A scientific study of the problems
of digital engineering for space flight systems,
with a view to their practical solution.
Amorphous Silicon Antifuse Programmable-Array-Logic Devices For High Relilability Space Applications
J. M. Benedetto, C. C. Hafer, A. R. Oliver, and D. B. Kerwin
UTMC Microelectronic Systems
4350 Centennial Blvd.
Colorado Springs, CO 80907
Abstract
The reliability and radiation performance of programmable array logic (PAL) devices using amorphous silicon (a-Si) antifuses is examined. Accelerated life-test data on programmed PALs show a failure rate of less than 0.1 failures in one billion device hours (0.1 FITs). It is also shown that the resistance characteristics of a-Si antifuses either improves with increasing radiation dose (unprogrammed state) or is unaffected by ionizing radiation (programmed state).
Table of Contents
List of Figures
Figure 1. Schematic cross section of the UTMC a-Si antifuse structure.
Figure 2. Portion of the PAL array showing true and complementary inputs and feedback, output logic macrocell, and array antifuse location.
Figure 3. Weibull failure distribution as a function of stress voltage.
Figure 4. Time to 0.000022% cumulative failure as a function of electric field
Conclusions
The data in this work shows that the TiW/a-Si/TiW stack fabricated by UTMC forms a highly reliable rad-hard antifuse. The unprogrammed antifuse structures were shown (via accelerated test methods) to have an MTTF of approximately 9.4x1010 years. In addition, over 2.1 million antifuse-hours were accumulated on programmed (low resistance) antifuses using a non-voltage accelerated lifetest (5.5V, 150°C stress) with no failures.
Radiation hardness data taken on the antifuses were discussed. Both the programmed and unprogrammed structures were rad-hard to at least 5Mrad(Si), with the resistance of the unprogrammed antifuse improving with total dose. The integrated PAL circuit (as measured on a 22 piece sample) was hard to 1.5Mrad(Si). The radiation hardness and high reliability of the UTMC PAL appears to make it well suited for space applications.
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