ABSTRACT

The extreme radiation environments described in this book include photons, electrons, neutrons, protons, and heavy ions of various energies. These forms of radiation comprise the natural space, atmospheric, nuclear reactor, and particle accelerator environments, as well as nuclear weapons environments. Electronic parts and materials used in these environments must be able to function after exposure to these forms of radiation. In order to determine that parts and materials will meet the radiation requirements for their specific application, it is necessary to test the parts to demonstrate that they will function without failure when exposed to the specified radiation levels. Often it is not possible to test the parts in the actual environment, but instead they must be exposed in a laboratory radiation environment that simulates the actual environment. In order to simulate the actual environments, one must know the effects of the radiation on the critical electrical parameters. The most widely used radiation-sensitive materials in microelectronics are silicon (Si) and silicon dioxide (SiO2). The most important effects of the radiation are ionization energy deposition (total ionizing dose, TID) and nonionization energy loss (NIEL), or displacement damage dose (DDD). The units most often used for these parameters are rad (material), 100 erg/g, and 1 MeV equivalent neutrons/cm2 fluence, ~2 × 10−6 MeV-cm2/mg, respectively. For single-event effects from heavy ions, the primary effect is energy deposition per unit path length or linear energy transfer (LET), given in pC/μm or MeV-cm2/mg, where ~1 pC/μm = ~100 MeV-cm2/mg. These simple concepts of measuring all effects in terms of TID, DDD, and LET do not always work for the simulation of actual radiation environments. However, the basic approach to performing laboratory tests to simulate the effects of the various radiation environments is based on these simple concepts. The primary radiation sources used to test microelectronic devices for the various effects are 60Co gamma rays (~1 MeV) and 10 keV x-rays for TID, nuclear reactor or accelerator/target generated neutrons for DDD and accelerator-generated heavy ions or protons for singleevent effects.