Highly Plasmonic Titanium Nitride by Room-Temperature Sputtering

Abstract

Titanium nitride (TiN) has recently emerged as an attractive alternative material for plasmonics. However, the typical high-temperature deposition of plasmonic TiN using either sputtering or atomic layer deposition has greatly limited its potential applications and prevented its integration into existing CMOS device architectures. Here, we demonstrate highly plasmonic TiN thin films and nanostructures by a room-temperature, low-power, and bias-free reactive sputtering process. We investigate the optical properties of the TiN films and their dependence on the sputtering conditions and substrate materials. We find that our TiN possesses one of the largest negative values of the real part of the dielectric function as compared to all other plasmonic TiN films reported to date. Two-dimensional periodic arrays of TiN nanodisks are then fabricated, from which we validate that strong plasmonic resonances are supported. Our room-temperature deposition process can allow for fabricating complex plasmonic TiN nanostructures and be integrated into the fabrication of existing CMOS-based photonic devices to enhance their performance and functionalities.

A Platform for Complementary Metal‐Oxide‐Semiconductor Compatible Plasmonics: High Plasmonic Quality Titanium Nitride Thin Films on Si (001) with a MgO Interlayer

“…As shown in Figure 4b, the use of MgO interlayer enables our TiN films to significantly outperform the plasmonic quality of other reported films grown on different substrates and by various deposition methods at CMOS compatible temperatures. More importantly, TiN films with an MgO interlayer exhibit the best performance among films grown on Si by PE‐ALD [ 23 ] and reactive sputtering [ 34 ] at CMOS compatible temperatures, and even at higher than 600 °C, [ 24,44 ] while also achieving their peak and fairly consistent performance in the telecommunications range (Figure 4a) and the solid and open connected dots in Figure 4b. It should also be mentioned that the usage of the 10 nm MgO interlayer shifts our data points to the high‐performance edge of the growth temperature dependence trend (Figure 4b) for films grown on bulk MgO, even though our films were grown on a Si substrate.…”

“…Figure 4. a) FOM ¼ Àε 0 /ε 00 TiN thin films grown on Si (001), Si (001)/MgO, and bulk MgO (001) substrates as a function of wavelength. b) Comparisonof FOMs obtained in this work with TiN films grown on sapphire, Si, and MgO substrates under deposition temperatures ranging from room temperature to 1000 C, reported in previous studies [23,24,28,30,34,42,44,[62][63][64]. …”

“…This requires the growth of high plasmonic quality TiN on Si substrates at CMOS-compatible temperatures. However, so far, only moderate plasmonic properties could be attained for TiN films grown on Si substrates using various deposition methods such as sputtering, [24,33,34] pulsed laser deposition (PLD), [35] and atomic layer deposition (ALD) [23] primarily due to the associated large lattice mismatch (21.9%). A relatively low resistivity of 1.5 Â 10 À5 Ω cm could be achieved by PLD only at temperatures as high as 700 C, [35] and TiN films grown on Si at lower temperatures of 250 C by ALD, although used to demonstrate fully CMOS-compatible plasmonic nanoantennas, exhibited weak metallic character (i.e., insufficiently large negative ε 0 of À24) and much higher loss (larger ε 00 of 41) compared with TiN films on MgO (ε 0 þiε 00 ¼ À30 þ 26i) at telecommunication wavelength 1550 nm.…”

Optical, electrical and mechanical properties of TiN thin film obtained from a TiO2 sol-gel coating and rapid thermal nitridation

“…The transmittance spectrum of the TiN thin film presents a maximum of 35% at wavelengths around 500 nm and decreases under 5% in the near-infrared region. The reflectance spectrum indicates a minimum of 21% at 500 nm and a high reflection around 70% in near-infrared wavelengths highlighting the metallic character of TiN [29].…”

Interface study of thermally driven chemical kinetics involved in Ti/Si3N4 based metal-substrate assembly by X-ray photoelectron spectroscopy

“…Depending on the external parameters like annealing temperature, film thickness, pressure etc., the preferential growth may occur between the nitride and silicide phases [6] and the majority phase dominates strongly over the minority so that distinctive characteristic properties from the former can be explored while keeping the latter unaffected. For instance, some of the characteristic properties, such as superconductivity [12,13], plasmonic [14][15][16], biocompatibility [17] and coating [18,19] related properties that are possessed by TiN, can be explored if it is obtained as the majority phase governing the properties of the whole composite system.…”