Abstract: A method and apparatus are disclosed for nondestructively measuring the density and orientation of crystalline and other micro defects on and 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 or levels. Polarization and wavelength or wavelengths of the electromagnetic radiation are 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 defects of interest, surface or subsurface, without interference from other scatter sources and to identify the orientation of the defects. Maps of scatter intensity versus position are made according to the density of the defects encountered.
Type:
Grant
Filed:
October 15, 1990
Date of Patent:
July 16, 1991
Assignee:
VTI, Inc.
Inventors:
Fred D. Orazio, Jr., Robert B. Sledge, Jr., Robert M. Silva, deceased
Abstract: A method and apparatus are disclosed for nondestructively measuring the density and orientation of crystalline and other micro defects on and 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 or levels. Polarization and wavelength or wavelengths of the electromagnetic radiation are 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 defects of interest, surface or subsurface, without interference from other scatter sources and to identify the orientation of the defects. Maps of scatter intensity versus position are made according to the density of the defects encountered.
Type:
Grant
Filed:
November 16, 1989
Date of Patent:
December 18, 1990
Assignee:
VTI, Inc.
Inventors:
Robert M. Silva, deceased, Fred D. Orazio, Jr., Robert B. Sledge, Jr.
Abstract: A method and apparatus are disclosed for nondestructively 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.
Type:
Grant
Filed:
January 26, 1989
Date of Patent:
June 12, 1990
Assignee:
VTI, Inc.
Inventors:
Robert M. Silva, deceased, Fred D. Orazio, Jr., Robert B. Sledge, Jr.
Abstract: In glass bodied gas lasers which use helium as a constituent gas, the leakage of helium through the laser walls is controlled by a specially applied external sealed metal coating. The glass body of the laser is then used as a solid state helium reservoir. In addition, in all lasers with thermal problems, such as distortion and the like, this same specially applied metal coating serves to distribute the temperature evenly over the laser minimizing those thermal distortions.