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Title: Closed loop adaptive control of spectrum-producing step using neural networks

Abstract

Characteristics of the plasma in a plasma-based manufacturing process step are monitored directly and in real time by observing the spectrum which it produces. An artificial neural network analyzes the plasma spectrum and generates control signals to control one or more of the process input parameters in response to any deviation of the spectrum beyond a narrow range. In an embodiment, a plasma reaction chamber forms a plasma in response to input parameters such as gas flow, pressure and power. The chamber includes a window through which the electromagnetic spectrum produced by a plasma in the chamber, just above the subject surface, may be viewed. The spectrum is conducted to an optical spectrometer which measures the intensity of the incoming optical spectrum at different wavelengths. The output of optical spectrometer is provided to an analyzer which produces a plurality of error signals, each indicating whether a respective one of the input parameters to the chamber is to be increased or decreased. The microcontroller provides signals to control respective controls, but these lines are intercepted and first added to the error signals, before being provided to the controls for the chamber. The analyzer can include a neural network and an optionalmore » spectrum preprocessor to reduce background noise, as well as a comparator which compares the parameter values predicted by the neural network with a set of desired values provided by the microcontroller.« less

Inventors:
 [1]
  1. (San Francisco, CA)
Issue Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
OSTI Identifier:
872003
Patent Number(s):
5841651
Assignee:
United States of America as represented by United States (Washington, DC) LLNL
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
closed; loop; adaptive; control; spectrum-producing; step; neural; networks; characteristics; plasma; plasma-based; manufacturing; process; monitored; directly; time; observing; spectrum; produces; artificial; network; analyzes; generates; signals; input; parameters; response; deviation; narrow; range; embodiment; reaction; chamber; forms; gas; flow; pressure; power; window; electromagnetic; produced; subject; surface; viewed; conducted; optical; spectrometer; measures; intensity; incoming; wavelengths; output; provided; analyzer; plurality; error; indicating; respective; increased; decreased; microcontroller; provides; controls; lines; intercepted; added; optional; preprocessor; reduce; background; noise; comparator; compares; parameter; values; predicted; set; desired; optical spectrometer; artificial neural; plasma reaction; manufacturing process; closed loop; control signal; neural network; gas flow; reaction chamber; control signals; error signal; neural networks; background noise; optical spectrum; adaptive control; parameter values; narrow range; error signals; electromagnetic spectrum; process step; controller provides; desired value; desired values; neural net; /700/216/438/

Citation Formats

Fu, Chi Yung. Closed loop adaptive control of spectrum-producing step using neural networks. United States: N. p., 1998. Web.
Fu, Chi Yung. Closed loop adaptive control of spectrum-producing step using neural networks. United States.
Fu, Chi Yung. Thu . "Closed loop adaptive control of spectrum-producing step using neural networks". United States. https://www.osti.gov/servlets/purl/872003.
@article{osti_872003,
title = {Closed loop adaptive control of spectrum-producing step using neural networks},
author = {Fu, Chi Yung},
abstractNote = {Characteristics of the plasma in a plasma-based manufacturing process step are monitored directly and in real time by observing the spectrum which it produces. An artificial neural network analyzes the plasma spectrum and generates control signals to control one or more of the process input parameters in response to any deviation of the spectrum beyond a narrow range. In an embodiment, a plasma reaction chamber forms a plasma in response to input parameters such as gas flow, pressure and power. The chamber includes a window through which the electromagnetic spectrum produced by a plasma in the chamber, just above the subject surface, may be viewed. The spectrum is conducted to an optical spectrometer which measures the intensity of the incoming optical spectrum at different wavelengths. The output of optical spectrometer is provided to an analyzer which produces a plurality of error signals, each indicating whether a respective one of the input parameters to the chamber is to be increased or decreased. The microcontroller provides signals to control respective controls, but these lines are intercepted and first added to the error signals, before being provided to the controls for the chamber. The analyzer can include a neural network and an optional spectrum preprocessor to reduce background noise, as well as a comparator which compares the parameter values predicted by the neural network with a set of desired values provided by the microcontroller.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1998},
month = {1}
}

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