3D Patterning of Si by Contact Etching With Nanoporous Metals

Frontiers in Chemistry

Sylvain Le Gall¹  Dmitri Yarekha²  Mathieu Halbwax²  Joseph Harari²  Jean-Pierre Vilcot²  Vincent Magnin²  Encarnacion Torralba³  Elias Mpogui³  Christine Cachet-Vivier³  Stéphane Bastide³ 

[1] Group of Electrical Engineering of Paris (GeePs), CNRS, Centralesupelec, Univ. Paris-Sud, Sorbonne Université, Gif sur Yvette, France;Institut d'Électronique de Microélectronique et de Nanotechnologie (IEMN), UMR 8520, Université de Lille, Villeneuve d'Ascq, France;Institut de Chimie et des Matériaux Paris-Est (UMR 7182), CNRS, UPEC, Université Paris Est, Thiais, France;

关键词: silicon;    nanoporous gold;    imprinting;    MACE;    contact etching;    patterning;   

DOI  :  10.3389/fchem.2019.00256

来源: DOAJ

【 摘 要 】

Nanoporous gold and platinum electrodes are used to pattern n-type silicon by contact etching at the macroscopic scale. This type of electrode has the advantage of forming nanocontacts between silicon, the metal and the electrolyte as in classical metal assisted chemical etching while ensuring electrolyte transport to and from the interface through the electrode. Nanoporous gold electrodes with two types of nanostructures, fine and coarse (average ligament widths of ~30 and 100 nm, respectively) have been elaborated and tested. Patterns consisting in networks of square-based pyramids (10 × 10 μm2 base × 7 μm height) and U-shaped lines (2, 5, and 10 μm width × 10 μm height × 4 μm interspacing) are imprinted by both electrochemical and chemical (HF-H2O2) contact etching. A complete pattern transfer of pyramids is achieved with coarse nanoporous gold in both contact etching modes, at a rate of ~0.35 μm min−1. Under the same etching conditions, U-shaped line were only partially imprinted. The surface state after imprinting presents various defects such as craters, pores or porous silicon. Small walls are sometimes obtained due to imprinting of the details of the coarse gold nanostructure. We establish that np-Au electrodes can be turned into “np-Pt” electrodes by simply sputtering a thin platinum layer (5 nm) on the etching (catalytic) side of the electrode. Imprinting with np Au/Pt slightly improves the pattern transfer resolution. 2D numerical simulations of the valence band modulation at the Au/Si/electrolyte interfaces are carried out to explain the localized aspect of contact etching of n-type silicon with gold and platinum and the different surface state obtained after patterning. They show that n-type silicon in contact with gold or platinum is in inversion regime, with holes under the metal (within 3 nm). Etching under moderate anodic polarization corresponds to a quasi 2D hole transfer over a few nanometers in the inversion layer between adjacent metal and electrolyte contacts and is therefore very localized around metal contacts.

【 授权许可】

Unknown