Proc. SPIE 8880, Photomask Technology 2013, 88801L (9 September 2013); doi: 10.1117/12.2023019

Published in SPIE Proceedings Vol. 8880:
Photomask Technology 2013
Thomas B. Faure; Paul W. Ackmann, Editor(s)