Influence of nitrogen concentration on the temperature sensing and resistor properties of TaN thin films at cryogenic temperatures

Abstract

Tantalum Nitride (TaN) thin films are popular for high-precision thin film resistors in several applications due to their nearly zero temperature coefficient of resistance (TCR) from room to high temperature. This study investigates the effect of nitrogen concentration on the temperature sensing and thin-film resistor capabilities of TaN thin films in the cryogenic temperature region (10 K to 320 K). The findings show that nitrogen concentration considerably impacts the stability and TCR of TaN thin films, making them suitable for various applications. Thin films fabricated with 4 and 6 sccm N₂ exhibited low TCR values of −360 ppm/K and −670 ppm/K, respectively, keeping stability over a broad temperature range and making them suitable for resistor applications ranging from cryogenic to high temperatures. The film fabricated with a Nitrogen concentration of 10 sccm exhibited a high TCR of −8498 ppm/K at 10 K, demonstrating its strong ability for temperature sensing applications. Additionally, the film fabricated with 15 sccm N₂ showed remarkable performance as a highly sensitive temperature sensor in the 10 K–150 K range. Most notably, it exhibited an extraordinarily low TCR of −1.24 ppm/K at 260 K and −0.034 ppm/K at 320 K. This is one of the lowest TCR values ever reported, indicating remarkable stability at higher temperatures and is, hence, a good option for applications requiring ultra-stable resistors. Additionally, the bandgap energy and surface roughness of TaN thin films increased from 3.756  eV to 3.847  eV and from 0.297 nm to 0.755 nm, respectively, as the nitrogen concentration increased.