Allan H. Johnston

Super Recovery of Total Dose Damage in MOS Devices

Super recovery of the gate threshold voltage has been observed for several types of commercial NMOS integrated circuits. These devices have characteristic recovery times that are as much as four orders of magnitude shorter than those reported for hardened oxides. Since these fast recovery times are comparable to the irradiation times used in conventional total dose facilities, their failure levels are strongly affected by the dose rate used for testing. An empirical model has been developed that predicts the general features of super recovery, and can be used to calculate the dependence of circuit failure levels on dose rate.

A proposed hardness assurance test methodology for bipolar linear circuits and devices in a space ionizing radiation environment

A hardness assurance test approach has been developed for bipolar linear circuits and devices in space. It consists of an initial test for dose rate sensitivity and a characterization test method to develop the conditions for a lot acceptance test at high dose rate. For parts with adequate design margin and/or well behaved parts a generic elevated temperature irradiation test is proposed.

Emerging radiation hardness assurance (RHA) issues: a NASA approach for space flight programs

Spacecraft performance requirements drive the utilization of commercial-off-the-shelf (COTS) components and emerging technologies in systems. The response of these technologies to radiation is often complex. This engenders a set of emerging radiation hardness assurance (RHA) issues which include displacement damage in optocouplers, high-precision and hybrid devices, enhanced low dose rate (ELDR) and proton damage enhancement (PDE) in linear circuits, linear transients, and catastrophic single event effects (SEEs) phenomena. NASA has developed an approach to designing reliable space systems which address these emerging RHA issues. This programmatic methodology includes hazard definition, hazard evaluation, requirements definition, evaluation of device usage, and application of radiation engineering techniques with the active involvement of designers. Risk assessment is an integral constituent in the approach as is an established program to assess future technology needs for programs.

Total ionizing dose effects on flash memories

This paper presents the results of measurements performed on two different flash memory types, NOR and NAND technologies. The data suggest that the degradation is influenced by the activation of integrated charge pump circuits. The NAND type device functionally failed at lower TID level than the NOR technology, even when the NOR device was used with the charge pump activated.

An updated data compendium of enhanced low dose rate sensitive (ELDRS) bipolar linear circuits

The 1996 total dose data compendium on ELDRS in bipolar linear circuits is updated. The new data include 37 data sets at high and low dose rate on 29 part types from nine manufacturers. A new table on elevated temperature irradiation has been added. References for each data set are provided.

A compendium of recent total dose data on bipolar linear microcircuits

Many conventional bipolar linear microcircuits used in space systems have shown a dose rate sensitivity to total dose degradation. Dose rate data, taken by several agencies, have been combined and presented in terms of sensitive parameter shifts at a fixed dose and dose rate enhancements factors.

A Framework for an Integrated Set of Standards for Ionizing Radiation Testing of Microelectronics

Post irradiation effects necessitate modifications to total dose testing procedures. A test methodology based on three options is proposed: (a) Test Method 1019, (b) Method 1019 with safety factors, (c) and a new test method based on extrapolation from measurements to effects expected at time of threat.

Total Dose Effects at Low Dose Rates

The effects of irradiation at very low dose rates are discussed for hardened CMOS devices from two different manufacturers. For some devices, rate effects were important even at dose rates of 0.04 rad(Si)/s, so that even lower dose rates may be required to characterize their behavior for some applications. Modeling approaches for low dose rates are discussed, and linearity of the charge generation processes is shown to be an important factor in modeling. Interface state generation for one process was highly nonlinear, which reduced the impact of annealing and super recovery on device hardness.

Low Dose Rate Effects in Shallow Trench Isolation Regions

Dose-rate effects are studied in shallow trench isolation regions. Increased damage is observed at low dose rate, with a different dose dependence compared to tests done at high dose rate. A three-dimensional modeling program was used to show that charge trapping occurs much deeper in the trench region when sufficient charge is present to reduce the field in the trench.

Dose rate and bias dependency of total dose sensitivity of low dropout voltage regulators

Total dose tests of six different low dropout voltage regulators show sensitivity to both dose rate and bias during exposure. All devices tested exhibited Enhanced Low Dose Rate Sensitivity (ELDRS) and performed worse for the unbiased irradiation condition. Behavior of critical parameters in different dose rate and bias conditions is compared and the impact on hardness assurance methodology is discussed.