Radiation Tolerant Electronics

On some occasions, an electrical engineer has to design radiation tolerant electronics for applications such as satellites, nuclear power plant. Radiations basically deposit certain amount of energy on electronic devices, which could generate electron-hole pairs, break bonds, create dislocations in crystal lattice. There are two effects, the total dose effect and the single event effect. The total dose effect is an accumulative effect , which traps charged particles or increases surface states causing changes in MOSFET thresholds. The single event effect could be single event latch-up (SEL) or single event transient (SET). The electron-hole pairs created by energetic particles trigger certain parasitic structures to turn on causing latch-up in CMOS. The single event latch-up can be mitigated with different device structures, such as epitaxial substrate or silicon on insulator. The single event transient can cause single event upset (SEU) in registers or memory cells when the disturbed electrical signals are latched into registers. The single event upset is usually mitigated with circuit design, single event upset immune register can be designed or with redundancy, in particular triple module redundancy.

Radiation tolerance level for total ionization dose (TID) is specified in Krad and for single event effect in linear energy transfer (LET). And the single event upset rate in number of errors per bit per day. In space applications, TID requirement is usually 100-300Krad (Si) , but in some extreme cases, such as Jupiter missions, TID could exceed 1Mrad.