Reliability of microwave SiGe/Si heterojunction bipolar transistors

The degradation behavior of NPN Si/SiGe/Si heterojunction bipolar transistors, grown by solid-source molecular beam epitaxy (MBE), has been studied by accelerated lifetime testing at different ambient temperatures. The degradations of the dc current gain and the microwave performance of the devices are explained in terms of recombination enhanced impurity diffusion (REID) of boron atoms from the base region and the subsequent formation of parasitic energy barriers at the base-emitter and base-collector junctions     

A 47 GHz Cross-Coupled VCO Employing High- Island-Gate Varactor for Phase Noise Reduction

A 47 GHz $LC$ cross-coupled voltage controlled oscillator (VCO) employing the high-$Q$ island-gate varactor (IGV) based on a 0.13 $mu{rm m}$ RFCMOS technology is reported in this work. To verify the improvement in the phase noise, two otherwise identical VCOs, each with an IGV and a conventional multi-finger varactor, were fabricated and the phase noise performance was compared. With $V_{DD}$ of 1.2 V and core power consumption of 3.86 mW, the VCOs with the IGV and the multi-finger varactor have a phase noise of $-$95.4 dBc/Hz and $-$91.4 dBc/Hz respectively, at 1 MHz offset, verifying the phase noise reduction with the introduction of the high-$Q$ IGV. The VCO with IGV exhibited an output power of around $-$15 dBm, leading to a FoM of $-$182.9 dBc/Hz and a tuning range of 3.35% (45.69 to 47.22 GHz).      

Balanced RF Duplexer with Low Interference Using Hybrid BAW Resonators for LTE Application

A balanced RF duplexer with low interference in an extremely narrow bandgap is proposed. The Long‐Term Evolution band‐7 duplexer should be designed to prevent the co‐existence problem with the WiFi band, whose fractional bandgap corresponds to only 0.7%. By implementing a hybrid bulk acoustic wave (BAW) structure, the temperature coefficient of frequency (TCF) value of the duplexer is successfully reduced and the suppressed interference for the narrow bandgap is performed. To achieve an RF duplexer with balanced Rx output topology, we also propose a novel balanced BAW Rx topology and RF circuit block. The novel balanced Rx filter is designed with both lattice‐ and ladder‐type configurations to ensure excellent attenuation. The RF circuit block, which is located between the antenna and the Rx filter, is developed to simultaneously function as a balance‐to‐unbalance transformer and a phase shift network. The size of the fabricated duplexer is as small as 2.0 mm × 1.6 mm. The maximum insertion loss of the duplexer is as low as 2.4 dB in the Tx band, and the minimum attenuation in the WiFi band is as high as 36.8 dB. The TCF value is considerably lowered to ?16.9 ppm/°C.     

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_T) of 207 GHz and an f_MAX extrapolated from Mason's unilateral gain of 285 GHz. f_MAX extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12×2.5 μm² have these characteristics at a linear current of 1.0 mA/μm (8.3 mA/μm²). Smaller transistors (0.12×0.5 μm²) have an f_T of 180 GHz at 800 μA current. The devices have a pinched base sheet resistance of 2.5 kΩ/sq. and an open-base breakdown voltage BV_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_T at small lateral dimensions     

A 210-GHz fT SiGe HBT with a non-self-aligned structure

A record 210-GHz f_T SiGe heterojunction bipolar transistor at a collector current density of 6-9 mA/μm² is fabricated with a new nonself-aligned (NSA) structure based on 0.18 μm technology. This NSA structure has a low-complexity emitter and extrinsic base process which reduces overall thermal cycle and minimizes transient enhanced diffusion. A low-power performance has been achieved which requires only 1 mA collector current to reach 200-GHz f_T. The performance is a result of narrow base width and reduced parasitics in the device. Detailed comparison is made to a 120-GHz self-aligned production device     

Trench‐type deep N‐well dual guard ring for the suppression of substrate noise coupling

This article presents a study on the isolation performance of the trench‐type deep n‐well (DNW) dual guard ring (GR) and its effect on the suppression of the substrate digital noise coupling on a low noise amplifier (LNA) based on measurement and TCAD simulation. The trench‐type DNW dual GR, in which the DNW is formed beneath the ring‐shaped n‐well region only, can be adopted for protecting the noise‐sensitive analog/RF circuits or circuit blocks against the substrate noise. An in‐depth analysis on the performance of the trench‐type DNW was carried out based on both measurement and a heavy use of TCAD. The results show that the trench‐type DNW dual GR exhibits comparable isolation to that of the pocket‐type DNW dual GR at high frequency regime. The effect of various GR dimension parameters and GR bias conditions on the GR isolation performance was also investigated and analyzed. Furthermore, the trench‐type DNW dual GR was applied to a 5.8‐GHz LNA and its effect on the suppression of the substrate digital noise coupling was studied for various digital noise conditions and GR bias schemes. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Half-terahertz operation of SiGe HBTs

This letter presents the first demonstration of a silicon-germanium heterojunction bipolar transistor (SiGe HBT) capable of operation above the one-half terahertz (500 GHz) frequency. An extracted peak unity gain cutoff frequency (f/sub T/) of 510 GHz at 4.5 K was measured for a 0.12/spl times/1.0 /spl mu/m/sup 2/ SiGe HBT (352 GHz at 300 K) at a breakdown voltage BV/sub CEO/ of 1.36 V (1.47 V at 300 K), yielding an f/sub T//spl times/BV/sub CEO/ product of 693.6 GHz-V at 4.5 K (517.4 GHz-V at 300 K).     

Scaling of SiGe Heterojunction Bipolar Transistors

Scaling has been the principal driving force behind the successful technology innovations of the past half-century. This paper investigates the impacts of scaling on SiGe heterojunction bipolar transistors (HBTs), which have recently emerged as a strong contender for RF and mixed-signal applications. The impacts of scaling on key performance metrics such as speed and noise are explored, and both theory and data show that scaling, both vertical and lateral, has mostly beneficial effects on these metrics. However, it is shown that the scaled devices are increasingly vulnerable to device reliability issues due to increased electric field and operation current density. Bipolar transistor scaling rules are reviewed and compared with accumulated reported data for verification. A review of scaling limits suggests that bipolar scaling has not reached the physical fundamental limit yet, promising a continued improvement of bipolar performance in the foreseeable future.     

A 300-GHz CMOS 7-by-7 Detector Array for Optics-less THz Imaging with Scan-less Target Object

Journal of Infrared, Millimeter, and Terahertz Waves - In this work, a 300-GHz 7?×?7 detector array based on a 65-nm Si CMOS technology has been developed and transmission imaging...     

Effect of Printed Circuit Board Structures on Temperature-Dependent Gain Characteristics of RF Power Amplifier Chips

We fabricated and characterized heterojunction field effect transistor radio frequency (RF) power amplifier (PA) test fixtures, for wireless applications, with various printed circuit board (PCB) structures. The RF matching and bias circuits of the test fixtures were designed so that they had the same RF characteristics. The only source of the variation of the RF gain (S₂₁) was different thermal characteristics of each PCB. The values of the junction temperature (T_J) and the junction-to-ambient thermal resistance (R _{J A}) of each test fixture were shown to be changed as much as 80deg C and 30deg C / W, respectively, by the change of PCB structures. The change of Rja was shown to be originated from the change of the PCB thermal resistance, assuring that the structure of the PCB was the dominant factor in determining R _{J A} Finally, we obtained a universal relation between S₂₁ of the amplifier and Tj. This work suggests that thermal budget of PCB is as important as that of package in wireless RF equipments.