IEC 60749-38 pdf download Semiconductor devices – Mechanical and climatic test methods – Part 38: Soft error test method for semiconductor devices with memory
3 Test apparatus
3.1 Measurement equipment The equipment shall be capable of measuring the functions of the integrated circuit devices, and capable of measuring the time taken for the change of stored data by the exposure to energetic particles, such as alpha radiation to take place (i.e. the generation of a soft error). Alternatively, the test equipment (memory tester etc.) shall have the capability of counting the number of soft errors in unit time.
3.2 Alpha radiation source
3.2.1 Background information Uranium and thorium impurities found in trace amounts in the various production and packaging materials emit alpha particles. Alpha particles are strongly ionizing, so those that impinge on the active device create bursts of free electron-hole pairs in the silicon. Different types of alpha sources can be used to simulate the alpha emission from uranium and thorium impurities. Sources that emit alpha particles with energy spectra similar to uranium and thorium impurities simulate the radiation environment of wirebonded components encapsulated in moulding compound. Sources that emit alpha particles with similar energy spectra to 21 0 Po are used for simulating components in a flip-chip arrangement with solder bumps. The source should provide an alpha particle spectrum similar to that encountered in the actual component.
3.2.2 Preferred sources 238 U or 232 Th are the preferred sources for inducing SER in mould-resin compounds. 241 Am and 21 0 Po sources can be used as substitutes.
3.2.3 Variation in results Results will differ depending on the source used due to spectral variations. Alpha particle sources available on the market are usually only classified by their activities in μCi (rather than in the preferred unit, Bq, see 2.11 ) and the emission rates of alpha particle are seldom indicated. The emission rate cannot be determined simply from the activities because of the effects of absorption of alpha particle in the source itself and its situation.
For example, the activity of 1 μCi is 3,7 × 1 0 4 decays/s. However, the alpha emission rate from the source would be less than 3,7 × 1 0 4 alpha/s. Therefore, a measurement of the alpha emission rate of the source which is used in the SER test is recommended. As a consequence, the energy spectrum of the alpha radiation source shall be confirmed because different test values can result from differing energy spectra even if the alpha radiation sources have the same level of radioactivity.
NOTE If 241 Am or 21 0 Po are used, this should be documented in a report along with the statement that results can differ if other sources have been used, due to energy spectra variations.
3.2.4 Effect of high radiation levels In cases where the dose concentration delivered to the test sample is high, consideration shall be given to the effect of multiple hits.