A Rad-hard On-chip CMOS Charge Detector with High Dynamic Range

Abstract

This article introduces a CMOS charge detector tailored for measuring ionizing radiation in a wide range of fluences. It represents an entirely ON-chip solution based on capacitive sensing. It was fabricated using a standard 0.18-μm CMOS process and employs metal–insulator–metal (MiM) capacitor arrays to attain high matching, low leakage, and minimal process variations. The sensing area was rad-hardened with a post-CMOS layer of metal deposited with a focus ion beam (FIB) that removes the use of external metallic plates. Experimental testing under the electron beam of a scanning electron microscope (SEM) demonstrated radiation hardness at energies up to 10 keV, with a very high dynamic range (DR) of up to 138 dB (externally adjustable), and with a sensitivity of 1.43 μV/e−. By harnessing the detection of relative charge variations instead of relying on absolute values, this approach proves highly suitable for particle event detection and facilitates future integrations compatible with the address event representation (AER) communication protocol.