Proposal of a Next-Generation Super Resolution Technique

Abstract

A super resolution technique has been developed in order to support next-generation devices. We found that the super resolution technique was effective for smaller patterns but not for larger ones, leading to the restriction of its applicability. In order to obtain wider applicability, we propose a new optical system which has been improved and is applicable to all kinds of mask patterns. According to the proposed optical system, the mask pattern produces a specific source shape preferable for the mask pattern itself. Then the mask pattern is illuminated by this self-optimized illumination source. Thus optimal improvements can be obtained under the same illumination conditions, even if conventional patterns and phase-shift patterns of spatial frequency modulation types and diffracted amplitude modulation types are on the same photomask. Consequently, the super resolution technique will be brought into full use by this optical system.

Experimental and simulated estimation of new super resolution technique

“…Using a clear region of the mask, one level offset was calibrated. 8 Accordingly, previous simulation results are supported by this experiment. By subtracting the flare and normalizing to the clear region intensity, we obtained the relative image profile.…”

“…1͑b͒ ͑reflection type͒. 8 In all cases the second source is the modified illumination. Passing through the first mask with the modified illumination, the UV light forms a specific source shape on the third source.…”

Evaluation of a two-mask resolution enhancement technique

“…This RET automatically provides an illumination that is different for every feature on the reticle ͑M2͒ but has the weakness that all features on the first mask ͑M1͒ must be illuminated in the same way, i.e., the illumination of the first mask can be adjusted to improve some features, but not all. 2 The alignment accuracy and/or lens distortion between the first mask and the reticle are of critical importance in such a system, and according to Kamon et al 3 acceptable imagery requires alignment to an absolute accuracy of order 0.1 m. Furthermore, a system employing a two-mask RET is estimated to cost 1.5-2 times more than a normal projection camera.…”

T-top forming simulation using percolation theory

“…[1][2][3][4][5][6][7][8][9][10][11][12] Chemically amplified resists are widely used in KrF or ArF lithography. In order to overcome limitations in photolithography, many researchers are making good efforts in surface imaging or ArF resist processing.…”