Study of porous silicon surface by mass spectroscopy methods

Abstract

Silicon surfaces of multicrystalline substrates before and after the formation of porous silicon on them, used in the production of photovoltaic cells were studied by mass spectrometry methods. An analysis of the elemental surface composition by mass spectroscopy of secondary ions at various manufacturing stages, including before and after electrochemical etching to create a porous silicon layer was conducted in the research. Clean surfaces before etching in an electrolyte based on hydrofluoric acid (HF: C 2 H 5 OH=10:1) were compared with surfaces after the etching process, both at secondary ion spectra, and in 2D-ion images of the multicrystalline substrate surface that have been obtained on the mass-spectrometer TOF5 SIMS using a current of secondary ions CH 3 +. In particular, the presence of ion CH 3 +, which can saturate the dangling bonds of the porous silicon surface, obtained due to the electrochemical technology using etchant solutions based on hydrofluoric acid with the addition of ((CH 3 ) 2 NCOH) was checked. As can be seen from the above mass spectroscopy spectra, both oxygen complexes and hydrogen bonds are present on a clean silicon surface before etching. As shown in the 2D-ion image of the sample surface, the surface of the etched silicon contains a large number of secondary ions CH 3 +. This is also evident from the spectra of secondary ion emission of the silicon surface before and after etching.