Resonance Plasma-enhanced Chemical Vapor Deposition Research Articles

Optical and mechanical properties of nanocrystalline aluminum oxynitride films prepared by electron cyclotron resonance plasma enhanced chemical vapor deposition

Aluminum oxynitride (AlON) films were prepared on silicon, glass and polymer substrates using electron cyclotron resonance plasma-enhanced chemical vapor deposition. The composition, structure, optical and mechanical properties were investigated. It was found that the composition of AlON films varies from nearly pure AlN to Al 2O 3, controlled by O 2 flow rate. Films deposited at room temperature is amorphous with hardness of 9.1–9.4 GPa, while those deposited at high temperature is crystalline with grain size of 10–20 nm. The hardness of crystalline films accords with the mixture rule. All AlON films are transparent and the transmittance increases with increasing O 2 concentration.

Conductance Transient Comparative Analysis of Electron-Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposited SiNx, SiO2/SiNx and SiOxNy Dielectric Films on Silicon Substrates

An interface quality comparative study of metal-insulator-semiconductor (MIS) structures based on SiNx, SiO2/SiNx and SiOxNy dielectric films deposited on silicon substrates by electron-cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) has been carried out. Overall interpretation of deep-level transient spectroscopy (DLTS) and conductance transient (G-t) measurements enables us to conclude that the interface quality of Al/SiOxNy/Si MIS structures is superior to those of Al/SiNx/Si devices. Moreover, we have proved that thermal treatments applied to Al/SiOxNy/Si capacitors induce defect passivation, possibly related to the presence of hydrogen in the films, and disorder-induced gap-state (DIGS) density maxima can decrease to values even lower than those corresponding to Al/SiNx/SiO2/Si devices.

Wet etching studies of silicon nitride thin films deposited by electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition

Silicon nitride films of various compositions have been deposited on silicon substrate by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique from mixtures of Ar, N 2 and SiH 4 as precursors. Film composition and refractive index as a function of deposition parameters like gas flow ratio and pressure were studied. Wet etching studies were conducted using diluted phosphoric acid and buffered oxide etch (BOE) solutions of various concentrations. The etching studies using phosphoric acid were conducted in the temperature range of 70–90 °C. For BOE the temperature range was 25–55 °C. The etch rate with BOE solution is much higher than with phosphoric acid. The results indicate that the mechanism of etching with phosphoric acid is different from that with BOE solution.

Interfacial State Density and Conductance-Transient Three-Dimensional Profiling of Disordered-Induced Gap States on Metal Insulator Semiconductor Capacitors Fabricated from Electron-Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposited SiOxNyHz Films

An electrical characterization of Al/SiOxNyHz/Si metal–insulator–semiconductor (MIS) structures has been carried out. SiOxNyHz films of different compositions have been obtained from these structures by varying gas flow in the electron-cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) system. The presence of nitrogen in the films increases the dielectric constant value and degrades the interface quality, as our measurements demonstrate. The effect of thermal annealing has also been determined. Capacitance–voltage (C–V) results show that unannealed samples exhibit positive flat-band voltages, whereas annealed ones exhibit negative values. On the other hand, from deep-level transient spectroscopy (DLTS) measurements we can conclude that interfacial state density diminishes when thermal treatments are applied. Moreover, conductance transient analysis provides the energetic and spatial distribution of defects in the films and demonstrates that thermal improvement affects not only the interface, but also the insulator bulk.

Silicon Nitride Films Deposited Using ECR-PECVD Technique for Coating InGaAlAs High Power Laser Facets

The lifetime of InGaAs/AlGaAs high power lasers increased significantly when silicon nitride (SiN) films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique were used as optical coatings for the emitting facet of the lasers. Precleaning of the surfaces to be coated, and the stable low stress in the film have been found to be highly valuable for these lasers. The films were deposited at a low temperature (90°C) from a mixture of Ar, and as precursors. Rutherford backscattering spectroscopy and nuclear reaction analysis measurements reveal that the composition of the film is 48 atom % Si, 32 atom % N, and 20 atom % H. The most important properties of the films are low intrinsic stress and a negligible hysteresis in the dependence of stress on temperature upon thermal cycling. The stress measurements indicate that all hydrogen atoms in the films are chemically bonded. © 2003 The Electrochemical Society. All rights reserved.

Conductance transient comparative analysis of ECR-PECVD deposited SiNx, SiO2/SiNx and SiOxNy dielectric films on silicon substrates

ABSTRACTA study of metal-insulator-semiconductor (MIS) structures based on SiNx, SiO2/SiNx and SiOxNy films deposited on silicon by electron cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD) is presented. Interface trap densities measured by deep level transient spectroscopy (DLTS) are higher for silicon oxynitride-based MIS capacitors than for silicon nitride and silicon oxide-silicon nitride-based ones. However, conductance transient analysis demonstrated that Al/SiNx/Si devices exhibit the highest disordered-induced gap states (DIGS) density, whereas the lowest one corresponds to Al/SiNx/SiO2/Si, and silicon oynitride-based MIS capacitors show an intermediate behaviour. In addition, thermal treatments applied to Al/SiOxNy/Si samples reduce DIGS densities to values even lower than those corresponding to Al/SiNx/SiO2/Si devices.

Electrical characterization of MIS capacitors fabricated from ECR-PECVD silicon oxide and silicon nitride bilayer films

In this study, a comparative electrical characterization of Al/SiNx/Si and Al/SiNx/SiO2/Si MIS structures has been carried out. Both SiO2 and SiNx films have been deposited by using electron-cyclotron resonance plasma-enhanced chemical vapor deposition method. C-V results show that samples without SiO2 have more defects than those with SiO2. Deep-level transient spectroscopy and conductance transient measurements demonstrate that as for the samples containing the SiO2 film, these defects are mostly concentrated in the insulator/semiconductor interface, whereas in the other case defects are spatially distributed into the insulator.

Coefficient determination related to optical gain in erbium-doped silicon-rich silicon oxide waveguide amplifier

Gain-determining coefficients in Er-doped, nanocrystal-Si (nc-Si) sensitized silica waveguide amplifiers are investigated. Single-mode, Er-doped silica waveguides with nc-Si embedded in them were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition of Er-doped a-Si:Ox (x<2) followed by a high-temperature anneal to precipitate nc-Si. Exciting the Er ions via nc-Si by pumping the waveguide from the top with the 477 nm line of an Ar laser resulted in an enhancement of the transmitted 1535 nm signal of up to 14 dB/cm, indicating a possible net gain of up to 7 dB/cm. From the dependence of the signal enhancement upon the pump power, an emission cross section of 2×10−19 cm2 at 1535 nm and an effective excitation cross section of ⩾10−17 cm2 at 477 nm is obtained.

Direct Crystallization and Characterization of Bi3TiTaO9 Thin Films Prepared by Metalorganic Chemical Vapor Deposition

Bi3TiTaO9 (BTT) thin films were prepared on (111)Pt/Ti/SiO2/Si substrate by electron cyclotron resonance plasma-enhanced metalorganic chemical vapor deposition (ECR-MOCVD). BTT thin films deposited at 550°C were found to consist of a single phase of bismuth layer structure by X-ray diffraction (XRD). This temperature was lower than that reported in the data for obtaining single phase SrBi2Ta2O9 (SBT) thin films prepared by MOCVD. Furthermore, the reciprocal space mapping of BTT thin films showed the (103)-preferred orientation of this film, as well as the orientation of SBT thin films. The dielectric constant, εr, and loss tangent, tan δ, of the BTT thin film were 180 and 3% at 1 MHz, respectively. An abrupt increase of the leakage current of this film was observed at about 280 kV/cm.

A hybrid Nb/CMOS integration process for superconducting tunnel junction imaging arrays

A process for hybrid superconductor/CMOS integration was developed for the fabrication of extremely sensitive color-imaging arrays using superconducting tunnel junctions. A Nb-AlO/sub x/-Nb process was used to fabricate arrays of junctions directly on top of CMOS devices. The CMOS wafers required the development of a planarization process suitable for subsequent tunnel-junction fabrication. The process involved the deposition of a sacrificial oxide layer by electron cyclotron resonance plasma-enhanced chemical vapor deposition, chemical-mechanical polishing, and a layer of spin-on glass. A process was also developed for via contacts through the oxide layer that optimized the stability of the contacts. The critical current spreads of the arrays (50 junctions) were as small (spread about 1% for 3 /spl mu/m /spl times/ 3 /spl mu/m junctions) as on bare silicon wafers.

Electrochemistry of Nitrogen-Incorporated Hydrogenated Amorphous Carbon Films

Nitrogen-doped hydrogenated amorphous carbon, films, were synthesized by microwave electron cyclotron resonance plasma-enhanced chemical vapor deposition, using as precursors. Such films, with thickness in the range of a few tens of nanometers, very smooth, and pinhole free, appear as electrode materials with reactivity and effective window potential similar to those of boron-doped polycrystalline diamond or nitrogen-doped amorphous diamond. These films, grown on Si or Ti substrates, were investigated with regard to their electrochemical reactivity toward outer sphere redox reactions, such as ferri/ferrocyanide, by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). It has been established that the electrical conductivity and the electrochemical reactivity vary in opposite directions, the optimum found for the former being around a nitrogen atomic fraction of 0.3, and for the latter around 0.05. EIS showed that for a fast redox reaction, the behavior, though looking similar to a simple electron transfer on a metallic substrate with a partial diffusion control, has another contribution, which could be explained by the presence of a layer at the interface with the solution, in which electron transport would occur by hopping between many localized states. Ti substrate improves the electrical contact with the carbon film with respect to the Si substrate, which decreases the apparent potential difference between the anodic and cathodic redox peaks by about 150 mV. The minimum value of found for the charge-transfer rate constant of lies in the range so far obtained for other modified carbon materials, such as boron-doped polycrystalline diamond or nitrogen-doped amorphous diamond thin films. © 2002 The Electrochemical Society. All rights reserved.

Effects of initial layers on surface roughness and crystallinity of microcrystalline silicon thin films formed by remote electron cyclotron resonance silane plasma

We have observed μc-Si:H films grown in the glass substrate in electron cyclotron resonance plasma-enhanced chemical vapor deposition employing two-step growth (TSG) method, where the seed layer was formed without charged species firstly, and subsequently, the film with charged species. The μc-Si:H films with smooth surface and high crystallinity were synthesized with a relatively high deposition rate at a low substrate temperature by TSG. By Fourier transform infrared attenuated-total reflection, it was found that the surface roughness and crystallinity of seed layer were related to the ratio of SiH bonds over SiH2 ones in the film. Consequently, the control of chemical bonds at the initial layer is of importance and TSG method is effective for the formation of μc-Si:H film with high quality.

Controlling the formation of luminescent Si nanocrystals in plasma-enhanced chemical vapor deposited silicon-rich silicon oxide through ion irradiation

The effect of ion irradiation on the formation of luminescent Si nanocrystals from silicon-rich silicon oxide (SRSO) films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) whose Si content ranged from 33 to 50 at. % is investigated. As-deposited SRSO films contained a high density of irregular-shaped Si nanocrystals. Irradiating these films with 380 keV Si at room temperature to a dose of 5.7×1015 cm−2 prior to anneal at 1000 °C is found to increase the luminescence intensity due to Si nanocrystals over the films. Based on the x-ray photoemission spectra and the dependence of the luminescence intensity on the irradiating ion dose, anneal time, and the silicon content of the film, we propose the destruction of pre-existing Si clusters by ion irradiation to be an important factor responsible for the observed enhancement of luminescence, and suggest that preanneal irradiation may be a viable method to control the formation of luminescent Si nanocrystals in PECVD-deposited silicon-rich silicon oxide.

Formation mechanism of C/SiC/C multi-layers during self-propagating high-temperature synthesis

In order to study the formation mechanism of a silicon carbide layer during the self-propagating high-temperature synthesis (SHS) reaction between graphite and silicon layers, multi-layers of carbon–silicon carbide–carbon on UO 2 pellets were prepared and analyzed. The carbon and silicon were deposited by thermal decomposition of propane in a chemical vapor deposition (CVD) unit and a microwave-pulsed electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) unit using silane and propane gases, respectively. The activation energy for the formation of silicon carbide determined by differential scanning calorimetry (DSC) depended on the initial carbon precursors. The final product layer was a fine, crystalline beta-silicon carbide. The numerically estimated value of the combustion limit was 0.06 at an initial temperature of 1200 °C, which supported the finding that pre-heating above the temperature was required for the formation of the silicon carbide. From thermal analysis and microstructure observations, the formation mechanism of the silicon carbide layer included carbon diffusion at the interface between liquid silicon and silicon carbide.

C-Axis oriented AlN films prepared on diamond film substrate by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition of aluminum nitride (AlN) films was performed on diamond film substrates using electron cyclotron resonance which have an attractive potential for application such as surface acoustic wave devices operating at high frequency. N 2 and AlCl 3 were used as reactant precursors. The dependences of the film morphology, film orientation, deposition rate on the diamond crystal orientation, substrate temperature and microwave power were investigated by scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction. c-Axis oriented pure AlN films have been achieved.

Preparation and Characterization of Pb(Zr,Ti)O3 Films Deposited on Pt/RuO2 Hybrid Electrode for Ferroelectric Random Access Memory Devices

Polycrystalline Pb(Zr,Ti)O3 (PZT) films were fabricated at a low temperature of 450°C by the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method. Stoichiometric PZT films with the pure perovskite phase could be obtained over a wider range of deposition conditions on Pt/RuO2 hybrid electrodes than on RuO2 electrodes. PZT capacitors fabricated on Pt/RuO2 hybrid electrodes showed low leakage current and superior polarization characteristics compared with those on RuO2 electrodes. PZT capacitors fabricated on Pt/RuO2 were not as fatigue-free as those on RuO2 but had higher resistance to fatigue than those on Pt. The introduction of a PbTiO3 buffer layer prior to PZT film deposition on Pt/RuO2 improved the fatigue characteristics by suppressing the formation of nonstoichiometric interfacial layers. Good leakage current property (J: 5.8 ×10-7 A/cm2 at 200 kV/cm) and fatigue characteristic (P* - P∧: 9% drop after 4 ×109 fatigue cycles) could be obtained for the 110-nm-thick PZT film using Pt/RuO2 hybrid top and bottom electrodes. This electrode structure is thought to be promising for use as a capacitor of high-density ferroelectric random access memory (FRAM) devices. The fatigue model that can explain the fatigue characteristics of PECVD-PZT capacitors with various hybrid electrode configurations is also suggested.

The effects of varying plasma parameters on silicon thin film growthby ECR plasma CVD

The technique of electron cyclotron resonance (ECR) plasmaenhanced chemical vapour deposition (PECVD) is increasingly being used inelectronic and photonic device applications. ECR offers a number ofadvantages including improved control of the deposition process, lessdamage to the growing film and the possibility of high deposition rates.ECR occurs in a plasma under appropriate magnetic and electric fieldconditions. In most cases, as in our system, this is achieved with acombination of 2.45 GHz microwave radiation and a 0.0875 T magnetic field,due to the use of standardized microwave supplies. We have studied theeffects on silicon film growth of changing the magnetic field configurationto produce one or more planes of ECR within the system, and of changing thepositions of the plane(s) relative to the deposition substrate. The filmswere grown in silane-hydrogen discharges. The magnetic field in our systemwas provided by two electromagnets. It was measured experimentally for anumber of operating current values and then a detailed profile achieved bymodelling using a proprietary software package. A process conditiondischarge under identical magnetic field configurations to growth wasanalysed by the use of a Langmuir probe and the results correlated withfilm properties determined by Raman spectroscopy and Dektak profilometry.

Ultrathin fluorinated silicon nitride gate dielectric films formed by remote plasma enhanced chemical vapor deposition employing NH3 and SiF4

Ultrathin fluorinated silicon nitride (SiNx) films of 4 nm in thickness were formed on a Si substrate at 350 °C in the downflow of electron cyclotron resonance plasma-enhanced chemical vapor deposition employing ammonia and tetrafluorosilane (NH3/SiF4) gases. Ultrathin fluorinated SiNx film was evaluated for use as a gate dielectric film. The observed properties indicated an extremely low leakage current, one order of magnitude lower than thermal SiO2 of identical equivalent oxide thickness, as well as an excellent hysteresis loop (20 mV) and interface trap density (Dit=4×1011 cm−2) in the capacitance–voltage characteristics. The film structures and the surface reactions for the fluorinated SiNx film formation were examined via in situ x-ray photoelectron spectroscopy. in situ Fourier-transform infrared reflection absorption spectroscopy, in situ atomic force microscopy, and thermal desorption mass spectroscopy. The control of the fluorine concentration in the SiNx films was found to be a key factor in the formation of fluorinated SiNx films of high quality at low temperatures. Fluorinated SiNx is the effective material for application in ultrathin gate dielectric film in ultralarge-scale integrated circuits.

Low-Temperature Formation of Device-Quality SiO2/Si Interfaces Using Electron Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposition

Low-temperature formation of SiO2/Si interfaces using electron cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition (PECVD) was investigated. It was found that the density of interface trap states (Dit) decreased with decreasing substrate temperature during film deposition and performing the post deposition annealing at 333°C in N2 or H2O atmosphere. The average Dit was 3 to 4×1011 cm-2 eV-1 when the substrate temperature was 300°C, while decreasing the substrate temperature to room temperature decreased it to 1.8×1010 cm-2 eV-1. These results indicate that device-quality-SiO2/Si-interface formation is possible using low-temperature processes of ECR PECVD and post deposition annealing.

Preparation of amorphous fluoride films by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Amorphous ZnF 2, ZnF 2–BaF 2, AlF 3 and AlF 3–BaF 2 films were prepared on CaF 2(1 1 1) substrates by an electron cyclotron resonance plasma-enhanced chemical vapor deposition (CVD) technique. Metal β-diketone chelates and NF 3 gas were used as starting materials and a fluorinating gas, respectively. ZnF 2 films deposited on the substrates kept at 300°C and 100°C were crystalline and amorphous, respectively. The crystalline ZnF 2 thin film prepared at a deposition rate of 0.2 μm h −1 was oriented along a [1 1 0] direction. The amorphous ZnF 2 film, tinted yellowish brown, had an IR spectra which were due to contaminants. Colorless and contaminant-free amorphous films were obtained for a 60ZnF 2·40BaF 2 composition. On the other hand, AlF 3 films generated on the CaF 2(1 1 1) substrate kept at 300°C were amorphous and colorless. We also found that amorphous 80AlF 3·20BaF 2 and 60AlF 3·40BaF 2 films could be synthesized at a deposition rate of 1.5 μm h −1 .