Pulsed electron beam lithography in soft vacuum

Abstract

Large‐area (cm2 ) proximity patterning of selected microelectronic polymers using soft vacuum (0.05 Torr) pulsed electron beams is described using polymers with widely differing electron sensitivities (2–80 μC/cm2 at 20 keV). The short duration (∼100 ns) electron beams are produced in the pulsed mode (25–28 keV electrons, 2–3 J/pulse). These electrons impinge upon thin polymer films in the presence of an ambient gas to produce electron initiated bulk polymer chemical reactions including partial self‐development. In soft vacuum, pulsed electron beams are shown to be capable of transferring submicron (∼0.5 μm) features from an electron transmitting stencil mask onto poly(methylmethacrylate) (∼3 μm thick) films. Wide‐area exposure (field size ∼20 mm) is also demonstrated for micron feature sizes. Soft vacuum lithography appears well suited to microelectronics packaging lithography where resist thickness is substantial, linewidths are 1–10 microns, areas to be processed are large (100 cm2 ), and where registr...