bluuebunny/crossref_metadata_2025 huggingface dataset:
PREVAIL: Dynamic correction of aberrations
Authors: Gordon M. S. , Enichen W. A. , Golladay S. D. , Pfeiffer H. C. , Robinson C. F. , Stickel W.
Published: July 2002

The curvilinear variable axis lens concept for the PREVAIL proof-of-concept (POC) system, and its practical implementation have been described in a previous publication [H. C. Pfeiffer et al., J. Vac. Sci. Technol. B 6, 2844 (1999)]. The objective of this article is to show experimental results regarding the dynamic compensation of the deflection-dependent focus and astigmatism aberration control in the projected subfield. The POC system contains a plurality of dynamic correction elements in the imaging section between reticle and wafer. Using a pair of properly positioned stigmators, we have demonstrated nearly independent control of feature astigmatism (image quality) and subfield distortion (shape astigmatism). In this article, we will describe a technique that was used to control the subfield distortion. In addition, using three dynamic focus coils, and an inverted sensitivity matrix approach, we have also demonstrated independent control of the subfield magnification, rotation, and axial focus.
Calculation of surface potential and beam deflection due to charging effects in electron beam lithography
Authors: Lee Yongjae , Lee Woojin , Chun Kukjin
Published: July 2002

In this article, we describe the analysis procedures of charging effects and calculation results of surface potential and beam deflection in electron beam lithography. Monte Carlo simulation is performed to obtain the charge distribution in e beam resist. A focused (Gaussian) and a flood beam are considered for beam shapes of the exposure system. The effects of discharging due to electron beam induced conductivity are included in the analysis. The Poisson equation is solved for the potential distribution by using the simultaneous overrelaxation method. The iteration technique is used for the convergence of the potential. With the given potential distribution, beam deflection is calculated using the fourth order Runge–Kutta integration algorithm. Comparison of the values of the surface potential obtained by simulations with experimental results by Pease' group at Stanford University show similar shapes between them. We also have applied this work to a SCALPEL mask with a thin silicon nitride membrane. This work will be helpful for the exact understanding and avoidance of charging effects, when an electron beam is irradiating an insulator.
Resist profile characteristics caused by photoelectron and Auger electron blur at the resist–tungsten substrate interface in 100 nm proximity x-ray lithography
Authors: Seo Younghun , Lee Changhwan , Seo Yongduk , Kim Ohyun , Noh Hyunpil , Kim Heesang
Published: July 2002

The replicated resist pattern characteristics caused by photoelectrons and Auger electrons generated from the W substrate were investigated for 100 nm proximity x-ray lithography. In addition, simulations for a hard x-ray spectrum having 2.36 keV average energy were performed to investigate the substrate electron effects in hard x-ray lithography. In the experiments, it was found that the secondary electrons from the W substrate caused undercut and footing of resist profiles at the resist–substrate interface. Several buffer layers with varying thicknesses were tested to reduce the photoelectron effects from the W substrate. The best thickness of the buffer layers for a good resist pattern profile was discovered to be >30 nm. Furthermore, the experimental results were quantitatively compared to the results from computer simulations using the Monte Carlo method. For hard x rays, we predict that the exposure latitude is worse on both W and Si substrates.
Evaluation of alternative development process for high-aspect-ratio poly(methylmethacrylate) microstructures in deep x-ray lithography
Authors: Malek Chantal Khan , Yajamanyam Sasi
Published: July 2002

The development of very thick commercial sheets of poly(methyl methacrylate) (PMMA) resist patterned by deep x-ray lithography was investigated. The development characteristics were explored, with the alternative methyl-iso-butyl-ketone (MIBK)-based developer systems, MIBK and MIBK/ iso-propyl-alcohol (IPA) 1:3, being compared with the “GG” developer system (2-butoxyethoxy-ethanol, morpholine, 2-aminoethanol, and water) more generally used. In particular, the influence of various parameters were studied: PMMA characteristics (resist thickness, pre-exposure thermal treatment), exposure conditions (x-ray incident energy, dose at the bottom of the resist, rate of dose deposition, distribution of dose inside the resist), development conditions (temperature, megasonic-assistance, length of cycle into developer and rinse baths), postexposure treatments (storage, thermal treatment), etc. The study also focused on surface finish of the parts corresponding to different exposure and development conditions. Using MIBK/IPA megasonic assisted development and postexposure treatment at 40 °C resulted in the best conditions, faster development rate, as well as smoother developed surfaces.
Vacuum gauge system with a self-compensator for photoelectrons produced in the SPring-8 storage ring
Authors: Saeki Hiroshi , Aoki Tsuyoshi , Yonehara Hiroto , Momose Takashi
Published: July 2002

Some Bayard–Alpert gauges mounted on crotch chambers in the SPring-8 storage ring have indicated minus pressures or lower pressures due to influx of photoelectrons to their collectors. In order to measure the pressure correctly in such a vacuum environment, the authors proposed a vacuum gauge system which self-compensates for photoelectrons from the external vacuum environment. The gauge has an added correcting electrode which detects the photoelectron current, only from the external environment, and can show the real pressure by compensating the ion current measured at the collector of the gauge. The proposed gauge system was developed and tested in an environment of excess electrons using a heater and in an environment of excess ions using an electron gun. In the pressure of the range of 10−7–10−6 Pa, the gauge system showed the real pressure correctly by compensating for charged particles from the external vacuum environments at the SPring-8 storage ring.
Influence of sputtering pressure on physical structure of AlN thin films prepared on Y-128° LiNbO3 by rf magnetron sputtering
Authors: Wu Long , Wu Sean , Song Hong-Tie
Published: July 2002

c-axis-oriented aluminum nitride (AlN) films were successfully prepared on a Y-128° LiNbO3 substrate by rf magnetron sputtering. The dependence between sputtering pressures and the physical structures of the films (crystalline structure and micromorphology) was investigated by x-ray diffraction (XRD) and atomic force microscopy (AFM). The result showed that the higher c-axis-oriented AlN films appeared at lower sputtering pressures and the uneven grain structures existed as multioriented XRD patterns appeared in the high sputtering pressure region (5–9 mTorr). The best orientation and microstructure of the films was prepared at 3 mTorr.
Analytic evaluation of the intensity point spread function
Authors: Gallatin Gregg M.
Published: July 2002

The intensity point spread function (PSF) for geometric imaging such as occurs in a projection electron system like SCALPEL is derived analytically from the ray aberration coefficients. The results show that, as expected, the PSF for ordinary aberrations has a finite radius and is not Gaussian. Hence blur estimates, which are often based on assuming a Gaussian PSF and computing the root-sum-square or “rss” of the separate blur radii will generally overestimate the true aberration blur. Global space charge acts like an electrostatic lens and hence its effects can be included in the PSF calculation as well. The net PSF can be convolved with an object to produce an accurate representation of the image. The convolution integral can also be performed first which yields the image intensity distribution directly in terms of the aberrations.
Enhancement of resist resolution and sensitivity via applied electric field
Authors: Cheng Mosong , Croffie Ebo , Yuan Lei , Neureuther Andrew
Published: July 2002

This article presents a methodology for enhancing the resist sensitivity and resolution based on confining the photoacid drift/diffusion by external electric field. An alternating electric field applied to the resist film during postexposure bake can enhance the photoacid drift in the vertical direction, reduce the bake time, and thereby confine the lateral acid diffusion. A mathematical model is presented and a rigorous solution is obtained in the case of Fickean diffusion and constant electric field. The experiments were conducted on UVIIHS resist with a JEOL electron-beam exposure tool. The scanning electron microscope pictures show that electric-field enhanced postexposure bake (PEB) can reduce the PEB time requirement by 30%, and at the same time, improve the sharpness of two-dimensional corners and increase the verticality of resist sidewalls. Electric-field-enhanced PEB also significantly improves the tolerance of overexposure and provides better critical dimension control. It is estimated that it reduces the lateral acid diffusion length by about 70 nm, or 50%.
Field emission cathode array with self-aligned gate electrode fabricated by silicon micromachining
Authors: Barth W. , Debski T. , Shi F. , Hudek P. , Kostic I. , Rangelow I. W. , Biehl S. , Iwert T. , Grabiec P. , Studzinska K. , Mitura S. , Bekh I. I. , Lushkin4 A. E. , Il’chenko L. G. , Il’chenko V. V. , Haindl G.
Published: July 2002

An electron emission behavior of field emission arrays based on a new bulk/surface silicon micromachining method of fabrication was studied. The process developed is simple and allows self-aligned gate electrode formation. The field emission of the emitter tips is enhanced by a 50 nm diamond-like carbon (DLC) film formed by chemical vapor deposition. Detailed Raman, Auger, and transmission electron microscopy (TEM) investigations of the deposited DLC films will be presented. Results about the presence of nanocrystalline diamond obtained with Raman spectroscopy could not be confirmed by the TEM investigations (the nanocrystalline diamond is smaller than 10 nm).
Measurement and simulation of temperature dynamics under electron beam
Authors: Babin S. , Gaevski M. E. , Konnikov S. G.
Published: July 2002

An original in situ technique was developed to measure the temperature rise and decay of a material under electron-beam (e-beam) irradiation. The technique uses the effect of temperature rise on the electrical conductivity of high-temperature superconductors that are prefabricated as microbridges. This temperature sensor was measured to have a sensitivity greater than two orders of magnitude more than a thin-film thermocouple. A stroboscopic technique ensured nanosecond temporal resolution, and the size of the microbridge allowed for micrometer-scale spatial resolution. These measurement ranges are important for practical e-beam lithography. Experimental results were compared with results simulated by the TEMPTATION (temperature simulation) software, and qualitative agreement of simulated and measured results was found. Factors influencing the accuracy of the temperature measurement are discussed.
Fabrication of ferromagnetic/semiconductor waveguide structures and application to microwave bandstop filter
Authors: Wu W. , Lee C. C. , Tsai C. S. , Su J. , So W. , Yoo J. , Chuang R.
Published: July 2002

We studied the propagation of a microwave signal in Fe/Ag–GaAs waveguide structures. In an ultrahigh frequency ferromagnetic resonance measurement, maximum coupling and thus strong attenuation of the microwave power occur near the ferromagnetic resonance frequency fres of Fe film. Magnetostatic wave (MSW)-based microwave devices have been achieved in the form of a bandstop filter utilizing single crystal Fe/Ag structures grown on GaAs (100) substrate. MSW-based microwave devices possess the unique capability of electronically tunable operating carrier frequency via a magnetic field. The peak absorption frequency for an Fe easy axis case has been tuned in a range from 10.6 to 36 GHz. For a hard axis case, the tuning frequency ranges from 8 to 22 GHz. The experimental results show that Fe/Ag–GaAs waveguide structures are very promising systems for use in future microwave magnetoelectronics as they have well-defined magnetic properties, as well as favorable electrical properties.
Basic constraints for a multibeam lithography column
Authors: Mankos M. , Coyle S. , Fernandez A. , Sagle A. , Owens W. , Sullivan J. , Chang T. H. P.
Published: July 2002

A 50 keV multibeam test bed incorporating a photocathode and multiple modulated light beams has been developed and constructed. The column allows for a detailed evaluation of both the photocathode sources and the electron optics for sub-100 nm lithography applications and is designed to reduce electron–electron (e–e) interactions. The basic constraints determining the performance of the multibeam electron column are discussed. Results have been obtained using gold photocathodes at beam energies varying from 10 to 50 kV, allowing the experimental evaluation of key design parameters.
Fermi contours and adsorbate phonon anomalies for Li/Mo(110) and Li/W(110)
Authors: Rotenberg Eli , Kevan S. D.
Published: July 2002

Angle-resolved photoemission was used to measure the Fermi contours of surface-localized states on the Mo(110) and W(110) surfaces with varying amounts of adsorbed lithium. In analogy with recent results for hydrogen adsorbed on the same surfaces, we find that the contours may have sufficient nesting to drive a surface phonon (Kohn) anomaly. The nesting vector along Γ̄→H̄ (parallel to the Σ̄ azimuth) on Mo(110) at monolayer coverage is measured to be 1.06±0.05 Å−1, which is compared to recent phonon measurements by electron energy-loss spectra. We also report the variation of this nesting vector as a function of coverage, and show that a more complete understanding of the electron–phonon coupling on these surfaces might be obtained from coverage-dependent measurements of surface phonon dispersion relations. Finally, our results suggest there is even better nesting along the Γ̄→S̄ direction and that a more pronounced Kohn anomaly might be observed there.
Near-edge valence-band structure of amorphous hydrogenated Si–C thin films characterized by Auger and photoemission processes
Authors: Lee Moon-Hwan , Ohuchi Fumio S.
Published: July 2002

A core–valence–valance Auger transition contains information about the local valence electronic structure of the probed atom. This is due to the direct coupling of the core and valence levels involved in the Auger process. In this work, a combined use of the Auger and photoemission processes to study near-edge valence-band structures of amorphous hydrogenated silicon carbide is described. Experimentally, a-Si1−xCx:H thin films were fabricated by plasma-enhanced chemical-vapor deposition using methylsilane precursors. Hydrogen was incorporated in the plasma to control the carbon composition from 0.36 to 0.83. The valence-band edge in the Si-rich region (x<0.6) was lead by both Si 3p and C 2p states, while the C 2p states from the C–C bonding configuration dominates the near-edge structure in the C-rich region (x⩾0.6). Due to the large difference in the photoionization cross sections for Si 3p and C 2p, the valance spectrum measured from x-ray photelectron spectroscopy failed to represent the near-edge structure in a-Si1−xCx:H.
Fabrication of triode diamond field emitter arrays on glass substrate by anisotropic conductive film bonding
Authors: Lee Jong Duk , Cho Euo Sik , Kwon Sang Jik
Published: July 2002

Gated pyramid-shaped polycrystalline diamond field emitter arrays (FEAs) were fabricated by microwave plasma chemical vapor deposition and the transfer mold technique. The FEAs were fabricated with various standard integrated circuit technologies and micromachine electromechanical system technologies; thermal oxidation, chemical wet etch, sputtering, and glass-to-metal bonding technique by using anisotropic conductive film (ACF). As a result of ACF bonding, thin flat film type FEAs were simply realized on an indium tin oxide coated glass substrate without the necessity of an additional cathode contact. Fabricated diamond FEAs were electrically characterized in triode configuration and an anode current of 237 nA was obtained at the gate bias of 120 V.
Enhanced diffusion as a mechanism for ion-induced damage propagation in GaN
Authors: Haberer E. D. , Chen C. H. , Hansen M. , Keller S. , DenBaars S. P. , Mishra U. K. , Hu E. L.
Published: July 2002

Although GaN is a chemically inert, thermally stable material, it has demonstrated sensitivity to ion damage generated by dry etch processes such as reacting ion etching and inductively coupled plasma etching. Recombination-enhanced diffusion is an important mechanism which has been observed in other III–V semiconductor systems. In this study we examine the possibility of enhanced diffusion in GaN using quantum well (QW) probe structures. The deeper QWs (750 and 1000 Å deep) showed a steady decrease in relative photoluminescence (PL) intensity with time, providing evidence of the cooperative effects of channeling and defect diffusion in deep etch damage propagation in GaN. In contrast, shallow QWs (150 and 250 Å from the surface) showed a slight decrease followed by a gradual increase in relative PL intensity with time which was explained by defect annihilation. Exposure to above band gap illumination, used to simulate and enhance carrier generation during etch, appears to speed defect annihilation in high defect concentration regions resulting in an increase in QW luminescence, where as in lower defect concentration areas, above band gap illumination does not appear to significantly alter QW luminescence. We attribute this difference in behavior to a difference in diffusion constant. The diffusion constant in less damaged regions may be much lower than that of the highly damaged material.
Scanning tunneling microscopy study of the molecular arrangement of meta- and para-xylene on Pd(111)
Authors: Futaba D. N. , Landry J. P. , Loui A. , Chiang S.
Published: July 2002

We have performed an experimental study of meta- and para-xylene isomers, C6H4(CH3)2, adsorbed on Pd(111). Using scanning tunneling microscopy we imaged the characteristic surface structures and investigated the molecular ordering for meta- and para-xylene. A triangular shape characterized the meta-xylene, and the para-xylene showed a distinctive diamond shape. Both isomers showed some propensity to order and a correlation between azimuthal orientation and the close-packed directions of the metal.
Performance improvement of gated silicon field emitters with a thin layer of boron nitride
Authors: Busta H. , Furst D. , Pryor R. , Li Lihua
Published: July 2002

Fully processed boron implanted n−-gated silicon tip arrays were coated with about 50 nm of carbon-doped BN by reactive sputtering at 450 °C. The current–voltage characteristics of the BN coated 6460 tip arrays shifted by about 40–60 V towards lower gate voltages for emission currents of about 100 μA. From the Fowler–Nordheim analysis of representative arrays, the Φ3/2/β ratio decreased from 2.5×10−5 eV3/2 cm to 8.9×10−6 eV3/2 cm for the coated tips. This decrease is attributed to an increase in the field conversion factor β. The arrays improve in performance when operated at 40 mA/cm2 for about 100 h in direct current mode and show a factor of 6 increased pressure tolerance towards ion bombardment as compared to the bare silicon emitters.
Luminescence characteristics of green phosphors with dwell times for field emission display design
Authors: Jang J. E. , Kim J. W. , Lee S. J. , Kwon N. H. , Jin Y. W. , Park S. H. , Jung J. E. , Lee N. S. , Kim J. M.
Published: July 2002

Luminescence characteristics of green phosphors were investigated for different dwell times and anode biases for optimal designing of field emission displays. At a medium anode voltage of 2.5 kV, the brightness was decreased steeply with a lower dwell time (a higher device resolution). At higher anode biases, however, the brightness was reduced slower than calculated from a given dwell time. Such a relationship between the brightness and the dwell times seems to be explained by excitation profile of phosphor at different anode biases. For high-resolution field emission displays, it is considered that an engagement of higher anode biases is more beneficial to excellent images in terms of brightness.
Investigation of the penetration of atomic hydrogen from the gas phase into SiO2/GaAs
Authors: Kagadei V. A. , Nefyodtsev E. V. , Proskurovsky D. I.
Published: July 2002

A comparison experiment has been performed to study the hydrogenation of GaAs samples coated with a thin film of SiO2 (5 nm) and thin-film vanadium samples in a flow of atomic hydrogen produced by a source based on a reflected arc discharge with a hollow cathode and a self-heating electrode. An increase in discharge current I results in an increase in the concentration of atomic hydrogen in the gas phase, NAH, and in a corresponding increase in the atomic hydrogen content (dose), QAH, dissolved in vanadium samples. For GaAs samples, the situation is different. At low discharge currents, an increase in current results in an increase in NAH and in a corresponding increase in QAH. However, beginning from some current I*, further increase in current and in NAH decreases QAH. This suggests that the value of QAH is more dependent on the probability of the penetration of hydrogen atoms into the solid, F, than on NAH. It has been supposed that F decreases substantially as the hydrogen atom energy decreases with increasing discharge current. Another reason for the observed phenomenon may be the formation of a near-surface diffusion barrier of immobile hydrogen molecules occupying interstitials and preventing hydrogen atoms from penetrating the bulk of the sample.
Relationship between deprotection and film thickness loss during plasma etching of positive tone chemically amplified resists
Authors: Mahorowala A. P. , Medeiros D. R.
Published: July 2002

Positive tone chemically amplified (CA) resists have demonstrated the sensitivity, contrast, and resolution necessary to print state-of-the-art subwavelength features using 248 nm and more recently 193 nm lithography. These materials are also being considered for printing sub-100 nm features with 157 nm and next-generation lithography technologies such as extreme ultraviolet and electron beam projection lithography. The basis for solubility differential and image formation in these resists is the acid catalyzed deprotection of labile protecting groups of an inherently base soluble polymer. The deprotection is effected by the photochemical generation of strong acid during the exposure process. Such acid-catalyzed deprotection reactions can also occur in unexposed resist areas when etched in a plasma. This can be due to UV exposure, high-energy ion bombardment, elevated substrate temperatures, or interaction of the resist surface with plasma species to form acidic moieties. Deprotection has been associated with resist mass loss and film shrinkage during plasma etching, leaving inadequate masking material for the entire etch step. In this article, we report the film thickness loss of several unexposed CA resists as a function of etch time in a variety of plasmas and correlate these data with film composition, monitored by Fourier transform infrared spectroscopy. These results are compared with theoretical predictions based on generally accepted deprotection mechanisms. Our findings indicate that the “acidic” nature of certain plasmas such as Cl2/O2 can result in deprotection in the resist film, even in the absence of a photoacid generator. Additionally, the data suggest that the nature of the resist polymer and, in turn, the identity of the deprotection products directly influence resist mass loss and etch rate linearity, both of which can be controlled by careful selection of resist materials.
Mold-type field-emission array fabrication by the use of fast silicon etching
Authors: Dziuban Jan , Górecka-Drzazga Anna
Published: July 2002

The SiC sharp-emitter field-emission arrays have been produced by a transfer-mold technique. An alternate method of microwave-enhanced wet anisotropic silicon etching has been applied to the fabrication of field-emission arrays. Supporting, back side (100)-oriented, 380 μm thick silicon substrate has been etched away six times faster as compared to the thermally activated, standard KOH etching process. The alternate etching method may be successfully applied to any existing transfer-mold fabrication procedures.
Effect of catalyst on growth behavior of carbon nanotube synthesizing by microwave heating thermal chemical vapor deposition process
Authors: Chen Shi-Cheng , Shih Liang-Yuan , Chang Yu-Chen , Tu George-C , Lin I-Nan
Published: July 2002

A modified chemical vapor deposition process, which utilizes a susceptor to absorb the microwave and to self generate the heat, for heating up the Si substrate, was used for growing carbon nanotubes (CNTs). The advantage of such a process is that the deposition chamber can be maintained at around room temperature with only the substrates localized heated, such that the deposition temperature can be more precisely controlled. The influence of the pretreatment process for catalyst-coated Si substrates on growth behavior of CNTs and the related electron field emission properties were systematically examined. Among the form of catalyst used, the Fe(NO3)3–ethythersilicate mixture performs much better than the dc sputtered Fe films. The higher the concentration of Fe species in the catalyst mixture, the denser the CNTs formed on the substrates, resulting in better field emission properties. Thus grown CNTs can be turned on at a very low field (E0≅0.78 V/μm), achieving a very large emission current density (Je≅13 mA/cm2) at 5.5 V/μm applied field.
Data requirements and communication issues for advanced process control
Authors: Markle Richard J. , Coss Elfido
Published: July 2002

Data streams and communication issues are the most critical areas for successful advanced process control (APC) programs. These areas are vital for both APC run-to-run controllers and fault detection and classification (FDC) systems used for high volume manufacturing applications in the semiconductor industry. All APC systems rely on data streams to make their process changes, to keep the process on target and in control, and to otherwise signal a need for engineering involvement to make similar corrective actions. The access to, communication of, and reliability and integrity of these data streams are essential to all APC programs. APC run-to-run controllers use the data to make changes in the process. FDC systems focus on predicting pending equipment- or process- related problems or detecting them quickly when they occur. The inability to access the needed data stream can prohibit the use of APC run-to-run controllers or FDC systems on critical process operations. Worse yet, the use of unreliable or corrupted data can cause undesirable consequences. In order to better capitalize on the improvements demonstrated with APC run-to-run controllers and FDC systems, end users have often had to create their own communication and data processing methods. The first decade of the 21st century will place increased demands on process and metrology equipment manufacturers, APC software and hardware suppliers, and APC programmers. Improvements in these areas through the use of industry standards and best known methods could greatly accelerate the APC field. Wafer-to-wafer and within wafer process control could be essential for 300 mm wafer processing; large flat panel processing will also need these improvements. We will discuss examples that Advanced Micro Devices experienced in Fast atom beam-25 within the past year. The case studies relate to complex, but necessary, methods to get the data we need for a FDC system and the role of metrology data on APC run-to-run controllers. Data and communication requirements for the next three to five years will also be discussed. The increased demands on the current process and metrology systems will increase as we begin to use new and alternative technologies to support more advanced APC strategies.
Micro-electro-mechanical system fabrication technology applied to large area x-ray image sensor arrays
Authors: Daniel J. H. , Krusor B. , Apte R. B. , Mulato M. , Van Schuylenbergh K. , Lau R. , Do T. , Street R. A. , Goredema A. , Boils-Boissier D. C. , Kazmaier P. M.
Published: July 2002

Micromachining has potential applications for large area image sensors and displays, but conventional micro-electro-mechanical system (MEMS) technology based on crystalline silicon wafers cannot be used. Instead, large area devices use deposited films on glass substrates. This presents many challenges for MEMS, both with regard to materials for micromachined structures and to integration with large area electronic devices. We are exploring the novel thick photoresist SU-8 as well as plating techniques for the fabrication of large area MEMS. As an example of its application, we have employed this MEMS technology to improve the performance of an amorphous silicon based x-ray image sensor array. SU-8 is explored as the structural material for the x-ray conversion screen and as a thick interlayer dielectric for the thin film readout electronics of the imager. Plating techniques are employed to metallize the deep contact vias in SU-8. Processing challenges that are particularly important for large area fabrication will be addressed.
Plasma oxidation as a tool to design oxide films at low temperatures
Authors: Schennach R. , Grady T. , Naugle D. G. , Parga J. R. , McWhinney H. , Cocke D. L.
Published: July 2002

Interfacial oxidation, an established approach to produce surface thin films for catalysts, corrosion, ware protective coatings and electronic structures is currently performed by thermal, anodic, and plasma methods. Fundamental physical-chemical models that can allow film design, particularly on alloys are lacking and plasma oxidation is the least studied of these methods. In this work, plasma oxidation of three CuZr alloys (CuZr2, CuZr, and Cu51Zr14) has been studied using x-ray photoelectron spectroscopy and depth profiling methods. The dependence of the resulting oxide film on alloy composition and sample temperature during plasma oxidation is investigated. In contrast to thermal and electrochemical oxidation which lead to the formation of a zirconium oxide film, plasma oxidation leads to the formation of a copper oxide or metallic copper overlayer depending on temperature and copper concentration in the bulk. It is shown that plasma oxidation can be used to design oxide films at room temperature, which require high temperatures using thermal oxidation and are not achievable by anodic oxidation.
Vacuum characteristics of sprayed metal films
Authors: Minato Michio , Iwamoto Hideo
Published: July 2002

The need to reduce particles in semiconductor equipment and data storage equipment is in high demand. In recent years, barrier and glue layers on shields have been used to reduce particles generated in physical vapor deposition equipment. For this purpose, spray coatings are applied to shields. Although the sprayed metal films are exposed to vacuum in a vacuum chamber, their vacuum characteristics have seldom been investigated. The conventional spray coatings are usually done under atmospheric conditions. In order to obtain a layer that has a better vacuum characteristic, spray coating in a chamber filled with an inert gas was developed. Outgassing characteristics of sprayed aluminum films and titanium films were investigated by using the conductance modulation method. A sprayed metal film produced in an inert gas system showed a lower outgassing rate than that produced in an atmospheric condition.
Novel interface modification technique applied from the top of a coated layer
Authors: Yoshitake M. , Aparna Y.-R. , Yoshihara K.
Published: July 2002

A technique to modify the interface after the formation of the interface is needed either because of some process requirement or because of a change in the required material function over time. In this article we present a novel technique to form an intermetallic compound at the interface between a coating layer and the substrate by depositing a specific metal film on the top of a coating layer. Based on the property of the intermetallic compound, the interface is modified. Experimentally, the diffusion and interfacial reaction of specimens with a top-film/middle-film/substrate structure were investigated. With proper choice of the top-film metal, the top-film metal diffuses inward without any significant reaction with the middle film and concentrates at the interface between the middle film and the substrate followed by formation of an intermetallic compound. We discuss conditions for obtaining the above phenomena and present a general guide for choosing the top-film metal. Key factors are (1) the segregation tendency of the top-film metal on the middle-film metal, (2) the activation energy of the diffusion of the top-film metal in the middle film and in the substrate, and (3) the formation of an intermetallic compound between the top-film metal and the substrate in the phase diagram. Examples of intermetallic compound formation by diffusion of the top-film metal are given for a Ti film/Nb film/Cu substrate, a Fe film/Nb film/Ti substrate and other systems.
Predicting pattern-specific distortions induced during optical mask patterning
Authors: Sohn J. , Engelstad R. L. , Lovell E. G.
Published: July 2002

All mask-related distortions must be minimized in order to meet the stringent error budgets for sub-100 nm lithography. Thermomechanical distortions during mask patterning are one source of image placement errors and may potentially consume a relatively large portion of the overlay error budget. This article investigates the thermomechanical distortions of an optical mask during electron-beam patterning. Pattern-specific distortions have been predicted for actual static random access memory layouts using numerical simulations. Finite element simulation results are presented illustrating the temperature rise and final in-plane distortion vector fields for those layouts.
Spun-on carbon antireflective layer with etch resistance for deep and vacuum ultraviolet lithography processes
Authors: Sato Yasuhiko , Onishi Yasunobu , Nakano Yoshihiko , Hayase Shuzi
Published: July 2002

Dry etch resistance and antireflective performance were studied for a film containing a high amount of carbon (83.4 wt %), which was named the spun-on carbon film. The film was formed by using a carbon cluster precursor synthesized by reductive coupling of a mixture of carbon tetrabromide and phenylbromide. The refractive indices of the spun-on carbon film at the exposure wavelengths of excimer lasers are n=1.72, k=0.35 (KrF), n=1.46, k=0.67 (ArF), and n=1.37, k=0.14 (F2). A bilayer bottom antireflective coating system composed of upper spun-on glass (SOG) and lower spun-on carbon was evaluated. By optimizing the SOG thickness, the reflectivity is reduced to 0.2% (KrF), 3.3% (ArF), and 0.5% (F2). Remarkable improvement is observed at the KrF and F2 wavelengths. Resist profiles are obtained without any footing, residue, or standing wave using the KrF and ArF scanning steppers. The etch resistance of the spun-on carbon film is 1.34 times greater than that of the thermally oxidized novolak film (i.e., a conventional underlayer for a trilevel resist process).
Investigation of radical–surface reactions
Authors: Voigt J. , Rangelow I. W.
Published: July 2002

Investigations on some aspects of thermal etching of silicon and polymer substrates are presented. Microscopic mechanisms of thermal degradation of substrate materials commonly applied in microelectronics and microsystem technology by means of radical containing downstream plasma are examined. The role of molecular constituents of the downstream gas flow for the etching process is considered in detail. Transport of free radicals through very high aspect ratio structures is demonstrated experimentally and interpreted in theory. Investigations presented here were performed by means of the Nanojet setup (reported in this volume).
Structural and optical properties of ternary Cs–Pb–Cl nanoaggregates in thin films
Authors: Somma F. , Aloe P. , Lo Mastro S. , Santucci S. , Giampaolo C. , Nikl M. , Nitsch K. , Fabeni P. , Pazzi G. P.
Published: July 2002

Ternary nanophases of CsPbCl3 and Cs4PbCl6 were evidenced in co-evaporated CsCl–PbCl2 thin films using x-ray diffraction spectroscopy. A morphological study by atomic force microscopy revealed the granular nature of the films consisting of the grains of about 150 nm size. The optical properties of CsPbCl3 and Cs4PbCl6 nanostructures were determined. CsPbCl3 is a wide gap semiconductor with direct band transitions and a pronounced Wannier free exciton emission round 418 nm at 5 K with a very small Stokes shift. Cs4PbCl6 is characterized by the auto-localized exciton emission around 365 nm. In both cases, the optical features are closely similar to the bulk ternary crystals which were reported earlier.
At-wavelength characterization of the extreme ultraviolet Engineering Test Stand Set-2 optic
Authors: Naulleau Patrick , Goldberg Kenneth A. , Anderson Erik H. , Batson Phillip , Denham Paul E. , Jackson Keith H. , Gullikson Eric M. , Rekawa Senajith , Bokor Jeffrey
Published: July 2002

At-wavelength interferometric characterization of a new 4×-reduction lithographic-quality extreme ultraviolet (EUV) optical system is described. This state-of-the-art projection optic was fabricated for installation in the EUV lithography Engineering Test Stand (ETS) and is referred to as the ETS Set-2 optic. EUV characterization of the Set-2 optic is performed using the EUV phase-shifting point diffraction interferometer (PS/PDI) installed on an undulator beamline at Lawrence Berkeley National Laboratory’s Advanced Light Source. This is the same interferometer previously used for the at-wavelength characterization and alignment of the ETS Set-1 optic. In addition to the PS/PDI-based full-field wave front characterization, we also present wave front measurements performed with lateral shearing interferometry, the chromatic dependence of the wave front error, and the system-level pupil-dependent spectral-bandpass characteristics of the optic; the latter two properties are only measurable using at-wavelength interferometry.
Fabrication of microfluidic devices in silicon and plastic using plasma etching
Authors: Weston D. F. , Smekal T. , Rhine D. B. , Blackwell J.
Published: July 2002

The move to miniaturization of biomedical systems offers tremendous potential for the improvement of health care, both in terms of reduced analysis time, and in significantly lowering the volume requirements of patient blood, or other bodily fluid. In order to fabricate microchannels for microfluidics, we have investigated two approaches using high-density plasma etching to achieve channel depths of 20–50 microns. The first was plasma etching of tapered silicon masters for hot embossing of plastics to form a capillary electrophoresis device. The second approach was the direct plasma etching of plastic to form a microfluidics device for DNA analysis. In both cases, we report the development of optimized etch conditions using SAS Institute, Inc. design of experiment software.
Characteristics of plasma enhanced chemical vapor deposited W–B–N thin films
Authors: Kim Dong Joon , Sim Hyun Sang , Kim Seong-Il , Kim Yong Tae , Jeon Hyeongtag
Published: July 2002

Amorphous W–B–N thin films were deposited with the plasma enhanced chemical vapor deposition method. The stoichiometry of W–B–N changed from W90B5N5 to W38B42N20 while the flow ratio of B10H14/NH3 varied from 2 to 6 under the condition that the flow ratio of WF6 and NH3 were fixed. During annealing process at 800 °C for 30 min, the W90B5N5 and W80B15N5 films were completely changed into a (100) oriented α-W film. Until the B and N contents in the as-deposited W–B–N film were lower than the W51B30N19 the B and N atoms were out-diffused. Whereas the B and N contents were higher than when the W51B30N19 B–N bond was formed, which prevented the grain growth of W or W–N phases in W–B–N thin film during the annealing process. Formation of the B–N bond in W–B–N thin film is more effective to inhibit the out-diffusion of B and N.
Density changes upon crystallization of Ge2Sb2.04Te4.74 films
Authors: Njoroge Walter K. , Wöltgens Han-Willem , Wuttig Matthias
Published: July 2002

The density of sputtered Ge2Sb2.04Te4.74 thin films upon annealing has been precisely determined by x-ray reflection and compared to the values determined from x-ray diffraction (XRD) data. The film density increases in two steps around 130 and 280 °C upon annealing up to 400 °C. These increases are consequences of phase transitions from amorphous to NaCl type and from NaCl type to hexagonal structure, respectively, as revealed by XRD. Average density values of 5.87±0.02, 6.27±0.02, and 6.39±0.02 g/cm3 were measured for the amorphous, NaCl-type, and hexagonal phases, respectively. This corresponds to density changes upon crystallization of 6.8±0.2% and 8.8±0.2% for NaCl-type and hexagonal phases, respectively. The accompanying film thickness reductions were determined to be 6.5±0.2% and 8.2±0.2%, which compares very well with the density changes. The corresponding XRD values are determined to be 6.43–6.48 and 6.48 g/cm3 for NaCl-type and the hexagonal phases, respectively. This shows that nearly void-free films are formed.
Influence of implantation and annealing on the surface topography of amorphous and polysilicon thin films
Authors: Edrei R. , Shauly E. N. , Hoffman A.
Published: July 2002

In this paper the surface roughness and topography of low-pressure chemical vapor deposition amorphous silicon films grown on (001) silicon substrates after phosphorus/argon/arsenic ion implantation, after annealing at 850 °C in an ambient N2 environment and after further annealing to 1070 °C in O2 environment have been investigated. The influence of the different treatments on the sample surface topography was examined by atomic force microscopy in the noncontact mode. The surface composition of the films was analyzed by x-ray photoelectron spectroscopy for annealed and unannealed phosphorus implanted wafers. It was found that the surface roughness of the films is affected by implantation and annealing and mostly by implantation followed by annealing. Only implantation reduced the surface roughness while only annealing results in an increase of surface roughness. Implantation followed by annealing results in a drastic increase of surface roughness. “Bumps” which appeared following annealing seem to consist of a polysilicon structure. The evolution of surface roughness with annealing temperature is accompanied by a concurrent formation of silicon oxide. Implanted wafers annealed at 850 °C in an ambient N2 grow a thin substochiometric silicon oxide layer which has a higher roughness than the as-deposit amorphous silicon layer. Further annealing to 1070 °C in a O2 environment results in an increase in roughness and formation of a stochiometric SiO2 layer.
Mechanical system construction for the EX-11 electron beam mask writer: A solution for 100 nm wafer lithography
Authors: Akeno Kiminobu , Ogasawara Munehiro , Tojo Toru
Published: July 2002

An advanced mechanical system has been developed for the EX-11 electron beam mask writer. In particular, a new XY stage was designed so as to improve CD uniformity and image placement by reduction of vibration and heat generation, and by stabilization of the stage temperature. A direct-drive friction-drive unit and crossed-roller guides enable the stage to obtain low position fluctuation less than ±1.2 nm over 1 kHz. The active thermal control system of the XY stage using the thermal control plate whose temperature is controlled within 0.001 °C can stabilize that of the top plate of the XY stage. The improved EX-11 is expected to satisfy the requirements for 100 nm generation lithography.
Advancements to the critical ionization dissolution model
Authors: Burns Sean D. , Schmid Gerard M. , Tsiartas Pavlos C. , Willson C. Grant , Flanagin Lewis
Published: July 2002

The microlithographic process is dependent upon the dissolution of acidic polymers in aqueous base. The fundamental mechanism that governs the dissolution of these polymers has been the subject of considerable discussion, and a number of theories have been proposed to explain this behavior. Our research group has presented the critical ionization (CI) dissolution model to explain the dissolution of phenolic polymers in aqueous base. Specifically, the model proposes that a minimum or critical fraction of ionized sites, fcrit, on a given polymer chain must be ionized in order for that chain to dissolve. The main input parameters to this model are the critical fraction of ionized sites, fcrit, and the fraction of ionized surface sites, α. In this work methods are established for measuring these parameters. A quantitative link between the CI model and experiment has been demonstrated for the dissolution rate and surface roughness dependence on polymer molecular weight. Methods for calculating α are discussed, including a new method that considers the formation of an electrostatic double layer at the resist–developer interface.
Deep etch of GaP using high-density plasma for light-emitting diode applications
Authors: Wuu D. S. , Chung C. R. , Liu Y. H. , Horng R. H. , Huang S. H.
Published: July 2002

Deep etching of GaP was performed by high-density plasma using an inductively coupled plasma (ICP) etcher. The effects of process parameters such as the gas combination (Cl2/N2), chamber pressure, inductive power and rf chuck power were investigated. The dependences of the etch rates and selectivity on the rf chunk power and chamber pressure were studied using the response surface method. The results obtained can be further interpreted by the plasma properties (ion flux and dc bias) measured in situ by a Langmuir probe. With an increase in the chamber pressure to 4 Pa, a maximum etch rate of ∼7.5 μm/min for GaP can be obtained under a Cl2/(Cl2+N2) gas mixture of 0.8, ICP power of 800 W, and rf power of 100 W. The increase in the etch rate with an increase in chamber pressure indicates that reactive radicals are the main etching species. To clarify the etching mechanism, the surface reaction of GaP under various Cl2/(Cl2+N2) gas mixtures was investigated by x-ray photoelectron spectroscopy and atomic force microscopy. In addition, quantitative analysis of the plasma-induced damage was attempted in order to discuss the mechanism of leakage current density and brightness with various rf powers on AlGaInP light-emitting diodes with a thick GaP window layer. Under a fixed ICP power applied, it is found that the duration of the plasma (not dc bias voltage) has a major effect on leakage current performance. Finally, an effective recovery method is developed, in which plasma-induced damage can be recovered in a boiling NaOH solution with the range of our experiments.
Extended Mass Range Operation of the Monopole Mass Spectrometer
Authors: Grande R. E. , Watters R. L. , Hudson J. B.
Published: July 2002

Data are presented demonstrating the degree to which the mass range of monopole and quadrupole mass spectrometers may be extended by various techniques and concomittant effects that this mass range extension has on the other operating parameters such as resolving power, sensitivity, and mass discrimination. These data indicate that high sensitivity and unit resolution may be maintained over a mass range of greater than 600 amu in a monopole instrument of modest size. Further extension is also possible if resolution or sensitivity may be sacrificed.