bluuebunny/crossref_metadata_2025 huggingface dataset:
Focused ion beam XeF2 etching of materials for phase-shift masks
Authors: Harriott L. R.
Published: July 2002

Phase-shift masks (PSMs) for photolithography are emerging as a very important technology for integrated circuit manufacture at 0.35 μm design rules and below using conventional optical step and repeat cameras at 365 and 248 nm. One of the biggest issues which remains unresolved in the fabrication of PSMs is defect repair. The sensitivity to printing of defects is much worse for phase defects than defects on conventional photomasks. In addition, the repair of defects in transparent dielectric materials at high-spatial resolution presents many challenges. Focused ion beams (FIBs) offer the necessary spatial resolution for PSM repair. This article discusses the addition of etchant gas to the FIB process for enhanced etch rates, decreased optical effects from implanted ions and possible etch selectivity for process control.
Determination of oxygen concentration in heavily doped silicon
Authors: Goldstein Michael , Chu Paul K. , Bleiler Roger J.
Published: July 2002

A number of years ago secondary ion mass spectrometry was proposed as a viable technique to determine the oxygen content in low resistivity (<0.1 Ω cm) silicon substrates. Since then, significant advances have been made in analytical protocols and instrumentation specifically for the measurement of oxygen in silicon. This article focuses on recent improvements in measurement precision and sample throughput. Presently, precisions of <±2% can be obtained on a routine basis, and can be as good as ±1.4% in the most favorable circumstances. Sample throughput has been improved to 24 per 8 h per instrument during normal operations.
Scanning tunneling microscopy system for the study of surfaces irradiated with low energy ions
Authors: Donnelly S. E. , Brooks W. S. , Vishnyakov V. , Meyer E. , Connell A. , Pearson C. , Stockmann R. , Valizadeh R.
Published: July 2002

An ultrahigh vacuum (UHV) operating scanning tunneling microscope (STM) has been designed and built with the aim of studying surfaces irradiated with low energy ions. Because the low energy ion implanter was sited in a location remote from the STM laboratory, it was also necessary to design and build a portable vacuum system which was capable of interfacing with both the ion implanter and the STM chamber, and thus, effect a sample transfer under UHV. This article presents a description of the STM and a selection of recent research results which demonstrate the capabilities of the system. In particular, the article reports on the development of small-scale structures on graphite, platinum, and copper surfaces after irradiation with low-energy helium ions and on the growth of copper islands formed by ion beam deposition on graphite substrates.
Growth of high-purity InP by chemical beam epitaxy
Authors: Rao T. Sudersena , Lacelle C. , Roth A. P.
Published: July 2002

High-purity InP layers have been grown by chemical beam epitaxy using H2 as the carrier gas for transporting the metal alkyl-trimethyl indium into the growth chamber. InP layers with μ≳1.0×105 cm2/V s and n<4.0×1014 cm−3 were grown at substrate temperatures as low as 500 °C and using a low V/III ratio (2.2) and PH3 cracking cell temperature of 900 °C. The 4 K photoluminescence spectra were dominated by donor bound excitonic transitions (D0, X)n up to n=5 and the free-excitonic (X) transitions for InP layers grown above 500 °C.
Chemical beam epitaxy of InxAs1−xP/InP strained single and multiquantum well structures
Authors: Bensaoula A. , Rossignol V. , Bensaoula A. H. , Freundlich A.
Published: July 2002

High-quality pseudomorphically strained InAsxP1−x/InP superlattices and strained multiquantum wells (SMQW) were grown by chemical beam epitaxy (CBE). The As versus P incorporation ratios in ternary InAsP layers is investigated showing that CBE is perfectly suited for a successful control of As composition in such heterostructures. InAs1−xPx/InAs SMQWs with As composition ranging from 30% to 70% were reproducibly realized. The control of InAsP well thickness and composition on the scale of the monolayer as determined through x-ray diffraction analysis is achieved.
Electron-induced nitridation of GaAs(100) with ammonia
Authors: Sun Y.-M. , Ekerdt J. G.
Published: July 2002

Nitridation of GaAs(100) was observed at temperatures ranging from 323 to 523 K by simultaneous exposure of the substrate to a molecular ammonia flux and electron irradiation in an ultrahigh vacuum environment. Incident electron energies of 350–3000 eV were employed. A GaN surface film formed. GaN formation was related to the amount of chemisorbed NH3 and the electron beam flux. The nitridation process was nonthermal. Two possible reaction schemes involving dissociative electron attachment and dissociative electron ionization are discussed.
Secondary ion mass spectrometry analysis of ultrathin impurity layers in semiconductors and their use in quantification, instrumental assessment, and fundamental measurements
Authors: Dowsett M. G. , Barlow R. D. , Allen P. N.
Published: July 2002

The subject of this review is the secondary ion mass spectrometry (SIMS) analysis of ultrathin or delta layers of impurity in a semiconductor matrix and their use in establishing the limitations of SIMS depth profiling, exploring the fundamental processes occurring during analysis, and enhancing the quantification of SIMS data. Methods for extracting accurate information for the grower (concerning the material) and the analyst (concerning the SIMS instrument) are described. It is demonstrated that sets of SIMS profiles obtained over a range of analytical conditions are desirable if accurate information is required. In this context, the observation of dopant interaction occurring in codoped samples during SIMS analysis is reported for the first time. It is shown that quite large discrepancies exist between different measurements of decay length and associated parameters for the same impurity/matrix combination. These need to be explained before attempting to relate delta profile shape to primary ion beam induced mass transport mechanisms. The concept of the delta profile as a response function and the use of deconvolution as a complete quantification method are discussed. The use of delta profiles in setting up models of the ion–solid interaction such as IMPETUS is illustrated.
In situ study of epitaxial CoSi2/Si(111) by ballistic-electron-emission microscopy
Authors: Sirringhaus H. , Lee E. Y. , von Känel H.
Published: July 2002

We have performed in situ ballistic-electron-emission microscopy (BEEM) and spectroscopy (BEES) at 77 K on epitaxial CoSi2/Si(111) films grown by molecular beam epitaxy. The transport in the silicide was found to be essentially ballistic. With the help of atomic-resolution scanning tunneling microscopy it has been found that the BEEM current depends significantly on the surface electronic structure. On strain-relaxed layers, hot electron scattering at individual interfacial dislocations has been observed for the first time by BEEM. Apart from the surface- and dislocation-induced contrast variations, the BEEM current is generally homogeneous.
A novel technique for shifter void defect repair by a focused ion beam tool
Authors: Jinbo Hideyuki , Takushima Katsuhiro , Saito Taro , Ashida Itsuji , Tanaka Yoshio
Published: July 2002

A new phase-shifting mask repair concept, transferred image correction (TRIC), for repairing shifter void defects is proposed. TRIC repair fills shifter voids with an opaque material by focused ion beam (FIB) deposition, in which a FIB tool is used to partially remove Cr adjacent to the void. The transferred image of a TRIC-repaired mask pattern corresponds to that of the original mask pattern with no defects.
Fabrication using x-ray nanolithography and measurement of Coulomb blockade in a variable-sized quantum dot
Authors: Burkhardt M. , Smith Henry I. , Antoniadis D. A. , Orlando T. P. , Melloch M. R. , Rhee K. W. , Peckerar M. C.
Published: July 2002

We report on the fabrication and measurement of a novel type of quantum dot device in which the shape and size of the dot can be controlled. The device consists of four uniformly spaced quantum point contacts which can be biased to produce quantum dots ranging in size from 600 nm to below 200 nm. The capacitances of the gates controlling the dot are small. Measurements were made at a temperature of 0.3 K for three different dot sizes. Devices were fabricated in three lithography steps, with x-ray nanolithography used to define the final gate layer. The device exhibits conductance maxima whose spacing depends on which quantum point contacts are used to define the quantum dot.
Cross-sectional scanning tunneling and scanning force microscopy of amorphous hydrogenated silicon pn-doping superlattices in nitrogen and in air
Authors: Teuschler Thomas , Hundhausen Martin , Eckstein Ralf , Ley Lothar
Published: July 2002

Amorphous hydrogenated silicon (a-Si:H) based pn-doping superlattices grown by radio-frequency-plasma deposition onto crystalline Si substrates were cleaved in air according to the crystallographic orientation of the substrate material. Their cross-sectional face is investigated using scanning tunneling microscopy (STM) and scanning force microscopy (SFM). With constant current STM in a dry nitrogen ambient at atmospheric pressure tip deflections due to the pn-superlattice periodicity are observed. With contact mode SFM in air only the transition from the substrate to the superlattice thin film but no periodic structure is resolved. A model calculation suggests that the apparent periodic height variation in constant current STM is due to a difference between p- and n-type doped layers in their density of accessible states for tunneling.
Experimental evaluation of an electron-beam pulse modulated blanker (160 MHz) for next-generation electron-beam raster scan systems
Authors: Muray Andrew , Colby Dave , Teitzel Robin , Gesley Mark
Published: July 2002

The simplicity of raster scan architecture has several benefits for mask-making production tools, the most important being accuracy. Nevertheless, building patterns on a grid resolution determined by the writing address of the raster scan mask generator places limitations on pattern edge locations, or equivalently, on throughput. A method of getting around this throughput bottleneck is pixel-level dose modulation, i.e., graybeam. In this article, a new driver technology in combination with the MEBES(R) 4500 blanker operating at 160 MHz is experimentally evaluated for real-time dose modulation by pulse width variation. Measurements of the rise and fall time of the blanker driver using various input data vectors (i.e., combinations of various pulse width signals) and a beam current modulation transfer function for the blanker are presented. Contributions from electronic artifacts such as electronic jitter are measured. Finally, these measurement results are used to determine the preliminary performance of a graybeam system.
Deep-etch silicon millimeter waveguide structure for electron acceleration
Authors: Willke T. L. , Feinerman A. D.
Published: July 2002

An ultrahigh vacuum compatible planar corrugated millimeter mm-waveguide structure (410-μm-deep) possessing bi-fold symmetry and a precision beam aperture (800 μm) has been fabricated using silicon processing technology, modeled with numerical analysis software, geometrically characterized, and compared to a similar waveguide fabricated using deep x-ray lithography (DXL) techniques. The waveguide was fabricated to operate at 60 GHz (λ=5 mm) with fields suitable for 2π/3 phase advance operation. Multichip alignment technology was used to provide a semiclosed conducting surface with aperture-coupled periodic resonator cavities. A pair of Si/Pyrex composite metallized substrates patterned with corrugated geometries have been vertically stacked with 980-μm-diam Pyrex capillaries. Geometrical analysis of the muffin-tin waveguide was divided into two classifications: substrate feature error and die-to-die orientation error. Both types of error were characterized with the following results: feature accuracy was maintained to 0.1%–1.0% tolerances in all directions (5 μm or less in most cases) and die-to-die aperture distance agreed to within ∼3% of theoretical calculation. Methods of improving these geometrical tolerances are suggested and critical issues are addressed. Electromagnetic testing of the mm waveguide has been investigated and a bead was fabricated for use in a bead-pull perturbation measurement of acceleration properties. The concluding section compares deep-etch silicon and DXL approaches for the fabrication of the ‘‘micro-linac.’’ It is concluded that through further refinement of thermal and conductive properties that the silicon waveguide is a viable method of constructing a micro-linac mm waveguide, requiring less fabrication complexity, processing time, and capital equipment investment than DXL.
Quantum confined Stark effect near 1.5 μm wavelength in InAs0.53P0.47/GayIn1−yP strain-balanced quantum wells
Authors: Mei X. B. , Bi W. G. , Tu C. W. , Chou L. J. , Hsieh K. C.
Published: July 2002

We report that high-quality InAsP/GaInP strain-balanced multiple quantum wells (MQWs) at 1.5 μm wavelength can be grown by gas-source molecular beam epitaxy. In order to obtain a large quantum-confined Stark effect, relatively thick (∼100 Å) InAs0.53P0.47 layers (lattice mismatch 1.8%) have been grown without strain relaxation. Our theoretical calculation shows that, while fulfilling the strain balance condition, the GaInP barriers should have a large thickness and small strain to reduce strain relaxation in these layers. Large Stark shift (32 meV at 180 kV/cm field) has been observed in a p-i-n diode structure with 20-period InAs0.53P0.47/Ga0.16In0.84P MQWs as the intrinsic region. The large change of absorption coefficient under electric field (∼3800 cm−1 at 80 kV/cm) indicates that this material is very promising for optical modulators near 1.5 μm.
Surface phenomena and kinetics of Si1−xGex/Si (0≤x<1) growth by molecular beam epitaxy using Si2H6 and Ge/GeH4
Authors: Zhang F. C. , Singh J. , Bhattacharya P. K.
Published: July 2002

Molecular beam epitaxy of Si1−xGex alloys, grown on (100)-oriented Si substrates by using gaseous Si2H6 and GeH4 as sources in the alloy composition range x<0.33, and on (100)-oriented and (100)-misoriented Si substrates by using gaseous Si2H6 and solid Ge as sources over the alloy composition range (0≤x<1), has been studied. From the observed growth rates as a function of composition it is evident that the presence of Ge tends to decrease the Si incorporation rate. Our results indicate growth via adatom migration to kink sites in a dissociative chemisorption process.
Molecular beam epitaxy growth of resonant-cavity separate-absorption-and-multiplication avalanche photodiodes
Authors: Anselm K. A. , Murtaza S. S. , Hu C. , Campbell J. C. , Streetman B. G.
Published: July 2002

We discuss the design and growth considerations of a resonant-cavity separate-absorption- and-multiplication avalanche photodiode and the effects of misfit dislocations that originate in the lattice-mismatched absorption layer. This device is grown on a GaAs substrate using molecular beam epitaxy and is designed to detect light near wavelengths of 900 nm. Such photodetectors have exhibited the following characteristics: an external quantum efficiency of nearly 80%, a spectral linewidth of less than 8 nm, an avalanche gain in excess of 40, and low dark current. In addition, a low excess noise factor corresponding to 0.2≤k≤0.3 has been achieved.
Material optimization for a polarized electron source from strained GaAs:Be grown on an InGaP pseudosubstrate
Authors: Bi W. G. , Tu C. W.
Published: July 2002

We report material optimization for a polarized electron source from strained GaAs:Be grown on an Inx0Ga1−x0P pseudosubstrate, i.e., a fully relaxed Inx0Ga1−x0P buffer layer on a GaP substrate, whereby the large lattice mismatch between the Inx0Ga1−x0P and the GaP was relieved by a linearly graded InxGa1−xP buffer layer. By changing the In composition x0 in the Inx0Ga1−x0P, strained GaAs:Be active layers with various lattice mismatch were obtained, and the effect of growth conditions on the residual strain in GaAs as well as the strain-induced enhancement of electron-spin polarization were studied. The results show that the residual strain in the GaAs layer is very sensitive to the growth temperatures, and that by choosing the right growth conditions, the strain in GaAs can be maintained even when the film exceeds its theoretical critical layer thickness. Enhanced electron-spin polarization has been observed from samples with larger strain.
Carbon tetrabromide doping memory effect, incorporation efficiency, and InAlAs/InGaAs heterojunction bipolar transistor application
Authors: Hwang W.-Y. , Micovic M. , Miller D. L. , Geva M.
Published: July 2002

Secondary ion mass spectroscopy was used to study the short-term carbon doping memory effect in InGaAs lattice-matched to InP induced by using CBr4 in a solid-source molecular beam epitaxy system. Carbon incorporation efficiencies in (In,Ga)As grown at different substrate temperatures and under different group V/III flux ratios were also investigated. There is no observable carbon residual doping effect in (In,Ga)As layers grown immediately after a 1000-Å-thick (In,Ga)As layer with a carbon doping density of up to 2×1019 cm−3. However, there is a small amount of transient residual carbon doping of less than 5×1016 cm−3 in the undoped (In,Ga)As grown immediately after a 1000-Å-thick (In,Ga)As layer with a carbon doping density of about 5×1019 cm−3. A dc current gain as high as 460 in carbon-doped (In,Al)As/(In,Ga)As Npn heterojunction bipolar transistors with an 800-Å-thick base doped at 2×1019 cm−3 was achieved.
X-valley related luminescence from AlAs/(Al,Ga) As quantum well structures grown on (112)B GaAs substrates
Authors: Henderson R. H. , Towe E.
Published: July 2002

We report X-valley related photoluminescence emission from AlAs/Al0.44Ga0.56As multiple quantum well structures grown on (112)B GaAs substrates. The low temperature (100 K) spectra of these structures exhibit two distinct emission peaks. One peak, located at 2.049 eV, is shown to be due to direct gap Γ-valley transitions. This peak is independent of the layer thicknesses. The second peak, believed to be due to spatially separated X-valley related transitions, depends on the layer thicknesses. The X-valley transitions are mediated by scattering wave vectors and are enhanced because of the closeness of the AlAs mole fraction in our samples to the direct–indirect crossover composition.
Electrostatic analysis of field emission triode with volcano-type gate
Authors: Wang Baoping , Tong Linsu , Sin Johnny K. O. , Poon Vincent M. C.
Published: July 2002

More researchers have recently paid much attention to the fabrication of field emission triode with a volcano-type gate on the silicon substrate because of their ease of fabrication and low cost. In this article, five different structures of this triode are presented. The electric field on the tip of field emitter (Etip) is calculated for these structures by using the EMAS software, and the different potential distribution and electric field distribution are obtained from these calculations. The results show that the diameter of the gate hole is important in determining Etip for this triode. Because the volcano-type gate holes fabricated by wet or dry etching have a very sharp rim, when the distance between anode and gate is small, a high electric field more than 1×107 V/cm is formed on the rim of gate hole at the given gate voltage Vg and anode voltage Va.
Cone-shaped metal–insulator–semiconductor cathode for vacuum microelectronics
Authors: Ishikawa Junzo , Inoue Kazunori , Sadakane Shinji , Gotoh Yasuhito , Tsuji Hiroshi
Published: July 2002

A cone-shaped metal–insulator–semiconductor (MIS) cathode, in which a field emitter is combined with a MIS structure, has been proposed in order to achieve a low-voltage operation and stable cathode for vacuum microelectronics. The cathode can supply the electrons with higher energies than those at the Fermi level of the metal surface of the emission area, by which the emission voltage and stability of a field emitter will be improved. We made a theoretical investigation on the influence of the electron energy to the electron transmission coefficient. It was found that the transmission coefficient increased drastically with the electron energy. The cone-shaped MIS cathodes were fabricated and their characteristics were investigated in a high vacuum condition. The emission efficiency reached 8% without applying an external electric field. We also confirmed the reduction of the emission voltage by 5 V with the external field. Fundamental characteristics of the cone-shaped MIS cathode have been demonstrated.
Two-stage distributed amplifier on field emitter arrays
Authors: Zakharchenko Y. F. , Torgashov G. V. , Gulyaev Y. V. , Sinitsyn N. I. , Nefedov I. S. , Zhbanov A. I. , Il’in E. M.
Published: July 2002

A two-stage distributed microwave amplifier with field emitter arrays is analyzed. It is shown to be capable of operating in the millimeter wavelength band and to provide better performance as compared with reported amplifier designs.
Characterization of amorphous carbon coated silicon field emitters
Authors: Myers A. F. , Camphausen S. M. , Cuomo J. J. , Hren J. J. , Liu J. , Bruley J.
Published: July 2002

Amorphous carbon was deposited on needle-shaped Si field emitters by filtered cathodic arc. Electron emission was obtained from these coated cathodes, but was reduced compared to emission from uncoated Si cathodes. Electron energy loss spectroscopy indicated that the coating was a high sp2 content amorphous carbon. Au particles were found to have precipitated out of the Si emitters, which were grown by a vapor–liquid–solid technique utilizing the Au–Si eutectic during the oxidation and chemical etch sharpening of the emitters. High resolution transmission electron microscopy and selected area electron diffraction confirmed the amorphous nature of the coating and the presence of the Au particles at the Si surface. The field emission, electron energy loss spectroscopy, high resolution transmission electron microscopy, and selected area electron diffraction results are presented and discussed.
Surface reaction of trimethylgallium on GaAs
Authors: Nishizawa Jun-ichi , Sakuraba Hiroshi , Kurabayashi Toru
Published: July 2002

The surface reaction mechanism of Ga(CH3)3 (trimethylgallium: TMG) on GaAs during monolayer growth by molecular layer epitaxy was investigated by quadrupole mass spectroscopy. The desorbed species by the reaction of TMG on GaAs (001), (111)As, and (111)Ga surfaces have been studied by the quadrupole mass spectroscopy signals. At 420–510 °C, adsorbed monolayers of GaCH3 are formed on the GaAs (001) surface by sufficient TMG introduction. The adsorbed GaCH3 form Ga and CH3 with a time constant of 15–36 s in the transient state. Furthermore, the decomposition of TMG occurs on this adsorbed GaCH3 or Ga layer as the steady state reaction progresses and volatile GaCH3, Ga(CH3)2, and CH3 are produced. In the case of (111)As, TMG decomposed into Ga and CH3 above 480 °C, below which the volatile adsorbates GaCH3 and Ga(CH3)2 are formed. These adsorbates migrate on the surface and react with each other or with TMG, gradually decomposing into Ga. TMG adsorbs temporarily on the (111)Ga surface and decomposes into GaCH3 and Ga(CH3)2 and they desorb quickly; therefore no adsorbates stay on the (111)Ga surface after TMG injection. At temperatures below 450 °C, TMG adsorbs on the (111)Ga surface with no TMG decomposition.
Multiwavelength ellipsometry for real-time process control of the plasma etching of patterned samples
Authors: Maynard Helen L. , Layadi Nacer , Lee John Tseng-Chung
Published: July 2002

We present a quantitative model to understand the ellipsometry traces recorded while etching patterned wafers in a high-density plasma reactor. This model allows one to determine the real-time thickness of a film as it etches, and data are presented showing the real-time thickness of TiN and polysilicon layers while etching. The model is generic to the film type and can be applied to any arbitrary stack of materials. Knowing the thickness in real time allows greater process control, as it enables one to stop or change the process at a specified remaining film thickness. The model is essentially geometric and does not include the effect of diffraction. It has been applied successfully to many samples, each with different integrated circuit layouts. The results are in good agreement with scanning electron microscopy measurements.
Theoretical analysis of field emission from a metal diamond cold cathode emitter
Authors: Lerner Peter , Cutler P. H. , Miskovsky N. M.
Published: July 2002

Recently, Geis et al. [J. Vac. Sci. Technol. B 14, 2060 (1996)] proposed a cold cathode emitter based on a Spindt-type design using a diamond film doped by substitutional nitrogen. The device is characterized by high field emission currents at very low power. Two properties, the rough surface of the metallic injector and the negative electron affinity of the (111) surface of the diamond are essential for its operation. We present a first consistent quantitative theory of the operation of a Geis–Spindt diamond field emitter. Its essential features are predicated on nearly zero-field conditions in the diamond beyond the depletion layer, quasiballistic transport in the conduction band, and applicability of a modified Fowler–Nordheim equation to the transmission of electrons through the Schottky barrier at the metal-diamond interface. Calculated results are in good qualitative and quantitative agreement with the experimental results of Geis et al.
Synthesis, structure, and optical properties of nanometer-sized In2O3 capped by anionic surfactant
Authors: Xiaochun Wu , Rongyao Wang , Bingsuo Zou , Pengfei Wu , jiren Xu , Wei Huang
Published: July 2002

In this article, nanometer-sized In2O3 organosol capped with a layer of anionic surfactants was prepared using microemulsion method. Its structure and optical properties were investigated through transmission electron microscopy, ultraviolet-visible absorption spectra, photoluminescence spectra and Z-scan technique. It was found that the prepared In2O3 organosol showed a series of new optical properties, which can be explained by its special oxygen vacancy structure. These new optical properties enhance its applications in information optics.
Nitridation of GaAs using helicon-wave excited and inductively coupled nitrogen plasma
Authors: Hara Akio , Nakamura Ryuichi , Ikoma Hideaki
Published: July 2002

GaAs was nitrided in the helicon-wave exited N2+Ar mixed plasma without and with a short-time pretreatment in inductively coupled O2+Ar mixed plasma. Nitridation of GaAs was also attempted using the inductively coupled N2+O2 mixed plasma. Relatively good capacitance–voltage (C–V) characteristics were obtained as compared with those reported in a previous article, especially for the GaAs samples treated in N2+Ar plasma with the pretreatment in O2+Ar plasma and treated in the N2+O2 plasma. Positive bias-temperature stress improved, to a certain degree, the C–V characteristics. Photoluminescence at low temperature showed that the interface with good electrical quality was obtained after these N2-plasma treatments. X-ray photoelectron spectroscopic data indicated that the stable GaN bonds were formed through nearly the whole depth of the grown film, with very small amounts of the suboxides of Ga and As. This indicates that N2-plasma treatment substantially suppressed oxidation of GaAs.
Experimental and theoretical characterization of integrated field emission nanotips
Authors: García N. , Marqués M. I. , Asenjo A. , Correia A.
Published: July 2002

An experimental and theoretical analysis of integrated nanotips and field emission arrays is presented in this article. Atomic force and scanning electron microscopy techniques were used to characterize the morphology of the monotips apex. Different positions of the tip with respect to the extraction lenses and morphologies were observed leading to different values of the tip emission current. Numerical calculations were performed considering the integrated tip as an electrostatic two-dimensional system allowing study of potential distributions, electrostatic fields near the tip apex, current density of emitted electrons, and electron trajectories. The correlation between experimental and theoretical results allows us to better understand the effect that the geometrical properties of the integrated nanotips, such as misalignments or morphology failures, produce on the emission current. Experiments and theory support the idea that the best emission is obtained for centered sharper tips with their apex localized at the level of the extraction lenses. Furthermore, slight modifications of the tip geometry lead to significant changes in the current distribution of emitted electrons.
Field electron emission of diamondlike carbon films deposited by a laser ablation method
Authors: Hong Young Kyu , Kim Ju-Jin , Park Chan , Kim Jin Seung , Kim Jae Ki
Published: July 2002

We have investigated field electron emission properties of diamondlike carbon films deposited by a laser ablation method. Emission properties of diamondlike carbon films show a strong correlation with surface roughness of the films which varies as a function of laser power densities. The threshold emission voltage of films turns out to be critically dependent on the surface morphology. Measurement of electrical resistivity shows that the density of states near the Fermi level is strongly localized. The major carrier transport occurs not by the activation to the conduction band but by hopping between the localized defect states near the Fermi level. The existence of localized defect bands in the intrinsic gap can also make it possible to emit electrons with a relatively small activation energy.
Substitutional carbon incorporation into molecular beam epitaxy-grown Si1−yCy layers
Authors: Zerlauth S. , Penn C. , Seyringer H. , Brunthaler G. , Bauer G. , Schäffler F.
Published: July 2002

To study the growth conditions for substitutional incorporation of carbon into Si layers a series of pseudomorphic Si1−yCy/Si superlattices was grown by molecular beam epitaxy (MBE) with absolute carbon concentrations between 0.3% and 2% and growth temperatures varying between 400 and 650 °C. All layers showed well behaved Si1−yCy band gap photoluminescence, which shifts linearly to lower energies with increasing carbon content at a slope of 70 meV per atomic percent of substitutional carbon. We employed a novel technique for an unambiguous determination of the substitutional carbon concentrations, which is based on comparative x-ray rocking analyses of Si1−yCy/Si superlattices grown with constant and step-graded temperature profiles. In addition, the surface morphology was assessed by a combination of in situ reflection high energy electron diffraction experiments and postgrowth atomic force microscopy investigations on single layers and superlattices. At MBE-typical growth rates around 1 Å/s, we find complete substitutional incorporation of carbon up to growth temperatures of 550 °C and carbon concentrations of 1.2%. At higher growth temperatures and/or higher carbon fluxes, the percentage of substitutionally incorporated carbon drops drastically, concomitant with a morphological transition from two-dimensional to three-dimensional growth.
Photoluminescence and photoconductivity of Si- and Ge-rich SiGe bulk crystals
Authors: Franz M. , Pressel K. , Barz A. , Dold P. , Benz K. W.
Published: July 2002

We have investigated Si- (0⩽x⩽0.13) and Ge-rich (0.90⩽x⩽1) Si1−xGex bulk crystals by photoluminescence and photoconductivity measurements. The small linewidths of the near band edge luminescence of less than 4 meV demonstrate the high quality of the crystals. Luminescence linewidth, line shape, and intensity ratios of transitions with and without phonon participation reveal a stronger influence of alloy effects on excitons on the Ge-rich side compared with the Si-rich side. Photoconductivity spectra of boron doped Si-rich and phosphorus doped Ge-rich Si1−xGex crystals show the influence of alloy composition and alloy fluctuations on the impurity levels. The shift of the photoconductivity spectra with increasing Si or Ge concentration indicates the change of the ground state energy of the impurity with changing alloy composition.
Photoresist erosion studied in an inductively coupled plasma reactor employing CHF3
Authors: Doemling M. F. , Rueger N. R. , Oehrlein G. S. , Cook J. M.
Published: July 2002

The evolution of integrated circuits into the ultralarge scale integrated regime takes today’s 0.35 μm circuit design rules to even smaller values of 0.18 μm and beyond. As a consequence, photoresist masks are becoming thinner and even more prone to erosion by etching. For this work an I-line novolak resist was used. Etch rates for various process conditions using in situ ellipsometry were obtained. Also the fluorocarbon surface layer, present on top of the photoresist during steady state etching was examined with x-ray photoelectron spectroscopy. The investigated pressure range was 6 to 20 mTorr and the inductive power range was 300 to 1400 W. It was found that there are two distinct regimes of etching behavior. At inductive powers below 600 W the etching is energy flux limited, at higher inductive powers the etching is ion energy limited.
Ballistic electron emission microscopy spectroscopy study of AlSb and InAs/AlSb superlattice barriers
Authors: Cheng X.-C. , McGill T. C.
Published: July 2002

Due to its large band gap, AlSb is often used as a barrier in antimonide heterostructure devices. However, its transport characteristics are not totally clear. We have employed ballistic electron emission microscopy (BEEM) to directly probe AlSb barriers as well as more complicated structures such as selectively doped n-type InAs/AlSb superlattices. The aforementioned structures were grown by molecular beam epitaxy on GaSb substrates. A 100 Å InAs or 50 Å GaSb capping layer was used to prevent surface oxidation from ex situ processing. Different substrate and capping layer combinations were explored to suppress background current and maximize transport of BEEM current. The samples were finished with a sputter deposited 100 Å metal layer so that the final BEEM structure was of the form of a metal/capping layer/semiconductor. Of note is that we have found that hole current contributed significantly to BEEM noise due to type II band alignment in the antimonide system. BEEM data revealed that the electron barrier height of Al/AlSb centered around 1.17 eV, which was attributed to transport through the conduction band minimum near the AlSb X point. Variation in the BEEM threshold indicated unevenness at the Al/AlSb interface. The metal on semiconductor barrier height was too low for the superlattice to allow consistent probing by BEEM spectroscopy. However, the superlattice BEEM signal was elevated above the background noise after repeated stressing of the metal surface. A BEEM threshold of 0.8 eV was observed for the Au/24 Å period superlattice system after the stress treatment.
Experimental evaluation of a miniature electrostatic thin-foil electron optical column for high current and low-voltage operation
Authors: Winkler Dieter , Bubeck Claus-D. , Fleischmann Andreas , Knell Guido , Lutsch Yvonne , Plies Erich
Published: July 2002

A miniaturized electrostatic electron optical column, consisting of thin commercial electron-microscope apertures as electrodes [Burstert, Winkler, and Lischke, Microelectron Eng. 31, 95 (1996)] has been successfully constructed and evaluated. An electron probe with a current of 300 nA and a spot size of 0.6 μm is achieved at 3 keV. The system is operated with beam energies as low as 300 eV, yielding 600 nA in a 2 μm spot size. Long term stability and reproducibility are achieved over operation times of several months. This demonstrates that the column is suitable for testing purposes where a high signal-to-noise ratio is required.
Negative chemically amplified resist characterization for direct write and SCALPEL nanolithography
Authors: Ocola L. E. , Biddick C. J. , Tennant D. M. , Waskiewicz W. K. , Novembre A. E.
Published: July 2002

Despite the common link of using high energy electrons as exposure probes in direct write and SCALPEL lithography, the imaging systems in both are different. The question arises then if an optimal process for direct write lithography will provide optimal results in SCALPEL. Characterization of a series of negative tone chemically amplified resists for use in direct write (at 50 kV) and projection electron beam (at 100 kV) nanolithography is reported. The current work has explored modifying the postapplied bake and postexposure bake temperatures and times to find an optimum process for direct write nanolithography and then verify it is applicable to SCALPEL. Results, using NEB-22A (Sumitomo Chemical Co.), show that this is possible. We have demonstrated that in direct write, the NEB-22A resist has excellent resolution (36 nm in 125-nm-thick resist, 75 nm in 500-nm-thick resist) and process latitude (>20%), with a sensitivity of about 14 μC/cm2 at 50 kV exposure. The etch resistance is 3 nm/s and is being used for gate level e-beam lithography of single level field-effect transistors. The optimal bake conditions are found to be longer than usual postapplied and postexposure bake times. We have also demonstrated that the optimal bake conditions can be transferred to a SCALPEL exposure with similar process latitude and resolution.
Particle manipulation and surface patterning by laser guidance
Authors: Renn Michael J. , Pastel Robert
Published: July 2002

Laser-induced forces are used to manipulate atoms, clusters, and micron-sized particles in hollow optical fibers. Laser light (400 mW, 800 nm) is guided in a low-order grazing incidence mode in glass capillaries. The optical field in the fiber generates gradient and scattering forces which simultaneously draw particles to the center of the hollow region and push them along the fiber axis. Dielectric, semiconductor, and metal particles in the size range of 9 μm–50 nm have been guided in gas- and liquid-filled fibers. Rb atoms are guided in evacuated fiber for up to 15 cm. Used alone or in conjunction with traditional methods, laser guidance is attractive for direct-write lithography. Arbitrary surface patterns can be created under ambient conditions with potential write speeds exceeding 106 particles/s and placement accuracy approaching 50 nm (assuming a 1 W laser, 100 nm Ge particles, and fiber filled with Ar at 760 Torr). Anisotropic optical forces resulting from particle shape anisotropy act to orient particles in the fiber. In initial experiments NaCl and KI crystals in aerosol suspension have been funneled into a hollow fiber using optical forces. The crystals have been directed onto a glass surface and lines as narrow as 0.5 μm drawn. This linewidth is 30 times smaller than the inner fiber diameter and illustrates the strong focusing produced by optical forces. Atomic force microscopy images show a high degree of alignment between crystals suggesting that anisotropic optical forces act to orient the crystals during deposition.
Thermal annealing of deep ultraviolet (193 nm) induced compaction in fused silica
Authors: Piao Fan , Oldham William G. , Haller Eugene E.
Published: July 2002

Different 1995–1996 ultraviolet (UV) grade experimental fused silica samples were evaluated for their resistance to UV-induced compaction at 193 nm under elevated sample temperature conditions. We found that the compaction rate decreases with increasing sample temperature. Compaction recoveries were observed at temperatures as low as 120 °C, this suggests that the recovery of UV-induced compaction in fused silica is a thermally excited process with a low activation energy. Isothermal annealing experiments were performed on two different sets of precompacted fused silica samples. An activation energy of 0.13 eV was found for both cases.
Advanced synchrotron radiation stepper alignment system performance
Authors: Sentoku Koichi , Matsumoto Takahiro
Published: July 2002

Canon has been developing a synchrotron radiation stepper system for volume production known as the XR1. The system incorporates many-original technologies. In this article, the key features of the XR1 alignment system and its performance will be discussed. To align the mask and wafer, the alignment system uses Fresnel zone plates as alignment marks. Our alignment is based on an advanced dual grating lens method. In order to attain high alignment accuracy and large process latitude, we improved the design of alignment marks and optics of the alignment scope. The alignment marks are optimized to minimize alignment error resulting from changing the gap distance between the mask and wafer, which is called telecentricity. Using these newly designed alignment marks, we have evaluated alignment accuracy. We obtained alignment accuracy 3σ of 11.9(X) and 10.2 nm(Y) using etched SiN patterns on a Si substrate. Furthermore, the alignment scope is designed with multiwavelength light sources to illuminate the alignment marks. Selectable three laser diodes are applied in the optics. Multiwavelength light sources compensate each other and achieve robustness for various lithography processes.
Kinetics of etch products and reaction process in electron cyclotron resonance plasma etching of Si
Authors: Nishikawa Kazuyasu , Oomori Tatsuo , Ono Kouichi
Published: July 2002

The effect of etch products on the Si etching characteristics in electron cyclotron resonance plasmas with Cl2 was investigated by using both plasma diagnostics and a numerical simulation. The etch products both in the gas phase and on the etched surface were observed by in situ Fourier transform infrared (FTIR) absorption spectroscopy. The concentration range of silicon tetrachloride SiCl4 detected as the gas-phase etch product during Si etching was about 1012 molecules/cm3 within the pressure range of 0.1–10 mTorr, while that of silicon oxide was 1010–1012 molecules/cm3. On the etched surface, unsaturated silicon chlorides SiClx (x=1–3) as well as SiCl4 were observed. Moreover, the effect of the etch products was numerically investigated by using a kinetic etching model. The calculated etch rate showed good agreement with the measured one within the pressure range of 0.1–10 mTorr even though the sticking coefficient of silicon oxide was varied from 0.001 to 0.5. The coverage of the SiClx layer saturated about one monolayer beyond pressure of 1 mTorr. The bare Si surface area and the actual coverage of the oxide layer decreased by increasing the gas pressure. However, the actual coverage of oxide layer at <1 mTorr varied according to the sticking coefficient of silicon oxide. The calculated concentration of the etch products was the same order of magnitude as the concentration obtained by in situ FTIR diagnostics. It is expected that the effect of etch products on the etching characteristic, especially etched profiles, becomes more and more important at pressure of less than 1 mTorr.
Fabrication of gated nanosize Si-tip arrays for high perveance electron beam applications
Authors: Choi S. S. , Lim S. H. , Kim D. W. , Jung M. Y. , Jeon H.
Published: July 2002

Nanosize Si-tip arrays with gated electrodes have been fabricated using the self-aligned method. In order to have a parallel electron beam (high perveance beam) toward the anode plate, we have designed a nanosize tip array with heights of the tip slightly less than that of a gate electrode. A high perveance beam is supposed to provide better focusing of the electron beams. Hence, it is important to have a high perveance electron beam for nanolithographic application. The fabricated procedures for nanoscale Si-tip array are reactive ion etching, sharpening, and oxidation followed by a 7:1 BHF oxide etch. The metal gate fabrication procedures are performed with self-aligned techniques using plasma oxide deposition, metal sputter deposition, and photoresist spin coating. The self-aligned methods allow for a controlling gate aperture less than 1.0 μm. The structure of the fabricated gated electron source was designed to have a 1.5 μm gate aperture, a 1.5 μm SiO2 insulating layer, and a 0.3 μm Mo volcano-type gate electrode. The Fowler–Nordheim and current–voltage characteristics of the fabricated tip arrays after seasoning the tip in a high vacuum chamber (<5×10−8 Torr) were examined carefully and its turn-on voltage was found to be ∼25 V. The observed bright electron spots on the anode screen was measured to be ∼300 μA. The total area for the (300×300) Si-tip array was ∼1.5 mm2. A charge coupled device camera photographed the bright area on the anode phosphor plate from electron bombardments and the size of electron bombardment spot was almost the same as the original tip array area (1.8 mm2). In addition, we have also fabricated the gated Si-tip arrays with a focusing electrode for angular confinement of the electron beam emission and high perveance for the beam trajectory.
In situ ellipsometric study of the formation process of metalorganic vapor-phase epitaxy-grown quantum dots
Authors: Lee Jeong-Sik , Sugou Shigeo , Ren Hong-Wen , Masumoto Yasuaki
Published: July 2002

Our in situ ellipsometry study of metalorganic vapor-phase epitaxy-grown quantum dot (QD) structures showed that the Δ–Ψ trajectory of the ellipsometric signal in Stranski–Krastanow QD growth sharply differs from that in layer-by-layer growth. When QD formation starts, Δ rapidly decreases, inflecting the Δ–Ψ trajectory. This indicates increased scattering loss, deduced from increased surface roughness produced in the transition from two- to three-dimensional surface morphology. Ex situ atomic force microscopy and photoluminescence results correspond well to the ellipsometric signal at the start of QD formation. Based on these results, we discuss growth-dependent QD formation processes such as QD formation onset and growth mode transition.
Technique for rapid at-wavelength inspection of extreme ultraviolet mask blanks
Authors: Spector S. J. , White D. L. , Tennant D. M. , Ocola L. E. , Novembre A. E. , Peabody M. L. , Wood O. R.
Published: July 2002

We have developed two new methods for at-wavelength inspection of mask blanks for extreme-ultraviolet (EUV) lithography. In one method an EUV photoresist is applied directly to a mask blank which is then flood exposed with EUV light and partially developed. In the second method, the photoresist is applied to an EUV transparent membrane that is placed in close proximity to the mask and then exposed and developed. Both reflectivity defects and phase defects alter the exposure of the resist, resulting in mounds of resist at defect sites that can then be located by visual inspection. In the direct application method, a higher contrast resist was shown to increase the height of the mounds, thereby improving the sensitivity of the technique. In the membrane method, a holographic technique was used to reconstruct an image of the mask, revealing the presence of very small defects, approximately 0.2 μm in size. The demonstrated clean transfer of phase and amplitude defects to resist features on a membrane will be important when flagging defects in an automatic inspection tool.