JP2005274173A - Surface inspection method of contamination on surface of object to be inspected such as wafer substrate transparent glass for liquid crystal display or the like and surface inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface inspection method for inspecting contamination on the surface of a wafer substrate constituted so as to instantaneously discriminate the stain particles or contamination on the wafer substrate having a rough back surface difficult to inspect and taking time by a conventional technique or the flaw such as the surface unevenness or scratch of a fine region in a large visual field to specify the position thereof. <P>SOLUTION: A wafer is irradiated with a laser irradiation beam from the lateral side of the wafer in parallel to the surface of the wafer and the laser irradiation beam is moved in a direction vertical to the surface of the wafer to measure and inspect the particles bonded on the surface of the wafer and the unevenness, scratch or the like on the surface of the wafer over the whole surface of the wafer. Sheetlike light of a range wider than the surface of the wafer is used to instantaneously record the outer shape and position of the wafer to subsequently record scattered light of stain fine particles bonded to the surface of the wafer and a particle size is calculated from the intensities of scattered light to collectively measure the positions of the all of fine particles on the surface of the wafer and the respective particle sizes of them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a foreign matter / surface inspection method and apparatus on the surface of an object to be inspected, such as a wafer substrate and a transparent glass for a liquid crystal display. More specifically, it is difficult to inspect with the prior art and takes time, such as transparent surface and rough back surface of wafer substrate, liquid crystal display transparent glass, etc. It is related to a foreign substance / surface inspection method and its apparatus on the surface of an inspection object such as a wafer substrate, a transparent glass for liquid crystal display, etc., which can instantly identify defects in a wide field of view and specify their positions. is there.

A conventional inspection method for a substrate such as a wafer will be briefly described below.
(A) Inspection of foreign matter on wafer with mirror surface and thin film In conventional inspection of foreign matter on wafer with mirror surface and thin film, the substrate is often equipped with both vertical upward illumination and oblique illumination. A method of collecting scattered light at an angle that does not allow reflected light to enter. However, in this method, (a) the laser beam is not expanded, and scanning is performed on the wafer with a single beam. In addition, (b) it takes time to specify the position of the particle to be measured on the wafer.
(B) Surface Transparent Back Surface Roughness Foreign Material Inspection on Wafer As an example of this inspection, there is a method disclosed in Non-Patent Document 1.
In this method, it is necessary to discriminate and detect the front surface and the back surface, and the back surface noise is removed and the sensitivity of the apparatus is improved by a unique spatial filter that removes a signal from the back surface of the wafer. The laser beam is irradiated at a high angle with respect to the wafer surface. Since the wafer or optical head is placed on a linear stage and the wafer rotates, the optical head measures the surface in a spiral. Then, the inspection light receiver detects an OSA (Optica 1 Surface Ana1yzer) in which an ellipsometer, a reflectometer, a skitometer, and an optical profiler are combined as one optical head. In addition, the oblique irradiation light has a strong back surface reflection, and a very precise information light separation optical system is required to separate the scattered light from the fine particles adhering to the wafer surface from the disturbance light of the back surface scattering.

2004, Opto Device Technology Encyclopedia, P360, P359, Cande1a Instrument / Dongguan Technology

  However, in the method according to (B), since the light receiving optical system and the analysis algorithm are complicated for detection of particles on the back surface reflecting wafer, it is difficult to measure the wafer surface with a large field of view. In addition, the inspection time is likely to be long. Oblique irradiation light is strongly reflected from the back side, and it has the disadvantage that a very precise optical system for separating information light is required to separate the scattered light from the fine particles adhering to the wafer surface from the disturbance light from the backside scattering. is there.

(C) Inspection of transparent substrate for liquid crystal display As this transparent substrate inspection method, the surface of the glass substrate is irradiated with laser light from a low angle, and the scattered light from the foreign matter is received by the CCD light receiving element and detected as a foreign matter signal. There is a way to do it. This method does not detect foreign matter of 50 μm or less on the back surface with a sensitivity of 0.3 μm on the front surface. The detection unit emits low-angle laser light, and the CCD light-receiving unit is controlled by the autofocus unit from the direction perpendicular to the glass surface to improve the front / back separation performance. In addition, a line-shaped laser beam is irradiated on the surface of the sample substrate at a low angle, and scattered light from a foreign substance on the substrate is received by a line sensor via an imaging detection optical system disposed above the substrate. Therefore, there is no movable part in both the laser irradiation optical system and the detection optical system, and the entire scan / inspection can be performed by moving the XY stage on which the sample substrate is mounted. The inspection speed is 3 minutes / 1 sheet for a 1100 × 1250 mm substrate.
This method does not have the idea of inspecting the entire surface of the substrate to be inspected at a time because the irradiation light beam is in a line shape. Therefore, there are drawbacks such as long measurement time and long time for positioning when fine particles are detected. Further, since the irradiated laser light hits the back surface locally, the particle size detection sensitivity is lowered.
(D) Inspection of all types of substrates from mirror wafers to surface transparent backside rough wafers This method is the same as the non-patent document 1 described in (B) described above, but there are problems as described in (B). is there.
(E) Fine particle inspection on patterned wafer Oblique illumination and upward detection are performed as this inspection method (see Non-Patent Document 2 below), but there are problems similar to those described above.

Measurement and inspection technology in SEMICON industry, Nobuyuki Akiyama, Foreign matter inspection technology, 0 pluseE, Vol.23, NO5 (2001-5), P558

Problems due to the detection method of fine particles adhering to the wafer surface used in most of the conventional inspection methods and inspection apparatuses described above.
1) The upward detection method using oblique illumination is highly effective for detecting contaminant particles on a mirror wafer such as a silicon wafer because no disturbance light enters from the wafer surface. However, the back surface is particularly rough when the wafer surface is a transparent substrate. In the measurement of fine particles, it is very difficult to separate the scattered light from the fine particles adhering to the wafer surface from the back scattered disturbance light because the back surface reflection of oblique irradiation light is strong. Therefore, there is a disadvantage that a very precise optical system for separating information light is required for measuring the fine particles adhering to the surface of the wafer whose surface is transparent. Further, since the disturbance light on the wafer surface due to oblique irradiation becomes stronger than the scattered light from the fine particles, it is difficult to reduce the measurable size of the fine particles.
2) Furthermore, in the illumination method using one beam as irradiation light, in order to inspect the entire surface of the wafer, a particle is scanned on the surface of the wafer hit by the detector, and the measurement point is scanned to scan the entire surface of the wafer. Inspection is required, and the conventional method of 1-beam irradiation has the disadvantages that it is difficult to measure on the wafer surface with a large field of view and the inspection time is likely to be long.

Therefore, in order to solve the above-mentioned problems of the prior art, the present inventor shortens the inspection time by using a sheet-shaped light in a wider range than the surface of the object to be inspected (wafer) and The following inspection apparatus and method are provided that can solve the problem of reflected light from the back surface by irradiating the object surface in parallel.
(1) A light beam such as a laser beam is scanned, or the laser beam is converted into a parallel sheet-like light by an optical system, and (a) irradiation light parallel to the wafer surface as the inspection object, and (b) the inspection object. A parallel irradiation light having a wider range than that of the wafer surface is produced and irradiated in parallel to the wafer surface.
(2) When the parallel irradiation light is irradiated at a height that is parallel to the wafer surface and hits the side surface of the wafer and is photographed with a CCD camera from above the wafer surface, the shape of the cross section parallel to the wafer surface is clear. Observed.
(3) As a result, the entire shape of the wafer surface is instantaneously recorded at a specific position on the screen of the CCD camera.
(4) Expanded parallel irradiation light parallel to the wafer surface is gradually lifted in parallel from the position in contact with the wafer surface and rises to a position where the wafer surface is not touched.
(5) During this time, the contaminating fine particles adhering to the wafer surface are irradiated with parallel light and emit side scattered light.
(6) Since the direction of the irradiation light such as laser light is irradiated parallel to the wafer surface, the disturbance light scattered from the wafer surface is much weaker than the scattered light such as adhering fine particles. Scattered light is easily separated and observed.
(7) The influence of disturbance light from the wafer surface or back surface is much smaller than when the wafer surface is irradiated obliquely.
(8) In the scattered light measurement, detecting the scattered light by the particles on the wafer surface while the irradiation light is gradually lowered from the position not touching the wafer to the position touching the wafer surface has the same effect. The scattered light can also be detected by moving the wafer surface up and down without moving the irradiation optical system.

For this reason, the technical solution means adopted by the present invention is:
Laser irradiation light is irradiated in parallel to the surface of the inspection object from the side of the inspection object such as a wafer or transparent glass for liquid crystal display, and the irradiation light is moved in a direction perpendicular to the surface of the inspection object. The surface shape is recorded, and the scattered light is moved in the direction perpendicular to the surface of the inspection object to adhere to the surface of the inspection object, unevenness on the surface of the inspection object, side scatter from scratches, etc. By capturing light and displaying within the contour of the surface of the object to be inspected, the particle diameter, unevenness on the surface of the object to be inspected, and scratch are obtained from the intensity of scattered light over the entire surface of the object to be inspected. This is a foreign matter / surface inspection method on the surface of an inspection object.
The irradiation light is a foreign matter / surface inspection method on the surface of an object to be inspected, wherein the irradiation light is a single laser beam or a plurality of laser beams irradiated from various directions.
Further, the irradiation light is a parallel scanning sheet-like light or an enlarged parallel sheet light, and is a foreign matter / surface inspection method on the surface of an inspection object.
The method for inspecting foreign matter / surface on the surface of the object to be inspected is characterized in that the parallel scanning sheet light or the enlarged parallel sheet light is a parallel scanning sheet light or an enlarged parallel sheet light wider than the surface of the object to be inspected. It is.
Further, the apparatus is used for the foreign matter / surface inspection method on the surface of the inspection object described above, wherein the apparatus irradiates the surface of the inspection object in parallel with the laser light source and the laser light from the laser light source. Laser irradiating means, supporting means for supporting the object to be inspected, imaging means for photographing scattered light or reflected light from the object to be inspected, scattered light or reflected light from the object to be inspected, or defects or foreign matter on the surface of the object to be inspected The laser irradiation means and the support means are provided with an adjustment mechanism capable of adjusting the position of each other, and are a foreign object / surface inspection apparatus on the surface of an object to be inspected.
The laser irradiation means for irradiating the surface of the inspection object in parallel can irradiate a sheet-like laser beam.
Further, in order to photograph the scattered light intensity of the fine particles over the entire surface of the object to be inspected, a half-wave plate is disposed in the optical system of the laser irradiation unit, and a polarizing plate is disposed in the optical system of the imaging unit. This is a foreign matter / surface inspection apparatus on the surface of an object to be inspected.
Further, the present invention is the foreign matter / surface inspection apparatus on the surface of the object to be inspected, wherein a spectroscopic optical system is arranged in the optical system of the photographing means so that the composition of the fine particles can be measured.

According to the present invention,
1. A wide inspection field of view can be created in accordance with the size of a substrate (for example, a wafer) as an object to be inspected, and the entire surface of the wafer can be inspected at a time.
2. Compared with the conventional method by using a method that suppresses disturbance light on the wafer surface by irradiating magnified parallel light to the wafer surface and instantly acquires weak scattered light from contaminating particles. There is an advantage of increasing the particle size limit and increasing the inspection speed.
3. The apparatus is relatively simple in structure, and is superior to the conventional method in terms of manufacturing cost.
And the like.

  The present invention irradiates laser irradiation light parallel to the surface of the inspection object from the side of the inspection object, moves the irradiation light in a direction perpendicular to the inspection object surface, and adheres to the inspection object surface. This is a method for measuring and inspecting particles, unevenness on the surface of the object to be inspected, scratches and the like over the entire surface of the object to be inspected. Use a sheet of light in a wider range than the surface of the object to be inspected, irradiate it from the side parallel to the surface of the object to be inspected (wafer), pull it up gradually, and the parallel irradiation light touches the surface of the object to be inspected The image is taken with a CCD camera from above the wafer surface at the moment when it rises to a position where it does not exist. By this process, the outer shape and position of the wafer can be recorded instantaneously. Next, when the irradiation light is moved further upward, the contaminated fine particles adhering to the wafer surface are irradiated to the parallel light, so that side scattered light that is much stronger than the disturbance light from the wafer surface is emitted from the fine particles. By recording these scattered light and further obtaining the particle diameter from the intensity of the scattered light, it is possible to measure the position of all the contaminating fine particles on the object to be inspected and the respective particle diameters at once. Inspection time can be significantly shortened. Further, according to the present invention, the projection on the wafer surface is detected by irradiation with parallel light, so that not only the contaminating fine particles but also the unevenness and scratches of the inspection object itself can be rapidly inspected.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic configuration diagram of an apparatus for carrying out the present invention. The apparatus has substantially the same configuration as that of a conventional inspection apparatus, and an image acquired from the CCD camera shown in FIG. 1 is analyzed by an image analysis apparatus, and the state of contaminant particles on the wafer surface is appropriately displayed by display means. Is done. FIG. 2 is an enlarged view of the main part of the present invention, FIG. 3 is a plan view of the main part, and FIG. 4 is a plan view of irradiation means for irradiating laser light parallel to the wafer surface from a laser light source.

In FIG. 1, 1 is a wafer support, 2 is a wafer as an object to be inspected, 3 is a laser light source, 4 is a beam expander, 5 is a laser irradiation means, 5a is a sheet-like laser beam, 6 is a CCD camera, and 7 is an image. In the analysis apparatus and these optical systems, a mirror, a lens, a half-wave plate, and a polarizing plate 8 are appropriately arranged. In the following description, the inspection object will be described on the premise of a wafer substrate. However, the inspection object is not limited to the wafer substrate, and may be a transparent glass substrate for liquid crystal display.
As will be described later, the laser irradiation means 5 and the wafer support 1 are capable of irradiating laser light parallel to the wafer surface, and changing the relative position (position in the X, Y, and Z directions) between the laser light and the wafer surface. Can be done. The position adjusting mechanism can employ various currently known means.

  In this apparatus, the irradiation light from the laser light source 3 is irradiated from the side surface to the wafer 2 as a sheet-like laser light 5a from the laser irradiation means 5 through a mirror, a beam expander, and a half-wave plate. This state is shown in FIG. The parallel irradiation light beam may be irradiated from a plurality of directions. Scattered light from the surface of the wafer 2 is photographed by the CCD camera 6 through the polarizing plate 8 and analyzed by the image analysis device 7 (see FIG. 1), and fine particles on the wafer surface, unevenness of the wafer itself, scratches, etc. are removed. To detect. As shown in FIG. 3, the laser light is irradiated onto the wafer from the side surface as sheet-like light 5a having a width larger than the surface of the wafer. The laser beam 5a irradiated at this time is irradiated through a λ / 2 plate (1/2 wavelength plate). The light beam irradiated in parallel on the object to be inspected (substrate surface) may be irradiated parallel to the surface in a form that licks the inspection surface.

An inspection method using the above apparatus will be described.
As shown in FIG. 2, the laser light is irradiated in parallel to the wafer surface as irradiation light parallel to the wafer surface to be inspected or parallel sheet-shaped irradiation light in a wider range than the wafer surface to be inspected. The laser beam may be a single laser beam or a plurality of laser beams irradiated from multiple directions.

  First, the relative position of the laser irradiation means 5 or the wafer support is adjusted to irradiate the parallel irradiation light 5a parallel to the surface of the wafer 2 and at a height corresponding to the side surface of the wafer, from above the surface of the wafer 2. Take picture with CCD camera 6. Specifically, the laser beam 5a is irradiated from the side surface in parallel to the wafer surface to be inspected, and is gradually pulled upward to raise the position where the parallel irradiation light does not touch the wafer 2 surface. By photographing this with the CCD camera 6 from above the surface of the wafer 2, the outer shape and position of the wafer 2 are recorded instantaneously when the sheet-like parallel irradiation light 5 a comes into contact with the surface of the wafer 2. As a result, a cross-sectional shape parallel to the surface of the wafer 2 is observed in a clear shape. In other words, the entire shape of the wafer 2 surface is instantaneously recorded at a specific position on the screen of the CCD camera.

Thereafter, the parallel irradiation light 5a in the form of an enlarged sheet parallel to the surface of the wafer 2 is gradually pulled up in parallel from the position in contact with the surface of the wafer 2 and rises to a position where the surface of the wafer 2 is not touched. During this time, the contaminating fine particles adhering to the surface of the wafer 2 are irradiated with parallel light and emit side scattered light that is much stronger than the disturbance light from the wafer surface. Since the direction of the irradiation light such as laser light is applied to the surface of the wafer 2 in parallel, the disturbance light scattered from the surface of the wafer 2 is much weaker than the scattered light such as adhering fine particles. Light is easily observed separately. The scattered light intensity and position are displayed in real time in the wafer 2 contour observed by the method described above. Further, the particle diameter is obtained from the My scattering (including Rayleigh scattering) by the scattered light intensity, and the particle diameter is displayed on the wafer image surface together with the position in an image.
As described above, in the present invention, the influence of disturbance light from the wafer front surface or the back surface is remarkably reduced as compared with the case of irradiating the wafer surface obliquely with respect to the wafer surface as in the conventional inspection method.
In the scattered light measurement, the same effect can be obtained by detecting scattered light caused by particles on the wafer surface while the irradiation light is gradually lowered from a position not touching the wafer to a position touching the wafer surface. Furthermore, the irradiation light may be fixed and the wafer support may be moved up and down.

By the way, when carrying out the above inspection method, the irradiating laser beam corrects the Gaussian distribution intensity to an optical system using a pinhole or a lens (such correction is well known in the art and will not be described). It is important to keep the distribution intensity of the light beam cross section so that the intensity of the end portion of the light beam does not become weak.
In order to separate the scattered light from the wafer surface to be inspected and adhering fine particles, and to capture the scattered light intensity of the fine particles over the entire surface of the inspected substrate on the image in real time, the polarization plane of the irradiated light should be at a certain angle with the wafer surface It is necessary to have. In order to appropriately select the polarization plane of the irradiation light, the irradiation light is irradiated through a λ / 2 plate (1/2 wavelength plate).
In order to separate the image of the scattered light from the wafer surface and the scattered light from the fine particles more clearly, an optical system with a polarizing plate is used to capture the image of the scattered light, etc., and the scattered light image from the fine particles is clearly defined. Make it separable.
The wavelength of irradiation light such as laser light is appropriately selected according to the characteristics of the object to be measured.
The light receiving optical system has a spectroscopic optical system added in front of the CCD camera so that the composition of the fine particles can be measured.
The measured particle diameter is obtained from the My scattering (including Rayleigh scattering) by the intensity of scattered light from the particle, and is displayed imageically together with the position on the wafer surface.
Instead of the CCD camera, a light intensity detector (for example, an array sensor) or an image detector (for example, an ICC camera (a CCD camera with an image intensifier)) can be used.

As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the embodiment. For example, the light beam irradiated in parallel to the surface of the object to be inspected may be irradiated in parallel to the surface so as to lick the inspection surface. The irradiation light beam may be a parallel light beam such as a laser beam, or may be a light beam from a light source other than the laser. Furthermore, the irradiation light may be a single light beam, may be an enlarged sheet light parallel to the substrate to be inspected, or a plurality of laser lights irradiated from multiple directions. In addition, the polarization plane of the irradiated light is irradiated through the half-wave plate at a constant angle with the wafer surface, and a polarizing plate and a wavelength filter are added in front of the CCD camera as a light receiver to reduce the particle size of the fine particles. Improves inspection performance and enables composition measurement. In addition, the object to be inspected is not limited to a wafer substrate, a transparent glass substrate for a liquid crystal display, or the like, but can also be a substrate that achieves the same function.
In addition, the present invention can be implemented in any other form without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner.

  INDUSTRIAL APPLICABILITY The present invention can be widely used for inspection of wafers with transparent front surfaces and rough back surfaces, inspection of transparent substrates for liquid crystal displays, inspection of all types of substrates including mirror-surface wafers, inspection of fine particles on patterned wafers, and the like.

It is a schematic block diagram of the apparatus for implementing this invention. It is an enlarged view of the principal part of this invention. It is a top view of the principal part. It is a top view of the irradiation means to irradiate a laser beam parallel to a wafer surface from a laser light source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer support stand 2 Wafer as a to-be-inspected object 3 Laser light source 4 Beam expander 5 Laser irradiation means 5a Sheet-like laser beam 6 CCD camera 7 Image analyzer 8 Polarizing plate

Claims (8)

Laser irradiation light is irradiated in parallel to the surface of the inspection object from the side of the inspection object such as a wafer or transparent glass for liquid crystal display, and the irradiation light is moved in a direction perpendicular to the surface of the inspection object. The surface shape is recorded, and the scattered light is moved in the direction perpendicular to the surface of the inspection object to adhere to the surface of the inspection object, unevenness on the surface of the inspection object, side scatter from scratches, etc. By capturing light and displaying within the contour of the surface of the object to be inspected, the particle diameter, unevenness on the surface of the object to be inspected, and scratch are obtained from the intensity of scattered light over the entire surface of the object to be inspected. Inspection method for foreign matter on the surface of the object to be inspected. 2. The foreign matter / surface inspection method on the surface of an inspection object according to claim 1, wherein the irradiation light is a single laser beam or a plurality of laser beams irradiated from various directions. 2. The foreign matter / surface inspection method on the surface of an object to be inspected according to claim 1, wherein the irradiation light is a parallel scanning sheet light or an expanded parallel sheet light. 4. The foreign matter on the surface of the inspection object according to claim 3, wherein the parallel scanning sheet light or the enlarged parallel sheet light is parallel scanning sheet light wider than the inspection object surface or the enlarged parallel sheet light. -Surface inspection method. An apparatus for use in the foreign matter / surface inspection method on a surface of an object to be inspected according to any one of claims 1 to 4, wherein the apparatus uses a laser light source and a laser beam from the laser light source to inspect the object to be inspected. Laser irradiation means for irradiating the surface in parallel, support means for supporting the inspection object as the object to be measured, scattered light or reflected light from the inspection object, or scattered light or reflected light from defects or foreign matter on the inspection object surface An apparatus for inspecting a foreign object / surface on the surface of an object to be inspected, comprising: an imaging means for taking an image, wherein the laser irradiating means and the supporting means are provided with an adjustment mechanism capable of adjusting the positions of each other. 6. The foreign matter / surface inspection apparatus on the surface of an inspection object according to claim 5, wherein the laser irradiation means for irradiating the surface of the inspection object in parallel can irradiate a sheet-like laser beam. In order to image the scattered light intensity of fine particles over the entire surface of the inspection object, a half-wave plate is disposed in the optical system of the laser irradiation unit, and a polarizing plate is disposed in the optical system of the imaging unit. The foreign matter / surface inspection apparatus on the surface of the inspection object according to claim 5 or 6. 7. A foreign matter / surface inspection on the surface of an object to be inspected according to claim 5 or 6, wherein a spectroscopic optical system is arranged in the optical system of the photographing means so that the composition of the fine particles can be measured. apparatus.

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