Hierarchical control system for molecular beam epitaxy

United States Patent m

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US005461559A [ii] Patent Number: 5,461,559 [45] Date of Patent: Oct. 24, 1995

[54] HIERARCHICAL CONTROL SYSTEM FOR MOLECULAR BEAM EPITAXY

[75] Inventors: Jeffrey J. Heyob; Oliver D. Patterson, both of Beavercreek; Steven R. LeClair, Spring Valley; T. Walter Haas, Kettering, all of Ohio; Kenneth Currie, Cookeville, Term.; Doug Moore, Okeana, Ohio; Stephen J. Adams, Dayton, Ohio; Victor Hunt, Cincinnati, Ohio

[73] Assignee: The United States of America as

represented by the Secretary of the
Air Force, Washington, D.C.

[21] Appl. No.: 131,536
[22] Filed: Oct. 4, 1993

[51] Int. CI.6 G05B 13/04

[52] U.S. CI 364/149; 364/468; 395/904;

117/85; 505/473

[58] Field of Search 364/149, 148,

364/468, 488^91; 156/601; 437/81, 122; 395/902, 904, 903, 906, 912; 117/85, 86, 202; 437/105; 505/473; 118/725; 427/564

[56] References Cited

U.S. PATENT DOCUMENTS

5,096,533 3/1992 Igarashi 156/601

5,122,222 6/1992 Turner et al 117/86

5,143,896 9/1992 Harada et al 505/473

5,169,798 12/1992 Eaglesham et al 437/81

5,185,288 2/1993 Cooketal 437/122

5,205,900 4/1993 Inoue et al 156/601

5,227,363 7/1993 Furukawa et al 505/473

5,364,492 11/1994 Eckstein et al 117/105

OTHER PUBLICATIONS

Currie, K. R. LeClair, S. R. and Pattevon, O. D., "Self-Improving Process Control for Molecular Beam Epitaxy", International Journal of Advanced Manufacturing Technology no date.

Chilton, P. A., Trascott, W. S., Wen, V. F. "Elimination of the Flux Transients from Molecular-Beam Epitaxy Source Cells

following Shutter Operation", Journal of Vacuum Science and Technology, B6 (4), Jul./Aug. 1988 pp. 1099-1103. Vlcek, J. C. Fonstad, C. G. "Precise Computer Control of the MBE Process", Journal of Crystal Growth, vol. HI 1991 pp. 55-60.

Patterson, O. D., Qualitative Control of Molecular Beam Epitaxy, Self Directed Control Workshop, WRDC-TR-90-4123 May 1990.

Heyob, Jeffrey J., "The Process Discovery Autotuner", 1991, pp. 1-114.

Adams, Stephen J., "Implementation Of A Robust Algorithm
For Comp. Of Shutter Opening Induced Flux Transients For
The Molecular Beam Epitaxy Process":, 1993, pp. 1-78.
Patterson O. D., Adams S. J., Garrett P. R, Eyink K. G.,
LeClair S. R., Heyob J. J., Hunt V, Currie K. R., Haas T. W,
"Progress Toward A Compre. Control Sys. For Molecular
Beam Epataxy", Aug. 1992, pp. 1-20.
Heyob J. J., "Insitu Process Control Research", 1992, pp.
1-60.

Primary Examiner—James P. Trammell

Attorney, Agent, or Firm—Bernard E. Franz; Thomas L.

Kundert

A multi-featured control system which improves the manufacturing capability of the thin-film semiconductor growth process. This system improves repeatability and accuracy of the process, reduces the manpower requirements to operate MBE, and improves the MBE environment for scientific investigation. This system has three levels of feedback control. The first level improves the precision and tracking of the process variables, flux, and substrate temperature. The second level comprises an expert system that uses sensors to monitor the status of the product in order to tailor the process plan in real time so that the exact qualities desired are achieved. The third level features a continuously evolving neural network model of the process which is used to recommend the recipe and command inputs to achieve a desired goal. The third level is particularly useful during the development process for new materials. All three levels require models of the process which are updated during automatic process identification experiments.

18 Claims, 39 Drawing Sheets

Microfiche Appendix Included
(101 pages 2 Microfiche)

The Three Loops of the MBE Control System

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