Large-Area Atomic Layer Deposition (ALD) of Titanium Nitride for RF Windows

The waveguide Radio Frequency (RF) vacuum window is a common point of failure at particle accelerators, especially during high-peak and high-average-power pulsed RF operations. At particle accelerators, such as the Spallation Neutron Source (SNS), the operating conditions can range from 300 to 1000 MHz frequencies, peak power of > 3 MW, pulsed at > 10% duty factor. Manufacturing waveguide window for high-power RF applications has proven to be challenging throughout the industry. One of the key challenges is the quality of the Titanium Nitride (TiN) coatings that is applied to the alumina ceramics in order to suppress the multipacting. RMD will address this challenge by deploying Atomic Layer Deposition (ALD) technique to deposit TiN, which will overcome the issues currently faced by the traditional Physical Vapor Deposition (PVD) methods. The key advantage of the proposed ALD technique is that the “self- limiting” chemical growth mechanism facilitates atomically conformal growth of TiN and with an excellent control on thickness, irrespective of the substrate size or the growth chamber design. Develop an ALD process for growing high-quality TiN coatings on large ceramic windows, measuring 16” diameter, with excellent control on thickness, composition, 3-dimensional coverage and its lateral uniformity over large areas. The multipacting suppression afforded by the TiN-coated ceramic windows will be evaluated in a co-axial RF-test stand operating at 201.25 MHz frequency, 3 MW peak power and 360 kW average power. The proposed development of TiN coatings by ALD will allow the scheduled performance- related upgrades for particle accelerators such as XFEL at SLAC, JLAB facility, SNS at ORNL etc. The TiN is also a much-sought coatings for gun in-barrels for improving the lifetime and performance of the guns used by the US soldiers. Electronic-grade TiN coatings are also sought by the microelectronic industry as ALD coatings, to realize the performance and miniaturization roadmap goals. This work will also lead to advances in technologies with significant commercial impact and will help maintain US technological edge over competing nations.