Photolithography is the critical step in realizing a smaller feature size of Integrated Circuits (IC). Manufacturing beyond the 30 [nm] node requires tighter focus budgets in ArF immersion lithography systems [1]. Wafer non-flatness and lens heating are main focus-budget contribu
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Photolithography is the critical step in realizing a smaller feature size of Integrated Circuits (IC). Manufacturing beyond the 30 [nm] node requires tighter focus budgets in ArF immersion lithography systems [1]. Wafer non-flatness and lens heating are main focus-budget contributors [2, 3]. Their contribution can be reduced by exposing the wafer with a curved instead of the conventional flat focal plane (Figure 1). This effect is achieved by manipulating the photomask curvature during the exposure process. A piezoelectric actuation system has been developed for this purpose which can control the photomask curvature [4]. This paper revisits the actuation principle and presents the experimental validation of the concept in a functional model.@en
