Volume 21, Issue 4, July 2003
- regular articles
- shop notes
- papers from the 49th international symposium of the avs
- advancing toward sustainability topical conference
- biomaterial interfaces
- electrochemistry and fluid-solid interfaces
- magnetic interfaces and nanostructures
- micro-electro-mechanical systems
- manufacturing science and technology
- nanometer-scale science and technology
- emerging opportunities and issues in nanotubes and nanoelectronics
- plasma science and technology
- plasma science and technology i
- plasma science and technology ii
- surface engineering
- surface science
- surface science i
- surface science ii
- thin films
- vacuum technology
- electrochemistry and fluid–solid interfaces/surface science
- electronics/semiconductors/magnetic interfaces and nanostructures
- magnetic interfaces and nanostructures/nanometer-scale science and technology
- magnetic interfaces and nanostructures/thin films
- micro-electro-mechanical systems/thin films
- manufacturing science and technology/surface engineering
- plasma science and technology/micro-electro-mechanical systems
- plasma science and technology/thin films
- surface engineering/nanometer-scale science and technology
- surface engineering/thin films
Index of content:
Transitional change to amorphous fluorinated carbon film deposition under energetic irradiation of mass-analyzed carbon monofluoride ions on silicon dioxide surfaces21(2003); http://dx.doi.org/10.1116/1.1578653View Description Hide Description
We have studied both the etching of film and the growth of an amorphous fluorinated carbon (a-C:F) film by mass-analyzed fluorocarbon ion irradiation. This experiment was done in an ultrahigh vacuum with a pressure of Pa even during irradiation. When using a carbon monoflouride ion with an energy of 300 eV to irradiate, it was found that film a few nm thick was initially etched away. Then, an a-C:F film was continuously deposited on the surface as the ion dose exceeded about Using in situ x-ray photoelectron spectroscopy analysis, it was determined that carbon accumulates on the surface at this early stage as the ion dose increases, so that this transition is resulted by the surface modification on which the ion itself irradiates the surface. Especially in highly ionized fluorocarbon plasmas, surface conditions such as the carbon concentration affect possibly etching performance.
- REGULAR ARTICLES
Thermal stability and hydrogen atom induced etching of nanometer-thick a-Si:H films grown by ion-beam deposition on Si(100) surfaces21(2003); http://dx.doi.org/10.1116/1.1575213View Description Hide Description
Amorphous hydrogenated silicon (a-Si:H) films in the thickness range 0.1–4.5 nm were deposited on Si(100) surfaces at 350 K using the ion-beam-deposition method. The thermal stability of these a-Si:H films was studied by temperature programmed desorption spectroscopy. The films are stable up to 500 K, where a-Si:H starts to decompose via evolution of hydrogen and silane Approximately 99% of the hydrogen initially bound to the Si network was detected in the hydrogen channel. The hydrogen evolution peaks at ∼780 K caused by the decomposition of monohydride groups; the presence of groups is indicated by hydrogen desorption below 700 K. The silane desorption states at 625 and 750 K reveal the existence of two different types of silyl groups. Etching of a-Si:H by impinging gas-phase H atoms was investigated in the temperature range from 150 to 700 K by in situ mass spectrometry. Silane was the sole etch product observed. The formation of silane proceeds via direct abstraction of silyl precursor groups by impinging hydrogen atoms, the silyl abstraction probability increases by a factor of 6 with increasing substrate temperature between 150 and 525 K. However, the steady-state erosion rate is controlled by the supply of silyl groups by successive hydrogenation of the Si network with the formation of as bottleneck of the silyl supply.
21(2003); http://dx.doi.org/10.1116/1.1575214View Description Hide Description
Two Mg-doped GaNfilms with different doping concentrations were grown by a metalorganic chemical vapor deposition technique. Photoluminescence(PL) experiments were carried out to investigate the optical properties of these films. For highly Mg-doped GaN, the PL spectra at 10 K are composed of a blue luminescence (BL) band at 2.857 eV and two excitonic luminescence lines at 3.342 eV and 3.282 eV, in addition to a L2 phonon replica at 3.212 eV. The intensity of the L1 line decreases monotonously with an increase in temperature. However, the intensity of the L2 line first slowly increases at first, and then decreases quickly with an increase in temperature. The two lines are attributed to bound excitonic emissions at extended defects. The BL band is most likely due to the transition from deep donor complex to Mg shallow acceptor. From the temperature dependence of the luminescence peak intensity of the BL band, the activation energy of acceptor Mg was found to be 290 meV.
21(2003); http://dx.doi.org/10.1116/1.1575227View Description Hide Description
An electron cyclotron resonance (ECR)-plasma reactor has been built to do energetic ion deposition of refractorymetals in vacuum. The system uses an E-beam gun to create refractorymetal flux. The neutral metal flux feeds into a microwave resonator and forms pure metalplasma created by electron cyclotron resonance. The metal ions are extracted to a biased substrate for direct deposition. A retarding field energy analyzer is developed and used to measure the kinetic energy of metal ions at the substrate location. A high-quality niobiumthin film is obtained through this deposition system. The niobium film exhibits an excellent superconducting transition. The niobium ion energy distribution has been measured. The niobium ion at the substrate location has a median kinetic energy of 64 eV with an energy spread of 20 eV under certain plasma conditions.
Effect of sputtering pressure on residual stress in Ni films using energy-dispersive x-ray diffraction21(2003); http://dx.doi.org/10.1116/1.1575229View Description Hide Description
A procedure for determining the residual stress in thin films using energy dispersive x-ray diffraction was investigated. The effect of the sputtering pressure on the residual stress in dc magnetron sputteredNi films was studied in greater detail using this approach. The behavior reported suggested the possibility of controlling or influencing the sign and/or magnitude of the residual stress. In addition, the stress variation with increasing negative bias voltage is also presented. In the range studied, between −15 and −150 V, residual stress is always tensile.
Structural and mechanical properties of diamond-like carbon films deposited by direct current magnetron sputtering21(2003); http://dx.doi.org/10.1116/1.1575231View Description Hide Description
The microstructure, morphology, and mechanical properties of diamond-like carbon (DLC) filmsdeposited by direct current magnetron sputtering were investigated for microelectromechanical systems applications. Film properties were found to vary markedly with the ion energy and ion-to-carbon flux ratio Cross-sectional high-resolution transmission electron microscopy revealed an amorphous microstructure. However, the presence of nanometer-sized domains at eV was detected. Film stresses, σ, which were compressive in all cases, ranged from 0.5 to 3.5 GPa and depended on the flux ratio as well as ion energy. The hardness (H), Young’s moduli (ε), and elastic recovery (R) increased with to maximum values of GPa, GPa, and at eV and However, near edge x-ray absorption fine structure and electron energy-loss spectrum analysis showed that the content of the films does not change with or The measured change in mechanical properties without a corresponding change in ratio is not consistent with any previously published models. We suggest that, in the ranges 5 eV eV and 1.1 the presence of defective graphite formed by subplanted C and Ar atoms has the dominant influence on the mechanical properties of DLC films.
X-ray photoemission spectra and x-ray excited Auger spectrum investigation of the electronic structure of21(2003); http://dx.doi.org/10.1116/1.1575212View Description Hide Description
Information on the bonding states of the compositional atoms and on the occupied energy states of the crystals have been obtained by investigating the Pd 3d and P and S 2p core levels and the valence band region with the x-ray photoemission spectroscopy. In particular, as far as core levels are concerned, each XPS spectrum, apart from the spin-orbit splitting, exhibits a single-peak structure suggesting the absence of nonequivalent sites for the compositional atoms. The analysis of the chemical shifts in the core-level binding energies of the constituents emphasizes their cation or anion-type behavior. As to the valence band (VB) XPS spectrum, two regions are distinguished and interpreted on the basis of the comparison with the VB XPS spectra of other palladium and compounds and of some thiophosphates. Confirmation of an involvement of the Pd 4d in the bonding is also given by the analysis of the spectral shape of the x-ray induced Pd Auger transition.
21(2003); http://dx.doi.org/10.1116/1.1577135View Description Hide Description
Molecular structures of fluorocarbon films synthesized by plasmas were analyzed by laser desorptiontime-of-flight mass spectrometry (LD-TOFMS). Mass peaks of positive and negative ions with up to 250 were observed in the mass spectra. Most of these ions were assigned as atomic hydrogen, atomic fluorine, carbonclusters, hydrocarbon clusters, fluorocarbon clusters, and hydrofluorocarbon clusters. The mass spectra changed sensitively with the partial pressure of The LD-TOFMS analysis showed that the films changed from a polytetrafluoroethylene-like film into crosslinked carbon- and hydrogen-rich one by the addition of The change in the chemical composition of the mass spectrum was consistent with the analyses by conventional x-ray photoelectron spectroscopy and Fourier transform infrared absorption spectroscopy. It is emphasized that LD-TOFMS can be used for the analysis of the degree of polymerization, which is an advantage of LD-TOFMS over the conventional analysis methods.
Pulsed laser ultrahigh vacuum deposited silicon in the presence of excess cesium and oxygen studied with x-ray photoelectron spectroscopy and atomic force microscopy21(2003); http://dx.doi.org/10.1116/1.1577137View Description Hide Description
Si/Cs/O clusters were prepared in an ultrahigh vacuum system with pulsed laserablation of Si in the presence of Cs vapor and molecular oxygen. The effects of an ambient, the pressure, and the deposition sequence of Cs and on the oxidation state of cesium oxides and silicon oxides, as well as on the formation of Si/Cs/O clusters, were studied with x-ray photoelectron spectroscopy and atomic force microscopy(AFM). Oxygen spectra were deconvoluted to cesium oxide(s) at around 530.5 eV and silicon oxide(s) at 532.3 eV. From the low binding energy side to the high binding energy side, spectra were assigned to negatively charged Si clusters (94 and 96 eV), silicon suboxide (102 eV), (104 eV), and Si/Cs/O clusters (106 eV), respectively. The high binding energy species was explained by the formation of clusters. Surface morphologies were influenced by the oxidation state of cesium oxides and their amount. The work function decrease as much as 0.5±0.1 eV was measured with ex situAFM.
21(2003); http://dx.doi.org/10.1116/1.1575230View Description Hide Description
During 1879 Thomas Edison’s Menlo Park, New Jersey laboratory developed the means to evacuate glass lamp globes to less than a mTorr in 20 min and in mid-1880 began production of carbon-filament incandescent lamps. Among Edison’s nearly 1100 U.S. patents are five for vacuum pump improvements, and at least eight others that are vacuum-related; all applied for between 1880 and 1886. Inspired by an 1878 article by De La Rue and Müller [Philos. Trans. R. Soc. London, Ser. A 169, 155 (1878)] on studies of glow discharges, Edison devised a combination pump using the Geissler pump as a rough pump and the Sprengel pump for continuous exhaustion. Edison’s patents described means to control the mercury flow and automate the delivery of the mercury to banks of up to a hundred pumps. Other patents described various means to remove residual gases during lamp processing.
21(2003); http://dx.doi.org/10.1116/1.1575211View Description Hide Description
Glass plates of 20 cm diameter have been etched by in a pulsed capacitively coupled 13.56 MHz discharge. The plates were mechanically clamped to the cooled substrate holder and allowed to heat due to ion bombardment. The average rf power was set at 220 W and the pulse frequency varied up to 200 kHz for duty cycles between 10% and 100%. For a pressure of 50 mTorr, pulse frequencies around 100 kHz and duty cycles below 30%, the etch rate was about double that of the continuous case and the glass plate temperature was between 90 and 100 °C about 30° below the continuous case. These results show that large plates of glass can be etched rapidly at 0.16 μm per minute at temperatures below the cross linking temperature of a photoresist mask.
Effects of Si addition on the microstructural evolution and hardness of Ti–Al–Si–N films prepared by the hybrid system of arc ion plating and sputtering techniques21(2003); http://dx.doi.org/10.1116/1.1576765View Description Hide Description
Ti–Al–Si–N films were deposited on WC–Co substrates by the hybrid coating system of arc ion plating method for Ti–Al sources and dc magnetron sputtering technique for Si incorporation. The synthesized Ti–Al–Si–N films were revealed as composites of solid-solution (Ti,Al,Si)N crystallites and amorphous by instrumental analyses such as x-ray diffraction, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The Si addition in Ti–Al–N films affected the refinement and uniform distribution of crystallites by percolation phenomenon of amorphous silicon nitride similar to that of the Si effect in TiN film. The solubility limit of Si in the crystal is believed to be about 6 at. %. No free Si was observed due to the very high ionization rate of nitrogen gas in the arc plasma. As the Si content increased up to about 9 at. %, the hardness of Ti–Al–N film steeply increased from 30 GPa to about 50 GPa. Ti–Al–Si–N films having the maximum hardness showed the nanocomposite microstructure consisting of fine (Ti,Al,Si)N crystallites, about 8 nm in size, dispersed uniformly in the amorphous matrix.
21(2003); http://dx.doi.org/10.1116/1.1577134View Description Hide Description
Silicon dioxide thin films have been prepared at room temperature by remote plasma-enhanced chemical vapor deposition in a downstream reactor by using as a volatile precursor and a microwave electron cyclotron resonance external source. Experiments are done at constant pressure by changing the relative amount of Ar species R in the plasma gas. The aim was to obtain thin films with low density and, therefore, low refractive index. Characterization of the species of the plasma is carried out by optical emission spectroscopy. The changes of the plasma conditions are correlated with the growing rate and microstructure of the films, the latter determined by atomic force microscopy and infrared spectroscopy. It is found that the growing rate of the films decreases and their roughness increases as R increases. The optical properties of thin films are analyzed by optical ellipsometry. A decrease in the refractive index is found for the films grown with high values of R. The possible routes for activation of the precursor and the formation of the thin films are discussed.
Microstructural and optical properties of aluminum oxide thin films prepared by off-plane filtered cathodic vacuum arc system21(2003); http://dx.doi.org/10.1116/1.1577132View Description Hide Description
Transparent, amorphous, surface smooth, and hard aluminum oxide thin films were deposited on Si (100) and quartz substrates by an off-plane filtered cathodic vacuum arc (FCVA) system. We systematically studied the optical properties, such as transmittance and optical constants, of the aluminum oxide thin filmsdeposited under various oxygen partial pressures. Experimental results show that the optical properties for aluminum oxide thin films are strongly dependent on oxygen partial pressure; the higher oxygen partial pressure causes much more oxygen to incorporate into the film thus inducing more modification of filmproperties. At proper oxygen partial pressure, the stoichiometric alumina film is obtained, which is smooth and dense. Additionally, it also displays good optical properties with a refractive index of at 550 nm. The properties exhibited by the alumina thin films manifest the potential applications for alumina thin films in optical coatings and for FCVA technology in deposition of metal oxide optical films.
21(2003); http://dx.doi.org/10.1116/1.1579015View Description Hide Description
A Monte Carlo based profile simulator was constructed that incorporated the dominant reaction mechanisms of surface chlorination under simultaneous neutral and ion bombardment, surface etching, and ion reflection. The profile simulation is based on the kinetics model developed from beam studies that measured the ion energy, ion and neutral fluxes and ion angular dependencies of ion-enhanced etching with Cl. The profile evolution of patterned samples with oxide hard mask etched in an inductively coupled plasmaetcher were simulated. The mechanisms of undercutting and microtrenching forming were discussed. Ions scattered from the neighboring hardmask were primarily responsible for the undercutting, while ions reflected from bowed feature sidewalls were primarily responsible for the microtrenching. The profile evolutions under different processing conditions were compared with experimental results and some etching artifacts were characterized and discussed. The neutral-to-ion ratio was found to influence the surface chlorination significantly, thus causing variation of profile evolution. Higher ion energy would give more ideal profiles due to increased ion directionality. However, higher ion energy also increased the etching rate and reduced the chlorination at the bottom of the feature. The reduced chlorination of the feature bottom relative to the sidewall increases the ratio of lateral etching to vertical etching, and decreases the etchinganisotropy. The influence of deposition and mask angle on feature profile evolution were also investigated.
Determination of -flux and -flux of ionized physical vapor deposition of titanium from multiscale model calibration with test structures21(2003); http://dx.doi.org/10.1116/1.1578652View Description Hide Description
In this article we determine physical parameters characterizing the ionized physical vapor deposition of titanium in a Hollow Cathode Magnetron by comparing experimental results obtained from suitable submicron test structures with a multiscale model. The model includes the reactor scale, the plasma sheath and presheath scale, and the feature scale. The reactor scale model delivers the energy and angular distribution of the neutral sputtered particles from the reactor geometry and an energy dependent collision model. The sheath and presheath model calculates the energy and angular distribution of the ions from the reactor model and a subsequent scattering model describes collisions in the presence of magnetic fields. The levelset-based feature scale simulator propagates the front according to local growth velocities which are calculated from Monte Carlo particle flux and reaction kinetics (derived from molecular dynamics calculation). The calibration is performed in two steps with help from bottle-shaped test structures as well as technologically relevant structures. First, hi-fill and ultra-hi-fill magnetron sputter processes of titanium are investigated in order to verify the transportmodel for the neutral particles. Second, a Hollow Cathode Magnetron sputter process of titanium is analyzed in order to verify the transportmodel for postionized particles. This analysis is performed for a floating substrate process and a process with rf-driven substrate bias. The postionized flux fraction of titanium in this technology is not calculated from a plasma model but treated as a free parameter. The prediction of the model and the comparison with the experimental data allow us to determine this value as under a standard condition. The ionized flux of argon relative to the ionized flux of titanium is determined as 2. The results show that the bottom and sidewall coverage of the process depends significantly on the angular dependence of the ionized component which is essentially a result of processes in the presheath. The validity of the model covers a variety of plasma and process conditions. It can be applied to other reactor concepts and materials.
21(2003); http://dx.doi.org/10.1116/1.1578654View Description Hide Description
When ionization gauges are used as reference or secondary standards, their stabilities are the most important features. Generally, only hot cathode gauges are used as reference or secondary standards in calibration services. Some traditional reasons preventing the use of cold cathode gauges are the presence of discontinuities in the current versus pressure characteristic, the ignition delay at very low pressures, and the poor stability especially under contaminating vacuum environments. Though current inverted magnetron designs are believed to avoid some of these problems, at least under clean conditions, no “hard facts” have been published to support this claim. Here, we present the experimental results of calibrations of three hot cathode gauges and two inverted magnetrons against a primary high-vacuum standard over the range to with gases of Ar, He, and respectively. During a continuous observation period of 72 h at a constant pressure of about hot cathode gauges showed better stabilities than inverted magnetrons in Ar, and He, but all gauges behaved similarly in Repeated calibrations over a period of about 6 months showed that all gauges had similar long-term stabilities in Ar, and He. For however, the stability of inverted magnetrons was better than that of hot cathode gauges. For different gases, the discontinuities of inverted magnetrons occurred at different pressures, making their calibrations more elaborate.
21(2003); http://dx.doi.org/10.1116/1.1578656View Description Hide Description
Chromiumaluminum oxynitride (Cr–Al–N–O) thin films have been prepared by pulsed laser deposition. Experiments were carried out by changing the surface area ratio of targets from 0% to 100%. The composition of the thin film prepared at was determined to be by Rutherford backscattering spectroscopy. From the result of grazing angle x-ray diffractometry, the phase transition of the Cr–Al–N–O thin films was clarified to occur, when the aluminum content in cations (x) ranged from 70 to 90 at. %. In addition, the thin films having composition close to the solubility limit were observed by transmission electron microscopy to contain chromium nitride particulates below 200 nm in diameter. The Cr–Al–N–O thin film with which was the hardest over the whole x range, had Vickers hardness above 4000. In this thin film, nanometer-sized crystallites were found in the grains. Moreover, the elastic modulus was shown to be higher than those of other Cr–Al–N–O thin films.
21(2003); http://dx.doi.org/10.1116/1.1575215View Description Hide Description
The etch rate of silicon by in a helicon reactor has been measured along with simultaneous actinometric measurements of the concentration of atomic fluorine in the gas phase for a variety of gas flow rates resulting in pressures in the mTorr range. A bias rf power was applied to the substrate to investigate the effect of ion energy on the etch rate. The etch rate was found to be proportional to the fluorine concentration and independent of the bias for the higher gas flow rates. However, at lower flow rates, the situation was more complicated and no simple model can explain the measurements.Measurements of the etch rate were also made in the afterglow of a repetitively pulsed discharge so that the directed ion energy would be reduced to the thermal motion after the rapid collapse of the plasma potential. A simple model was developed to explain the temporal etching phenomena in terms of the lifetime of the atomic fluorine.
X-ray diffraction study of residual stresses and microstructure in tungsten thin films sputter deposited on polyimide21(2003); http://dx.doi.org/10.1116/1.1578655View Description Hide Description
Structural and mechanical properties of metal/polymer systems are of great interest for technological applications since they strongly influence the quality and lifetime of these systems. The phase composition, microstructure, and residual stresses of tungstenfilms sputter deposited on polyimide substrates have been analyzed by x-ray diffraction. The influence of several deposition parameters is studied. In 200 nm thick films, the tungsten β phase is observed when oxygen incorporation is high. As the film thickness increases, a thermally activated β→α phase transition occurs and only the α phase exists in the 600 nm films. High compressive residual stresses are evidenced in both phases.