New approach to phase metrology for manufacturing 248-nm lithography-based embedded attenuated phase-shifting mask

Giang T. Dao; Gang Liu; Alan Snyder; Jeff N. Farnsworth

doi:10.1117/12.245240

24 July 1996 New approach to phase metrology for manufacturing 248-nm lithography-based embedded attenuated phase-shifting mask

Giang T. Dao, Gang Liu, Alan Snyder, Jeff N. Farnsworth

Author Affiliations +

Proceedings Volume 2793, Photomask and X-Ray Mask Technology III; (1996) https://doi.org/10.1117/12.245240
Event: Symposium on Photomask and X-Ray Mask Technology, 1996, Kawasaki City, Japan

Abstract

One of major benefits of attenuated phase-shifting mask, also called half-tone mask, over binary mask is the increase in depth-of-focus. This improvement, however, will be drastically reduced if phase error over the entire reticle is excessive. It is well known that phase error causes focal shift at the wafer level, leading to loss of useful depth of focus. Therefore, controlling phase error is critical in achieving good lithographic performance of embedded attenuated phase-shifting mask (EPSM). Most recently there are newly developed tools that can be used to measure phase at 248 nm wavelength. However, these tools can't measure phase of actual device patterns such as 0.25 xm contact holes due to beam size. This paper will present a new approach that directly measures focal shift of actual device patterns using Aerial Image Measurement. We have successfully utilized this approach in our development of EPSM reticle fabrication process leading to a focal shift uniformity of ≤ 0.2 μm over the entire 6" EPSM reticle. This new approach is also being used as a quality control tool in our mask fabrication process. New metrology pattern design will be described. Measurement accuracy and repeatability and data analysis methodology will be discussed.

Citation Download Citation

Giang T. Dao, Gang Liu, Alan Snyder, and Jeff N. Farnsworth "New approach to phase metrology for manufacturing 248-nm lithography-based embedded attenuated phase-shifting mask", Proc. SPIE 2793, Photomask and X-Ray Mask Technology III, (24 July 1996); https://doi.org/10.1117/12.245240

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