Plasma-ion-assisted deposition: a powerful technology for the production of optical coatings

Abstract

Plasma-lAD with the APS (dvanced plasma ource) has been introduced into the market in 1992. Up to now this technique is used worldwide in almost I 00 coating systems. A large number of different layer systems has been investigated in R&D and applied in production. For ophthalmic applications plasma-lAD with the APS is used for antireflection systems as well as for wear resistant coatings onto organic substrates. New processes which combine the AR coating and the hardcoating on ophthalmic lenses have been successfully introduced into mass production. Plasma-lAD is also used for laser protection coatings onto plastic substrates. The ability for the production of shift free multilayer coatings is utilized in manufacture for many applications such as steep edge filters for color separation, rugate filters for laser protection, narrowbandpass filters in the NIR region for wavelength multiplexing in the field of fiber optic communication or for radiometers in the UV-B region. A review of the development of some important APS based coating processes and applications shows the flexibility of plasma-lAD with the APS. Actual evaluations of the optical constants of Ta205 layers deposited with APS assistance show a low extinction coefficient and a stable refractive index. New results of the performance, temperature behaviour and long term stability ofsome interference filters confirm high packing density and low absorption ofthe films produced with plasma-lAD. The result of a reproducibility experiment demonstrates high process stability and high monitoring accuracy.Ion assisted deposition for optical coatings has been used since many years. A large number of papers which show the superior properties of this technique have been published. Due to the limited ion bombardement onto large substrate areas most of the ion sources available on the market do not meet the requirements for high throughput production. Plasma-lAD with the APS has overcome this problem. Superior film properties are achieved on substrate areas of more than I m2. Therefore plasma-lAD becomes more and more important in the production ofhigh performance filters in the UV, VIS and NIR spectral range. No discernible vacuum to air shift, high temperature stability as well as low absorption is experienced without the need for additional substrate heating. Due to the low temperature loading of the substrates, deposition of organic substrate materials is successfully used in production.The principle of plasma-lAD with the Advanced plasma source (ASP) is shown in figure 1 . The plasma source, which is based on a large area LaB6 -cathode, a cylindrical anode tube and a solenoid magnet, is located in the center of the chamber bottom. The cylindrical LaB6 -cathode is indirectly heated by a graphite filament heater. A dc voltage between anode and cathode creates a glow discharge plasma with a hot electron emitter, supplied with a noble gas such as argon. Due to the magnetic field of the solenoid magnet, which surrounds the anode tube, the plasma is extracted towards th...

Surface technology for automotive engineering

“…Plasma activated electron beam evaporation is nowadays the preferred process for manufacturing of antireflective coatings on lenses for optical instruments or spectacles [197].…”

Self-organized antireflective nanostructures on PMMA by ion etching

“…Due to the magnetic field of the solenoid magnet, surrounding the anode tube, the plasma is extracted towards the direction of the substrate holder. The reactive gas is introduced through a ring shower located on top of the anode tube 15 . Two distinct maxima are characteristic for the distribution of the high energy ions: one in the range of the plasma potential (10 eV), and the other at the corresponding bias voltage (60 eV -160 eV).…”

Optimization of the spectral performance of multilayer coatings on complex optics in plasma assisted deposition processes

“…Plasma assistance is used to densify the films at lower process temperature [1,2,3]. The evaporation of dielectrics and metals shows high flexibility as chamber volume can be large, substrate shape and position can be almost arbitrary and available optical materials are numerous and very flexible regarding available refractive indices [3].…”