Adrian Ildefonso

Using TCAD Modeling to Compare Heavy-Ion and Laser-Induced Single Event Transients in SiGe HBTs

Silicon-germanium heterojunction bipolar transistor (SiGe HBT) models are used in technology computer aided design (TCAD) to investigate single event transients induced by heavy-ion broadbeam and pulsed-laser two-photon absorption sources. A comparison between transient waveforms is provided, the proper extraction of heavy-ion broadbeam transients is discussed (along with circuit implications), and basic laser strike profiles are implemented in TCAD to provide insight into future design practices for simulation software to be used to describe laser-induced upsets in terms of an effective linear energy transfer (LET).

An Investigation of Single-Event Effect Modeling Techniques for a SiGe RF Low-Noise Amplifier

The single-event transient (SET) response of a SiGe-based, L-band low-noise amplifier (LNA) is investigated, with a focus on providing recommendations for radiation event simulation techniques. Pulsed-laser, two-photon absorption experiments show that the SET sensitivity of the SiGe LNA is highly dependent on operating conditions and strike location. Time and frequency-domain analyses raise potential concerns for digital data modulated on RF carrier signals. Device and circuit-level ion-strike TCAD simulations are utilized to compare alternative simulation approaches, highlight the importance of parasitics on SET simulation accuracy, and suggest best practices for modeling radiation-induced transients within RF/mm-wave circuits.

On the potential of using SiGe HBTs on SOI to support emerging applications up to 300°C

For the first time, the high temperature (to 300°C) DC and AC performance of a > 100 GHz f_T/f_max SiGe HBTs on thick-film SOI are investigated for their potential use in emerging energy sector, automotive, and aerospace applications. Metrics such as current gain (β_F), BV_CEO, M-1, f_T, f_max are extracted from 24°C to 300°C and compared with a bulk SiGe HBT platform. The results demonstrate that while there are degradation to key device metrics at high temperatures, the devices are still usable over a wide temperature range. Additionally, while SOI is known for its high thermal resistance, it is demonstrated that the device is constrained by electrical effects rather than thermal effects at higher temperatures, which should therefore yield acceptable reliability.

On the Cryogenic RF Linearity of SiGe HBTs in a Fourth-Generation 90-nm SiGe BiCMOS Technology

Large-signal (P1 dB) and small-signal (OIP3) radio frequency (RF) linearities of silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) fabricated in a new fourth-generation 90-nm SiGe BiCMOS technology operating at cryogenic temperatures are investigated. The SiGe BiCMOS process technology has an fT/fmax of 300/350 GHz. SiGe HBTs with two different layout configurations, collector-base-emitter (CBE) and CBE-base-collector (CBEBC), were characterized over temperature. Both dc and ac figures-of-merit are presented to aid in understanding the linearity, and to provide an overall performance comparison between the two layout configurations. The extracted peak fT/fmax for CBE and CBEBC at 78 K are 387/350 and 420/410 GHz, respectively. The P1 dB and OIP3 linearity metrics for both configurations are comparable. Source- and load-pull measurements were performed at each temperature at 8 and 18 GHz, with the devices biased at a JC of 18 mA/μm2. Two-tone measurements over bias were also performed at 300 and 78 K with 50-Ω terminations for the source and load impedances. The 50 Ω results follow a similar response to the source-and load-pull measurements at 300 and 78 K, and demonstrate that the small-signal linearity of the SiGe HBTs is not adversely impacted by operation at cryogenic temperatures. The CBEBC configuration demonstrated the most consistent RF linearity performance at cryogenic temperature out of the two layout options.

Single-Event Transient Response of Comparator Pre-Amplifiers in a Complementary SiGe Technology

The single-event transient (SET) response of the pre-amplification stage of two latched comparators designed using either <italic>npn</italic> or <italic>pnp</italic> silicon-germanium heterojunction bipolar transistors (SiGe HBTs) is investigated via two-photon absorption (TPA) carrier injection and mixed-mode TCAD simulations. Experimental data and TCAD simulations showed an improved SET response for the <italic>pnp</italic> comparator circuit. 2-D raster scans revealed that the devices in the <italic>pnp</italic> circuit exhibit a reduction in sensitive area of up to 80% compared to their <italic>npn</italic> counterparts. In addition, by sweeping the input voltage, the sensitive operating region with respect to SETs was determined. By establishing a figure-of-merit, relating the transient peaks and input voltage polarities, the <italic>pnp</italic> device was determined to have a 21.4% improved response with respect to input voltage. This study has shown that using <italic>pnp</italic> devices is an effective way to mitigate SETs, and could enable further radiation-hardening-by-design techniques.

Modeling single-event transient propagation in a SiGe BiCMOS direct-conversion receiver

The propagation of single-event transient (SET) signals in a silicon–germanium direct-conversion receiver carrying modulated data is explored. A theoretical analysis of transient propagation, verified by simulation, is presented. A new methodology to characterize and quantify the impact of SETs in communication systems carrying modulated data is proposed. The proposed methodology uses a pulsed radiation source to induce distortions in the signal constellation. The error vector magnitude due to SETs can then be calculated to quantify errors. Two different modulation schemes were simulated: QPSK and 16-QAM. The distortions in the constellation diagram agree with the presented circuit theory. Furthermore, the proposed methodology was applied to evaluate the improvements in the SET response due to a known radiation-hardening-by-design (RHBD) technique, where the common-base device of the low-noise amplifier was operated in inverse mode. The proposed methodology can be a valid technique to determine the most sensitive parts of a system carrying modulated data.

An Investigation of the SET Response of Devices and Differential Pairs in a 32-nm SOI CMOS Technology

The single event effect (SEE) response of devices and differential pairs in a 32-nm SOI CMOS technology is explored using laser-induced carrier injection and TCAD simulations. Both nFETs and pFETs in this technology exhibit similar sensitive area to laser-induced SEE and are strongly dependent on the drain bias condition. TCAD simulations were conducted in order to confirm results and utilize a 3-D mixed-mode simulation approach to more accurately model testing conditions. The differential pair (diff. pair) circuit SEE response extends the discussion to include the use of these devices in a core analog/RF circuit block. The analysis includes the use of floating body (FB) and body-connected (BC) devices. Body-connected FETs tend to exhibit a transient response that is much shorter in duration when compared directly to its floating body counterpart.

Total Ionizing Dose Effects on a High-Voltage (>30V) Complementary SiGe on SOI Technology

Total ionizing dose (TID) effects are evaluated for a high-voltage (>30 V) complementary SiGe on SOI technology. Devices are irradiated with 10-keV X-rays at doses up to 5 Mrad(SiO2). The results depend strongly on collector-to-emitter bias, in both forward- and inverse-mode. An anomalous reduction in current gain at high injection in forward-mode operation is observed at doses >500 krad(SiO2). Calibrated 2-D TCAD simulations suggest that this high injection phenomenon is primarily due to interface traps near the STI/Si interface, which is exhibited as a collector resistance increase in the forward Gummel characteristics. Additionally, a strong collector doping dependence is observed, which indicates that this is primarily driven by the thick and lightly doped collector used in this technology. These results illustrate, that high concentrations of interface traps at the STI can have a strong impact on the forward-mode TID response of SiGe HBTs.

Modeling Single-Event Transient Propagation in a SiGe BiCMOS Direct-Conversion Receiver

The propagation of single-event transient (SET) signals in a silicon-germanium (SiGe) direct-conversion receiver is studied. A theoretical analysis of transient propagation, verified by simulation, is presented. A new method to characterize and quantify the impact of SETs in communication systems carrying modulated data is proposed. The proposed method suggests examining distortions in the signal constellation diagram to determine the effect of SETs on modulated data, and using error vector magnitude to estimate the error probability in different parts of the system.

On the Application of Inverse-Mode SiGe HBTs in RF Receivers for the Mitigation of Single-Event Transients

Best practice in mitigation strategies for single-event transients (SETs) in radio-frequency (RF) receiver modules is investigated using a variety of integrated receivers utilizing inverse-mode silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs). The receivers were designed and implemented in a 130-nm SiGe BiCMOS technology platform. In general, RF switches, low-noise amplifiers (LNAs), and downconversion mixers utilizing inverse-mode SiGe HBTs exhibit less susceptibility to SETs than conventional RF designs, in terms of transient peaks and duration, at the cost of RF performance. Under normal RF operation, the SET-hardened switch is mainly effective in peak reduction, while the LNA and the mixer exhibit reductions in transient peaks as well as transient duration.