Experimental investigation into impacts of neutron irradiation on pMOS dosimeter behaviors

Abstract

The p-channel metal–oxide–semiconductor (pMOS) transistor is a frequently used dosimeter for ionizing radiation, such as γ-rays, since its threshold voltage changes (ΔVth) in proportion to the ionization dose. When a pMOS is subjected to γ-ray and neutron radiation fields, the neutrons can influence the ΔVth response to γ-rays. Individual cobalt-60 γ-ray irradiation and sequential irradiation by fission neutrons and subsequent cobalt-60 γ-rays are used to explore the neutron-induced impacts. Experiments show that preceding neutron irradiation can reduce γ-ray sensitivity of ΔVth while accelerating the recovery of ΔVth during the post-γ-irradiation annealing. Additionally, the component of ΔVth induced by oxide charges (ΔVox) is separated from that induced by interface traps as determined by mid-gap tests. This proves that the neutron sensitivity of ΔVox accounts for that of ΔVth. According to nuclear collision theory, this work suggests that the electronic loss of neutrons rather than the nuclear loss dominates the neutron-induced influences on ΔVth.