Ultrathin Titanium Nitride Research Articles

Optical response of ultra-thin titanium nitride films on brass and gold plated brass surfaces

Nanocrystalline TiN thin films have been deposited by DC reactive magnetron sputtering on brass and gold coated brass substrates. Atomic force microscope images of the 20nm thickness films indicate that grain sizes are in the range of 30–70nm. Specular reflectance in the visible and near infrared region is between 5 and 30%. Reflectance minima, attributed to surface plasmon resonances, are observed in the region between 1.7 and 2.5eV depending on percentage of nitrogen in the sputtering gas mixture. The plasmon resonances can be tuned by varying the N2 percentage in the sputtering atmosphere. Specular reflectance and dielectric functions of films aged in air for one year show that the changes in values are very negligible. The ultra-thin TiN films can, thus, be used as capping layers to protect brass and gold surfaces from ambient environment corrosion.

Photoelectrochemical hydrogen production on silicon microwire arrays overlaid with ultrathin titanium nitride

p-Si wire arrays overlaid with an ultrathin TiN are demonstrated to be an efficient and robust photocathode for hydrogen production.

On the difference between optically and electrically determined resistivity of ultra-thin titanium nitride films

This work reports on the determination and comparison of the resistivity of ultra-thin atomic layer deposited titanium nitride films in the thickness range 0.65–20nm using spectroscopic ellipsometry and electrical test structures. We found that for films thicker than 4nm, the resistivity values obtained by the two techniques are in good agreement. However, below 4nm, the comparison shows an increasing difference with decreasing film thickness. A difference with a factor of 3 was found at 1.8nm and increased up to hundreds at 0.65nm. We attribute this significant difference to the electron scattering effects at grain boundaries and interfaces which can not be fully taken into account by spectroscopic ellipsometry measurements.

Pseudogap in a thin film of a conventional superconductor

A superconducting state is characterized by the gap in the electronic density of states, which vanishes at the superconducting transition temperature T(c). It was discovered that in high-temperature superconductors, a noticeable depression in the density of states, the pseudogap, still remains even at temperatures above T(c). Here, we show that a pseudogap exists in a conventional superconductor, ultrathin titanium nitride films, over a wide range of temperatures above T(c). Our study reveals that this pseudogap state is induced by superconducting fluctuations and favoured by two-dimensionality and by the proximity to the transition to the insulating state. A general character of the observed phenomenon provides a powerful tool to discriminate between fluctuations as the origin of the pseudogap state and other contributions in the layered high-temperature superconductor compounds.

Formation of Ti and TiN ultra-thin films on Si by ion beam sputter deposition

Ultra-thin titanium and titanium nitride films on silicon substrate were obtained by ion beam sputtering of titanium target in vacuum and nitrogen atmosphere, using argon ions with energy of 5 keV and 15 μA target current. Elemental composition and chemical state of obtained films were investigated by X-ray photoelectron spectroscopy with using Mg-Kα X-ray radiation (photon energy 1253.6 eV). It was shown that it is possible to form both ultra-thin titanium films (sputtering in vacuum) and ultra-thin titanium nitride films (sputtering in nitrogen atmosphere) in the same temperature conditions. Photoelectron spectra of samples surface, obtained in different steps of films synthesis, detailed spectra of photoelectron emission from Si 2p, Ti 2p, N 1s core levels and also X-ray photoelectron spectra of Auger electrons emission are presented.

Deposition Method-Induced Stress Effect on Ultrathin Titanium Nitride Etch Characteristics

A systematic study to investigate the fundamental cause for wet etch variation of ultrathin titanium nitride (TiN) film as a function of the deposition technique such as physical vapor deposition, chemical vapor deposition, and atomic layer deposition is presented. For this study, 10 nm TiN films were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, X-ray reflectometry, and absolute ellipsometry. It is shown that the deposition method plays an important role on the final TiN crystallography and properties. However, it is demonstrated that the dominating factor defining etch rate is the resulting film strain.

How low-energy ions can enhance depositions on low-K dielectrics

Ultrathin titanium nitride layers grown on three different dielectrics were studied to examine how low-energy ions change the chemical composition at and near their interface. Comparisons were made by growing titanium nitride under similar conditions both with (ion-assisted) and without (reactive) nitrogen ions. Although the chemical reactions between the titanium nitride and the three dielectrics under both growth conditions depend on the type of dielectric used, a few general observations were seen. In comparison with the reactively grown samples, all of the ion-assisted growths show a significant increase in the amount of nitride in the titanium nitride layer at and near the titanium nitride/dielectric interface. Moreover, the amount of chemical binding between the titanium nitride and dielectric is increased when low-energy ions are used. Finally, by using angle resolved x-ray photoemission it was determined that the enhancement in the deposition process from low-energy ions occurs without inducing significant intermixing between the titanium nitride layer and the dielectric.

Surface Morphology Improvement of Metalorganic Chemical Vapor Deposition Al Films by Layered Deposition of Al and Ultrathin TiN

The surface morphology of aluminum (Al) films grown by metalorganic chemical vapor deposition (MOCVD) has been improved by inserting a 1.0-nm-thick titanium nitride (TiN) layer between 90-nm-thick Al layers. For multilayered Al/TiN film depositions, dimethylaluminum-hydride (DMAH) and tetrakis(dimethylamido)titanium (TDMAT) are used as metalorganic precursors. For uniform and conformal TiN layers 1.0-nm-thick atomic layer deposition (ALD) was carried out in the same reaction chamber as the Al MOCVD. The surface morphology of the films was evaluated by measuring the optical reflectance. In the early stage of Al MOCVD, the reflectance versus film thickness curve shows a rapid decrease because of the scattering of incident light from the Al nuclei, and then it increases sharply to a maximum reflectance until the completion of island coalescence. However, it monotonically decays again with Al thickness due to the nonuniform grain growth. By inserting a 1.0 nm TiN layer on the Al layer at the maximum reflectance, the reflectance is restored again to the peak reflectance in the manner of a sinusoid waveform. Moreover, the multilayered Al/TiN films have a strong (111) preferred crystal orientation, and small and uniformly sized Al grains, which are expected to result in higher electromigration resistance. Therefore, the combined deposition technique with Al MOCVD and TiN ALD is considered a promising candidate to make Al MOCVD suitable for future microelectronic applications.

ダイナミックミキシング法による透光性窒化チタン超薄膜の形成

ダイナミックミキシング法による透光性窒化チタン超薄膜の形成

Interface analysis of plasma-deposited titanium nitride on stainless steels

Ultra-thin titanium nitride (TiN) films of about 30 Å, thickness were deposited by means of an electron cyclotron resonance (ECR) plasma using a plasma-sputtering process in nitrogen at 25 and 600°C substrate temperatures. Using X-ray photoelectron spectroscopy (XPS) we have investigated the chemical composition of the formed TiN/steel interface. The effects of substrate temperature during and after deposition and the influence of the plasma, on the interface are reported. At the interface the plasma is found to result in nitride formation of the substrate surface in the initial stage of the deposition process. High temperatures above 350°C during or after deposition result in metal segregations from the bulk of the substrate to the interface and even into the coating. Our observations suggest that, by controlling the substrate temperature and deposition parameters, one can effectively control structural and chemical characteristics of the interface and the coating, and consequently increase the functional lifetimes of the composite system for a given application.