Microfabrication techniques used in Japan for VLSI and other devices

Lead films of thickness 100 Å, 250 Å. and 350 Å were vacuum deposited on AI and laser treated in air using single pulses (7 ns FWHM) from a Nd: glass laser operating in TEM₀₀ mode, at peak energy densities of 1.5-5.0 J/cm². Rutherford back-scattering of 1.8 MeV He⁺ ions was employed to determine the depth profiles of Pb in Al. Up to about 1.4 J/cm², we observe only evaporation loss of Pb and formation of Pb-rich cells on the surface. At higher energies, liquid phase diffusion of Pb is observed up to 4 J/cm², beyond which convection effects are seen. A quantitative analysis of data for 350 Å film at 3.0 J/cm² shows evidence of nonequilibrium segregation effects.