Paper
20 August 2004 Advanced mask pattern correction method of alternating PSM: improvement of line width uniformity in the shifter length direction
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Abstract
We have developed a new pattern correction method to improve the uniformity of gate width and thus transistor characteristics. It is well known that the width of the gate pattern as exposed with an alternating phase shift mask (alt-PSM) varies along the gate width direction, owing to the optical-intensity maxima within the phase shifter regions on both sides of the gate. Since the positions of the maxima depend on the shifter height, the pattern pitch and the illumination conditions (σ and NA), the degree of distortion of the gate length also depends on these factors. We have found that the optimal segment size for optical proximity correction (OPC) of gate distortion also depends on the above factors and should be determined by simulation prior to OPC. From our simulations, shorter segments do not necessarily lead to higher correction accuracy, and the optimal size is strongly related to the degree of distortion. Based on these observations, we propose a novel correction method, in which the look-up table of optimal segment size as a function of shifter height and pattern pitch is referred to in the model-based OPC flow. The advantage of the method has been shown by comparing the correction results to those from the ordinary model-based method, with the latter focusing on the line-end regions where the distortion effects are most remarkable.
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Masamichi Yoshida, Ken Ozawa, Kazuhisa Ogawa, and Hidetoshi Ohnuma "Advanced mask pattern correction method of alternating PSM: improvement of line width uniformity in the shifter length direction", Proc. SPIE 5446, Photomask and Next-Generation Lithography Mask Technology XI, (20 August 2004); https://doi.org/10.1117/12.557800
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KEYWORDS
Optical proximity correction

Distortion

Image segmentation

Model-based design

Critical dimension metrology

Phase shifts

Photomasks

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