Measurement of the permeability of thin films

A system has been developed to directly measure the flow of inert gases thr ough an arbitrary thin film. The system employs a porous aluminum silicate ceramic as the substrate for film deposition, a flow control apparatus to h old the substrate under vacuum and allow a helium gas pressure differential to be established across the substrate, and a helium leak detector to meas ure the flow of helium through the substrate/film combination. This allows calculation of the permeability of the film. The permeability of plasma enh anced chemical vapor deposited diamondlike carbon films and sputter deposit ed silicon nitride, and nickel films were measured. A thermally grown silic on dioxide film was also tested. (C) 1999 American Institute of Physics. [S 0034-6748(99)04704-8].