Optics: measuring and testing – Inspection of flaws or impurities – Surface condition
Reexamination Certificate
2001-04-18
2003-05-13
Stafira, Michael P. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Surface condition
C356S237100, C356S237400, C356S237500
Reexamination Certificate
active
06563577
ABSTRACT:
This application claims the benefit of Japanese Applications Nos. 2000-120450 and 2000-153461 which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a defect testing apparatus for detecting a defect such as a foreign substance or a flaw on the surface of a substrate which may be produced in the course of manufacture of a semiconductor device, or the like, especially in the course of manufacture of a semiconductor wafer, a liquid crystal display panel, etc.
2. Related Background Art
In a conventional testing apparatus, a scattered light from the surface of a substrate to be tested is observed to detect an abnormality such as a foreign substance (e.g. dust) or a flaw. For instance, there is an apparatus which is disclosed in the Japanese Patent Laid-Open Application Nos. 5-232032 and 5-232040. According to the disclosed method therein, this apparatus is arranged such that a light from a light source is applied onto an object to be tested, such as a wafer, so as to visually detect the scattered light therefrom, thereby conducting a defect test.
Also, according to a method disclosed in the Japanese Patent Laid-Open Application Nos. 7-27709 and 8-75661, it is arranged that a light from the light source is applied onto a tested object such as a wafer, and the scattered light therefrom is fetched by a light receiving optical system to obtain a dark field image, thereby detecting a defect from this image by an image processing.
To be described more specifically, in the course of manufacturing a semiconductor wafer or a liquid crystal display substrate, presence of a foreign substance such as a dust is a hindrance to a processing for forming a correct circuit pattern, such as an etching or CVD (Chemical Vapor Deposition). Accordingly, it is generally conducted, on the stage of printing and developing a pattern on a resist typically by means of an exposure machine, to test to detect an abnormality or a foreign substance on the printed pattern. Such a conventional test of this type is conducted by applying a light flux from an illumination optical system onto an object to be tested to be visually observed by a testing personnel, as disclosed in the Japanese Patent Laid-Open Application No. 5-232032 described above. In this case, if the light is applied onto a fine circuit pattern in the course of detection of a foreign substance, a diffracted light is produced, which results in difficulty in discriminating the scattered light which is produced by the foreign substance from the diffracted light which is produced by the circuit pattern. Moreover, since a pattern abnormality is detected by using a diffracted light, a result of the test is easily affected by the degree of skill or of fatigue of the testing personnel so that the test standard is unstable. Accordingly, in the above Japanese Patent Laid-Open Application No. 7-27709, such a method is disclosed in which the illumination is optimized in detecting a foreign substance and in detecting a pattern abnormality with application of the technology of an image processing so as to attain a test free from an individual difference of the testing personnel. In this case, in order to detect a foreign substance on the surface of a tested object, an illumination light from the light source is introduced into a light guide fiber to form a linear secondary light source. Then, a light from the linear secondary light source is transmitted through a condensing lens so that a light flux in the direction of the surface on which the illumination light is incident is collimated to be substantially parallel light fluxes. Thereafter, the light is applied onto the entire surface of the wafer at an angle of incidence of substantially 90°. The scattered light from the foreign substance on the wafer is received by the light receiving optical system which is disposed above the wafer, whereby the foreign substance is detected.
However, in such a testing apparatus, if fine repeated patterns are present on the tested object, the diffracted light may enter the eye of the observer or the light receiving optical system to be hindrance to detection of a defect under a certain condition, which leaves the possibility that an abnormality such as a foreign substance of a flaw can not be detected.
Furthermore, the conventional apparatus described above is arranged such that in order to minimize an amount of light to enter the surface of the tested object so as to detect a scattered light from a foreign substance at a highest contrast, the illumination light illuminates the tested object at an angle of incidence of substantially 90°. For this reason, when the wavelength of the illumination light and the pattern pitch of the tested object are substantially equal to each other, the diffracted light advances in a direction substantially perpendicular to the surface of the tested object so as to enter the light receiving optical system. The amount of the diffracted light from the circuit pattern is far greater, compared with that of the scattered light from the foreign substance. For this reason, there arises a problem that the foreign substance can not be detected when the diffracted light is incident on the light receiving optical system of the surface testing apparatus. Particularly, in a case as disclosed in the Japanese Patent Laid-Open Application No. 7-27709, in which the illumination light is applied in the entire circumferential direction of the tested object, since the diffracted light inevitably enters the light receiving optical system, a test on a foreign substance can not be conducted.
SUMMARY OF THE INVENTION
The present invention was contrived taking such problems into consideration, and its object is to provide a testing apparatus and method with high reliability, which is arranged such that a diffracted light does not enter a light receiving optical system and capable of detecting a foreign substance, and the like, correctly at high speed and with high precision.
According to the present invention, there is provided a defect testing apparatus which comprises a light source, an illumination optical system for applying a light flux from the light source onto a substrate to be tested having repeated patterns at a predetermined angle of incidence, a light receiving optical system for receiving a scattered light from the tested substrate, an image pick-up device for picking up an image which is formed by the light receiving optical system, a display device for displaying the image obtained by the image pick-up device, and a test stage for mounting the tested substrate thereon at the time of testing, characterized in that the tested substrate and the illumination optical system are arranged to be rotatable relatively to each other.
The defect testing apparatus of the present invention may be arranged such that the test stage is rotatable around the axis in the normal direction of the tested substrate. Or, an alignment stage may be disposed separately to conduct alignment around the axis in the normal direction of the substrate prior to the test.
Moreover, the defect testing apparatus of the present invention preferably comprises a light receiving optical system which is telecentric on the side of the tested substrate.
Also, the defect testing apparatus of the present invention is preferably arranged, when a light is applied on the tested substrate with the spread angle on a flat surface which is perpendicular to the entrance surface of the illumination optical system and contains the optical axis, to rotate such that an angle of rotation between the optical axis of the illumination optical system and the direction of arrangement of lines of the repeated pattern is more than or equal to ½ of the spread angle.
Moreover, in the defect testing apparatus of the present invention, even when the repeated pattern has two or more directions of arrangement, the test stage or the alignment stage can be rotated to satisfy predetermined conditions.
Furthers the defect testing apparatus of the prese
Komatsu Koichiro
Oomori Takeo
Miles & Stockbridge P.C.
Nguyen Sang H.
Nikon Corporation
Stafira Michael P.
LandOfFree
Defect testing apparatus and defect testing method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Defect testing apparatus and defect testing method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Defect testing apparatus and defect testing method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3093587