Gregory F. Cardinale

Sandia National Laboratories, Albuquerque, New Mexico, United States

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Publications (37)24.56 Total impact

  • J L Skinner, G F Cardinale, A A Talin, R W Brocato
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    ABSTRACT: The effect of critical dimension (CD) variation and metallization ratio on the efficiency of energy conversion of a surface acoustic wave (SAW) correlator is examined. We find that a 10% variation in the width of finger electrodes predicts only a 1% decrease in the efficiency of energy conversion. Furthermore, our model predicts that a metallization ratio of 0.74 represents an optimum value for energy extraction from the SAW by the interdigitated transducer (IDT).
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 03/2006; 53(2):497-501. · 1.82 Impact Factor
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    ABSTRACT: We report the surface acoustic wave (SAW) correlator devices fabricated using nanoimprint lithography. Using step-and-flash imprint lithography (S-FIL), we produced SAW correlator devices on 100 mm diameter z-cut LiNbO3 devices and an aluminum metal etch process. On the same chip layout, we fabricated SAW filters and compared both the filters and correlators to similar devices fabricated using electron-beam lithography (EBL). Both S-FIL- and EBL-patterned correlators and SAW filters were analyzed using a bit-error rate tester to generate the signal and a parametric signal analyzer to evaluate the output. The NIL filters had an average center frequency of 2.38 GHz with a standard deviation of 10 MHz. The measured insertion loss averaged -31 dB. In comparison, SAW filters fabricated using EBL exhibited a center frequency of 2.39 GHz and a standard deviation of 100 kHz. Based on our preliminary results, we believe that S-FIL is an efficient and entirely viable fabrication method to produce quality SAW filters and correlators.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 01/2004; 22(6):3265-3270. · 1.36 Impact Factor
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    ABSTRACT: We describe the use and characterization of a bilevel photoresist for extreme ultraviolet lithography (EUVL). The bilevel photoresist consists of a combination of a commercially available polydimethylglutarimide (PMGI) bottom layer and an experimental EUVL photoresist top (imaging) layer. We measure the sensitivity of PMGI to EUV exposure dose as a function of photoresist prebake temperature, and using this data, optimize a metal liftoff process. Reliable fabrication of 700 Å thick Au structures with sub-1000 Å critical dimensions is achieved, even without the use of a Au adhesion layer, such as Ti. Using the bilevel photoresist process, we fabricate an electrode array test structure, designed for electrical characterization of molecules and nanocrystals. © 2004 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 01/2004; 22(2). · 1.36 Impact Factor
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    ABSTRACT: The relationships between polymer molecular weight, surface roughness measured by Atomic Force Microscopy (AFM), and EUV line edge roughness (LER), were studied in four separate rounds of experiments. In Round 1, EUV-2D (XP98248B) was prepared with seven levels of added base. These seven resists were patterned using EUV lithography; the LER was determined using 100 nm dense lines. The LER of the seven resist dramatically decreases with increasing level of base. These LER results were compared with the surface roughness of these resists after development for unexposed and DUV (248 nm) exposed surfaces. In Rounds 2-4, we evaluated three sets of EUV-2D type resists prepared with polymers having Mw of 2.9, 4.9, 6.1, 9.1, 16.1, and 33.5 Kg/mole. EUV LER and surface roughness were determined for each resist. In Round 2, the polymers were substituted into the EUV-2D resist matrix with no other formulation changes. In Round 3, the PAG level was decreased with increasing polymer Mw, to obtain a constant unexposed fill thickness loss (UFTL) for all six resists. In Round 4, both PAG level and base level were modified to yield six resists with similar sensitivity and EFTL. These experiments have led to conclusion about the impact of polymer molecular weight on imaging LER and AFM surface roughness, as well as elucidating the relationship between all three.
    Proc SPIE 01/2003;
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    ABSTRACT: While interferometry is routinely used for the characterization and alignment of lithographic optics, the ultimate performance metric for these optics is printing in photoresist. The comparison of lithographic imaging with that predicted from wavefront performance is also useful for verifying and improving the predictive power of wavefront metrology. To address these issues, static, small-field printing capabilities have been added to the EUV phase- shifting point diffraction interferometry implemented at the Advanced Light Source at Lawrence Berkeley National Laboratory. The combined system remains extremely flexible in that switching between interferometry and imaging modes can be accomplished in approximately two weeks.
    Proc SPIE 07/2002;
  • Peiyang Yan, Chih-wei Lai, Gregory F. Cardinale
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    ABSTRACT: In this paper, the printability of Extreme ultraviolet (EUV) mask contact layer defects at 90 nm contact size and above is studied via ultra-thin DUV resist and 10X EUV Microstepper. The EUV mask contact defect size requirement is determined by taking into account the wafer process critical dimension (CD) variability. In the experiment, two types of contact mask defect were studied. They are opaque defect placed at both edge and center of a contact and clear defect at edge of a contact. The programmed EUV absorber defect mask was fabricated by subtractive metal patterning on a Mo/Si multilayered-coated silicon wafer substrate. The 10X experimental EUV lithography system with 13.4 nm exposure wavelength and 0.088 NA imaging lens was used to expose the programmed defect mask. The response of the printed resist contact area to the metal absorber mask defect area is measured under different process conditions, i.e., different exposure doses. It is found that the EUV resist contact area responds to the mask defect area linearly for small mask defects. From such a set of contact area change vs. defect area response lines, the allowable absorber mask defect requirement for the contact layer is assessed via statistical explanation of the printable mask defect size, which is tied to the wafer process specifications and the actual wafer process CD controllability. Our results showed that a clear and an opaque intrusion corner absorber mask defect as small as 70 - 80 nm (4X) is printable for 90 nm contacts when 10% contact area change (or 5% contact DC change) due to defect alone is allowed. The effect of an opaque defect at center of a contact is found similar to that of corner opaque defect for smaller defect. It becomes much worse than that of at edges when defect is large. Based on the statistical defect printability analysis method that we have developed, the printable mask defect size can always be re-defined without additional data collection when the process controllability or the process specification changes.
    Proc SPIE 07/2000;
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    ABSTRACT: The thickness of the photoresist directly impacts the etch stand off and may impact the number of defects in the spin- coated film. However, the maximum imaging layer thickness for extreme ultraviolet lithography (EUVL) is limited by absorption of the radiation. Attenuation in photoresist materials at relevant EUV wavelengths was calculated with atomic extinction coefficients provided from Henke et al. The calculations indicated that photoresist materials have an optical density (O.D.) of 4.0 micrometer-1 (base e) so that 100 nm thick imaging layers have approximately 67% transmission at 13.4 nm wavelength. Using Prolith/3DTM (Finle Technologies, Austin, TX) simulations of the effect of highly attenuating materials on sidewall slope were done and shown to be small. Imaging experiments were performed in a commercially-available DUV resist material on the 10 X II microstepper and with an improved EUV resist formulation. The imaging results agreed well with the calculations. Top down and cross-section images showed good sidewall profiles in 95 nm thick films at the nominal dose because over 68% of the energy was transmitted through the film. When the thickness of the film was increased, the dose was increased slightly to compensate for the absorption while good sidewall profiles and linearity were maintained. Photoresist thicknesses as high as 145 nm were imaged with a 35% increase in dose. Results are also shown for a single layer resist exposed at 175 nm thickness with only slight sidewall degradation. It is shown that the imaging layer thickness for 13.4 nm lithography is likely to be 120 +/- 15 nm. If 11.4 nm wavelength radiation is chosen for EUV lithography, it is shown that thicknesses of 170 nm is possible.
    Proc SPIE 07/2000;
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    ABSTRACT: Extreme Ultra-Violet lithography is one of the leading next generation lithography options. Currently, EUV masks are routinely made of reflective mirrors made of Mo/Si multi- layers, which have a peak reflectivity of 67.5% at a wavelength of 13.4 nm. However, in order to increase the throughput of an EUVL system, a new set of Be-based multi- layers are being developed, which have a peak reflectivity of near 70% at 11.4. The two materials that have recently been developed are Mo/Be and MoRu/Be multi-layers. Beryllium based multi-layer masks show great promise for a significant increase in the lithography system throughput (2 - 3X over the current Mo/Si multi-layer mask) due to their increased reflectivity and bandwidth at 11.4 nm where the xenon laser plasma source is more intense. We have successfully developed a process to fabricate masks using Be-based multi-layers. The absorber stack consists of TaSiN (absorber), SiON (repair buffer) and Cr (conductive etch stop) deposited on the multi- layer mirror. Lawrence Livermore National Laboratory supplied the Mo/Be and MoRu/Be multi-layer mirrors used to fabricate the masks. Completed masks were exposed at Sandia National Laboratories' 10X EUV exposure system and equal lines and spaces down to 80 nm were successfully printed. The paper addresses the issues and challenges to fabricate the mask using Be-based multi-layers and a comparison will be made with the Mo/Si multi-layer mask patterning process.
    Proc SPIE 07/2000;
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    ABSTRACT: In an attempt to narrow the choice for an absorber used in EUV masks, different materials are being evaluated. These materials need to meet the absorber requirements of EUV absorbance, emissivity, inspection, and repair, to name a few. We have fabricated masks using Cr absorbers. The absorber stack consists of a repair buffer of SiON and a conductive etch stop of Cr sandwiched between the SiON repair buffer film and the Mo/Si multilayer mirror deposited on a Si wafer. However, to increase the process latitude, the Cr etch stop needs to be removed from the stack, in particular for mask repair. The absorber layer was patterned using commercial DUV resist and the pattern was transferred using reactive ion etching (RIE) with halogen-based gases. Completed masks exhibited negligible shift in the centroid wavelength of reflectivity and less than 2% loss in peak reflectivity due to mask patterning. Completed masks were exposed at Sandia National Laboratories' 10X EUV exposure system and equal lines and spaces down to 80 nm were successfully printed. The masks were also imaged in a microscope with 248 nm wavelength, and the focused ion beam repair selectivity to the buffer layer (SiON) was established. The paper summarizes the mask fabrication process, EUV printability, mask repair, inspection and emissivity for EUVL masks with Cr absorber.
    Proc SPIE 07/2000;
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    ABSTRACT: Improvements in mask blank yield by the reduction in defects dramatically reduces the reticle cost of any lithography. Extreme ultraviolet lithography (EUVL) masks typically consist of a substrate coated with reflective multilayer (ML) materials (e.g., Mo and Si), followed by a sacrificial or “repair” layer (e.g., SiO2) and top absorber layer material (e.g., Cr or TaSiNx). Defects of the following two types exist: substrate and absorber defects. Substrate defects are generally below the absorber and buffer layers, i.e., at the substrate–ML interface or within the ML stack, whereas the absorber defects are located at the absorber layer. In addition, the printability of substrate-type defects may be reduced by coating the defects with a planarizing or smoothing layer. In this work, we discuss simulation and experimental results that compare the printability of programmed defect reticles with and without smoothing layers covering the programmed defect. We propose several criteria for smoothing layer specifications that are necessary to mitigate a size range of defects for an EUV imaging system. © 2000 American Vacuum Society.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2000; 18(6):2944-2949. · 1.36 Impact Factor
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    ABSTRACT: We report on the comparison of defect printability experimental results with at-wavelength defect inspection and printability modeling at extreme ultraviolet (EUV) wavelengths. Two sets of EUV masks were fabricated with nm- scale substrate defect topographies patterned using a sacrificial layer and dry-etch process, while the absorber pattern was defined using a subtractive metal process. One set of masks employed a silicon dioxide film to produce the programmed defects, whereas the other set used chromium films. Line-, proximity- and point-defects were patterned and had lateral dimensions in the range of 0.2 micrometer X 0.2 micrometer to 8.0 micrometer X 1.5 micrometer on the EUV reticle, and a topography in the range of 8 nm - 45 nm. Substrate defect topographies were measured by atomic force microscopy (AFM) before and after deposition of EUV-reflective Mo/Si multilayers. The programmed defect masks were then characterized using an actinic inspection tool. All EUVL printing experiments were performed using Sandia's 10x- reduction EUV Microstepper, which has a projection optics system with a wavefront error less than 1 nm, and a numerical aperture of 0.088. Defect dimensions and exposure conditions were entered into a defect printability model. In this investigation, we compare the simulation predictions with experimental results.
    Proc SPIE 12/1999;
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    ABSTRACT: The capabilities of the EUV 10x microstepper have been substantially improved over the past year. The key enhancement was the development of a new projection optics system with reduced wavefront error, reduced flare, and increased numerical aperture. These optics and concomitant developments in EUV reticles and photoresists have enabled dramatic improvements in EUV imaging, illustrated by resolution of 70 nm dense lines and spaces (L/S). CD linearity has been demonstrated for dense L/S over the range 100 nm to 80 nm, both for the imaging layer and for subsequent pattern transfer. For a +/- 10 percent CD specification, we have demonstrated a process latitude of +/- micrometers depth of focus and 10 percent dose range for dense 100 nm L/S.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    06/1999;
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    ABSTRACT: The capabilities of the EUV 10x microstepper have been substantially improved over the past year. The key enhancement was the development of a new projection optics system with reduced wavefront error, reduced flare, and increased numerical aperture. These optics and concomitant developments in EUV reticles and photoresists have enabled dramatic improvements in EUV imaging, illustrated by resolution of 70 nm dense lines and spaces (L/S). CD linearity has been demonstrated for dense L/S over the range 100 nm to 80 nm, both for the imaging layer and for subsequent pattern transfer. For a +/- 10 percent CD specification, we have demonstrated a process latitude of +/- micrometers depth of focus and 10 percent dose range for dense 100 nm L/S.
    Proc SPIE 06/1999;
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    ABSTRACT: In the last two years, we have developed tow Extreme UV (EUV) mask fabrication process flows, namely the substractive metal and the damascene process flows, utilizing silicon wafer process tools. Both types of EUV mask have been tested in a 10X reduction EUV exposure system. Dense lines less than 100 nm in width have been printed using both 0.6 micrometers thick top surface imaging resists and ultra-thin DUV resist. The EUV masks used in EUV lithography development work have been routinely made by using the current wafer process tools. The two EUV mask processes that we have developed both have some advantages and disadvantages. The simpler subtractive metal process is compatible with the current reticle defect repair methodologies. On the other hand, the more complex damascene process facilitates mask cleaning and particle inspection.
    Proc SPIE 06/1999;
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    ABSTRACT: Extreme UV Lithography (EUVL) is one of the leading candidates for the next generation lithography, which will decrease critical feature size to below 100 nm within 5 years. EUVL uses 10-14 nm light as envisioned by the EUV Limited Liability Company, a consortium formed by Intel and supported by Motorola and AMD to perform R and D work at three national laboratories. Much work has already taken place, with the first prototypical cameras operational at 13.4 nm using low energy laser plasma EUV light sources to investigate issues including the source, camera, electro- mechanical and system issues, photoresists, and of course the masks. EUV lithograph masks are fundamentally different than conventional photolithographic masks as they are reflective instead of transmissive. EUV light at 13.4 nm is rapidly absorbed by most materials, thus all light transmission within the EUVL system from source to silicon wafer, including EUV reflected from the mask, is performed by multilayer mirrors in vacuum.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    04/1999;
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    ABSTRACT: In two separate experiments, we have successfully demonstrated the transfer of dense- and loose-pitch line/space (L/S) photoresist features, patterned with extreme ultraviolet (EUV) lithography, into an underlying hard mask material. In both experiments, a deep-UV photoresist (∼90 nm thick) was spin cast in bilayer format onto a hard mask (50–90 nm thick) and was subsequently exposed to EUV radiation using a 10× reduction EUV exposure system. The EUV reticle was fabricated at Motorola (Tempe, AZ) using a subtractive process with Ta-based absorbers on Mo/Si multilayer mask blanks. In the first set of experiments, following the EUV exposures, the L/S patterns were transferred first into a SiO2 hard mask (60 nm thick) using a reactive ion etch (RIE), and then into polysilicon (350 nm thick) using a triode-coupled plasma RIE etcher at the University of California, Berkeley, microfabrication facilities. The latter etch process, which produced steep (≫85°) sidewalls, employed a HBr/Cl chemistry with a large (≫10:1) etch selectivity of polysilicon to silicon dioxide. In the second set of experiments, hard mask films of SiON (50 nm thick) and SiO2 (87 nm thick) were used. A RIE was performed at Motorola using a halogen gas chemistry that resulted in a hard mask-to-photoresist etch selectivity ≫3:1 and sidewall profile angles ≥85°. Line edge roughness (LER) and linewidth critical dimension (CD) measurements were performed using Sandia’s GORA© CD digital image analysis software. Low LER values (6–9 nm, 3σ, one side) and good CD linearity (better than 10%) were demonstrated for the final pattern-transferred dense polysilicon L/S features from 80 to 175 nm. In addition, pattern transfer (into polysilicon) of loose-pitch (1:2) L/S features with CDs≥60 nm was demonstrated. © 1999 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 01/1999; 17:2970-2974. · 1.36 Impact Factor
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    ABSTRACT: We propose the use of optical proximity correction on absorber features to compensate for the effect of subresolution multilayer defects that would otherwise induce a critical error in linewidth. Initial experiments have been performed which validate this concept. Process window simulations quantify the practical limits of this technique. (c) 1999 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 01/1999; 17(6). · 1.36 Impact Factor
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    ABSTRACT: We propose the use of optical proximity correction on absorber features to compensate for the effect of sub-resolution multilayer defects that would otherwise induce a critical error in linewidth. A series of defect printability and compensation experiments utilizing programmed multilayer defects are presented which demonstrate this approach. The amount of absorber removal for defect compensation depends on system imaging performance and the quality of the absorber removal process. A process flow for the mask fabrication, defect characterization and compensation is presented.
    Proc SPIE 01/1999;
  • Journal of Vacuum Science and Technology-Section B-Microelectronics Nanometer Structur. 01/1999; 17(6):3024-3028.
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    ABSTRACT: Extreme ultraviolet (EUV) lithography masks were fabricated using a stack of TaSi or TaSiN (absorber), SiON (repair buffer), and Cr (conductive etch stop) on a Mo/Si multilayer mirror deposited on a Si wafer. High-resolution structures were exposed using a commercial i-line resist, and the pattern was transferred using both electron cyclotron resonance and reactive ion etching with halogen-based gases. Process temperatures to fabricate these reticles were always maintained below 150 degree sign C. EUV properties after patterning were measured using a synchrotron source reflectometer. Completed masks exhibited a negligible shift in the peak wavelength and less than 2% loss in reflectivity due to processing. Qualified masks were exposed with a 10x EUV exposure system. The exposures were made in 80-nm-thick DUV resist and with numerical apertures (NA) of 0.08, 0.088, and 0.1. Resolution down to 70 nm equal lines and spaces was achieved at a NA of 0.1. Line edge roughness in the resist features was 5.5 nm (3Ï, one side), and the depth of focus for {+-}10% CD control was {+-}1 μm for 100 nm equal lines and spaces. (c) 1999 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 01/1999; 17(6):3029-3033. · 1.36 Impact Factor

Publication Stats

153 Citations
24.56 Total Impact Points

Institutions

  • 1997–2004
    • Sandia National Laboratories
      • Semiconductor Material and Device Sciences Department
      Albuquerque, New Mexico, United States
  • 1994–1996
    • CSU Mentor
      Long Beach, California, United States
  • 1993–1996
    • University of California, Davis
      • Department of Chemical Engineering and Materials Science
      Davis, California, United States