A Study Of Stability Of Vapor Etching Texturization Of Diamond Wire Sawn Multicrystalline Silicon Wafers And Its Control

Conventional acid etching technology for texturization of multicrystalline silicon wafers failed with the diamond wire sawn multicrystaliine silicon wafers. Vapor etching technology is expected to solve this problem. But its stability is not so well.Based on our previous work in vapor etching texturization of diamond wire sawn multicrystalline silicon wafers, In order to solve the stability between a batch of continuous etching and the etch effect of each sample, the effects of repeated utilizations of the vapor source acid on the stability of the thermal evaporation-based vapor etching texturization, and the effect of temperature control on the morphology and stability of the texturization, were investigated in the present work. We developed a two-stage heating method for the temperature control, with the first stage at low temperature and the second stage at high temperature, replacing the previous constant temperature heating. It improved both the structure and the stability of the textures.The mechanisms for such improvement were analyzed and discussed.The result show that in the current small experimental device, the vapor source acid repeated use effect can keep stable in the continuous etching of 10 pieces of silicon. The etching effect of initial 1 to 2 silicon wafer is not ideal, we hold that the high water vapor content in acid vapor lead to the poor etching ability. The acid vapor is in steady state after the first use of repeated continuous process, leading to the texturization effect of silicon wafer is stable. After 10 times of continuous etching, the etching ability of acid vapor is decreased because of the cost of acid composition.After static cooling of gas source acid, the acid vapor is under reflux-cooling, and the acid composition is recovered, It still has a certain etching effect. It is showed that the acid vapor can be recovered and recycled.With two stage heating method in vapor etching, the microstructure of secondary corrosion pits can be formed on the surface of the etched silicon, the consistency and uniformity of the microstructure have been improved..In the first stage of the process of silicon etching, the large corrosion pits is formed due to the low holdingtemperature of silicon; in the second stage of the process of silicon etching, the small corrosion pits is formed on the basis of large corrosion pits due to the high holding temperature of silicon. The ideal microstructure of secondary corrosion pits not only has the advantages of quick removal of silicon wafer surface damage layer at low temperature reaction stage, but also has the advantage of reduction of reflectivity at the high temperature reaction stage. The secondary corrosion pits formed at the high temperature reaction stage improving the overall consistency of the microstructure on the surface of etched silicon. Two stage heating method can be an effective control method to improve the stability of the vapor etching.The best temperature in the low-temperature stage can be chosen from 65 ?-80?,with different temperature the selection of heating duration is in 1-3mins.The best temperature at high-temperature stage is about 90?, and the best duration is about 5min.The best heating rate is different when the temperature differences,but the best heating time is about 2min. If the effect of low-temperature stage is too strong,the surface of the etched silicon will remain large droplets after reaction,texturization of silicon wafer was polished, and the reflectivity can not be reduced. If the effect of high-temperature is not enough, the microscale corrosion pits can only form in bottom of some large corrosion pits which formed in low-temperature stage,and the effect of reduce reflectivity is also not enough.This study found the effect of repeated use of gas source acid and the reutilization character of acid vapor, we can control of the stability between a batch of continuous etching. We also found the two stage heating method can be a good control method of the etch effect in vapor etching and explain why the secondary corrosion pits can be form. These studies have important reference value for the further research and popularization of the future vapor etching method.