Studies On The Textured Surface Microstructure Of Mc-Si Wafers Etched By Acid Solutions

Mc-Si has been utilized widely in optoelectronic field. Surface texture has a great impact on the performance of optoelectronic devices. Therefore, This paper have studied up the textured surface microstructure of mc-Si wafers etched by acid solution, optimized the surface structure and improved the reflectivity of mc-Si wafer.Acidic solutions have been widely used for etching of silicon in mc-Si texturing field due to acidic etching is isotropic. This paper has studied up etching by traditional HF-HNO₃ solution, and found traditional acidic etching leading to many large shallow pits is ineffective. So the average ratio of reflectivity of etched mc-Si wafers is up to 31.7%. On this basis, this paper have found a solution replacing of HNO3 with NaNO2 as oxidizing agent that leads to comparable improvements in surface microstructure, and the pits like earthworms are deep, uniform, and high-density. So the surface reflectivity is down to 23.9%, 8% lower than traditional solution. But there are some deep and unfavorable grooves on the surface too.With further research, this paper creatively proposed two-steps method etching mc-Si. The principle of this method is to obtain high-density pits on mc-Si wafers etched by slow-etching solution, and deeper pits etched by fast-etching solution again. Through a lot of experiments, it proved that the method is feasible and effective. Firstly, high-density pits have been obtained with HF-NaNO₂ as slow-etching solution. Secondly, by means of HF-HNO₃-(NH₄)₂C₂O₂ as fast-etching solution, removing the last damaged layer, deepening pits and preventing disadvantageous grooves have achieved simultaneously. On this basis, this paper has optimized both of times and obtained a more ideal etching method. According to the experiments, this paper discovered that the surface etched by two-steps method randomly distributes many deep, uniform, high-density pits like earthworms and the reflectivity measured by experiments is 24.8%, 7% lower than traditional etching.