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We propose the use of a CMOS differential circuit with inherent amplification to enhance the performance of n-channel field oxide MOSFETs as ionizing radiation dosimeters. These new dosimeters are aimed to be used in low dose applications such as X-ray diagnosis. The circuit is presented and described, and a discrete-level prototype was tested as regards sensitivity, temperature variations compensation and signal-to-noise ratio at different operation conditions. Results show that, comparing to a single MOSFET dosimeter, on chip amplification is possible along with temperature induced error attenuation. The highest sensitivity measured with respect to \gamma radiation was 0.4 V/rad. The circuit successfully measured the dose delivered in an X-ray image diagnosis environment with a sensitivity of approximately 0.5 V/rad. [ABSTRACT FROM PUBLISHER]

This paper presents a new technique to build MOS dosimeters using unmodified standard CMOS processes. The devices are n-channel MOS transistors built with the regular Field Oxide as a thick radiation-sensitive gate. The devices were fabricated in two different commercial 0.6~\mu m CMOS processes, gate oxide thicknesses of \sim 600 nm and \sim 400 nm. Responsivities up to 4.4 mV/rad with positive bias, and 1.7 mV/rad with zero gate bias were obtained in the thicker oxides. The effect of charge trapped in the oxide and interface states on the shift in the threshold voltage are analyzed. [ABSTRACT FROM PUBLISHER]

Through the injection of a Fowler-Nordheim tunnel current or the inversion of oxide fields during irradiation (Radiation-Induced Charge Neutralization), the oxide charge trapped in thick-oxide (300 nm) commercial RADFETs, often called QOT could be erased. Novel trapped-hole and interface characteristics were observed after treatments of this type at high doses. With both erasure techniques, it was possible only to neutralize a fraction of the oxide trapped charge. A non negligible amount of charge and border traps is deemed here to be “intractable”. That adjective an a symbol, QIN, are introduced for the first time in this paper. Later sections discuss the possible impact of these results. The conclusion for dosimetry is that a “reusable RADFET” dosimeter, working up to an unprecedented dose before wearing out, may be a practical possibility. [ABSTRACT FROM AUTHOR]

MIS capacitance structures, with Hafnium Oxide, Alumina and nanolaminate as dielectrics were studied under gamma photons ^60\Co, 25 MeV oxygen ions and 10 MeV protons radiation using capacitance-voltage (C-V) characterization. [ABSTRACT FROM AUTHOR]

This work proposes a new measurement technique to extend the dose range of MOS dosimeters. The technique consists on alternating stages of positive oxide charge buildup with stages of radiation induced charge neutralization, maintaining a uniform sensitivity along the whole measurement. The technique was applied with 70 nm MOS dosimeters, extending the dose measurement range from less than a kilogray to more than 675 kGy without showing wear effects. An initial saturation of interface traps creation ensures repeatability in the responses. [ABSTRACT FROM AUTHOR]

Electron trapping in HfO 2 -based MOS structures was studied through pulsed capacitance-voltage (C-V) technique. 10 nm HfO 2 layer was deposited by atomic layer deposition over a HF last treated Si substrate. The C-V curves were observed to shift to positive voltages driven by the positive applied voltage along the pulses, consistent with electron trapping due to tunneling transitions between the substrate and pre-existing defects within the oxide and the subsequent lattice relaxation through electron-phonon interaction. The dependences of the voltage shift for a given capacitance value (ΔV C) with stress bias and time, allowed to distinguish two mechanisms. An initial trapping process occurs for times shorter than the microsecond, probably associated with a thin non-stoichiometric SiO x interfacial layer, which is followed by a trapping process that starts after tens of μs and progressively slowed down, associated with traps within the HfO 2 layer. Numerical simulations yield for the HfO 2 traps an energy of 1.3 eV below the conduction band edge, decreasing exponentially with the distance from the Si interface with a characteristic length of 1.7 nm; and phonon and relaxation energies of 50 meV and 1 eV, respectively. These physical parameters are consistent with previous reports of electron trapping in HfO 2 layers deposited on a controlled interfacial layer, suggesting that trapping properties of defects inside the HfO 2 layer are insensitive to the treatment of the Si surface before HfO 2 deposition. On the other hand, the observed large initial trapping suggests that the non-controlled SiO x interfacial region is more defective than a controlled one. [Display omitted] • Electron trapping in HfO 2 layer deposited over HF last treated Si was studied. • A physics-based numerical model was employed to reproduce experimental results. • An initial trapping process is associated with a defective SiO x interfacial layer. • Trapping inside HfO 2 does not depend on the underlying interfacial layer. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of the threshold voltage of MOS dosimeters during irradiation under switched bias is investigated with the aim of using the sensors with a new biasing technique. The devices response to a bias change does not only depend on the instant threshold voltage and bias, and may lead to non-monotonical behavior under fixed bias following the switch. This work shows experimental evidence for this effect and presents a simple model based on oxide charge buildup and neutralization. The proposed model reproduces the experimental data assuming the existence of two types of hole traps in the oxide. Physical interpretations of the results are discussed. [Copyright &y& Elsevier]