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High quality compound coatings can be deposited by reactive magnetron sputtering. Optimal stoichiometry and properties of the produced coatings can be achieved by operating in a transition state of the reactive sputtering process. This state is, however, history-dependent and varies with the previous conditions used in the coating equipment. Moreover, the process conditions during the deposition can also drift due to long term effects. A discussed example is the drift of the discharge voltage as a consequence of the deposition of an insulating coating onto the vacuum chamber walls. This example was chosen because it hindered the validation of our computational model for reactive magnetron sputtering. The development of a new probe that compensates for the observed voltage drift not only advances our understanding of the reactive process, but also fixes the chosen transition state for thin film deposition.

https://doi.org/10.14332/svc24.proc.0067

A new three-layer, with three materials, antireflection (AR) coating design has been discovered. The designs for the classic three- and four-layer AR coatings in common use, when optimized with respect to the photopic response of the eye, can reduce the luminous (Y) value of reflectance to between 0.05 and 0.08 or 0.05% to 0.08%, as compared to 4.3% for uncoated crown glass. This invention can further reduce this to 0.02%. The classical three-layer AR design employs successive layers on the glass substrate of: medium, high, and low indices of refraction which are approximately one quarter, one half, and one quarter wavelength of optical thickness at a wavelength near the center of the visible spectrum. This discovery uses a notably different material for the second layer, and thereby reduces the photopic reflectance by a factor of 2 to 4 times. The performance depends a great deal on the detail index of refraction properties of this material.

https://doi.org/10.14332/svc24.proc.0031

The advent of the extensive use of Zoom and similar meeting venues has made the reflection from eyeglasses more apparent and distracting. Eyeglass lenses which have not been antireflection (AR) coated typically reflect more than 4% of light from each lens surface or more than 8% per lens. Lenses with the common 4-layer AR coating still reflect more than 0.5% of greenish or bluish light per surface. When we observe the reflection of a bright computer screen or other illumination sources in someone’s glasses while they are communicating with a video image, it is particularly distracting if they have uncoated lenses, but it still can be distracting even with the common 4-layer AR coatings. The currently available technology will allow the reduction of these reflections by an order of magnitude so that we can “look someone in the eye” when we talk with them via video conferencing. The new coatings would probably use 6-10 layers, which is not many layers as compared to more sophisticated applications where over 100 layers are now used. The common production issues limiting performance now are inadequate reproducibility of factors like pressure, rate, uniformity, temperature, etc. Tighter process control would tend to make these coatings somewhat more expensive than the present 4-layer coatings, but discerning users would probably be willing to pay a premium for their improved appearance when being viewed by video.

https://doi.org/10.14332/svc24.proc.0030

A collection of interesting vacuum-coating challenges will be presented, from uniformly coating small glass spheres to roll-to-roll coating paper, along with the solutions implemented.

https://doi.org/10.14332/svc24.proc.0026

We explored leveraging a Plasma Emission Monitor (PEM) to effectively develop a reactive titanium nitride sputtering process in a production batch-coating PVD system. It is essential for the system to have optical sensors precisely placed to view the plasma, optimally designed gas rings to inject reactive gas into the sputter plasma, and properly located MFCs to adjust reactive gas flow rates promptly. The PEM was set to track the relative intensity of the Ti/Ar emission spectra from the plasma, which decreases as the nitrogen gas ratio increases. The reactive gas flow was controlled by the PEM to maintain an emission intensity setpoint, which was found to correlate to the deposition rate and nitrogen concentration in the TiN films. This allowed us to rapidly develop a process to deposit TiN films with a resistivity < 150 μohm-cm on unheated substrates. Once the process was developed, the PEM allowed for repeatable film deposition of similar quality. Overall, the PEM is a great solution for controlling and developing reactive sputtering processes.

https://doi.org/10.14332/svc24.proc.0036

Masking of glass substrates by printable media is already used in the architectural and automotive glass industries. Within this process, the desired area on the substrate that should be kept without the coating is covered with the masking material by a screen or digital printer, the applied mask is dried or cured by UV light, a PVD coating is applied, and the coated mask is removed either by water or a chemical solvent.
For the implementation of the mentioned steps within the in-line processing of large area glass substrates, several challenges have to be solved. First, printing technology should be suitable for the process cycle time, which in some cases can be below 30 seconds. At the same time, requirements on a high print resolution, a long uptime of equipment, and low operational costs should be fulfilled. Second, the selected masking material should be compatible with magnetron sputtering processes: on one hand, exposed plasma should not damage the mask pattern, and on the hand, the outgassing rate of applied mask should be low to minimize the impact on the sputtering process. Additionally, cost of the applied mask per square meter is a crucial factor driving the choice of the print technology, especially for large area applications. Third, washing off the mask after the sputtering process should not damage the applied film, whereas coated masking material should be completely removed from the glass surface. Residuals of coating and mask material remaining in tanks with used water or solvent must be filtered out to prevent their redeposition on the next substrates entering the washing area.
Successful solution of the mentioned challenges will allow to expand the range of applications for printable masking in a sputtering process. Masking technology can potentially replace the process of edge deletion on the glass, which is nowadays required for production of individual glass units for residential and commercial buildings. It can be effectively used for production of a bird protection glass which requires specific patterns nearly invisible for humans but well recognized by birds. Another field of application is the automotive industry: sunroofs and windshields of modern cars coated with low emission films always require uncoated areas, sometimes with specific pattern, to transmit various signals e.g. rain sensors, traffic sign recognition, etc. The application of printable masks enables an extremely accurate, high yield and cost-efficient high throughput production in the field of automotive products.
In this contribution different process optimization approaches of the large area masking technology are discussed, and first essential validation results of this in-line masking and coating technology are presented.

https://doi.org/10.14332/svc24.proc.0019

Gravitational-wave detectors (GWD) are ultra-sensitive, large-scale facilities whose successful operation depends critically -among various factors- on the performance of high-reflective mirrors. These consist of doublets of high- and low-refractive-index amorphous oxide coatings deposited by ion beam sputtering (IBS). Their performance, defined in terms of high reflectivity, low optical absorption and low thermal noise, can be enhanced by optimizing the constituent materials, the deposition and post-deposition processes such as the thermal annealing. In this contribution, an implementation of real-time spectroscopic ellipsometry is proposed as a convenient tool to understand the evolution of coatings properties during the post-deposition thermal annealing. The amorphous titania-tantala coating and the annealing protocol considered here match those currently used in mirrors for GWD. In-situ analysis shows the evolution of the coating refractive index and thickness throughout the annealing, including the heating and cooling ramps. Results indicate that the current annealing protocol leaves room for further possible modifications in the coatings properties and suggest ways to optimize it. The in-situ analysis discussed here can be beneficial to screen and validate other coating materials as well as to test new annealing protocols to enhance the properties of mirror coatings for GWD applications.

https://doi.org/10.14332/svc24.proc.0029

A proprietary approach to reflection and transmission measurements using the Carl Zeiss ThinProcess UV/Vis/NIR platforms will be discussed. The following topics will be included: conventional design; Zeiss design; instrument to instrument reproducibility; supplier to supplier reproducibility; measuring on-line reflection and transmission with “lab-like” uncertainty.

https://doi.org/10.14332/svc24.proc.0038

Atomic Layer Deposition (ALD) is now a well-established process broadly used in the manufacture of leading-edge semiconductor chips. ALD is required for this application due to its high level of precision and ability for conformal deposition of pinhole-free coatings on complex surfaces. These same coating attributes are highly desirable in other applications, such as thin film encapsulation, on the large area substrates used in the display and photovoltaic industries. But to date, scaling of ALD processes to such large substrates, with sufficient throughput and at the low cost required for these applications, has been elusive. In this work, a novel Spatial Plasma Enabled ALD (S-PEALD) process is demonstrated that offers the economic scalability of ALD to these large area substrates. The use of a simple DC plasma source, enabled by the use of spatial processing, allows plasma generation over the multi-meter distances required for these substrate sizes. Meanwhile, a novel method for spatial precursor separation provides the means to utilize a simple, compact, and rapidly moving coating head for executing the ALD cycle. In combination with a mixed oxide barrier material, a process is demonstrated that provides a path to the in-line deposition of OLED-quality barrier coatings on multi-meter substrates, with a takt time of less than one minute.

https://doi.org/10.14332/svc24.proc.0022

As multi-pass, multilayer flexible coated devices grow in complexity, the need for modulatory and versatility in a vacuum R2R system is essential. The ability to incorporate a wide range for PVD source technologies and monitoring across multiple wavelengths while still maintaining precision controls and substrate handling, including particle management, substrate interleaves, thermal control in a single pass or throughout hundreds of passes is required. Delivering state of the art R2R Vacuum deposition systems for precision layers can also be enhanced by leveraging laser technology for annealing or surface modification for individual device performance.

https://doi.org/10.14332/svc24.proc.0052