Organic contamination of silicon wafers by buffered oxide etching

Abstract

Recently it has been shown that for present and future scales of integration in semiconductor devices even volatile organics have a strong negative impact on process yield and product performance. Therefore, new ultrasensitive analytical methods for the detection and identification of organic volatiles are needed in process control for monitoring and for failure analysis. Very promising in this field, especially for monitoring of ultrapure process gases, are methods involving atmospheric pressure ionization, like API-MS and IMS (ion mobility spectrometry). We present results from investigations into wafer contamination by wetting agents and surfactants that are used in buffered oxide etchings (BOE) and related processes. Depending upon the chemical class of the surfactant, considerably strong bindings are formed to the silicon surface. DI-water rinse is not able to remove the species. The residues strongly increase the tendency of the surface to adsorb particles and thus may lead to a higher defect density. On the other hand, only the persisting residues assure that the silicon surface remains wetted during following steps of processing. So the optimum selection of the surfactant is crucial to adjust parameters for etching and other wet processes.