An Investigation of Dose Rate and Source Dependent Effects in 200 GHz SiGe HBTs

Abstract

We present an investigation of the observed variations in the total dose tolerance of the emitter-base spacer and shallow trench isolation oxides in a commercial 200 GHz SiGe HBT technology. Proton, gamma, and X-ray irradiations at varying dose rates are found to produce drastically different degradation signatures at the various oxide interfaces. Extraction and analysis of the radiation-induced excess base current, as well as low-frequency noise, are used to probe the underlying physical mechanisms. Two-dimensional calibrated device simulations are employed to correlate the observed results to the spatial distributions of carrier recombination in forward-and inverse-mode operation for both pre-and post-irradiation levels. Possible explanations of our observations are offered and the implications for hardness assurance testing are discussed.

A Comparison of the Effects of X-Ray and Proton Irradiation on the Performance of SiGe Precision Voltage References

“…8 and 12 indicates that the degradation in the circuit performance is radiation source dependent and proton irradiation shows less degradation than X-ray irradiation. This difference could be attributed to the fact that at the transistor level, the increase in the base leakage current is smaller for protons than for X-rays, as discussed in [11], [12]. This is also observed by comparing Figs.…”

“…10 and 13 which show that at the base-emitter voltage of 0.7 V, and at room temperature, the base current after X-ray exposure changes by almost 100 nA, while it changes by less than 20 nA after proton irradiation (at the same effective dose). This difference in the degradation induced by X-rays and protons, as discussed in [11], may lie in dose enhancement effects, as low energy X-rays pass through high-materials such as the copper layers and the tungsten vias of the metal interconnections.…”

“…In deriving (1), it has been assumed that the base current is negligible. However, as it has been discussed in [11], [12], the base leakage current increases after X-ray radiation and therefore, cannot be neglected after exposures to these dose levels. The increase in the post-irradiation base current is due to creation of positive charge in the emitter-base (EB) oxide spacer and increase in the number of traps at the EB spacer oxide/silicon interface, which results in increased surface recombination velocity [20].…”

“…However, no studies have been carried out to investigate the effects of radiation source on the performance of SiGe circuits. At the device level, differences in the degradation induced by 10 keV X-rays and 63.3 MeV protons have been observed [11], [12], and provides clear motivation to determine if these source dependent differences will be encountered at the circuit level, affecting the overall circuit performance.…”

10 Bit and 12 Bit data conversion achievements at microwave frequencies on 200GHz SiGeC (Bipolar) and 120GHz 0.18µm BiCMOS technology

“…Furthermore, the 200 GHz fT is achieved with very low current densities for transistors, thus enabling low power for the 12 Bit 1.5GS/s ADC (3.2W) and 1.3Watt for the 12 Bit 3GS/s DAC including the embedded 4:1 MUX.Hence the parts could be packaged in a small fPBGA196 plastic package. Moreover, inherent radiation tolerance property of vertical isolated SiGeC HBTs [9] …”