Adilson S. Cardoso

A 0.8 THz

We demonstrate record ac performance (0.8 THz) for a silicon-germanium heterojunction bipolar transistor (SiGe HBT) operating at cryogenic temperatures. An extracted peak fMAX of 798 GHz (peak fT of 479 GHz) at 4.3 K was measured for a device with a BVCEO of 1.67 V. This scaled SiGe HBT also exhibits excellent thermal properties, as required from an electro-thermal reliability perspective. Taken together, these results strongly suggest that at the limits of scaling, robust, and manufacturable SiGe HBTs designed for room temperature operation are likely to achieve THz speeds.

f_{\rm MAX}

The single-event effect sensitivity of fourth-generation, 90 nm SiGe HBTs is investigated. Inverse-mode, ≥1.0 Gbps SiGe digital logic using standard, unoptimized, fourth-generation SiGe HBTs is demonstrated and the inverse-mode shift register exhibited a reduction in bit-error cross section across all ion-strike LETs. Ion-strike simulations on dc calibrated, 3-D TCAD SiGe HBT models show a reduction in peak current transient magnitude and a reduction in overall transient duration for bulk SiGe HBTs operating in inverse mode. These improvements in device-level SETs are attributed to the electrical isolation of the physical emitter from the subcollector-substrate junction and the high doping in the SiGe HBT base and emitter, suggesting that SiGe BiCMOS technology scaling will drive further improvements in inverse-mode device and circuit-level SEE. Two-photon absorption experiments at NRL support the transient mechanisms described in the device-level TCAD simulations. Fully-coupled mixed-mode simulations predict large improvements in circuit-level SEU for inverse-mode SiGe HBTs in multi-Gbps, inverse-mode digital logic.

SiGe HBT Operating at 4.3 K

This paper presents an investigation of the impact of single-event transients (SETs) and total ionization dose (TID) on precision voltage reference circuits designed in a fourth-generation, 90-nm SiGe BiCMOS technology. A first-order uncompensated bandgap reference (BGR) circuit is used to benchmark the SET and TID responses of these voltage reference circuits (VRCs). Based on the first-order BGR radiation response, new circuit-level radiation-hardening-by-design (RHBD) techniques are proposed. An RHBD technique using inverse-mode (IM) transistors is demonstrated in a BGR circuit. In addition, a PIN diode VRC is presented as a potential SET and TID tolerant, circuit-level RHBD alternative.

An Investigation of Single-Event Effects and Potential SEU Mitigation Strategies in Fourth-Generation, 90 nm SiGe BiCMOS

The total ionizing dose response of 4th-generation SiGe HBTs is assessed at both low and high dose rates to evaluate enhanced low dose rate sensitivity (ELDRS) in a new SiGe BiCMOS technology. Both device and circuit results are presented. A bandgap reference circuit topology is chosen to monitor for ELDRS in TID-induced collector current shifts, which have previously been reported in low dose rate studies of SiGe HBTs. The results in this paper also cover previous technology generations from this foundry in order to incorporate a broader view of dose rate effects in SiGe HBTs. No indication of ELDRS was found in any technology generation.

Single-Event Transient and Total Dose Response of Precision Voltage Reference Circuits Designed in a 90-nm SiGe BiCMOS Technology

The single-event effect sensitivity of three different commonly employed current mirror circuits, as well as an unconventional inverse-mode current mirror, all implemented in C-SiGe (NPN + PNP) HBT on SOI technology are investigated. Comparisons of the measured data of the basic NPN and PNP current mirror circuits show higher single-event radiation tolerance of PNP SiGe HBTs compared with NPN SiGe HBTs. The concept of utilizing inverse-mode SiGe HBTs in current mirror circuits is investigated. Measurement results validate the feasibility of employing inverse-mode PNP SiGe HBTs in current mirrors and show an excellent resilience against ion-strikes. Full 3-D NanoTCAD models of the SiGe HBTs are developed and used in mixed-mode TCAD simulations (within Cadence) to validate the measurement results. Finally, based on the measurement data and analysis of the four current mirrors, some practical suggestions and observations are offered for operation of such circuits in extreme environments.

Evaluation of Enhanced Low Dose Rate Sensitivity in Fourth-Generation SiGe HBTs

The effects of 63 MeV proton irradiation on the RF performance (insertion loss, isolation, and linearity) of triple-well nFET-based RF switches designed in a 130 nm SiGe BiCMOS technology are investigated. The switches were designed for wide-band operation (1 to 40 GHz) and were required by the application to achieve high isolation (> 35 dB at 40 GHz) with moderate insertion loss (dB at 40 GHz). The RF switch IL improves (S21 increases) at 100 and 500 krad(SiO2), but degrades (S21 decreases) at 2 Mrad(SiO2). P1dB and IIP3 (switch linearity) shows a similar TID response, at 100 and 500 krad(SiO2) dose an increase of ~ 0.4 dBm and ~0.2 dBm, respectively. However, at 2 Mrad(SiO2) both sharply decrease. Standalone RF and dc structures were also irradiated to better understand the underlying mechanisms affecting the switch RF performance. The bias dependence of the radiation-induced change on the measured RF performance of a SPST switch is also analyzed. 10 keV X-ray radiation experiments were conducted on separate dc transistor structures to provide additional insight into the measured impact of total ionization dose on the performance of RF switches.

An Investigation of Single-Event Transients in C-SiGe HBT on SOI Current Mirror Circuits

The impact of single event transients (SETs) on single-pole double-throw (SPDT) RF switch circuits designed in a commercially-available, 180 nm second-generation SiGe BiCMOS (IBM 7HP) technology is investigated. The intended application for these SPDT RF switches requires a 1 GHz to 20 GHz band of operation, relatively low insertion loss (<; 3.0 dB at 20 GHz), and moderate isolation (> 15 dB at 20 GHz). Two-photon absorption experiment results reveal that the SPDT switches are vulnerable to SETs due to biasing effects as well as the triple-well (TW) nFETs, which are found to be more sensitive to SETs than bulk nFETs. From these results, potential implications are discussed and mitigation strategies are proposed. To verify one of the proposed mitigation techniques, SPDT switches were also designed in a 180 nm twin-well SOI CMOS (IBM 7RF-SOI) technology. A different biasing technique is implemented to help improve the SET response. The fabricated SOI SPDT switches achieve an insertion loss of <; 1.04 dB at 20 GHz and > 21 dB isolation at 20 GHz. For this circuit, no transients were observed even at very high laser energies (≈ 5 nJ).

Total Ionizing Dose Response of Triple-Well FET-Based Wideband, High-Isolation RF Switches in a 130 nm SiGe BiCMOS Technology

A wideband (8-18 GHz) built-in test receiver in silicon-germanium technology is presented. The receiver chain consists of a low-noise amplifier (LNA), an image-reject mixer, on-chip automatic gain control ring oscillator sources that are used to provide test signals of a predefined amplitude, and control circuitry in the form of digital-to-analog converters and data registers. Both the LNA and the mixer circuit blocks incorporate tuning knobs to enable tuning of RF metrics to ensure consistent performance and mitigate the negative effects of process, voltage, and temperature variations, aging, and damage from extreme environments such as ionizing radiation. A maximum post-healed gain greater than 30 dB, an image rejection ratio exceeding 30 dB, output third-order intercept point greater than 8 dBm, and noise figure less than 9 dB are obtained in measurement. An automated healing algorithm was developed and shown to be effective at improving the overall performance of the receiver. The receiver was fabricated in an 0.18- μm SiGe BiCMOS process with a peak fT of 150 GHz, and consumes 240-260 mA from a 4-V supply.

Evaluating the Effects of Single Event Transients in FET-Based Single-Pole Double-Throw RF Switches

The single-event transient (SET) response of a third-generation bulk C-SiGe ( npn + pnp) BiCMOS platform is investigated for the first time. Pulsed-laser, two-photon absorption experiments show that the pnp SiGe heterojunction bipolar transistor (SiGe HBT) exhibits a significant reduction in sensitive area as well as an improved transient response compared with the npn SiGe HBT. Ion-strike simulations on 3-D TCAD, C-SiGe HBT models agree with experimental findings, showing a reduction in overall transient duration and collected charge for the pnp SiGe HBT. These improvements in device-level SETs are attributed to the n-well isolation layer present in the vertical material stack of the pnp HBT. These results suggest that precision analog, RF/mm-wave, and high-speed digital applications utilizing unhardened, high-performance bulk pnp SiGe HBTs should benefit from an inherently improved SEE response.

A SiGe 8–18-GHz Receiver With Built-In-Testing Capability for Self-Healing Applications

This paper uses charge deposition by two-photon absorption to present the first investigation of the physical mechanisms underlying the single event transient (SET) response of cascode structures in a 45-nm RF-CMOS/SOI technology, provides the first experimental comparison of SET between 45-nm and 32-nm RF-CMOS/SOI devices, and presents implications for circuit design in both technologies. This work leverages a number of different device types and is supported by calibrated TCAD simulations.