JPH10325803A - Foreign matter inspection equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foreign matter inspection equipment in which detection of a foreign matter and analysis of a detected foreign matter can be performed using a single equipment while facilitating positioning at an analyzing point and a foreign matter can be detected easily even if a sample has mirror surface. SOLUTION: The foreign matter inspection equipment comprises an analyzing means 2, and means 3 for optically observing the surface of a sample wherein the surface of the sample to be observed by the optical observation means 3 includes the point on the surface of the sample to be irradiated by a probe of the analyzing means 2. A part common to the observing region of the optical observation means 3 and the analyzing region of the analyzing means 2 is provided and the surface of the sample is irradiated with an oblique illumination means 4 for projecting a parallel light to the surface of the sample to be observed by the optical observation means at an angle with respect to the optical axis thereof. According to the arrangement, a foreign matter can be detected easily even if the sample has mirror surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter inspection apparatus, and more particularly to a foreign matter inspection apparatus for analyzing foreign matter present on a sample having a mirror-like surface.

[0002]

2. Description of the Related Art As one of surface analysis for analyzing a sample surface,
A foreign substance inspection for inspecting a foreign substance present on a sample surface is known. Conventionally, foreign matter detection is performed by visually inspecting an observation image obtained by an imaging device or the like on a sample surface, and further, when analyzing the detected foreign matter, an optical system for detecting foreign matter present on the sample surface is used. This is achieved by combining two devices, a foreign matter detection device and an analyzer for analyzing the detected foreign matter. For example, when inspecting and analyzing a foreign substance on a semiconductor wafer, the foreign substance is detected using an optical foreign substance inspection apparatus, the position coordinates thereof are obtained, and the position coordinates are converted to another analyzing apparatus for analysis. Is going.

When the analysis range is narrow, it is also possible to use an analyzer such as SEM, EPMA, or AUGER to analyze foreign matter after searching for foreign matter on the sample surface by observing the SEM image.

[0004]

In the conventional foreign substance inspection by observing an SEM image, when the size of the foreign substance is very small, or when the number of the foreign substances is small and the distribution density is low, the foreign substance is detected on a wide sample. In addition, in the case of combining two devices, an optical foreign matter detection device and an analyzer, it is not always easy in terms of reproducibility of coordinates by performing coordinate conversion on the analyzer. There is a problem that the position of the foreign matter cannot be reproduced.

[0005] In addition, the optical foreign matter detection device is generally configured to irradiate illumination light onto the sample surface from directly above and observe reflected light reflected directly above from the sample surface.
If the surface of the sample to be analyzed, such as a hard disk or semiconductor wafer, has a mirror-like surface, the reflected light from the mirror surface and the scattered light from the foreign material are both observed at the same time. There is also a problem that it may be.

Accordingly, the present invention solves the above-mentioned conventional problems, and can detect foreign matter and analyze the detected foreign matter with one apparatus, and can easily perform positioning to an analysis point. It is an object of the present invention to provide an inspection apparatus, and to provide a foreign substance inspection apparatus that can easily detect a foreign substance even when the surface of the sample is mirror-like.

[0007]

According to the present invention, there is provided a foreign matter inspection apparatus comprising: an observation area of an optical observation means for searching for a foreign matter; and an analysis area of an analysis means for analyzing a detected foreign matter, on the surface of a sample to be inspected. By providing the common part, the optical observation means and the analysis means are incorporated in the same apparatus, and foreign matter can be detected and analyzed by one apparatus, and the positioning to the analysis point is facilitated. By using oblique illumination, it is possible to perform a foreign substance inspection on a mirror-like sample surface.

The foreign matter inspection apparatus according to the present invention includes an analyzing means for analyzing foreign matter on the surface of the sample and an optical observation means for observing the surface of the sample. Since the means includes the irradiation point of the probe that irradiates the sample surface, a common portion is provided in the observation area of the optical observation means and the analysis area of the analysis means. Further, the configuration of the illumination for illuminating the sample surface is made by oblique light illuminating means for projecting parallel rays at an angle with respect to the optical axis of the optical observation means on the sample surface observed by the optical observation means. In addition, even when the surface of the sample is mirror-like, the foreign object can be easily detected by the optical observation means.

According to the foreign matter inspection apparatus of the present invention, the parallel rays projected by the oblique illumination unit enter the sample surface at an angle to the optical axis of the optical observation unit. The specular sample surface reflects the incident light in the direction opposite to the optical axis of the optical observation means at the same angle as the incident angle. Therefore, since the reflected light has an angle with respect to the optical axis of the optical observation means, the reflected light reflected from the mirror surface of the sample surface is not observed by the optical observation means. On the other hand, when there is a foreign substance on the surface of the sample, the parallel light projected by the oblique illumination unit is scattered by the foreign substance to emit scattered light, and a part of the scattered light is observed by the optical observation unit. This makes it possible to detect a foreign substance present on the mirror-like sample surface.

Since the observation area of the optical observation means and the analysis area of the analysis means are on the same coordinates, the position of the foreign matter detected by the optical observation means and the irradiation point of the probe are aligned without performing coordinate conversion. Accordingly, foreign matter analysis by the analysis means can be performed.

An embodiment of the analysis means of the present invention is a SEM,
The analysis is performed by irradiating a foreign material with a probe such as an electron beam and detecting X-rays and secondary electrons emitted from the foreign material. An embodiment of the optical observation means of the present invention is a CCD
It is an imaging device such as a device, and can obtain an observation image as image data. According to an embodiment of the present invention, the foreign matter inspection apparatus includes a position data detecting means for obtaining position data of the foreign matter from an observation image of the optical observation means, and a position adjustment of the foreign matter and the probe of the analyzing means based on the detected position data. It is provided with a positioning means for performing the positioning, whereby the positioning to the analysis point can be performed automatically.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. A configuration example according to an embodiment of the present invention will be described with reference to a schematic configuration diagram for explaining the foreign substance inspection device of the present invention in FIG. In FIG. 1, a foreign matter inspection apparatus 1 includes an analysis system 2 that analyzes a foreign matter on a sample s using a probe, and optically observes the surface of the sample, detects the foreign matter on the sample s, and determines its position. Optical observation system 3
An oblique illumination system 4 for irradiating illumination light obliquely to the surface of the sample s, and a stage for holding the sample s and moving and positioning the sample s with respect to the analysis system 2 or the optical observation system 3. The control unit 6 controls the respective systems. The input of the set value to the control unit 6 can be performed via the input unit 8. An image obtained by the analysis system 2 or the optical observation system 3 can be displayed on the display device 7.

The analysis system 2 includes a probe source 21 such as an electron gun for irradiating the sample s with a probe such as an electron beam, and a detector 2 for detecting X-rays and secondary electrons emitted from the sample s.
2 and an analyzer 23 for performing analysis using the detection signal detected by the detector 22. The analyzer is SEM, E
PMA, AUGER, or the like can be used.

The optical observation system 3 is for observing the surface of the sample s optically and includes an image pickup means 31 such as a CCD camera.
And an image processing unit 32 that performs signal processing of the image data obtained by the imaging unit 31 to detect a foreign substance. The oblique illumination system 4 projects parallel rays at an angle with respect to the optical axis of the optical observation system 3 on the surface of the sample s to a region to be observed by the optical observation system 3, and elevates the sample surface with the elevation angle. A light source 41 for irradiating a parallel light beam from an oblique direction at an angle of degrees is provided. The light source 41 is disposed obliquely above the sample s such that the projected parallel light beam is irradiated on the sample surface by the irradiation point of the probe.

As a light source for illumination, white light and laser light such as a halogen lamp can be used, and light intensity can be increased by converging light to an irradiation point on a sample using a lens system. Since the optical observation system of the present invention observes scattered light, a laser beam having a high light intensity is advantageous in terms of the light intensity to be detected. Thus, at the irradiation point of the probe on the sample surface, the light source 41 emits a parallel light beam having an angle with respect to the optical axis of the optical observation system 3.

FIG. 2 is a view for explaining the state of optical observation of the sample surface by the oblique illumination system 4 of the present invention. FIG.
(A) shows a case where no foreign matter exists on the surface of the sample s. The oblique incident light 4a projected from a light source of oblique illumination (not shown) is reflected by the mirror surface 10 of the sample s to become reflected light 4b. Since the reflection angle of the reflected light 4b is the same as the incident angle on the opposite side to the optical axis of the optical observation system, the reflected light 4b does not enter the optical system 33 such as a lens and the light receiving unit 31, and the optical observation Not observed in system 3.

On the other hand, FIG. 2B shows a case where a foreign substance exists on the surface of the sample s. Oblique incident light 4a
Is scattered by the Tyndall phenomenon in the foreign substance 11,
The scattered light 4c is scattered in various directions. Part of the scattered light 4c enters the light receiving unit 31 via the optical system 33 and is observed by the optical observation system 3.

Accordingly, by performing the oblique illumination, the optical observation system 3 can observe and detect only the foreign matter on the sample surface, and the optical image of the observed foreign matter floats on a dark field and is observed. .

FIG. 2C shows an example of an image pickup signal by the light receiving section 31. The light receiving section 31 detects only the foreign matter 11 on the sample as an image and outputs a light receiving signal corresponding to the position of the foreign matter 11. The light receiving signal detected by the light receiving section 31 is almost only a signal from the foreign substance 11 because the signal intensity from the mirror surface portion of the sample surface is very small.

An image signal received by an imaging device such as a CCD camera is subjected to image processing in an image processing section 32 to clarify an image and determine position coordinates. Since an image signal obtained by oblique illumination has a very small signal from a mirror surface, an image signal obtained without performing a binarization process is often used as it is as a binarized signal. The signal processing of the value conversion processing can be omitted.

Further, in determining the position coordinates, the position on the optical observation system can be determined by associating the scanning signal of the CCD camera with the coordinates. It can be obtained by combining the position of the system and the position on the optical observation system.

Further, the foreign matter can be selected by image processing by designating an image to be observed floating on a dark field on a display device, or automatically by threshold processing of an image signal. The position coordinates are obtained by determining the position coordinates. The alignment between the selected foreign substance and the probe of the analysis system can be performed by moving the foreign substance side or the probe side using the position coordinates of the foreign substance obtained by the image processing.

The stage system 5 includes a stage 51 that holds the sample s and is movable in two-dimensional or three-dimensional directions, a stage driving unit 53 that drives the stage 51, and a stage control unit 52 that controls the stage driving unit 53. And The stage control unit 52 controls the foreign matter inspection device 1 from the stage 51.
The position coordinates of the stage with respect to are input, and the stage driving unit 53 is controlled based on a control signal from the control unit, and the foreign object and the probe are aligned.

The control unit 6 inputs the position coordinates of the foreign matter obtained by the image processing unit 32 and sends the position coordinates of the foreign matter automatically selected or selected by the input unit 8 to the stage control unit 52, and the position of the foreign matter is determined by the stage 51. Controls the image processing unit 32
The optical observation image obtained in the step is displayed on the display device 7, and
Detecting device 2 based on a detection signal of detector 22 of analysis system 2
The analysis image obtained in 3 is displayed on the display device 7. In addition,
The foreign matter inspection apparatus shown in FIG. 1 shows a configuration in which the stage 51 is moved to align the foreign matter and the probe. However, a structure in which the analysis system is moved to align the foreign matter and the probe. It can also be.

Next, the operation of the foreign matter inspection apparatus of the present invention will be described with reference to FIGS. FIG. 3 shows an operation state of aligning the foreign matter detected by the optical observation means with the analysis position of the analysis means, and FIG. 4 is a flowchart for explaining the operation of the operation.

FIGS. 3 (a) and 3 (b) show optical observation images of the sample surface in a coordinate system (XY coordinates) fixed on the foreign matter inspection apparatus. FIG. 3 (a) shows the positions of the foreign matter and the probe. FIG. 3B shows a state before the alignment, and FIG. 3B shows a state after the alignment between the foreign matter and the probe. 3 and 4 show the case where the center point of the beam axis of the probe coincides with the optical axis point of the optical observation system on the sample surface. A similar process can be performed by performing coordinate conversion on the center position shift and performing position adjustment.

When the sample surface is irradiated by oblique illumination and the irradiated surface is observed by an optical observation system, an observation image of the optical observation area 35 in FIG. 3A is obtained (step S1). The optical observation area 35 includes the beam axis center point B of the probe of the analysis system. By performing the oblique illumination, the foreign matter (point P in the figure) existing on the mirror-like sample in the optical observation area 35 rises and is observed in the dark field. The foreign substance is identified by observing an observation image displayed on the display screen, and an analysis point is selected. The analysis points can be selected using a pointing device such as a mouse on the display screen, or the control unit can automatically select the analysis points using the image data itself or the binarized image data. (Step S2).

The position coordinates of the selected analysis point P are represented by (xp, xy) on the coordinate system (xy coordinates) provided in the optical observation area 35.
yp). Here, the center point B of the beam axis of the probe
Coordinate system (xy) in which the coordinate positions of
(Coordinates), the beam axis center point B is set in the coordinate system (XY coordinates) provided on the particle inspection apparatus.
Are represented by (XB, YB), and the analysis point P is (XB +
xp, YB + yp). The image processing unit 32 and the control unit 6 calculate the position coordinates of the selected analysis point P and store the calculated position coordinates in a storage unit (not shown). When automatically calculating the position coordinates of the analysis point P from the image data of the optical observation image, it can be performed by associating the scanning signal of the optical observation image with the position coordinates on the optical observation region 35 (step S).
3).

The analysis points P selected and stored in steps S1 to S3 will be referred to as steps S4 to S3.
The analysis of each analysis point is performed by the processing of step 7. In the state shown in FIG. 3A, the center point B of the beam axis of the probe and the analysis point P
Do not always coincide with each other, and a position shift occurs. Therefore, by the following processing, the sample supported on the stage 41 is moved with respect to the beam axis by the movement of the stage 41, and the beam axis center point B and the analysis point P are matched.

Therefore, an analysis point P to be analyzed is designated from the analysis points P selected and stored in step S3 (step S4), and the position coordinates of the analysis point are read out (step S4).
5). The stage system 5 is driven based on the read position coordinates of the analysis point P, and the alignment between the beam axis center point B and the analysis point P is performed. In FIG. 3B, the stage 41 is moved from the pre-movement stage 41a to the post-movement stage 41b by moving the stage -xp in the X-axis direction and -yp in the Y-axis direction. Thereby, the beam axis center point B and the analysis point P in the optical observation area 35 are aligned (step S).
6).

After the alignment between the beam axis center point B and the analysis point P, an analysis process is performed. The analysis result can be displayed on a display screen together with the optical observation image, and data can be recorded in a recording device (not shown) (step S7). The analysis of the selected analysis point P can be performed by repeating the processing of steps S4 to S6 for the stored analysis point P (step S8).

An optical microscope can be used as an optical observation system used in the foreign substance inspection apparatus of the present invention. Foreign matter having a size of several microns can be observed.

According to the foreign substance inspection apparatus of the present invention, a small and small number of foreign substances can be easily found, and accurate analysis of foreign substances can be performed while increasing the magnification of an optical observation system or the analysis system such as an SEM. It can be carried out.

Further, by using a blue laser or a clean laser as a light source for use in the foreign matter inspection apparatus of the present invention, high-brightness illumination becomes possible, and it becomes easier to find foreign matter, and when a clean laser is used. In this case, high CCD sensitivity and high visual sensitivity can be obtained.

Further, since the foreign matter inspection apparatus of the present invention can obtain the position coordinates of the foreign matter, it is possible to specify the position where the foreign matter is generated in the production line by combining with the production line of the sample object.

[0036]

As described above, according to the foreign matter inspection apparatus of the present invention, foreign matter detection and analysis of the detected foreign matter can be performed by one apparatus, and positioning to the analysis point can be easily performed. I can do it. Further, even when the sample surface is mirror-like, foreign matter detection can be easily performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining a foreign substance inspection device of the present invention.

FIG. 2 is a diagram for explaining a state of optical observation of a sample surface by the oblique illumination system of the present invention.

FIG. 3 is a view showing an operation of aligning a foreign substance and an analysis position by the foreign substance inspection apparatus according to the present invention.

FIG. 4 is a flowchart illustrating an operation of a positioning operation between a foreign substance and an analysis position by the foreign substance inspection apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Foreign substance inspection apparatus, 2 analysis system ... 3 ... optical observation system, 4 ...
Oblique light system, 5: Stage system, 6: Control unit, 7: Display device,
8 input unit, 10 mirror surface, 11 foreign matter, 21 probe source, 22 detector, 23 analyzer, 31 light receiving unit, 3
2 ... Image processing unit, 41 ... Light source, 51 ... Stage, 52 ...
Stage control unit, 53: stage drive unit, s: sample.

Claims (1)

[Claims] An analyzing means for analyzing foreign matter on the sample surface using a probe irradiating the sample surface; an optical observing means for observing a sample surface including an irradiation point of the probe on the sample surface; Oblique light illuminating means for projecting a parallel light beam at an angle to the optical axis of the optical observation means with respect to the sample surface observed by the optical observation means, and a probe for foreign matter detected by the optical observation means A foreign matter inspection device, wherein the foreign matter is analyzed by an analysis means.