Development of the ultra-high-sensitive Kr adsorption technique to evaluate the pore-size distribution of thin-film materials

Abstract

To meet the increased demand of porosity evaluation of low-k materials, the ultra-high-sensitive Kr gas adsorption technique was developed. A homemade differential-type adsorption apparatus enables us to detect Kr adsorption as small as 2 μg. This corresponds to the sensitivity improvement by four orders of magnitude compared to the conventional nitrogen adsorption method. Established analytical procedures for the pore-size distribution, Brunauer–Emmett–Teller theory, Kelvin equation, and Dollimore–Heal method, are applied to Kr adsorption. The results were calibrated with one obtained from nitrogen adsorption using standard samples. Applicability of the Kr adsorption method to a low-k thin-film sample was demonstrated.