US 5,032,734 AGranted

Method and apparatus for nondestructively measuring micro defects in materials

AssigneeVti, L.L.C.

InventorsFred D. Orazio, Jr., Robert B. Sledge, Jr., Robert M. Silva, deceased

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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.

Claims6

Dependent claims

A method of simultaneously measuring the distribution of surface and subsurface micro defects on a predetermined area of a material, comprising the steps of:

(a) generating a beam of electromagnetic radiation with substantially equal S and P polarized components;
(b) directing the beam towards the surface at a predetermined fixed angle of incidence and focusing the beam to expose a small portion of the material to the electromagnetic radiation;
(c) directing the lines of sight of two detectors toward the surface of the material to the point where the beam intercepts the surface, one line of sight and detector for only P polarized electromagnetic radiation and the other line of sight and detector for only S polarized electromagnetic radiation;
(d) limiting the extent of the scattered electromagnetic radiation entering each detector in order to detect the scatter coming from a small solid angle around the line of sight of each detector, for detecting a portion of the scattered electromagnetic radiation and converting it to an electrical signal proportional to the detected intensity from each detector;
(e) producing relative rotation between the beam and the material about an axis substantially perpendicular to the surface and at the point where the beam intercepts the surface and determining the rotational positions of selected scatter signature for that point;
(f) producing relative lateral movement between the beam and the material to expose an adjacent portion of the material to the electromagnetic radiation;
(g) repeating above steps (e) and (f) for each portion of the material exposed until the predetermined area is covered in a contiguous manner;
and
(h) mapping the selected scatter intensity versus the coordinate position of each point of measurement for the predetermined area, the scatter intensity sensed at the P polarization detector being related to the subsurface defects and the scatter intensity sensed at the S polarization detector being related to the surface defects and the rotational positions being related to the defect orientations.

6 more elements

A method of simultaneously measuring the distribution of surface and subsurface micro defects on a predetermined area of a material, comprising the steps of:

(a) generating a beam of electromagnetic radiation with elliptical polarization;
(b) directing the beam towards the surface at a predetermined fixed angle of incidence and focusing the beam to expose a small portion of the material to the electromagnetic radiation;
(c) directing the lines of sight of two detectors toward the surface of the material to the point where the beam intercepts the surface, one line of sight and detector for only P polarized electromagnetic radiation and the other line of sight and detector for only S polarized electromagnetic radiation;
(d) limiting the extent of the scattered electromagnetic radiation entering each detector in order to detect the scatter coming from a small solid angle around the line of sight of each detector, for detecting a portion of the scattered electromagnetic radiation and converting it to an electrical signal proportional to the detected intensity from each detector;
(e) producing relative rotation between the beam and the material about an axis substantially perpendicular to the surface and at the point where the beam intercepts the surface and determining the rotational positions of selected scatter signature for that point;
(f) producing relative lateral movement between the beam and the material to expose an adjacent portion of the material to the electromagnetic radiation;
(g) repeating above steps (e) and (f) for each portion of the material exposed until the predetermined area is covered in a contiguous manner;
and
(h) mapping the selected scatter intensity versus the coordinate position of each point of measurement for the predetermined area, the scatter intensity sensed at the P polarization detector being related to the subsurface defects and the scatter intensity sensed at the S polarization detector being related to the surface defects and the rotational positions being related to the defect orientations.

6 more elements

Apparatus for simultaneously measuring the distribution of surface and subsurface micro defects on a predetermined area of a material, comprising the steps of:

(a) means for generating a beam of electromagnetic radiation with substantially equal S and P polarized components;
(b) means for directing the beam towards the surface at a predetermined fixed angle of incidence and focusing the beam to expose a small portion of the material to the electromagnetic radiation;
(c) means for directing the lines of sight of two detectors toward the surface of the material to the point where the beam intercepts the surface, one line of sight and detector for only P polarized electromagnetic radiation and the other line of sight and detector for only S polarized electromagnetic radiation;
(d) means for limiting the extent of the scattered electromagnetic radiation entering each detector in order to detect the scatter coming from a small solid angle around the line of sight of each detector, for detecting a portion of the scattered electromagnetic radiation and converting it to an electrical signal proportional to the detected intensity from each detector;
(e) means for producing relative rotation between the beam and the material about an axis substantially perpendicular to the surface and at the point where the beam intercepts the surface and determining the rotational positions of selected scatter signature for that point;
(f) means for producing relative lateral movement between the beam and the material to expose an adjacent portion of the material to the electromagnetic radiation;
(g) means for repeatably engaging means (e) and (f) for each portion of the material exposed until the predetermined area is covered in a contiguous manner;
and
(h) mean for mapping the selected scatter intensity versus the coordinate position of each point of measurement for the predetermined area, the scatter intensity sensed at the P polarization detector being related to the subsurface defects and the scatter intensity sensed at the S polarization detector being related to the surface defects and the rotational positions being related to the defect orientations.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/597,857Filed 15 Oct 1990
Granted: 16 Jul 1991
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

G01N 21/21
Systems in which incident light is modified in accordance with the properties of the material investigated: polarisation-affecting properties
G01N 21/9501
Characterised by the material or shape of the object to be examined: semiconductor wafers
G01N 21/33
Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry:…
G01N 21/47
Systems in which incident light is modified in accordance with the properties of the material investigated: scattering, i.e. diffuse reflection

Family

No related US applications are recorded in the indexed filing history.

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