Eci Technology, Inc.

Guang Liang

Eugene Shalyt

Peter Bratin

Methods and apparatuses for selective monitoring of multiple silicon compounds in etchant solutions are provided. Methods can include reacting a test solution comprising a plurality of different silicon compounds with a fluoride-based compound in several conditions to provide different silicon:reagent binding ratios. One of the conditions can include the addition of a co-solvent to the test solution. Concentrations of the multiple silicon compounds can be determined based on the different binding ratios of silicon:reagent. Methods can further include a measuring method such as silicon elemental analysis or measuring of functional groups of a certain silicon form of a first portion of a test solution comprising a plurality of different silicon compounds and reacting a second portion of the solution with a fluoride-based compound to provide a silicon:reagent binding ratio. Concentrations of the multiple silicon compounds can be determined based on the measuring method and binding ratio measurements.

Selective monitoring of multiple silicon compounds

Silicon ions in an alkaline etchant solution are analyzed by acidifying a sample of the etchant solution, adding fluoride ions in excess of the concentration required to react with all of the silicon ions, and using a fluoride ion specific electrode (FISE) to detect free fluoride ions in the resulting test solution. Good sensitivity and precision are provided by using a relatively acidic test solution and only a slight excess of fluoride ions, and limiting the analysis range to the maximum expected silicon concentration in the etchant solution.

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