摘要:

VariedSiNxfilms have been deposited by low pressure chemical vapor deposition from silaneSiH4and ammoniaNH3and the influences of the deposition parameters (temperature, total pressure andNH3/SiH4gaseous ratio) on the film deposition rate, refractive index (assessed at a 830 nm wavelength), stoichiometry and thermomechanical stress are investigated and correlated. Low stress(≈600 MPa)Si3N4films are obtained for the highest deposition temperature and the lowest total pressure but the gaseous ratio is shown to be the dominant parameter. According to theSiNxstoichiometry, silicon-rich silicon nitride and nitrogen-doped silicon (called NIDOS) depositions are obtained and compressive to tensile stresses are reported. A maximum in compressive stress is put into evidence for N/Si ratio roughly equal to 0.7 and is related to the cumulated effects of silicon nitridation and crystallization, characterizing the transition between nitrogen-doped silicon and silicon-rich silicon nitride. Finally, by considering stress, deposition rate, nonuniformity along the load and resistance to alkaline solutions, optimal (silicon-rich) silicon nitride deposition conditions are proposed for microelectromechanical applications.

ISSN:0734-2101    

DOI:10.1116/1.581302

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The influence of plasma and thermal treatments on the structure and composition of sapphire (00.1) surfaces has been studied by hemispherically recorded x-ray photoelectron spectroscopy and diffraction (XPD) to better understand the surface conditioning during the growth initiation procedure for the epitaxy of GaN. A treatment involving anO2plasma generated by electron cyclotron resonance is shown to efficiently remove surface contamination and to produce well-ordered surfaces. After a thermal treatment in vacuum the sapphire (00.1) surface becomes terminated by Al atoms. AlN films with good short-range order are obtained by a simple high temperature nitridation step in the metal organic chemical vapor deposition reactor. A novel direct crystallographic method termed CHRISDA is employed for the analysis of the XPD data. By analysis of the XPD patterns the crystal structure of sapphire is found to extend into the probed near surface region without significant perturbations. The AlN layers formed by thermal nitridation were found to crystallize in the hexagonal phase and to be terminated by nitrogen atoms.

ISSN:0734-2101    

DOI:10.1116/1.581303

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A toroidal plasma source for plasma deposition at the University of Sydney (PLADEPUS) has been developed for studies of deposition of thin films, such as titanium nitride (TiN). This article describes measurements of the plasma parameters at a low rf power input, the experimental setup of the preliminary thin film deposition and the method of titanium (Ti) atom injection into the plasma by using a small current Ti arc. The microstructure of the TiN thin films is analyzed and the results are presented.

ISSN:0734-2101    

DOI:10.1116/1.581304

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The “interphase” region between the deposited layer [e.g., plasma-enhanced chemically vapor deposited (PECVD)SiO2or SiN] and the poly(ethylene terephthalate) (PET) substrate has been investigated and compared to physical vapor deposited (PVD) (electron beam evaporated)SiO2.Composition profiles determined by time-of-flight elastic recoil detection, electron microprobe analysis, and x-ray photoelectron spectroscopy all show an extended interphase region more than 50 nm in width, while the profile of the PVDSiO2is narrower. However, since these analytical techniques are invasive and prone to artifacts, we have also examined ultrathin (about 10 and 20 nm)SiO2and SiN PECVD layers on 50 nm spin-coated PET substrates by nondestructive infrared (IR) techniques. The IR spectra confirm that the thin PECVD deposits also comprise an organosilicon phase withSi–CHxbonds. We explain these observations in terms of a fragmentation/redeposition mechanism: During the earliest stage of PECVD, interaction between the plasma and the polymer surface produces volatile organic species, which intermix with the reagent gas feed, thus giving rise to the observed organosilicon-like deposit with gradually decreasing carbon content.

ISSN:0734-2101    

DOI:10.1116/1.581305

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

To fabricate the AlGaInP/GaInP strained-multiple-quantum well laser, the reactive ion etching of GaAs, GaInP, AlGaInP, and AlInP inBCl3/Ardischarges was investigated as a function of plasma parameters such as power, pressure, gas flow rate, and reactive composition, as well as etching time. Photoluminescence and Auger electron spectroscopy measurements were used to characterize the damage and surface residues caused by reactive ion etching. We have achieved a highly selective etching of GaAs with underlying GaInP. Selective etching of GaInP with AlInP and a smooth etching surface were also achieved.

ISSN:0734-2101    

DOI:10.1116/1.581306

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The reactive ion etching of substrates used in piezoelectric devices (quartz, fused silica,LiNbO3, LiTaO3,and sapphire) has been characterized inCHF3/CF4-based plasmas. For quartz and fused silica, a regime of ion-enhanced chemical etching similar to that established by Steinbruchel [Ch. Steinbruchel, J. Electrochem. Soc.130, 648 (1983)] forCF4was indicated over the range of compositions fromCF4=1toCHF3=1.In this regime, the etch rate was dependent on the square root of the rf bias voltage(V1/2).The etch rate of both the quartz and fused silica was at a maximum in aCF4plasma and decreased continuously with an increase in the ratio ofCHF3/CF4gases in the mixture. In comparison, the etch rates ofLiNbO3, LiTaO3,and sapphire were invariant with changes in the ratio of theCHF3/CF4gases, the flow rate, and the chamber pressure. The constancy of etch rate in these substrates has been attributed to a predominance of etching by a physical process of sputtering.

ISSN:0734-2101    

DOI:10.1116/1.581307

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Thin films of Au deposited on Si[(100),ntype] wafers using a solid Au source andCF4+O2microwave plasma were studied. Solid Au heated at 200 °C in a vacuum crystal reactor was vaporized in aCF4+O2microwave (2.45 GHz power 200 W) plasma flow, and the Au film was deposited on a Si wafer heated to 270 °C in a low-pressure (10 mTorr)O2atmosphere. The density of Au in this film was about 91.7% as analyzed by x-ray photoelectron spectroscopy, and the film resistivity was 2.8 μΩ cm, which is almost the same as that of the initial bulk Au (2.4 μΩ cm). The deposition mechanism was deduced. The heated solid Au reacts withO2and(CF2)nfrom theCF4+O2microwave plasma, and then the Au is converted intoAuO(CF2)n.This Au compound carries Au atoms to the vacuum chamber. In theO2atmosphere, vaporizedAuO(CF2)nis oxidized and changed into oxides such as AuO andCOFx.AuO is deposited on the Si wafer heated to 270 °C, and then reduced into Au andO2by heating. This process results in a high purity deposited gold film.

ISSN:0734-2101    

DOI:10.1116/1.581308

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The etching of silicon nitride(Si3N4)and silicon dioxide(SiO2)in the afterglow ofNF3andNF3/O2microwave discharges has been characterized. The etch rates of both materials increase approximately linearly with the flow ofNF3due to the increased availability of F atoms. The etch rate ofSi3N4is enhanced significantly uponO2injection into theNF3discharge forO2/NF3ratios of 0.3 and higher, whereas theSiO2etch rate is less influenced for the same flow ratios. X-ray photoelectron spectroscopy of processedSi3N4samples shows that the fluorine content of the reactive layer, which forms on theSi3N4surface during etching, decreases with the flow ofO2,and instead oxidation and nitrogen depletion of the surface occur. The oxidation of the reactive layer follows the same dependence on the flow ofO2as the etch rate. Argon actinometry and quadrupole mass spectrometry are used to identify reactive species in the etching of both materials. The atomic fluorine density decreases due to dilution asO2is added to the discharge. The mass spectrometer did not detectNFxspecies(x=1–3)at any discharge parameter setting, which indicates the near complete dissociation ofNF3.Nitric oxide (NO) was detected by mass spectrometry, and the NO density shows the same dependence onO2flow as theSi3N4etch rate and the surface oxidation. Based on this observation, we propose that the etch rate enhancement forSi3N4is due to the adsorption of the NO on theSi3N4surface, followed by the formation ofN2with a N atom from the surface. The O atom can then attach to the same surface site, contributing to the oxidation.

ISSN:0734-2101    

DOI:10.1116/1.581309

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A helicon plasma etch reactor is simulated using direct simulation Monte Carlo and particle-in-cell methods for a chlorine(Cl2)feed gas flow. Computations for the gas discharge are carried out by modeling the ions and neutrals as particles and by imposing the electrons as a background condition conforming to experimental measurements. The neutrals and ions are then allowed to interact with the background electrons and to relax to a steady state. The effects on the reactor flow field and etch rate of chlorine atom recombination into chlorine molecules at the walls is investigated. Results show that recombination at the walls results in the depletion of the amount of chlorine atoms (Cl) in the reactor. The depleted chlorine atom population leads to lower ionization levels and a diminished ion(Cl+)flux to the wafer. Consequently, the etch rate is decreased by as much as 15% when compared to simulations without recombination. The creation of chlorine(Cl2)molecules at the walls through recombination also provides a new source for negative ions(Cl−)which increases the electronegativity of the plasma. In addition, the results of the simulation are compared with ion current and optical emission spectroscopy (OES) measurements. The Cl–Ar ratio (measured by the OES technique) increases less than 20% from the centerline to the wall of the reactor. An inspection of absolute densities, however, reveals that the individual near-wall densities are as much as a factor of 2 greater than the centerline densities. The trace species, Ar, therefore, does not become distributed evenly throughout the reactor.

ISSN:0734-2101    

DOI:10.1116/1.581310

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Spatially resolved velocity distribution functions of metastable chlorine ions are measured in ultrahigh-frequency (UHF) plasma and compared with those in electron cyclotron resonance (ECR) plasma and inductively coupled plasma (ICP). In UHF plasma, ion velocity distribution function (IVDF) perpendicular to the surface normal of a wafer exhibits approximately no acceleration of ions to the side wall of a plasma reactor as the measuring point becomes radially far from the center of the reactor, even at 14 cm from the center where IVDF’s are shifted evidently in ECR plasma and ICP. This indicates that an almost flat profile of plasma potential is realized along the radius of the reactor in UHF plasma. As a consequence, metastable chlorine ion temperature remains low and almost constant over a radius of 14 cm in UHF plasma. Relative density of metastable chlorine ions in UHF plasma increases toward the side wall of the reactor. In contrast to this, the density exhibits a maximum in the center of the reactor and decreases towards the side wall in ECR plasma and ICP. The increased densities near the side wall in UHF plasma imply increased plasma production off the symmetry axis of the reactor, which makes UHF plasma uniform in a wider region than in ECR plasma and ICP. The effect of the discharge frequency on radial distribution of metastable chlorine ion density is also discussed.

ISSN:0734-2101    

DOI:10.1116/1.581311

出版商:American Vacuum Society    

年代:1998

数据来源: AIP