JP2008045964A - Edge inspection apparatus and exposure apparatus - Google Patents

Abstract

An end inspection apparatus capable of imaging the front, back, and side surfaces of an end by a set of optical systems.
An edge for detecting flaws, foreign matter, and film abnormalities at the end of the object to be detected by imaging the upper surface 1a, the end lower surface 1b, and the end side surface 1c of the disk-shaped object 1 to be detected. The optical system for imaging the end upper surface 1a, the lower surface 1b, and the side surface 1c of the test object 1 has a common objective lens 7 and is telecentric on the object side. The optical system for imaging the side surface of the object end includes the afocal magnifying optical systems 5 and 6 in the telecentric optical system, and the images of the upper end surface 1a, the lower surface 1b, and the end surface 1c of the test object end portion are coplanar. An end inspection apparatus characterized by forming an image on top 11.
[Selection] Figure 1

Description

  The present invention captures an image of an end upper surface, an end lower surface, and an end side surface of a disk-shaped test object such as a semiconductor wafer, and detects an end of the test object at a flaw, a foreign object, or a film abnormality. The present invention relates to a partial inspection apparatus and an exposure apparatus incorporating the same.

  As the density of semiconductor devices increases, the resolution required for the exposure apparatus is increasing. As a countermeasure against this, an immersion exposure apparatus has been developed and put into practical use. On the other hand, it is desirable to perform exposure to the periphery of the semiconductor wafer in order to increase the yield of the semiconductor element, and when using such a semiconductor wafer, in the case of an immersion type exposure apparatus, the exposure to the periphery of the semiconductor wafer is performed. It needs to be in a liquid state. At this time, if there is a foreign matter or film abnormality at the edge of the semiconductor wafer, a problem that the foreign matter or part of the film is lifted by the immersion liquid and sticks on the baking pattern is likely to occur. Therefore, it is becoming more important to perform end inspection of semiconductor wafers.

Conventionally, when performing a surface inspection of an edge of a semiconductor wafer, as disclosed in Japanese Patent Laid-Open No. 2006-64975 (Patent Document 1), optical systems for three directions of a front surface, a back surface, and a side surface are separately provided. The image was independently captured and image processing was performed, and image processing was performed to check for foreign matter and film peeling, bubbles in the film, and wraparound of the film. In the case of semiconductor wafers, since defects found by edge inspection occur accidentally, it is necessary to inspect all semiconductor wafers.
JP 2006-64975 A

  However, providing an optical system in three directions complicates the inspection apparatus, and requires image processing from three directions, resulting in a long inspection time.

  The present invention has been made in view of such circumstances, and provides an end inspection apparatus capable of imaging the front, back, and side surfaces of an end by a set of optical systems, and an exposure apparatus incorporating the end inspection apparatus. Is an issue.

  The first means for solving the problem includes three optical paths for imaging the upper end surface, the lower end surface and the end side surface of a flat test object, and an objective lens common to the three optical paths. And an optical path for imaging the side surface of the end portion has a magnifying optical system on the object side of the objective lens, and the images of the end top surface, the end bottom surface, and the end surface of the test object are on the same plane. It is the edge part inspection apparatus characterized by arrange | positioning so that it may image.

  The second means for solving the problem is the first means, wherein the magnifying optical system is an afocal optical system, and the three optical paths are telecentric on the object side. Is.

  The third means for solving the problem is the first means or the second means, wherein the light beam for observing the upper surface and the lower surface of the end portion is within a plane including the central axis of the object to be examined. It is bent, and the images of the end upper surface, the end lower surface, and the end side surface of the test object are formed in a straight line.

であることを特徴とするものである。 A fourth means for solving the problem is the first means or the second means, wherein the effective diameter of the lens group of the afocal optical system is φ, the magnification is β, and the objective lens NA is the numerical aperture, f _{1 is} the focal length, e _{3 is} the distance from the side surface of the test object to the main plane of the lens group 5 on the object side in the afocal optical system, and the top and bottom surfaces of the test object are imaged When the distance from the position where the luminous flux intersects the plane perpendicular to the end face of the test object to the test object upper and lower surfaces is D, and the thickness of the test object edge is t,

It is characterized by being.

  A fifth means for solving the above-mentioned problems is an exposure apparatus characterized in that an end inspection apparatus which is one of the first to fourth means is incorporated.

  According to the present invention, it is possible to provide an end inspection apparatus capable of imaging the front surface, back surface, and side surfaces of an end by a set of optical systems, and an exposure apparatus incorporating the end inspection apparatus.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of an end face inspection apparatus as an example of an embodiment of the present invention. A semiconductor wafer 1 as a test object is adsorbed by a wafer holder 2 that can rotate in a horizontal plane. A drive mechanism (not shown) for rotating the semiconductor wafer 1 is attached to the wafer holder 2, and a rotation operation is performed based on a signal from a control system.

  In the vicinity of the end of the semiconductor wafer 1, the mirror 3 for observing a part of the surface of the semiconductor wafer 1, the mirror 4 for observing a part of the back surface of the semiconductor wafer 1, and the side surface of the semiconductor wafer 1 are observed. The afocal optical systems 5 and 6 are arranged in a plane including the rotation axis of the semiconductor wafer 1. A light beam emitted from a point 1 a on the surface of the semiconductor wafer 1 is reflected by the mirror 3, changes its direction in a direction substantially parallel to the surface of the semiconductor wafer 1, and enters the objective lens 7 of the light receiving optical system. Similarly, a light beam emitted from a point 1b on the back surface of the semiconductor wafer 1 is reflected by the mirror 4, changes its direction in a direction substantially parallel to the surface of the semiconductor wafer 1, and enters the objective lens 7 of the light receiving optical system.

The light emitted from the side surface of the semiconductor wafer 1 passes through the afocal optical systems 5 and 6 and is enlarged to a predetermined magnification β, and then enters the objective lens 7 of the light receiving optical system.

In the light receiving optical system, the light collected by the objective lens 7 is imaged on the one-dimensional line sensor 11 by the imaging optical system 10 through the aperture stop 8. At this time, since the objective lens 7 is telecentricly arranged on the object side, the distance between the main plane of the objective lens 7 and the aperture stop 8 is equal to the focal length f ₁ of the objective lens 7. Further, the focal plane of the objective lens 7 coincides with the point 1a on the surface of the semiconductor wafer and the point 1b on the back surface of the semiconductor wafer, that is, the distance between the main point surface of the objective lens 7 and the front and back surfaces of the semiconductor wafer 1 is a mirror. 3 and 4 are arranged so as to coincide with each other within the range of the focal length focal depth of the objective lens 7.

  Hereinafter, the configuration of the optical system for observing the side surface of the semiconductor wafer 1 will be described in detail. As described above, since the objective lens 7 is telecentric, in order to observe the side surface 1c of the semiconductor wafer 1 on the same image plane, it is necessary to insert the afocal optical systems 5 and 6 and to guarantee the parallelism of the observation principal ray. .

FIG. 2 shows the vicinity of the end face of the semiconductor wafer 1 on which optical parameters are written. The focal length of the lens group 5 on the object side of the afocal optical system is f ₃ , the focal length of the lens group 6 on the image side of the afocal optical system is f ₂ , and the object of the afocal optical system from the side surface 1c of the semiconductor wafer 1 The distance to the main plane of the lens group 5 on the side is e ₃ , the distance between the main planes of the two lens groups 5 and 6 of the afocal optical system is e ₂ , and the main plane of the lens group 6 on the image side of the afocal optical system Let e ₁ be the distance to the main plane of the objective lens 7.

Here, the difference between the distance from the main plane of the objective lens 7 to the observation point 1a on the front surface on the semiconductor wafer 1 or the observation point 1b on the back surface and the distance from the main plane of the objective lens 7 to the side surface 1c of the semiconductor wafer 1, In other words, when the sum of AB and BC shown in FIG. 2 is D, the following relationship exists between the observation point 1 a on the surface of the semiconductor wafer 1, the observation point 1 b on the back surface of the semiconductor wafer 1, and the semiconductor wafer 1. An image of the side surface 1c is formed in one plane.

  Here, β is an enlargement ratio by the afocal optical system. More precisely, in the lens groups 5 and 6 of the afocal optical system, the main plane on the incident side and the main plane on the output side may not completely coincide with each other. It is necessary to subtract the interval from D in the above equation.

An example of the result of substituting numerical values is shown below. It goes without saying that there are solutions other than this numerical example that satisfy the above formula.

  In this embodiment shown in FIG. 1, a reflection illumination system for illuminating the sample surface via the objective lens 7 is added. The illumination light from the light source 15 is collected by the collector lens 14, reflected by the half mirror 9 through the field stop 13 and the illumination relay lens 12, and then passed through the objective lens 7 and the afocal optical systems 5 and 6. Each inspection surface 1a, 1b, 1c of the semiconductor wafer 1 is illuminated. This illumination system is Koehler illumination in which the image of the light source 15 is formed on the aperture stop 8 of the objective lens 7. Further, dark field illumination that illuminates the objective lens 7 and the afocal optical systems 5 and 6 may be used, or reflection illumination and dark field illumination may be used in combination.

  On the one-dimensional line sensor 11, the images of the front surface 1a of the semiconductor wafer 1, the back surface 1b of the semiconductor wafer 1, and the side surface 1c of the semiconductor wafer 1 are aligned in a straight line. Images of the above three portions of the cross section of the semiconductor wafer including the central axis of the wafer can be captured. The outer periphery of the semiconductor wafer can be inspected by rotating the semiconductor wafer 1. This is input to an image processing system (not shown) to detect foreign matter or film abnormality. When a two-dimensional image sensor is used, these three images do not need to be aligned on a straight line, and can be formed on the same plane, so that the mounting positions of the mirror 3 and the mirror 4 can be easily adjusted. Become.

Since the afocal optical systems 5 and 6 for side inspection need to be able to observe at least the range of the thickness t of the edge of the semiconductor wafer 1, the effective diameter of the lens group 6 that is enlarged by the magnifying system is enlarged. It is necessary to be larger than the sum of the image size and the imaging light beam diameter. The size of the field of view enlarged by the afocal optical system is a product βt of the edge thickness t and the magnification β of the afocal optical systems 5 and 6. Further, when the numerical aperture of the objective lens 7 is NA, the diameter of the light beam in the lens group 6 of the afocal optical system can be expressed as NA (f ₁ −e ₁ ) by proportional calculation. By substituting the above numerical values into this, an expression of the effective diameter φ of the lens group 6 is obtained.

In the optical system for observing the upper surface or the lower surface of the semiconductor wafer 1, as shown in FIG. 3, a light beam forming an image of a portion near the center passes near the afocal optical system for observing the side surface. For this reason, as shown in FIG. 3, the distance w from the edge of the semiconductor wafer within the range that can be observed by the optical system for observing the upper surface or the lower surface of the semiconductor wafer 1 is as follows from the condition that all the imaged light beams cannot be obtained. Limited to

  Actually, since the afocal optical system requires a larger diameter in terms of the lens configuration for the metal object for holding the lens and the aberration correction, βt in the above equation is the magnification of the afocal optical system in the field diameter. Since the range w where the edge can be observed becomes smaller, the size of the field of view must be determined in consideration of this amount.

  As described above, according to this embodiment, it is possible to simultaneously inspect the upper surface, the lower surface, and the side surface of the end surface of the semiconductor wafer using one one-dimensional line sensor without using a plurality of light receiving elements. Speeding up and downsizing of the apparatus are possible. For this reason, this edge inspection apparatus can be incorporated into a semiconductor exposure apparatus or a clean track in which a semiconductor exposure apparatus, a resist film coating apparatus, and a development apparatus are combined, and an edge inspection apparatus before placing a semiconductor wafer on an exposure stage. In order to prevent the occurrence of defects during exposure due to adhesion of foreign objects such as foreign matter or film on the exposure stage, so as not to place a semiconductor wafer with foreign matter or film abnormalities on the exposure stage. The yield of the semiconductor element can be improved.

  In particular, in an immersion exposure apparatus, foreign matter and film at the edge of a semiconductor wafer may float due to the immersion liquid and affect pattern projection. In the edge inspection apparatus according to the above embodiment, a semiconductor with foreign matter or film abnormality Sort the wafer so that it is not placed on the exposure stage. As a result, foreign matter and film can be prevented from abnormally adhering or dropping on the exposure stage, and defects can be prevented during pattern projection, greatly reducing the occurrence of defects in semiconductor elements. it can.

  Also, a semiconductor wafer center position detecting device that can detect the edge position of the semiconductor wafer from the intensity difference between the transmitted light of the illumination and the reflected light of the semiconductor wafer, and detects the center position of the semiconductor wafer from several edge positions by rotating the semiconductor wafer. The edge inspection can be performed simultaneously with the detection of the center position of the semiconductor wafer.

  Needless to say, the present invention can be used not only for semiconductor wafers but also for edge inspection of other wafers.

It is a figure which shows the outline | summary of the edge part inspection apparatus which is embodiment of this invention. It is a figure for demonstrating the outline | summary of a structure of the optical system in embodiment of this invention. It is a figure for demonstrating the effective diameter of the optical system in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor wafer, 2 ... Wafer holder, 3 ... Mirror, 4 ... Mirror, 5 ... Afocal optical system object side lens group, 6 ... Afocal optical system image side lens group, 7 ... Objective lens, 8 ... Aperture stop, 9 DESCRIPTION OF SYMBOLS ... Half mirror, 10 ... Imaging lens, 11 ... One-dimensional image sensor, 12 ... Illumination relay lens, 13 ... Field stop, 14 ... Collector lens, 15 ... Light source

Claims (5)

  The three optical paths for imaging the upper end surface, the lower end surface, and the end side surface of the flat test object, the objective lens common to the three optical paths, and the optical path for imaging the end side surface, It has a magnifying optical system on the object side of the objective lens, and is arranged so that images of the upper end surface, the lower end surface, and the end surface of the test object are formed on the same plane. End inspection device.   The end inspection apparatus according to claim 1, wherein the magnifying optical system is an afocal optical system, and the three optical paths are telecentric on the object side.   The edge inspection apparatus according to claim 1 or 2, wherein a light beam for observing the upper surface and the lower surface of the edge is bent in a plane including a central axis of the object to be tested, so that the edge of the object to be tested is detected. An end inspection apparatus characterized in that images of a part upper surface, an end lower surface, and an end side surface are formed in a straight line. 3. The edge inspection apparatus according to claim 1, wherein an effective diameter of the lens group of the afocal optical system is φ, an enlargement magnification is β, a numerical aperture of the objective lens is NA, and the object to be inspected. The distance from the side surface of the afocal optical system to the principal plane of the lens group on the object side in the afocal optical system is e ₃ , and the position at which the light flux that images the top and bottom surfaces of the test object intersects the plane perpendicular to the end surface of the test object When the distance from the upper surface and the lower surface of the test object is D, and the thickness of the edge of the test object is t,

An end inspection device characterized by being.   An exposure apparatus in which the edge inspection apparatus according to any one of claims 1 to 4 is incorporated.

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