Controllable fabrication and mechanism study of textured ultra-thin silicon wafers via one-step Cu-assisted chemical etching

In this paper, the one-step Cu-assisted chemical etching method is reported for controllable thinning and texturization on mono-crystalline silicon in Cu2+/HF/H2O2 mixture solution. HF and Cu2+ exhibited a synergetic effect on accelerating etching process while H2O2 slowed down the preferential Si (100) etching by oxidizing the Cu atoms. Within optimal 0.15 M Cu2+/4 M HF/0.88 M H2O2 solution, quasi-inverted pyramid-like structures of 2-4 mu m in size and a reflectance of 8.46% were obtained at 20 degrees C. By adjusting the temperature and etching time, ultra-thin silicon wafers with thickness of 19-120 mu m were fabricated. Comparing the microstructures obtained at 20 degrees C and 60 degrees C, widths and inclination angles were distinct. By illustrating the transportation and distribution of holes during the etching process, the intrinsic connection between thinning and texturization was studied. The etching results, including etching rates and morphologies, were determined by the distribution of holes between the B' and B '' orbitals. In summary, controllable fabrication of textured ultra-thin silicon wafers with desired thickness and microstructures could be achieved by one-step, short-time and low-temperature Cu-assisted chemical etching method, exhibiting a great potential use in ultra-thin silicon solar cells.