[54] METHOD AND APPARATUS FOR
MEASURING THICKNESS OF EPITAXIAL
LAYER BY INFRARED REFLECTANCE
[75] Inventors: William R. Case, Walden, N.Y.;
Wildey E. Johnson, Boca Raton, Fla.
[73] Assignee: International Business Machines Corporation, Armonk, N.Y.
[21] Appl. No.: 442,193
[22] PCT Filed: May 27, 1982
[86] PCT No.: PCT/US82/00729
§ 371 Date: Oct. 28, 1982
§ 102(e) Date: Oct. 28, 1982
[51] Int. CI.4 G01B 11/02
[52] U.S. CI 364/563; 356/357;
356/381
[58] Field of Search 364/563, 728; 356/355,
356/357, 381, 382; 156/601; 148/175
[56] References Cited
U.S. PATENT DOCUMENTS
3,816,722 6/1974 Sakoe et al 364/728
3,819,274 6/1974 Koulicovitch et al 356/357
3,892,490 7/1975 Uetsuki et al 356/382 X
3,994,599 11/1976 Southwell 356/357
4,032,885 6/1977 Roth 364/728
4,203,799 5/1980 Sugawara et al 356/357 X
4,293,224 10/1981 Gaston et al 356/357
4,355,903 10/1982 Sandercock 356/382
OTHER PUBLICATIONS
IBM Technical Disclosure Bulletin, Jun. 1981 (vol. 24, No. 1A), W. R. Case; "Transparent Film Thickness Measurement", pp. 49-54.
IBM Technical Disclosure Bulletin, Jun. 1982 (vol. 25, No. 1), G. H. Hewig; "In-Situ, Realtime Thin-Film Refractive Index & Thickness Monitor", pp. 436-438. IBM Technical Disclosure Bulletin, Aug. 1976 (vol. 19, No. 3), R. B. Ananthakrishan, "Cubic Spline Fit for
Calibration of Thin Film Measurement Tools", pp. 890-896.
Applied Optics, Sep. 1978 (vol. 17, No. 17), A. M. Goodman; "Optical Interference Method for Approximate Determination of Refractive Index and Thickness of a Transparent Layer", pp. 2779-2787. IBM Technical Disclosure Bulletin, Apr. 1976 (vol. 18, No. 11), R. B. Ananthakrishnan; "Algorithm for Computing Thin-Film Thicknesses", pp. 3618-3819. J. Electrochem. Soc, Feb. 1973 (vol. 120, No. 2), P. F. Cox et al.; "Measurement of Si Epitaxial Thickness Using a Michelson Interferometer", pp. 287-292. J. App. Phy., Jul. 1970 (vol. 41, No. 8), P. A. Schumann et al., "Measurement of Silicon Epitaxial Layers Less than 1/j, Thick by Infrared Interference", pp. 3532-3535.
"Optical Properties of Thin Solid Films"; O. S. Heavens, Phd, published by Butterworths Scientific Publications, 1955, pp. 76 and 77.
Primary Examiner—Errol A. Krass
Assistant Examiner—Kevin J. Teska
Attorney, Agent, or Firm—Douglas R. McKechnie
[57] ABSTRACT
Method and apparatus measure the thickness of an epi layer grown on a substrate. IR energy 12 is directed onto the epi layer 13 and a portion 14 of the energy is reflected from the surface of the epi layer and from the interface of the epi layer and substrate. The spectral reflectance of the reflected energy is measured by means of a Fourier transform IR spectrometer 10. The measured values of spectral reflectance are correlated with a series of theoretical reflectance values determined for different thicknesses of an epi layer in a range including the nominal thickness. The measured or actual epi thickness is determined from the correlation analysis.
14 Claims, 7 Drawing Figures
