Determination of funnel length from cross section versus LET measurements

Proposes an empirical model and method for determining the funnel length from heavy ion upset cross sections as a function of LET (linear energy transfer) data. It is valid for bulk technologies having a lightly doped epi region over a heavily doped substrate region. The proposed method is applied to 8 K×8 K SRAM (static random-access memory) heavy ion SEU (single event upset) test data. It is shown that the primary cause of discontinuities decreases in the upset cross section even though the surface normal effective LET has increased in the upset cross section versus surface normal effective LET curves. This is due to inappropriate conversion of the ion LET into surface normal effective LET. Previous attempts to resolve these discontinuities focused on modifying the upset cross section. The proposed model focuses on the conversion from ion LET to surface normal effective LET. The discontinuities are significantly reduced by modifying the traditionally used 1/cos conversion equation