Large-Scale Terahertz Sensor Array Module With Antenna-Coupled Microbolometers on Glass Substrate With Sigma-Delta ADC Readout ASIC

Abstract

We describe the design, fabrication, and demonstration of a terahertz sensor array module, designed to operate over 250-350 GHz. The antenna-coupled microbolometer was fabricated on a glass substrate with an integrated array of pixel switches and row multiplexing circuitry implemented with low-temperature polysilicon thin film transistors. While other microbolometer arrays have been reported for the upper terahertz bands, we focus on lower frequencies where adequate semiconductor sources are available potentially enabling important medical and security applications. The devices were fabricated in a Gen 3.5 flat panel manufacturing facility implementing what we call large-area micro-electromechanical systems (MEMS) platform (LAMP) surface micromachining process, providing a path to low-cost manufacturing. Individual pixels were defined on a 0.7-mm pitch across an array of 128 x 128 pixels in this first demonstration. Since flat panel fabrication capabilities use large, single-shot reticle masks and large glass substrates, physically larger arrays can be manufactured without mask stitching. A readout integrated circuit was demonstrated to support the terahertz (THz) sensor panel with 648 input channels, each providing an independent sigma-delta analog to digital converter (ADC) with excellent uniformity and 12 effective number of bits. An early demonstration of the sensor array is described, imaging a metallic knife hidden in a cardboard envelope.