# Gate spacers etching of Si$_3$N$_4$ using cyclic approach for 3D CMOS devices

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Abstract : In this work, we optimize a CH$_3$F/O$_2$/He/SiCl$_4$ chemistry to etch silicon nitride gate spacers for 3D CMOS devices in a 300mm inductively coupled plasma reactor. The chemistry has high directivity and high selectivity to Si and SiO$_2$. A cyclic approach, which alternates this chemistry with a CH$_2$F$_2$/O$_2$/CH$_4$/He plasma, is investigated. Using $quasi\ in\ situ$ x-ray photoelectron spectroscopy and ellipsometry measurements, etching mechanisms are proposed to explain the results obtained. As a result of process optimization, silicon nitride spacers with vertical profile and a small critical dimension loss of 3 nm as well as complete spacers removal on sidewalls of the active area are obtained on 3D patterns, confirming the advantages of this approach.
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Submitted on : Tuesday, September 14, 2021 - 11:30:02 AM
Last modification on : Thursday, September 16, 2021 - 3:23:58 AM

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Valentin Bacquie, Aurelien Tavernier, Francois Boulard, Olivier Pollet, Nicolas Posseme. Gate spacers etching of Si$_3$N$_4$ using cyclic approach for 3D CMOS devices. Journal of Vacuum Science and Technology A, American Vacuum Society, 2021, 39, pp.033005. ⟨10.1116/6.0000871⟩. ⟨cea-03343549⟩

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