bluuebunny/crossref_metadata_2025 huggingface dataset:
High-density plasma patterning of low dielectric constant polymers: A comparison between polytetrafluoroethylene, parylene-N, and poly(arylene ether)
Authors: Standaert T. E. F. M. , Matsuo P. J. , Li X. , Oehrlein G. S. , Lu T.-M. , Gutmann R. , Rosenmayer C. T. , Bartz J. W. , Langan J. G. , Entley W. R.
Published: July 2002

The pattern transfer of SiO2 hard masks into polytetrafluoroethylene, parylene-N, and poly(arylene ether) (PAE-2) has been characterized in an inductively coupled plasma source. Selected results obtained with blanket parylene-AF4 films are included in this work. These dielectrics offer a relatively low dielectric constant (k∼2–3) and are candidate materials for use as intra- and interlayer dielectrics for the next generations of high-speed electronic devices. Successful patterning conditions were identified for Ar/O2 and N2/O2 gas mixtures. It was found that the formation of straight sidewalls in Ar/O2 discharges relies on the redeposition of oxygen-deficient etch products on the feature sidewall. Furthermore, the etch rates of parylene-N, parylene-F, and PAE-2 for blanket and patterned films could be captured by a semiempirical surface coverage model, which balances the adsorption rate of oxygen and the ion-induced desorption rate of oxygenated etch products.
Fabrication process of field emitter arrays using focused ion and electron beam induced reaction
Authors: Ochiai C. , Yavas O. , Takai M. , Hosono A. , Okuda S.
Published: July 2002

Metal-gated Pt field emitter arrays (FEAs) have been manufactured using a dual beam system consisting of focused ion and electron beams. The gate opening in Nb or Au gate layers was produced by physical sputtering using a focused ion beam and subsequent wet etching of the underlying silicon dioxide layer. Deposition of a platinum tip into the gate opening using electron-beam-induced chemical reaction resulted in field emission without any thermal annealing process. After wet etching an enlargement of the gate opening in Nb-gated FEAs was observed due to the beam-induced enhanced etching. In contrast, the smaller gate opening in Au-gated FEAs was easily fabricated because of the suppression of the enhanced etching. Consequently, the gate opening was controlled by selection of the gate metal material. The turn-on voltage for field emission decreased by decreasing the diameter of the gate opening.
Analysis of tunneling magnetoresistance test structures by low energy electron nanoscale-luminescence spectroscopy
Authors: Goss S. H. , Parkin S. S. P. , Brillson L. J.
Published: July 2002

The performance of state-of-the-art tunneling magnetoresistive (TMR) heads depends on the thickness of insulating layers less than a few nanometers thick that separate two magnetic films. We have used low energy electron nanoscale-luminescence (LEEN) spectroscopy to observe optical emission from TMR test structures with buried insulating oxides less than a few nanometers thick. TMR structures grown by metal evaporation consisted of a 0.8–3 nm Al oxide layer on a 2.4 nm CoFe alloy (84:16) on a multilayer metal-on-Si substrate, all capped with a 0.4 nm CoFe with Pt overlayer. LEEN studies with excitation energies ranging from 0.5 to 3 keV enabled emissions from the buried oxide layers versus the free surface to be distinguished. We used different compositions, thicknesses, and oxidation exposures to separate Al oxide from transition metal oxide emissions, as well as from the ambient-exposed Pt surface. A broad peak centered at 2.2–2.5 eV increased with O plasma exposure to Al films on the CoFe alloy. Emission from oxidized CoFe without Al consists of a broad emission centered at 2.5 eV. Common to all these spectra is emission at 1.8 eV, which energy-dependent LEEN demonstrates is due to the ambient-exposed Pt. Spectral changes versus oxygen exposure reveal the regime separating oxidation of the magnetic and nonmagnetic layers.
Rapid cooling dual slot load locks for liquid crystal display
Authors: Hosokawa Akihiro , Blonigan W. , Kurita S.
Published: July 2002

Rapid cooling of 680×880 mm glass substrates was demonstrated in the dual-slot load locks [S. Kurita, W. Blonigan, and A. Hosokawa, U.S. Patent pending No. 7828.7017 (December 1999)] of an AKT 5500 chemical vapor deposition system. Two complimentary techniques are used to cool a substrate from 400 to 60 °C within 33 s while maintaining a temperature uniformity of ±5 °C. Helium equivalent to a partial pressure of 9 Torr is injected at the initial stage of venting. Cooling plates are located as close as 8 mm above and below the substrate while cooling. Rapid-cool dual-slot load locks reduce cost by eliminating large vacuum pumps and machine components. Uniform cooling eliminated undesirable thermal stress during cooling and thus enabled reliable substrate handling.
Focusing properties of dual-gate field emitters
Authors: Nicolaescu Dan , Filip Valeriu , Itoh Junji
Published: July 2002

Field emitters are used as distributed electron sources in applications such as field emission displays (FEDs). Reducing the angular aperture of the electron beam increases the resolution and luminance of the FED. This study comparatively analyzes the focusing properties of several kinds of dual-gate emitter structures. The configurations considered are the coplanar and coaxial gate types, and also the coaxial gates structure with protruding emitter, considered for the first time in this context. The simulation work was performed using the SIMION 3D 7.0 software package. Several conclusions are drawn concerning the suitability of double-gated emitter structures for electron beam focusing.
Deposition of trimethylsilane in glow discharges
Authors: Yasuda H. K. , Yu Q. S.
Published: July 2002

The deposition characteristics of trimethylsilane (TMS) on the electrode surface, and on floating substrates, are investigated in direct current (dc), 40 kHz, and 13.5 MHz discharges by examining the difference of dependence on operational parameters; flow rate, discharge wattage, and the system pressure. In dc glow discharge, the deposition of materials are caused by the mixture of “dark” cathodic polymerization, which is pressure dependent, and “glow” plasma polymerization in the negative glow, which is pressure independent. The deposition onto the cathode surface is primarily by the dark polymerization, but the deposition onto any noncathode surface, including the anode surface, is by glow plasma polymerization. The creation of reactive species occurs by electron-, ion-, and (excited neutrals)-impact dissociations of TMS in the cathode dark region and in the negative glow. With an alternating current discharge, the feature of the dark cathodic polymerization decreases to the half of the dc because an electrode is the cathode only for half of the deposition time, but in 13.5 MHz discharge, the influence of the dark cathodic polymerization totally diminishes as the creation of reactive species changes to that by the oscillating electrons and associating species in the glow. The cathodic polymerization provides the best protective coating on metallic substrates.
Chemical and structural characterization of La0.5Sr0.5MnO3 thin films prepared by pulsed-laser deposition
Authors: Decorse P. , Quenneville E. , Poulin S. , Meunier M. , Yelon A. , Morin F.
Published: July 2002

La 0.5 Sr 0.5 MnO 3 thin films were deposited onto sapphire substrates by means of the pulsed-laser deposition technique. These films were characterized by several techniques including x-ray diffraction, Rutherford backscattering spectrometry, energy-dispersive x-ray, atomic-force microscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy (XPS). The cation ratios are the same in the deposited films as in the target. However, strontium segregation occurs at the film surface with an enrichment in this element compared to Mn and La, as shown by XPS. In addition, a clear correlation between the three different contributions which compose the O(1s) XPS signal and the Sr, La, and Mn surface concentrations has been established. Annealing the films at a sufficiently high-temperature produces the same crystal structure as in the target.
Etching mechanism of YMnO3 thin films in Cl2/Ar gas chemistries
Authors: Min Byung-Jun , Kim Chang-Il , Kim Yong-Tae
Published: July 2002

Ferroelectric YMnO3 thin films are excellent dielectric materials for high integrated ferroelectric random access memory with a metal–ferroelectric–silicon field effect transistor structure. In this study, YMnO3 thin films were etched with Cl2/Ar gas chemistries in inductively coupled plasma. The maximum etch rate of YMnO3 thin films is 285 Å/min under Cl2/(Cl2+Ar) of 1.0, 600 W/−200 V and 15 mTorr. The selectivities of YMnO3 over CeO2 and Y2O3 are 2.85 and 1.72, respectively. The results of x-ray photoelectron spectroscopy (XPS) reflect that Y is removed dominantly by chemical reaction between Y and Cl, while Mn is removed more effectively by Ar ion bombardment than chemical reaction. The results of the secondary ion mass spectrometer were equal to these of XPS. The etch profile of the etched YMnO3 film is approximately 65° and free of residues at the sidewall.
Ion-assisted deposition of silicon nitride films using electron cyclotron resonance plasma
Authors: Vargheese K. Deenamma , Rao G. Mohan
Published: July 2002

Ion-assisted deposition (IAD) is one of the most widely used techniques for the deposition of thin films. Electron cyclotron resonance (ECR) ion sources are ideal for ion-assisted deposition due to high ionization efficiency even at low pressures. Silicon nitride films have been deposited by rf reactive sputtering with ion assistance from an ECR plasma. The ECR power was varied from 0 to 250 W. The effect of ECR plasma on the growth of silicon nitride films has been shown to be systematic and is characterized by using Fourier-transform infrared spectroscopy and atomic force microscopy. The surface roughness for the films deposited without ECR plasma was about 2 nm and decreased to about 0.7 nm for those deposited with 250 W of ECR power. The optical band gap changed from 2.2 to 4.9 eV as the ECR power was increased, indicating higher reactivity in the presence of ECR plasma. Good quality silicon nitride films with a band gap of 4.9 eV, a refractive index of 1.92, and an extinction coefficient of 4×10−4 have been obtained with an ECR power of 100 W (corresponding ion density of 1.5×1010 cm−3) and the surface roughness was less than 0.7 nm. The compositional analysis carried out using Auger electron spectroscopy showed a Si/N ratio of 0.73 for the films deposited under optimum deposition conditions.
Reflection high-energy electron diffraction study of ion-beam induced carbonization for 3C–SiC heteroepitaxial growth on Si (100)
Authors: Tsubouchi Nobuteru , Chayahara Akiyoshi , Mokuno Yoshiaki , Kinomura Atsushi , Horino Yuji
Published: July 2002

A novel carbonization process for 3C–SiC heteroepitaxial growth on Si (100) with mass-separated ion beams (e.g., C−, C2−, C+, and CH3+ ions) was carried out by in situ monitoring with reflection high-energy electron diffraction measurements. The kinetic energies of ions and substrate temperatures were in the range of E=10–700 eV and T= 400–700 °C, respectively. This ion-beam induced carbonization process was investigated as a function of various irradiation parameters; i.e., ion kinetic energy, substrate temperatures, charge and mass of ions, ion species, ion irradiation modes, etc. and was compared to conventional carbonization processes with thermal species; e.g., hydrocarbon gases. As a result, the use of energetic ion species allows successful carbonization and provides lower process temperatures by 150–600 °C, compared to the conventional processes reported previously. The mechanisms of carbonization reaction with energetic ions are compared to using thermal species.
Gas sensing properties of copper gate metal–oxide–semiconductor capacitors
Authors: Filippini D. , Aragón R. , Weimar U.
Published: July 2002

Metal–oxide–semiconductor capacitors with sputtered 100 nm thick copper gates, operated at 180 °C, are sensitive to NO2, with no cross sensitivity either to H2 or CO, in inert atmospheres and air. Sensitivity to NO is present in air only. Flatband voltages shift positive with NO2 stimulus, similarly to gold gates of comparable morphology, but responses are an order of magnitude smaller. Unlike Au, response and relaxation times are independent of NO2 concentration and the signal is affected by negative drift, due to gate oxidation. Ultraviolet photoelectron spectroscopy measured changes of the work function upon NO2 adsorption, which are larger for copper than gold, are not representative of the corresponding gate-dielectric change.
Study of the exposure-dose-dependent photon-stimulated-desorption phenomena
Authors: Hsiung G. Y. , Young K. Y. , Hsu Y. J. , Chen J. R.
Published: July 2002

Photon-stimulated desorption (PSD) was studied by using synchrotron light at a critical energy of 2.14 keV from the 1.5 GeV Taiwan Light Source. Samples of aluminum alloy (Al) and oxygen-free-high-conductivity copper (Cu) was studied at the 19B(PSD) beam line of the Synchrotron Radiation Research Center for exposure measurement. The yields of photoemission and the PSD are measured at different exposure beam doses. The result shows a decrease of the PSD yield for each gas and a decreased yield of photoemission at higher beam doses on the samples. The transient curves of pressure rise for each PSD molecule illustrate a longer delay time τ of the peak after exposing the surface with higher beam dose D. The delay time of H2O and O2 are longer than that of CO, CO2, CH4, etc., in the case of both Al and Cu samples. In this work, it is found that τ∼Dα, with 0.5<α<1, in cases where D<2000 mA h. The discrepancy between the Al and Cu samples is not much different at higher beam doses. The processes of the chemical reactions by the photoelectrons and diffusion in the surface oxide layer are suspected to conduct the dose-dependent PSD phenomena.
Recent progress in 1×x-ray mask technology: Feasibility study using ASET-NIST format TaXN x-ray masks with 100 nm rule 4 Gbit dynamic random access memory test patterns
Authors: Tsuboi Shinji , Tanaka Yuusuke , Iwamoto Toshiyuki , Sumitani Hiroaki , Nakayama Yoshinori
Published: July 2002

This article discusses recent progress in 1×x-ray mask technology in Japan. Proximity x-ray lithography (PXL) using synchrotron radiation light with a wavelength of 0.7–1.0 nm can in principle provide as high a throughput as optical lithography, because PXL and optical lithography both employ photon beams and masks. A high-performance electron-beam mask writer called the EB-X3, suitable for PXL, has been developed by NTT under the Association of Super-Advanced Electronics Technologies (ASET) program. It has a reproducible image placement (IP) accuracy of less than 15 nm. We used the shaped-beam EB-X3 to fabricate 100 nm rule x-ray masks for the gate and contact/hole (C/H) layers of 4 Gbit dynamic random access memory (DRAM) test patterns. The ASET-NIST (National Institute of Standards and Technology) type masks consist of a 350-nm-thick TaBN absorber, a 3-μm-thick SiC membrane (27-mm square membrane area), a 1-mm-thick Si substrate, and a 6.63-mm-thick Pyrex glass frame. We have achieved an IP accuracy for 1×x-ray masks of less than 15 nm at both the gate and C/H levels. The mask-to-mask overlay accuracy between the gate and C/H masks is less than 20 nm; and after magnification correction, it is less than 10 nm. The critical dimension (CD) variations for 100 nm features measured in a 24-mm-square area are less than 100±6.0 nm at both levels. An overlay accuracy for PXL of better than 30 nm (|mean|+3σ) was obtained by the double-exposure method using the XRA volume-production x-ray stepper (Canon, Inc.) and 18 nm overlay ASET-NIST type x-ray masks (gate to contact). An IP reproducibility of less than 7 nm has been achieved for the EB-X3 itself (best data). The resist CD accuracy on the membrane for 4 Gbit DRAM patterns is better than 7 nm (Δ|mean|+3σ=6.6 nm). These data indicate that PXL has the potential for patterning 50 nm node devices with current tools.
Initial growth step and annealing effect of Ta2O5 formed by anodization of Ta foil in an ammonium tartrate electrolyte
Authors: Ahn Kwang-Soon , Sung Yung-Eun
Published: July 2002

The initial growth step during the anodization of a Ta foil and structural changes in the Ta2O5 film with anodizing time and annealing temperature were investigated using cyclic voltammetry, chronoamperometry, ac impedance spectroscopy, atomic force microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Under the conditions used here, the Ta2O5 film was anodized by the island growth mechanism and the initial growth step of Ta2O5 formation is via the tunneling mode, which is thickness dependent, that is, changing from direct tunneling to defect-enhanced tunneling as the thickness is increased up to a considerable thickness (about 200 Å). The anodized Ta2O5/Ta samples were annealed by rapid thermal annealing (RTA) and Pt metals were then sputtered to produce the Pt/Ta2O5/Ta structure. Based on the leakage current versus voltage data for Pt/Ta2O5/Ta, we conclude that an anodized Ta2O5 film can be used as an insulating material for storage capacitors in combination with an optimum RTA treatment.
Direct measurement of Coulomb effects in electron beam projection lithography
Authors: Yahiro Takehisa , Suzuki Shohei , Irita Takeshi , Hirayanagi Noriyuki , Shimizu Hiroyasu , Kojima Shinichi , Morita Kenji , Kawata Shintaro , Okino Teruaki , Suzuki Kazuaki
Published: July 2002

We describe a direct measurement of the image blur and defocus induced by Coulomb effects (stochastic and global space charge) in electron beam projection lithography. The Nikon 100 kV electron beam projection experimental column was used for the experiments. This column has similar values of electron optical parameters to those of electron beam projection lithography (EPL) systems. The Coulomb effect image blur and defocus were directly measured by a knife-edge method. The experimental data of Coulomb effect image blur and defocus as functions of beam current are shown. The experimental results show excellent agreement with our Monte Carlo simulation results.
Evaluation of new x-ray stepper, the XRA
Authors: Sumitani Hiroaki , Suita Muneyoshi , Mitsui Soichiro , Aoyama Hajime , Fujii Kiyoshi , Watanabe Hiroshi , Taguchi Takao , Matsui Yasuji
Published: July 2002

The exposure performance has been evaluated for the new x-ray stepper, the XRA, which is equipped with global alignment and magnification correction systems. Dose uniformity in the exposure field of 3.9%, stage accuracy of less than 20 nm, and good linearity and stability between the magnification change and applied force were obtained. For the 100 nm node, both critical dimension (CD) control of 10 nm and overlay accuracy of less than 30 nm were obtained using two 4 Gbit masks of the gate and contact hole by the double exposure method. Possible improvements of the dose uniformity and mask pattern CD will result in more accurate CD control. By compensating for the alignment offset, overlay accuracy of 23 nm for the 70 nm node is also expected.
Stochastic Coulomb interaction effect in ion-neutralized electron-beam projection optics
Authors: Takahashi Kimitoshi , Han Liqun , Pease R. Fabian , Meisburger W. Dan
Published: July 2002

The stochastic Coulomb interaction effect in positive ion-neutralized electron-beam (e-beam) projection optics was investigated using Monte Carlo simulations. Stationary ions in the projection optics neutralize e-beam space charge without causing an unwanted increase in stochastic blur. The Coulomb interaction due to the stationary positive ions only has an effect as that of a continuum space charge. We also found that asymmetric point spreads at the field corners are due to the stochastic Coulomb interaction effect and are not a result of residual space charge effect. Methods of ion cloud generation were preliminary discussed. The ion neutralization potentially increases the throughput of an exemplary electron projection tool for 30 nm devices by a factor of 2.
Pattern placement correction methodology for 200 mm SCALPEL masks
Authors: Ocola L. E. , Farrow R. C. , Kasica R. J. , Caminos C. G. , Rutberg L. , Fullowan R. F. , Teffeau K. , Blakey M. I. , Peabody M. L. , Knurek C. S. , Bogart G. R. , Novembre A. E. , Liddle J. A. , Lercel M. , Magg C. , Collins K. , Trybendis M. , Cadwell N. , Jeffer R. , Dauksher W. J. , Resnick D. J. , Mancini D. , Han S. I. , Masnyj Z. , Smith K. , Mangat P. J. S.
Published: July 2002

Methods for correcting pattern placement errors found on SCALPEL™ masks are addressed. The methodology and implementation of individual membrane image placement correction is presented, showing its advantages over the global image placement correction method. Local image placement corrections are possible by the unique capability of electron projection lithography (EPL) tools to correct placement errors with electron optical components during exposure while addressing each individual mask membrane. Data of pattern placement on a series of 200 mm SCALPEL masks from different sources was collected. Within the mask set and patterning tools used, the placement errors are similar for all masks regardless of source. Local image placement corrections can reduce placement errors to less than 14 nm, which is less than the 20 nm budget allocated for 100 nm node lithography. Implementation of local image placement correction will permit EPL lithography to be ready for sub-100 nm node lithography without the need to burden existing mask writers on severely stringent pattern placement tolerances or chucking procedures.
Linewidth reduction using liquid ashing for sub-100 nm critical dimensions with 248 nm lithography
Authors: Timko A. G. , Frackoviak J. , Hopkins L. C. , Klemens F. P. , Trimble L. E. , Nalamasu O. , Watson G. P. , Mansfield W. M. , Barr D. , Li J.
Published: July 2002

The need for sub-100 nm semiconductor devices has driven our industry to develop new resists, exposure tools (248 nm, 193 nm, extreme ultraviolet, SCALPEL, etc.), mask technologies, and processing procedures. An enormous amount of research has gone into every aspect of the semiconductor device fabrication process and new techniques to further reduce the critical dimensions need to be investigated. The work that is reported on in this article identifies a process that is referred to as liquid ashing. Liquid ashing is a novel approach to linewidth reduction of resist features patterned with positive 248 nm deep-ultraviolet (DUV) resists. The lashing process reduces linewidth through the use of a second wet development step. This process is isotropic and can be continued once started. A bake prior to the second development improves process control. Various types of phase-shifted patterns have been measured and evaluated to determine the effectiveness of this process. This process has been exercised using different resists, different developers, and several different integrated circuit (IC) test patterns. Linewidth reduction using liquid ashing is controllable, does not increase linewidth variations, and can be accomplished using existing equipment. The process was evaluated with IC test patterns that were printed using attenuated phase shifted mask technology generated photo masks and conventional DUV processes. Scanning electron microscopy was used to obtain critical dimension data and cross-sectional information. Features, ranging from 120 to 280 nm in size were reduced by 60 nm at a controllable rate of approximately 1.25 nm/s. Transistor gates as small as 60 nm have been formed in 248 nm DUV resist and successfully transferred while maintaining >85° wall profile.
Low
-k
1
optical lithography for 100 nm logic technology and beyond
Authors: Yen Anthony , Yu Shinn-Sheng , Chen Jeng-Horng , Chen Chun-Kuang , Gau Tsai-Sheng , Lin Burn Jeng
Published: July 2002

In this article, we present 193 nm lithography at a k1 factor of 0.37–0.40 and discuss several topics important to 100 nm logic such as optical proximity correction (OPC), control of critical dimension (CD) variation, and lowering of the mask error factor (MEF). In OPC, the best correction results can be achieved by developing accurate models and using reasonable segmentation rules. The technique of variable-dose exposures is demonstrated as a means to reduce interfield CD variation once the cause is known and can be characterized. A more than 30% reduction in CD variation is realized for variation caused by temperature nonuniformity in hot plates. The concept of two dimensional (2D) MEF is introduced to describe situations at feature ends. Higher numerical aperture or more effectively, quadrupole illumination, can be used to lower 1D and 2D MEFs. We also explore the technique of dipole illumination, which may be a candidate for taking optical lithography to k1<0.35.
Cr absorber etch process for extreme ultraviolet lithography mask fabrication
Authors: Smith K. H. , Wasson J. R. , Mangat P. J. S. , Dauksher W. J. , Resnick D. J.
Published: July 2002

Reactive ion etching (RIE) and inductively coupled plasma (ICP) Cr etch processes have been evaluated for fabrication of extreme ultraviolet lithography masks on 200 mm substrates. Experiments were completed to optimize the Cr etch rate, etch rate uniformity, and Cr to resist selectivity for both etch processes. The best ICP process was found to have superior etch rate, etch rate uniformity, and comparable Cr to resist selectivity to the RIE process. The effect of exposed Cr area on the Cr to resist selectivity, critical dimension (CD) bias, and CD bias 3σ was also investigated. A decrease in exposed Cr area from 95% to 7% was found to dramatically increase the Cr etch rate, leading to an increase in the Cr to resist selectivity. Lower Cr loading was also found to decrease the CD bias and CD bias 3σ. The average CD bias was very high for both processes, with the ICP etch process having a higher CD bias (143 nm) than the RIE process (89 nm). The CD bias uniformity was significantly lower for the ICP process (32 nm, 3σ) when compared to the RIE process (71 nm, 3σ).
High-throughput electron-beam lithography with a raster-scanned, variably shaped beam
Authors: Veneklasen L. H. , Kao H. M. , Rishton S. A. , Winter S. , Boegli V. , Newman T. , Bertuccelli G. , Howard G. , Le P. , Tan Z. , Lozes R.
Published: July 2002

A raster-shaped beam writing strategy has been tested on a prototype 50 keV electron-beam lithography workstation. The test stand was constructed to prove the raster-shaped beam concept by exposing patterns at full throughput over small areas. Patterns are composed in a raster-scanned array of variably shaped flashes at 100 MHz flash rate, with 0.9 μA full beam current, and 2200 A/cm2 current density using a thermal field emission source. Writing speed is independent of resist sensitivity and pattern complexity. By comparison, a typical variably shaped beam system with a LaB6 source would have a current density of 10–30 A/cm2 and a flash rate of 2–10 MHz, depending on resist sensitivity and deflection settling time.
Photocatalytic, antifogging mirror
Authors: Takagi K. , Makimoto T. , Hiraiwa H. , Negishi T.
Published: July 2002

This article is about the coating of thin titanium dioxide film by sputter deposition. When irradiated with solar light, thin titanium dioxide film exhibits high oxidizing power and provides sterilizing, cleaning, decomposing, and hydrophylic effects. This technique has already been used for coating building walls by the sol–gel method and by others and has been partly commercialized to make automotive sideview mirrors. There have been no practical applications of the sputter deposition method so far, but establishment of the coating method is expected because of its excellent properties of film production techniques such as film thickness uniformity, film quality durability, and freedom from environmental pollution. In this article we discuss the establishment of the method of evaluating the quality of thin titanium dioxide film, establishment of sputter-deposition conditions, and the results of observation by x-ray diffraction and atomic force microscopy of the thin film. It was found that titanium dioxide films, 200 nm or more in thickness, have the above mentioned performance and that sputter deposition allows the film to form without heating.
Characteristics of a taper-seal type gasket for the Conflat® sealing system
Authors: Kurokouchi Satoshi , Morita Shinsaku , Okabe Masayuki
Published: July 2002

Disk (flat ring) gaskets are commonly employed in conjunction with the ConFlat® metal sealing system. The use of the disk gasket, however, limits the seal performance on the ConFlat system because considerable tightening force is wasted in the sealing process when the flange knife edge cleaves the surfaces of the disk gasket. The taper-seal type gasket, which seals entirely by the compression of its corners without surface shearing, can be expected to improve the inefficiency of the ConFlat system relative to performance using conventional disk gaskets. Tightening tests on both gasket versions demonstrated that the seal area on the taper-seal type gasket was some 1.6–3.7 times larger than that on conventional disk gaskets, even when the taper-seal type gasket material is relatively hard. This result suggests that the tightening force acts more effectively to form a sealed area on a taper-seal gasket than a disk gasket. The two types of gaskets also differed in their stress distributions under the tightening load. Results of stress analyses using computer simulation showed that the stress concentration occurred in the conventional disk gasket around the tip of flange knife edge, and that maximum stress could be over four times larger than that seen in the taper-seal gasket. This excessively high stress in the disk gasket prevented achievement of a wide seal area, and intensified the creep of gasket materials during the baking process, this increasing the probability of leaks developing. The characteristic mode of deformation of the taper-seal gasket generates a highly stable stress distribution, virtually independent of the tightening torque; thus, good seal performance is realized, even under sever thermal cycling conditions.
PREVAIL-EPL alpha tool: Early results
Authors: Golladay S. D. , Pfeiffer H. C. , Bohnenkamp C. A. , Dhaliwal R. S. , Enichen W. A. , Gordon M. S. , Kendall R. A. , Lieberman J. E. , Stickel W. , Rockrohr J. D. , Tressler E. V. , Tanimoto A. , Yamaguchi T. , Okamoto K. , Suzuki K. , Miura T. , Okino T. , Kawata S. , Morita K. , Suzuki S. C. , Shimizu H. , Kojima S. , Varnell G. , Novak W. T. , Sogard M.
Published: July 2002

The IBM/Nikon alliance is developing an EPL stepper alpha tool based on the PREVAIL technology. This article provides a status report on the alliance activity with particular focus on the electron optical subsystem developed at IBM. We have previously described design features of the PREVAIL Alpha system. The state-of-the-art e-beam lithography concepts have since been reduced to practice and turned into functional building blocks of a production level lithography tool. The electron optical subsystem has been designed, built, assembled, and tested at IBM’s Semiconductor Research and Development Center (SRDC) in East Fishkill, NY. After demonstrating subsystem functionality, the column, an interim mechanical system and all associated control electronics hardware and software have been shipped during January 2001 to Nikon’s facility in Kumagaya, Japan, for integration into the Nikon commercial e-beam stepper Alpha tool. Postshipment activity has been directed primarily toward demonstrating subfield stitching, a task which exercises system architecture, calibration, stability, and noise performance.
Contactless testing of wiring networks by an electron beam system utilizing induced current detection
Authors: Golladay S. D.
Published: July 2002

Flying-probe mechanical test systems which detect opens and shorts in electrical networks within a multichip module substrate by measuring the capacitance of network elements have found application within the manufacturing industry. The feasibility of a contactless capacitance measurement method using an electron beam is reported here. Compared to mechanical probers, an electron beam capacitance tester could have higher throughput, test smaller features, and eliminate the possibility of probe damage to substrates. The test method is easily implemented as it employs a low voltage probe beam with a small deflection range, electron flood guns, a grid or electrode above the substrate, and an induced current detector. The capacitance between the node under test and the conductive plane is measured (indirectly) as the node is charged by the probe beam. Capacitance measurement to the accuracy required to detect opens and shorts has been demonstrated.
Mechanical, geometrical, and electrical characterization of silicon membranes for open stencil masks
Authors: Sossna E. , Degen A. , Rangelow I. W. , Drzik M. , Hudek P. , Tiwald T. E. , Woollam J. A.
Published: July 2002

Silicon membranes are used for stencil masks which are key to charged particle projection lithography, particularly for ion projection lithography, electron beam projection. Quantitative and qualitative determination of the mechanical properties of the true thickness, thickness variations (morphology), electrical conductivity and stress is critical to the development of next generation lithography. The metrology setup includes high accuracy thickness, refractive index and electrical conductivity measurement based on infrared variable angle spectroscopic ellipsometry, thickness variation characterization based on the Fizeau interferometric scheme and mechanical stress evaluation based on a novel double bulging technique.
High-resolution nitride etching using hydrogen implantation effect
Authors: Ezaki Mizunori , Kato Yoshihide , Tojo Tooru
Published: July 2002

A nitride etching method by oxygen plasma using hydrogen implantation effect is reported. High-resolution patterning of nitride film with sub 50 nm width is demonstrated using this etching method. The mechanism of the nitride etching process has been investigated with various measurements in this study. The measurement results show that the binding of nitrogen and hydrogen in the nitride films is caused by the irradiation of hydrogen-containing gas plasma and the hydrogen implantation into the nitride film plays an important role in the nitride etching by oxygen plasma. No plasma-induced damage in nitride film, such as formation of defects and dislocations, is observed in the case that this etching method is used. This etching method with low damage is applicable to the fabrication of various nitride-based devices.
Focused ion beam patterned Hall bars and Ohmic columns embedded in molecular-beam-epitaxial-grown GaAs/AlGaAs
Authors: Vijendran S. , See P. , Ahmed A. , Beere H. E. , Jones G. A. C. , Norman C. E.
Published: July 2002

Focused ion beam lithography combined with molecular-beam-epitaxial growth can be a useful tool for the formation of real-time patterned, embedded structures. For this purpose, sub-50 eV ion beams are essential to minimize ion induced damage and to ensure vertical localization of the deposited ions. The simultaneous patterning of a beam of dopant ions during wafer growth allows the realization of three-dimensional structures with doping profiles otherwise unattainable through conventional methods. This article reports on the successful fabrication of focused ion beam patterned Hall bars in epitaxially grown bulk GaAs and GaAs/AlGaAs heterostructures. The bulk Si2+ doped sample achieved a 77 K mobility of 4000 cm2 V−1 s−1 for a carrier concentration of 3.4×1017 cm−3 while the heterostructure showed a 1.5 K mobility of 1.8×105 cm2 V−1 s−1 at a carrier density of 5.5×1011 cm−2. It is also demonstrated that in situ device patterning reduces the number of required ex situ processing steps while maintaining the high quality of molecular-beam epitaxially grown material. Furthermore, the development of in-grown ohmic contact columns to buried structures is presented. A proposed three dimensionally integrated circuit and future applications of this new technology are also discussed.
Product wafer monitoring of ultrashallow channel implants with an elastic metal gate
Authors: Hillard Robert J. , Howland William H. , Mazur Robert G. , Ye Win , Variam Naushad K.
Published: July 2002

The most critical parameter for deep submicron metal–oxide–semiconductor (MOS) field effect transistors (MOSFETs) is the threshold voltage (VT). The device VT is highly dependent on processing; specifically, the ion implanted channel-doping profile. Monitoring the channel doping on product wafers is highly desirable and is a major issue for process engineers. A technique based on a noncontaminating, nondamaging, small diameter metal contact is described for highly sensitive and precise measurements of the channel carrier density profile, dose and VT on product wafers.
Measuring optical image aberrations with pattern and probe based targets
Authors: Robins Garth , Adam Konstantinos , Neureuther Andrew
Published: July 2002

A theoretical foundation is given for the ability of programmed-probe based aberration targets to measure individual Zernike terms. The optimum targets are inverse Fourier transforms of the Zernikes and this allows the main features of the family of targets to be predicted in advance. Simulation of discretized versions shows an impressive 27%–36% increase, per 0.01 λ of rms aberration, in the intensity at the center of the target relative to the clear field intensity. The cross contamination by other targets is about 1/6 as large and it is thus possible to measure spherical aberration independent of focus.
Capacitance accelerometer with metal microbeam
Authors: Chaikovsky I. , Reznik M. , Karnovsky I.
Published: July 2002

At present, there exist numerous designs of accelerometers based on microelectromechanical systems technology. We propose an accelerometer that also belongs to this design, whose operation principle is based on transformation of different capacitance signals generated by displacement of a mass element. A distinctive feature of the proposed accelerometer is the use of hybrid metal-silicon technology allowing us to replace silicon, a brittle material, with a metal alloy featuring high mechanical properties. The combined accelerometer design proposed is intended for operation in the range of small acceleration, up to ±2 g, where high accuracy of measurements and sensitivity of 0.01 g are insured. The combined design can be used equally well for higher acceleration ranges. A mathematical calculation and optimization of the proposed device were carried out. A solution for the problem of matching materials with different thermal extension coefficients is also proposed. This makes it possible to develop and produce metal-silicon structures for accelerometers in a wide region of acceleration values.
Extended radio frequency nonlinear model for power prediction of AlGaAs/InGaAs pseudomorphic high electron mobility transistors
Authors: Lin Cheng-Kuo , Chan Yi-Jen
Published: July 2002

A modified nonlinear Curtice model for pseudomorphic high electron mobility transistors, capable of modeling the current–voltage characteristics, drain-to-source resistances, and gate-to-source and gate-to-drain capacitances, has been developed. Parameters extraction is based on dual delta-doped pseudomorphic high electron mobility transistors on GaAs substrates. Measured and modeled dc I–V, S parameters, and power performance have been compared and demonstrated a great improvement from the conventional Curtice models.
Reliability and low-frequency noise measurements of InGaAsP multiple quantum well buried-heterostructure lasers
Authors: Letal Gregory , Smetona Saulius , Mallard Robert , Matukas Jonas , Palenskis Vilius , Pralgauskaite Sandra
Published: July 2002

Analysis of low-frequency noise characteristics is used to investigate the behavior of gain-coupled buried-heterostructure lasers. Devices which exhibit threshold current degradation during electrical and thermal overstress, as well as stable devices, are examined. In addition to examining the magnitudes of the optical and electrical noise as functions of current and frequency, the correlation between the electrical and optical noise is examined. It is shown that unreliable lasers exhibited white electrical and optical noises with negative correlation between them at threshold while the reliable devices did not. While the root cause of these characteristic noise differences is as of yet unknown, the present results suggest the potential utility of noise measurements as a means of predicting laser reliability and the development of low-cost screening techniques.
Ellipsometric method for real time control of thin film deposition on imperfect substrates
Authors: Hofrichter A. , Heitz T. , Bulkin P. , Drevillon B.
Published: July 2002

In this work we present a method of the ellipsometric control for optical filter deposition. This control procedure uses the length of the real time ellipsometric trajectory as a control parameter with respect to the length of precalculated target trajectory. This control method has been adapted for substrates whose optical structure cannot be adequately modeled. In this case an effective refractive index and absorption coefficient is assigned to the substrate, which is determined by computing the length of the experimental trajectory from the deposition of a reference layer. This effective refractive index is used to compute the target trajectory. The control procedure has been applied to the deposition of a graded index antireflection coating on Corning and float glass by plasma enhanced chemical vapor deposition. Spectrophotometry transmission measurements show the high efficiency of the control method with respect to uncontrolled filter deposition.
Determination of structural parameters in heterojunction bipolar transistors by x-ray diffraction with (002) reflection
Authors: Shen A. , Griswold E. M. , Hillier G. , Dang L. , Kuhl A. , Arès R. , Clark D. , Calder I. D.
Published: July 2002

Both GaAs and InP heterojunction bipolar transistors (HBT’s) were analyzed by x-ray diffraction measurements with (002) reflection. For GaAs HBT’s, the InGaP emitter thickness and alloy composition were accurately determined. For InP HBT’s, both the base and emitter layer thicknesses could be extracted. Thickness determined from x-ray diffraction measurements agreed well with that measured by transmission electron microscopy.
High-density plasma-induced etch damage of wafer-bonded AlGaInP/mirror/Si light-emitting diodes
Authors: Wuu D. S. , Horng R. H. , Huang S. H. , Chung C. R.
Published: July 2002

Dry etch of wafer-bonded AlGaInP/mirror/Si light-emitting diodes (LEDs) with planar electrodes was performed by high-density plasma using an inductively coupled plasma (ICP) etcher. The etching characteristics were investigated by varying process parameters such as Cl2/N2 gas combination, chamber pressure, ICP power and substrate-bias power. The corresponding plasma properties (ion flux and dc bias), in situ measured by a Langmuir probe, show a strong relationship to the etch results. With a moderate etch rate of 1.3 μm/min, a near vertical and smooth sidewall profile can be achieved under a Cl2/(Cl2+N2) gas mixture of 0.5, ICP power of 800 W, substrate-bias power of 100 W, and chamber pressure of 0.67 Pa. Quantitative analysis of the plasma-induced damage was attempted to provide a means to study the mechanism of leakage current and brightness with various dc bias voltages (−110 to −328 V) and plasma duration (3–5 min) on the wafer-bonded LEDs. It is found that the reverse leakage current increases and the brightness decreases rapidly as the dc bias increases, which is a clear indication of severe damage accumulation in the sidewall. However, once a low-etch-rate condition (long duration of plasma treatment) is chosen to facilitate smooth sidewall and profile, the accumulated charge on the etched surface may not have enough time to relieve and make the leakage current increase. Finally, an effective recovery method is developed, where the plasma-induced damage can be partially restored after rapid thermal annealing at 450 °C in N2 ambience.
Low temperature SF6/O2 electron cyclotron resonance plasma etching for polysilicon gates
Authors: Hasan I. , Pawlowicz C. A. , Berndt L. P. , Tarr N. G.
Published: July 2002

The use of SF6/O2 chemistry for polysilicon gate etching at a low temperature in an electron cyclotron resonance plasma etcher is considered. Sidewall angle, polysilicon etch rate, and selectivity to gate oxide and photoresist are reported as functions of temperature in the range −125 °C to 25 °C. The addition of oxygen to the plasma allows anisotropic etching to be obtained at higher temperatures than with pure SF6. 0.3 μm long gates were formed at −100 °C using an etch process with ≈3:1 selectivity to photoresist and ≈14:1 selectivity to oxide.
Growth and coalescence evolution of InAs on GaAs by molecular beam epitaxy
Authors: Nee Tzer-En , Lin Ray-Ming , Hsieh Li-Zen , Chang Liann-Be
Published: July 2002

InAs layers, grown on GaAs substrates using molecular beam epitaxy, has been systematically investigated. Through the observation of pyrometer readings, it was found that the transition of both the growth mode and the surface morphology of InAs layers are strongly dependent on the As4/In flux ratio and the substrate temperature. Cross-sectional transmission electron microscopy images showed that effective reduction in defect density resulting from the InAs/GaAs interface was achieved for InAs layers with a thickness of only 1.5 μm.
Thickness-dependent renormalization of strain effects on self-organized InAs quantum dots grown on GaAs
Authors: Lin Ray-Ming , Nee Tzer-En , Tsai Mei-Ching , Chang Yuan-Hao , Fan Ping-Lin , Chang Rong-Seng
Published: July 2002

The thickness-dependent renormalization of strain effects on self-organized InAs quantum dots has been systematically investigated. The photoluminescence-emission energy shift for the smaller quantum dots reveals both the hydrostatic and shear strain effects. However, the characteristics of the larger quantum dots are attributed predominantly to the hydrostatic effect. Furthermore, due to the elastic stiffness constant difference, the GaAs matrix-dependent characteristics were prevailed in the smaller quantum dots, while InAs-like properties were observed in the larger ones. All results indicate that the strain effect plays a major role in the emission energy of InAs quantum-dot heterosystems.
Submicron, high speed complementary metal–oxide semiconductor compatible metal–semiconductor–metal photodetector
Authors: DeVries A. M. , Tarr N. G. , Cheben P. , Grant P. D. , Janz S. , Xu D.-X.
Published: July 2002

Metal–semiconductor–metal photodetectors with electrode spacing of 0.5 μm have been fabricated on polysilicon films formed by low-pressure chemical vapor deposition. The detectors give a responsivity of 8 mA/W at 980 nm, and a 3-dB bandwidth of 1.5 GHz. Steady-state and transient photoresponse both appear to be limited by recombination and trapping at energy levels within the forbidden gap.
Residual-Gas Analysis of a DC-705 Oil-Diffusion-Pumped uhv System
Authors: Gosselin Charles M. , Bryant Paul J.
Published: July 2002

The residual gases present in a DC-705 oil-diffusion-pump uhv system have been determined as a function of various trapping conditions. The system was equipped with a metal 2-in. oil-diffusion pump in series with a specially designed trap in which zeolite was used. The configuration of the trap permitted the trapping zone to be immersed in cryogenic liquids, e.g., LN2. The effectiveness of the trap was determined as a function of temperature. A comparison of the residual gases is made for six conditions, including three trapping temperatures, while operating with zeolite and without zeolite.