Device technology progresses quickly, even in the eyes of those who track semiconductor advances. For those interested in the state of the art, there may be no better place to compare standards than the annual International Electron Devices Meeting (IEDM). Scheduled for December 8-10, 2003 in the Hilton Washington and Towers hotel (Washington, DC), the 49th Annual IEDM promises a wide cross section of leading semiconductor technologies, from logic and memory to RF power transistors and millimeter-wave integrated circuits (ICs).
For example, in a session on solid-state devices, Katsuyoshi Washio of Hitachi Ltd.'s Central Research Laboratory (Tokyo, Japan) will detail improvements in silicon-germanium heterojunction-bipolar-transistors (SiGe HBTs) and BiCMOS technologies. His presentation notes that the use of self-aligned fabrication processes along with thinning of the base width have enabled device developers to reduce parasitic device capacitances and resistances to achieve maximum frequency of oscillation for SiGe HBTs in excess of 250 GHz. Washio predicts that gate delays will reach a mere 3 ps in 2005, supporting the development of logic circuitry operating at 160 GHz.
Following Washio, B. Heinemann and co-workers from IHP (Frankfurt, Germany) will report on a 200-GHz complementary BiCMOS process with isolated SiGe:C PNP HBT devices. By using a highly tuned vertical doping profile, the isolated PNP transistors can be readily integrated into the CMOS process. Fabricated devices have shown current gain of 160 at a +2 VDC for an NPN HBT, with peak maximum frequency of oscillation in the range of 110 to 120 GHz.
In the first of several sessions on displays, sensors, and microelectromechanical systems (MEMS), Paul Baude and associates from the 3M Company (St. Paul, MN) presented results for organic-semiconductor-based radio-frequency-identification (RFID) transponders. The transponders feature pentacene-based thin-film circuitry, including a ring oscillator that, when activated, generates a clock signal which is buffered and used to modulate the RF signal. Amplitude modulation (AM) of a 4.079-MHz field is detected externally with a simple diode-based peak detector. The researchers accomplishment is the first reported demonstration of organic semiconductor technology without external rectification.
Following Baude's presentation, a fascinating student session by Josephine Lee and Vivek Subramanian from the Department of Electrical Engineering and Computer Sciences at the University of California at Berkeley explored the use of organic transistors fabricated on fabric, opening the way for the first electronic textile materials. The process employs 125-µm-diameter aluminum wire as the gate line, which can be woven directly into an electronic textile (e-textile). The fiber was encapsulated with a thin-layer gate dielectric, 60-nm pentacene channel material was evaporated, and the fiber was masked with orthogonal over-woven 50-µm-diameter wires, serving as channel masks. Then 100-nm gold was evaporated to form source/drain contacts. Upon removal of the over-woven fibers, arrays of transistors resulted, with transistors formed at every intersection of the fibers. The devices, which are similar to conventional pentacene thin-film transistors (TFTs), exhibit well-behaved electrical characteristics with gate mobility on the order of 0.05 cm2/V-s.
In the first of several sessions on quantum electronics and compound semiconductors, Sung-Yung Chung and associates from Ohio State University (Columbus, OH), the US Naval Research Laboratory (Washington, DC), the University of California at Riverside (Riverside, CA), and the Rochester Institute of Technology (Rochester, NY) reported on the first monolithic vertical integration of a Si/SiGe HBT with a Si-based resonant interband tunnel diode (RITD). The device acts as a logic latch with adjustable peak-to-valley current ratios.
In a session on RF power devices and passive components, Helmut Brech and co-workers from the RF and DSP Infrastructure Division of the Semiconductor Products Sector of Motorola (Tempe, AZ) reported on record numbers for efficiency and gain of power transistors used in wideband-code-division-multiple-access (WCDMA) communications systems at 2.1 GHz. The sixth-generation lateral DMOS (LDMOS) transistor features cutoff frequency and maximum frequency of oscillation of 8 and 18 GHz, respectively, along with small-signal gain of 25.5 dB. The gate length and oxide thickness were both reduced to improve the high-frequency response, although drain optimization did not compromise reliability with projected quiescent current drift of less than 4 percent extrapolated over 20 years. When used in the 2.1-GHz band with a two-carrier WCDMA signal, the device achieved 29-percent drain efficiency with 20 W output power and third-order intercept point of −37 dBc, while maintaining power gain at 16.5 dB. Under other test conditions, power-added efficiency (PAE) of 61 percent was achieved with output power of more than 100 W.
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Also in the RF power device session, Jonghae Kim and associates from IBM's Semiconductor Research and Development Center (Hopewell Junction, NY) and the Department of Electronics at Carleton University (Ottawa, Ontario, Canada) detailed highly manufacturable 40-to-50-GHz voltage-controlled oscillators (VCOs) fabricated in a 120-nm system-on-a-chip (SoC) technology. The tunable oscillators are designed to provide as much as 15-percent frequency tuning range in embedded RF circuits at frequencies to 50 GHz. The total power dissipation is 15 mW at +1.8 VDC and the phase noise offset 1 MHz from the carrier is −90.2 dBc/Hz.
In the RF power device session, Albert Chin and fellow researchers from the National Chiao Tung University (Hsinchu, Taiwan), the United Microelectronics Corp. (Hsinchu, Taiwan), and the Institute of Nuclear Energy Research (Taoyuan, Taiwan) detailed how it was possible to produce near-ideal passive components on silicon substrates at frequencies through 100 GHz with the help of electromagnetic (EM) computer modeling tools. Using the IE3D EM design tool from Zeland Software (Fremont, CA), the researchers succeeded in fabricating a variety of components, including coplanar-waveguide (CPW) filters at 91 GHz with maximum transmission loss of 1.6 dB.
In the first of several sessions on quantum electronics (with a focus on wide bandgap devices), Y. Ando and co-workers from the Photonic and Wireless Devices Research Laboratories of NEC Corp. (Otsu, Japan) presented their latest data on recessed-gate AlGaN/GaN heterojunction field-plate FETs with tremendous potential for high-power amplification. At 2 GHz and 66 V, these recessed-gate devices demonstrated a CW saturated output power of 12 W (power density of 12 W/mm device periphery) with linear gain of 21.2 dB and PAE of 48.8 percent.
R. Quay and associates from the Fraunhofer Institute of Applied Solid-State Physics (Freiburg, Germany) detailed AlGaN high-electron-mobility transistors (HEMTs) fabricated on silicon-carbide (SiC) substrates for applications at V-band (60 GHz) frequencies. The researchers achieved +13.9 dBm output power with 4 dB gain at 60 GHz.
Finally, Walid Hafez and Milton Feng from the Department of Electrical and Computer Engineering at the University of Illinois at Urbana-Champaign (Urbana, IL) described what must be done for the fabrication of indium-phosphide (InP) HBTs with cutoff frequencies as high as 502 GHz using molecular-beam-epitaxial (MBE) wafers. For more information on the upcoming IEDM, contact Conference Manager Phyllis Mahoney, Widerkehr & Associates, 16220 S. Frederick Ave., Gaithersburg, MD 20877; (301) 527-0900 ext. 103, e-mail: [email protected].