bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical lithography using a single point diamond machining
Authors: Goss S. H. , Grazulis L. , Tomich D. H. , Eyink K. G. , Walck S. D. , Haas T. W. , Thomas D. R. , Lampert W. V.
Published: July 2002

A technique that produces submicron size features by machining GaAs wafers in air was studied. An apparatus was built which uses a sharp diamond tip to mechanically scribe patterns into the substrate. The debris produced from surface machining was removed by using a CO2“snow jet” sprayer, thus eliminating the use of hazardous liquid chemicals for cleaning. By changing the force between the diamond tip and sample surface, different depths of cuts were produced. This allowed the production of three dimensional patterns on the wafer in one step. With this instrument, write speeds of up to 25 μm/s on 30 μm×30 μm area patterns with a lateral resolution of 100 nm were demonstrated. In a different set of experiments, x-ray diffraction, spectroscopic ellipsometry, and cross sectional transmission electron microscopy analysis identified that subsurface damage created during the diamond turning process was removed at normal molecular beam epitaxial growth temperatures. Atomic force microscope analysis showed that the surface patterns were still present after annealing.
Atomic force microscopy correlated with spectroscopic ellipsometry during homepitaxial growth on GaAs(111)B substrates
Authors: Tomich D. H. , Eyink K. G. , Seaford M. L. , Taferner W. F. , Tu C. W. , Lampert W. V.
Published: July 2002

The growth of high quality layers on GaAs(111)B on-axis substrates has been found to be extremely difficult. Homoepitaxial growth in the (√19×√19)R23.4 reconstruction typically produces surfaces with pyramidal morphologies. Only a narrow region near the (√19×√19)R23.4 and high temperature (1×1) border has been found to produce nearly atomically flat films. In this study, we have followed the homoepitaxial growth with in situ spectroscopic ellipsometry (SE) and compared the resulting film morphologies with atomic force microscopy (AFM). The surface reconstructions during growth were determined by reflection high energy electron diffraction. SE analysis allowed the determination of surface roughness variation which occurred under various growth conditions. Under near ideal growth conditions SE indicates the filling of voids evident after oxide desorption. When growths were carried out within the (√19×√19)R23.4 reconstruction the surface was observed to roughen continuously with growth. AFM studies of these surfaces will be discussed in relation to the various stages of growth as observed with SE. The density of “triangular pits” on the surfaces grown under ideal conditions was found to be on the order of 1%.
Midinfrared silicon/germanium based photodetection
Authors: Presting H. , Hepp M. , Kibbel H. , Thonke K. , Sauer R. , Mahlein M. , Cabanski W. , Jaros M.
Published: July 2002

Highly p-doped silicon/silicon–Germanium (SiGe) quantum well structures have been grown by molecular beam epitaxy on 〈100〉 Si substrates as detectors in the midinfrared regime (3–5 μm; 8–12 μm). These detectors—operating from about 3 to 20 μm—are based on heterointernal photoemission of photogenerated holes across the Si/SiGe valence band from a highly p-doped SiGe layer which is grown on an undoped (50 Ω cm), double-sided polished Si substrate. The thickness of the well, its doping level, and its Ge content determines the valence band offset and thus the operating wavelength of the detector. This layer sequence has been repeated up to five times and the structure has been terminated with a p-doped SiGe contact layer on top. The samples grown have been extensively analyzed by secondary ion mass spectroscopy, x-ray diffraction, Rutherford Backscattering, and absorption spectroscopy. Mesa detectors of varying diameters have been fabricated using a standard Si processing technique, and the photocurrent and dark current have been measured at 77 K. A broad quantum efficiency of ηext=0.3% has been obtained (at 4 μm and 77 K) with dark current densities as low as 10−8 A/cm2. The photoresponse spectrum shows a broad maximum between 3 and 5 μm; it is shown that the peak in this spectrum can be tuned over a fairly broad range by the choice of layer composition.
Controlling transient enhanced diffusion effects in high-frequency Si0.7Ge0.3, heterojunction bipolar transistors with implanted emitters
Authors: Nanver L. K. , Visser C. C. G. , van den Bogaard A.
Published: July 2002

A method is presented by which the implantation damage induced transient enhanced diffusion of boron and phosphorus is used to advantage to fabricate high-frequency Si0.7Ge0.3 heterojunction bipolar transistors with implanted phosphorus emitters. A device with 300 Å basewidth, 7 kΩ/□ intrinsic base sheet resistance, and fT=44 GHz is demonstrated. The very low diffusivity of both boron and phosphorus in high Ge concentration SiGe during 700 °C thermal annealing results in a self-alignment of the emitter–base junction to the Si/SiGe interface, giving high current gain with good reproducibility. Methods of counteracting the boron outdiffusion in the Si collector are considered. Rather than reducing this outdiffusion, results indicate that it can be better compensated for by introducing a narrow phosphorus doped peak, epitaxially grown on the collector side of the SiGe. The n doping of this peak, as is also the case for that of the emitter, barely penetrates the SiGe and the p-doped base is well preserved.
Field emitter arrays based on natural self-organized porous anodic alumina
Authors: Govyadinov Alexander N. , Zakhvitcevich Sergej A.
Published: July 2002

The field emitter array (FEA) conception with tip’s density up to 1010 cm−2 based on natural porous anodic alumina is proposed and its realizability is demonstrated. The basic technological steps of FEA based on the anodic alumina and emission characteristic are shown.
Three-dimensional vacuum magnetic sensor with a Si emitter tip
Authors: Itoh Junji , Uemura Koji , Kanemaru Seigo
Published: July 2002

A vacuum magnetic sensor (VMS) using a silicon field emitter tip was fabricated and demonstrated. The VMS is constructed with the emitter tip generating a cross-shaped electron beam, an anode divided into eight symmetrical sectors and a vacuum-sealed glass package. The Si tip is centered in a cross-shaped extraction gate surrounded by four in-plane focusing lenses and emits a cross-shaped electron beam of 0.5 μA in current at the gate voltage of 60 V. The magnetic field externally applied to the VMS causes the translational and rotational displacement of the cross-shaped beam at the anode and these displacements are measured by detecting the difference in anode currents between neighboring two anode sectors. From preliminary experiments, we found that the present VMS had the sensitivity higher than 104(%/T).
Minority-carrier recombination lifetimes of the frontside and backside of Si wafers subjected to plasma processing
Authors: Itsumi Manabu
Published: July 2002

We have examined minority-carrier recombination lifetimes of a silicon wafer’s backside after plasma processing. The decrease in lifetime reflects the degree of Si-SiO2 interface degradation caused by plasma-induced damage. We found that even if the silicon wafer’s backside is fully covered by the stage during plasma processing, there was a further decrease in the lifetime in a region about 20 mm from the wafer’s edge. We propose that when charges are ejected from the silicon wafer to the outside of the wafer, a portion of the charges flows via the interface between SiO2 and the stage. To fully understand plasma-induced damage, in addition to examining the nature of the decrease in the lifetime of the wafer’s frontside, it is important to examine the nature of the decrease in the lifetime of the wafer’s backside in detail.
Selective area epitaxy of CdTe arrays
Authors: Luo Yuanyuan , Cavus Abdullah , Tamargo Maria C. , Wan Junzuo , Pollak Fred H.
Published: July 2002

We have performed selective area epitaxy of CdTe by using a bimetal shadow mask during molecular beam epitaxial growth on CdTe (211)B substrate and achieved patterns of square arrays similar to those used in the detector arrays. The growths were carried out at 285 and 190 °C. We observed reproducible excellent pattern definition for both conditions. The sidewalls are abrupt (∼5–7 μm when grown without sample rotation and ∼7–9 μm when grown with sample rotation), the mesa tops are flat and the separations are well defined. All the squares in a given array are uniform. Similar results were also obtained by using a mask fixture that allowed us to place the mask on the substrate within the growth chamber (in situ). This technique may be applicable for the in situ fabrication of HgCdTe focal plane arrays.
Substrate orientation dependence of carbon doping of GaAs using CBr4 source in molecular beam epitaxy
Authors: Schulte D. W. , Subramanian S. , Ungier L. , Yoo H. M. , Venkateswaran U. , Arthur J. R.
Published: July 2002

The effect of substrate orientation upon the material properties of molecular beam epitaxy grown carbon doped GaAs on (100), (111A), and (111B) orientated substrates with doping levels varying from 1017 to 1020 cm−3 is reported. Van der Pauw Hall measurements show that all samples are p-type regardless of substrate orientation. Photoluminescence (PL) measurements at atmospheric pressure show the band gap shrinkage and the broadening of the PL peaks as the doping concentration is increased. The broad PL peak is believed to arise from a combination of transitions from the conduction band (CB) to heavy hole valence band and CB to light hole valence band. Heavily doped GaAs:C samples show a series of sharp lines at high pressures that are believed to be due to transitions involving near donor–acceptor pairs.
Ga
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focused-ion-beam exposure and CF4 reactive-ion-etching development of Si3N4 resist optimized by Monte Carlo simulation
Authors: Lee Hyun-Yong , Chung Hong-Bay
Published: July 2002

Focused-ion-beam (FIB) lithographic characteristics of low-pressure chemical-vapor-deposited Si3N4 resist have been studied using low-energy Ga+ -FIB exposure and CF4 reactive ion-etching (RIE) development. The resist thickness, Zmin, to minimize a substrate damage is determined by Monte Carlo (MC) simulation. The Zmin is approximately 190, 355, and 560 Å for incident ion energies of 10, 30, and 40 keV, respectively. Ga+ FIB-exposed Si3N4 for CF4 RIE development demonstrates a negative-type resist which is dependent on resist thickness and dose. In the case of 30 keV Zmin Si3N4, a pattern is formed initially at dose of about 5.70×1015 ions/cm2 (D1), and a linewidth corresponding to a beam diameter of 0.36 μm is obtained at dose of 4.73×1016 ions/cm2 (D2). Above a critical dose of about 7.56×1016 ions/cm2 (D3), which reaches a surface concentration of about 1.5×1021 ions/cm3 according to MC simulation, a dent begins to form from the center of pattern. The reason for the formation of dent is not clear at present but may be due to the decrease of resistance against CF4-reactive gas with the increase of the surface ion concentration up to a critical value. The values (D1, D2, D3) decrease with decreasing resist thickness. As the incident energy increases, the threshold dose increases. The imaging contrast appear to be about 3.3–3.5. A 190-Å-thick Si3N4 resist exposed by 10 keV FIB with a dose of 8.0×1015 ions/cm2 increases both the refractive index n, and the optical energy gap, Eop to about Δn=0.007 and ΔEop=0.07 eV. A clear pattern with a linewidth of 0.14 μm is formed on Zmin Si3N4 resist by 40 keV FIB exposure.
Effect of the forward biasing the source-substrate junction in n-metal–oxide–semiconductor transistors for possible low power complementary metal–oxide–semiconductor integrated circuits’ applications
Authors: De la Hidalga-W. F. J. , Deen M. J. , Gutierrez-D. E. A. , Balestra F.
Published: July 2002

The use of forward biasing the source-substrate junction in metal–oxide–semiconductor transistors, to reduce its threshold voltage is a simple method to realize low power complementary metal–oxide–semiconductor integrated circuits. A 2 μm long n-metal–oxide–semiconductor field effect transistor was used as the device under test. The threshold voltage was measured in the temperature range of 300–77 K, using two different methods. The classic long channel threshold voltage model was fitted by optimization to the experimental data of the reverse-biased substrate, and the model with the fitted parameters was used to calculate the threshold voltage under forward-biased substrate conditions. The agreement between the fitted and extrapolated threshold voltage with the experimental values demonstrated the validity of this classic model for a substrate forward bias up to 0.5 V, and for a wide temperature range.
Sidewall slope control of chemically assisted ion-beam etched structures in InP-based materials
Authors: Daleiden J. , Czotscher K. , Hoffmann C. , Kiefer R. , Klussmann S. , Müller S. , Nutsch A. , Pletschen W. , Weisser S. , Tränkle G. , Braunstein J. , Weimann G.
Published: July 2002

Chemically assisted ion beam etching (CAIBE) of InP-based materials has been newly developed with BCl3/Ar in comparison to Cl2/Ar and IBr3/Ar. Using halogen gases and an argon ion beam at 400 V a very good surface morphology was obtained at a low substrate temperature of −5 °C in any case; with BCl3/Ar a surface roughness of 0.2 nm was observed. The etch rates were in the range of 40–75 nm/min depending on the reactive gas. Mixing the reactive gases or tilting the substrate with respect to the impinging ion beam allowed us an excellent control of the etched sidewall slope. By mixing BCl3 and IBr3 we were able to tune the sidewall slopes between 15° (measured to the surface normal) for pure BCl3 and 38° for the pure IBr3, respectively. Tilting the substrate allowed us to adjust the slope angle between 0° and 60°. In addition we have analyzed the etched surfaces by energy dispersive x-ray measurements. The low temperature processes yielded stoichiometric InP surfaces, etching at higher substrate temperatures results nonstoichiometric surfaces. These low temperature halogen CAIBE processes were successfully applied for the fabrication of gratings, ridge waveguides and facets for long wavelength (InGa)(AsP) and (AlInGa)(AsP) laser diodes. In this article we present ridge waveguide (InGa)(AsP)/InP lasers (1.55 μm) with direct CW modulation bandwidths of 9.5 GHz.
Experimental evaluation of the extended Schottky model for ZrO/W electron emission
Authors: Fransen M. J. , Faber J. S. , van Rooy Th. L. , Tiemeijer P. C. , Kruit P.
Published: July 2002

The energy distribution of electrons emitted from a ZrO/W electron source with a radius of curvature of 0.9 μm was determined for extraction voltages ranging from 3000 to 6000 V and emitter temperatures from 1200 to 1900 K. Full width at half maximum values of the energy spectra between 0.3 and 0.8 eV were found. The experimental data are analyzed according to the extended Schottky model for electron emission, yielding the electric field at the emitter surface. The tunneling probabilities are evaluated numerically by integrating the one-dimensional Schrödinger equation, and analytically by employing the commonly used Wentzel–Kramers–Brillouin approximation. Both approaches give good agreement with the experimental data, except for small differences probably due to Coulomb interactions (Boersch effect). The same analysis is also applied to the experimental results for a Schottky emitter with a radius of curvature of 0.3 μm, taken from literature.
Side-by-side wafer bonding of InP for use with stepper-based lithography
Authors: Ryan R. W. , Kopf R. F. , Tate A. , Burm J. , Hamm R. A.
Published: July 2002

We have developed a simple technique for wafer bonding for use with stepper-based lithography. The technique involves side-by-side bonding of two or more pieces of a wafer together with epoxy. A bonded wafer with the same dimensions, such as thickness, flatness, and position of the large flat, as a whole wafer can be run on a stepper. Since a stepper can align each field independently, all of the area without the actual bond may be patterned. This technique is quite useful for salvaging a broken wafer in the middle of processing. In addition, it may be used for bonding several substrates of different materials together for monolithic integration.
Processes of quantum dot formation in the InAs on GaAs(001) system: A reflectance anisotropy spectroscopy study
Authors: Westwood D. I. , Sobiesierski Z. , Matthai C. C. , Steimetz E. , Zettler T. , Richter W.
Published: July 2002

Reflectance anisotropy spectroscopy (RAS) has been used to monitor the formation and development of InAs islands grown onto GaAs(001) substrates by molecular beam epitaxy. Time resolved measurements show entirely different responses at different photon energies, corresponding to different aspects of the islanding process. At a photon energy of 2.6 eV RAS is sensitive to the onset of islanding, whereas the 4.0 eV signal appears to be sensitive to the continuous interisland wetting layer. Thus, by using the 4.0 eV signal it is possible to follow the real time development of the islanded surface. In particular, it is found that (1) during growth and immediately beyond the point of islanding, a fixed fraction of the incoming flux is directly transferred to the islands, and this fraction increases with increasing growth temperature up to 100%; (2) as a consequence of this, the wetting layer can increase in thickness beyond the 1.6 monolayers islanding thickness, to at least ∼2 monolayers; (3) the importance of islands acting as sinks for the acquisition of material from the wetting layer is revealed; (4) the dynamic equilibrium set up between the islands and the wetting layer is such that the thickness of the latter increases significantly with sample temperature.
New model for reflection high-energy electron diffraction intensity oscillations
Authors: Braun W. , Däweritz L. , Ploog K. H.
Published: July 2002

We investigate the influence of inelastic processes on reflection high-energy electron diffraction (RHEED) oscillations by recording energy filtered RHEED intensity oscillations during homoepitaxy of (001)-oriented GaAs. The results clearly show that the dominant inelastic scattering process, plasmon inelastic scattering, does not influence the phase of the oscillations. It cannot therefore account for an independent process contributing a phase to the oscillations that is different from elastic scattering. As an alternative approach, we investigate a basic coherent scattering model introduced by Horio and Ichimiya. We compare its predictions with experiments in the one-beam condition for both GaAs and AlAs(001) homoepitaxy. The average crystal potential required for the fits can be determined independently by Kikuchi line fits, yielding a value of 10.5±0.5 V for both GaAs and AlAs. This allows us to reduce the number of free parameters in the model to only the layer thickness. The theoretical fits of the model to the experimental data yield different layer thicknesses that are in good agreement with the surface reconstruction thicknesses for GaAs and AlAs. We therefore conclude that the phase of RHEED oscillations is determined by the surface reconstruction forming on top of the growing layer during crystal growth. This new model explains many experimentally observed RHEED oscillation phenomena in a unified approach.
Overlay accuracy tests for direct write implantation
Authors: Mogren S. , Berry I. L.
Published: July 2002

Direct write implants are usually made in registration with pre-existing features on the wafer surface. The accuracy of the registration is a critical component of the error budget for a given device, just as it is for optical lithography layers. We present a scheme for creating alignment marks in field oxide on a silicon wafer. These alignment marks can be applied near the beginning of the process, are robust in a silicon processing environment, and can be reused for multiple layers of maskless implantation. We also present our method of measuring overlay accuracy, and data showing that an accuracy of 62 nm one sigma can be achieved by our system.
Effect of H2O partial pressure and temperature during Ti sputtering on texture and electromigration in AlSiCu/Ti/TiN/Ti metallization
Authors: Yoshida Tomoyuki , Hashimoto Shoji , Mitsushima Yasuichi , Ohwaki Takeshi , Taga Yasunori
Published: July 2002

The effect of residual gas constituents and substrate temperature during Ti sputtering on the texture of TiN/Ti films deposited on SiO2/Si substrates has been investigated. The Ti (002) and TiN (111) preferred texture of the films deposited at 350 °C was found to be improved drastically by increasing the H2O partial pressure from 1×10−9 to 3×10−8 Torr. Both the Ti (002) and TiN (111) texture showed a similar H2O partial pressure and substrate temperature dependence because of the epitaxial transfer between these planes. The improved Ti (002) texture was attributed to the self-assembly of Ti atoms on the SiO2 surface, which had a low surface free energy due to the formation of surface OH groups. The AlSiCu/Ti/TiN/Ti layered film fabricated with the highly textured TiN/Ti film showed a strong Al (111) texture and had a smooth surface. Moreover, interconnects from this improved film had longer electromigration lifetimes. It was also confirmed that the increased H2O partial pressure (3×10−8 Torr) does not affect the contact resistance and junction leakage current of the AlSiCu/Ti/TiN/Ti/(n+Si or p+Si) contact system.
Electrical conductivity measurement for quantitative evaluation of development speed of a photoresist
Authors: Takeda T. , Saka M.
Published: July 2002

In a previous article, we reported on the possibility of predicting the development speed of a photoresist by measuring its electrical conductivity in an organic solvent [T. Takeda and M. Saka, J. Vac. Sci. Technol. B (submitted)]. The electrical conductivity of the organic solution of a photoresist base polymer at various frequencies was found to have a positive correlation with the dissolution speed of photoresist base polymers into an alkaline developer. In addition, the influence of the measurement temperature and the concentration of polymer solution on conductivity was investigated. Based on the collected data, this article derives the calibration equation, which was influenced neither by measurement temperature nor by the concentration of the solution.
Deep-ultraviolet interferometric lithography as a tool for assessment of chemically amplified photoresist performance
Authors: Hinsberg W. , Houle F. A. , Hoffnagle J. , Sanchez M. , Wallraff G. , Morrison M. , Frank S.
Published: July 2002

The precise control of the exposure step provided by interferometric photolithography facilitates studies of chemically amplified resist physics, chemistry, and functional properties that are difficult using more conventional exposure techniques. We describe here the design and operating characteristics of a deep-ultraviolet interferometric lithography tool designed specifically for the study of high resolution chemically amplified resists. We provide an example of its use to evaluate resist response to controlled variations in aerial image contrast.
Microelectron gun with silicon field emitter
Authors: Endo Yasuhiro , Honjo Ichiro , Goto Shunji
Published: July 2002

We evaluated the characteristics of single Si field emitters (Si-FEs) from the perspective of their use in electron guns. Since the current fluctuation of Si-FEs strongly depends on the product of vacuum pressure P and emission current I, just as it does for conventional cold field emitters (CFEs), the mechanism of fluctuation was assumed to be similar to that of CFE. Such fluctuations are divided into two regions, the boundary was virtually equal to CFEs, at approximately 3×10−12 Pa A. However, unlike as for CFEs, the emission current of Si-FEs drops abruptly after a certain duration. We found that the integral of PI with the duration time (PIT integral) is almost constant (approximately 1×10−8 Pa A s) in various conditions and therefore assume that it correlates with the emission area of the emitter tip. The current leakage between emitter and gate electrode was found to be caused because of their small size. Responsible for this leakage are hydrocarbon contamination layers that were generated by emitted electrons or backscattered electrons on the surface of the insulating layer. Finally, we fabricated a miniaturized electron gun with Si-FEs and succeeded in obtaining SEM images with electrons that were emitted from the Si-FEs.
Study on characterizing fluorocarbon polymer films deposited on an inner surface during high-aspect-ratio contact hole etching using secondary ion mass spectroscopy
Authors: Liu Guo Lin , Ikegami Naokatu , Uchida Hidetsugu , Hirashita Norio , Kanamori Jun
Published: July 2002

Characterization of fluorocarbon films deposited on sidewall and bottom surfaces during high-aspect-ratio contact hole etching has been investigated by secondary ion mass spectrometry (SIMS). Very high-aspect-ratio contacts, with hole diameters ranging from 0.06 to 0.18 μm, were etched in 1 μm thick SiO2 films with polycrystalline Si hard masks by high density CHF3/CO or C4F8/O2/Ar plasma generated by a dipole ring-type magnetron reactive ion etching reactor. A series of SIMS studies for test element group chips with high density contact holes first reveal that the SIMS profiles obtained from the etched samples qualitatively exhibit a good measure of fluorocarbon profiles on the inner surfaces of the high-aspect-ratio contact holes. Quantitative evaluation is also discussed further. Fluorocarbon films on the sidewalls polymerized from CHF3/CO plasma show a great accumulation of C-rich films at an aspect ratio of around 4. With an increasing aspect ratio of more than approximately 8, the polymers are found to change from C-rich to F-rich films. On the other hand, fluorocarbon films on the sidewalls polymerized from C4F8/O2/Ar plasma are more uniform, much more fluorinated, and much thinner than those of the CHF3/CO plasma. Both polymers show a clear C pileup on the Si substrates at the bottom of the contact holes even for sub-0.1 μm contacts. This work successfully demonstrates the usefulness of the SIMS measurement for characterizing high-aspect-ratio contacts down to sub-0.1 μm diameters.
Properties and thermal stability of chemically vapor deposited W-rich WSix thin films
Authors: Wang M. T. , Lin Y. C. , Chuang M. S. , Chun M. C. , Chen L. J. , Chen M. C.
Published: July 2002

The tungsten-rich (Si/W atomic ratio less than 2.0) chemical vapor deposition (CVD)-WSix layer was found to be an efficient diffusion barrier against Cu diffusion. In this study, the properties and thermal stability of the W-rich WSix films chemically vapor deposited at various deposition temperatures, pressures, and SiH4/WF6 reactant gas flow ratios were investigated. With SiH4/WF6 flow rates of 6/2 sccm and a total gas pressure of 12 mTorr, the activation energy of the CVD process was determined to be 3.0 kcal/mole, and the film deposited at 250 °C has a Si/W atomic ratio of unity. The WSix films have a low residual stress, low electrical resistivity, and excellent step coverage. For the WSix layers deposited on Si substrates, the residual stress varies from 7 to 9×108 dynes/cm2 depending on the deposition temperature. The resistivity of the WSix films varies from 200 to 340 μΩ cm; higher deposition temperatures and SiH4/WF6 flow ratios resulted in higher film resistivities. The as-deposited amorphous WSix layer is thermally stable up to 600 °C; however, crystallization of the deposited film takes place at 650 °C and WSix was transformed into WSi2 phase when the WSix/Si structure was thermally annealed at temperatures above 650 °C.
Raman analysis and field emission study of ion beam etched diamond films
Authors: Park M. , McGregor D. R. , Bergman L. , Nemanich R. J. , Hren J. J. , Cuomo J. J. , Choi W. B. , Zhirnov V. V.
Published: July 2002

Discontinuous diamond films were deposited on silicon using a microwave plasma chemical vapor deposition system. The diamond deposits were sharpened by argon ion beam etching. Raman spectroscopy was carried out to study the structural change of the diamond after ion beam bombardment. It was found that amorphous sp2 carbon is produced as diamond is being sputtered by the Ar ion beam. The field emission turn-on field was also drastically lowered after sharpening, which, it is speculated, is caused by field enhancement due to change in geometry and/or structural changes (such as amorphization of crystalline diamond into graphitic or amorphous sp2 carbon) by Ar ion irradiation.
Ion implantation by vacuum arc plasmas
Authors: Schuelke T. , Witke T. , Brueckner J.
Published: July 2002

Plasma immersion ion implantation (PIII) is a promising new method to modify surfaces of materials by ion implantation. PIII works without expensive accelerators and therefore this method should have the potential for more applications than conventional ion accelerators. By this method, the samples are immersed into a plasma and high voltage pulses are applied to it for extracting ions from the plasma. Neither an extraction system nor other ion optics are needed. In addition to this great advantage, by using PIII, higher ion current densities and shorter implantation times are possible. The most commonly used plasma immersion arrangements extract the ion current from excited gases, especially from nitrogen. The vacuum arc is an option to produce hydrogen-free carbon plasmas or metal vapor plasmas. These plasmas extend the possibilities of the immersion ion implantation considerably. For an efficient use of PIII in thin film technology, ion sources with currents higher than 1.0 A are necessary. Moreover, the source has to be a compact tool. We have developed an ion source based on a pulsed high current arc. For the separation of the macroparticles, a magnetic plasma filter is used. The efficiency of the system was proved by implantation of carbon into silicon and niobium into a high-grade steel alloy. The implantation depths were 100 nm for carbon and 30 nm for niobium.
Adsorption of atomic hydrogen on the Si(001) 4×3-In surface studied by coaxial impact collision ion scattering spectroscopy and scanning tunneling microscopy
Authors: Ryu J. T. , Fuse T. , Kubo O. , Fujino T. , Tani H. , Harada T. , Saranin A. A. , Zotov A. V. , Katayama M. , Oura K.
Published: July 2002

Using coaxial impact collision ion scattering spectroscopy, scanning tunneling microscopy (STM), and low-energy electron diffraction techniques, we have investigated the interaction of atomic hydrogen with the Si(001) 4×3-In surface phase. During this interaction, Si–In bonds are broken and replaced by Si–H bonds. As a result, the 4×3 reconstruction is destroyed and In atoms form small clusters on the hydrogen-terminated Si(001) surface. The indium clusters are found to be not monocrystalline but, rather, polycrystalline. This is in contrast with other metal adsorbate/Si systems such as H/Ag/Si(111), H/Pb/Si(111), and H/In/Si(111) where metal atoms are known to form epitaxial monocrystalline islands. The size of the In clusters increases with increasing substrate temperature during hydrogen exposure of the 4×3-In phase. Using STM, we have confirmed that, as a result of atomic hydrogen interaction, the Si substrate becomes bare and forms the Si(001) 4×1-H phase, indicating that the underlying Si layer in the Si(001) 4×3-In surface phase is reconstructed with 4×1 periodicity. A structural model of the Si(001) 4×1-H surface has been proposed.
Molecular beam epitaxial growth and device performance of metamorphic high electron mobility transistor structures fabricated on GaAs substrates
Authors: Hoke W. E. , Lemonias P. J. , Mosca J. J. , Lyman P. S. , Torabi A. , Marsh P. F. , McTaggart R. A. , Lardizabal S. M. , Hetzler K.
Published: July 2002

Single and double pulse doped metamorphic high electron mobility transistor (MHEMT) structures have been grown on GaAs substrates by molecular beam epitaxy. A linear indium graded buffer layer was used to expand the lattice constant. Transmission electron microscopy cross sections showed planar interfaces. Threading dislocations were not observed along both cleavage directions. For a single pulse doped MHEMT structure with an In0.56Ga0.44As channel layer, the mobilities (10 030 cm2/V s at 292 K; 32 560 cm2/V s at 77 K) and sheet density (3.2×1012 cm−2) were nearly equivalent to values obtained for the same structure grown on an InP substrate. Secondary ion mass spectroscopy measurements of a double pulse doped structure indicated no measurable migration of the silicon doping pulses. MHEMT devices with 0.15 μm gates were fabricated, tested, and compared to GaAs pseudomorphic HEMT devices of the same geometries. Above 9 GHz, the MHEMT devices exhibited lower noise figure. From 3 to 26 GHz, the associated gain was 3 dB higher with the MHEMT devices. Also higher linearity performance was obtained with the MHEMT devices. At 4 GHz MHEMT linearity measurements yielded third order intermodulation distortion intercepts, IP3, of 36–39 dBm with linearity figure of merits of 60–90. Due to the significantly lower cost and more robustness of GaAs substrates compared to InP substrates, MHEMT technology is very promising for low cost manufacturing of low noise amplifiers.
Fabrication of a microcavity structure with a polyimide thin film prepared by vacuum deposition polymerization
Authors: Sakakibara Y. , Tani T.
Published: July 2002

A microcavity structure has been fabricated in which a polyimide layer with thickness on the order of the wavelength of light was sandwiched in between dielectric mirrors by using vacuum deposition polymerization (VDP). We deposited a 330-nm-thick polyimide layer through a polymerization reaction between two mutually reactive monomers evaporated onto a dielectric mirror consisting of TiO2/SiO2 multistacks. In the middle of the VDP process we deposited tris(8-hydroxyquinoline) aluminum (ALQ) so that a sublayer 30%-doped with ALQ was inserted within the polyimide layer. Upon the polyimide layer we coated a dielectric mirror consisting of Ta2O5/SiO2 multistacks. The mirrors were designed to have a broad high reflection band (stop band) with a reflectivity maximum of ∼90% at 530 nm. Fabrication of a microcavity was considered to be successful based on its optical properties. Within the stop band a sharp transmission band with a width of 8 nm appeared due to Fabry–Perot resonance. Correspondingly, ALQ photoluminescence became narrowed by the same width. We characterized the cavity resonance modes using a model considering penetration of the optical field into the dielectric layers.
Impact of plasma-enhanced chemical vapor deposited oxide characteristics on interconnect via resistance and device performance of four-transistor static random access memory with polysilicon load resistors
Authors: Lin C.-F. , Tseng W. T. , Feng M. S. , Wang Y. L.
Published: July 2002

By varying the gas ratio during the process of plasma-enhanced chemical vapor deposited (PECVD) SiOx, the composition of the oxide used as the intermetal dielectric (IMD) in the device is modified, and its impact on the integrity of the interconnect metal via hole and the stability of four-transistor (4-T) static random access memory (SRAM) with poly-Si load resistors is investigated. PECVD oxides using precursors of SiH4 and N2O under various gas ratios are adopted to manipulate the Si:O atomic ratio and other dielectric characteristics. An increase in the Si atomic percent in IMD film would induce a higher via resistance. Cross-sectional scanning electron microscopy of the post- etching via holes in a Si-rich IMD sample reveals a high amount of plasma-induced polymer formation around the via holes, which is perceived as the root cause of the dimensional decrease in via hole size and a corresponding increase in via resistance. As the gas ratio of SiH4/N2O increases, the IMD films become more Si rich with a higher refractive index and an a-Si-like dangling bond (⋅Si≡Si3) density. The a-Si-like dangling bonds (⋅Si≡Si3) in IMD films serve as effective trapping centers for hydrogen or moisture above the second polysilicon load resistor and hence protect them from attack by back-end process-induced mobile charges. The resistance of these poly-Si load resistors is maintained at a high level and device performance is secured. Thus, the high quality of a 4-T SRAM device with stable load resistance, could be realized, while maintaining a low interconnect metal via resistance.
Sensitivity analysis of the field emitter
Authors: Wei Lei , Baoping Wang , Hanchun Yin , Li Guohui
Published: July 2002

Many types of field emitters have been studied up to now to improve the emission current. However, only the ideal parameters are taken into account in some designs. In the fabrication process, the structural parameters of emitters may change. Therefore, it is useful to analyze the parameter sensitivity of the field emitter. This sensitivity should also be included in the defect function of the optimum design. In this article we propose a method to calculate the derivative of the electric field and emission current density versus geometrical parameters of emitter. This derivative can be used to represent the parameter sensitivity of the field emitter. Using this method, the sensitivities of some parameters in the diode and triode emitters are analyzed.
New method to prepare W–B+–N ternary barrier to Cu diffusion by implanting BF2+ ions into W–N thin film
Authors: Kim Dong Joon , Kim Yong Tae , Park Jong-Wan
Published: July 2002

Implanting 1×1017 BF2+ ions/cm2 with as low an energy as 40 keV into W–N thin films, W–B+–N thin layer was formed for the region near the surface of the W–N thin film. Experimental results reveal that thermal stability of the W–B+–N/W–N thin film and its barrier performance against Cu diffusion were improved compared to those of the W–N thin films after annealing at 600–800 °C for 30 min. These excellent properties of the W–B+–N/W–N barrier are due to the B+ ions to prevent nitrogen out-diffusion and to keep the W–B+–N/W–N thin film in an amorphous phase after annealing at 800 °C because the grain growth of W or W–N and the Cu diffusion were suppressed by the B and N impurities in the amorphous thin film.
Pyroelectronics: Novel device concepts based on nitride interfaces
Authors: Zandler G. , Majewski J. A. , Vogl P.
Published: July 2002

A key property of nitrides is their large spontaneous and piezoelectric polarization fields that allow significant tailoring of the carrier dynamics and optical properties of nitride devices. In this article, based on first-principles calculations of structural and electronic properties of bulk nitrides and their heterostructures, we investigate the potential of this novel material class for modern device applications by performing self-consistent Monte Carlo simulations. We demonstrate that the internal electric fields have a significant and favorable influence on the transistor characteristics.
In situ electrical determination of reaction kinetics and interface properties at molecular beam epitaxy grown metal/semiconductor interfaces
Authors: Chen L. C. , Palmstro/m C. J.
Published: July 2002

In situ patterning and electrical characterization are used to study the electrical properties, reaction kinetics, and interface properties during reactions at Ni/n-GaAs interfaces. Ni contacts were formed in situ by deposition through a removable molybdenum shadow mask onto a GaAs(100) c(4×4) As-rich surface. Annealing at 300 °C resulted in Ni3GaAs formation. Subsequent exposure of the Ni3GaAs to an As4 flux at 350 °C resulted in the formation of NiAs at the surface and the epitaxial regrowth of GaAs at the NixGaAs/GaAs interface. The GaAs regrowth thickness and the regrown GaAs electrical properties were determined electrically by in situ capacitance–voltage and current–voltage measurements. An interlayer model was applied to explain the Schottky barrier height discrepancy between capacitance–voltage and current–voltage measurements for metal/GaAs contacts with regrown GaAs. The model predicts that the regrown GaAs interlayer is p type with a hole concentration of ∼3×1015 holes/cm3.
Control of spatial and transient temperature trajectories for photoresist processing
Authors: El-Awady Khalid , Schaper Charles D. , Kailath Thomas
Published: July 2002

Spatial and transient control of temperature trajectories by a new thermal cycling module is presented, with a focus on photoresist processing applications for semiconductor wafers and quartz reticles. In the proposed unit, the bake and chill steps are conducted sequentially within the same module without any substrate movement. The unit includes two heating sources. The first is a circulating fluid which can be switched between hot and cold reservoirs and serves as the dominant means for heat transfer. The second is a set of thermoelectric devices which are used to provide a distributed amount of heat to the substrate for uniformity and transient temperature control. Experimental data is provided to demonstrate temperature uniformity during both transient and steady state operation. The flexibility of the system to develop new processing temperature trajectories is presented.
Extreme ultraviolet lithography at Carl Zeiss: Manufacturing and metrology of aspheric surfaces with angstrom accuracy
Authors: Handschuh H. , Fröschke J. , Jülich M. , Mayer M. , Weiser M. , Seitz G.
Published: July 2002

Experiments were carried out to manufacture aspheric surfaces to extreme ultraviolet (EUV) standards, within the European Project extreme UV concept lithography development system (EUCLIDES). Results of the fabrication of mirror 2 of the Sandia National Laboratory 5 × ring-field system will be discussed. A residual rms surface error of 0.14 nm and a roughness of 0.2 nm have been achieved. These results are very promising for the realization of future EUV systems.
EUCLIDES: European EUVL Program
Authors: Benschop Jos P. H. , van Dijsseldonk Anton J. J. , Kaiser Winfried M. , Ockwell David C.
Published: July 2002

In August 1998 a new European research program named extreme ultraviolet concept lithography development system (EUCLIDES) was started. The program, headed by ASM Lithography (ASML), partnered by Carl Zeiss and Oxford Instruments, is evaluating extreme ultraviolet lithography (EUVL) as a viable lithographic solution for resolutions of 70 nm and smaller. In this article a summary of program objectives and status will be given, followed by an overview of recent highlights obtained by the various program partners and subcontractors. Results of the system architecture study will be presented. These include the (preliminary) results of the comparison study between laser plasma and synchrotron sources in terms of throughput and cost-of-ownership. A novel technique will be presented which mitigates resist outgassing without the need of a window between the projection optics and the wafer. Using this idea the EUV flux on the wafer can be doubled hence increasing the throughput. An EUVL test bench, containing an EUV interferometer is under construction. The test bench contains an operational water droplet laser plasma source. Experimental results will be presented. Part of the program focuses on optical and mechanical design, substrate fabrication, metrology, and multilayer coatings. Most recent results on coatings and optical substrate manufacturing will be presented.
Nondestructive picosecond-ultrasonic characterization of Mo/Si extreme ultraviolet multilayer reflection coatings
Authors: Pu Nen-Wen , Bokor Jeffrey , Jeong Seongtae , Zhao Ri-An
Published: July 2002

We have used noncontact, nondestructive picosecond-ultrasonic techniques to characterize Mo/Si multilayer reflection coatings for extreme ultraviolet (EUV) lithography. Using our alternating-pump technique, we successfully excited and detected the two lowest frequency localized acoustic-phonon surface modes. By measuring their vibration frequencies simultaneously, we can extract the two key parameters for EUV reflector performance: d (bilayer thickness) and Γ (thickness ratio of Mo layer to the bilayer) of the Mo/Si multilayers. To demonstrate the utility of this technique, we measured the surface-mode frequencies and extracted the values of d and Γ for six mirrors. Good agreement with the results of at-wavelength EUV reflectometry was found. Damage to coatings caused by the pump and probe laser beams was also studied, and found to be negligible given our data-acquisition time.
Highly accurate cell projection mask for applications to sub-130 nm patterning
Authors: Kim Cheol-Kyun , Hur Cheol , Kim Young-Sik , Baik Ki-Ho , Choi Il-Hyun
Published: July 2002

In this article, we introduce the constraints of cell projection mask (CPM) design for application to sub-0.13 μm patterning and the modified fabrication technology for the highly accurate CPM. First, we investigated the constraints of CPM design such as Coulomb interaction and proximity effect. Especially, in order to reduce beam blur effect, we applied mask bias and optimized shot size that could be obtained by calculated space margin and experiment. Second, we made highly accurate CPM using modified fabrication technology, which included deep trench etching process with oxide barrier, the stacked protection layer, and effective cleaning process. The minimum feature size achievable in this technology is 1 μm, corresponding to 0.04 μm on a wafer due to 1/25 reduction ratio of cell projection e-beam lithography system. Using CPM made by above process, we successfully defined 0.08 μm lines-and-spaces and 0.1 μm contact hole patterns with a standard deviation of 0.005 μm. In addition, we also compared the lithographic performance of the CPM samples with 20- and 10-μm-thick diaphragms. According to our results, thin CPM has more advantages than a thick one in view point of fabrication and low electron transmittance of sidewall.
Carrier profile of the Si-doped layer in GaAs fabricated by a low-energy focused ion beam/molecular beam epitaxy combined system
Authors: Yanagisawa Junichi , Goto Takayuki , Hada Takuo , Nakai Masaya , Wakaya Fujio , Yuba Yoshihiko , Gamo Kenji
Published: July 2002

Buried Si-doped layers in GaAs were fabricated by low-energy focused Si2+ ion beam (Si FIB) implantation in GaAs grown by molecular beam epitaxy (MBE) and successive overlayer regrowth using an FIB/MBE combined system. Carrier profiles were measured by means of a capacitance–voltage profiling technique. It was found that doped layers with a carrier concentration of 1.2×1012 cm−2 and a width (full width at half maximum) of 23 nm were formed without postannealing for the 200 eV Si implantation at a dose of 7×1012 cm−2. After postannealing, the doping efficiency was improved and the width became narrower. At a dose of 1.4×1013 cm−2, narrower carrier distribution with higher peak density was observed although the total doping efficiency was decreased. In contrast a deeply depleted layer was formed and no carriers were observed for implantations at an energy higher than 400 eV before the postannealing. This may be because damage is significantly reduced for the lower implantation energy.
Lithographic projectors with dark-field illumination
Authors: White D. L. , Cirelli R. A. , Spector S. J. , Wood O. R.
Published: July 2002

A new resolution enhancement technique for photolithography that allows the illumination of each and every feature on a reticle to be customized is described. Customization is important because different feature types, e.g., contact holes, isolated lines, dense gratings, etc., must be illuminated differently if the best possible image at the largest depth-of-focus is to be produced. Examples of the imaging performance of a conventional lithographic projector retrofitted with dark-field illumination for three feature types commonly encountered in semiconductor lithography are presented.