Radiation-Hardened Performance-Optimized I2L LSI
Experimental data and theoretical calculations are presented on the effects of neutron irradiation on I2L circuits. It is shown that neutron-induced degradation of I2L gate performance can be theoretically predicted with reasonable accuracy. Operation of custom designed I2L 32-bit serial shift registers to a neutron fluence level of 1 × 1014n/cm2 is demonstrated. Shift register data are also given from total dose gamma and transient upset radiation experiments with thresholds exceeding 3 × 106rads(Si) and 2 × 109rads(Si)/s, respectively.
Approaches to Radiation-Hardened I2L Technology
Design techniques are described for achieving radiation-hardened Schottky-base I2L (SBI2L) circuits. Radiation performance data are presented for this new technology and compared with results for conventional I2L. A design technique is also described for optimizing the intrinsic base sheet resistance in conventional or Schottky-base I2L. This concept is extended to VLSI designs. Finally, as an application of SBI2L, a new design is presented for a radiation-hardened static random-access-memory (RAM) cell.
Effect of Injection Level on Carrier Lifetime in Neutron-Irradiated Germanium
The dependence of minority carrier lifetime on injection level was analyzed to yield recombination center parameters for neutron-irradiated germanium. The results are an improvement over data obtained by other methods because they eliminate a possible dependence of capture probability on temperature, and are more sensitive to energy level position. Six n-type specimens doped with arsenic and antimony in the resistivity range from one to twenty ohm-cm were studied. The results reveal a recombination center level of Er - Ev = 0. 34 ± 0.01 eV for antimony-doped germanium and Er - Ev = 0.335 ± 0.01 eV for arsenic-doped germanium. The dependence of lifetime on injection level for high excitation demonstrated the appropriateness of the model which includes the effect of a level of Ec - Er ~ 0.2 eV.