High LET radiation effects microscopy for ICs

Abstract

Radiation effects microscopy (REM) has been used at Sandia National Laboratories (SNL) for several years to study radiation hard ICs. As ICs become more radiation hardened, ions with larger linear energy transfer (LET) are needed to study their response to radiation. This higher LET can be achieved by using high energy, heavy ions. To carry out REM on ICs, the ion beam has to be focused to a submicron spot, which is very problematic for these ions. A new high LET system was developed at SNL, which combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional tandem Van de Graaff-pelletron to velocities of 1.9 MeV/amu. To circumvent the problem of focusing high-energy ions, we invented ion-electron emission microscopy (IEEM). Instead of focusing the ion beam and scanning it over the device under test (DUT), the positions of the ion hits are determined by projecting ion-induced secondary electrons at high magnification onto a single-electron position sensitive detector (PSD). Then, the two position signals (x and y) are recorded in coincidence with each REM event. Details of the RFQ booster and the IEEM system are given with initial results on Sandia manufactured radiation hardened ICs.