Browsing by Author "Smayling, Michael C."

Now showing 1 - 9 of 9
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    Analysis of passive mode-locking in lasers
    (1975) Smayling, Michael C.; Rabson, Thomas A.
    The passively mode-locked laser is modeled as a regenerative oscillator. An organic dye used as a saturable absorber is treated as the only nonlinear element in the feedback loop. Using a transcendental equation to represent the transfer function of the inhomogeneously broadened, "energy saturated" dye, numerical analysis shows that a Gaussian pulse is a steady state solution. For the example considered, in which an NdsYAG laser is mode-locked by an Eastman 974 dye, the initial shortening of the pulse by the dye is .6%, and approximately 1 to 2 passes are required to reach steady state.
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    Enhanced Microlithography Using Combined Phase Shifting and Off-axis Illumination
    (Japanese Journal of Applied Physics, 1995-12-01) Erdelyi, Miklos; Bor, Zsolt; Cavallaro, Joseph R.; Szabo, Gabor; Wilson, William L.; Sengupta, Chaitali; Smayling, Michael C.; Tittel, Frank K.; Center for Multimedia Communication
    Off-axis illumination is a promising optical microlithography technique which can be used to improve the image quality of line-space patterns. With this method the image is produced by the zero and first order diffracted beams. Due to the intensity difference between these two order diffracted beams the contrast of the image cannot be unity. This paper demonstrates the optical enhancement that can be achieved by a combination of interferometric phase shifting and off-axis illumination. In such an arrangement the mask is illuminated symmetrically from both the front and back sides, and not two but in fact four–(two zero and two first)–order beams produce the image. We show experimentally that the contrast of the image can be improved if the phase difference between the reflected and transmitted beams is π, and the intensity of the transmitted beam is about 13% of the reflected beam. This improved quality image with feature sizes of 0.4 µm was recorded in a photoresist using an Ar+ ion laser operating at 457.9 nm.
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    Generation of diffraction-free beams for applications in optical microlithography
    (American Vacuum Society, 1997-03-01) Erdelyi, Miklos; Horvath, Zoltan L.; Szabo, Gabor; Bor, Zs.; Tittel, Frank K.; Cavallaro, Joseph R.; Smayling, Michael C.; Center for Multimedia Communication
    A new concept based on a Fabry–Perot interferometer for the generation of nondiffracting Bessel beams is described and proposed for potential applications in microlithography such as the fabrication of small isolated patterns. It was experimentally demonstrated that the depth of focus can be increased by a factor of about 2, and simultaneously the transverse resolution improved by a factor of 1.6, when using this technique to image contact holes. The properties of simultaneous imaging of two contact holes were also investigated. It was shown experimentally that, even in the most critical case ~when the first diffraction rings overlap!, undesirable interference effects between the adjacent contact holes can be eliminated by means of a phase shifting technique.
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    An Integrated CAD Framework Linking VLSI Layout Editors and Process Simulators
    (SPIE, 1996-03-01) Sengupta, Chaitali; Erdelyi, Miklos; Bor, Zsolt; Cavallaro, Joseph R.; Smayling, Michael C.; Szabo, Gabor; Tittel, Frank K.; Wilson, William L.; Center for Multimedia Communication
    As feature sizes in VLSI circuits extend into the far sub-micron range, new process techniques, such as using phase shifting masks for photolithography, will be needed. Under these conditions, the only means for the circuit designer to design compact and efficient circuits with good yield capabilities is to be able to see t he effect of different design approaches on manufactured silicon, instead of solely relying on conservative general design rules. The Integrated CAD Framework accomplishes this by providing a link between a layout editor (Magic), advanced photolithographic techniques such as phase shifted masks, and a process simulator (Depict). This paper discusses some applications of this tool. A non-conventional process technique involving interferometric phase shifting and off-axis illumination has been evaluated using the tool. Also, a feature of the CAD Framework which allows representation of a phase shifted mask, together with its layout analysis capability has been used to compact a piece of layout by inserting phase shifted elements into it.
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    Interferometric Phase Shift Technique for High Resolution Deep UV Microlithography
    (SPIE, 1994-09-01) Tittel, Frank K.; Cavallaro, Joseph R.; Kido, Motoi; Smayling, Michael C.; Szabo, Gabor; Wilson, William L.; Center for Multimedia Communication
    A new phase shifting technique based on interferometry has been developed which is especially suited for deep-UV microlithography. Using only a single layer chromium mask, with no additional phase shift elements, significant resolution and contrast enhancement over conventional transmission lithography can be achieved. Both computer simulations, as well as experiments using a CCD camera and UV photoresist confirm the capabilities of this new approach. Using a relatively simple experimental setup and an illumination wavelength of 355 nm, lines with feature sizes as find as 0.3 um were achieved.
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    A New Interferometric Phase-Shifting Technique for Sub-half-micron Laser Microlithography
    (SPIE, 1995-02-01) Erdelyi, Miklos; Sengupta, Chaitali; Bor, Zsolt; Cavallaro, Joseph R.; Kido, Motoi; Smayling, Michael C.; Tittel, Frank K.; Wilson, William L.; Szabo, Gabor; Center for Multimedia Communication
    This paper reports recent progress in achieving sub-half-micron feature sizes with UV laser illumination based on a novel interferometric phase shifting (IPS) technique. In the IPS arrangement, the intensity and amount of phase shift of the shifted beam can be controlled continuously and independently using the same mask. Consequently the method can be considered as a convenient general testbed for practical phase shifting concepts such as strong, weak and attenuated phase shifting. Recent measurements of the lithographic performance of a new concept are reported where phase shifting is combined with off-axis illumination. Experimental as well as simulation data are used to demonstrate this new method. A lithography simulator, Depict from Technology Modeling Associates, Inc. and a related Integrated CAD Framework which is being developed at Rice University was used to simulate and evaluate the performance of the IPS scheme.
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    Sub-quarter micron contact hole fabrication using annular illumination
    (SPIE, 1996-03-01) Erdelyi, Miklos; Bor, Zsolt; Szabo, Gabor; Cavallaro, Joseph R.; Smayling, Michael C.; Tittel, Frank K.; Wilson, William L.; Center for Multimedia Communication
    Details of an experimental demonstration of a contact hole imaging system are reported in which the depth of focus is increased by a factor of about 3.5 using annular illumination. Due to spatial filtering and nonlinearity of the photoresist, the resolving power was enhanced by 52% and it was possible to pattern a 0.28 um contact hole in photoresist deposited on a silica substrate. This technique is capable of fabricating sub-quarter micron holes using excimer laser radiation at 193 nm.
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    Submicron Optical Lithography Based on a New Interferometric Phase Shifting Technique
    (Japanese Journal of Applied Physics, 1995-08-01) Kido, Motoi; Szabo, Gabor; Cavallaro, Joseph R.; Wilson, William L.; Smayling, Michael C.; Tittel, Frank K.; Center for Multimedia Communication
    This paper reports the computer simulation and experimental demonstration of a new phase shifting technique based on interferometry that is especially suited for deep ultraviolet (UV) microlithography. Significant resolution and contrast enhancement can be achieved using a chrome binary mask. Image analysis based on charge coupled device (CCD) detection and patterns recorded in UV photoresist has been used to study the capabilities of this new approach. Lines with a feature size as fine as 0.3 µm have been demonstrated using 355 nm illumination.
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    Ultrahigh Resolution Lithography with Excimer Lasers
    (Kluwer Academic Publishers, 1995-07-01) Tittel, Frank K.; Erdelyi, Miklos; Sengupta, Chaitali; Bor, Zsolt; Szabo, Gabor; Cavallaro, Joseph R.; Smayling, Michael C.; Wilson, William L.; Center for Multimedia Communication
    The photolithography process is central to integrated circuit fabrication. Through this process an integrated circuit is patterned by imaging a photomask onto a layer of photoresist. The light source currently being used by the semiconductor industry in the photolithography process for 0.35 micron feature size is the mercury lamp. As the feature size for integrated circuits moves below 0.35 microns, a new source of shorter wavelength light and higher power must be found to replace the mercury lamp.