1 June 1990 Alignment performance of a 0.6-NA 364-nm laser direct writer
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Abstract
Alignment performance data is presented on a high resolution laser scanning lithography system. The alignment system is a through-the-lens on-axis design which features multiple optical paths such as bright-field and dark-field illumination and high and low magnification legs. Total system overlay is better than 0. 10 tm. 1. DW ALIGNMENT REQUIREMENTS Translating design data into patterned photoresist on wafers typically requires two lithographic steps. First data is transferred to a mask or reticle using either a laser scanning tool such as the ATEQ CORE-2500 or an e-beam system. Next the patterned mask or reticle is projected onto a wafer coated with resist. Throughout this paper I shall refer to systems which use two lithographic steps to transfer a pattern as Indirect Writers (1W). This is in contrast to Direct Writers (DW). As the name implies a DW patterns a wafer without the need for creation of a mask or reticle. 1W alignment systems must accurately register a wafer pattern to a reticle pattern. The most straightforward technique is to directly reference the reticle to the wafer through the projection lens. This approach eliminates baseline problems. 1W alignment systems require high precision. However since they have a reticle to reference (either directly or indirectly) absolute accuracy is not required. Measurements (alignments) are concerned only with the relative offset of the projected reticle image to a pattern on the wafer. The alignment system
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael J. Bohan, Michael J. Bohan, "Alignment performance of a 0.6-NA 364-nm laser direct writer", Proc. SPIE 1264, Optical/Laser Microlithography III, (1 June 1990); doi: 10.1117/12.20215; https://doi.org/10.1117/12.20215
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