Jenny M. Ford

TFSOI-can it meet the challenge of single chip portable wireless systems?

Tremendous progress in understanding and improving SOI material and devices has been made in recent years. The reduced junction capacitance and the minimal body-effect of SOI provides an inherent advantage for low-voltage low-power applications. Recent growth in the portable wireless communication market and the push for low cost solutions have driven the semiconductor industry into a race for the ultimate solution: a single chip radio capable of handling both the RF and baseband functions. In this paper, the applications of Thin-Film-Silicon-On-Insulator (TFSOI) to the different circuit elements of wireless communication systems are reviewed. The use of CMOS SOI devices as well as future development essential to realize the single chip radio are discussed.

AC floating-body effects in submicron fully depleted (FD) SOI nMOSFETs and the impact on analog applications

We report the impact of submicron fully depleted (FD) SOI MOSFET technology on device AC characteristics and the resultant effects on analog circuit issues. The weak DC kink and high frequency AC kink dispersion in FD SOI still degrade circuit performance in terms of distortion and low-frequency noise requirements. These issues raise concerns about FD devices for mixed-mode applications. Therefore, further device optimization such as source/drain engineering is still necessary to solve the aforementioned issues for FD SOI. On the other hand, partially depleted SOI MOSFET with body contact structures provide an alternative technology for RF/baseband analog applications.

Extrinsic base optimization for high-performance RF SiGe heterojunction bipolar transistors

A comprehensive study on the effect of extrinsic base optimization on the RF performance of an advanced SiGe HBT is presented. An optimized extrinsic poly base with its interface to the epi-base passivated by boron ions is demonstrated to enhance the f/sub max/ and the current gain almost two times and to reduce the low-frequency 1/f noise ten times and noise figure (NF) 0.5 dB, achieving f/sub max/ of 45 GHz, 1/f noise corner frequency of 700 Hz at I/sub B/=1.0 /spl mu/A, NF/spl les/1.0 dB at 900 MHz. Early voltage V/sub A/ of /spl ges/200 V is achieved, while maintaining a BV/sub CEO/ of /spl ges/8.0 V.

Empirical correlation between AC kink and low-frequency noise overshoot in SOI MOSFETs

Low-frequency (LF) noise overshoot has been empirically correlated with the frequency dependence of the kink effect in floating body SOI MOSFETs. Based on the correlation between these unique ac characteristics in SOI, a new mechanism is proposed to explain the well-known kink-related noise overshoot. Also, device solutions for suppressing LF noise overshoot will be discussed.

Low-frequency noise in TFSOI lateral n-p-n bipolar transistors

Low-frequency (1/f) noise is characterized as a function of base current density (J/sub B/) on thin-film-silicon-on-insulator (TFSOI) lateral bipolar transistors. In the low injection region of operation, the noise power spectral density was proportional to J/sub B//sup 1.8/ for J/sub B/ 0.4 /spl mu/m/sup 2/), the noise bias dependence shifts to J/sub B//sup 1.2/, indicating current crowding effects, alter the contribution of noise sources near the extrinsic base link region of the device. In addition to the expected 1/f noise and shot noise, we have observed a bias dependent generation-recombination (Gm) noise source in some of the devices. This G/R noise is correlated to random-telegraph-signal (RTS) noise resulting from single trapping centers, located at or near the spacer oxide and/or the Si to SIMOX interface, which modulate the emitter-base space charge region.

TFSOI technology for portable wireless communication systems

Recent growth in the portable wireless communication market has driven semiconductor technologies toward voltage and power reduction. The reduced junction capacitance and near-ideal MOS device characteristics of SOI provides an inherent advantage for low-voltage low-power applications. Substantial progress in applying SOI technology for these applications has been demonstrated in recent years. The quest for a single chip system has also initiated work in developing high frequency and analog SOI circuits. In this paper, the application of Thin-Film-Silicon-On-Insulator (TFSOI) technology for wireless communication systems is reviewed and future development discussed.

Al/Poly Si specific contact resistivity

Experimental results on the specific contact resistivity of Al/polysilicon are given for Al/1.5-percent Si contacting poly Si implanted with boron or phosphorus, annealed to surface concentrations from 3E18 to 4E20 cm-3. Specific contact resistivities of the interfaces involved were determined using an extrapolation method. Measurements were taken at room temperature, and were conducted both before and after an anneal cycle of 20 min at 450°C in forming gas. Results provide a useful parameter which enables modeling of Al/poly Si contacts.

TFSOI complementary BiCMOS technology for low power RF mixed-mode applications

A Thin-Film-Silicon-On-Insulator Complementary BiCMOS technology has been developed for low power applications. The technology is based on a manufacturable, near-fully-depleted 0.5 /spl mu/m CMOS process with the lateral bipolar device integrated as a drop-in module for CBiCMOS circuits. Excellent low power performance is demonstrated through low current ECL and low voltage CMOS circuits. For the first time, good RF and analog performance of a TFSOI (C)BiCMOS technology is demonstrated. Device gain, noise figure, 1/F noise and matching characteristics comparable to bulk BiCMOS technologies are achieved.

Al/Si contact resistance for submicrometer design rules

The resistance of contacts between aluminum/1.5-percent silicon and doped silicon is experimentally determined as a function of contact sizes from 0.6 to 4 µm square. Silicon contacted was doped to varied concentrations with either boron or phosphorus. The magnitudes of resistances observed for submicrometer geometry contacts underscore the need for a lower resistance-contact process for high-performance VLSI.

Power amplifiers on thin-film-silicon-on-insulator (TFSOI) technology

Portable wireless communication applications have provided a relentless driving force for semiconductor manufacturers to deliver high performance circuits operating with drastically reduced supply voltage and power. To ultimately enable a single chip solution, process technology for these circuits must support all functions within the radio, from digital microcontrollers to RF downconversion. The literature reflects previous work that soundly demonstrates the advantages of thin-film-silicon-on-insulator (TFSOI) in low power digital baseband circuits such as microcontroller CPUs, SRAM, DRAM and ALUs (Huang et al. 1997). More recently, results of receiver functions such as low noise amplifiers, mixers, and VCOs implemented in TFSOI have been reported (Harada et al. 1997; Dekker et al. 1997; Tseng et al. 1998). Lack of a successful demonstration of a power amplifier has been one element preventing implementation of a complete TFSOI RF transceiver. This paper reports the results of the first demonstration of power amplifiers on TFSOI, using n-channel RF MOSFET devices.