Experimental Determination of the Low-Energy Spectral Component of Cobalt-60 Sources

Total-dose failure mechanisms are identif ied over a wide range of dose rate for 2K and 16K SRAMs from hardened and commercial CMOS technologies. Failure was defined "parametrically," such that an IC fails if one of its parameters, e.g., static power supply current or timing, exceeds a preset specification following irradiation. These studies demonstrate that the dominant failure mechanisms of SRAMs in space radiation environments are often quite different than those observed at considerably higher laboratory dose rates specified by DoD test guidelines, i.e., 100 to 300 rad(Si)/s. In addition, the total-dose hardness of SRAMs varied significantly between laboratory and space dose rates. Several approaches are discussed for predicting total-dose hardness of ICs in space from laboratory measurements. Results are also presented for transistors irradiated over the same range of dose rate (200 to 0.02 rad(Si)/s) and at all biases, i.e., N-on/off and P-on/off. These transistor measurements are used to characterize the physical mechanisms that govern the radiation response of the more complex SRAMs. In a surprising result, a dose-rate dependence for the buildup of radiation-induced interface states was observed.At dose rates from 200 to 0.02 rad(Si)/s, the number of interface states at a given total dose increased as the dose rate decreased.

Section: Samples and Experimental Techniquesmentioning

confidence: 99%

Total-Dose Failure Mechanisms of Integrated Circuits in Laboratory and Space Environments

Winokur

Sexton

Hash

et al. 1987

“…cm fiO-60 and f x-ray are the fractional hole n yields in the 60Co and 1O-keV x-ray cm sources, and Ri8-6O and R6-ray are the n dose enhancement in the 60Co and 10-keV xray sources. Rie-60 is usually assumed to be 1; however some 60Co sources can have an appreciable low-energy component [16].…”

Section: Z2umentioning

confidence: 99%

The Relationship between 60Co and 10-keV X-Ray Damage in MOS Devices

Benedetto

Boesch

1986

178

This paper presents a conduction current technique to separate the effects of fractional charge yield and dose enhancement in metal-oxide semiconductor (MOS) devices in a 1O-keV x-ray environment. The results of the conduction current measurements, together with the concept of charge generation as the damage-producing agent, are used to correlate the threshold-voltage shifts in gate-and field-oxide MOS field-effect transistors irradiated with 60Co and a 10-keV x-ray machine. A straightforward procedure for calculating the equal6,gamage dose equivalence between the 1O-keV x-ray and Co sources is also presented. 1.

“…At the present time Monte Carlo calculations of dose ehancement versus photon energy are only available for gold next to silicon and gold next to polyethylene. This restricts the application of the method outlined in [3] to those material combinations. The direct measurement technique does not require data from calculations and can be applied to any combination of materials which are electrically conducting.…”

Section: Performancementioning

confidence: 99%

The direct measurement of dose enhancement in gamma test facilities

Burke¹,

Lowe²,

Snowden³

et al. 1989

The design and use of a dual cavity ionization chamber for routine measurement of dose enhancement factors in CO-60 gamma test facilities is described. The enhancement factors can be derived directly from the chamber measurements without recourse to reference data that may be difficult to obtain. It is shown, in agreement with earlier work, that the maximum dose enhancement factors can be altered by a factor two as a result of Compton scatter from relatively small amounts of low or high atomic number materials next to the target. The dual chamber permits the ready detection of such effects. This relatively simple device reliably reproduced earlier results obtained by more involved equipment and procedures. Measured enhancement factors are reported for new material combinations not previously examined and compared with recent calculations.