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This report describes results of radiation effects studies on charge-coupled devices (CCDs) and other MOS structures. Emphasis is placed on determining the basic mechanisms of the interaction of radiation with such devices with a view toward gaining understanding of benefit to developers of radiation-tolerant devices. A study of neutron damage mechanisms in CCDs was performed with emphasis placed on investigation of dark current increases.

This report describes results of several related studies of ionizing radiation effects on silicon-on-sapphire devices and on silicon dioxide films. In the SOS investigation, emphasis was placed on the study of radiation-induced back-channel leakage current and on a comparison of devices with wet and dry gate oxides. Differing behavior for wet and dry devices is accounted for in terms of a larger density of hole traps in the sapphire for dry transistors as compared to wet units. SEM studies reveal that energy must be deposited in the sapphire before significant increases in leakage current will occur. In addition, such studies indicate that energy deposition deep in the sapphire bulk is relatively unimportant in producing leakage current. A process of radiation-induced reduction of leakage current was observed in which this current can be dramatically reduced to near its pre-irradiation value by simply reducing the applied drain bias to zero and continuing the irradiation. Models for radiations effects on SOS devices are presented. Measurements of the temporal, temperature, and electric-field dependences of radiation-induced charge transport have been performed for radiation-hardened SiO2 films.

Analytical and experimental studies of charge transport and charge buildup in aluminum-implanted SiO2 were performed which indicate that both electrons and holes are trapped in the implanted region. Results of an ionizing dose rate study for CMOS devices are presented in which the effects of two low dose rates (0.2 and 70 rads(Si)/sec) are compared. Charge transport studies on pedigreed MOS capacitors were made and results compared to those for similar devices. Detailed measurements of charge transport in radiation-hardened SiO2 films were performed as a function of temperature, applied electric field, and time following pulsed excitation. Determinations of SiO2 hole mobility were also made as a function of time, temperature, and field. An investigation of charge buildup at low temperatures in radiation-hardened MOS capacitors was performed and severe flatband voltage shifts were noted. Employment of ion-implanted oxides was observed to reduce this effect. A bibliography of published work on neutron-irradiated silicon is included.

Contents: Oxide studies--Hole and electron transport in SiO2 films, Charge transport studies in SiO2: processing effects and implications for radiation hardening, Ionizing dose rate effects in MOS devices, Experiments on MOS capacitors fabricated on a p-type silicon substrate, Ion microanalyzer measurements on SiO2 films, Effects of bias polarity on current flow in SiO2 under electron beam injection, Studies of charge transport and charge buildup in pure SiO2 and Al+-implanted pure SiO2, Determination of hole mobility in SiO2 films; Semiconductor studies.

This report describes results of an investigation of radiation effects on semiconductor devices used in electro-optical sensor applications. Emphasis is placed on determining the basic mechanisms of the interaction of radiation with such devices with a view toward gaining understanding of benefit to developers of radiation-tolerant devices. A study of ionizing radiation effects on silicon MOS devices was performed at temperatures ranging from 4 to 77 degrees K. Charge buildup in the SiO2 layer was observed to be identical at 4 and 77 degrees K after a steady-state exposure to ionizing radiation, which indicates that electron trapping is not important at 4 degrees K. Results at both temperatures can be accounted for quite well in terms of hole trapping and hole transport. An investigation of the basic mechanisms of radiation effects on extrinsic silicon detector material was initiated. Carrier removal produced by neutron bombardment of such material was studied and it was found that the introduction rate of compensating defects depends strongly on the depth within the forbidden gap of the intentional dopant level. A detailed study of radiation effects on charge-coupled devices was performed, with emphasis placed on examining changes in dark current density produced by bombardment with neutrons and with ionizing radiation. The rate of increase in dark current density was found to be very similar for neutron-irradiated buried-channel CCDs obtained from two sources. Results of short-term annealing measurements on CCDs following pulsed neutron bombardment are also presented. A damage coefficient appropriate for describing the introduction of damage in silicon depletion regions was experimentally determined.

A reusable solid state device is disclosed which monitors ionizing radiation. The device is a silicon-on-sapphire n-channel MOS transistor having a back-channel leakage current which is proportional to total radiation dose. To return the monitor to its original reusable state, the drain-to-source transistor bias is reduced to zero while irradiating the device to an appropriate dose level. (Author)