Charles E. Weitzel

Device and technology evolution for Si-based RF integrated circuits

The relationships between device feature size and device performance figures of merit (FoMs) are more complex for radio frequency (RF) applications than for digital applications. Using the devices in the key circuit blocks for typical RF transceivers, we review and give trends for the FoMs that characterize active and passive RF devices. These FoMs include transit frequency at unity current gain f/sub T/, maximum frequency of oscillation f/sub MAX/ at unit power gain, noise, breakdown voltage, capacitor density, varactor and inductor quality, and the like. We use the specifications for wireless communications systems to show how different Si-based devices may achieve acceptable FoMs. We focus on Si complementary metal-oxide-semiconductor (CMOS), Si Bipolar CMOS, and Si bipolar devices, including SiGe heterojunction bipolar transistors, RF devices, and integrated circuits (ICs). We analyze trends in the FoMs for Si-based RF devices and ICs and show how these trends relate to the technology nodes of the 2003 International Technology Roadmap for Semiconductors. We also compare FoMs for the best reported performance of research devices and for the performance of devices manufactured in high volumes, typically more than 10 000 devices. Certain commercial equipment, instruments, or materials are identified in this article to specify adequately the experimental or theoretical procedures. Such identification does not imply recommendation by any of the host institutions of the authors, nor does it imply that the equipment or materials are necessarily the best available for the intended purpose.

RF, Analog and Mixed Signal Technologies for Communication ICs - An ITRS Perspective

The International Technology Roadmap for Semiconductor (ITRS) Radio Frequency and Analog/Mixed-Signal (RF and AMS) Wireless Technology Working Group (TWG) addresses device technologies for wireless communications covering both silicon and III-V compound semiconductors. This paper discussed the roadmap and the figures of merit (FoM) used to characterize both active and passive devices critical for typical radio front end designs. The trends, challenges and potential solutions was reviewed and address the intersection of silicon and III-V compound semiconductors

The effects of oxidation and hydrogen annealing on the silicon-sapphire-interface region of SOS

Aluminum-sapphire-silicon capacitor structures were fabricated from n-SOS and p-SOS epitaxially deposited layers. The modified MIS capacitance method was used to characterize the Si-sapphire interface region electrically and to monitor changes due to exposure of the SOS to 1) oxidation at 900°C in HCl-steam and 2) annealing at 500°C in H2. Our results show that these processes can cause large easily observed changes: 1) oxidation tends to introduce negative charge at the interface and 2) subsequent annealing tends to remove it. Further, 1) oxidation tends to decrease the effective doping in the n-Si and increase the effective doping in the p-Si adjacent to the sapphire while, 2) subsequent annealing has the opposite effect.

Reduction of Low-Temperature Nonlinearities in Pseudomorphic AlGaAs/InGaAs HEMTs Due to Si-Related DX Centers

The linearity of conventional pseudomorphic AlGaAs/InGaAs/AlGaAs high-electron mobility transistors with planar doping in the AlGaAs layers is shown to degrade at low temperatures down to -40°C, as measured by the adjacent-channel power ratio under wideband code-division multiple-access modulation. A modified structure, in which the planar Si doping layers are placed within thin single GaAs quantum wells inside the AlGaAs barrier layers, eliminates this degradation. Deep-level transient spectroscopy and persistent photocapacitance measurements show that trapping on DX centers is effectively eliminated. The linearity improvements are therefore attributed to the elimination of this trapping. Self-consistent solutions of the Schro¿dinger and Poisson equations show that the transfer of the donor electrons into the channel is essentially the same in the modified and conventional structures.

Future Perspective of RF and Analog/Mixed-Signal Integrated Circuit Technologies for Mobile Communications

Radio frequency (RF) and analog/mixed-signal (AMS) integrated circuits (ICs) are key enabling components for mobile and wireless communications and their advancements continue to drive the growth of the related semiconductor market. The circuit and technology requirements for RF and AMS ICs in mobile and wireless communications are quite different in comparison to that for digital logic and memory applications. Many tradeoffs and unique considerations have to be applied for RF and analog/mixed-signal technology development and circuit implementations. This paper reviews the critical circuit and technology requirements for RF and analog/mixed-signal ICs for mobile and wireless communications and highlights future challenges and opportunities

High power density InGaP PHEMTs for 26 V operation

This paper presents a high power density and high efficiency InGaP barrier PHEMT technology for 26 V operation. This device was evaluated for 3G infrastructure applications at 2.14 GHz and WiMAX applications at 3.5 GHz. At 2.14 GHz, under a two carrier WCDMA signal, a 32.4 mm packaged device delivered 10 W average power with 11.4 dB gain and 31.4% drain efficiency at -37 dBc IM3. At 3.5 GHz, under CW stimulus, a 14.4 mm device generated an output power of 22 W with associated drain efficiency of 56% and gain of 10.2 dB.