Resonance Plasma-enhanced Chemical Vapor Deposition Research Articles

Effect of ions and radicals on formation of silicon nitride gate dielectric films using plasma chemical vapor deposition

We have clarified effects of ions and radicals on the film property of ultrathin silicon nitride (SiNx) films of 5 nm in thickness formed on Si substrates at 300 °C in electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) employing ammonia and silane (NH3/SiH4), and nitrogen and silane (N2/SiH4) gases. In situ Fourier transform infrared reflection absorption spectroscopy and in situ x-ray photoelectron spectroscopy confirmed that in N2/SiH4 plasma, Si-N bonds in the film were increased by eliminating charged species, and thus, radicals promoted the formation of the SiNx film of high Si-N bond density. On the other hand, Si-N bonds in the film were decreased by eliminating charged species, and eventually, ions played an important role in forming the film of high Si-N bond density in NH3/SiH4 plasma. The excellent hysteresis of 0.04 V was successfully achieved with the NH3/SiH4 plasma. Furthermore, the quadrupole mass spectroscopy suggests that NH4+ charged species make a significant contribution to the formation of ultrathin SiNx films with high quality. These results provide insights into important species to be controlled in the PECVD for low temperature formation of the SiNx gate dielectric films in ultralarge scale integrated circuits.

Preparation and etching processing of planar thin film of Pr3+-doped fluorozirconate glass

Planar thin-films of a 60ZrF4 · 35BaF2 · 5PrF3 composition were successfully prepared from Zr(hfa)4, Ba(hfa)2(tg), Pr(fod)3 and NF3 by an electron cyclotron resonance plasma-enhanced chemical vapor deposition technique. The films obtained were colorless and amorphous. As etching processing of the prepared thin-film, dry etching was performed using Ar, CF4, SF6, Cl2 and Cl2-BCl3 gases. The Ar etching in which no reactive ion-etching is anticipated exhibited the fastest etching rate. Wet etching was also performed using a ZrOCl2-HCl etching solution. The etching rate was extremely fast compared with those of dry etching. In this etching, however, undesirable side-etching occurred. At the present stage, therefore, the most preferable etching processing is dry etching by an Ar gas.

Experimental Study on the Role of Hydrogen in the Breakdown of Low-Temperature Si Epitaxy

AbstractHomoepitaxial Si layers were grown on Si(100) at temperatures of 325 - 500 °C by Electron-Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposition (ECR PECVD) from a gas mixture of SiH4,H2 and Ar. Ar was added in order to realize high growth rates where the breakdown of epitaxy was well observed. Si disorder depth profiles derived from RBS channeling spectra were compared with hydrogen depth distributions measured by Heavy-Ion Elastic Recoil Detection Analysis (HI-ERDA) and Secondary Ion Mass Spectroscopy (SIMS). The results suggest that the transition from epitaxial to amorphous growth proceeds through two stages: (1) a highly defective but still ordered growth with the defect density increasing as the growth proceeds and (2) the formation of conically shaped precipitates of amorphous Si. Both regions act as an increasingly effective sink for excessive hydrogen which diffuses from the growth surface into the bulk of the sample. In perfectly grown epitaxial films, where the overall concentration of excessive hydrogen was low, the hydrogen diffusion tail was found to extend far beyond the interface into the Si substrate.

The origin of intrinsic stress and its relaxation for SiOF thin films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition

SiOF films were deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) on Si(100) substrates as a function of both the SiF 4/O 2 flow ratio, as well as the Ar flow rate. The formation of SiO and SiF bonds was then confirmed using Fourier transform infrared spectroscopy (FTIR), and the residual stress in the SiOF thin films was also measured. While the SiOF thin films deposited in a SiF 4/O 2 ECR plasma were in tensile intrinsic stress, the films deposited in a SiF 4/O 2/Ar ECR plasma had compressive intrinsic stress. This transition between tensile and compressive stress was interpreted to result from Ar ion bombardment of the growing film. In the cases where films had compressive intrinsic stress, the magnitude of the compressive stress decreased with increasing SiF 4/O 2 ratio. The relaxation of the compressive stress for a given Ar flow rate is related to an F − ion related open structure.

Visible photoluminescence and electroluminescence in wide-bandgap hydrogenated amorphous silicon

Abstract The work describes basic photoluminescence (PL) and electroluminescence (EL) properties of wide-bandgap (2.0 eV or greater) hydrogenated amorphous silicon (a-Si: H). Thin films of wide-bandgap (high-hydrogen-content) a-Si: H were prepared by microwave electron cyclotron resonance plasma-enhanced chemical vapour deposition from SiH4 under high dilution with He. The films exhibit spectrally broad (full width at half-maximum, 0.4 eV or greater) visible PL at room temperature, peaked at about 1.5eV. On the basis of measurements of the PL temperature dependence, PL dynamics, infrared absorption spectra, picosecond pump-and-probe experiments and hydrogen thermal desorption spectroscopy the dominant microscopic mechanism of visible PL has been revealed to be the radiative de-excitation of oligosilane (-(SiH2)2-) units or of a specific defect in their close vicinity. EL has been investigated in sandwich p+[sbnd]i[sbnd]n+ and p+[sbnd]p[sbnd]n[sbnd]n+ structures with (Cr[sbnd]Ni)/indium tin oxide contacts....

00/02894 Preparation and characterization of ZrF 4-BaF 2-EuF 3 planar glass films by electron cyclotron resonance plasma-enhanced chemical vapor deposition

00/02894 Preparation and characterization of ZrF 4-BaF 2-EuF 3 planar glass films by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Low-Temperature Preparation of SrBi2Ta2O9 Thin Films by Electron Cyclotron Resonance Plasma-Enhanced Metalorganic Chemical Vapor Deposition and Their Electrical Properties

A SrBi2Ta2O9 (SBT) thin film was prepared by electron cyclotron resonance plasma-enhanced metalorganic chemical vapor deposition (ECR-MOCVD). The deposition temperature dependence of the composition of the film was lesser than that of films prepared by conventional thermal MOCVD. An almost single phase of SBT was obtained at 610°C. The crystallinity of this film was higher than that of the film prepared by thermal MOCVD at 500°C and subsequent heat treatment at 800°C. The leakage current density of this film was small, on the order of 10-8 A/cm2 up to 240 kV/cm. Moreover, two fold the remanent polarization and the coercive field at an applied electric field of 400 kV/cm were 14.5 µC/cm2 and 77 kV/cm, respectively. These values were larger than those of the film prepared by thermal MOCVD at 500°C with heat treatment at 800°C.

Epitaxial growth of AlN films on Si substrates by ECR plasma assisted MOCVD under controlled plasma conditions in afterglow region

Wurtzite-type aluminum nitride (h-AlN) films were epitaxially grown on off-axis Si (111) substrates by electron–cyclotron–resonance plasma-enhanced metalorganic chemical vapor deposition (ECRMOCVD) using trimethylalminum (TMA) and ammonia (NH 3) as source gases. Plasma space potential in the growth chamber was lowered by setting the magnetic field distribution as a mirror field. For the growth of h-AlN with excellent crystallinity on Si substrates, nitridation of the substrate surface, growth of a low-temperature (LT) buffer layer, and epitaxial growth of AlN films were performed under a mirror field condition in a growth chamber. Thermal nitridation at 1050°C prior to the epitaxial growth appreciably improved the crystallinity of AlN films. The growth of buffer layer at temperatures below 650°C was not so effective for the improvement of the crystallinity and crystal orientation of AlN epitaxial layer. The proportion of domain including stacking faults and that whose c-axis was parallel to the substrate surface was very small ( I (0002)/( I (10–10)+ I (10–11))>700), irrespective of the gas feed ratio of N source to Al source (NH 3/TMA) during the epitaxial growth process. Under a small gas feed ratio (NH 3/TMA<200), however, the diffraction peak intensities from the non-epitaxial domains became large.

Light emitting wide band gap a-Si:H deposited by microwave electron cyclotron resonance plasma-enhanced chemical vapour deposition

We investigate hydrogenated amorphous silicon (a-Si:H) from the point of view of light emitting applications. Thin films of wide band gap a-Si:H were prepared from silane SiH 4 diluted with He by using the microwave electron cyclotron resonance plasma enhanced chemical vapour deposition. Room temperature photoluminescence (PL) and mainly electroluminescence (EL) of p +–i–n + (p +–p–n–n +) structures were studied. The PL and EL emission spectra are in the red/near-infrared region. EL, occuring in fact in recrystallised parts of the devices (the crystallisation arising as a result of the application of an external bias), has hysteresis and the EL devices evoke the a-Si:H memory switches.

Deposition characteristics of low dielectric constant siof films prepared by ECR PECVD

SiOF film has attracted significant attention as a new interlayer dielectric material since it exhibits a lower dielectric constant than SiO2. In this study, we prepared SiOF films by using the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method and observed the dependence of the film properties on such various deposition parameters as the SiF4/O2 flow rate ratio, substrate temperature, microwave power and pressure. The increase in the film’s fluorine content led to a decrease in the dielectric constants. This was due to a decrease in ionic polarization rather than to a decrease in electronic polarization. The film properties have not exhibited a large dependence on the substrate temperature, in the range of 25~200°C. When the plasma was not activated, i. e. when the microwave power was as low as 300 W or the pressure was higher than 5 mTorr, the dielectric constants of the films were lower than 3.0 because of the high fluorine content, but the films contained silicon difluoride (Si-F2) bonds. Since Si-F2 bonds play a critical role in the absorption of water molecules which causes an increase in the dielectric constants of the films, the deposition conditions where the Si-F2 bonds are formed should be avoided.

Application of in situ ellipsometry in the fabrication of thin-film optical coatings on semiconductors

Thin-film interference filters, suitable for use on GaAs- and InP-based lasers, have been fabricated by use of the electron-cyclotron resonance plasma-enhanced chemical vapor deposition technique. Multilayer film structures composed of silicon oxynitride material have been deposited at low temperatures with an in situ rotating compensator ellipsometer for monitoring the index of refraction and thickness of the deposited layers. Individual layers with an index of refraction from 3.3 to 1.46 at 633 nm have been produced with a run-to-run reproducibility of 0.005 and a thickness control of 10 A. Several filter designs have been implemented, including high-reflection filters, one- and two-layer anitreflection filters, and narrow-band high-reflection filters. It is shown that an accurate measurement of the filter optical properties during deposition is possible and that controlled reflectance spectra can be obtained.

KrF excimer laser crystallization of silicon thin films

A KrF excimer laser operating at 249 nm has been employed to crystallize silicon thin films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) and by RF magnetron sputtering on Corning glass and SiO2. All films display a substantial improvement in crystallinity after ELC with the optimum laser fluence for as-deposited ECR films being higher than for sputtered films. This is probably related to the presence of Si−Hx bonds in the former. A pronounced bimodality in the Raman spectra of some amorphous, as-deposited ECR samples has been observed after laser crystallization where, in addition to the peak at 520cm−1, a strong peak at 509cm−1 is also present. Such behavior has not been reported previously to our knowledge in ELC silicon films. Interestingly, the XRD spectra of these samples do not exhibit any peaks suggesting the films are composed of nano-grain material. The dehydrogenation of ECR films by ELC has been demonstrated to be substantial, the hydrogen content typically decreasing from ∼30 at % in an as-deposited film to ∼10 at % after a single low fluence laser shot. Raman spectroscopy has shown that the film bonding changes from predominantly Si−H2 to Si−H after ELC. Electrical resistivity measurements of phosphorus-doped films show a controllable and repeatable change with laser fluence. The results in this paper show that it is possible to crystallize and controllably change the electrical characteristics of ECR PECVD produced silicon thin films by ELC.

Amorphous hydrogenated carbon film formation from benzene by electron cyclotron resonance chemical vapor deposition

Amorphous hydrogenated carbon thin films have been deposited from benzene vapor in an electron cyclotron resonance plasma-enhanced chemical vapor deposition reactor. The effects of gas flow rate, pressure, and microwave power on deposition rates, chemical structure and composition, and on film density were investigated. Plasma enhanced dissociation and ionization reactions were monitored by mass spectrometry and by optical emission spectroscopy. Dissociation products included a variety of unsaturated hydrocarbon species (primarily ethylene) and hydrogen. Deposited films were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, and fluorescence spectroscopy. Films displayed a condensed, aromatic, hydrocarbon-like structure, albeit without extensive conjugation. Possible reaction sequences leading to the observed film structures have been proposed.

Preparation of ZnF 2 and ZnF 2–BaF 2 thin films by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Crystalline and amorphous ZnF 2 and ZnF 2-BaF 2 thin-films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition. The Zn and Ba β-diketone chelates and an NF 3 gas were used as starting materials and a fluorinating gas, respectively. Crystalline and transparent ZnF 2 thin-films were obtained on CaF 2(111) substrates kept at 300°C at the deposition rates of 0.2–0.8 μm/h. The thin film prepared at the 0.2 μm/h deposition rate was oriented along a [110] direction. The ZnF 2 thin-film deposited on a substrate kept at 100°C was amorphous though it tinted yellowish brown and had IR absorption bands due to contaminants. Colorless and contaminant-free amorphous thin-films were obtained in a 60ZnF 2·40BaF 2 composition.

Nitrogenated amorphous carbon films synthesized by electron cyclotron resonance plasma enhanced chemical vapor deposition

Nitrogenated amorphous carbon (a-CN x :H) films were investigated as protective overcoats for industrial applications. Thin a-CN x :H films have been deposited on silicon by electron cyclotron resonance plasma-enhanced chemical vapor deposition. The substrate bias was found to play an important role in determining the chemical compositions and mechanical properties of the films. The surface roughness and hardness of the films can reach 1.4 Å and 20 GPa, respectively. The influence of mechanical properties by hydrogen was studied. A correlation exists between the background slope of Raman spectra and the hydrogen content as determined by elastic recoil detection analysis.

1.54 μm Er3+ photoluminescent properties of erbium-doped Si/SiO2 superlattices

The 1.54 μm Er3+ photoluminescent properties of erbium-doped Si/SiO2 superlattices are investigated. Two superlattice films, one with erbium in Si layers and the other with erbium in SiO2 layers, were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition of SiH4 and O2 with cosputtering of erbium and subsequent rapid thermal anneal. Both display Er3+ luminescence, but it is stronger with longer luminescent lifetime and less temperature quenching when erbium is in the SiO2 layer. The results demonstrate that by using quantum structures, nonradiative deexcitation of Er3+ may be suppressed, and that carrier recombination events, which excite Er3+ ions, may be physically separated from Er atoms and still lead to an efficient Er3+ luminescence.

Optoelectronic and structural properties of amorphous silicon–carbon alloys deposited by low-power electron-cyclotron resonance plasma-enhanced chemical-vapor deposition

The optoelectronic and structural properties of hydrogenated amorphous silicon-carbon alloys (a-SiC:H) are studied over the entire compositional range of carbon content. The films are prepared using low-power electron-cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition. The carbon content was varied by using different methane (or ethylene-)-to-silane gas phase ratios and by introducing the methane (or ethylene) either remotely into the plasma stream or directly through the ECR source, together with the excitation gas (hydrogen). Regardless of the deposition conditions and source gases used, the optical, structural and transport properties of the a-SiC:H alloys followed simple universal dependencies related to changes in the density of states associated with their structural disorder. The deep defect density from photothermal deflection spectroscopy, the ESR spin density, the steady state and the transient photoluminescence, the dark and photoconductivity, the temperature of the hydrogen evolution peaks and the bonding from infrared spectroscopy are correlated to the Urbach tail energy, the B factor of the Tauc plot and E04 (defined as the energy at which the absorption coefficient is equal to 104 cm−1). Silicon-rich and carbon-rich regions with very different properties, corresponding approximately to carbon fractions below and above 0.5, respectively, can be distinguished. The properties of the ECR a-SiC:H alloys are compared with those of alloys deposited by rf glow discharge.

Silicon nitride thin films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Using an electron cyclotron resonance plasma compact source, we have studied the deposition of silicon nitride films at low deposition temperature (&amp;lt;300 °C) and low microwave power (&amp;lt;250 W). Nitrogen plasma and pure silane have been used as gas precursors. We report on the effect of the main process parameters on the composition and properties of the films. We show that each experimental parameter has an optimal range of values or a threshold value necessary to obtain films with high dielectric quality. For a deposition temperature of 300 °C, the best films exhibit a resistivity of 1015 Ω cm and a soft breakdown field (at 10−9 A cm−2) of 3 MV cm−1. The physicochemical properties of the films are close to those of stoichiometric silicon nitride: N/Si ratio of 1.33, optical index value of 2 at 3 eV and etch rate of 10 Å/min. Moreover, we observed strong correlations between the physicochemical and the electrical properties of the deposited films, over the entire range of process parameters.

ETCHING PROPERTIES OF AMORPHOUS HYDROGENATED CARBON FILMS IN A MULTIPOLE ELECTRON CYCLOTRON RESONANCE OXYGEN PLASMA SYSTEM

The etching properties of amorphous hydrogenated carbon films deposited from benzene vapor in a multipole electron cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition system have been investigated.Etch rates of these carbon films as a function of the process variables,includ-ing gas pressure and microwave power were measured,and compared with other resist materials.The results show that the film has high etching resistance against oxygen,and etch rate of the film not only closely correlated with etching process parameters,but also with the deposition conditions.This film could be used as a resist in dry etching process.

Effect of hydrogenation on room-temperature 1.54 μm Er3+ photoluminescent properties of erbium-doped silicon-rich silicon oxide

The effect of hydrogenation on the room-temperature 1.54 μm Er3+ photoluminescent properties of erbium-doped silicon-rich silicon oxide thin films is investigated. Two samples with 7 and 1 at. % excess silicon and 0.4 at. % erbium were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition of SiH4 and O2 with cosputtering of erbium and subsequent rapid thermal anneal at 900 °C. Hydrogenation by exposure to D plasma doubles the 1.54 μm Er3+ luminescence intensity from the high excess silicon content sample but halves that from the low excess silicon content sample. The lifetimes and excitation power dependence of Er+ luminescence show that hydrogenation primarily affects the active erbium fraction, increasing it in case of the high excess silicon sample but decreasing it in case of the low excess silicon content sample. With proper treatments, Er3+ luminescence lifetime of over 7 ms is obtained.