Simple method to measure the etching rate of monocrystalline silicon in KOH solution Cheng Chen, Liang Jiang, Peng Zhang, Hongbo Wang, Linmao Qian ✉ Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, People’s Republic of China ✉ E-mail:
[email protected] Published in Micro & Nano Letters; Received on 22nd August 2017; Revised on 23rd November 2017; Accepted on 18th December 2017
A simple and low-cost method is proposed to measure the etching rate of monocrystalline silicon in KOH solution with various pHs through atomic force microscopy. The native oxide on the silicon surface is applied as a mask film to achieve selective etching. A quadrate-part area of the native oxide on silicon substrate surface is removed through the non-destructive tribochemical removal of the SiO2 microsphere. As a result, the fresh subsurface silicon is exposed and etched smoothly. The adjacent remaining native oxide is hardly etched by the KOH solution. After etching in KOH, a step forms at the boundary between the remaining native oxide layer and exposed silicon surface. The atomistic-precision measurement of atomic force microscopy can detect a tiny etching depth of silicon, thereby acquiring the accurate etching rate in the KOH solution. This method provides a new and simple concept to measure the etching rate of materials in a suitable etchant and afford high-precision measurement to the etching rate required in the design of a material etching process.
1. Introduction: Anisotropic wet chemical etching of monocrystalline silicon is one of the key techniques in the fabrication of silicon microstructures for integration circuits (ICs), micro-electromechanical systems (MEMS), and other microstructures [1–4]. KOH is the most widely used anisotropic etchant in silicon etching for the fabrication of silicon microstructures [5, 6]. When designing an etching fabrication process, the etching rate of silicon in a KOH etchant must be known, thereby enabling a smooth and accurate etching process [7, 8]. As a result, a fine three-dimensional microstructure of silicon can be obtained. The microminiaturisation of functional silicon structures requires increased attention nowadays for enhanced development of IC, MEMS, and other fields, which requires strict control over the etching process and ensures precise material etching removal. For silicon microstructures in IC and MEMS, the accuracy of a structure should be at the nanometre scale to ensure optimum functional properties. A slow, precise, and controllable etching rate of silicon is the prerequisite during the micro etching process in KOH etchant, which can ensure a nanometre-scale etching depth (
