-
[show abstract]
[hide abstract]
ABSTRACT: Results from a spectromicroscopic study of the formation of TiSi2 in patterned structures are reported. An x-ray spectromicroscope was used to acquire spectra and images with photoabsorption signals using synchrotron radiation. A patterned TiSi2 sample with feature sizes ranging from 100 μm to 0.1 μm was studied. The silicidation reactions were carried out in ultrahigh vacuum using rapid thermal processing. Lateral variations in the local chemistry of the titanium silicide could be directly imaged and are attributed to the formation of the C54 phase in large areas and the C49 phase at feature edges and in narrow features. © 1997 American Institute of Physics.
Applied Physics Letters 07/1997; 71(1):55-57. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In the fabrication of a typical refractory X-ray lithography mask, the pattern transfer process subjects the membrane/pattern to the non-uniform deposition and removal of multiple stressed layers. This removal process can result in unacceptably large pattern distortions in the final mask. This paper presents relationships obtained from finite element (FE) modeling, between pattern distortions and the following mask parameters: membrane material, thickness, size and stress, and the removed film material, thickness and stress. In addition, the sensitivity of the distortions was investigated for stress gradients present in the removed film. Finally, the capability of these models to predict pattern specific distortions (PSD) is demonstrated.
Microelectronic Engineering - MICROELECTRON ENG. 01/1997; 35(1):549-552.
-
[show abstract]
[hide abstract]
ABSTRACT: We present a study of the effect of multilayer‐surface‐roughness‐induced scattering in the image formation of the Schwarzschild objective (SO) used in the spectromicroscope MAXIMUM. The two mirrors comprising the SO are coated with Ru/B 4 C multilayers that have a peak reflectivity at 130 eV. We had long observed that a diffuse x‐ray background surrounds the focused x‐ray spot. The spatial resolution remains at 0.1 μm in spite of this. However, since a significant fraction of the flux is lost to the background, since too large an area of the sample is illuminated, and since the S/N ratio is degraded, the origins of this effect merit investigation. This diffuse background resulting from x‐ray scattering at the surface of the mirrors was mapped out using bidirectional knife edge scans. Complementary surface roughness simulations were carried out with the ray‐tracing program SHADOW. AFM experiments were also done to directly measure the surface roughness and power spectrum of representative multilayers. Following curve fitting, it was possible to classify Gaussian components in both the measured and simulated profiles as arising from scattering occurring at either the convex primary mirror or the concave secondary mirror. Together with geometrical analysis, these techniques permitted us to track the image formation process of an actual optical system in the presence of surface roughness. © 1996 American Institute of Physics.
Review of Scientific Instruments 10/1996; · 1.37 Impact Factor
-
John T. Welnak,
H. Solak,
J. Wallace, F. Cerrina,
F. Barbo,
M. Bertolo,
A. Bianco,
S. Di Fonzo,
S. Fontana,
W. Jark,
F. Mazzolini,
R. Rosei,
A. Savoia,
J.H. Underwood,
G. Margaritondo
[show abstract]
[hide abstract]
ABSTRACT: High brightness, third‐generation synchrotrons allow diffraction‐limited performance and large flux for scanning photoemission microscopes. A new microscope, SuperMAXIMUM, is being developed at the University of Wisconsin Center for X ray Lithography in collaboration with the Sincrotrone Trieste. The beamline, being built in Trieste, uses a variable angle spherical grating monochromator (VASGM). A combination of rotation of a plane mirror and rotation of the spherical grating keeps the slit positions and beam directions fixed. The microscope objectives are normal‐incidence, multilayer‐coated Schwarzschild objectives. The project, which is nearing completion, utilizes novel designs for optics alignment, sample rastering mechanics, and software control. We will discuss the project status, new designs, and techniques. © 1996 American Institute of Physics.
Review of Scientific Instruments 10/1996; · 1.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The MAXIMUM scanning x‐ray microscope, developed at the Synchrotron Radiation Center (SRC) at the University of Wisconsin – Madison, was implemented on the Advanced Light Source (ALS) in August of 1995. The microscope’s initial operation at SRC successfully demonstrated the use of a multilayer‐coated Schwarzschild objective for focusing 130 eV x‐rays to a spot size of better than 0.1 micron with an electron energy resolution of 250 meV. The performance of the microscope was severely limited because of the relatively low brightness of SRC, which limits the available flux at the focus of the microscope. The high brightness of the ALS is expected to increase the usable flux at the sample by a factor of 1000. We will report on the installation of the microscope on bending magnet beamline 6.3.2 at the ALS and the initial measurement of optical performance on the new source, and preliminary experiments on the surface chemistry of HF‐etched Si will be described. © 1996 American Institute of Physics.
Review of Scientific Instruments 10/1996; · 1.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The Schottky‐barrier formation of the Au/GaP (110) interface has been investigated by photoemission, in the presence of large surface photovoltage effects induced by the intense photon beam of a synchrotron‐radiation source. The surface photovoltage has been measured with a Kelvin probe. The largest surface photovoltage shift observed in the photoemission spectra was almost 1 eV. The Schottky barrier appears to be fully established at about 8 Å, while the surface photovoltage does not disappear until about 16 Å. The Schottky‐barrier height is 1.35±0.1 eV. The Kelvin‐probe results demonstrate directly that the photoemission data must be corrected for the surface photovoltage during the formation of the barrier but are insensitive to it once full coverage is obtained. © 1996 American Vacuum Society
Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 08/1996; · 1.25 Impact Factor
-
Review of Scientific Instruments - REV SCI INSTR. 01/1996; 67.
-
[show abstract]
[hide abstract]
ABSTRACT: Traditional x‐ray lithography mask radiation damage studies have concentrated on the pattern placement errors produced by stress changes within the mask membrane. The usual approach is to measure the location of fiducial marks on the mask membrane to measure the distortions for pre‐ and postirradiation. The measured distortions are not directly related to changes in individual mechanical properties of the membrane material. To isolate the individual mechanical parameters this study has utilized a silicon nitride membrane structure in the form of a bridge with lithographically patterned strain gauges to allow independent measurement of changes in the elastic modulus and Poisson’s ratio as a function of incident dose. It was found that the modulus of elasticity decreased by 37% for an incident dose of 114 kJ/cm<sup>2</sup> while the Poisson ratio for the material remained unchanged within the accuracy of the experiment. The results of these measurements have been incorporated into a finite element model to numerically determine the resulting distortions and compare them with published experimental results. © 1995 American Vacuum Society
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/1995; · 1.34 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Multilayer‐coated imaging systems for extreme ultraviolet (EUV) lithography at 13 nm represent a significant challenge for alignment and characterization. The standard practice of utilizing visible light interferometry fundamentally provides an incomplete picture since this technique fails to account for phase effects induced by the multilayer coating. Thus the development of optical techniques at the functional EUV wavelength is required. We present the development of two EUV optical tests based on Foucault and Ronchi techniques. These relatively simple techniques are extremely sensitive due to the factor of 50 reduction in wavelength. Both techniques were utilized to align a Mo–Si multilayer‐coated Schwarzschild camera. By varying the illumination wavelength, phase shift effects due to the interplay of multilayer coating and incident angle were uniquely detected. © 1995 American Vacuum Society
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/1995; · 1.34 Impact Factor
-
Physical review. B, Condensed matter 03/1995;
-
J. Welnak,
Z. Dong,
H. Solak,
J. Wallace, F. Cerrina,
M. Bertolo,
A. Bianco,
S. Di Fonzo,
S. Fontana,
W. Jark,
F. Mazzolini,
R. Rosei,
A. Savoia,
J. H. Underwood,
G. Margaritondo
[show abstract]
[hide abstract]
ABSTRACT: X ray microscopy excels on high‐brightness sources, such as the Advanced Light Source and ELETTRA, where there is a good match between the source and optics phase spaces. In these conditions, diffraction‐limited operation becomes possible with large flux. We will discuss the development of a second‐generation x ray scanning spectromicroscope; an evolution of the MAXIMUM project at the University of Wisconsin. The new tool is called SuperMAXIMUM and will be installed on ELETTRA in Trieste, Italy. © 1995 American Institute of Physics.
Review of Scientific Instruments 03/1995; · 1.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present an updated global model for x‐ray lithography based on realistic models for image formation, demonstrating how the extendibility of x‐ray lithography is well in the nanometer range. We apply these models to define the most convenient spectral range for x‐ray lithography manufacturing and the parameters of mirrors and filters to be used in an optimized beam line.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/1994; · 1.34 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This article studies the effect of mirror misalignment on run‐out overlay errors in a synchrotron radiation based x‐ray lithography system. Using the ES‐5 beam‐line installation at the CXrL as an example, we found that the current beamline mirror alignment method, which relies on the final beam shape and orientation at the mask‐wafer plane, is insensitive to the mirror grazing incident angle alignment. Simulations using the ray‐tracing program shadow indicate that a smaller than ±0.5‐mrad mirror grazing angle misalignment consumes the required run‐out overlay error budget of the beamline. A direct beamline run‐out overlay measurement technique based on the Hartmann method was developed for the beamline mirror alignment. This measurement technique was applied to our ES‐5 beamline mirror alignment procedure. The measurement results show that the beamline induced run‐out error of the installed ES‐5 beamline is less than 0.014 μm in both horizontal and vertical direction for a 25‐mm exposure field with a mask‐wafer gap of 40 μm. The across field run‐out error distribution is also compared with shadow simulation results. The good agreement between measurement and simulation data indicates that our measurement technique provides a sensitive, practical, and accurate method for x‐ray lithography beamline mirror alignment and evaluation.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/1994; · 1.34 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: EUV metrology is central to the successful commercialization of EUV projection lithography. Metrology carried out at the EUV wavelength of 13 nm enables a gain of {approximately}50 in precision when translated from visible light wavelengths. It also uniquely measures wavefront errors due to lateral variations in the inherent phase shift upon reflection from the multilayer coating. The authors present the development of two metrology techniques: EUV Foucault and Ronchi tests.
10/1994;
-
W. Ng,
A. K. Ray-chaudhuri,
S. Liang,
S. Singh,
H. Solak, F. Cerrina,
G. Margaritondo,
L. Brillson,
A. Franciosi,
J. H. Underwood,
J. B. Kortright,
R. C. C. Perera
Synchrotron Radiation News 03/1994; 7(2):25-29.
-
F. Gozzo,
M. Marsi,
H. Berger,
G. Margaritondo,
A. Ottolenghi,
A. K. Raychaudhuri,
W. Ng,
S Liang,
S Singh,
J. T. Welnak,
J. P. Wallace,
C. Capasso, F. Cerrina
[show abstract]
[hide abstract]
ABSTRACT: The interpretation of photoemission-spectromicroscopy studies of Au on GaSe requires a revision of established ideas about this interface, which has long been considered a prototype of Schottky-like systems. We find that the interface-formation process involves strong substrate-overlayer interactions, the release of free Ga, and the formation of interface species, and leads to a barrier height in total disagreement with the Schottky model. Furthermore, the space-resolving capabilities of our instruments revealed lateral inhomogeneities of the local overlayer thickness and of the local band bending.
Physical review. B, Condensed matter 01/1994;
-
[show abstract]
[hide abstract]
ABSTRACT: X‐ray masks are an expensive part of the x‐ray lithographic technology. The overall mask making process can be simplified and the cost reduced by a judiciously applied replication process. It is desirable that the copy has negligible feature bias and minimal placement distortion. It should therefore be produced by a process that has the greatest possible latitude with respect to dose and gap. In this article, it is described how these conditions are met. The latitude requirement is met by engineering the exposure system so that the source has a prescribed amount of spatial incoherence. This technique is an extension of the zero magnification method used by Wells et al. [J. Vac. Sci. Technol. B 10, 3221 (1992)]. This approach is particularly well suited for synchrotron‐based x‐ray lithography.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/1993; · 1.34 Impact Factor
-
A. K. Ray‐Chaudhuri,
W. Ng,
S. Liang,
S. Singh,
J. T. Welnak,
J. P. Wallace,
C. Capasso, F. Cerrina,
G. Margaritondo,
J. H. Underwood,
J. B. Kortright,
R. C. C. Perera
[show abstract]
[hide abstract]
ABSTRACT: Utilizing a Mo–Si multilayer coated Schwarzschild objective to focus 95 eV photons, we have recently demonstrated better than 0.1 μm resolution as a scanning x‐ray transmission microscope. Operating as a scanning photoemission microscope with submicron resolution, we have demonstrated its chemical mapping capabilities by studying a patterned Al/AlO x test structure. In addition, we have also studied the cleaved GaAs(110) surface and have identified lateral variations in the surface band bending on the scale of 100 meV. In both experiments, core level microspectroscopy was performed at selected points on the sample to elucidate the image contrast mechanisms.
Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 08/1993; · 1.25 Impact Factor
-
F. Cerrina,
A. K. Ray‐Chaudhuri,
W. Ng,
S. Liang,
S. Singh,
J. T. Welnak,
J. P. Wallace,
C. Capasso,
J. H. Underwood,
J. B. Kortright,
R. C. C. Perera,
G. Margaritondo
[show abstract]
[hide abstract]
ABSTRACT: Photoelectron energy distribution spectra taken for the first time on micrometer‐sized areas of cleaved GaAs(110) reveal rigid shifts from location to location in the photoemission core level peak energies, indicating band‐bending changes on a microscopic scale.
Applied Physics Letters 08/1993; · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This article presents a new optical metrology technique that has been developed at CXrL to investigate potential distortions induced in x‐ray masks during their fabrication, mounting, and x‐ray irradiation. The technique employs a Zygo phase‐shifting Fizeau interferometer to acquire the in‐plane distortion (IPD) and out‐of‐plane distortion (OPD) present in the masks. The interferometer measures the OPD directly, while IPD measurements are obtained with the aid of holographic gratings that have been printed onto the masks. When positioned at the Littrow angle of the gratings, the interferometer can acquire a retrodiffracted wavefront that contains the IPD information. Subtraction of the pre‐ and postdistortion interferograms yields the induced distortions. Computer models to simulate x‐ray mask distortions have been developed and implemented using ansys, a commercially available finite element analysis software package. Numerical results have shown excellent agreement with interferometric data. The authors believe that these new interferometric techniques and models should prove invaluable as metrologic and predictive tools for the measurement, characterization, and design of x‐ray masks in the 0.25 μm regime.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/1992; · 1.34 Impact Factor
