Determination of ultratrace metallic impurities in polysilane and siloxane polymers for microelectronic devices

Abstract

Ultratrace metallic elements in polysilane, siloxane and other such organic silicon compounds used in the fabrication of semiconductor devices are determined so as to understand their effects on the devices. Separating organic silicon by means of hydrolysis to SiO2 is a high sensitivity analysis. The established procedures involve dissolution of organic silicon compounds and the hydrolyzed products of organic silicon samples in hydrofluoric acid-containing reagents followed by evaporation of the silicon matrix as H2SiF6. The residual metallic elements in the treated sample solution were then determined by electrothermal atomic absorption spectrometry (ETAAS). The results indicated that a small amount of sulfuric acid was helpful in yielding SiO2 from organic silicon compounds, and that proper controls of the evaporation process are effective in preventing chemical interferences of some metallic elements during recovery and reproducible analysis. The methods developed were applied to the determination of metallic elements such as sodium, iron, and copper in various kinds of organic silicon compounds used for microelectronic devices. The limit of detection for seven metallic elements was as low as 0.1 ng g−1 levels.