DOI: 10.1007/s10967-008-0914-1 Journal of Radioanalytical and Nuclear Chemistry, Vol. 278, No.2 (2008) 509–512 0236–5731/USD 20.00 Akadémiai Kiadó, Budapest © 2008 Akadémiai Kiadó, Budapest Springer, Dordrecht Thermal neutron induced soft error rate measurement in semiconductor memories and circuits C. Çelik, 1 K. Ünlü, 1 * K. Ramakrishnan, 2 R. Rajaraman, 2 V. Narayanan, 2 M. J. Irwin, 2 Y. Xie 2 1 Radiation Science and Engineering Center, Penn State University, University Park, PA 16802, USA 2 Department of Computer Science and Engineering, Penn State University, University Park, PA 16802, USA (Received July 10, 2008) Soft error rate (SER) testing and measurements of semiconductor circuits with different operating voltages and operating conditions have been performed using the thermal neutron beam at the Radiation Science and Engineering Center (RSEC) at Penn State University. The high neutron flux allows for accelerated testing for SER by increasing reaction rate densities inside the tested device that gives more precision in the experimental data with lower experimental run time. The effect of different operating voltages and operating conditions on INTEL PXA270 processor has been experimentally determined. Experimental results showed that the main failure mechanism was the segmentation faults in the system. Failure response of the system to the operating conditions was in agreement with the general behavior of SERs. Introduction A single-event upset or soft error is the sensitivity of semiconductor memories and circuits to environmental radiation. The environmental radiation creates excess charge carriers that directly or indirectly induces localized ionization, which can change the state of the internal values of the memory cells and cause wrong data to get latched onto the output of the combinational circuits. Initial experimental results of SER measurements for thermal neutron-induced SER on semiconductor memories have been published previously. 1 The majority of detected errors in memory chips originate from transient failures and results can be found in the literature. 2,3 As the technology improves, SER will significantly affect reliability and dependability of the semiconductor memories. SER measurements and testing of devices have been reported in the literature extensively. 4–6 In the past, experiments were carried out with alpha-particles to study their effects on memories and showed that the effects of borophosphosilicate glass (BPSG) layers on SER could be avoided by reducing the SER due to 10 B containment. 7–11 In this paper, SER measurements for PXA270 microprocessor at the Penn State Breazeale Reactor (PSBR) using thermal neutrons are discussed. Currently, fast neutron effects are being explored to observe effects of higher-energy neutrons on circuit operation and SER. In addition, simulations of SER in semiconductor circuits for verifying the experimental results are also being studied. * E-mail: k-unlu@psu.du Experimental setup The Radiation Science and Engineering Center (RSEC) at Pennsylvania State University served as the test facility for the SER measurement. The Penn State Breazeale Reactor (PSBR) [TRIGA] was used as the neutron source in the experiments. The maximum rated power of the reactor is 1 MW in the continuous mode, and 2000 MW in the pulse mode. The reactor power is adjusted from 10 W to 1 MW to observe the soft error rate dependence on neutron flux. Figure 1 shows the experimental setup. In order to get a well-thermalized neutron beam, a D 2 O tank was used between the core and beam port. The average thermal flux at the exit of the beam port is about 3 . 10 7 n . cm –2. s –1 , and the fast flux is about three magnitudes smaller. The neutron spectrum, which was measured using a slow neutron chopper, was compared with the corresponding Maxwell Boltzmann distribution and was found to be fairly matching. The different power levels at PSBR allow us to characterize the soft error rate and categorize the different types of errors effectively. PSBR has the ability to produce fast neutrons (energy >1 MeV) and epithermal or thermal neutrons (energy <0.1 MeV) depending on the two types of tests namely the in-core and out-of-core tests. The neutron flux near the core is dominated by fast neutrons while the flux at the end of the beam port is dominated by the thermal neutrons due to the loss of energy during the passage of neutrons through a heavy water tank. The upper energy limit of the fast neutron flux is less than the maximum atmospheric neutron spectrum, but corresponds to dominant portion of the atmosphere neutron flux.