Optical properties of plasmonic titanium nitride thin films from ultraviolet to mid-infrared wavelengths deposited by pulsed-DC sputtering, thermal and plasma-enhanced atomic layer deposition

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Abstract

We present a comparative study of the optical properties of 50 nm-thick titanium nitride (TiN) films deposited on a silicon substrate by pulsed-DC sputtering, thermal, and plasma-enhanced atomic layer deposition. Silicon was chosen as the optimal material for the complementary metal–oxide–semiconductor (CMOS) integration. Using ellipsometry and Fourier-transform infrared (FTIR) spectroscopy, broadband permittivity of the films was obtained from a series of free-space reflection measurements in the wavelength range of 210 nm to μm (47619–500 cm−1). Our particular focus is on the influence of the deposition method and its process temperature on the TiN plasmonic properties. We used grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, X-ray reflectometry, atomic force microscopy, and electrical resistivity measurements to analyze the composition of thin films and to elucidate the effect of different deposition parameters on their optical properties. All measurements were carried out at room temperature and the thickness of all film samples was fixed to 50 nm to exclude the influence of these factors on the optical properties. We demonstrate that PEALD-deposited films have smoother surfaces than those deposited by the sputtering technique, while sputtered films have higher densities. In addition, by changing the temperature of both processes, it is possible to influence the stoichiometry and crystal orientation of the layers. Based on this characterization, we found out that TiN thin film deposited by pulsed-DC at 600 °C gives the best plasmonic response (high negative permittivity εand relatively low losses associated with ε2, where εand εare the real and imaginary parts of permittivity, respectively) among all samples for the entire wavelength range under study. The same film also exhibits the excellent resistivity of 29 µΩ. These results suggest that there is a direct relationship between stoichiometry, structural quality, and oxygen incorporation in TiN films and their plasmonic response.
Original languageEnglish
Article number114237
JournalOptical Materials
Volume143
Number of pages9
ISSN0925-3467
DOIs
Publication statusPublished - 2023

Keywords

  • Atomic layer deposition
  • Ellipsometry
  • Optical characterization
  • Plasmonic material
  • Sputtering
  • Thin film
  • Titanium nitride

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