MC-Si Wafers - Wet Etching

MC-Si Wafers - Wet Etching

Material Name: MC-Si wafers
Recipe No.: 10309
Primary Chemical Element in Material: Si
Sample Type: Wafer
Uses: Etching
Etchant Name: None
Etching Method: Wet etching
Etchant (Electrolyte) Composition: The traditional p-type multi-wire slurry sawn mc-Si wafers (180-µm-thick, 156x 156 mm2) were supplied by Linuo Solar Power Holdings Co., Ltd. The wafers were divided into four groups (a, b, c and d). The four groups of samples were treated separately to form different surface structures, which are shown as follows. In order to emphasize application significance, the etching solutions were made according to chemical compositions used in the production process of the black silicon.

a: As-cut wafer sample with mechanical damages layer resulted from the wafer cutting.
b: Polished in a mixed acid solution (V/V: 70% HNO3: 49% HF= 6:1) for 3 min at room temperature.
c: Etched (textured) in a mixed solution (V/V: 70% HNO3: 49% HF: DI-water= 4:1:2) for 3 min at 8°C to obtain the micro-structured surface. The etched samples are called RENA textured wafer hereafter.
d: Micro-nano etched (textured) using MACE. Sample of Group c was chosen as a substrate and textured using MACE. Silver nanoparticles were electrolessly deposited on the silicon wafers in a solution of 8 mM/L AgNO3 and 4 vol.% HF for 15 s at room temperature. Nanoporous silicon was formed in a solution (V/V: 30% H2O2: 49% HF: DI-water= 2:2:7) for 60 s at room temperature. In this work, the surface of Sample d is called a micro-nano textured surface hereafter.

During surface treatment of the samples, the samples were rinsed two times in deionized water (DIW) at room temperature after the polishing or etching.
Before the contact angle measurements, all samples were immersed in 5 vol.% HF for 60 s at room temperature to remove the SiO2 layer formed in air and rinsed two times in deionized water (DIW) at room temperature. The SL1000 automatic contact angle meter was used to test the contact angle of all samples; the surface morphologies of samples were analyzed by means of OLS4000 confocal lasers scanning microscope (CLSM) and S4800 scanning electron microscope (SEM).
Procedure (Condition): No data
Note: In order to investigate the wettability of multicrystalline silicon (mc-Si) with the etching solutions during metal-assisted chemical etching process, different surface structures were fabricated on the p-type multi-wire slurry sawn mc-Si wafers, such as as-cut wafers, polished wafers, and wafers etched in different solutions. The contact angles of different etching solutions on the surfaces of the wafers were measured. It was noted that all contact angles of etching solutions were smaller than the corresponding ones of deionized water, but the contact angles of different etching solutions were quite different. Among the contact angles of the etching solutions of AgNO3-HF, H2O2-HF, TMAH and HNO3-HF, the contact angle of TMAH solution was much larger than the others and that of HNO3-HF solution was much smaller. It is suggested that the larger contact angle may lead to an unevenly etching of silicon wafer due to the long retention of big bubbles on the wafers in the etching reaction, which should be paid attention to and overcome.
Reference: Y C Niu, et al., The wettability between etching solutions and the surface of multicrystalline silicon wafer during metal-assisted chemical etching process, 2017 IOP Conf. Ser.: Mater. Sci. Eng. 167 012015, (http://iopscience.iop.org/1757-899X/167/1/012015).