Since 1980, I have been working in the area of lithographic patterning for IC production - a most fascinating, interdisciplinary area. Some particular interests include advanced image formation, simulation, process control, metrology methods, data analysis, and EUV lithography.
I have a B.A. from Carleton College in 1975 and a doctorate from MIT in 1980, both in physics. Before joining ASML in 2019, I worked for GLOBALFOUNDRIES, IBM, Xerox PARC and Perkin-Elmer Corporation.
I have a B.A. from Carleton College in 1975 and a doctorate from MIT in 1980, both in physics. Before joining ASML in 2019, I worked for GLOBALFOUNDRIES, IBM, Xerox PARC and Perkin-Elmer Corporation.
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This paper provides a thorough experimental assessment of the implementation of vote-taking, and discusses its pro’s and con’s. Based on N=4 vote-taking, we demonstrate the capability to mitigate different types of mask defects. Additionally, we found that blending different mask images brings clear benefit to the imaging, and provide experimental confirmation of improved local CDU and intra-field CDU, reduction of stochastic failures, improved overlay, ... Finally, we perform dedicated throughput calculations based on the qualification performance of ASML’s NXE:3400B scanner.
This work must be seen in the light of an open-minded search for options to optimally enable and implement EUV lithography. While defect-free masks and EUV pellicles are without argument essential for most of the applications, we investigate whether some applications could benefit from vote-taking.
We use a double exposure method, previously described by Minghetti [1] et al. to isolate and measure intra-field overlay distortions caused by tool lens signatures and different illumination conditions. A full field test reticle is used to create a dual level expose pattern. The same pattern is exposed twice, but with two different illumination conditions. The first exposure is done with a standard reference illumination. The second exposure is the target illumination condition. The test reticle has overlay target pairs that are measurable when the 2nd exposure is offset in the Y direction by the designed amount. This allows for a high density, 13x13, intra-field overlay measurement to be collected and modeled to determine 2nd and 3rd order intra-field terms. Since the resulting illumination and scanner lens specific intra field corrections are independent of field size, the sub-recipes can be applied to any product exposure independent of field size, which use the same illumination conditions as the test exposures. When the method is applied to all exposure levels in a product build cycle, the overlay errors contributed by the reference illumination condition cancel out. The remaining errors are due exclusively to the impact of the illumination condition on that scanner lens.
Actual results correlated well with the model with more than 80% of the predicted overlay improvement being achieved.
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