BEHAVIOR OF POLYETHYLENE OXIDE-BASED NONIONIC SURFACTANTS IN SILICON PROCESSING USING ALKALINE-SOLUTIONS

The adsorption of polyethylene oxide (PEO) based nonionic surfactants onto hydrophobic silicon from an alkaline solution was investigated us ing an in situ attenuated total reflection Fourier transform infrared spectroscopy technique. The adsorption/desorption profiles of surfacta nts were affected by the type and length of the hydrophobic group and the lengths of hydrophilic PEO chains. Complete wetting of hydrophobic silicon was measured at surfactant concentrations in the range of 50 to 200 ppm. Surfactant adsorption was controlled by hydrophobic attrac tions between the hydrophobic moiety of surfactant and the silicon sur face. The addition of surfactant to alkaline solutions dramatically re duced the etch rate of silicon and resulted in a smoother silicon surf ace: Oxidizing treatments followed by buffered oxide etching (BOE) wer e effective in the complete removal of adsorbed surfactant.