Akil K. Sutton

Multiple-Bit Upset in 130 nm CMOS Technology

The probability of proton-induced multiple-bit upset (MBU) has increased in highly-scaled technologies because device dimensions are small relative to particle event track size. Both proton-induced single event upset (SEU) and MBU responses have been shown to vary with angle and energy for certain technologies. This work analyzes SEU and MBU in a 130 nm CMOS SRAM in which the single-event response shows a strong dependence on the angle of proton incidence. Current proton testing methods do not account for device orientation relative to the proton beam and, subsequently, error rate prediction assumes no angular dependencies. Proton-induced MBU is expected to increase as integrated circuits continue to scale into the deep sub-micron regime. Consequently, the application of current testing methods will lead to an incorrect prediction of error rates

Application of RHBD Techniques to SEU Hardening of Third-Generation SiGe HBT Logic Circuits

Shift registers featuring radiation-hardening-by-design (RHBD) techniques are realized in IBM 8HP SiGe BiCMOS technology. Both circuit and device-level RHBD techniques are employed to improve the overall SEU immunity of the shift registers. Circuit-level RHBD techniques include dual-interleaving and gated-feedback that achieve SEU mitigation through local latch-level redundancy and correction. In addition, register-level RHBD based on triple-module redundancy (TMR) versions of dual-interleaved and gated-feedback cell shift registers is also realized to gauge the performance improvement offered by TMR. At the device-level, RHBD C-B-E SiGe HBTs with single collector and base contacts and significantly smaller deep trench-enclosed area than standard C-B-E-B-C devices with dual collector and base contacts are used to reduce the upset sensitive area. The SEU performance of these shift registers was then tested using heavy ions and standard bit-error testing methods. The results obtained are compared to the unhardened standard shift register designed with CBEBC SiGe HBTs. The RHBD-enhanced shift registers perform significantly better than the unhardened circuit, with the TMR technique proving very effective in achieving significant SEU immunity

An Evaluation of Transistor-Layout RHBD Techniques for SEE Mitigation in SiGe HBTs

We investigate transistor-level layout-based techniques for SEE mitigation in advanced SiGe HBTs. The approach is based on the inclusion of an alternate reverse-biased pn junction (n-ring) designed to shunt electron charge away from the sub-collector to substrate junction. The inclusion of the n-ring affects neither the DC nor AC performance of the SiGe HBT and does not compromise its inherent multi-Mrad TID tolerance. The effects of ion strike location and angle of incidence, as well as n-ring placement, area, and bias on charge collection are investigated experimentally using a 36 MeV O2 microbeam. The results indicate that charge shunting through the n-ring can result in up to a 90% reduction in collector collected charge for strikes outside the DT and a 18% reduction for strikes to the emitter center. 3-D transient strike simulations using NanoTCAD are used to verify the experimental observations, as well as shed insight into the underlying physical mechanisms. Circuit implications for this RHBD technique are discussed and recommendations made.

Proton tolerance of fourth-generation 350 GHz UHV/CVD SiGe HBTs

We report, for the first time, the impact of proton irradiation on fourth-generation SiGe heterojunction bipolar transistors (HBTs) having a record peak unity gain cutoff frequency of 350 GHz. The implications of aggressive vertical scaling on the observed proton tolerance is investigated through comparisons of the pre-and post-radiation ac and dc figures-of-merit to observed results from prior SiGe HBT technology nodes irradiated under identical conditions. In addition, transistors of varying breakdown voltage are used to probe the differences in proton tolerance as a function of collector doping. Our findings indicate that SiGe HBTs continue to exhibit impressive total dose tolerance, even at unprecedented levels of vertical profile scaling and frequency response. Negligible total dose degradation in /spl beta/ (0.3%), f/sub T/ and f/sub max/(6%) are observed in the circuit bias regime, suggesting that SiGe HBT BiCMOS technology is potentially a formidable contender for high-performance space-borne applications.

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

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 gamma and proton radiation effects in 200 GHz SiGe HBTs

We present the results of gamma irradiation on third-generation, 200 GHz SiGe HBTs. Pre- and post-radiation dc figures-of-merit are used to quantify the tolerance of the raised extrinsic base structure to Co-60 gamma rays for varying device geometries. Additionally, the impact of technology scaling on the observed radiation response is addressed through comparisons to second generation, 120 GHz SiGe HBTs. Comparisons to previous proton-induced degradation results in these 200 GHz SiGe HBTs are also made, and indicate that the STI isolation oxide of the device shows increased degradation following Co-60 irradiation. The EB spacer oxide, on the other hand, demonstrates increased susceptibility to proton damage. Low dose rate proton testing was also performed and indicate that although there is a proton dose rate effect present in these devices, it cannot fully explain the observed trends. Similar trends have previously been observed for buried oxides and isolation oxides in several MOS technologies and have been attributed to increased charge yield in these oxides for 1.2 MeV Co-60 gamma rays when compared to 63 MeV protons.

The Effects of Irradiation Temperature on the Proton Response of SiGe HBTs

We compare, for the first time, the effects of 63 MeV protons on 1st generation and 3rd generation SiGe HBTs irradiated at both liquid nitrogen temperature (77 K) and at room temperature (300 K). The 1st generation SiGe HBTs irradiated at 77 K show less degradation than when irradiated at 300 K. Conversely, the 3rd generation SiGe HBTs exhibits an opposite trend, and the devices irradiated at 77 K show enhanced degradation compared to those irradiated at 300 K. The emitter-base spacer regions for these two SiGe technologies are fundamentally different in construction, and apparently are responsible for the observed differences in temperature-dependent radiation response. At practical circuit biases, both SiGe technology generations show only minimal degradation for both at 77 K and 300 K exposure, to Mrad dose levels, and are thus potentially useful for electronics applications requiring simultaneous cryogenic temperature operation and significant total dose radiation exposure

Substrate Engineering Concepts to Mitigate Charge Collection in Deep Trench Isolation Technologies

Delayed charge collection from ionizing events outside the deep trench can increase the SEU cross section in deep trench isolation technologies. Microbeam test data and device simulations demonstrate how this adverse effect can be mitigated through substrate engineering techniques. The addition of a heavily doped p-type charge-blocking buried layer in the substrate can reduce the delayed charge collection from events that occur outside the deep trench isolation by almost an order of magnitude, implying an approximately comparable reduction in the SEU cross section

A 2 mW, Sub-2 dB Noise Figure, SiGe Low-Noise Amplifier For X-band High-Altitude or Space-based Radar Applications

This paper presents a low-power X-band low-noise amplifier (LNA) implemented in silicon-germanium (SiGe) technology targeting high-altitude or space-based low-power density phased-array radar systems. To our knowledge, this X-band LNA is the first in a Si-based technology to achieve less than 2 dB mean noise figure while dissipating only 2 mW from a 1.5 V power supply. The gain of the circuit is 10 dB at 10 GHz with an IIP 3 of 0 dBm. In addition to standard amplifier characterization, the LNAs total dose radiation response has been evaluated.

Laser-Induced Current Transients in Silicon-Germanium HBTs

Device-level current transients are induced by injecting carriers using two-photon absorption from a subbandgap pulsed laser and recorded using wideband transmission and measurement equipment. These transients exhibit three distinct temporal trends that depend on laser pulse energy as well as the transverse and vertical charge generation location. The nature of the current transient is controlled by both the behavior of the subcollector-substrate junction and isolation biasing. However, substrate potential modulation, due to deformation of the subcollector-substrate depletion region, is the dominant mechanism affecting transient characteristics.