Fabrication of Silicon Nanowires by Metal-Assisted Chemical Etching Combined with Micro-Vibration

Abstract

In this work, we design a micro-vibration platform, which combined with the traditional metal-assisted chemical etching (MaCE) to etch silicon nanowires (SiNWs). The etching mechanism of SiNWs, including in the mass-transport (MT) and charge-transport (CT) processes, was explored through the characterization of SiNW's length as a function of MaCE combined with micro-vibration conditions, such as vibration amplitude and frequency. The scanning electron microscope (SEM) experimental results indicated that the etching rate would be continuously improved with an increase in amplitude and reached its maximum at 4 μm. Further increasing amplitude reduced the etching rate and affected the morphology of the SiNWs. Adjusting the vibration frequency would result in a maximum etching rate at a frequency of 20 Hz, and increasing the frequency will not help to improve the etching effects.

Keywords: MaCE; amplitude; etching rate; frequency; micro-vibration platform.

Figure 1

Equipment of micro-vibration platform; 1—Engine Bed; 2—Coil; 3—Armature; 4—Aluminum Plate; 5—Ball Bearing; 6—Spring; 7—Vibrating Rod; 8—Sensor.

Figure 2

Cross-sectional view SEM image of SiNWs with no vibration (a), and with the vibration at the amplitude of 2 μm (b), 4 μm (c), and 6 μm (d). The numerical values marked in green are 1.870 μm, 2.680 μm, 3.475 μm and 2.135 μm.

Figure 3

Etching mechanism model with no vibration (a), and with amplitudes of 2 μm (b), 4 μm (c), and 6 μm (d). The “+” in the figure represents a hole.

Figure 4

Etching rate of SiNWs at different amplitudes.

Figure 5

Plan view SEM image of SiNWs with no vibration (a), and with the vibration at the frequency of 20 Hz (b).

Figure 6

Plan view SEM image of SiNWs.

Figure 7

Etching mechanism model with frequencies of 20 Hz (a) and 40 Hz (b). The “+” in the figure represents a hole.