Niobium Titanium Nitride Thin Film Coating

The Niobium Titanium Nitride (NbTiN) Thin Film Coating can optically couple light to a bolometric detector, which is suspended on an ultra-thin dielectric membrane. The coating can also filter out low frequency spectral components, which would increase the photon-limited noise of the detector. NbTiN thin film coatings are fabricated on dielectric substrates using a specialized reactive sputtering co-deposition process. Two different sputtering sources are used, in which one source contains a niobium sputtering target and the other contains a titanium sputtering target. The niobium and titanium are deposited in a nitrogen-rich environment. NbTiN coating can be used by depositing it on one side of an ultra-thin silicon membrane and have a well-defined optical impedance requirement for a specific application. NbTiN coating can be deposited on non-silicon membranes as well. The NbTiN coating have low intrinsic stress, which makes it mechanically compatible with integration on ultra-thin dielectric membranes. The coating possesses the optical impedance required for a high optical efficiency absorption. Furthermore, the coating has a very low superconducting transition temperature, which enables it to filter out radiation at certain frequencies. The NbTiN coating is especially useful for ultrasensitive cryogenic bolometric detector applications. The NbTiN coating can be fabricated in a reproducible manner, while simultaneously not complicating the fabrication process of detector architectures.