Chemical analysis of acidic silicon etch solutions II. Determination of HNO(3), HF, and H(2)SiF(6) by ion chromatography.
The processing of silicon in microelectronics and photovoltaics involves the isotropic chemical etching using HF-HNO(3) mixtures to clean the surface from contaminations, to remove the saw damage, as well as to polish or to texture the wafer surface. Key element of an effective etch process control is the knowledge of the actual etch bath composition in order to maintain a certain etch rate by replenishment of the consumed acids. The present paper describes a methods for the total analysis of the etch bath constituents HF, HNO(3), and H(2)SiF(6) by ion chromatography. First step is the measurement of the total fluoride and nitrate content in the analyte. In a second step, H(2)SiF(6) is precipitated as K(2)SiF(6). After careful filtration of the precipitate, the fluoride concentration in the filtrate is measured and the content of free HF is calculated therefrom. The K(2)SiF(6) is dissolved again and the fluoride content measured and recalculated as H(2)SiF(6). The results obtained with the presented method are discussed with respect to the results from two other, previously published methods, based on a titration using methanolic cyclohexylamine solution as titrant and based on a method using a fluoride ion selective electrode (F-ISE). An evaluation with respect to the needs for an industrial application is given.
Acker
Jörg
J
Department of Biological, Chemical, and Process Engineering, Fachhochschule Lausitz, University of Applied Sciences, Grossenhainer Strasse 57, D-01968 Senftenberg, Germany; Leibniz-Institute for Solid State and Materials Research Dresden (IFW Dresden), P.O. Box 270016, D-01171 Dresden, Germany.
Henßge
Antje
A