Diffusion barriers for capping porous low dielectric constant films were important for preventing metal migration into a semiconductor circuit. Using the fact that positrons implanted into a porous dielectric form ortho-positronium (o-Ps) copiously, others had been able to measure open area fractions as low as 10–5 in porous dielectric film barrier layers from the increase in the ortho-positronium lifetime and intensity associated with positronium escape into vacuum. It was demonstrated that it was possible to obtain comparable sensitivities by measuring the gamma-ray energy spectrum of the escaping positronium.

Measuring the Continuity of Diffusion Barriers on Porous Films using γ-Ray Energy Spectra of Escaping Positronium. J.Xu, A.P.Mills, C.Case: Applied Physics Letters, 2005, 87[5], 054105 (3pp)