Impact of Planarization Sheet Addition on Full Wafer Printing Uniformity
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0961-O02-06
Impact of Planarization Sheet Addition on Full Wafer Printing Uniformity Tanguy Leveder1, Stefan Landis1, Laurent Davoust2, and Nicolas Chaix3 1 CEA\LETI - Minatec, 17, rue des martyrs, Grenoble, France 2 ENSHMG-LEGI, Grenoble, France 3 CNRS\LTM, 17, rue des martyrs, Grenoble, France
Abstract Uniformity of nanoimprint lithography has been quantitatively studied through the ability to replicate regular lines arrays by wafer-to-wafer imprint. Two statistic coefficients have been defined in order to quantify the local uniformity and the ability to identically imprint two similar areas respectively. Those coefficients enable to compare different imprint profiles in terms of uniformity and to point out the efficiency of soft layers insertion into the imprint stack. Introduction The International Technology Roadmap for Semiconductor (ITRS) trends predict constant downsizing of the features and improvement of electrical properties of nanoscale devices. Altough lower wavelength of optical sources or immersion techniques are proposed to improve capabilities of conventional projection lithographies, other approaches have been proposed for Next Generation Lithographies (NGL). Nanoimprint lithographies are now emerging as the longawaited disruptive technologies [1]. Many aspects of nanoimprint lithography, as resolution [2] or throughput [3] have been studied, and the non uniformity of imprinted patterns henceforth appears as an important issue. Non uniformities have been already studied [4, 5, 6]; especially in the case of residual thicknesses remaining in the case of pattern density variation [4, 5]. Ground-breaking answers like micro dispensing [7] were proposed. However, even in uniform pattern arrays, imprinted depths non uniformities are often observed, though they are more seldom reported [8]. To improve the imprint uniformity and reduce the number of imprinted defects, the Nanoimprint community usually insert soft material layer between the stamp and the applying-force system of the imprint tool (figure 1) leading to a significant improvement of imprints. This paper is a first quantitative analyze of the different imprint configurations (figure 1). In the first section we will see both which parameters are needed to quantify the imprint uniformity, and the experimental set-up. Then we will define two statistic coefficients which are used to quantify the uniformity at the die and at the wafer scale respectively. Finally, impact of soft material layer used into the imprint stack will be reported.
b a c Figure 1: sketch of considered imprint stack. The reference configuration (a) without any soft layer is compared with two stacks including either one (b), or two (c) soft layers.
Experimental section Studied configurations In this paper, we will focus on the uniformity of imprinted depths. Figures 2 show why this non uniformity could be distinguished either as a local defect, or as a global one.
Figure 2: Origin of studied non-uniformity. Influence of imprinted depth on pattern transfer. The first situatio
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