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Proceedings Paper

Optical rasterization algorithms for contrast devices utilizing different physical modulation principles in optical maskless lithography
Author(s): Azat Latypov; Ronald Albright; Nabila BabaAli; Wenceslao A. Cebuhar; Jason D. Hintersteiner; Elizabeth Stone
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Paper Abstract

In Optical Maskless Lithography (OML), the die pattern to be printed is generated by a contrast device known as Spatial Light Modulator (SLM), consisting of a multitude of pixels. Each pixel is independently actuated so as to change its optical properties. Different physical principles can be used to modulate the light. For instance, liquid crystal pixels can be used to vary the amplitude transmittance of a pixel, or mirrors actuated by tilting or pistoning can be used to vary the amount of light from each pixel reaching the image plane. Optical rasterization is an algorithm that, given the description of the pattern to be printed (e.g. a GDSII mask file), computes the states (e.g. pixel transmittance or pixel micro-mirror tilt / piston) of the contrast device pixels that will reproduce the pattern at an optical image plane. The purpose of this paper is to present the Global Optimization (GO) rasterization algorithm based on matching the pupil field generated by the given mask, taking into account the constraints dictated by the modulation principle of the contrast device. In particular, we discuss a relation of GO algorithm and a grid filter approach to rasterization in Maskless Lithography. Also, a global optimization algorithm allowing the minimization of light loss is formulated and discussed. We present simulated results of lithographic patterns at the 65 nm node imaged using both tilt mirror and piston mirror contrast devices. In contrast with the previously reported work, we demonstrate that for a particular case of an SLM with piston mirror pixels, the presented GO rasterization algorithm results in aerial images that do not exhibit placement drift with defocus. The variations in the rasterization procedure needed to account for contrast devices with different physical modulation principles are discussed.

Paper Details

Date Published: 6 May 2005
PDF: 12 pages
Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); doi: 10.1117/12.600241
Show Author Affiliations
Azat Latypov, ASML (United States)
Ronald Albright, ASML (United States)
Nabila BabaAli, ASML (United States)
Wenceslao A. Cebuhar, ASML (United States)
Jason D. Hintersteiner, ASML (United States)
Elizabeth Stone, ASML (United States)

Published in SPIE Proceedings Vol. 5751:
Emerging Lithographic Technologies IX
R. Scott Mackay, Editor(s)

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