Comparison of clear-field and dark-field images with optimized masks

Robert Sinn; Thuc Dam; Bob Gleason

doi:10.1117/12.879533

22 March 2011 Comparison of clear-field and dark-field images with optimized masks

Robert Sinn, Thuc Dam, Bob Gleason

Proceedings Volume 7973, Optical Microlithography XXIV; 79731V (2011) https://doi.org/10.1117/12.879533
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

Clear-field photo-masks offer significant advantages over dark-field photo-masks for some important classes of target patterns, including small isolated features and dense arrays of contacts. This work compares lithographic performance of clear-field and dark-field images when mask patterns are optimized for respective mask tones. Since the purpose is to study optical behavior, computed images without resist models were compared. In order to explore performance limits, optimized masks were not constrained to limit their complexity. Calculated images were compared for clear-field and dark-field masks, with either opaque or 6% transmission, 180-degree phase-shifted absorbers. In each case, mask patterns were independently optimized to print the targets, which were a set of square and rectangular arrays of contact holes with various dimensions and pitches. The range of the target patterns extended to the limits of ArF resolution with water immersion. Because the intent was to compare inherent optical performance of positive and negative-tone imaging, the study did not use resist models that would combine materials properties or behaviors into the results, but simply applied a constant threshold to calculated intensities to obtain images. Contrast, MEEF, and deviation of images with defocus were the basis of optimizing the mask patterns, and were compared for the four combinations of mask tones and absorbers. Best contrast and MEEF were obtained with bright-field masks that had attenuated, phase-shifting absorbers. The amount of improvement depended on the size of the mask patterns relative to that of their corresponding targets, set here by varying the intensity threshold for the images during mask optimization. Differences in how the images of the four types of masks changed with defocus were statistically insignificant.

Citation Download Citation

Robert Sinn, Thuc Dam, and Bob Gleason "Comparison of clear-field and dark-field images with optimized masks", Proc. SPIE 7973, Optical Microlithography XXIV, 79731V (22 March 2011); https://doi.org/10.1117/12.879533

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available