Monochromatic monitoring by intermittent measuring technique is established as a standard optical thickness control for thin films in box coaters since 2005. A newly developed set-up of the optical path was designed for the Syruspro 1100 DUV box-coater series. A deuterium lamp in combination with an achromatic lens system extends the monitoring capabilities to the UV range for wavelengths from 200nm up to 380nm. We present the hardware set-up and coating results for various DUV coatings.
A new, highly efficient impedance matching network is introduced , increasing the LION300 RF-source efficiency by approximately 20% and enabling considerably higher SiO2 rates for the production of shift-free and low scattering interference filters. Results of single layer coatings and a UV-IR cut filter are presented.
A newly developed wideband optical monitoring system is based on a fast triggered spectrometer with a high dynamic array detector with low signal noise. It is useful for fast in-situ transmittance measurements on the rotating substrate holder during the deposition. The spectra can be stored and used for reverse engineering analysis. Layer thickness control with monochromatic monitoring strategies can be applied by using a selected single wavelength from the array detector. The high dynamic detector supports the classical turning point monitoring as well as trigger-point cut-offs with online corrected end points. The basic system design and functionalities are described. The results of multilayer systems demonstrate the performance of the new developed monitoring system.
For the production of high performance multilayer systems with tight specifications and large numbers of layers optical
monitoring is essential. Substantial progress was achieved by the introduction of direct monitoring on the rotating
substrate holder. Pre production analysis by computer simulation of coating processes helps to optimise monitoring
strategies and reduces the effort for expensive and time consuming test runs significantly. However not in any case we
can find error compensating monitoring strategies. Also we have to deal with error accumulation effects especially with
multi layer systems with large number of layers. Changing the monitor glass after the layer stack is deposited partly is
a useful method to discontinue accumulation or to simplify the monitoring strategy.
A testglass changer which helps to suppress error accumulation was developed and automized. The testglasses are
located on the rotating substrate holder which may be a calotte or a plane substrate holder. It combines the advantages
of direct monitoring with the flexibility to change testglasses in a fully automatic process. The basic principle will be
described. Results of multilayer systems demonstrate the benefits of the newly developed testglass changer.
For the production of high performance multilayer systems optical monitoring is essential. Substantial progress was
achieved by the introduction of direct monitoring on the rotating substrate holder. It is a complex task to develop a
stable monitoring strategy for multilayers with a large number of layers and irregular thicknesses. The verification
and improvement requires the feedback of more or less numerous real coating runs. This expensive and time
consuming trial and error method can be reduced significantly by computer simulation of coating runs.
A new software tool which simulates the coating process with monochromatic optical monitoring is introduced.
Process instabilities are described by systematic and random errors of the deposition rate, refractive indices, etc. For
the simulation of the monitoring curve real monochromatic bandwidth, signal noise, measurement frequency, etc. are
taken into account. A UV-IR cut filter and a single notch filter design were simulated with virtual deposition runs. In
both cases the simulation results were confirmed by real coating processes.
The deposition of oxide coatings with excellent optical and mechanical properties requires powerful plasma or ion
sources. We investigated the layer performance of oxide coatings using a large aperture radio frequency powered plasma
source for plasma ion assisted application and related the achieved coating performance to beam parameter of the source.
The coatings exhibit low compressive stress values, high refractive indices and low absorption values. Using the new
type of source in combination with direct optical monitoring on the dome for the production of challenging interference
filters shows a huge potential in terms of stability, running costs and easy maintenance. Examples of application in the
visible spectral region will be given.
For Notch Filters, Rugate designs with a small index contrast and apodisation are well known in the literature. The
required deposition of gradient index layers or so called flip flop structures is very complicated and difficult to
manufacture. Higher order H/L stacks of coating materials with high index contrast result in very thick layer stacks. In
our approach we replace the second refractive index by equivalent layers consisting of H/L materials with high index
contrast. This leads to a combination of thick (>100nm) and very thin layers. Stable coating processes with dense layers
are strict requirements. Another challenge is the accurate thickness control of very thin layers in the nanometer range. Single notch filters were produced with PIAD and broad-band optical monitoring. The most challenging filters were demonstrated with magnetron sputtering and monochromatic optical monitoring. Some outstanding results of single and multiple notch filter coatings will be presented.
The success of fabrication of optical coatings depends on a proper choice of a theoretical coating design and on the
choice of monitoring strategy that provides low thickness errors for the chosen design. Software tools described in this
presentation help an optical coating engineer to investigate a potential manufacturability of a given theoretical design
when various monochromatic monitoring strategies are applied. This may help to reduce or even eliminate test
deposition runs required for a successful coating fabrication.
The production capabilities for optical multilayer coatings were improved significantly in the last decade. So called "shift free" coatings have become a standard in the coating production. Direct optical monitoring plays a key role to improve the layer thickness accuracy and takes advantage of error compensation effects. For the production of DWDM filters direct monitoring was introduced in the last decade. Continuous measurement is applied on relatively small substrate areas. (Ø < 200 mm). The paper reports substantial progress which has been achieved for coating systems with large area substrate holders (up to Ø 1050 mm). The stationary light spot of a single wavelength optical monitor is far out of centre of the rotating substrate holder. Intermittent monitoring on a substrate or a witness is applied. This technique enables rapid prototyping with tight specifications and high yields in large area batch coaters. Application results of challenging optical multilayer systems are demonstrating clearly the potential of this powerful monitoring technique. The monitoring capability was investigated for a lot of different layer systems such as dielectric mirrors, anti-reflection coatings, sophisticated edge filters, polarizer coatings, beam splitters and multiple cavity band-pass filters. Strong coincidence of theory with experiment was achieved with PIAD and magnetron sputtering. Reproducibility experiments have clearly shown the benefits of this monitoring technique.
The requirements to produce high performance coatings increase dramatically when moving from 248 nm to 193 nm. The quality of DUV thin film components is mainly determined by the optical properties of the applied layer materials. The reduction of losses due to scattering and absorption of dielectric materials is essential for excellent properties of the coating results. The most common oxide and fluoride materials SiO2, Al2O3, MgF2 and LaF3 have been investigated and optimized. Plasma ion assisted deposition was applied for the deposition of the oxide materials, using improved coating equipment such as the modified APSpro (advanced plasma source). The paper reports the results of DUV coatings using plasma ion assisted deposition for the oxide materials. Single layers of silica and alumina and multilayer systems with both materials were investigated. In addition, MgF2 and LaF3, conventionally coated at very high temperatures, have been performed to demonstrate the improved capabilities of the optimized SYRUSpro DUV for DUV applications with all the new features.
The success of volume production of 200GHz and 100GHz spacing WDM band pass filters relies on several critical issues: (a) a robust, high tolerance design; (b) optimized machine configurations; (c) a stable and repeatable process; and (d) an accurate and reliable optical monitoring system. At Corning NetOptix, significant effort has been made to optimize the chamber and process parameters in order to control the optical performance, the reproducibility and the useful area. This results in increased production yields and excellent filter performance. The results of 200GHz and 100GHz spacing WDM filters manufactured at Corning NetOptix are presented.
Plasma-IAD with the APS has been applied for a large number of different layer systems in production an ind R and D. The ability for the production of shift free multilayer coatings for the visible and NIR spectral range is utilized in manufacture for many applications such as steep edge filters for color separation, rugate filters for laser protection and narrow-bandpass filters for wavelength division multiplexing. An overview was given. Shift free narrowband filters for the UV-B region were published in 1996. The paper reports the result of UV coatings using plasma ion assisted deposition. Tantala/silica and hafnia/silica combinations have been used for multilayer coatings in the UV-A and UV-B spectral range. Single layers of silica and alumina and multilayer systems with both materials were investigated in the UV-B and UV-C region. The coatings were characterized by obtained transmittance and reflectance curves as well as absorption and scattering measurements. The temperature stability results are compared with coatings in the visible and NIR spectral range published.
Tetrahedral carbon thin films in amorphous modifications (ta-C) are ofinterest for applications due to their excellent hardness, chemical inertness, low friction, and low wear rates. They are obtained by mass-selected and monoenergetic carbon ion beam deposition and by laser ablation ofgraphite '' . The need ofan ion beam with a narrow distributed kinetic energy per C-atom is currently a fundamental obstacle for the use of such thin films in large area and high volume applications. More recently, the deposition of ions abstracted from a radio frequency excited acetylene plasma has yield a hydrogenated form oftetrahedral carbon with properties comparable to ta-C '.An important technological progress can be expected if an ion source can be made available that delivers carbon ions with a narrow-distributed kinetic energy per Catom, that can easily be scaled up, and that can be integrated into existing deposition systems. Due to their high vapour pressure, fullerenes can easily be sublimed and introduced into ion beam and plasma systems and thus have a potential for the deposition oftetrahedral carbon films by relatively simple technological means. The first approach to the use of fullerenes for the deposition oftetrahedral carbon was a cluster ion beam experiment ,in which fullerene ions were accelerated and disintegrated at their impact on a substrate. In another way, fullerenes can be used to generate a plasma ofhigh C2-content due to the effective dissociation ofstrongly heated fullerenes by C2-emission 6 The first use of such a plasma was a chemical vapour deposition experiment, in which fullerenes were dissociated in an argon microwave plasma and nanocrystalline diamond was grown6. The films obtained hereby show superior surface smoothness, low friction and low wear rates .Forthe deposition of amorphous carbon, a Kaufmann-source supplied with fu8 and a radio-frequency (RF) plasma source supplied with fullerenes and argon 10have been applied. Here we report on the ion beam deposition of amorphous carbon by using a fullerene argon plasma without the admixture ofhydrogen. The films are characterized regarding their Raman-emission, their plasmon loss structure and valence band spectra acquired by high-resolution X-Ray photoelectron spectroscopy (XPS), their optical absorption in the visible wavelength regime, and their wetting angles.
Plasma-IAD with the APS (advanced plasma source) has been introduced into the market in 1992. Up to now this technique is used worldwide in almost 100 coating systems. A large number of different layer systems has been investigated in R&D and applied in production. For ophthalmic applications plasma-IAD 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-IAD 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, narrow-bandpass 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-IAD with the APS. Actual evaluations of the optical constants of Ta2O5 layers deposited with APS assistance show a low extinction coefficient and a stable refractive index. New results of the performance, temperature behavior and long term stability of some interference filters confirm high packing density and low absorption of the films produced with plasma-IAD. The result of a reproducibility experiment demonstrates high process stability and high monitoring accuracy.
In many applications in the field of optical coatings low dimensions and low weight of the substrates are of increasing importance. Organic substrate materials or thin glass substrates are used in many cases. Due to the low mechanical stability, these substrates are very sensitive against bending caused by the stress of the coatings. The stress of optical coatings deposited with plasma-IAD with the APS (advanced plasma source) was investigated. Based on the bending radius of coated thin glass substrates stress values were evaluated. It was found, that film stress can be influenced significantly with the deposition parameters and the use of the coating starting materials. The results of single layer coatings of various dielectric materials and completed multilayer systems are given.
Ion assisted deposition (IAD) is a well known technique to improve the properties of thermally evaporated thin films. A wide range of materials and completed layer systems have already been investigated. Because of the low total ion current and the small beam size of the commercial available ion sources, the useful substrate area is strongly limited. With a newly developed advanced plasma source (APS) we have overcome these problems. A total ion current of up to 5 A with excellent uniformity over a large area substrate holder (approximately equals 1 m2) has been achieved. The plasma source is installed in conventional box coating system. Besides plasma-IAD the APS is also useful for plasma-CVD processes like plasma polymerization. The principle of operation of the plasma assisted processes with the APS is described. Results of dielectric materials and completed layer systems like shift free edge filters and AR-coatings are presented. In particular, in case of organic substrate materials, the advantages of the APS are outstanding. Scratch resistant layers in combination with AR- coatings and hydrophobic surface layers onto organic substrates are successfully introduced in production.
To protect the soft surface of organic CR 39 ophthalmic lenses we
built up a parallel plate reactor and developed a Plasma Enhanced
Chemical Vapor Deposition (PECVD) process for Si02 protection films.
Beside high transmission in the VIS-range we obtained refractive
indices between n=1.46 and n=l.49 depending on the process parameters
at layer- thicknesses of 2,5 jnn to 5 jmt. Deposition rates up to 30 A/s
and thickness uniformities of 10 % were achieved. The mechanical
properties of these layers were tested with different methodes and
gave better results compared with other technologies like ion-assisted
deposition or lacquering.
Ion assisted deposition (lAD) is a well known technique to iniproye the properties of thin films. A wide range of materials and conipleted layer systems have already been investigated by many laboratories.
One disadvantage of this technology is the small useful substrate
area compared to conventional thermal evaporation. This is due to the
limited ion beam size of the available ion sources. Therefore we have
developed a new plasma source which is able to irradiate a substrate
holder of 800 mm diameter with high plasma current density.
The principle of operation and some details of the plasma source
are described. The experiments were done in a conventional coating system.
The plasma source has been operated at up to 90 V discharge voltage
and up to 80 A discharge current. Up to now we have deposited some
single layers with dielectric materials. For TiO2 we have achieved
an refractive index of 2.55 at 550 nm.
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