Comparative study of titanium, platinum, and titanium nitride thin films for micro-elecrto mechanical systems (MEMS) based micro-heaters

Abstract

This paper presents a comparative study of titanium (Ti), platinum (Pt), and titanium nitride (TiN) micro-electro mechanical systems based micro-heaters. In the present study, a common geometry and thin film thicknesses were selected to achieve comparable base resistances for all three microheater materials. Titanium, platinum, and titanium nitride thin films are deposited using DC magnetron sputtering, E-beam evaporation, and reactive DC magnetron sputtering techniques, respectively, and deposited thicknesses were verified using scanning electron microscopy. Mechanical properties such as Young’s modulus and hardness were also evaluated using nano-indentation. Later, the micro-heaters were fabricated, packaged, and characterized. The thermal coefficient of resistance (TCR) was found to be 4146, 2641, and 487 ppm/°C for Ti, Pt, and TiN micro-heaters, respectively. Power–temperature (P–T) characterization showed that the power required to reach the set temperature is comparable for all the above micro-heater materials. The TiN micro-heater exhibits a linear voltage–current (V–I) characteristic compared to platinum and titanium micro-heaters. The temperatures measured using infra-red imaging were comparable to those calculated by TCR measurements. Furthermore, thermal stability studies have been performed on all micro-heaters for 110 h. TiN microheaters were found to be more stable and resilient to external environmental conditions than Ti and Pt microheaters because of their lower TCR values.