Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
1998-09-28
2001-05-22
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S559450
Reexamination Certificate
active
06236056
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for evaluating a defect or the like on, e.g., a semiconductor wafer. A defect means a defect, a foreign substance, a flaw, a particle, or unevenness.
2. Related Background Art
In a conventional apparatus for evaluating a defect in an object such as a semiconductor wafer, a laser beam is irradiated on the object obliquely with respect to the surface of an object to observe scattered light from a defect inside the object is observed from the object surface side in a direction different from the laser beam incident direction, thereby detecting a defect or a particle in the object (Japanese Patent Application Laid-Open No. 4-24541). In this apparatus, the scattered light is observed in a direction different from the direction of the laser beam reflected by the object, thereby minimizing the influence of reflected light. Also, the wavelength of laser beam or the object temperature can be changed to adjust the depth in the object to which the laser beam travels.
In this apparatus, however, when a defect near the surface of the object is observed, a flaw or the like on the surface is observed together in the same observation field. Since the defect cannot be discriminated from the flaw, accurate evaluation cannot be obtained.
To solve this problem, in a conventional defect evaluation apparatus comprising a laser irradiation means for obliquely irradiating a laser beam onto the observation surface of an object, and an observation means for observing, through the observation surface, scattered light which is generated by a defect or a particle in the object when refracted light of the laser beam becomes incident thereon, a component discrimination means is used to allow observation with both light mainly containing a p-polarized light component and light mainly containing an s-polarized light component. With this apparatus, even when a defect near the surface of the object surface is to be observed, and a flaw or the like on the surface is present in the same observation field, the defect can be discriminated from the flaw, so accurate evaluation can be obtained.
However, the shape information of the defect cannot be obtained.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a defect evaluation apparatus capable of separating defects or the like of an object into defects in the object and those on the object surface, and simultaneously obtaining the shape information of the defect.
In order to achieve the above object, according to the present invention, there is provided a defect evaluation apparatus comprising laser irradiation means for obliquely irradiating a laser beam onto an object, and observation means for observing scattered light from inside the object or a surface of the object, wherein the laser irradiation means irradiates the laser beam onto the object from a plurality of incident directions around an observation optical axis, and the observation means receives the scattered light from the object to obtain shape information of a defect or the like in the object or on the surface of the object.
REFERENCES:
patent: 4614427 (1986-09-01), Koizumi et al.
patent: 4893932 (1990-01-01), Knollenberg
patent: 4966457 (1990-10-01), Hayano et al.
patent: 5032734 (1991-07-01), Orazio, Jr. et al.
patent: 5424536 (1995-06-01), Moriya
patent: 5426506 (1995-06-01), Ellingson et al.
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Le Que T.
Mitsui Mining & Smelting Co. Ltd.
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