1 April 2005 Intensity imbalance in phase shift masks and correction by multiple exposures
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In this paper, the issue of intensity imbalance in an alternating phase shift mask has been studied for hole patterns with pitches 300 nm and below. A method of processing is developed, which would nullify the effects of phase errors that cause focus dependent difference in the sizes of holes belonging to opposite phases. This method uses two exposures with opposite foci. Using this method, the effect of the focus on the difference in the size of holes from opposite phases could be totally eliminated. It also changes the nature of the focus curve, bringing a significant improvement in the depth of focus without affecting exposure latitude and mask error enhancement factor. The method works quite effectively for all the via pitches, however, some constant size difference existed across focus, that is easily correctable by biasing one phase with respect to the other. It was also found that this technique could bring remarkable immunity against the lens aberrations such as defocus and astigmatism.
© (2005) Society of Photo-Optical Instrumentation Engineers (SPIE)
Moitreyee Mukherjee-Roy, Moitreyee Mukherjee-Roy, Navab Singh, Navab Singh, Sohan Singh Mehta, Sohan Singh Mehta, Yasuki Kimura, Yasuki Kimura, Hideki Suda, Hideki Suda, Kazunori Nagai, Kazunori Nagai, } "Intensity imbalance in phase shift masks and correction by multiple exposures," Journal of Micro/Nanolithography, MEMS, and MOEMS 4(2), 023004 (1 April 2005). https://doi.org/10.1117/1.1898043 . Submission:


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