9.4.2 Experimental data and prediction of component degradation

a. Experimental data used to calculate single event rates shall cover a LET range (for heavy-ion induced SEEs) or energy range (for proton and neutron-induced effects) capable to ensure that:

1. The lower LET or energy is less than the threshold for the onset of the single event effect.

NOTE 1 The lower LET or energy threshold can require extensive testing to determine. For protons it is influenced by packaging, while for neutrons it can be in the region of thermal energies if Boron-10 is present.

NOTE 2 Lower LET or energy threshold for the testing is specified in the radiation hardness assurance programme under ECSS-Q-ST-60.

2. For heavy ions, the upper LET threshold corresponds either to:

(a) the maximum LET expected for the environment,

(b) the device LET saturation cross section,

NOTE Saturation is defined according to the radiation hardness assurance programme established under ECSS-Q-ST-60.

(c) 60 MeV×cm²/mg.

3. For nucleons, the maximum energy corresponds either to:

(a) the maximum energy for the predicted environment, or

(b) the device saturation cross section is in the range.

NOTE Saturation is defined according to the radiation hardness assurance programme established under ECSS-Q-ST-60.

(c) 150 MeV for all SEE phenomena.

b. Cross section data shall be from tests where the test particle’s range in the material ensures it is able to penetrate the entire sensitive volume of the device.

NOTE The reason is that many modern devices (including power semiconductors) have significant vertical structure and very thick epitaxial layers and sufficient range of the incident test particle is required to adequately penetrate through the entire sensitive volume of the device.

c. The experimental data used for device conditions shall be either those expected for operational conditions, or such that the experiment provide worse SEE-susceptibility data, as follows:

1. For SRAMs and DRAMs, SEU-dependent electrical conditions are voltage, clock frequency and refresh rate.

2. For SEL, tests are for the maximum power and maximum temperature conditions expected for space application.

3. For SEB, tests correspond to the minimum operating temperature for the application, as this corresponds to maximum SEB susceptibility of the device.

d. For SEL, SEGR, and SEB, the potential inaccuracy of LET cross-section data obtained using obliquely incident heavy-ion beams shall be analysed and the results reported in accordance with the RHA programme established under ECSS-Q-ST-60.

NOTE 1 The reason is that the concepts of sensitive volume and effective LET are not strictly valid (see ECSS-E-HB-10-12 Section 8.6.1 to 8.6.3).

NOTE 2 SEHE cross-section can be a function of particle species and energy (i.e. not just LET) and angle of incidence (see ECSS-E-HB-10-12 Section 8.7.4).

NOTE 3 It is important that the ion track width of the particles used in the irradiations is sufficient to cover a significant fraction of the gate region.

NOTE 4 There are synergies between SEHE rates and cumulative dose (TID) as well as microdose effects.