A CMOS 300-GHz 7 by 7 detector array for THz imaging

In this work, a 300-GHz 7×7 imaging detector array has been developed with a 65-nm CMOS technology. Each pixel is made of an identical 300-GHz common-gate differential direct detector integrated with a patch antenna. The detector exhibits a 1,200 V/W responsivity and a 20 pW/Hz⁰⁵ NEP by simulation. The fabricated chip area is 4×4 mm² including wire-bonding pads. Employing the fabricated 7×7 detector array as a detector, real-time reflection imaging at 300 GHz was successfully carried out.

I. Introduction

THz-wave, or the electromagnetic wave with a frequency of around 300 GHz - 30 THz, is attracting growing attention due to its unique properties that can be utilized in various applications. It is transparent to most dielectric materials, while it is highly reflective to metals and water. Also, it is nonionizing and thus safe to biomedical tissues when radiated unlike X-rays [1]. These interesting characteristics make THz-wave a favored candidate particularly for imaging, which can be applied to security, safety, and biological and medical purposes [2]–[4]. Until recently, most conventional THz systems have been implemented with pulse-based optical components, which includes THz imaging systems. However, such optical systems suffer from their bulky size and costly setup as well as high power dissipation. As an effort to replace the optics-based THz imaging systems with relatively compact and low-cost integrated circuit architectures working on CW signals, this paper presents a CMOS array detector for 300-GHz imaging application and reflection imaging experiments based on this developed array.