Jae Sung Rieh

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 T/) of 207 GHz and an f/sub MAX/ extrapolated from Masons unilateral gain of 285 GHz. f/sub MAX/ extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12/spl times/2.5 /spl mu/m/sup 2/ have these characteristics at a linear current of 1.0 mA//spl mu/m (8.3 mA//spl mu/m/sup 2/). Smaller transistors (0.12/spl times/0.5 /spl mu/m/sup 2/) have an f/sub T/ of 180 GHz at 800 /spl mu/A 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 T/ at small lateral dimensions.

SiGe HBTs with cut-off frequency of 350 GHz

This work reports on SiGe HBTs with f/sub T/ of 350 GHz. This is the highest reported f/sub T/ for any Si-based transistor as well as any bipolar transistor. Associated f/sub max/ is 170 GHz, and BV/sub CEO/ and BV/sub CBO/ are measured to be 1.4 V and 5.0 V, respectively. Also achieved was the simultaneous optimization of f/sub T/ and f/sub max/ resulting in 270 GHz and 260 GHz, with BV/sub CEO/ and BV/sub CBO/ of 1.6 V and 5.5 V, respectively. The dependence of device performance on bias condition and device dimension has been investigated. Considerations regarding the extraction of such high f/sub T/ and f/sub max/ values are also discussed.

Reduction of dislocation density in mismatched SiGe/Si using a low-temperature Si buffer layer

The reduction of the dislocation density in relaxed SiGe/Si heterostructures using a low-temperature Si(LT-Si) buffer has been investigated. We have shown that a 0.1 μm LT-Si buffer reduces the threading dislocation density in mismatched Si0.85Ge0.15/Si epitaxial layers as low as ∼104 cm−2. Samples were grown by both gas-source molecular beam epitaxy and ultrahigh vacuum chemical vapor deposition.

SiGe HBT technology with f/sub max//f/sub T/=350/300 GHz and gate delay below 3.3 ps

This work reports on SiGe HBT technology with f/sub max/ and f/sub T/ of 350 GHz and 300 GHz, respectively, and a gate delay below 3.3 ps. This is the highest reported speed for any Si-based transistor in terms of combined performance of f/sub max/ and f/sub T/ both of which exhibit 300 GHz and above. Associated BV/sub CEO/ and BV/sub CBO/ are measured to be 1.7 V and 5.6 V, respectively. The dependence of device performance on bias condition and device dimension has been investigated. Considerations regarding the extraction of such high f/sub max/ and f/sub T/ values are also discussed.

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).

A 210-GHz f/sub T/ SiGe HBT with a non-self-aligned structure

A record 210-GHz f/sub T/ SiGe heterojunction bipolar transistor at a collector current density of 6-9 mA//spl mu/m/sup 2/ is fabricated with a new nonself-aligned (NSA) structure based on 0.18 /spl mu/m 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/sub 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.

Foundation of rf CMOS and SiGe BiCMOS technologies

This paper provides a detailed description of the IBM SiGe BiCMOS and rf CMOS technologies. The technologies provide high-performance SiGe heterojunction bipolar transistors (HBTs) combined with advanced CMOS technology and a variety of passive devices critical for realizing an integrated mixed-signal system-on-a-chip (SoC). The paper reviews the process development and integration methodology, presents the device characteristics, and shows how the development and device selection were geared toward usage in mixed-signal IC development.

40 Gbit/sec circuits built from a 120 GHz f/sub T/ SiGe technology

Product designs for 40 Gbit/sec applications fabricated from SiGe BiCMOS technologies are now becoming available. This paper will briefly discuss technology aspects relating to HBT device operation at high speed, acting to dispel some common misconceptions regarding SiGe HBT technology applicability to 40 Gbit/sec circuits. The high speed portions of the 40 Gbit/sec system are then addressed individually, demonstrating substantial results toward product offerings, on each of the critical high speed elements.

SiGe heterojunction bipolar transistors and circuits toward terahertz communication applications

The relatively less exploited terahertz band possesses great potential for a variety of important applications, including communication applications that would benefit from the enormous bandwidth within the terahertz spectrum. This paper overviews an approach toward terahertz applications based on SiGe heterojunction bipolar transistor (HBT) technology, focusing on broad-band communication applications. The design, characteristics, and reliability of SiGe HBTs exhibiting record f/sub T/ of 375 GHz and associated f/sub max/ of 210 GHz are presented. The impact of device optimization on noise characteristics is described for both low-frequency and broad-band noise. Circuit implementations of SiGe technologies are demonstrated with selected circuit blocks for broad-band communication systems, including a 3.9-ps emitter coupled logic ring oscillator, a 100-GHz frequency divider, 40-GHz voltage-controlled oscillator, and a 70-Gb/s 4:1 multiplexer. With no visible limitation for further enhancement of device speed at hand, the march toward terahertz band with Si-based technology will continue for the foreseeable future.

Measurement and modeling of thermal resistance of high speed SiGe heterojunction bipolar transistors

Thermal resistance has been measured for high speed SiGe HBTs with various emitter widths and lengths. The smaller devices exhibited higher thermal resistance values, but eventually resulted in lower junction temperature rise for a given power density. A physical model has been developed which showed good agreement with the measurements. The model indicates that the thermal resistance depends strongly on the deep trench geometry. The thermal resistance is also anticipated to increase with the existence of adjacent devices due to a heat dissipation interference, according to the model.