2 June 2003 Dose and focus estimation using top-down SEM images
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As design rules shrink and process windows become smaller, strict process control is becoming increasingly important. The two primary process parameters in the photolithography process, exposure dose and focus, require strict control in order to maintain the photoresist profile. This paper presents the second stage of an approach towards monitoring the semiconductor photolithogprhay process by using critical dimension-scanning electron microscopy. In the former paper, we propsed a method that quantifies the photoresist pattern profile variation caused by dose or focus variation. In this paper, a new method for estimating the variation in exposure dose and focus is presented. Top-down SEM imagse are intrinsically limited in the inability to observe the re-entrant profile. This limitation has been overcome through the use of two tyeps of common patterns: island patterns and window patterns. Island patterns, such as isolated line patterns, have a tapered profile for negative defocus, while window patterns, such as isolated spaces patterns, have an inverse tapered profile for negative defocus. Using both types of patterns allows the focus deviation to be monitored, whether positive or negative defocus. The behavior of the two types of patterns is considered here based on photolithography simulation, and a new algorithm for estimating the exposure dose and focsu variation is proposed.
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Chie Shishido, Chie Shishido, Ryo Nakagaki, Ryo Nakagaki, Maki Tanaka, Maki Tanaka, Yuji Takagi, Yuji Takagi, Hidetoshi Morokuma, Hidetoshi Morokuma, Osamu Komuro, Osamu Komuro, Hiroyoshi Mori, Hiroyoshi Mori, } "Dose and focus estimation using top-down SEM images", Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003); doi: 10.1117/12.483673; https://doi.org/10.1117/12.483673

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