From Event: SPIE Advanced Lithography, 2019
The read performance of a spin-transfer torque magnetic random-access memory device is based on the tunnel magnetoresistance of the magnetic tunnel junction cell, which is a function of the resistance values at low and high resistance states of the magnetic layers. To ensure a robust tunnel magnetoresistance value and high yield, magnetic tunnel junction pillar patterning process should have a good local critical dimension uniformity. In this paper, we screen several patterning techniques, such as dry development rinse material-based tone reversal besides the standard patterning, as well as different resists and underlayer materials to improve the local critical dimension uniformity at 50nm pitch extreme ultraviolet pillar printing. The results of the best litho process obtained show an improvement above 20% for the local critical dimension uniformity performance. The performance metrics such as the process windows analysis, pillar circularity and the critical dimension uniformity have also been checked for the promising litho process options. Moreover, the transfer of the post-litho improvements to the etch process have been checked and qualified after several layers of hardmask etch.
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Murat Pak, Davide Crotti, Farrukh Yasin, Monique Ercken, Sandip Halder, Danilo De Simone, Pieter Vanelderen, Laurent Souriau, Hubert Hody, and Gouri Sankar Kar, "LCDU optimization of STT-MRAM 50nm pitch MTJ pillars for process window improvement," Proc. SPIE 10957, Extreme Ultraviolet (EUV) Lithography X, 109570R (Presented at SPIE Advanced Lithography: February 27, 2019; Published: 26 March 2019); https://doi.org/10.1117/12.2515023.