bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress and thermal expansion of boron-doped silicon membranes on silicon substrates
Authors: Berry B. S. , Pritchet W. C.
Published: July 2002

A new analysis is presented to describe the weak linear temperature dependence of the stress observed from 293 to 550 K in B-doped silicon membranes supported by silicon substrates. In contrast to a previous treatment, where consideration was given only to the existence of a differential thermal expansion coefficient Δα, the present treatment also takes into account the temperature dependence of the elastic modulus of the membrane, an effect which cannot be neglected when Δα is very small. It is now concluded that boron doping to a nominal level of 1020 atoms/cm3 increases the expansion coefficient of Si over the range 293–550 K by 1.1×10−8/K, an increment only one-half as large as that previously reported. In addition, the {100} biaxial elastic modulus of the membrane B is deduced to have a temperature coefficient (1/B0) dB/dT of −3.7×10−5/K. The value of the present analysis in avoiding other misinterpretation of the experimental results is pointed out.
Metal–oxide–semiconductor gate oxide reliability and the role of fluorine
Authors: Ma T. P.
Published: July 2002

As the metal–oxide–semiconductor (MOS) device down-scaling trend continues, the integrity and reliability of thin gate insulators have become a major concern for the development of current and future generations of integrated circuits. In this paper, some of the reliability issues concerning thin gate SiO2 and SiO2/Si interface will be briefly reviewed. Among the various methods being developed to improve the thin gate oxide reliability, a relatively simple approach involving the incorporation of fluorine will be covered in some detail. Several variations of introducing fluorine will be described, and their resulting effects on the MOS gate oxide reliability will be presented. The role of fluorine will be discussed.
Deposition and properties of diamondlike carbon films produced in microwave and radio-frequency plasma
Authors: Raveh A. , Klemberg-Sapieha J. E. , Martinu L. , Wertheimer M. R.
Published: July 2002

Hard a-C:H films were grown in a dual frequency plasma sustained simultaneously by microwave and radio-frequency power. ‘‘Optimum’’ growth conditions, namely those leading to the most pronounced sp3 structural features in the films, depend very strongly on the methane feed gas flow rate and on the argon concentration, in the case of CH4/Ar mixtures. These optimum conditions have been found to correspond to maximum values of ion flux at the growing film surface, and high concentrations of precursor species such as CH, C2, C3, and atomic hydrogen in the plasma, as revealed by optical emission spectroscopy. Films grown under optimum conditions have very high microhardness (∼50 GPa), high density (1.8 g/cm−3), and low internal stress (0.5 GPa). Addition of argon to the methane is shown to enhance the gas phase fragmentation and to raise the microhardness, but argon atoms trapped in the films’ structure increase the internal stress.
Doppler shift measurements of ion energy distribution widths in an electron cyclotron resonance/multipole hybrid reactor
Authors: Forster John , Klepper C. Chris , Berry Lee A. , Gorbatkin S. M.
Published: July 2002

An optical emission spectroscopy diagnostic was used to measure the Doppler broadening of a Cl+ emission line in a plasma generated in an electron cyclotron resonance/multipole hybrid reactor. The broadening of the emission line was found to be correlated with Langmuir probe measurements of the electron temperature. It is postulated that the Doppler broadening is related to the electron temperature through the plasma potential. Deviations to the correlation occur at high microwave powers, suggesting the existence of another type of ion broadening.
Emergence of atomic-level structural information for ordered metal–solution interfaces: Some recent contributions from in situ infrared spectroscopy and scanning tunneling microscopy
Authors: Gao Xiaoping , Chang Si-Chung , Jiang Xudong , Hamelin Antoinette , Weaver Michael J.
Published: July 2002

The utilization of infrared reflection–absorption spectroscopy (IRAS) and scanning tunneling microscopy (STM) for extracting atomic-resolution information for ordered metal–solution interfaces in a related (and relatable) fashion to metal-ultrahigh vacuum (UHV) surfaces is illustrated by means of some recent results from our laboratory. Two specific topics are addressed. The first involves the potential-dependent properties of saturated CO adlayers on low-index platinum and rhodium electrodes in aqueous and nonaqueous media. The central role of the surface potential in controlling the CO adlayer structure is discussed on the basis of in situ IRAS data, especially in comparison with the properties of corresponding metal-UHV interfaces. The application of in situ atomic-resolution STM in tandem with IRAS for elucidating real-space adsorbate structures is noted for saturated CO adlayers on Rh(111) and Rh(110) electrodes. The second topic concerns the application of in situ STM to probe potential-induced reconstruction at gold-aqueous interfaces. All three low-index gold surfaces are seen to undergo reconstruction at potentials corresponding to small (∼10–15 μC cm−2) negative electrode charges. The subtle surface relaxation observed for Au(111) is essentially identical to that observed recently by atomic-resolution STM in UHV. The (5×27) and (1×n) (n=2,3) symmetries observed for reconstructed Au(100) and (110) electrodes, respectively, are compatible with the structures deduced for the UHV systems by diffraction methods, although the STM data afford greater real-space detail.
Variable angle spectroscopic ellipsometry studies of oriented phthalocyanine films. II. Copper phthalocyanine
Authors: Debe M. K.
Published: July 2002

Recent studies obtaining the anisotropic complex dielectric spectra of oriented metal-free phthalocyanine (H2Pc) films with variable angle spectroscopic ellipsometry (VASE) have been extended to similarly oriented copper phthalocyanine (CuPc) thin films. The CuPc films were vacuum vapor deposited onto sputter deposited copper substrates. Two classes of anisotropically oriented films with thicknesses on the order of 1000 Å were produced with the molecular stacking b-axis in either a ‘‘standing’’ or surface-parallel configuration by controlling the substrate temperature. Reflection absorption infrared spectroscopy and x-ray diffraction were used to verify the different orientations. VASE data were acquired over a 4000–8000 Å wavelength range in 100 Å steps, and 45°–79° incidence angle range in 2° steps. Three-dimensional plots of the ellipsometric parameters, Δ and Ψ, versus wavelength and incidence angle have different characteristic shapes for the two classes of oriented films, similar to H2Pc, leading to significant differences in the optical constant spectral solutions obtained with an isotropic film model. Knowing the high degree of uniaxial ordering in the two film classes, approximate solutions to the parallel and perpendicular optical constants taken with respect to the crystalline b axis can be extracted from the isotropic solutions using a two-dimensional Bruggeman effective medium approximation.
Atomic layer epitaxy of silicon by dichlorosilane studied with core level spectroscopy
Authors: Yarmoff J. A. , Shuh D. K. , Durbin T. D. , Lo C. W. , Lapiano-Smith D. A. , McFeely F. R. , Himpsel F. J.
Published: July 2002

The chemisorption and reaction of dichlorosilane (SiH2Cl2) with Si(111) and Si(100) surfaces is investigated with core-level soft x-ray photoelectron spectroscopy employing synchrotron radiation, in order to ascertain the surface chemistry involved in atomic layer epitaxy (ALE). Exposures to 8 kL of SiH2Cl2 were performed as a function of sample temperature in the range from room temperature to 800 °C. At all temperatures, SiH2Cl2 chemisorbs dissociatively forming silicon monochloride surface species. The coverage of monochloride displays a maximum for exposures at ∼600 °C. Under all conditions studied, larger chlorine coverages are observed on Si(100) than on Si(111). A Si surface that was first saturated with SiH2Cl2 at 600 °C was subsequently exposed to H2 at 600 °C, and no reaction occurred. These results indicate that recent models for silicon ALE are incorrect. An alternative method for low-temperature ALE of Si is proposed, in which SiH2Cl2 is adsorbed onto Si at 600 °C and Cl is removed via reaction with atomic H.
Adsorption and decomposition of hydrides on Ge(100)
Authors: Cohen Stephen M. , Yang Yuemei L. , Rouchouze Eric , Jin Tuo , D’Evelyn Mark P.
Published: July 2002

The surface reactivity of germanium is of interest because of novel SixGe1−x heterostructure applications and the insight into semiconductor surface chemistry attainable by comparative studies on silicon and germanium. The adsorption of the inorganic hydrides H2S, H2O, and NH3 on Ge(100) was investigated by temperature-programmed desorption (TPD) for the first time. The initial sticking probability S0 for H2S exhibits at most only a minor temperature effect, remaining roughly constant at ∼0.23 within the temperature range 173 K≤T≤373 K. Adsorbed H2S decomposes upon heating into H2 and GeS, which desorb at 570 and 660 K, respectively. The initial sticking probability for H2O depends strongly on substrate temperature, dropping from 0.28 at 173 K to ∼0.02 at 273 K. Adsorbed water decomposes to yield H2 and GeO, which desorb at peak temperatures of 570 and 660 K, respectively. The peak shapes and independence of peak temperature with coverage for H2 indicate approximately first-order desorption kinetics. Adsorption of NH3 was not observed, implying S0 < 10−4. The adsorption and desorption behavior of these molecules can be understood by regarding the Ge dimer atoms as being linked by a strained double bond and examining analogous addition and elimination reactions of molecular germanium compounds.
Nucleation and growth of ultrathin Fe and Au films on Cu(100) studied by scanning tunneling microscopy
Authors: Chambliss D. D. , Wilson R. J. , Chiang S.
Published: July 2002

Cu(100) surfaces modified by depositing Au and Fe in the monolayer (ML) thickness regime are studied with the scanning tunneling microscope (STM). STM results confirm that Au deposition of 0.5 ML at 300 K creates a CuAu c(2×2) alloy monolayer, with nearly regular disruptions of structure that relieve misfit strain. The alloy forms by Au replacement of Cu atoms in the surface. Submonolayer Fe deposition at 300 K yields monolayer islands and additional features interpreted as Fe patches in the surface Cu layer. This suggests that Fe atoms replace Cu atoms in the surface. Deposition of ∼4 ML Fe yields a more homogeneous surface with height variations that suggest structural disorder in the Fe layer. Fe deposition at ∼110 K and warming to 300 K yields many monolayer and bilayer islands, with no evidence of Fe incorporation into the surface. Unusual tip behavior is also discussed which appears to yield STM sensitivity to the chemical difference between Fe and Cu areas.
Recent advances in physical vapor growth processes for ferroelectric thin films
Authors: Krupanidhi S. B.
Published: July 2002

Recent developments in the deposition of ferroelectric thin films involving physical vapor depositions are described, which include (a) multimagnetron sputter deposition, (b) multi-ion-beam reactive sputter (MIBERS) deposition, (c) pulsed excimer laser ablation, and (d) electron cyclotron resonance plasma-assisted deposition. The prevailing intrinsic low-energy ion bombardment during the growth process, common to these methods, may be used to control composition, crystallization temperature, and microstructure. A low-energy (60–75 eV) off-normal incidence ion bombardment in the MIBERS technique and a dc glow discharge in the excimer laser ablation of ferroelectric Pb(Zr,Ti)O3 thin films indicated a reduction in the phase formation/crystallization temperature, improved the electrical properties, microstructure, and the surface smoothness. Discussion is presented emphasizing the effects of low-energy ion bombardment during deposition of ferroelectric films.
Oscillatory reduction of nitric oxide with hydrogen over Pt(100)
Authors: Cobden P. D. , Siera J. , Nieuwenhuys B. E.
Published: July 2002

The reaction between NO and H2 was studied over the Pt(100) single crystal surface. Under suitably chosen parameters (partial pressures, flow rate, etc.) and under isothermal conditions, the reaction exhibited sustained temporal oscillations in reaction rate as seen by the variation in product and reactant partial pressure measured by a quadrupole mass spectrometer. The oscillations observed for the formation rates of N2 and NH3 are out of phase with those found for the formation rates of N2O. Systematic small changes in the H2 partial pressure cause the system to move from a single period oscillation via a sequence of period doublings to oscillations which were aperiodic or chaotic in nature. Analysis of this data through power spectra and correlation integrals identified it as being chaotic, and not noisy in nature, and these calculations also revealed that the minimum number of variables determining the physical properties of the system to be 3. On the basis of this and careful analysis of the different product formations, a mechanism is proposed for this oscillating system.
Surface and interface states for GaAs(100) (1×1) and (4×2)-c(8×2) reconstructions
Authors: Vitomirov I. M. , Raisanen A. D. , Finnefrock A. C. , Viturro R. E. , Chang S. , Brillson L. J. , Kirchner P. D. , Pettit G. D. , Woodall J. M.
Published: July 2002

Low energy cathodoluminescence spectroscopy measurements of GaAs(100) surfaces prepared by thermal desorption of an As passivation layer reveal deep level transitions localized at the clean surfaces and metallized interfaces. These surface and interface state features extend from 0.7 to 1.3 eV and exhibit subtle differences between the As-rich (1×1) and Ga-rich (4×2)-c(8×2) reconstructions. Both Au deposition and subsequent annealing induce additional deep level emissions which appear relatively unchanged between these two reconstructions. In contrast, Al deposition introduces new features which depend significantly upon starting surface stoichiometry and reconstruction. We discuss the formation and energies of these states in relation to reported variations in Fermi level stabilization. We conclude that surface stoichiometry and atomic bond configuration are a significant factor in formation and evolution of electrically active, deep level metal-GaAs(100) interface states.
Influence of a direct current bias on the energy of ions from an electron cyclotron resonance plasma
Authors: Reinke P. , Schelz S. , Jacob W. , Möller W.
Published: July 2002

The energy distributions of ions (IED) on the substrate in an electron cyclotron resonance discharge have been measured for methane at pressures of 5.4 × 10−2 and 1.1 × 10−1 Pa, for substrate holders with diameters ranging from 2.2 to 9.5 cm and dc-bias voltages between 0 and −120 V. The applied dc bias is fully converted into an increase of ion energy only with the smallest substrate plate, and has no effect on the ion energy for the largest diameter. For intermediate diameters, the ion energy increases with increasing pressure at constant bias. This is explained by a model taking into account the sheath and anisotropic plasma resistivity. The current density does not increase with bias. From the merely small changes in full width at half-maximum and the percentage in low energy ions with increasing dc-bias voltage and sheath thickness it can be concluded that the sheath is collisionless.
Direct current plasma discharges of fluorobromomethanes
Authors: Driscoll D. C. , Sheinson R. S.
Published: July 2002

The ion yield from dc discharges in the fluorobromomethanes CF4−xBrx (x=0 to x=3) and CF3Cl has been observed. The ion yield variation with pressure and power is presented. Results for the bromine substituted methanes, and CF3Cl have been compared to examine the effects of molecular symmetry (chemical substitution), and of the electronegativity of the halogen substituent. Input power was varied in order to observe approximate discharge energy dependance, and cell pressure was varied to explore the importance of ion molecule collisions.
Langmuir probe measurements of the electron energy distribution function in radio-frequency plasmas
Authors: Scanlan John V. , Hopkins Michael B.
Published: July 2002

Plasma parameters, including the electron energy distribution function (EEDF), have been measured in 13.56 MHz argon and nitrogen plasmas using a tuned probe. The EEDF measured over a range of pressures in argon are approximately bi-Maxwellian, whereas the nitrogen EEDF becomes highly non-Maxwellian at high gas pressures. The EEDF measurements also demonstrate that the argon radio-frequency (rf) plasma can be sustained entirely by single step ionization, whereas in the case of nitrogen, another source of ionization is necessary to account for the plasma production rate. The low pressure EEDF display an isotropic group of ionizing electrons despite the fact that their mean free paths are greater than the chamber dimension. This persistence of rf plasmas at low pressures is also discussed.
Influence of the discharge frequency (35 kHz and 13.56 MHz) on the composition of plasma enhanced chemical vapor deposition a-C:H films
Authors: Gómez-Aleixandre C. , Sánchez O. , Albella J. M.
Published: July 2002

Amorphous carbon films have been deposited by plasma enhanced chemical vapor deposition from methane and hydrogen gas mixtures excited at two different frequencies, 35 kHz and 13.56 MHz. Large differences observed in the optical emission spectra of the discharge have been attributed to changes in the main dissociative excitation processes of the CH4 molecules. The deposition rate and film composition also depend on the discharge frequency. At 35 kHz, the high concentration of atomic hydrogen during the excitation process favors the etching of the amorphous carbon and extremely thin films are obtained. However, at 13.56 MHz, the deposition rate is much higher and the films present a high polymeric content, which has been related to one of the dissociative mechanism proposed at this frequency (i.e., CH4+e→CH2+H2+e).
Interface studies between transition metals and poly(vilylidene fluoride)
Authors: Pan F.-M. , Huang J.-L. , Liaw C.-F.
Published: July 2002

The interfaces between poly(vilylidene fluoride) (PVDF) and the chromium film as well as the nickel film have been studied by x-ray photoelectron spectroscopy (XPS). Chromium carbide and fluoride were formed at the interface when chromium was vapor deposited on the PVDF film. The chromium fluorides formed on the PVDF surface could be reduced by incoming Cr vapor atoms. According to mass spectroscopy, simple hydrocarbon gas species were produced during Cr deposition. While nickel carbide was detected by XPS on the Ni deposited PVDF, no fluoride was found on the substrate. In addition to simple hydrocarbon gas species, fluorocarbon gas product was produced during Ni deposition.
Pairing and clustering of hydrogen on Si(100)2×1: Monte Carlo studies
Authors: Yang Yuemei L. , D’Evelyn Mark P.
Published: July 2002

We consider a generalization of the doubly occupied dimer model we proposed recently to explain the near first-order desorption kinetics of H2 from Si(100)2×1, incorporating effective nearest-neighbor interactions between paired hydrogen atoms on adjacent dimers. We have performed Monte Carlo simulations of the generalized model, and compare the pairing and cluster-size distributions with those observed recently by scanning tunneling microscopy (STM). The agreement is reasonable but the cluster size distributions differ in shape, which we suggest is due to the nonthermal nature of the distributions observed by STM and/or possible inadequacies in the use of nearest-neighbor interactions to represent the physics of clustering. Implications of the results for the underlying physical interactions responsible for ordering of hydrogen on Si(100) and for the desorption kinetics are discussed.
Rotationally inelastic scattering of N2 from W(110)
Authors: Hanisco Thomas F. , Kummel Andrew C.
Published: July 2002

We have measured the translational energy, rotational state population distributions, and angular momentum alignment of monoenergetic, rotationally cold N2 scattered from W(110), as a function of incident energy, incident angle, and exit angle. Translational energy and rotational state distributions indicate that N2 scattering is direct and highly rotationally inelastic. Rotational distributions are well described by Boltzmann fits at all incident energies, incident angles, and exit angles. Rotational distributions do not change with incident angle or exit angle; the distributions scale only with the total incident energy. A comparison between W(110) and Pt(111) shows that the rotational excitation of N2 scattered from W(110) is significantly larger than that N2 scattered from Pt(111). Measurements of angular momentum alignment show that molecules in low J states rotate like helicopters and molecules in high J states rotate like cartwheels for low incident energies (Ei≤0.5 eV). At higher incident energy (Ei=1.0 eV), only cartwheeling rotations are observed.
Application of a high density inductively coupled plasma reactor to polysilicon etching
Authors: Patrick Roger , Schoenborn Philippe , Toda Harry , Bose Frank
Published: July 2002

An inductively coupled radio-frequency (13.56 MHz) plasma reactor has been applied to polysilicon etching for complementary metal–oxide semiconductor (CMOS) gate fabrication. The system comprises a powered flat coil situated above an upper insulating plate in the reaction chamber. It is found, using Langmuir probe measurements, to be capable of generating a high density plasma (Ni≳1011 cm−3) at pressures of ∼5 mTorr. The intrinsic bias of the system is low and a capacitively coupled substrate bias from an additional 13.56 MHz generator allows independent control of ion energy. The system is capable of etching polysilicon at a high rate (≳3000 Å min−1) in a Cl2 discharge with good selectivity to oxide. Etch results are discussed along with damage studies based on thermal wave, minority carrier lifetime and MOS gate oxide breakdown measurements.
Real time stress measurements and elastic constant of aluminum nitride thin films on Si(111)
Authors: Meng W. J. , Sell J. A. , Perry T. A. , Eesley G. L.
Published: July 2002

This article addresses stress effects in sputter deposited aluminum nitride (AlN) thin films on Si(111). One of the elastic constants of AlN (C33) was measured directly. Real time stress measurements during growth of AlN thin films yield corroborating results for polycrystalline film growth and new results which indicate large intrinsic stresses during epitaxial growth of AlN on Si(111).
Photoelectron spectroscopic studies on interfacial reactions in Zr/2×1(100)Si and Zr/SiO2/(100)Si systems
Authors: Yamauchi T. , Kitamura H. , Wakai N. , Zaima S. , Koide Y. , Yasuda Y.
Published: July 2002

Interfacial reactions in Zr/clean-2×1(100)Si and Zr/SiO2/(100)Si systems have been studied by x-ray and ultraviolet photoelectron spectroscopy. It has been found that no silicidation reaction occurs at the Zr/2×1(100)Si interface at temperatures below 400 °C and, however, the existence of a thin SiO2 layer at the interface causes interfacial reactions even at as low as 80 °C. The silicidation in the latter system is thought to be initiated by Si atoms produced by the reduction of SiO2 due to chemically active Zr. Chemical shifts of core levels of Zr 3d5/2 and Si 2p electrons due to the silicidation are found to be +0.3 and −0.6 eV, respectively
Influence of magnetic field on the self-bias potential on a radio frequency-powered electrode in radio frequency plasma
Authors: Tsuzuki K. , Tabuchi S. , Banno T. , Kinbara A. , Nakagawa Y. , Tsukada T.
Published: July 2002

Electric self-bias potential and its distribution on the radio frequency (rf) electrode in an rf plasma have been measured using probes buried in the electrode. The potential increases almost proportionally with the net rf power (Wrf) ranging from 5 to 80 W. When the magnetic field parallel to the electrode (Wrf=26 W) is applied, the potential is reduced from −150 V (0 T) to −50 V (0.04 T) at the center of the electrode and the gradient in the potential distribution occurs along the E×B direction. This mechanism, the role of the external magnetic field, and the industrial applicability are discussed.
Sputtered atom transport in high-current gas discharges: A self-consistent computer simulation study
Authors: Urbassek Herbert M. , Sibold Dieter
Published: July 2002

It is experimentally known that particles sputtered from the cathode of high-current gas discharges heat the discharge locally in front of the cathode, reduce its density there, and induce a ‘‘sputter wind’’ in the discharge gas. As a consequence, sputtered particles are stopped less strongly in a high-current discharge, as compared to a low-current discharge. We study the coupled system of sputter current and discharge gas, using a direct simulation Monte Carlo algorithm adoped from gas kinetics, which simulates the Boltzmann equation underlying these transport processes. A cylindrical model system is studied. The effects of density reduction and discharge heating in front of the cathode and a convection wind are clearly observed. By comparing the sputtered particle flow in this simulation with that of a reference simulation in which the discharge gas is kept in its initial condition, the effects of the coupling between sputtered currents and discharge are brought out most clearly. Comparison of the gas density reduction in front of the cathode with experimental data is favorable.
CdTe oxide films grown by radio frequency sputtering utilizing argon–nitrous oxide plasma
Authors: Zapata-Navarro A. , Zapata-Torres M. , Sosa Victor , Bartolo-Perez P. , Peña J. L.
Published: July 2002

Cadmium telluride oxide films (CdTe:O) were grown by a radio frequency sputtering technique using a controlled plasma (Ar–N2O) on glass slide substrates. The films were studied by Auger electron spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction. We demonstrate that with N2O the oxidation process occurs in a narrow range of partial pressures of nitrous oxide. We find that the films are amorphous and the amount of oxygen incorporated in the films depends on the N2O partial pressure and saturates at about 55 at. % oxygen. As the amount of oxygen increases the number of Te–O and Cd–O bonds increases. The compounds formed depend on the partial pressure of the N2O and are of the form CdxTeyOz. When saturation of oxygen is obtained the compound formed is probably CdTe2O5.
Valence-band structure of PMDA-ODA polyimide studied by x-ray photoelectron spectroscopy and theoretical calculations*
Authors: Nakayama Y. , Baltzer P. , Wannberg B. , Gelius U. , Stafström S. , Lunell S.
Published: July 2002

The valence-band structure of pyromellitic dianhydride-4,4′-oxydianiline (PMDA-ODA) film was investigated experimentally and theoretically. High-resolution valence band spectra were obtained with an x-ray photoelectron spectroscopy (XPS) instrument equipped with a monochromatic high-power Al Kα x-ray source. Several new valence-band structures were observed. Electron energy loss spectra showed the presence of an inelastic peak at about 6.5 eV loss energy. A photoelectron background was synthesized from the electron energy loss spectrum by a convolution procedure. This background gave a good understanding of the valence band spectrum. Valence effective Hamiltonian and extended Hückel calculations were performed to study the XPS intensities of the valence-band structures. The intensities were approximated by utilizing the XPS intensity model with net atomic populations. The total intensities were partitioned into intensity contributions from various functional groups of the polyimide. Three energetically separated regions with dominating contributions from the imide nitrogens, the ODA carbons, and the imide oxygens, respectively, were found.
Fluorocarbon high density plasma. VI. Reactive ion etching lag model for contact hole silicon dioxide etching in an electron cyclotron resonance plasma
Authors: Joubert O. , Oehrlein G. S. , Surendra M.
Published: July 2002

Etching of high aspect ratio patterns induces reactive ion etching (RIE) lag. This effect is studied for oxide features etched in a high density plasma excited by electron cyclotron resonance using different fluorocarbon gases. A new RIE lag model is proposed which depends on the assumption that the oxide etch rate is, as on a blanket sample, strongly influenced by the deposition of fluorocarbon film on the oxide surface during the etching process.
Characterization of heated platinum filaments as a source of atomic oxygen
Authors: Smentkowski V. S. , Yates J. T.
Published: July 2002

Hot platinum filaments, for the production of atomic oxygen, have been characterized by two complementary techniques: line-of-sight gas phase analysis and surface trapping experiments using a gold substrate. It is demonstrated by both techniques that platinum is detected prior to detectable atomic oxygen production. This calls into question previous studies which have employed Pt as a thermal source of atomic oxygen for research purposes.
Growth ripples upon strained SiGe epitaxial layers on Si and misfit dislocation interactions
Authors: Cullis A. G. , Robbins D. J. , Barnett S. J. , Pidduck A. J.
Published: July 2002

Ripple arrays are formed under certain growth conditions upon the surface of epitaxial Si1−xGex on Si, and their nature is examined in detail using transmission electron microscopy, atomic force microscopy, and x-ray diffraction measurements. The driving force for ripple formation on the strained layers is the lowering of the system free energy by partial elastic strain relief due to oscillatory lattice plane distortion. We present the first direct measurement of the lattice distortion and demonstrate that this corresponds to near-complete relaxation in the ripple peaks in a direction normal to the ripple rows. The additional compressive lattice plane distortion present at ripple troughs is also estimated and is likely to promote misfit dislocation nucleation. Surface faceting can reduce the energy of the configuration, allowing troughs to deepen and minimize the dislocation nucleation barrier. The way in which the ripple strain fluctuations couple to already formed underlying misfit dislocations (often pinned bunches) is also demonstrated.
Pulsed ion beam surface analysis as a means of in situ real-time analysis of thin films during growth
Authors: Krauss A. R. , Lin Y. , Auciello O. , Lamich G. J. , Gruen D. M. , Schultz J. A. , Chang R. P. H.
Published: July 2002

Low-energy (5–15 keV) pulsed ion beam surface analysis comprises several different surface spectroscopies which possess the ability to provide a remarkably wide range of information directly relevant to the growth of single and multicomponent semiconductor, metal and metal-oxide thin films and layered structures. Ion beam methods have not however, been widely used as anin situ monitor of thin film growth because existing commercial instrumentation causes excessive film damage, physically conflicts with the deposition equipment, and requires a chamber pressure ∼10−7–10−8 Torr, i.e., much lower than that associated with most deposition processes (≥10−4 Torr). We have developed time-of-flight ion scattering and recoil spectroscopy (TOF-SARS) as a nondestructive, insitu, real-time probe of thin film composition and structure which does not physically interfere with the deposition process. Several TOF-SARS implementations are exceptionally surface specific, yet in a properly designed system can yield high-resolution data at ambient pressures well in excess of 10 mTorr (4–6 orders of magnitude higher than conventional surface analytic methods). Because of the exceptional surface specificity of these methods, TOF-SARS is ideally suited as a means of studying ultrathin layers and atomically abrupt interfaces. TOF-SARS instrumentation designed specifically for use as an in situ, real-time monitor of growth processes for single and multicomponent thin films and layered structures is described here. Representative data are shown for in situ analysis of Pb and Zr layers at room temperature and high vacuum, as well as under conditions appropriate to the growth of Pb(ZrxTi1−x)O3 (PZT) perovskite films on MgO and RuO2 substrates.
Intelligent model-based control system employing in situ ellipsometry
Authors: Butler S. W. , Stefani J. , Sullivan M. , Maung S. , Barna G. , Henck S.
Published: July 2002

An intelligent model-based control system provides a framework for the efficient application of in situ sensors to semiconductor manufacturing. This article discusses the components of such a system. The specific example presented in this article is a system utilizing in situ ellipsometry developed for a polysilicon gate etch. The ellipsometer was used for robust endpointing, process modeling, fault detection, and run-to-run supervisory control. The methodology for each sensor application is presented. The coordination of the various applications is also discussed and implementation issues are covered. The goal of the controller for polysilicon gate etch is to achieve a target mean etch rate, while maintaining a spatially uniform etch. This process suffers from machine aging, which degrades the etch rate and final film uniformity. Experimental results demonstrating that the controller compensates for process drift are shown. Implementation of this system resulted in a 36% decrease in standard deviation from the target for the mean etch rate. All of the wafers processed with feedback control met the specifications on nonuniformity, while some of the wafers processed without control did not. In addition, the data indicated that controlling the etch rate may improve the control and uniformity of the linewidth change.
Postdeposition growth of a uniquely nanostructured organic film by vacuum annealing
Authors: Debe M. K. , Poirier R. J.
Published: July 2002

The organic red pigment N,N-di(3,5-xylyl)perylene-3,4:9,10bis(dicarboximide) is easily vacuum deposited at ambient substrate temperatures to form ordinary looking smooth films. When subsequently annealed in vacuo between ∼160 and 220 °C, an initially 1000 Å uniformly thick film transforms to an extremely dense, random array of discrete, crystalline whiskers, uniformly oriented with their long axes normal to the substrate. Whisker growth occurs at zero supersaturation ratio (no incident flux) and all film material is conserved. Whisker cross sectional dimensions are ∼27×55 nm, lengths 1–1.5 μm, and areal number densities ∼50 per square micron. The high-aspect-ratio whiskers grow purely by surface diffusion to minimum energy binding sites believed to be emergent screw dislocations on the whisker tips, while the uniform cross sectional shapes reflect the ratio of surface free energies of the bounding crystal faces. The transformation has been followed in situ with reflection absorption IR spectroscopy as a function of time and temperature to obtain a dimensionless growth parameter. The surface self-diffusion coefficient and surface entropy to free energy ratio are extracted. The pigment whiskers are readily sputter or vapor-coated to provide conformally coated nanostructure-sized features with metal and semiconductor properties. Vapor coating and annealing of the original pigment films can be done reproducibly in large areas and offer a novel alternative approach to plasma etching and photolithography for producing nanostructured surfaces with new properties.
Characterization of silicon surface microroughness and tunneling transport through ultrathin gate oxide
Authors: Hirose M. , Hiroshima M. , Yasaka T. , Miyazaki S.
Published: July 2002

The surface morphology of chemically cleaned Si(100) surfaces has been studied by Fourier-transform infrared–attenuated total reflection (ATR) and atomic force microscopy (AFM). It is shown that the final cleaning in 0.1%HF+1%H2O2 after modified SC-1 clean yields a sharp SiH2 vibrational peak with weak SiH3 and SiH absorption bands while 4.5%HF treatment gives the twin peaks consisting of SiH2 and SiH3 absorptions. In contrast to this the AFM images exhibit no significant changes for the surfaces with significantly different ATR spectra. Quantitative analysis of the measured tunneling current for metal–oxide–semiconductor diodes fabricated on (100) surfaces with different surface morphologies has shown that the observed current is well fitted to the theoretically predicted characteristics.
Influence of ion mass and ion energy on microstructure of ion assisted deposited zinc selenide thin films
Authors: Caneve L. , Scaglione S. , Flori D. , Martelli S.
Published: July 2002

Zinc selenide thin films have been deposited by an ion beam assisted evaporation system in order to investigate the influence of some deposition parameters, with particular interest on incident ions energy, on film microstructure by means of x-ray diffraction in conventional Bragg–Brentano reflection geometry. Two different ion kinds (Ar and Xe) have been employed during the deposition process in order to analyze the effect of the ion mass on the microstructure of the growing thin film. The correlation of the microstructure and some mechanical properties of films deposited with different parameters has been analyzed. Moreover, thin films composition has been analyzed by Rutherford backscattering technique and the correlation with the energy ions is reported.
Expanded-range, sealed parts leak testing technology for helium mass spectrometer leak detection
Authors: Mahoney D. G.
Published: July 2002

Small, hermetically sealed objects are often leak tested after subjecting the finished device to an environment of tracer gas under high pressure. Parts with very large leaks are often missed during testing because of very fast signal decay, necessitating employment of an auxiliary gross leak detection technique, such as one which discriminates normal and abnormal pressure decay during evacuation. Such techniques require careful consideration of variables, including the presence of water vapor in the system, the condition of the mechanical vacuum pump, and electronics response time lags, and are not always precisely predictable in operating environments. However, if a large leak discrimination system is designed to operate at test pressures close to atmospheric, and if a gas expansion method is applied comparing the volume of the test object to a fixed volume, such variables are eliminated, yielding a highly reliable and rapid large leak discrimination method. Combining such a method within a helium mass spectrometer leak detector (HMSLD) results in a system capable of detecting leaks from very large leaks down to the limits of HMSLD testing.
Si/SiO2 interface studies by spectroscopic immersion ellipsometry and atomic force microscopy
Authors: Liu Q. , Wall J. F. , Irene E. A.
Published: July 2002

The dependence of the Si/SiO2 interface characteristics on the thickness and oxidation temperature for SiO2 films grown on different Si orientations was studied by spectroscopic immersion ellipsometry (SIE) and atomic force microscopy (AFM). Essentially, SIE uses liquids that match the refractive index of the films, thereby optically removing the films and consequently increasing the sensitivity to the interface. We show that as the thickness of the thermally grown SiO2 overlayer increases, the thickness of the suboxide layer at the interface also increases, and the average radius of the crystalline silicon protrusions (roughness) at the interface decreases for the three different Si orientations (100), (110), and (111), and two different oxidation temperatures (800 and 1000 °C) studied. The dependence of the interface roughness on the thickness of the SiO2 overlayer was confirmed by AFM. The results include unintentionally and intentionally roughened Si samples and are shown to be consistent with the commonly accepted Si oxidation model.
Thermal decomposition of diethylgermane on Si(100)-(2×1)
Authors: Du Wei , Keeling Lori A. , Greenlief C. Michael
Published: July 2002

The adsorption and decomposition of diethylgermane, GeH2(C2H5)2 (or GeH2Et2), on the Si(100)-(2×1) surface is investigated with the intent of elucidating the surface processes leading to the deposition of epitaxial Ge thin films from gaseous Ge-containing sources. Low GeH2Et2 exposures to Si(100) at 110 K result in dissociative adsorption of the molecule with both ethyl groups transferring to the silicon surface. Heating of the sample to higher temperatures results in the decomposition of the adsorbed ethyl groups. GeH2 is the other adsorption product which also decomposes at higher temperatures to atomic Ge. The final reaction products are H2, C2H4, and atomic Ge. The ethylene produced is consistent with a β-hydride elimination reaction.
Adsorption of sulfur and 1,3-butanediol on silver thin films using atomic resolution-reduced-temperature scanning tunneling microscopy
Authors: Chen X. X. , Frank E. R. , Hamers R. J.
Published: July 2002

Scanning tunneling microscopy has been used to study the adsorption of atomic sulfur and 1,3-butanediol on silver films formed by evaporation onto Si(111)-(7×7) substrates. Thin silver films only a few monolayers thick grown on Si(111) show a √3×√3R30° reconstruction, while thicker films show a hexagonal close-packed, unreconstructed Ag(111) surface. At high deposition rates, screw dislocations in the films are commonly observed. Atomic sulfur adsorbed on thin Ag films showing a √3×√3R30° reconstruction appears as a protrusion when filled states are imaged and as a depression in empty state images. The sulfur atoms bond almost exclusively at lattice defects which appear to be vacancy clusters. 1,3-butanediol appears as a large depression at all biases, indicating that the adsorbate electrostatically repels charge and lowers the metal density of states around the adsorption site.
X-ray photoelectron spectroscopy investigation of interfacial interactions in the Cr/BPDA-PDA and Ti/BPDA-PDA systems
Authors: Chenite A. , Selmani A. , Yelon A.
Published: July 2002

Interfacial interactions of evaporated chromium and titanium with BPDA-PDA polyimide surfaces have been studied using x-ray photoelectron spectroscopy. The results reveal two stages in the metallization process. At low coverage, the behavior is dominated by the reaction of metal with the C=O function, as in the case of PMDA-ODA polyimide. The nitrogen atoms are slightly perturbed following the C=O attack. At relatively higher coverage, additional interfacial reactions occur, involving the formation of chromium and titanium carbides and nitrides. The results indicate clearly that the chemical interactions of Cr or Ti at BPDA-PDA and PMDA-ODA surfaces are quite similar. Thus, the diamine portions, PDA and ODA, can affect the adhesion strength, probably by modifying the polyimide chain conformation. In PMDA-ODA, the polyimide chain is flexible and can rotate around the ether oxygen, while in the BPDA-PDA the conjugation effect is more important and makes the macromolecules more rigid. This is most probably the way by which PDA and ODA segments can influence the adhesion performance of polyimide.
Nanometer p–n junction formation and characterization
Authors: Lau W. M. , Huang L. J. , Chang W. H. , Bello I. , Abraham T. , King M.
Published: July 2002

The fabrication of p–n junctions in silicon with junction depths of a few nanometers and the determination of the potential distribution and junction depth of such a specimen with a depth resolution of better than 0.5 nm were performed. The ultrashallow p–n junctions were formed by bombarding hydrogen-passivated n-Si(100) with BF2+ of less than 500 eV. After being annealed at 500 °C in vacuum for an hour, the sample surfaces were treated with a HF solution for the reduction of surface states in the band gap of silicon prior to junction characterization. With hydrogen passivation, the separation between the Fermi level and the valence band maximum of the semiconductor surface, EFs, an energy which is governed by the doing type and net carrier concentration, was measured with x-ray photoelectron spectroscopy. The sample was then subjected to ozone oxidation at room temperature for 20 min, a procedure which reproducibly consumes 0.5 nm of silicon. The oxide was then removed by a HF solution to reveal a new hydrogen-passivated surface for the second-cycle EFsmeasurement. This process was repeated until the measurement of EFs versus depth was completed for the profiling of the ultrashallow junction. With a mathematical space-charge calculation, the carrier-concentration–depth profile, the potential-distribution–depth profile, and the junction depth can then be determined by the measured EFs–depth relationship. At a bombardment energy of 150 eV and a dose of less than 1×1016/cm2, the junction depth was found to be less than 2 nm.
Study of ion mixing during Auger electron spectroscopy depth profiling of Ge–Si multilayer system
Authors: Menyhard M. , Barna A. , Biersack J. P.
Published: July 2002

Auger electron spectroscopy depth profiling was carried out on a Ge–Si multilayer structure using a rotated specimen and grazing incidence angle. Under these sputtering conditions the depth resolution is determined mainly by atomic mixing. The dependence of the experimentally measured depth resolution on incidence angle and energy was compared with the simulation results from a trim code. It was found that the trends of the dependencies were the same, but the trim absolute values were different.
Strain compensated heterostructures in the Si1−x−yGexCy ternary system
Authors: Regolini J. L. , Bodnar S. , Oberlin J. C. , Ferrieu F. , Gauneau M. , Lambert B. , Boucaud P.
Published: July 2002

Si1−x−yGexCy pseudomorphic heterostructures have been grown on Si(100) substrates using a rapid thermal chemical vapor deposition reactor. Due to the lattice parameters of Si, Ge, and C(diamond), the strained Si1−xGex layers can be strain compensated by the addition of substitutional C. The epitaxial layers were fabricated at reduced pressure and the reactive gases (silane, dichlorosilane, germane, and organometallic C–Si compound) were diluted in purified hydrogen. The growth temperatures were 650 and 550 °C, in order to have a reasonable growth rate and not form the stable SiC phase. The epitaxial layers, up to 4000 Å in thickness and x=20%, were compensated by up to 1% of substitutional C as measured by infrared spectroscopy at 605 cm−1. The lattice parameters were measured by x-ray diffraction using the [004] and [224] substrate difraction peaks to directly obtain the strain parameters. Partial strain compensation was observed in layers thicker than the critical thickness for Si1−xGex. These results are also compared to those of photoluminescence spectroscopy, where the observed misfit dislocation related bands (D1 and D2) are minimized in compensated samples.