Performance improvement of on-chip integrable terahertz microbolometer arrays using nanoscale meander titanium thermistor

In this study, uncooled antenna-coupled microbolometer arrays were fabricated to detect terahertz waves by using nanoscale meander-shaped Ti thermistors with design widths of DW = 0.1 and 0.2 μm, respectively, on SiO₂ and SiN_x substrates. Each unit device with a thermistor with DW = 0.1 μm yielded double the electrical responsivity (787 V/W) of unit devices with thermistors with DW = 0.2 μm (386 V/W) at the maximum allowable bias current (I_b = 50 for DW = 0.1 μm and 100 μA for DW = 0.2 μm, respectively). However, the calculated noise-equivalent power (NEP) of unit devices with thermistors with DW = 0.1 μm was $1.85×10−10W/Hz$ at I_b = 50 μA and $1.58×10−10W/Hz$ at I_b = 100 μA for unit devices with thermistors with DW = 0.2 μm. Hence, the reduction in DW did not lead to an improvement in NEP. This study validates our previous investigation into the effect of width on such device parameters such as the temperature coefficient of resistance (TCR) and resistivity in the context of device miniaturization. The smaller grain size in thinner metal interconnects (thermistors) can be linked to the lower TCR and increased resistivity of the devices. Thus, the enhancement in responsivity in the design was largely due to the nanoscale meander design that, however, was detrimental to the noise response of the devices. These devices with nanoscale Ti meander thermistors deliver high responsivity in unit devices with scope for further miniaturization and have significant potential for application as on-chip integrable detector arrays.