McClellan Park, California—To operate successfully across the globe, U.S. military forces depend on the 24/7/365 availability of space-based systems like telecommunications and observational satellites. This means that these systems must operate reliably, often for decades, in a harsh environment where they face temperature extremes and ionizing radiation in the form of energetic atomic particles traveling, in some cases, at the speed of light. The most vulnerable components of a space-deployed asset are the microelectronics subsystems upon which the entire system and mission architecture is built. Over time, these microelectronics will succumb to the environment, resulting in overall system degradation and, in due course, failure.
The scientists, engineers, and program managers charged with deploying a space-based system know that the demise of its microelectronics subsystems is inevitable, and the uncertainty in predicting when the system will fail weighs heavy on their minds. They perform Earth-bound standardized tests to ensure that the microelectronics will perform as expected throughout the system’s lifetime. However, these tests do not consider the potential synergistic impact of real-world operational conditions—standardized tests for ionizing radiation, for example, do not occur in the temperature extremes encountered in space. Without this fidelity, the potential harmful effects resulting from the simultaneous exposure to ionizing radiation and elevated temperature go unexplored and unquantified.
To address this concern, engineers Dr. Kevin Geoghegan, Tom Shepherd, and Dr. Jeffrey Siddiqui at the Defense Microelectronics Activity (DMEA) in McClellan Park, California, have invented a system that investigates the combined-effects susceptibility of p-channel metal-oxide semiconductor (PMOS) devices. Ubiquitous in microelectronics systems employed by the Department of Defense (DoD), PMOS devices are fundamental constituents of the complementary metal-oxide semiconductor (CMOS) devices at the heart of the semiconductor revolution. Though relatively tolerant to ionizing radiation, PMOS devices make excellent test subjects because of their known susceptibility to another reliability concern: negative bias temperature instability (NBTI), in which device degradation occurs while undergoing electrical stress at elevated temperatures.
PMOS NBTI has been a major reliability concern within the semiconductor industry, and how NBTI manifests in a radiation environment is not fully understood. This invention and associated research are providing a glimpse into that interaction.
In order to impose the combined effects of NBTI and radiation on PMOS devices, the devices undergo accelerated reliability testing at high temperature and electrical stress while being simultaneously irradiated for up to 30 hours. During this time, periodic in situ electrical measurements are taken to observe device degradation. From the collected data, device operating lifetimes can be predicted for a given set of operating conditions.
The DMEA Science and Engineering Gamma Irradiation Test (SEGIT) facility was essential to the success of this invention. The SEGIT performs total-ionizing-dose testing for Government, university, and commercial partners. It includes two large-format irradiators, one designed for high-dose-rate testing and the other optimized for enhanced low-dose-rate sensitivity research.
Through this combined-effects testing, the inventors were able to demonstrate that ionizing radiation has a complex effect on device reliability associated with NBTI and that, in the space environment context, ionizing radiation worsened device performance under operationally relevant conditions.1 For their work, Dr. Kevin Geoghegan, Tom Shepherd, and Dr. Jeffrey Siddiqui were issued a patent by the U.S. Patent Office for the “System and Method for Simultaneous Testing of Radiation, Environmental, and Electrical Reliability of Multiple Semiconductor Electrical Devices.”
A major benefit of the invention is that it allows for devices to be simultaneously stressed and tested, whereas the current standard employs a time-consuming stress-then-test methodology that poses a risk to devices because of the additional handling required. Another benefit is that the patent ensures U.S. Government programs and other U.S. Government test labs can use the invention.
DMEA is a DoD field organization located at the former McClellan Air Force Base near Sacramento, California. A component of the Office of the Under Secretary of Defense for Research and Engineering, DMEA is chartered to leverage advanced technologies to extend the lifetimes of weapon systems by improving reliability and maintainability while addressing obsolescence concerns and diminishing manufacturing sources. Utilizing Government-owned and -operated laboratory facilities, DMEA’s microelectronics specialists provide solutions and expertise to developing, existing, and legacy programs across DoD.
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