Realization of high-speed to SHBTs using novel but simple techniques for parasitic reduction (original) (raw)
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Solid-State Electronics, 2006
A new self-aligned emitter-base metallization (SAEBM) technique with wet etch is developed for high-speed heterojunction bipolar transistors (HBTs) by reducing extrinsic base resistance. After mesa etch of the base layer using a photo-resist mask, the base and emitter metals are evaporated simultaneously to reduce the emitter-base gap (S EB ) and base gap resistance (R GAP ). The InP/InGaAs/InP double heterojunction bipolar transistor (DHBT) fabricated using the technique has a reduced R GAP , from 16.48 X to 4.62 X comparing with the DHBT fabricated by conventional self-aligned base metallization (SABM) process. Furthermore, we adopt a novel collector undercut technique using selective etching nature of InP and InGaAs to reduce collector-base capacitance (C CB ). Due to the reduced R GAP , the maximum oscillation frequency (f max ) for a 0.5 lm-emitter HBT is improved from 205 GHz to 295 GHz, while the cutoff frequency (f T ) is maintained at around 300 GHz.
High-speed small-scale InGaP/GaAs HBT technology and its application to integrated circuits
IEEE Transactions on Electron Devices, 2001
We have developed the advanced performance, smallscale InGaP/GaAs heterojunction bipolar transistors (HBTs) by using WSi/Ti base electrode and buried SiO 2 in the extrinsic collector. The base-collector capacitance BC was further reduced to improve high-frequency performance. Improving the uniformity of the buried SiO 2 , reducing the area of the base electrode, and optimizing the width of the base-contact enabled us to reduce the parasitic capacitance in the buried SiO 2 region by 50% compared to our previous devices. The cutoff frequency T of 156 GHz and the maximum oscillation frequency max of 255 GHz were obtained at a collector current C of 3.5 mA for the HBT with an emitter size E of 0.5 4.5 m 2 , and T of 114 GHz and max of 230 GHz were obtained at C of 0.9 mA for the HBT with E of 0.25 1.5 m 2 . We have also fabricated digital and analog circuits using these HBTs. A 1/8 static frequency divider operated at a maximum toggle frequency of 39.5 GHz with a power consumption per flip-flop of 190 mW. A transimpedance amplifier provides a gain of 46.5 dB with a bandwidth of 41.6 GHz at a power consumption of 150 mW. These results indicate the great potential of our HBTs for high-speed, low-power circuit applications.
Submicron InP-based HBTs for Ultra-high Frequency Amplifiers
International Journal of High Speed Electronics and Systems, 2003
Transistor bandwidths are approaching terahertz frequencies. Paramount to high speed transistor operation is submicron device scaling. High bandwidths are obtained with heterojunction bipolar transistors by thinning the base and collector layers, increasing emitter current density, decreasing emitter contact resistivity, and reducing the emitter and collector junction widths. In mesa HBTs, minimum dimensions required for the base contact impose a minimum width for the collector junction, frustrating device scaling. We have fabricated HBTs with narrow collector junctions using a substrate transfer process. HBTs with submicron collector junctions exhibit extremely high fmaxand high gains in mm-wave ICs. Transferred-substrate HBTs have obtained record 21 dB unilateral power gain at 100 GHz. Recently-fabricated devices have shown unbounded unilateral power gain from 40-110 GHz, and fmaxcannot be extrapolated from measuremente. However, these devices exhibited high power gains at 220 GHz...
Ultra high-speed 0.25-μm emitter InP-InGaAs SUBTs with f/sub max/ of 687 GHz
IEDM Technical Digest. IEEE International Electron Devices Meeting, 2004., 2004
We have developed novel but simple process techniques for high speed InP SHBTs. For parasitic reduction, the collector layer is undercut using an etch-stop layer, the base pad is isolated, and the emitter metal is widened using thick plated gold. For transit time reduction, the SHBT employs InGaAs base with graded Incomposition and InGaAlAs emitter setback with graded Alcomposition. Maximum extrapolated f max of about 687 GHz with f T of 215 GHz is achieved for 0.25 × 8 µm 2 emitter area devices at I C = 8 mA and V CE = 1.5 V. These data clearly show that the optimized conventional process can offer direct implementation of InP HBT for high-speed electronic circuit fabrication.
Ultra high-speed InP-InGaAs SHBTs with f/sub max/ of 478 GHz
IEEE Electron Device Letters, 2003
InP-based single heterojunction bipolar transistors (SHBTs) for high-speed circuit applications were developed. Typical common emitter dc current gain () and BV CEO were about 17 and 10 V, respectively. Maximum extrapolated max of 478 GHz with of 154 GHz was achieved for 0.5 10 m 2 emitter size devices at 300 kA/cm 2 collector current density and 1.5 V collector bias. This is the highest max ever reported for any nontransferred substrate HBTs, as far as the authors know. This paper highlights the optimized conventional process, and the authors have great hopes for the process that offers inherent advantages for the direct implementation to high-speed electronic circuit fabrication.
InP Bipolar Transistors:High Speed Circuits and Manufacturable Submicron Fabrication Processes
2003
Compared to SiGe,InP HBTs offer superior electron transport but inferior scaling and parasitic reduction.Figures of merit for mixed-signal ICs are developed and HBT scaling laws for improved circuit speed are introduced.Device and circuit results are summarized, including >370 GHz f W &fmax HBTs,174 GHz amplifiers,75 GHz power amplifiers,87 GHz static frequency dividers, and 8 GHz '6 ADCs.To compete with 100 nm SiGe processes,InP must be similarly scaled.Device structures and initial results are shown for two processes intended for high-yield fabrication of low-parasitic InP HBTs at ~300 nm emitter width.
High-speed AlGaAs/GaAs HBTs with reduced base-collector capacitance
Electronics Letters, 2001
We present a new layout for high-speed AlGaAs/GaAs HBTs. The layout is horseshoe shaped and is designed to simultaneously reduce base resistance (R B) and base-collector capacitance (C BC). A horseshoe shaped HBT and a conventional singlefinger HBT with the same emitter width of 2 µm were fabricated and tested. The reduction of R B and C BC using the horseshoe shaped HBT resulted in 25 % improvement of maximum oscillation frequency (f max = 130 GHz).
InP DHBT-based IC technology for high-speed data communications
2005
In this paper, we report the achieved performance of devices and integrated circuits (ICs) using a manufacturable InP DHBT-based technology. High speed MBE grown InGaAs/InP DHBTs with an effective emitter junction area of 4.8 /spl mu/m/sup 2/ exhibited peak f/sub T/ and f/sub MAX/ values of 265 and 305 GHz, respectively, at a collector current density of 3.75 mA//spl mu/m/sup
Ultra high speed InP heterojunction bipolar transistors
This thesis deals with the development of high speed InP mesa HBT's with power gain cutoff frequencies up to and above 300 GHz, with high current density and low collector discharging times. Key developments are Pd-based base ohmics yielding base contact resistances as low as 10 Ωµm 2 , base-collector grades to enable to use of InP in the collector, and an increase in the maximum current density through collector design and thermal optimization. HBT's with a linear doping gradient in the base are for the first time reported and compared to HBT's with a bandgap graded base. The effect of degenerate base doping is simulated, as well as the base transit time. Key results include a DHBT with a 215 nm thick collector and an f τ = 280 GHz, and f max =400 GHz. This represents the highest f max reported for a mesa HBT. Results also include a DHBT with a 150 nm thick collector and an f τ = 300 GHz, and f max =280 GHz. The maximum operating current density has been increased to above 10 mAµm while maintaining f τ and f max ≥ 200 GHz. A mesa DHBT process with and as much yield and simplicity as possible has been developed, while maintaining or pushing world-class performance.