Process model identification for a plasma enhanced electron beam PVD process

Controlling an inline Electron Beam Physical Vapor Deposition (eb-PVD) process requires mostly the identification of proper process models, even more if the distance between the measuring points of the process input quantity (e.g. the electron beam power) and output quantity (e.g. a layer thickness measurement) is large in comparison to the used substrate velocity. In this case, remarkable dead times between the quantities are common and therefore it is very hard to control such processes. If plasma enhanced eb-PVD process is used, it's possible to employ specific spectral emission lines of the plasma (e.g. captured by optical emissions spectroscopy [OES]) as controller auxiliary input quantity to speed up the controller's reaction on the process dynamics. In this article results of a investigation about the possibility of using the plasma spectral emission intensities as auxiliary input quantity to control the layer thickness are shown.