Bipolar Microcircuits Research Articles

Bias Effects on Total Dose-Induced Degradation of Bipolar Linear Microcircuits for Switched Dose-Rate Irradiation

Accelerated test techniques are needed in order to qualify bipolar devices intended for use in low dose rate environments. Indeed, low dose rate is known to enhance degradation of bipolar devices. Moreover, the bias of microcircuits is known to play a significant role in device degradation. In this work, bipolar microcircuits are irradiated with different bias configurations during the irradiation. It is shown that the bias configuration leading to the worst-case degradation is dose-rate dependent. Moreover, if a time-saving evaluation technique based on dose-rate switching is to be used, the effect of bias has to be investigated. In this work, this time-saving technique, the switched dose-rate technique, is applied for the first time to evaluate the behavior of dynamics parameters of a bipolar IC irradiated all pins grounded, and also to evaluate the behavior of static and dynamics parameters of bipolar ICs irradiated under several bias configurations. Good agreement is found between the predictive curve obtained with the switched dose-rate technique and the low dose rate data.

Estimation of low-dose-rate degradation on bipolar linear integrated circuits using switching experiments

The low-dose-rate response of five bipolar integrated circuits is evaluated on the basis of switching experiments. Such experiments consist of performing first a high-dose-rate irradiation followed by a low-dose-rate irradiation. Based on these experiments, a time-saving method to predict the low-dose-rate degradation of bipolar linear microcircuits is proposed. This approach provides a good estimate of the low-dose-rate degradation.

The effects of neutron irradiation on gamma sensitivity of linear integrated circuits

A dozen linear bipolar microcircuits were first irradiated with neutrons then gammas and compared to the same devices exposed to gammas only. The data show that neutron irradiation can affect subsequent total dose behavior. This has significant hardness assurance implications.

Total dose effects on bipolar integrated circuits: characterization of the saturation region

The total-dose response of bipolar microcircuits is investigated. A recovery of the degradation is observed for high total dose in the saturation region. The circuit response in this region is studied based on room temperature annealing. The role of the electric field is studied and the results are discussed in terms of hardness assurance.

Origins of total-dose response variability in linear bipolar microcircuits

LM111 voltage comparators exhibit a wide range of total-dose-induced degradation. Simulations show this variability may be a natural consequence of the low base doping of the substrate PNP (SPNP) input transistors. Low base doping increases the SPNPs collector to base breakdown voltage, current gain, and sensitivity to small fluctuations in the radiation-induced oxide defect densities. The build-up of oxide trapped charge (N/sub OT/) and interface traps (N/sub IT/) is shown to be a function of pre-irradiation bakes. Experimental data indicate that, despite its structural similarities to the LM111, irradiated input transistors of the LM124 operational amplifier do not exhibit the same sensitivity to variations in pre-irradiation thermal cycles. Further disparities in LM111 and LM124 responses may result from a difference in the oxide defect build-up in the two part types. Variations in processing, packaging, and circuit effects are suggested as potential explanations.

Dependence of total dose response of bipolar linear microcircuits on applied dose rate

The effect of dose rate on the total dose radiation hardness of three commercial bipolar linear microcircuits is investigated. Total dose tests of linear bipolar microcircuits show larger degradation at 0.167 rad/s than at 90 rad/s even after the high dose rate test is followed by a room temperature plus a 100/spl deg/C anneal. No systematic correlation could be found for degradation at low dose rate versus high dose rate and anneal. Comparison of the low dose rate with the high dose rate anneal data indicates that MIL-STD-883, Method 1019.4 is not a worst-case test method when applied to bipolar microcircuits for low dose rate space applications. >

Total dose induced hole trapping in trench oxides

Ionization effects in polysilicon-filled trenches used for component isolation in an advanced commercial bipolar technology are examined. Contact to the trench polysilicon was used to sweep the subthreshold characteristics of a parasitic trench field-effect transistor formed by the trench and two buried layers. The subthreshold-charge-separation technique was used to analyze the buildup of trapped holes and interface states. For typical microcircuit layouts, the irradiation data at a total dose of greater than 1 Mrad(SIO/sub 2/) showed identical saturation of the threshold voltage shift and minimal interface-stage buildup regardless of the source and drain irradiation bias conditions. However, the radiation responses for the various irradiation bias conditions prior to saturation were significantly different. The complex irradiation response and implications for the use of trenched bipolar microcircuits in radiation environments are discussed. >

Total Dose Indujced Hole Trapping and Interface State Generation in Bipolar Recessed Field Oxides

Ionizing radiation induced trapped hole density, Not, and interface state density, Nit, are investigated in bipolar recessed field oxides using parasitic nMOS transistors. Most of the results agree with previous studies made with capacitors on generic thick field oxides. New results include the effects of PN junction fringing fields on inversion voltage shift. Implications are made for total dose failure of bipolar microcircuits based on results of inversion voltage shift versus channel length and channel doping density. under contract DNA001-83-C-0115.

Total Dose Effects in Recessed Oxide Digital Bipolar Microcircuits

Total dose failure levels in digital bipolar microcircuits utilizing recessed oxides were measured at levels as low as 5 Krad(Si). Typical failure levels are in the 10-100 Krad(Si) range. Failure was found to be a strong function of irradiation bias and annealing time after irradiation. In addition, total dose windows below 100 Krad(Si) were observed. The radiation failure mechanism is predominantly inversion of p type silicon either at the bottom of the recessed field oxide, causing buried layer to buried layer channeling, or on the oxide sidewall causing collector to emitter leakage. In addition, a failure mode due to increased sidewall current was observed in a nonisolated form of integrated injection logic. Hardening approaches have been identified and investigated at several manufacturers. Device failure levels were found to vary by several orders of magnitude depending on process lot and layout revision.

Microcircuit operation observed by the stimulation of electro-optic responses in nematic liquid-crystals

The application to microcircuits of the electrooptic effects in nematic liquid crystals-normally employed in visual displays-has been investigated using special test structures and active devices. Two electro-optic phenomena have been observed, and the sensitivity to surface potentials and fields estimated. The functioning of both low-voltage bipolar and higher-voltage MOS microcircuits having overglazed dice has been examined qualitatively, but only with AC or pulsed operation at audio frequencies governed by the voltages present. The technique requires a little acquired skill, and simple equipment.

US Army Panama field test of plastic encapsulated devices

Over 175 million device hours have been accumulated on 5688 transistors and 1316 bipolar microcircuits in seven years of testing in the Panama Canal Zone. Failure rates and failure modes of biased and stored plastic encapsulated devices are detailed. The data indicate that certain plastic packaged microcircuits have performed as well as hermetic ceramic units on this test. Preliminary CMOS reliability information is also presented.

US Army Panama field test of plastic encapsulated devices : Edward B. Hakim. Microelectron. Reliab.17, 387 (1978)

Abstract Over 175 million device hours have been accumulated on 5688 transistors and 1316 bipolar microcircuits in seven years of testing in the Panama Canal Zone. Failure rates and failure modes of biased and stored plastic encapsulated devices are detailed. The data indicate that certain plastic packaged microcircuits have performed as well as hermetic ceramic units on this test. Preliminary CMOS reliability information is also presented.

Influence of p-n Junctions on the Mobile Charge Density in MOS Transistors

Empirical data shows that the mobile charge density in the oxides of MOS and bipolar microcircuits depends on the proximity of a p-n junction. This data is consistent with a model in which positive mobile ions migrate from oxides over n-regions to those over p-regions. Several practical consequences of this phenomenon are discussed.