J. A. Diniz

Oxynitride films formed by low energy NO+ implantation into silicon

Oxynitride (SiOxNy) insulators have been obtained by low‐energy nitric oxide ion (NO+) implantation in Si substrates prior to thermal oxidation. Characterization by Fourier transform infrared (FTIR) and secondary ion mass spectrometry (SIMS) analyses reveal the presence of Si–O, Si–N, and Si–N–O bonds in the high quality 37 nm silicon oxynitride films. The dielectric constant=5.5, effective charge density=7×1010 cm−2 and breakdown E‐fields of 3 MV/cm were determined by capacitance–voltage (C–V) and current–voltage (I–V) measurements, respectively, indicating that the SiOxNy films formed are suitable gate insulators for metal‐oxide‐semiconductor (MOS) devices.

Deposition of silicon nitride by low-pressure electron cyclotron resonance plasma enhanced chemical vapor deposition in N2/Ar/SiH4

Plasma deposition of silicon nitride on silicon substrates in a microwave electron cyclotron resonance N2/Ar/SiH4 discharge was studied as a function of gas pressure (1–5 mTorr), gas composition, and discharge power (250–1000 W). The dependencies of deposition parameters on discharge characteristics obtained at 1 mTorr appear to be essentially different from those at higher pressures. Optical emission spectroscopy was used for plasma characterization. A high degree of ionization and dissociation of gas molecules was observed under present plasma conditions. It is shown that the contribution of ionized species to film deposition is comparable with that of neutral ones under high power and low pressure conditions. The best quality of films was obtained at a moderate rather than the highest available dissociation degree of silane.

Metal gate work function tuning by Al incorporation in TiN

Titanium nitride (TiN) films have been used as gate electrode on metal-oxide-semiconductor (MOS) devices. TiN effective work function (EWF) values have been often reported as suitable for pMOS. For nMOS devices, a gate electrode with sufficient low EWF value with a similar robustness as TiN is a challenge. Thus, in this work, aluminum (Al) is incorporated into the TiN layer to reduce the EWF values, which allows the use of this electrode in nMOS devices. Titanium aluminum (TiAl), Al, and aluminum nitride (AlN) layers were introduced between the high-k (HfO2) dielectric and TiN electrode as Al diffusion sources. Pt/TiN (with Al diffusion) and Pt/TiN/TiAl/TiN structures were obtained and TiN EWF values were reduced of 0.37 eV and 1.09 eV, respectively. The study of TiN/AlN/HfO2/SiO2/Si/Al structures demonstrated that AlN layer can be used as an alternative film for TiN EWF tuning. A decrease of 0.26 eV and 0.45 eV on TiN EWF values were extracted from AlN/TiN stack and AlN/TiN laminate stack, respectively. AlN/TiN laminate structures have been shown to be more effective to reduce the TiN work function than just increasing the AlN thickness.

Silicon nitride deposited by ECR–CVD at room temperature for LOCOS isolation technology

For LOCOS application, silicon nitride (SiNx) insulators have been deposited by ECR–CVD at room temperature and with N2 flows of 2.5, 5, 10 and 20 sccm on pad-SiO2/Si or on Si substrates. The obtained SiNx/Si structures were used to analyze the SiNx characteristics. FTIR analyses reveal the presence of Si–N and N–H bonds. The refractive indexes between 1.88 and 2.48 and the thickness between 120 and 139 nm were determined by ellipsometry. With these thickness values, the deposition rates of 9.6– 10.1 nm/min and the BHF etch rates of 2–86 nm/min were determined. On the SiNx/pad-SiO2/Si structures, the LOCOS process was performed. Optical and SEM microscopy analyses were used to investigate the SiNx resistance to thermal oxidation, made at 1000 8C, and the bird’s beak in the obtained LOCOS structures, respectively. These analyses reveal that SiNx insulator performed with N2 flows higher than 2.5 sccm presented high quality to LOCOS isolation technology. # 2003 Elsevier Science B.V. All rights reserved. PACS: 85.40.Ls; 77.84.Bw; 85.40.Sz; 81.15.Gh

Optically Controlled Reconfigurable Antenna Array Based on E-Shaped Elements

This work presents the development of optically controlled reconfigurable antenna arrays. They are based on two patch elements with E-shaped slots, a printed probe, and a photoconductive switch made from an intrinsic silicon die. Numerical simulations and experiments have been shown to be in agreement, and both demonstrate that the frequency response of the antenna arrays can be efficiently reconfigured over two different frequency ISM bands, namely, 2.4 and 5 GHz. A measured gain of 12.5 dBi has been obtained through the use of two radiating elements printed in a low-cost substrate and a dihedral corner reflector.

Characterization and modeling of antireflective coatings of SiO2, Si3N4, and SiOxNy deposited by electron cyclotron resonance enhanced plasma chemical vapor deposition

In this work the optical transmission spectra of silicon oxide (SiO2), silicon nitrides (Si3N4), silicon-rich oxynitrides (SiOxNy), and antireflective coatings (ARCs), deposited by the electron cyclotron resonance enhanced plasma chemical vapor deposition onto a silicon substrate at room temperature, are studied. Simulations carried out with the MATHEMATICA program, from 0to1000nm thick coatings, showed maximum transmittance in the three basic colors at 620, 480, and 560nm for the SiO2, Si3N4, and SiOxNy ARCs, respectively. However, a highly significant transmittance over a broad spectral range from visible (VIS) to near the infrared region, with optical gain in the three basic colors above 20%, is observed only at thicknesses of 80, 70, and 60nm, respectively, for SiO2, Si3N4, and SiOxNy ARCs. Among the three evaluated films, the highest transmittance in the broad spectral band in the VIS range was observed for 60nm thick Si3N4 films. The Fourier transform infrared spectroscopy of these films reveal high...

Insulators obtained by electron cyclotron resonance plasmas on Si or GaAs

Silicon oxynitride (SiOxNy) and nitride (SiNx) insulators have been deposited or grown (with or without silane in the gas mixture, respectively) by electron cyclotron resonance (ECR) plasmas on Si and/or GaAs substrates at room temperature (20 jC) and low pressures (up to 10 mTorr). Chemical bonding characteristics of the SiOxNy and SiNx films were evaluated using Fourier transform infrared spectrometry (FTIR). The profile measurements determined the film thickness, the deposition (or oxidation) rate and the etch rates in buffered HF (BHF). The refractive indexes and the thicknesses were determined by ellipsometry. The effective interface charge densities were determined by capacitance–voltage (C–V) measurements. With these processes and analyses, different films were obtained and optimized. Suitable gate insulators for metal–insulator– semiconductor (MIS) devices with low interface charge densities were developed: (a) SiNx films deposited by ECR-chemical vapor deposition (ECR-PECVD) on GaAs substrates; (b) SiOxNy insulators obtained by low-energy molecular nitrogen ion ( 28 N2

Improving performance of microwave AlGaAs/GaAs HBTs using novel SiN/sub x/ passivation process

We report on the development of a silicon-nitride passivation film and its application to heterojunction bipolar transistors (HBT). The electric characterization of the semi-insulating film shows excellent passivation properties with measured charge density on the order of 5/spl times/10/sup 10/ cm/sup -2/, lowest, to our knowledge, reported for GaAs. Applied to HBT structure the passivation reduces in more than 75% the extrinsic base surface recombination current guaranteeing transistor gain even at 10 nA collector current levels.

Ambipolar acoustic transport in silicon

We have investigated the ambipolar transport of electrons and holes by electrically generated surface acoustic waves (SAWs) on silicon wafers coated with a piezoelectric ZnO film. The transport experiments were carried out by using a focused laser beam to optically excite carriers. The carriers are then captured by the moving SAW piezoelectric field and then transported towards a lateral p-i-n junction, where they are electrically detected. The piezoelectric modulation modifies the current vs. voltage characteristics of the lateral p-i-n junction. This behavior is accounted for by a simple model for the change of the junction potential by the SAW fields. We demonstrate that electrons and holes can be acoustically transported over distances approaching 100 μm, the transport efficiency being limited by the low mobility of holes in the material. These results open the way for silicon-based acousto-electric devices using ambipolar transport such as photo-detectors and solar cells.

Photometry of THz radiation using Golay cell detector

The measurement of THz radiation in the continuum presents new technical challenges concerning materials, frequency filters and detection devices. We present the first results of a radiometric system using Golay cell as a detector, for the whole > 15 THz range, and at discrete frequencies centered at 2, 10 and 30 THz. The system was designed to measure solar THz radiation. It is capable to detect small solar bursts, with a large dynamic range to be able to detect larger events.