D. Vanhoenacker

Comparison of TiSi2 , CoSi2, and NiSi for Thin‐Film Silicon‐on‐Insulator Applications

TiSi2, CoSi2, and NiSi self-aligned silicide processes have been studied, compared, and applied to thin-film silicon-on-insulator technology. Compared to TiSi2, CoSi2 and NiSi have the advantages of wider process temperature window, no significant doping retarded reaction, narrow runner degradation, and thin-film degradation. Therefore, they are more suitable for thin-film silicon-on-insulator technology. N-type field effect transistors have been fabricated in a complementary metal oxide-semiconductor compatible thin-film silicon-on-insulator technology with titanium, cobalt, and nickel self-aligned silicide processes for low-voltage, low-power microwave applications. The initial thicknesses of titanium, cobalt, and nickel are 30, 13, and 25 nm, respectively. The gate sheet resistances are 6.2, 4.4, and 2.9 Omega/square, respectively, and the total source/drain series resistances are 700, 290, and 550 Omega mu m, respectively. High-frequency measurement results are also presented.

Extended study of crosstalk in SOI-SIMOX substrates

This work analyzes crosstalk phenomena in SOI-SIMOX substrates by means of two-dimensional device simulations and measurements on test structures. The influence of the substrate resistivity and of guard rings is studied. The results are compared with those obtained for standard CMOS technology. A significant crosstalk reduction, up to 10 GHz, is obtained with high-resistivity substrates. A simple modeling is proposed to explain and simulate the phenomenon.

A low-voltage, low-power microwave SOI MOSFET

Summary form only given. Recently, it has been demonstrated that the use of high-resistivity SOI (SIMOX) substrates (5,000 and 10,000 /spl Omega/.cm) yields MOSFETs which offer interesting microwave performances. Indeed unity-gain frequencies (f/sub T/) of 14 and 23.6 GHz and maximum oscillation frequencies (f/sub max/) of 21 and 32 GHz have been reported for effective gate lengths of 0.36 and 0.25 /spl mu/m, respectively, and using supply voltages ranging from 3 to 5 volts. Such devices can be integrated with planar lines to implement MMIC circuits. These transistors were fabricated using a dedicated MOS process, called MICROX/sup TM/, which uses non-standard CMOS features, such as a metal (gold) gate and air-bridge metallisation. In this work, the high-frequency performances of microwave transistors fabricated using a standard fully-depleted SOI CMOS process are described. These devices are, therefore, compatible with analog and digital circuits fabricated using the same low-cost process.

A novel nanostructured microstrip device for tunable stopband filtering applications at microwaves

The authors present a novel microstrip structure using a nanoscale porous substrate filled by a ferromagnetic material, forming an array of nanowires perpendicular to the ground plane. When compared with photonic bandgap structures, the stopband behavior is created here by a gyromagnetic resonance phenomenon in the metallic nanowires. This resonance is tuned by means of a DC magnetic field parallel to the nanowires, in a very good agreement with the gyromagnetic theory. Also, tuning can be achieved over more than one octave, because the nanoscale geometry ensures that fields penetrate into the whole wire area up to 40 GHz. Other advantages are detailed in this work.

Determining the reference impedance of on-wafer TLR calibrations on tossy substrates

This paper presents an efficient reference impedance determination method, which is applicable to TLR calibrations performed on a wide variety of substrates, including those consisting of low resistivity material. The method is shown to be valid up to 40 GHz. It is based on the comparison of DC-resistance and scattering-parameter measurements of a resistor, a short and an open.

A Multipath Model for Atmospheric Scintillations At Microwaves and Millimeter Waves

The paper describes a deterministic model for the effects of atmospheric turbulences on satellite-earth links from 1 to 100 GHz. Turbulent cells are considered as dielectric volumes crossing the Fresnels zones of the link. The transmission coefficients are calculated for point receivers as well as for actual aperture antennas. The model yields a transfer function submitted to the influence of the equivalent dielectric constant, the thickness, size, and geometry of the cells, the size of the antenna, and the operating frequency. The resulting group delay is also evaluated, as well as the impulse and step-responses.

An efficient design tool for transmission line on SIMOX substrates

Planar metallizations on surface-passivated semiconductor substrates have become a familiar form of signal transmission with the rapid development of the monolithic integrated circuit technology now extending into the microwave frequency region. However, little is known at present concerning the transmission properties of such a composite structure. In this paper we present the behaviour of the SOI substrate as function of frequency. A new model of transmission line is developed and compared with measurements of CPW lines realized on various SIMOX substrates.

A New and Simple Calibration Method for Measuring Planar Lines Parameters up to 40 GHz

This paper presents a new method for extracting the wavelength and losses of dispersive lossy planar lines from measurements made up to 40 GHz. It requires only two lines, differing by their length, while the LRL method necessites four elements. This new method has been successfully tested on microstrips, slotlines and coplanar waveguides. The results confirm the validity of the method and the accuracy of the models developed by the authors for those lines. From the results, a method has been designed to measure the dielectric constant of the substrates, with a very good accuracy up to 40 GHz.

Accurate Characterization of Silicon-On-Insulator MOSFETs for the Design of Low-Voltage, Low-Power RF Integrated Circuits

The maturation of low cost Silicon-on-Insulator (SOI) MOSFET technology in the microwave domain has brought about a need to develop specific characterization techniques. An original scheme is presented, which, by combining careful design of probing and calibration structures, rigorous in-situ calibration, and a new powerful direct extraction method, allows reliable identification of the parameters of the non-quasi-static small-signal model and the high-frequency noise parameters for MOSFETs. The extracted model is shown to be valid up to 40 GHz.

Modelling and optimising the SOI MOSFET in view of MMIC applications

A small-signal model based on technological parameters is validated by measurements for thin-film fully-depleted silicon-on-insulator nMOSFETs. The model is used to evaluate the impact of technological improvements and to guide the performance optimisation of the device. It is shown that the SOI nMOSFET can be expected to perform suffciently well so as to be eligible for MMIC applications up to 10 GHz.