Characterization and control of unconfined lateral diffusion under stencil masks

A quantitative study of the spreading behavior of electron-beam-evaporated Al, Au, Cr, Ge, Pt, and Ti on oxidized Si substrates has been performed using translated stencil masks. At least two mechanisms are needed to account for the lateral spreading of the deposited materials: The deposition edge moves by a Fickian diffusion with a diffusion coefficient of 6.7nm2/s6.7nm2∕s at 45°C45°C which is approximately independent of the deposited material. Once under the stencil mask, the deposited material spreads 0.1–2μm0.1–2μm (at 45°C45°C for under 2h2h), in a thin layer as a result of surface diffusion. The evaporation in N2N2 or O2O2 at 50μTorr50μTorr significantly suppresses the spreading with Ti showing the greatest reduction of (7–8)×