5 Depth, Range, and LET_EFF Calculation

Figure 5-1 Generalized Cross-Section of the LBC7 Technology BEOL Stack on the TPS7H2201-SEP (Left) and SEUSS 2022 Application Used to Determine Key Ion Parameters (Right)

The TPS7H2201-SEP is fabricated in the TI Linear BiCMOS 7 (LBC7, 250-nm process with a Back-End-Of-Line (BEOL) stack consisting of four levels of standard thickness aluminum metal. The total stack height from the surface of the passivation to the silicon surface is 13.5 μm based on nominal layer thickness as shown in Figure 5-1. Accounting for energy loss through the 1-mil thick Aramica beam port window, the 40-mm air gap and the BEOL stack over the TPS7H2201-SEP, the effective LET (LET_EFF) at the surface of the silicon substrate, the depth, and the ion range was determined with the SEUSS 2020 Software (provided by the Texas A&M Cyclotron Institute and based on the latest SRIM-2013 (7) models). Table 5-1 lists the results. The stack was modeled as a homogeneous layer of silicon dioxide (valid since SiO₂ and aluminum density are similar).