Optical rasterization algorithms for contrast devices utilizing different physical modulation principles in optical maskless lithography

Azat Latypov; Ronald Albright; Nabila BabaAli; Wenceslao A. Cebuhar; Jason D. Hintersteiner; Elizabeth Stone

doi:10.1117/12.600241

6 May 2005 Optical rasterization algorithms for contrast devices utilizing different physical modulation principles in optical maskless lithography

Azat Latypov, Ronald Albright, Nabila BabaAli, Wenceslao A. Cebuhar, Jason D. Hintersteiner, Elizabeth Stone

Author Affiliations +

Proceedings Volume 5751, Emerging Lithographic Technologies IX; (2005) https://doi.org/10.1117/12.600241
Event: Microlithography 2005, 2005, San Jose, California, United States

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.

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Azat Latypov, Ronald Albright, Nabila BabaAli, Wenceslao A. Cebuhar, Jason D. Hintersteiner, and Elizabeth Stone "Optical rasterization algorithms for contrast devices utilizing different physical modulation principles in optical maskless lithography", Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); https://doi.org/10.1117/12.600241

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