Cryogenic Total-Ionizing-Dose Response of 4th-Generation SiGe HBTs Using 1-MeV Electrons for Europa-Surface Applications

To support the use of SiGe BiCMOS for future mission targets such as Europa, which are subject to high radiation doses and cryogenic temperatures, SiGe heterojunction bipolar transistors (HBTs) were exposed to 1-MeV electrons to 5 Mrad(Si) at 300, 200, and 115 K. The presented results are the first in situ characterization of electron irradiation at cryogenic temperatures in SiGe HBTs. Lower temperature was found to improve total ionizing dose (TID) tolerance. Physical mechanisms behind this improved tolerance with cooling are examined, such as trap formation due to particle bombardment and the trapping/de-trapping of carriers at oxide/semiconductor interfaces. The results of the present work demonstrate that SiGe HBTs enjoy improved TID tolerance in addition to higher performance at cryogenic temperatures, supporting the use of SiGe BiCMOS as enabling technology platforms for space missions to harsh environments like Europa.

I. Introduction

The National Aeronautics and Space Administration (NASA) Ocean Worlds program will explore moons and planets in the solar system with liquid-water oceans in the search for signatures of extraterrestrial life [1]. Europa is of particular interest due to the warm ocean under its icy surface, and the proposed Europa Lander mission will potentially perform scientific measurements directly from the surface [2].