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Ultra-Shallow P+/N Junctions Formed by SiF4 Preamorphization and BF3 Implantation Using plasma Immersion Ion Implantation

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MRS Online Proceedings Library 1992年第1期279卷 255-259页

作者： Erin C. Jones Seongil Im Nathan W. Cheung Plasma Assisted Materials Processing Laboratory Department of Electrical Engineering and Computer Sciences University of California Berkeley USA Department of Materials Science and Mineral Engineering University of California Berkeley USA

Sub-100 nm P+/N junctions are fabricated by implanting wafers in the plasma immersion ion implantation system (PIII). Ions from SiF4 and BF3 plasmas are implanted at energies from 4-6 keV and 2 keV, respectively. The amorphous region formed by SiF4 im-plantion is shown to be effective in slowing B diffusion during a 10 sec, 1060°C rapid thermal anneal step. Channeling and transmission electron microscopy studies show the recrys-tallized amorphous region is comparable in quality to an unprocessed Si wafer, and the implantation and annealing sequence has no detrimental effects on the physical or electrical characteristics of fabricated devices. Diodes have forward ideality factors of 1.05 to 1.06 and reverse leakage as low as 2 nA/cm2 in the diode bulk at -5 V applied bias.

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Limit cycles in floating-point implementations of recursive filters-a review

Limit cycles in floating-point implementations of recursive ...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： T.I. Laakso B. Zeng Laboratory of Signal Processing and Computer Technology Helsinki University of Technology Espoo Finland Department of Electrical Engineering University of Toronto Toronto ONT Canada

Results on limit cycle oscillations in floating-point implementations of recursive filters are reviewed. Special attention is paid to structures with a single floating-point nonlinearity in the recursive filter loop, for which efficient criteria are proposed to guarantee the absence of limit cycles. Both unlimited exponent range limit cycles and underflow limit cycles are considered. Also results on wave digital filters and related structures are discussed.< >

关键词： Limit-cycles Quantization Laboratories Signal processing Digital filters Feedback loop Information analysis Information filtering Information filters Hardware

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Proximity effect reduction in x‐ray mask making using thin silicon dioxide layers

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1992年第6期10卷 3062-3066页

作者： Kee W. Rhee David I Ma Martin C. Peckerar R. A. Ghanbari Henry I. Smith Nanoelectronics Processing Facility Naval Research Laboratory Washington DC 20375 Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139

A novel method is reported for reducing the proximity effect in high‐resolution electron beam patterning of high atomic number materials such as tungsten. The method involves interposing a thin (50–400 nm) layer of SiO2 between the resist and the underlying high‐Z substrate. Examples are shown in which gratings of 0.2 μm lines with a 0.5 μm period were written without proximity effect compensation. Optimal intermediate layer thickness for the best resolution of the gratings is determined to be 200 nm. A Monte Carlo model of electron scattering including inelastic processes has been implemented to interpret our experimental results. The model presented shows that having the low atomic number SiO2 layer between the resist and the tungsten prevents the fast secondary electrons being generated at the surface of the tungsten from propagating back into the resist, suggesting a mechanism for proximity effect reduction. The results presented here have important practical applications for x‐ray mask making.

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Multiple branch FIR filters for sampling rate conversion

Multiple branch FIR filters for sampling rate conversion

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： T. Saramaki S.K. Mitra Signal Processing Laboratory Tampere University of Technology Tampere Finland Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

A class of linear-phase finite impulse response (FIR) digital filters for sampling rate conversion is introduced. These filters consist of two cascaded parts. The first part is a parallel connection of two or three branches with transfer function of the form A/sub k/(z)B/sub k/) (z/sup D/), where D is the sampling rate conversion ratio. The second part has a transfer function of the form C(z/sup D/). The advantage of these designs is that they provide a significant reduction in the multiplication and addition rates as well as in the number of required multipliers over the equivalent conventional direct-form designs also in cases where D is a prime number. In these cases, the sampling rate conversion cannot be performed in several stages and many of the other existing designs lose their advantages. Special multiplier-free solutions are generated for implementing the filters A/sub k/(z), resulting in dramatic savings. Several examples are included showing the efficiency of the proposed filters compared to other existing designs.< >

关键词： Finite impulse response filter Sampling methods Delay Passband Niobium USA Councils Baseband Shape Transfer functions Interpolation

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Comparative mobility degradation in modulation‐doped GaAs devices after e‐beam and x‐ray irradiation

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1992年第6期10卷 2890-2892页

作者： R. A. Ghanbari M. Burkhardt D. A. Antoniadis Henry I. Smith M. R. Melloch K. W. Rhee M. C. Peckerar Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 School of Electrical Engineering Purdue University West Lafayette Indiana 47907 Nanoelectronics Processing Facility U. S. Naval Research Laboratory Washington DC 20375

We report on measured Hall mobility versus temperature for high‐quality modulation‐doped AlGaAs/GaAs samples after exposure by electrons and x rays at doses and energies typically used in lithography. We find that bare samples exposed by 50 keV electrons suffered significant mobility degradation over the temperature range of 4.2–300 K (as much as a factor of 30). X‐ray‐exposed samples did not show any mobility degradation. Two‐dimensional electron densities were not dramatically affected by either exposure technique, although e‐beam exposed samples did show a slight decrease in carrier density. Our results are consistent with previous reports of mobility degradation in some e‐beam evaporators.

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Conductance quantization in a GaAs electron waveguide device fabricated by x‐ray lithography

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1992年第6期10卷 2966-2969页

作者： W. Chu C. C. Eugster A. Moel E. E. Moon J. A. del Alamo Henry I. Smith M. L. Schattenburg K. W. Rhee M. C. Peckerar M. R. Melloch Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 Center for Space Research Massachusetts Institute of Technology Cambridge Massachusetts 02139 Nanoelectronics Processing Facility U.S. Naval Research Laboratory Washington DC 20375 School of Electrical Engineering Purdue University West Lafayette Indiana 47907

We report on the fabrication of AlGaAs/GaAs split‐gate electron waveguide devices of lengths between 0.1 and 2 μm using x‐ray lithography, and the measurements of these devices at liquid‐helium temperatures and up to 15 K. An x‐ray mask (parent mask) was fabricated using e‐beam lithography and replicated using proximity x‐ray lithography (λ=1.32 nm) to generate a replica (daughter) mask. The daughter mask was then aligned to patterns on a high‐mobility AlGaAs/GaAs sample and x ray exposed using a conformable mask fixture. The conductance of the electron waveguides was measured as a function of the split‐gate bias. Sharp 2e2/h conductance steps were observed in devices up to 0.75 μm long at T=2 K. The features in the conductance remain visible up to 15 K.

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Fabrication of parallel quasi‐one‐dimensional wires using a novel conformable x‐ray mask technology

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1992年第6期10卷 3196-3199页

作者： R. A. Ghanbari W. Chu E. E. Moon M. Burkhardt K. Yee D. A. Antoniadis Henry I. Smith M. L. Schattenburg K. W. Rhee R. Bass M. C. Peckerar M. R. Melloch Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 Center for Space Research Massachusetts Institute of Technology Cambridge Massachusetts 02139 Nanoelectronics Processing Facility U. S. Naval Research Laboratory Washington DC 20375 School of Electrical Engineering Purdue University West Lafayette Indiana 47907

We report on the fabrication of quasi‐one‐dimensional wires on modulation‐doped GaAs/AlGaAs using a novel conformable x‐ray mask technology which allows us to expose arbitrary sized samples, including samples much smaller than the membrane area, using our laboratory’s standard 31 mm‐diam silicon‐nitride x‐ray mask. After optical alignment, the sample and mask are brought into contact electrically, and then loaded into a specially designed cartridge which allows a vacuum to be pulled between mask and substrate. The vacuum causes the x‐ray mask to conform around the sample. We find that a vacuum hold down is necessary to allow easy separation of the sample from the mask with minimal risk to both.

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Holographic moiré patterns processed by the fourier transform method

Holographic moiré patterns processed by the fourier transfo...

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Holographics International 1992

作者： Simova, Eli S. Stoev, Krassimir N. Central Laboratory of Optical Storage and Processing of Information Bulgarian Academy of Sciences P.O. Box 95 Sofia1113 Bulgaria Institute of Nuclear Energy and Nuclear Research Bulgarian Academy of Sciences Boul. Trakia 72 Sofia1784 Bulgaria Electrical Engineering Department University of Ottawa 161 Louis Pasteur OttawaONKIN 6N5 Canada River Road Environmental Technology Center 3439 River Road GloucesterONK1 A 0H3 Canada

Spatial-carrier fringe pattern analysis is a wide-spread technique and has found a lot of applications to optical metrology. Introducing spatial-carrier into a holographic moire pattern is also a well-known technique to obtain observable moire fringes. Preprocessing of the holographic moire pattern includes optical or digital Fourier filtering to remove the carrier. The fringe pattern is then processed by using time-consuming fringe-counting algorithms. The current work presents a new appUcation of the Fourier transform method to automated analysis of holographic moire fringe patterns. The method owns the advantage of instantaneous determination of both phase functions in the pattern. Investigations are carried out on the frequency restrictions imposed on the phase functions. The technique is demonstrated on computer generated noisy holographic moire patterns. The technique does not compUcate the conventional experimental holographic moire arrangement. © 1992 SPIE. All rights reserved.

关键词： Moire fringes

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IMAGE SEQUENCE CODING BY SPLIT AND MERGE

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IEEE TRANSACTIONS ON COMMUNICATIONS 1991年第12期39卷 1845-1855页

作者： WILLEMIN, P REED, TR KUNT, M Signal and Image Processing Laboratory Swiss Federal Institute of Technology Lausanne Switzerland Department of Electrical Engineering and Computer Science University of California Davis CA USA

This paper describes a method for reducing the information contained in an image sequence, while retaining the information necessary for the interpretation of the sequence by a human observer. The method consists of first locating the redundant information, reducing the degree of redundancy, and coding the result. The sequence is treated as a single 3-D data volume, the voxels of which are grouped into several regions, obtained by a 3-D split and merge algorithm. To find these regions, we first obtain an initial region space by splitting the image sequence until the gray-level variation over each region can be approximated by a 3-D polynomial, to a specified accuracy. This results in a set of parallelepipedic regions of various sizes. To represent the gray-level variation over these regions, the coefficients of the approximating polynomial are used as features. The most similar regions are then merged, using a region adjacency graph. The information is coded by representing the borders of the regions using a pyramidal structure in the x, y, t space. The coefficients of the approximating polynomials are coded in a straightforward manner. For 256 x 256 pixel, 25 frames/s image sequences, compressions allowing transmission rates near 64 kbit/s are obtained.

关键词： Image sequences Image coding Pixel Bandwidth Layout Polynomials Image segmentation Humans Helium ISDN

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Axial radio frequency electric field intensity and ion density during low to high mode transition in argon electron cyclotron resonance discharges

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1991年第2期9卷 339-347页

作者： D. A. Carl M. C. Williamson M. A. Lieberman A. J. Lichtenberg Department of Chemical Engineering Plasma Assisted Materials Processing Laboratory Univerity of California Berkeley California 94720 Department of Electrical Engineering and Computer Sciences Plasma Assited Materials Processing Laboratory University of California Berkeley California 94720

To investigate the transition from the low density mode to the high density mode in an electron cyclotron resonance (ECR) discharge, a Langmuir probe and an E field probe were used to measure ion density and E field intensity as functions of axial position and power. The experiments were performed in argon at 0.13 Pa in a 7.9 cm diam cyclindrical source chamber propagating TE11 mode 2.45 GHz microwave power. Low mode was characterized by a standing wave throughout the plasma chamber and minimal power absorption. High mode exhibited nearly complete power absorption and no standing wave past the ECR zone. A sliding short (ss) was used to determine if the position of an E field null in the source chamber affected the transition between these two modes for various magnetic field configurations. The ss position had little effect on mode transition, relative power absorption or ion density when positioned downstream from a broad, large volume resonance zone (resonance near the mirror midplane). However, the plasma could not be ignited if the short was placed at or upstream from the large volume resonance *** the magnetic field was adjusted to yield a sharp, small volume resonance zone (resonance midway between the midplane and the throat), then positioning the ss to force an E field null at the resonance zone would prevent plasma ignition, even at 800 W forward power. The ion density exhibited a hysteresis (i.e., a direct jump from no plasma to a plasma density observed at other sliding short positions for that same forward power, thereafter following the ion density versus forward power dependence observed at nearby ss positions) on power cycling when the sliding short was within ∼1 cm of the broad resonance zone or within ∼1 cm of forcing a null in the sharp resonance zone caes. The ion density versus power curve for the broad volume case exhibited a change in slope over the transition region (Pforward ≊40 W) when the ion density at the resonance zone was ≊1×1011 cm

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