By Topic

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

Issue 6 • Date Nov 1988

Filter Results

Displaying Results 1 - 25 of 138
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (2128 KB)  
    Freely Available from IEEE
  • Reactive ion beam etching of polyimide thin films

    Page(s): 1621 - 1625
    Save to Project icon | PDF file iconPDF (813 KB)  

    Reactive ion beam etching of polyimide thin films was investigated using x‐ray photoelectron spectroscopy (XPS) and etch rate measurements. The etching mechanism and the near surface damage produced in polyimide by exposure to argon and oxygen ion beams were compared. The etch rate of polyimide by oxygen ions was studied as a function of ion current density and neutral oxygen molecular flux, and the results were found to match a model for the contribution of neutral fluxes to the etch process. Ion beam etching with inert argon ions was found to produce a graphitelike layer on polyimide. Reactive ion beam etching with oxygen ions resulted in much faster etching than for argon ions, and did not produce a graphitized layer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High‐rate ion etching of GaAs and Si at low ion energy by using an electron beam excited plasma system

    Page(s): 1626 - 1631
    Save to Project icon | PDF file iconPDF (953 KB)  

    By using a newly developed electron beam excited plasma (EBEP) system, etching characteristics of GaAs and Si in an ion energy range of 5 to 100 eV were investigated. Anisotropic etching profiles with high aspect ratios were obtained by both Ar ion beam etching (IBE) and Cl2 reactive ion beam etching (RIBE). Etching rates of 1.2 μm/min for GaAs and 0.5 μm/min for Si were demonstrated for the first time by Cl2 RIBE at ultralow ion acceleration voltage of 5 V. Selective ratios of etching rates for Si/SiO2 and GaAs/SiO2 are ∼33 and 80, respectively. Electrical and optical measurements on the etched samples indicated that damage degree introduced by the low‐energy ions is negligible. Therefore, the EBEP system cannot only provide high etching rate because of its high ion current but also realize damageless ion etching due to its low ion energy. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reaction probability for the spontaneous etching of silicon by CF3 free radicals

    Page(s): 1632 - 1640
    Save to Project icon | PDF file iconPDF (1618 KB)  

    The spontaneous thermal etching of silicon by CF3 free radicals has been studied in a very‐low‐pressure photolysis reactor. The radical is produced by infrared multiphoton dissociation of either hexafluoracetone or CF3 I, and is allowed to react with a temperature‐controlled silicon sample (560–745 K). Mass spectrometry is used to measure the extent of dissociation of the precursor gas and the formation of product molecules, C2 F6 and SiF4 . The etch rate of the silicon is determined from the SiF4 production. Resonance‐enhanced multiphoton ionization of CF3 is used to determine the density and time history of the radical in the reactor. The measurements of the etch rate and CF3 density are combined to derive the reaction probability. CF3 etches silicon much more slowly than F atoms and at a rate comparable to molecular F2 . A carbon layer, that is deposited on the silicon by the radicals, inhibits, but does not stop, further etching. Experiments on the etching of silicon by F2 were performed both to validate the reactor design and to prepare the silicon surface for the CF3 studies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Selective dry etching of GaAs over AlGaAs in SF6/SiCl4 mixtures

    Page(s): 1641 - 1644
    Save to Project icon | PDF file iconPDF (576 KB)  

    Reactive ion etching of GaAs with high selectivity over Al0.29Ga0.71As in SF6/SiCl4 mixtures was studied. Selectivity, surface morphology, and anisotropy were investigated over a wide range of pressures (15–100 mTorr), dc bias values (-20 to -300 V), and SF6‐to‐SiCl4 ratios (0–0.5). Higher pressures, lower dc biases, and higher SF6/SiCl4 ratios increase the GaAs‐to‐AlGaAs selectivity. Electron spectroscopy for chemical analysis indicates that the formation of nonvolatile aluminum fluoride on AlGaAs is responsible for the selective etch process. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The role of aluminum in selective reactive ion etching of GaAs on AlGaAs

    Page(s): 1645 - 1649
    Save to Project icon | PDF file iconPDF (830 KB)  

    We have studied the role of aluminum in the formation of an etch barrier at the GaAs/ Alx Ga1-x As interface during reactive ion etching in CCl2 F2 plasma. The minimum Alx Ga1-x As thickness needed to form the barrier is Al mole fraction dependent and was determined with etching experiments monitored by optical emission spectroscopy. Effective Alx Ga1-x As layers for forming an etch barrier are 275 Å for x=0.02, 22 Å for x=0.10, 15 Å for x=0.15, 12 Å for x=0.20, and 9 Å for x=0.30. For all Al mole fractions except x=0.02, these thicknesses correspond to a sheet dose equivalent to 3/4 of a monolayer of Al in the original Alx Ga1-x As layer. Barrier layers for x=0.02, 0.10, 0.25, and 0.30 were examined without air exposure by angle‐dependent x‐ray photoelectron spectroscopy. For samples that are not overetched, the surface is covered with ∼20 Å of AlF3 intermixed with a gallium halide containing chlorine and fluorine and is depleted of arsenic. For substantially overetched barriers, a 30 Å layer is formed with gallium halide present at the surface, AlF3 found farther in, and arsenic depletion throughout the barrier. During extreme overetch, barrier layers on the order of tens of Å in thickness were not etched away and yet did not completely prevent very slow etching of underlying GaAs. Barrier layers on the order of 60 Å in thickness did prevent etching of underlying GaAs. Collectively the data suggest that the role of Al is formation of AlF3 exclusively and that only this compound is responsible for stopping the GaAs etch. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Photoemission investigation of Ge and SiGe alloy surfaces after reactive ion etching

    Page(s): 1650 - 1656
    Save to Project icon | PDF file iconPDF (1224 KB)  

    Photoemission spectra were obtained from Ge surfaces after reactive ion etching with CF4 and CF4/H2 mixtures. These measurements indicate a surface layer of fluorinated Ge species as well as adsorbed carbon and CFx species. The shifted intensity in the Ge(2p3/2) core level suggests a layer of about 1 to 2 layers of GeFx, with x∼2–3. The accumulation of CFx overlayer increases with increasing H2 to CF4, but comparisons with Si etched under identical conditions indicate that there is less steady‐state film deposition of Ge during reactive ion etching than on Si. Thus, an increased thickness of carbonaceous overlayer on Ge compared to Si is unlikely to be the explanation for the observed drop in the selectivity toward etching Ge over Si with increasing hydrogen addition. Reactive ion etching of a Si35Ge65 alloy was also investigated. Here, photoemission indicated a surface layer of GeFx similar to that found on pure Ge, but little evidence of SiFx species. The composition of the surface is enriched in Ge for about 3–5 layers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High‐throughput and fully automated system for molecular‐beam epitaxy

    Page(s): 1657 - 1661
    Save to Project icon | PDF file iconPDF (840 KB)  

    A new high‐throughput and fully automated system for molecular‐beam epitaxy was developed by employing multiple substrate mount pallets and automatic pallet transfer mechanisms. The geometrical configuration between pallet and effusion cells was optimized to achieve the uniformity of thickness and carrier concentration of epitaxial layer better than ±2% within a pallet. The throughput was more than 70 2‐in. wafers per day for the growth of AlGaAs/GaAs two‐dimensional electron gas structure. In a typical two‐dimensional electron gas structure with a 6‐nm spacer layer, the variation of sheet electron mobility closed in 7.5 to 10×104 cm2 /V s at 77 K over growth run to run. By improving the heater structure of the Ga effusion cell, the Ga‐related oval defect density was found to be reduced ≪1 cm -2. The total surface defect density was reduced to ≪50 cm-2 by preventing the particulate contamination on the growth surface. Moreover, unintentionally doped GaAs layer was dominated by a donor, whose concentration was lower than 1×1014 cm-3, and electron mobility was 145 000 cm2 /V s at 77 K. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Barrier height modification of metal/germanium Schottky diodes

    Page(s): 1662 - 1666
    Save to Project icon | PDF file iconPDF (920 KB)  

    Germanium is experiencing a resurgence of interest due to superior intrinsic properties and recently overcome technological limitations. This paper addresses the problem of Schottky barrier height control. The Fermi level of metal/Ge contacts is pinned at between 0.54 and 0.61 eV below the conduction‐band edge, independent of the contacting metallization. We compare the modulation of effective barrier height by means of shallow ion implantation, epitaxial growth, and diffusion from a doped level to create a thin, highly doped interfacial region. Lowering of n‐type contacts from 0.54 to 0.4 eV, at room temperature, and enhancement of p‐type contacts from 0.09 to 0.23 eV, at 77 K, have been achieved. Experimental results are compared to computer model calculations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Baffle‐free refractory dimer arsenic source for molecular‐beam epitaxy

    Page(s): 1667 - 1670
    Save to Project icon | PDF file iconPDF (623 KB)  

    A refractory, two‐zone, large‐capacity, baffle‐free arsenic cracking source for molecular‐beam epitaxy is presented. The new features of this design include the use of a molybdenum tube to provide efficient cracking, a horizontal sublimator at a right‐angle geometry to the cracking section, a baffle‐free design, and the use of expanded tantalum heating filaments. High‐efficiency cracking is obtained at cracking tube temperatures between 750 and 1050 °C. Bulk GaAs and GaAs/AlGaAs heterostructures grown using this source exhibit good electrical and optical properties, with clear improvements in electrical behavior when compared to an As4 source. We believe this source design can be easily applied to other column V materials such as phosphorus and antimony. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Correct substrate temperature monitoring with infrared optical pyrometer for molecular‐beam epitaxy of III–V semiconductors

    Page(s): 1671 - 1677
    Save to Project icon | PDF file iconPDF (1010 KB)  

    Correct GaAs and InP substrate temperatures are monitored with an infrared optical pyrometer. The temperature calibration for the pyrometer is carried out with the help of an emissivity change, produced by an eutectic reaction, in the Al deposited Si substrate. It is found that large apparent temperature differences exist between n+‐ (or p+‐) and semi‐insulating GaAs and InP substrates when constant emissivity is assumed. The temperature difference is ∼60 °C at 500 °C for InP, and 10–30 °C for GaAs. The temperature differences are found to increase with increasing substrate temperature. A model calculation is given for substrate temperature monitoring with an infrared optical pyrometer. The apparent temperature difference is attributed to the presence of optical absorption mechanisms in an n+‐ (and p+‐) substrate and its absence in a semi‐insulating substrate. The limiting temperature of congruent evaporation and the native oxide evaporation temperature for GaAs are measured with an accurately calibrated infrared optical pyrometer. They are found to be 612±10 °C and ∼585 °C, respectively. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization and optimization of low‐pressure chemical vapor deposited tungsten silicide using screening and response surface experimental designs

    Page(s): 1678 - 1687
    Save to Project icon | PDF file iconPDF (1420 KB)  

    Low‐pressure chemical vapor deposited WSiX has been characterized and optimized through the use of screening and modeling experimental designs. In the screening study, the effects of temperature, pressure, gas flow rates, and a predeposition treatment were determined for a list of properties which included deposition rate, resistivity, stress, stoichiometry, oxidation rate, particle generation, and resistance to chemical attack. Over the process domain covered, temperature, WF6 flow rate, and SiH4 flow rate were found to affect deposition rate, resistivity, film stress, and stoichiometry while stoichiometry was also affected by pressure. WSiX films produced in the screening study ranged in stoichiometry from X=2.1 to 3.0. The oxidation rate of these samples was found to be insensitive to deposition conditions and unrelated to the as‐deposited stoichiometry. As‐deposited and annealed film stress were found to decrease linearly with increasing silicon content of the as‐deposited films. Similarly, the as‐deposited and postannealed resistivity of WSiX films were found to be a function of the initial stoichiometry. Manufacturability related properties such as particle generation, chemical resistance, and uniformity measures involving sheet resistance, resistivity, and film thickness were found to be largely insensitive to the process factors studied. Response surface models were developed for deposition rate, annealed resistivity, annealed stress, and stoichiometry and were used to guide the final process optimization. The optimized process window was relatively large and yielded WSiX films with an annealed (950 °C, 30 min) resistivity of ∼75 μΩ cm, an as‐deposited Si/W atom ratio of ∼2.5, annealed tensile stress of ∼1.2×1010 dyne/cm2, and deposition rates of 9 - - to 10.5 Å/s. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surface science studies of semiconductor growth processes

    Page(s): 1688 - 1693
    Save to Project icon | PDF file iconPDF (807 KB)  

    A new approach to the study of semiconductor growth mechanisms is described which utilizes surface science and related photon‐based techniques. It is possible to study growth processes over the pressure range 5×10-11 to 103 mbar through the use of an isolatable atmospheric pressure reactor described briefly. As an illustration of the potential of the surface science approach, the effectiveness of the reducing hydrogen atmosphere employed in the pregrowth bake of a GaAs (100) metal‐organic vapor phase epitaxy (MOVPE) substrate in removing surface carbon and oxygen is determined using Auger electron spectroscopy. It is shown that at a pressure of 0.5 mbar of H2, temperatures as low as 600 K are sufficient to remove the surface carbon and oxygen contamination present on the substrate following wet chemical etching and heating in ultrahigh vacuum. This result implies that the conventional MOVPE sample bake at high temperatures (≫850 K), in H2 and AsH3 is not necessary to produce clean substrates. Following the H2 treatment the GaAs(100) surface gives rise to a (1×1) low‐energy electron diffraction pattern suggesting that it has been stabilized towards reconstruction via hydrogen chemisorption. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Projection patterned Si doping of GaAs in ambient SiH4 gas by a KrF excimer laser

    Page(s): 1694 - 1697
    Save to Project icon | PDF file iconPDF (591 KB)  

    Potential application of a projection system with reduction optics to the patterned doping process has been demonstrated. A KrF excimer laser beam is projected on GaAs substrates enclosed in a SiH4 gas ambient cell to achieve the Si doping with a field size of 5×5 mm2. At a laser fluence of 380 mJ/cm2, the n‐type conduction layer with a surface carrier density of 2.27×1014 cm-2 in the semi‐insulating GaAs substrate and with an activation efficiency of ∼81% can be obtained. The minimum linewidth of 2.5 μm is discussed together with temperature profiles calculated by transient heat conduction in the substrate. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Absorption properties of the bottom novolac layer in multilayer resist systems

    Page(s): 1698 - 1701
    Save to Project icon | PDF file iconPDF (562 KB)  

    A novolac resin suitable for the bottom planarizing layer in multilayer resist systems is discussed from the standpoint of exposure wavelength absorption. Absorption by the bottom planarizing layer is crucial to reduce the reflected light from the resist–substrate interface. It was clarified that the absorption of phenol novolac resin was higher than that of the cresol novolac resin under the same baking conditions. From infrared and nuclear magnetic resonance analysis, it was found that carbonyl structures were formed in the novolac resin after baking. In addition, cross‐linking was found to occur at the methylene bridges in the phenol novolac resins. These factors seem to cause the absorption maxima to shift to a longer wavelength. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Properties of WSix using dichlorosilane in a single‐wafer system

    Page(s): 1707 - 1713
    Save to Project icon | PDF file iconPDF (931 KB)  

    Chemical vapor deposition of tungsten silicide (WSix) from WF6 and SiH2Cl2 [JB Price, S. Wu, Y.Chow, and J. Mendonca, Semicon West (1986)] at higher deposition temperatures (450–650 °C) than the conventional WF6 and SiH4 (250–400 °C) process has been characterized using a plasma enhanced, single‐wafer, cold‐wall, radiantly heated system with temperature control utilizing a thermocouple in contact with the backside of the wafer. Film properties such as silicon to tungsten ratio, fluorine and chlorine concentration, resistivity, and film stress were studied as a function of substrate temperature, reactant composition, and flow rates. The film composition was measured by Rutherford backscattering spectrometry. The silicon to tungsten ratio is a function of deposition temperature at a fixed flow (x varying from 2.0–2.8 through the temperature range of 450–650 °C). The as‐deposited resistivity is also a strong function of deposition temperature. The chlorine and fluorine distributions in the WSix film were measured using secondary ion mass spectrometry. The fluorine concentration was found to be much lower than levels reported by conventional WF6/SiH4 chemistry with as‐deposited values of 9×1015 to 3×1018/cm3 compared to 1.3×1020 cm3 by M. Fukumoto and T. Ohzone [Appl. Phys. Lett. 50, 894 (1987)]. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study on oxygen behavior during Ti/Si and Ti/SiO2 interactions

    Page(s): 1714 - 1720
    Save to Project icon | PDF file iconPDF (825 KB)  

    For practical titanium silicide device application the oxygen behavior in the solid phase interaction is important to study. The Ti/Si and Ti/SiO2 interaction by the NH3 plasma assisted thermal annealing and oxidation of Ti/SiO2 and TiSi2/Si in a wet oxygen ambient were investigated by Auger electron analysis. The characteristic Auger spectral line shapes of Ti, O, and Si and their changes in compounds were measured. The experiment clearly demonstrated the oxygen snowplow effect during TiSi2 and TiN growth, and a stable SiO2 can be grown on TiSi2/Si directly or through a layer of TiO2. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Tungsten chemical vapor deposition characteristics using SiH4 in a single wafer system

    Page(s): 1721 - 1727
    Save to Project icon | PDF file iconPDF (1082 KB)  

    Several workers have recently begun using silane as a high‐rate, low‐temperature alternative to hydrogen for the reduction of WF6 in the chemical vapor deposition of W. The deposition and film characteristics of both selective and blanket W using this new chemistry are explored in a radiantly heated single wafer system using closed‐loop temperature control with a thermocouple in direct contact with the backside of the wafer. Selective W deposition rates of up to 1.5 μm/min were measured over the temperature range 250–550 °C with blanket W rates typically 2–5× lower. Resistivity is in the 10–15 μΩ cm range at 300 °C for SiH4/WF6 ratios of 0.2 to 1.0, while above 400 °C the range is 7.5–8.5 μΩ cm. Si content in the W films is quite low at 1016 to 1017 atoms/cm3. Adhesion to silicon is excellent at temperatures of 350 °C and above. Selective W using SiH4 reduction for doped silicon contact fill shows none of the consumption or encroachment problems common to H2 reduction, although selectivity is more sensitive. Contact resistance for p+ and n+ silicon contacts are comparable to aluminum controls and to previously published data. Blanket deposition into narrow geometries gives ≥90% step coverage and without keyholes in the 250–450 °C deposition temperature range. For low‐SiH4 flows, deposition at 500 °C causes small keyholes, while at 550 °C even larger keyholes result. At higher SiH4 flows, keyholes are typically not seen from 250 to 550 °C. The SiH4‐reduced films are much smoother as indicated by reflectivities that are 2–4×higher t- - han for the H2‐reduced films. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Formation and properties of rapid thermally annealed TiSi2 on lightly doped and heavily implanted silicon

    Page(s): 1728 - 1733
    Save to Project icon | PDF file iconPDF (1060 KB)  

    Detailed material and electrical characteristics of rapid thermally annealed (RTA) TiSi2 on doped silicon are presented using transmission electron microscopy, Rutherford backscattering spectrometry, secondary ion mass spectrometry (SIMS), Auger analysis, and four‐point probe measurements. TiSi2 films with varying sheet resistances were formed on lightly doped and heavily arsenic and phosphorus implanted 〈100〉 silicon by rf sputtering titanium and forming the silicide using two‐step flash anneals at different temperatures. It is shown that the silicide sheet resistance is a sensitive function of the silicon surface condition prior to titanium sputtering; in particular, silicide films formed on heavily implanted silicon had significantly higher sheet resistance compared to films formed under identical conditions on lightly doped prime silicon. The higher silicide sheet resistance resulted because of the surface damage created during arsenic and phosphorus implantation and higher silicon dopant concentration. The RTA silicide films showed excellent film properties across 4‐in.‐diam wafers with good thickness uniformity and minimal sheet resistance variations compared to furnace annealed samples. Detailed SIMS and Auger analyses showed minimal film contamination and negligible dopant redistribution for RTA silicided wafers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • TiSi2 strap formation by Ti–amorphous‐Si reaction

    Page(s): 1734 - 1739
    Save to Project icon | PDF file iconPDF (980 KB)  

    This report describes the formation of a TiSi2 strap in combination with the self‐aligned titanium silicide (salicide) technology. The TiSi2 strap is formed by reaction of amorphous silicon (a‐Si) with the underlying Ti layer. It was determined that sputter deposition of the Ti and a‐Si had to be done in one deposition cycle, otherwise interface contamination would prevent the Ti–a‐Si reaction and give rise to extensive silicon diffusion from the active areas. Since TiSi2 straps are formed over diffusion areas as well as over oxide surfaces, the influence of the substrate on the Ti/a‐Si reaction was determined. It was found that for straps deposited on oxide substrate the properties of the silicide layer formed were determined by the Ti/a‐Si atomic ratio. A titanium‐rich strap resulted in a high‐resistivity silicide layer due to TiSi compound formation. Stoichiometric straps formed low‐resistivity TiSi2 layers with a thin‐TiN top layer and silicon‐rich straps also resulted in a low‐resistivity TiSi2 layer but with a silicon enrichment at the surface. On a mono‐Si substrate no influence of the sputtered Ti/a‐Si atomic ratio could be found. Only low‐resistivity TiSi2 layers were formed. In case of silicon‐rich Ti/a‐Si ratio the excess silicon disappears from the layer and regrows onto the Si substrate. The roughness of TiSi2 straps, mainly observed for stoichiometric or silicon‐rich straps on oxide substrates, was found to be related to the presence of argon (and probably hydrogen) incorporated in the layer during sputter deposition. Special attention was paid to strap formation at oxide/diffusion area edges. Possible void formation by local silicon consumption could not be detected. Strap/TiSi2 salicide transitions are also very sm- - ooth and showed no substrate defects. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Selectively silicided vertical power double‐diffused metal–oxide semiconductor field effect transistors for high‐frequency power switching applications

    Page(s): 1740 - 1745
    Save to Project icon | PDF file iconPDF (1163 KB)  

    A new power field effect transistor (FET) structure with selectively silicided gate and source regions is described. This structure simultaneously lowers the gate sheet resistance and source contact resistance. Vertical power double‐diffused metal‐oxide semiconductor field effect transistors fabricated using this technology have a specific on‐resistance of 0.53 mΩ cm2 for devices capable of blocking 50 V in the off‐state. Devices with cell density as high as 4 million cells/in.2 and die size as large as 200×220 mil have been successfully fabricated with excellent gate yield. These results represent the best ever reported forward conductivities for any type of power FET in the 50‐V reverse blocking range. Comparison of selectively silicided power FET’s with state of the art commercial nonsilicided FET’s indicates that the former have an order‐of‐magnitude lower gate sheet resistance, 8× smaller on‐resistance, and 2× smaller input capacitance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The morphologies and characteristics of reactively formed TaSi2 films

    Page(s): 1746 - 1748
    Save to Project icon | PDF file iconPDF (479 KB)  

    Morphologies and characteristics of the surface and interface of TaSi2/Si and TaSi2/poly‐Si structures reactively formed by furnace annealing and rapid thermal annealing (RTA) have been investigated thoroughly. Scanning electron microscopy and transmission electron microscopy (cross section) results show that the morphologies of the annealed samples were uneven, but the surface and interface of RTA samples were better than that of furnace annealed samples. The specific contact resistivity of TaSi2 to n+ ‐Si substrates with Kelvin structure was measured. The contact resistivity increased as the annealing temperature increased, but was lower for RTA samples than for furnace annealed samples. Sheet resistance measurement, x‐ray diffraction, and Auger electron spectroscopy analysis techniques were used to monitor the formation of TaSi2 films. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new x‐ray diffractometer design for thin‐film texture, strain, and phase characterization

    Page(s): 1749 - 1755
    Save to Project icon | PDF file iconPDF (1107 KB)  

    Powder diffraction techniques are potentially extremely useful for the characterization of a variety of metallic thin films which are used as interconnection materials in very large scale integrated (VLSI) devices. Phase identification, texture determination, elastic strain measurement, and grain size distribution can, in principle, be obtained nondestructively. Although x‐ray techniques have long been applied to bulk materials for these purposes, conventional x‐ray equipment, particularly the widely used Bragg–Brentano powder diffractometer, is often unsuitable for use on these thin films. High‐angle reflections are extremely weak, strong texture renders many reflections inaccessible, and reflections from the silicon single crystal substrate can be a serious interference. The Seemann–Bohlin focusing geometry with a fixed low angle of incidence provides improved intensities and reduced substrate interference, but is unsuitable for texture determinations or strain measurements. We have designed a unique instrument, called a generalized focusing diffractometer (GFD), which combines the intensity advantages of a focusing geometry with the flexibility necessary for texture and strain measurements. The key capability is the arbitrary setting of the incidence beam angle α, independent of the Bragg angle 2θ, which allows accessing of practically any desired set of Bragg diffraction planes in the sample. The focusing condition is achieved in such a geometry by computer control of the sample to detector (receiving) slit distance. Four distinct modes of operation are possible with the GFD: Bragg–Brentano (BB), Seemann–Bohlin (SB), texture analysis (TA), and strain analysis (SA). The BB and SB modes are conventional, except that the incident beam angle α, can be varied arbitrarily in the SB mode, allowing small 2θ values to be explored. In the TA mode, the sample is rocked through a range of in- - cidence angles while the detector is fixed in 2θ, but continuously positioned relative to the sample for optimal focus. In the SA mode, profile scans of particular Bragg reflections are obtained at varying beam incidence angles while the focusing conditions are continuously maintained by detector positioning. Several examples illustrate the application of the GFD. Untextured powdered Si provides a comparison of BB and SB modes. A film of 5 nm of Au on a glass substrate with well‐developed (111) texture further illustrates the differences between these modes, and indicates the sensitivity of the GFD focusing geometry. A sample consisting of alternating layers of 50‐nm sputtered amorphous TiSi2 and 500 nm of polycrystalline Al–Si on a Si substrate is examined in the BB and SB mode both as synthesized and after two thermal cycles at 450 °C. The scans indicate well‐developed texture in the Al–Si film and the thermally induced growth of silicide crystallites. A sample of highly textured 1000‐nm Al sputtered on Si is examined in TA mode to demonstrate this capability. Finally, SA scans on a sample of highly textured 750‐nm Al‐1% Sm sputtered on Si have been used to determine the strain in the thin film. The results are compared with those obtained by utilizing the wafer curvature method of strain analysis. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An investigation of hydrogen concentration profiles in as‐deposited and annealed chemical vapor deposited SiO2 films

    Page(s): 1756 - 1762
    Save to Project icon | PDF file iconPDF (932 KB)  

    Hydrogen concentration depth profiles in as‐deposited and annealed chemical vapor deposited silicon oxide [2% P glass, 8% P glass, tetraethylorthosilicate (TEOS), phosphorous‐doped TEOS and plasma oxide] films were measured using the nuclear reaction profiling technique with a 6.4 MeV 15N ion beam. The H2/Ar annealing of 450 °C for 60 min in furnace and the rapid thermal annealing at 1000 °C for 60 s in O2 or H2/Ar were carried out. It is found that hydrogen concentration is in the range 1021–1022 per cm3 in as‐deposited films. Annealing at high temperatures, even in hydrogen containing medium, lowers the hydrogen concentration in all films. The hydrogen concentration gradually increased with time when the films were left in the room environment. The electrical properties of the oxide are found to be related to the presence of hydrogen. The observed correlation between the flatband voltage and the hydrogen concentration is presented and discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal stability of polyimidesiloxane (SIM‐2000)

    Page(s): 1763 - 1767
    Save to Project icon | PDF file iconPDF (617 KB)  

    Polyimides are finding increased use in integrated circuits as a dielectric and protective layer. Its low dielectric constant, ease of application, and ability to planarize the surfaces, permit their incorporation into very large scale integrated and ultra‐large scale integrated circuit processing. However, there is no single polyimide available which possesses high‐temperature stability at temperature ≫300 °C. A newer class of polymers called polyimidesiloxane (SIM‐2000), resulting from the modification of polyimides by special equilibrated silicone blocks, has been found superior to commercial polyimides especially with respect to their high‐temperature stability. In this paper, we present the results of our investigation of the high‐temperature stability of a few polyimidesiloxane materials spun on various substrates including Si, SiO2, and Al. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

The Journal of Vacuum Science and Technology B is devoted to reports of original research, review articles, and Critical Review articles.

Full Aims & Scope

Meet Our Editors

Gary E. McGuire
International Technology Center