Fabrication of high aspect ratio silicon gratings by interference lithography and potassium hydroxide anisotropic etch technique

Yanchang Zheng; Keqiang Qiu; Xiaolong Jiang; Qingbo Wang; Lixiang Wu; Lali Bi; Yilin Hong

doi:10.1117/12.2058669

28 August 2014 Fabrication of high aspect ratio silicon gratings by interference lithography and potassium hydroxide anisotropic etch technique

Yanchang Zheng, Keqiang Qiu, Xiaolong Jiang, Qingbo Wang, Lixiang Wu, Lali Bi, Yilin Hong

Author Affiliations +

Proceedings Volume 9170, Nanoengineering: Fabrication, Properties, Optics, and Devices XI; 917018 (2014) https://doi.org/10.1117/12.2058669
Event: SPIE NanoScience + Engineering, 2014, San Diego, California, United States

Abstract

The authors report a new process combining interference lithography with potassium hydroxide (KOH) anisotropic etch technique for fabrication of high aspect ratio silicon gratings on (110) oriented silicon wafers. This new process has the ability in fabricating high aspect ratio silicon gratings with extremely smooth sidewalls over a large sample area. An alignment method was developed to align interference fringes to the vertical (111) planes of (110) oriented wafers. In addition, a room temperature etch process with 50 wt % KOH solution was chosen to finally get an etch anisotropy of 188. Better etch uniformity was achieved by adding a surfactant to the aqueous KOH to promote the release of hydrogen bubbles. To increase latitude in KOH etching process, deposition of aluminum under a sloped angle with respect to the grating structures was utilized to obtain a high duty cycle nitride mask. To prevent the collapse of high aspect ratio grating structures caused by surface tension, a liquid carbon dioxide supercritical point dryer was used in the drying process. The authors successfully fabricated 320nm period gratings with aspect ratio up to 100 on 5-μm-thick silicon membranes on (110) oriented silicon-on-insulator wafers. The sample area is about 50 mm × 60 mm. The roughness (root mean square) of the sidewall is about 0.267 nm.

Citation Download Citation

Yanchang Zheng, Keqiang Qiu, Xiaolong Jiang, Qingbo Wang, Lixiang Wu, Lali Bi, and Yilin Hong "Fabrication of high aspect ratio silicon gratings by interference lithography and potassium hydroxide anisotropic etch technique", Proc. SPIE 9170, Nanoengineering: Fabrication, Properties, Optics, and Devices XI, 917018 (28 August 2014); https://doi.org/10.1117/12.2058669

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