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20 March 2018 In-resist pattern shift metrology
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Scanner induced pattern shifts between layers are a large contributor to DRAM Bitline to Active overlay. One of the main root causes for this Pattern Shift non-Uniformity are lens aberrations. Currently measuring the Bitline to Active overlay requires a decap CDSEM method1. In this paper, an in-resist pattern shift uniformity metrology method is proposed which quantifies the main DRAM Bitline to Active overlay without the necessity to decap. We have designed a high transmission reticle (≥ 60%) to measure the pattern shift non-uniformity between two dense gratings under the rotation angle of the Active layer in both cold and hot lens states. Each module on the reticle contains product-like features and a variety of metrology targets, i.e. alignment and overlay, such that the product-to-product and the productto- metrology pattern shift fingerprints can be measured. OPC is applied to enlarge the overlapping process windows of the metrology targets with respect to the product-like features.
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Anita Bouma, Bart Smeets, Lei Zhang, Thuy T. T. Vu, Peter de Loijer, Maikel Goosen, Willem van Mierlo, Wendy Liebregts, and Bart Rijpers "In-resist pattern shift metrology", Proc. SPIE 10587, Optical Microlithography XXXI, 105871G (20 March 2018);

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