Fabrication of phase-shifting masks employing multilayer films

T. C. Chieu; Kwang Kuo Shih; Derek B. Dove

doi:10.1117/12.175412

17 May 1994 Fabrication of phase-shifting masks employing multilayer films

T. C. Chieu, Kwang Kuo Shih, Derek B. Dove

Proceedings Volume 2197, Optical/Laser Microlithography VII; (1994) https://doi.org/10.1117/12.175412
Event: SPIE's 1994 Symposium on Microlithography, 1994, San Jose, CA, United States

Abstract

The design and fabrication of phase shifting masks using multi-layer films are summarized. Mask blanks consist of fused silica substrates coated with a top chrome layer, an SiO₂ phase layer, and an etch-stop layer. The layer thicknesses are designed to give a (pi) -phase shift at 248 nm (or at 365 nm), and equal and maximal transmission at etched and non-etched regions. The chrome layer is patterned by e-beam resist and is etched by reactive ion etching (RIE) with Cl₂ chemistry. The SiO₂ layer is patterned by another e-beam resist in registration with first chrome pattern and is etched by RIE with CHF₃ chemistry. Two materials were investigated as the etch stop layer, namely Al₂O₃ and HfO₂, with the latter having advantageous properties. It is shown that a 20% processing window is achieved in this type of PSM for a 5 degree phase accuracy as in contrast to quartz etched PSM in which the etched depth and uniformity has to be controlled to within 2.5% for a similar phase accuracy.

Citation Download Citation

T. C. Chieu, Kwang Kuo Shih, and Derek B. Dove "Fabrication of phase-shifting masks employing multilayer films", Proc. SPIE 2197, Optical/Laser Microlithography VII, (17 May 1994); https://doi.org/10.1117/12.175412

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