Rice Wireless

Permanent URI for this collection

https://hdl.handle.net/1911/21945
Formerly the Center for Multimedia Communications, Rice Wireless is part of the university's Electrical and Computer Engineering Department. More information about the group can be found at http://wireless.rice.edu/.

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Browsing Rice Wireless by Author "Bor, Zsolt"

Now showing 1 - 6 of 6
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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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    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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    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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    A New Phase Shifting Technique for Deep UV Excimer Laser Based Lithography
    (SPIE, 1995-02-01) Bor, Zsolt; Cavallaro, Joseph R.; Erdelyi, Miklos; Kido, Motoi; Sengupta, Chaitali; Smayling, Michael; Szabo, Gabor; Tittel, Frank; Wilson, William; Center for Multimedia Communication
    This paper reports simulation and experimental details of a novel phase shifting technique based o laser interferometry. Phase shifting is one of the most promising techniques for the fabrication of high density DRAM's. In recent years many kinds of phase shifting methods have been proposed to extend the resolution limit and contrast of image patterns. These techniques however, have several problems that result from the phase shift elements on the mask, especially when applied to UV excimer laser illumination. A new technique will be described that is based on a one-layered reticle which is used as both a reflective and transmissive mask, irradiated from both the front and the back sides. A combination of both off-axis illumination, as well as phase shift are used in this method. Both the relative path length of the two beams as well as their amplitude can be manipulated in such a way that near 100% contrast can be achieved in the final image. Experimental as well as simulation data are used to demonstrate this new method.
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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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    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.