I. Doi

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

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...

A novel Si micromachined moving-coil induction actuated mm-sized resonant scanner

A novel silicon micromachined moving-coil scanner with electromagnetic induction actuation principle is presented. It was manufactured by the Si-LIG process, silicon-lithography-electroforming (Galvanoformung, from German), where its mechanical structure was made by bulk silicon micromachining of 200 µm thick (1 0 0) silicon substrate, and its armature was patterned by deep UV lithography and Au electroplating. The monolithic mechanical structure is a 12 × 24 mm2 rectangular frame connected by 4.5 mm long torsion bars to a 4 × 10 mm2 rectangular rotor. On one face of the rotor is the armature, a 70 µm thick, single turn, electroplated Au coil with 3.3 mΩ electrical resistance. The other face of the rotor was mirrored by a 1480 A thick Al film. An external magnetic circuit generated a constant 0.115 T magnetic field parallel to the coil plane and a 0.01 T (peak value) field normal to the coil plane. A maximum mechanical deflection angle of 9.0° pp at the 1311.5 Hz resonance frequency was measured, and a quality factor, Q, of 347 was achieved in air. A mathematical model for the device was derived and a dimensioning procedure was developed. The results show that electromagnetic induction actuation is adequate for mm-sized systems and capable of producing resonant scanners with performance compatible with applications such as bar code readers.

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

Influence of Al/TiN/SiO2 structure on MOS capacitor, Schottky diode, and fin field effect transistors devices

Titanium nitride (TiN) films were tested for their suitability as upper electrodes in metal–oxide–semiconductor (MOS) capacitors and Schottky diodes and as metal gate electrodes in fin field effect transistor devices. TiOxNy formation on TiN surfaces was confirmed by x-ray photoelectron spectroscopy and appears to be associated with exposure of the metal electrodes to ambient air. In order to avoid the formation of TiOxNy and TiO2, a layer of aluminum (Al) was deposited in situ after the TiN deposition. TiN work function was calculated for the devices to study how dipole variation at the interface TiN/SiO2 influences TiN work function. TiOxNy and TiO2 formation at the film surface was found to affect the dipole variations at the TiN/SiO2 interface increasing the dipole influence on MOS structure. Furthermore, the estimated values TiN work function are suitable for complementary metal–oxide–semiconductor (CMOS) technology. Finally, this work had shown that Al/TiN structure can be used in CMOS technology, e...

Deposition of sacrificial silicon oxide layers by electron cyclotron resonance plasma

Electron cyclotron resonance plasmas with SiH4∕O2∕Ar mixtures were used for deposition of thin films of silicon oxide, to be employed as sacrificial layers in microelectromechanical system (MEMS) fabrication. The grown films were characterized by Fourier transform infrared and ellipsometry. Optical emission spectroscopy and Langmuir probe were used for plasma characterization. It has been shown that OH molecules generated in the plasma play an important role in formation of films suitable as sacrificial layers for MEMS fabrication. Extremely high etch rates of grown oxide films (up to 10μm∕min) were obtained, allowing fabrication of high quality poly-Si suspended structures.Electron cyclotron resonance plasmas with SiH4∕O2∕Ar mixtures were used for deposition of thin films of silicon oxide, to be employed as sacrificial layers in microelectromechanical system (MEMS) fabrication. The grown films were characterized by Fourier transform infrared and ellipsometry. Optical emission spectroscopy and Langmuir probe were used for plasma characterization. It has been shown that OH molecules generated in the plasma play an important role in formation of films suitable as sacrificial layers for MEMS fabrication. Extremely high etch rates of grown oxide films (up to 10μm∕min) were obtained, allowing fabrication of high quality poly-Si suspended structures.

Observation of Structural Depth Profiles in Porous Silicon by Atomic Force Microscopy

The morphology of porous silicon (PS) formed by wet etching of Si crystals in fluoride solutions was investigated by atomic force microscopy (AFM). The experiments were made in a liquid cell to allow the measurements to be made before the drying process caused restructuring of the surface porosity. We studied the surface roughness, showing experimentally that PS samples produced in high HF concentrations are smoother than PS samples produced in low HF concentrations. We also demonstrated that using the capillary forces produced by the AFM probe tip itself, it is possible to etch layers of the PS material, opening “windows” to observe the interior PS layers. We identified through Fourier transform analysis the most frequent dimensions of the pores, concluding that these pores in general do not suffer appreciable vertical narrowing and that high HF concentrations are favorable for the formation of more pores of smaller size.

Si-LiG process for inductive meso systems

A new process for microelectromechanical systems (MEMS) has been developed and employed in the microfabrication of inductive actuators. The process combines deep UV lithography and metal electroplating with bulk silicon micromachining. The lithography is based on an AZ-4260 photoresist with a thickness of 50 μm, while electroplating is accomplished by using a gold bath; the bulk silicon is micromachined in an aqueous KOH solution (28% w/w) at 80 °C. This process has been successfully applied in the micromachining of an oscillating mirror actuated by induction. The results show compatibility between the microfabrication process of the metallic structures and the KOH bulk silicon micromachining process. The photoresist mold remained intact after the electroplating step, and the electroplated structures were uniform in thickness, surface uniformly smooth, and presented good adhesion, maintaining these features also after KOH micromachining.

Micromachined scanner actuated by electromagnetic induction

A novel micromachined scanner with electromagnetic induction actuation principle is presented. It was manufactured by Si-LIG technique, where its mechanical structure was made by bulk silicon micromachining of 200μm thick (100) silicon substrate, and its electric circuit was made by deep UV lithography and Au electroplating. The monolithic mechanical structure is a 12×24 mm2 rectangular frame connected by 4.5mm long torsion bars to a 4×10mm2 rectangular rotor. On one face of the rotor is the electric circuit, a 70μm thick, single turn, electroplated Au coil with 3.3mΩ electrical resistance. The other face of the rotor was mirrored by a 1480Å thick Al film. An external magnetic circuit generated a constant 1150 Gauss magnetic field parallel to the coil plane and a 100 Gauss (peak value) field normal to the coil plane. Maximum deflection angle of 6.5°pp at the 1311Hz resonance frequency was measured, and the quality factor Q was 402. The results shown that electromagnetic induction actuation is adequate for meso-scale systems and capable of producing resonant scanners with performance compatible with applications like bar code readers.

Modification of the refractive index and the dielectric constant of silicon dioxide by means of ion implantation

The modification of silicon dioxide films by means of ion implantation of fluorine and carbon was studied. 19 F a and 12 C a ions were separately and sequentially implanted in 250 nm thick thermal SiO 2 films with energies ranging from 10 to 50 keV and fluences in the interval 5 10 15 to 5 10 16 cm ˇ2 . Metal/oxide/semiconductor (MOS) capacitors were fabricated on half side of the wafers. The implanted SiO2/Si samples were characterized by means of ellipsometry and Fourier transform infrared (FTIR) spectroscopy. The MOS capacitors were used to determine the relative dielectric constant. Our results indicate a considerable reduction of the dielectric constant and refractive index. The refractive index was reduced from 1.46 to 1.29 when only fluorine was implanted or when fluorine with a higher dose was implanted in combination with carbon. For the same conditions, a relative dielectric constant of 3.4 was obtained and a shift in the Si‐O bond stretching mode from 1085 to 1075 cm ˇ1 was observed by FTIR spectroscopy. ” 2000 Elsevier