NPN HBTs Research Articles

A unified aging compact model for hot carrier degradation under mixed-mode and reverse E-B stress in complementary SiGe HBTs

This paper presents an accurate, comprehensive and physics-based aging compact model for stress-induced degradation due to hot-carrier generation and oxide trapping in advanced complementary NPN and PNP SiGe HBTs. The analytical model equations are derived from the solution of reaction–diffusion theory and Fick’s law of diffusion combined with oxide trapping mechanism under accelerated stress conditions. The model accuracy has been validated against results from long-term aging tests performed close to the safe-operating-areas of an advanced complementary 0.25 µm BiCMOS technology. Degradation asymmetry observed between NPN and PNP devices is accurately captured by this unified aging compact model. This study highlights the challenges of predicting degradation of complementary circuits and thereby improving its functionalities by designing better-matched NPN and PNP HBTs.

Half-terahertz silicon/germanium heterojunction bipolar technologies: A TCAD based device architecture exploration

A 2D TCAD based device architecture exploration of SiGe:C NPN HBTs is presented. Two novel and one conventional self-aligned architectures are explored by process and device simulation. All these three architectures show their capability of achieving maximum oscillation frequency (fmax) of 500GHz for scaled layout rules.

The Effects of Proton and X-Ray Irradiation on the DC and AC Performance of Complementary (npn + pnp) SiGe HBTs on Thick-Film SOI

The impact of 63.3 MeV proton and 10 keV X-ray irradiation on the DC and AC performance of complementary SiGe HBTs on thick-film SOI is investigated. Proton and X-ray induced changes in the forward and inverse Gummel characteristics, the output characteristics, and avalanche multiplication are reported for both npn and pnp SiGe HBTs, at both room temperature (300 K) and at cryogenic temperatures (down to 30 K). Comparison of room temperature and cryogenic data suggests interface trap formation at two distinct physical locations in the transistors. Experimental data and calibrated TCAD simulations are used to compare the radiation response of both thick-film SOI devices and thin-film SOI SiGe HBTs.

The Effects of X-Ray and Proton Irradiation on a 200 GHz/90 GHz Complementary $(npn + pnp)$ SiGe:C HBT Technology

We investigate the effects of both X-ray and proton irradiation on a novel 200 GHz/90 GHz (npn/pnp) complementary SiGe:C HBT technology. The DC forward mode total dose tolerance of the pnp HBTs is shown to exceed that of the npn HBTs by a significant margin after being subjected to both 63-MeV proton and 10-keV X-ray sources, while the AC characteristics of both devices exhibit no degradation up to X-ray doses as high as 1.8 Mrad(SiO2). Pre- and post-irradiation results from a current feedback operational amplifier implemented in this technology and irradiated up to a dose of 1.8 Mrad(SiO2) are presented, showing no degradation in performance metrics under two low current density bias configurations.

High-performance BiCMOS technologies without epitaxially-buried subcollectors and deep trenches

A 0.25 µm SiGe:C BiCMOS technology family (SG25H) with high-speed npn and pnp transistors for different performance requirements is presented. A CMOS-friendly integration scheme is realized by using collector wells, implanted after shallow trench formation, and avoiding deep trenches and extra collector sinkers. Three process variants are offered. The key bipolar transistor of the SG25H1 process is a 200 GHz npn device. The SG25H3 process offers three different types of npn HBTs. The performance ranges from fT/fmax /BVCEo values of 110 GHz/180 GHz/2.3 V for the high-speed (HS) device to 50 GHz/140 GHz/4.5 V for the medium voltage (MV) device and 30 GHz/80 GHz/6.5 V for the high-voltage (HV) transistor. The SG25H2 process provides in addition to npn transistors similar to those of SG25H1 and H3 a very high-speed SiGe:C pnp HBT with fT/fmax/BVCEo values of 90 GHz/120 GHz/2.8 V.

The effects of radiation on 1/f noise in complementary (npn+pnp) SiGe HBTs

We present the first study of the effects of radiation on low-frequency noise in a novel complementary (npn+pnp) silicon-germanium (SiGe) HBT BiCMOS technology. In order to manipulate the physical noise sources in these complementary SiGe HBTs, 63.3 MeV protons were used to generate additional (potentially noise-sensitive) trap states. The base currents of both the npn and pnp SiGe HBTs degrade with increasing proton fluence, as expected, although in general more strongly for the npn transistors than for the pnp transistors, particularly in inverse mode. For the pnp SiGe HBTs, irradiation has almost no effect on the 1/f noise to proton fluence as high as 5.0/spl times/10/sup 13/ p/cm/sup 2/, while the npn SiGe HBTs show substantial radiation-induced excess noise. In addition, unlike for the pnp devices, which maintain an I/sub B//sup 2/ bias dependence, the 1/f noise of the post-irradiated npn SiGe HBTs change to a near-linear dependence on I/sub B/ at low base currents following radiation. That suggests a fundamental difference in the noise physics between the two types of devices.

2D-simulation and analysis of lateral SiC N-emitter SiGe P-base Schottky metal-collector (NPM) HBT on SOI

We report a novel BiCMOS compatible lateral SiC N-emitter, SiGe P-base Schottky metal-collector NPM HBT on SOI. The proposed lateral NPM HBT performance has been evaluated in detail using 2-dimensional device simulation by comparing it with the equivalent NPN HBT and homojunction silicon NPM BJT structures. Based on our simulation results, it is observed that while both the lateral NPM and NPN HBTs exhibit high current gain, high cut-off frequency compared to the homojunction NPN BJT, the lateral NPM HBT has the additional benefit of suppressed Kirk effect and excellent transient response over its counterpart lateral NPN HBT. The improved performance of the proposed NPM HBT is discussed in detail and a CMOS compatible process is suggested for its fabrication.

Self-aligned SiGe NPN transistors with 285 GHz f/sub MAX/ and 207 GHz f/sub T/ in a manufacturable technology

This paper reports on SiGe NPN HBTs with unity gain cutoff frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) of 207 GHz and an f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> extrapolated from Mason's unilateral gain of 285 GHz. f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12×2.5 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> have these characteristics at a linear current of 1.0 mA/μm (8.3 mA/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). Smaller transistors (0.12×0.5 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) have an f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of 180 GHz at 800 μA current. The devices have a pinched base sheet resistance of 2.5 k/spl Omega//sq. and an open-base breakdown voltage BV/sub CEO/ of 1.7 V. The improved performance is a result of a new self-aligned device structure that minimizes parasitic resistance and capacitance without affecting f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> at small lateral dimensions.

First demonstration of monolithic InP-based HBT amplifier with PNP active load

An InP-based integrated HBT amplifier with PNP active load was demonstrated for the first time using complementary HBT technology (CRBT). Selective molecular beam epitaxy (MBE) regrowth was employed and a merged processing technology was developed for the monolithic integration of InP-based NPN and PNP HBTs on the same chip. The availability of PNP devices allowed design of high gain amplifiers with low power supply voltage. The measured amplifier with PNP HBT active load achieved a voltage gain of 100 with a power supply (V/sub CC/) of 1.5 V. The corresponding voltage swing was 0.9 V to 0.2 V. The amplifier also demonstrated S/sub 21/ of 7.8 dB with an associated S/sub 11/ and S/sub 22/ of -9.5 dB and -8.1 dB, respectively, at 10 GHz.

VLSI-COMPATIBLE PROCESSING AND LOW-VOLTAGE OPERATION OF MULTIEMITTER Si/SiGe HETEROJUNCTION BIPOLAR TRANSISTORS

Previously we demonstrated a new class of VLSI-compatible multiemitter Si/SiGe/Si npn HBTs with enhanced logic functionality. These devices have two (or more) emitter contacts and no base contact. Given a potential difference between any two emitter contacts, one of the emitter-base junctions is forward biased and injects electrons into the base, while the other junction is reverse biased and small controlling current flows by interband tunneling. Because of emitter contact symmetry, the device possesses exclusive or functionality. Our first devices provided current gain of ~400 at room temperature, at an operating voltage of ~2 V. Here we present an improved version that operates at 1 V, as well as a multiemitter HBT fabrication sequence that is not only fully compatible with a VLSI BiCMOS process, but even saves several processing steps comapred to a standard HBT.

VLSI-Compatible Processing and Low-Voltage Operation of Multiemitter Si/SiGe Heterojunction Bipolar Transistors

Previously we demonstrated a new class of VLSI-compatible multiemitter Si/SiGe/Si npn HBTs with enhanced logic functionality. These devices have two (or more) emitter contacts and no base contact. Given a potential difference between any two emitter contacts, one of the emitter-base junctions is forward biased and injects electrons into the base, while the other junction is reverse biased and small controlling current flows by interband tunneling. Because of emitter contact symmetry, the device possesses exclusive or functionality. Our first devices provided current gain of ~400 at room temperature, at an operating voltage of ~2 V. Here we present an improved version that operates at 1 V, as well as a multiemitter HBT fabrication sequence that is not only fully compatible with a VLSI BiCMOS process, but even saves several processing steps comapred to a standard HBT.

InP-based complementary HBT amplifiers for use in communication systems

This paper addresses a method to improve the linearity characteristics of power amplifiers by developing a PNP HBT technology and combining the PNP HBTs with NPN HBTs in a push–pull amplifier. InP-based PNP HBTs were fabricated with h fe>30, BV ECO=5.6 V, and f T and f max of 11 and 31 GHz, respectively, which is the best reported for InAlAs/InGaAs PNP HBTs. Common-collector push–pull amplifiers were simulated using these HBTs, demonstrating an improvement of 14 dB in second harmonic content under Class B operation. A common-emitter push–pull amplifier fabricated with the same HBTs demonstrated the best IM3 (by ∼7 dBc) and smaller second harmonic content (by ∼9 dBc) compared with NPN HBTs. In addition, the circuit produced 1.32 dBm more output power than the NPN HBT alone at 1 dB of gain compression.

Physical compact collector-emitter breakdown model for heterojunction bipolar transistors

Collector-emitter breakdown in npn HBTs is modeled using a base-collector current equal to I h = α i I c, where I c is the collector current and α i is the integral of the electron impact ionization coefficients over the base-collector depletion depth. We fit the α integrals for collector doping concentrations N d ∼ 0.08 to 1 × 10 17 cm −3 to functions of the collector voltage. The model is suitable for SPICE and harmonic balance simulators, is temperature dependent, and allows voltages to be swept above the collector-emitter breakdown limit without catastrophic effects to the model convergence.

65/90 GHz complementary HBT technology

A monolithic complementary HBT technology with record microwave performance is reported. Pnp HBTs have achieved an fmax of 65 GHz; Npn HBTs on the same wafer achieved an fmax of 90 GHz. These fmax values are the highest reported for any complementary technology; to the authors&apos; knowledge, 65 GHz is the highest fmax ever reported for a hole-transport device.

High gain AllnAs/GaAsSb/AllnAs NpN HBTs on InP

We report the first growth and characterization of high gain double heterojunction NpN HBTs on InP with a lattice-matched GaAs5Sb5 base layer. This AllnAs/GaAsSb heterojunction has almost no discontinuity in the conduction band edge, eliminating the need to grade the emitter-to-base heterojunction to achieve optimal carrier injection. The layers were grown in a solid source MBE system, using tetramer As4 and Sb4 sources. Be is an efficient acceptor in the GaAsSb, but the mobility is about half that measured inp type GaAs on GaAs substrates. The HBTs fabricated were large area mesa isolated transistors, with a beta of 80 at a current density of 2 kA/cm2, and the gain remained high at lower current densities. The turnon voltage,V be, is only 0.45 V at a current density of 2 A/cm2.