Chapter 11 - Vacuum Polymer Deposition

Abstract

Among the numerous methods used to deposit organic materials and polymers, vacuum polymer deposition (VPD), also known as the polymer multilayer (PML) process, produces ultrasmooth, nonconformal, and pinhole-free films at very high deposition rates over large areas. VPD films actually smooth the surface of the substrate. All other vacuum deposition techniques essentially bombard the substrate with species from a source that can bond immediately to the surface (low energy), bond after moving some distance on the surface, or reflect off the surface. A VPD layer does not grow atom by atom upward from the substrate; a gas of monomer vapor condenses on the substrate as a full-thickness liquid film that covers the entire substrate surface and its features. The liquid film is then cross-linked into a solid layer by ultraviolet (UV) or electron beam (e-beam) radiation. The resulting surface is glassy with virtually no defects or pinholes. The VPD layer can be combined with conventional physical or chemical vapor deposition layers (PVD, CVD, PECVD, etc.) to form low-defect, ultrasmooth thin film structures. VPD technology permits ultrafast deposition of polymer films in the same vacuum environment as conventional physical vapor deposition (sputtered or evaporated) thin films. The VPD process has two forms, evaporative and nonevaporative. Each begins by degassing the working monomer, which is a reactive organic liquid. The VPD process has several distinct advantages over conventional organic and organic/inorganic deposition processes.