• Angermann, H.; Laades, A.; Kegel, J.; Klimm, C.; Stegemann, B.: Improvement of silicon solar cell substrates by wet-chemical oxidation studied by surface photovoltage measurements. Solid State Phenomena 219 (2015), p. 291-296


Conventional strategies for wet-chemical pre-treatment are mainly based on concentrated solutions. Electronic interface properties can be enhanced by opti-mised sequences of surface oxidation in concentrated acids e.g. RCA I and II , H2SO4/H2O2, HNO3 68% and etching in HF-containing solutions (NH4F 40 % or HF 1 %). To minimise chemical consumption and the number of process steps, in this study also mixtures of ultra-pure deionized water (DiW) with dissolved ozone (O3) [ ] or hy-drochloric acid (HCl) [ ] were investigated as an alternative to RCA, HNO3 and H2SO4/H2O2 solutions. The aim of these investigations is to reach the comparable cleaning and passivation ef-fects, as achieved by conventional concentrated solutions, with a significant cost reduction. According to our results wet-chemical oxidation in diluted solutions of HCl [9] or ozone O3 [4] could be a high quality and low cost alternative to current approaches with liquid chemicals for the preparation of hydrophobic Si substrate surfaces and ultra-thin passivating oxide layers.