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United States Patent m
Silva, deceased et al.
[li] Patent Number: 4,933,567  Date of Patent: Jun. 12, 1990
 METHOD AND APPARATUS FOR NONDESTRUCTIVELY MEASURING SUBSURFACE DEFECTS IN MATERIALS
 Inventors: Robert M. Silva, deceased, late of Dayton, by Ruby M. Silva, executrix; Fred D. Orazio, Jr., Centerville; Robert B. Sledge, Jr., Dayton, all of Ohio
 Assignee: VTI, Inc., Dayton, Ohio
 Appl. No.: 301,721
 Filed: Jan. 26, 1989
Related U.S. Application Data
 Continuation-in-part of Ser. No. 218,542, Jul. 13, 1988, abandoned, which is a continuation-in-part of Ser. No. 918,518, Oct. 14,1986, abandoned, which is a continuation-in-part of Ser. No. 724,966, Apr. 19, 1985, abandoned.
 Int. CI.5 G01N 21/01
 U.S. a 250/572; 356/369;
 Field of Search 250/562, 563, 572, 225;
356/338, 340, 341, 369, 370, 429-431, 445-449
 References Cited
U.S. PATENT DOCUMENTS
3,574,470 4/1971 Vukelich et al 250/572
3,652,863 3/1972 Gaskell et al 356/239
3,904,293 9/1975 Gee 356/448
4,015,127 3/1977 Sharkins 356/369
4,314,763 2/1982 Steigmeier et al 356/237
4,342,515'- 8/1982 Akiba et al 356/239
4.352.016 9/1982 Duffy et al 250/358.1
4.352.017 9/1982 Duffy et al 250/358.1
4,391,524 7/1983 Steigmeier et al 356/338
4,395,122 7/1983 Southgate et al 250/572
4,575,249 3/1986 Grieger 356/446
F. D. Orazio, Jr., W. K. Stowell and R. M. Silva, Instrumentation of a Variable Angle Scatterometer (VAS), Aug. 1982.
W. K. Stowell, R. M. Silva and F. D. Orazio, Jr., Damage Susceptibility of Ring Laser Gyro Class Optics, Aug. 1982.
R. M. Silva, F. D. Orazio, Jr. and W. K. Stowell, Scatter Evaluation of Supersmooth Surfaces, Aug. 1982. IBM Technical Disclosure Bulletin, vol. 20, No. 8, Jan. 1978, Automatic Brewster's Angle Thin Film Thickness Measurement Spectrophotometer, Chwalow et al.
Primary Examiner—David C. Nelms
Assistant Examiner—Stephone B. Allen
Attorney, Agent, or Firm—Jacox & Meckstroth
A method and apparatus are disclosed for nondestructive^ measuring the density and orientation of crystalline and other micro defects directly below the surface of a properly prepared material such as a semiconductor wafer. The material surface is illuminated with a probe beam of electromagnetic radiation which is limited to a nondestructive power level and with a wavelength, or wavelengths, selected according to certain characteristics of the material so that penetration depth is controlled. Specific orientation of the material with respect to the probe beam and the detector is required to detect that portion of the probe beam scattered from the subsurface region without interference from the surface scatter and to identify the orientation of the defects. Maps of scatter intensity versus position are made according to the density of the defects in the subsurface.
21 Claims, 7 Drawing Sheets