Article ID Journal Published Year Pages File Type
1245903 Talanta 2007 5 Pages PDF
Abstract

In the photovoltaic industry the etching of silicon in HF/HNO3 solutions is a decisive process for cleaning wafer surfaces or to produce certain surface morphologies like polishing or texturization. With regard to cost efficiency, a maximal utilisation of etch baths in combination with highest quality and accuracy is strived. To provide an etch bath control realised by a replenishment with concentrated acids the main constituents of these HF/HNO3 etch solutions including the reaction product H2SiF6 have to be analysed. Two new methods for the determination of the total fluoride content in an acidic etch solution based on the precipitation titration with La(NO3)3 are presented within this paper. The first method bases on the proper choice of the reaction conditions, since free fluoride ions have to be liberated from HF and H2SiF6 at the same time to be detected by a fluoride ion-selective electrode (F-ISE). Therefore, the sample is adjusted to a pH of 8 for total cleavage of the SiF62− anion and titrated in absence of buffers. In a second method, the titration with La(NO3)3 is followed by a change of the pH-value using a HF resistant glass-electrode. Both methods provide consistent values, whereas the analysis is fast and accurate, and thus, applicable for industrial process control.

Related Topics
Physical Sciences and Engineering Chemistry Analytical Chemistry
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