Characterization of platinum and titanium thermistors for terahertz antenna-coupled bolometer applications

• Published in: Sensors and actuators. A. Physical. Vol. 273; pp. 49 - 57
• Main Authors: Banerjee, Amit, Satoh, Hiroaki, Sharma, Yash, Hiromoto, Norihisa, Inokawa, Hiroshi
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.04.2018; Elsevier BV
• Subjects: Bolometers; Crystal structure; Diffraction; Electrical resistivity; Electromagnetics; Electron backscatter diffraction; Grain size; Infrared detectors; Metal thermistor; Microbolometer; Nanowires; Narrow-width effect; Platinum; Radiation detectors; Responsivity; Silicon dioxide; Silicon substrates; Terahertz detector; Thermistors; Titanium; Terahertz detector; Microbolometer; Metal thermistor; Responsivity; Narrow-width effect
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2018.02.014

[Display omitted] •Microbolometer is a radiation detector for infrared (IR) and terahertz (THz) waves.•Responsivity is proportional to temperature coefficient of resistance of thermistor.•Narrow-width effects on TCR and resistivity of Pt & Ti thermistor are investigated.•Device with Ti thermistor has higher responsivity than with Pt thermistor.•Device with Ti thermistor width of 0.1 μm has higher responsivity than width 0.2 μm. Microbolometer is a radiation detector for infrared (IR) and terahertz (THz) waves. The temperature coefficient of resistance (TCR) of the thermistor is a vital factor, as the responsivity is proportional and noise equivalent power (NEP) is inversely proportional to it. The narrow-width effect on TCR and resistivity on two different substrates (SiO2/Si and SiNX/SiO2/Si) for platinum (Pt) and titanium (Ti) thermistor with various design width (DW) = 0.1–5 μm are investigated. Increased resistivity and reduced TCR of the devices with the decreased line width, is observed commonly for both metal and fitted with empirical formulae, which hold well for different substrates. It is evident from electron backscatter diffraction (EBSD) results showing reduced average grain size form Ti film to Ti nanowire (DW = 0.1 μm), that the reduced TCR is not dependent on crystal orientation or phase variation of material but can be correlated with reduced grain size due to reduction of width. The optimum value considering design requirement, thermistor of DW = 0.1 μm and 0.2 μm is used further for the fabrication of microbolometers. It is found that the device with DW = 0.1 μm of Ti thermistor has ∼1.5 times higher electrical responsivity (376 V/W) at maximum allowable current than that with DW = 0.2 μm (254 V/W), which is also ∼11 times higher than device with DW = 0.1 μm of Pt thermistor.