Process optimization of selective wet etching for fabrication of high-aspect-ratio and uniform multilayer grating reference materials

Longfei Zhang; Xingrui Wang; Xinbin Cheng; Xiao Deng

doi:10.1117/1.JMM.17.4.044003

5 December 2018 Process optimization of selective wet etching for fabrication of high-aspect-ratio and uniform multilayer grating reference materials

Longfei Zhang, Xingrui Wang, Xinbin Cheng, Xiao Deng

Author Affiliations +

Journal of Micro/Nanolithography, MEMS, and MOEMS, Vol. 17, Issue 4, 044003 (December 2018). https://doi.org/10.1117/1.JMM.17.4.044003

Abstract

Background: The multilayer gratings are considered as the potential length-standard-traceable lateral scales for calibrating the next-generation critical dimension scanning electron microscope (CD-SEM) magnification. As a key step in the fabrication of multilayer gratings, selective wet etching determines the final grating structure formation. However, the effects of the etching process parameters on the multilayer gratings in several nanometer scales have not been reported in detail. Aim: By optimizing the process of selective wet etching, we should fabricate high-aspect-ratio and uniform multilayer gratings to obtain high-contrast secondary electron signals and stable secondary electron images while also obtaining measurement accuracy from the small line edge roughness. Approach: Based on the analysis of the important factors in the etching process and SEM and TEM measurement results, we evaluate the effects of ultrasonic agitation, HF acid concentration, etch time, and linewidth scale on the aspect-ratio and uniform of multilayer gratings. Results: We recommend to etching the multilayer films with an HF acid concentration of about 2% during the ultrasonic agitation for uniformity. Moreover, selective wet etching reaction is limited by scale when the linewidth is below 20 nm. Despite the fact that the grating structure is fragile and easy to be broken down, for linewidths of about 10 and 5 nm, the aspect ratio of multilayer gratings can reach about 3 and 2, respectively. Conclusions: By focusing on the optimum conditions of ultrasonic agitation, HF acid concentration, and linewidth scale in the selective wet etching, selective wet etching can be used to fabricate high-aspect-ratio and uniform multilayer gratings with linewidth below 20 nm.

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Longfei Zhang, Xingrui Wang, Xinbin Cheng, and Xiao Deng "Process optimization of selective wet etching for fabrication of high-aspect-ratio and uniform multilayer grating reference materials," Journal of Micro/Nanolithography, MEMS, and MOEMS 17(4), 044003 (5 December 2018). https://doi.org/10.1117/1.JMM.17.4.044003

Received: 6 August 2018; Accepted: 14 November 2018; Published: 5 December 2018

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KEYWORDS

Etching

Multilayers

Wet etching

Ultrasonics

Signal processing

Line edge roughness

Scanning electron microscopy

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