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20 March 2019 Ultrahigh selective etching of Si3N4 over SiO2 using plasma-less dry process for 3D-NAND device applications
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Abstract
This study provides a new chemistry composition as an effective etchant with a plasma-less dry process for selectively etching Si3N4 to SiO2 with selectivity over 200. Both blanket and patterned wafers were examined. To investigate the parameters affecting selectivity, blanket wafers were tested. Etch rate and selectivity can be optimized by tuning the etchant concentration, chamber temperature and chamber pressure. The selectivity can be tuned from 10 to over 200 depending on the testing condition. It was found nearly etch stop of SiO2 with increasing the etching time, leading to higher selectivity with increasing the processing time. Under the optimized condition, etching rates of Si3N4 > 30 nm/min and SiO2 < 0.2 nm/min were obtained. It was also demonstrated on 3D-NAND patterned wafers of ONON stacked layer with pre-etched holes. The Si3N4 layers can be removed with lateral etching rate >20 nm/min, while maintaining the SiO2 layer.
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Chih-Yu Hsu, Peng Shen, and Nathan Stafford "Ultrahigh selective etching of Si3N4 over SiO2 using plasma-less dry process for 3D-NAND device applications", Proc. SPIE 10963, Advanced Etch Technology for Nanopatterning VIII, 109630M (20 March 2019); https://doi.org/10.1117/12.2504426
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