Introduction
Radiation Hardening of electronic devices is an extremely important field in the world of electronics. In general, semiconductor devices are housed in a ceramic "hardened" shell. This is primarily to prevent light from being absorbed at the junctions and changing the electric properties of the device. This idea must be taken a step further if semiconductor devices are to be submitted to conditions harsher than the atmospheric conditions on the surface of the earth.
Space is one of the harshest natural environments that devices are exposed to.
In space, two types of radiation cause
problems for semiconductor devices. They are electromagnetic
radiation and ionizing radiation. Electromagnetic radiation is
comprised of photons of gamma rays, X-rays, ultraviolet or UV
radiation, visible light, infrared, microwaves, and radio waves.
The source of electromagnetic radiation is primarily the Sun.
The relevant types of ionizing radiation are Galactic Cosmic Rays (GCR), and Van Allen Belts. GCR are made up of high-energy protons, helium nuclei, and heavy nuclei. GCR originate in distant stars and are the most penetrating radiation because of the high energy they possess. The total flux for GCR is fairly small, and may or may not cause a problem for electronic devices. The Van Allen Belts are regions around the Earth that comprise high-energy protons and electrons.
Each type of radiation described has an individual effect on electronic devices and it is necessary to know what the device will be exposed to before knowing what to protect it against. Some effects of radiation that will be discussed are as follows: Neutron Effects, Total Ionizing Dose Effects, Transient Dose Effects, and Single Event Effects. Possible solutions to the effects will also be discussed.
Figure 1. Electronics in Space
References: See Bibliography
references 8 and 9.
Picture from http://www.sigtech.com/microaz/space/space.htm