Electron Beam Physical Vapor Deposition - Disadvantages of EBPVD

Disadvantages of EBPVD

EBPVD is a line-of-sight deposition process when performed at a low enough pressure (roughly <10−4 Torr ). The translational and rotational motion of the shaft helps for coating the outer surface of complex geometries, but this process cannot be used to coat the inner surface of complex geometries. Another potential problem is that filament degradation in the electron gun results in a non-uniform evaporation rate.

However, when vapor deposition is performed at pressures of roughly 10−4 Torr (1.3 x 10−4 hPa) or higher, significant scattering of the vapor cloud takes place such that surfaces not in sight of the source can be coated. Strictly speaking, the slow transition from line-of-sight to scattered deposition is determined not only by pressure (or mean free path) but also by source-to-substrate distance.

Certain materials are not well-suited to evaporation by EBPVD. The following reference materials suggest appropriate evaporation techniques for many materials:
Vacuum Engineering & Materials Co., Inc.
Kurt J. Lesker Company

Also see Oxford's Evaporation Guide for the Elements.