Future Requirements on Radiation Quantities and Testing Environment
Robert Ecoffet
Centre National d’Études Spatiales, CNES, Toulouse, France
Abstract
In the past, testing requirements were expressed in terms of ionizing dose (rad(Si)), non-ionizing dose, heavy ion LET (dE/dx) and proton energy. Except for proton energy, all those quantities are radiation – matter interaction quantities supposed to be descriptive of the effect under consideration. Are they still representative today? Two trends may limit this representativity and advocate for the definition of alternative radiation quantities.
First trend is the miniaturization of electronic technologies and their diving into the submicronic – nanometric world. “Dose” is basically a macroscopic value, how much is it representative at the micrometer or nanometer scale ? LET is a one-dimension value, how much is it representative when the target size is smaller than the ion track radius? Another consequence of the diving into the “small world” is that a larger number of particle types may be susceptible to produce effects because typical charges on the circuit are smaller and easier to disturb (today electrons can induce SEEs, tomorrow maybe photons, the day after tomorrow…?). Much more physical interactions will have to be taken into account.
Second trend is the multiplication of the number of atomic elements in electronic technologies. In the past, only a handful of elements was to take into consideration (silicon, oxygen, aluminium, phosphorus, boron…), today, almost the entire Mendeleiev table is used. One given example is the use of tungsten and copper: recoil products from proton nuclear reactions with those elements will have much larger energy deposition properties than products from silicon – proton reactions. Other examples are various types of III-V semiconductors. Laser diodes could have optical elements made of KTiOPO4 with surface treatment MgF2, etc. Stacked technologies could integrate very different active and passive materials.
It is thus essential to continue and promote research activities on the definition of more representative quantities for the description of effects (and thus definition of test conditions), and to continue and promote research activities on the characterization of the multiple interaction types susceptible to be responsible of radiation effects.