Optical defect inspection apparatus

Abstract

A laser beam oscillated from a laser source is folded in its path by first and second plane mirrors and enters a beam expander. The surface of each plane mirror is deteriorated with illumination by the laser beam and the reflectance is reduced. To avoid a light quantity of the laser beam entering the beam expander from being reduced below a reference value, when the laser beam is illuminated over a certain time, a position on each of the first and second plane mirrors at which the laser beam is illuminated is changed by a structure for rotating and / or translating a reflecting surface of each plane mirror on a plane, which includes the plane mirror, while an optical axis is kept same. The useful life of each plane mirror can be prolonged without displacing the optical axis itself by overcoming the problem that when the laser beam is employed as the light source and a thin beam with a high illumination density is illuminated to the same position on each of the first and second plane mirrors for a long time, the surface of the plane mirror is deteriorated, the reflectance is reduced, and the light quantity cannot be held at a required level.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an apparatus and a method for inspecting an object to be inspected (i.e., an inspection target). More particularly, the present invention is adapted for an optical defect inspection apparatus and method for inspecting foreign matters, defects, etc. on inspected objects in manufacturing processes of, e.g., semiconductor devices, flat panel displays, magnetic disks, and masks. [0003] 2. Description of the Related Art [0004] The capability of detecting finer defects is demanded in an optical defect inspection apparatus for illuminating a light to an object to be inspected, such as a semiconductor device and a flat panel display, and measuring the light reflected or scattered from the object. To meet such a demand, using a light source with higher luminance is required and a laser beam is mainly used as the light source. One known inspection apparatus using the laser beam is disclosed in...

AI Technical Summary

Benefits of technology

[0009] An object of the present invention is to prolong the useful life of a plane mirror (each of first and second plane mirrors) without displacing an optical axis itself, taking into account the above-described problem that when a laser beam is employed as the light source and a thin beam with a high illumination density is illuminated to the same position on each of the first and second plane mirrors for a long time, the surface of the plane mirror is deteriorated, the reflectance is reduced, and the light quantity cannot be held at a required level.

[0012] In order to avoid the above problem, a dust collection chamber 803C for collecting the pressurized air including generated dust is required to be disposed around the piston rod 805 and the seal ring 807. The provision of the dust collection chamber 803C significantly limits layout of a vacuum source 821 and a line 819, which are also arranged nearby for evacuation. There is hence a demand for a linearly reciprocating device which can suppress the generation of dust without needing the vacuum source and the line for evacuation.

[0016] To overcome the above problems and to achieve the above object, the present invention is featured in providing one or more mechanisms capable of moving a beam illuminated position on each of a first reflecting mirror and a second reflecting mirror, which reflect an illuminated laser beam, and changing a position of reflection on the reflecting mirror with one or both of rotation and translation of the reflecting mirror on a reflecting including the reflecting mirror while an optical axis itself is kept same, thereby allowing the use of a position on the reflecting mirror where the reflectance is not reduced. Also, those mechanisms can be realized with a manual, automatic or programmed way based on the illumination intensity measured before and behind the reflecting mirror.

[0030] Still another feature of the present invention resides in that, in any of the above-described defect inspection apparatuses, the inspected object is supported at an outer peripheral edge thereof by the inspected object holding unit, thereby enabling the inspected object to be inspected while a rear surface of the inspected object is kept in a non-contact state.

[0033] According to the one feature of the present invention, since the reflecting mirror is provided with the translation mechanism and the rotation mechanism both causing no displacements of the optical axis, frequency of part replacement can be reduced and alignment of the optical axis of the reflecting mirror can be dispensed with.

Problems solved by technology

However, replacing the plane mirror whenever its reflection is reduced causes a problem in point of cost efficiency.

Also, changing the laser illuminated point on the plane mirror to avoid frequent replacement is not easy to practice in the known apparatus.

The generation of dust causes deposition of foreign matters on the inspected object during transport and inspection thereof, and deteriorates reproducibility of the inspection apparatus.

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