4 Irradiation Facility and Setup

The SEE testing described in this test report was performed at the Cyclotron Institute at Texas A&M University (TAMU) using their K500 Cyclotron. The testing was performed in air using the 15 MeV/n beam. When necessary, beam degraders were inserted into the beam line to achieve the desired LET and a wider LET range for a given ion. The beam characteristics and dosimetry were provided by the Texas A&M heavy ion test facility. TAMU delivered the beam with a high degree of uniformity over a 1in diameter circular cross sectional area using the in-air test system. Uniformity was achieved by magnetic defocusing and by thin foil scattering. The beam uniformity and flux are determined using an array of five plastic scintillators coupled to photo multiplier tubes, located in the diagnostic chamber adjacent to and upstream from the target. Four of the five detectors are fixed in position and set up to measure beam particle counting rates continuously at four characteristic points 1.64 inches (41.7mm) away from the beam axis center. The fifth scintillator is inserted to measure the beam particle counting rate right at the beam axis and was removed to provide an unobstructed beam during testing. The control software determines the beam uniformity (ranging from 0% to 100%), axial gain (%), and beam flux (in particles/cm²/s) based on the scintillator counting rates. The parameters are displayed on the computer screen in the control room and are updated about once every second. For all beam experiments the air gap between the die surface and the ion port window was 40mm.

Figure 4-1 shows a photograph of the test fixture used for SEE testing. All DUT were de-lidded prior to testing and all exposures took place from the top surface providing a distance to the active layer in silicon, through the passivation and metallization layers of approximately 10µm.