JPH11274256A - Sample checking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sample checking device for detecting a fine foreign object on a wafer while distinguishing it from a circuit pattern and for easily performing composition analysis or analysis such as shape observation. SOLUTION: This sample checking device is provided with a reflected light observing part 2 for irradiating the surface of a sample 4 to be measured such as an LSI wafer with beam light and observing reflected light from the said surface, abnormality observing/analyzing part 3, movable stage 5 for moving the sample 4 to be measured between the respective fields of view of the reflected light observing part 2 and the abnormality observing/analyzing part 3 and in the field of view, information processing part 6 for processing into desired shape based on information provided by the reflected light observing part 2 and the abnormality observing/analyzing part 3, coordinate storage part 7 for storing the position of an abnormal part confirmed by the information processing part 6 based on the information from the reflected light observing part 2, control part 9 for controlling the drive of the movable stage 5 based on the position coordinate of the abnormal part stored in the coordinate storage part 7, and display part 8 for displaying the processing result of the desired shape at the information processing part 6 on the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample inspection apparatus for detecting, observing, and analyzing foreign matter adhering to the surface of a semiconductor wafer.

[0002]

2. Description of the Related Art In recent years, advanced manufacturing techniques have been used in the semiconductor-related industry. In particular, in the LSI manufacturing process, wiring patterns and transistor elements having micron and submicron dimensions are formed on semiconductor wafers. On the other hand, with the miniaturization of manufacturing technology, it was not a problem in the past,
The minute foreign matter adhering to the wafer surface causes disconnection or short circuit of the circuit pattern, which is a major cause of occurrence of defects. Therefore, it is important to manage these foreign substances and suppress the generation of foreign substances in order to improve the yield. These foreign substances are generated in an LSI manufacturing process including a wet process, a deposition process, a lithographic process, a diffusion process, an ion implantation process, and a metallization process. Therefore, assuming the size, shape, composition, etc. of the foreign matter,
It is indispensable to find out when and in what process the generation of foreign matter is suppressed.

Conventionally, when observing minute foreign matter on the surface of a semiconductor, a visual inspection has been performed using an optical microscope of several hundred times. However, as the circuit pattern becomes finer, the size of the foreign matter that needs to be observed becomes larger. It became finer, and observation with the naked eye became difficult.

Further, detection of minute foreign matter from a large wafer area is realized by a foreign matter detection device which irradiates light to the wafer and detects light scattering from the foreign matter. However, foreign matter is present. Only the coordinates and size are known, but no specific shape or composition can be observed. Therefore, after detecting the foreign matter with the foreign matter detection device, the sample is moved into the field of view of the electron microscope based on the position coordinates of the detected foreign matter, and the shape is observed by the scanning electron microscope, and the energy dispersive X-ray analyzer (EDX) is used.
In general, a method of performing a composition analysis by using the method is performed. One example of such an apparatus is disclosed in Japanese Patent Publication No. 4-68622.

FIG. 4 is a block diagram showing a conventional sample inspection apparatus disclosed in Japanese Patent Publication No. 4-58622. In the apparatus shown in this figure, a foreign substance inspection unit 103 using an optical means such as a laser and a scanning electron microscope (hereinafter, referred to as a scanning electron microscope) are provided on a ceiling in a vacuum sample chamber 102 evacuated by a vacuum pump 101.
(Referred to as “SEM”) 104 is provided separately. A moving stage 10 for moving an object to be inspected such as an LSI wafer 105 between and within the respective visual fields of the foreign substance detection unit 103 and the SEM 104 is provided on the floor in the sample chamber 102.
6 are installed. The moving stage 106 is a motor 10
The position of the moving stage 106 is output by an encoder 108 connected to a motor 107. The LSI wafer 105 is mounted on the sample stage 10.
The sample stage 109 is rotatable by a motor 110 on a moving stage 106. The position of the sample stage 109 is the motor 11
It is output by the encoder 111 connected to 0.

[0006] To the motors 107 and 110, a sample scanning unit 112 for controlling their driving is connected. The encoders 108 and 111 are connected to a coordinate storage unit 113 that stores the position where foreign matter is attached to the LSI wafer 105. The coordinate storage unit 22 stores the foreign object detection signal 114 detected by the foreign object detection unit 103 and the encoder 10
8 and 111 are input. The foreign substance detection signal 114 becomes, for example, “High” level when the foreign substance detection unit 103 detects a foreign substance on the LSI wafer 105. The sample scanning section 112 and the coordinate storage section 113 are connected to a control section 115, and the control section 115 exchanges information with them to control the entire inspection apparatus.

When a foreign substance inspection is performed by such an apparatus, first, an LSI wafer 105 to be inspected is placed on a sample stage 109 in a vacuum sample chamber 102. The foreign substance detection unit 103 using an optical unit such as a laser detects foreign substances on the LSI wafer 105 that moves spirally by the motors 107 and 110. When a foreign object is detected, the foreign object detection signal 114 changes from “Low” level to “High”.
Level. At the start, the encoder 10
8 and 111 are latched in the coordinate storage unit 113, and L
The position of the foreign matter on the SI wafer 105 is stored. Therefore, the position of the foreign matter is obtained in polar coordinates. LSI wafer 10
When the inspection of the entire surface of 5 or several chips is completed, the moving stage 106 is moved by the motor 107 into the field of view of the SEM 104. Since the detected position coordinates of the foreign substance are stored in the coordinate storage unit 113, the sample scanning unit 112 finely moves the motors 107 and 110 based on the data and positions the sample stage 109 and the moving stage 106. As a result, an SEM signal of a foreign substance at a position to be observed can be obtained.

When the sample to be inspected is an LSI wafer with a circuit pattern, the foreign matter inspection section 103 has, for example, the configuration shown in FIG. In FIG. 5, the S-polarized laser light is directed onto the LSI wafer 105 by the S-polarized laser 116 at an angle ψ.
Irradiation. ψ is about 1 degree. Here, polarized light that oscillates perpendicularly to the plane formed by the irradiation laser light and the wafer normal is called S-polarized light, and polarized light that oscillates parallel to it is called P-polarized light. At this time, LS
The scattered light from the pattern portion on the I-wafer 105 does not change its polarization direction and proceeds toward the objective lens 117 as S-polarized light. Contains. So objective lens 1
A polarizing plate 118 for blocking S-polarized light is provided behind 17,
By detecting the light passing through the photodiode 119, only the scattered light (P-polarized component) from the foreign matter is detected. This makes it possible to detect the position of the foreign substance on the LSI wafer with the circuit pattern.

As a result, the coordinate storage unit 113 stores the LSI
The position coordinates of all the foreign substances adhering to an arbitrary position on the wafer 105 are stored. next,
The control unit 115 reads the position coordinates of each foreign substance stored in the coordinate storage unit 113, controls the driving of the motor 107 via the sample scanning unit 112, and controls the movement stage 106
The moving stage 106 and the sample stage 109 are moved to the lower side of the lens barrel of the M104, and the motor 107 and the motor 110 are drive-controlled to finely control the moving stage 106 and the sample stage 109 so that each foreign substance exists in the field of view of the SEM 104. In this way, the S
By analyzing the EM signal, it is possible to analyze and analyze each foreign substance.

[0010]

In the above-described conventional sample inspection apparatus, an abnormal portion is detected by observing scattered light with respect to incident laser light. For example, when detecting a foreign substance placed on a bare wafer, since the wafer surface hardly scatters the incident laser light, the intensity of the scattered light detection between the surface where the foreign substance is present and the surface where no foreign substance is present is detected. High contrast can be obtained, and foreign matter can be detected. However, when observing foreign matter on a wafer with a circuit pattern, the background other than the scattered light from the foreign matter is strong because the surface of the wafer on which no foreign matter exists also changes the polarization angle of the S-polarized incident laser light. This makes it difficult to detect minute foreign matter.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sample inspection apparatus for detecting minute foreign matter on a wafer, in particular, by distinguishing it from a circuit pattern and easily performing analysis such as composition analysis and shape observation.

[0012]

In order to achieve the above object, a sample inspection apparatus according to the present invention includes a reflected light observation means for irradiating a light beam on a surface of a sample to be measured and observing light reflected from the surface. Abnormal observation and analysis means for observing and analyzing an abnormal portion of the surface of the sample to be measured, and
A moving unit that moves between and within the respective fields of view of the reflected light observation unit and the abnormal observation / analysis unit, and detects an abnormal portion on the surface of the measurement sample based on information obtained by the reflected light observation unit And, based on the information obtained by the abnormality observation and analysis means, the information processing unit that determines whether the detected surface abnormality was a foreign substance, or what kind of foreign substance was A coordinate storage unit for storing position coordinates when the information processing unit detects an abnormal location on the surface of the measurement sample; and moving the moving unit based on the position coordinates of the abnormal location stored in the coordinate storage unit. A control unit for causing an abnormal portion on the surface of the measurement sample to be within the visual field of the abnormal observation / analysis unit; and a display unit for externally displaying a processing result by the information processing unit. And wherein the door.

When the sample to be measured is a wafer with a circuit pattern, the reflected light observing means includes an illuminating unit for irradiating the surface of the sample to be measured with a light beam, and an image formed by light reflected from the surface of the sample to be measured. It is preferable that the apparatus includes an imaging unit for imaging. In this case, the information processing unit stores the image data obtained by the imaging unit of the abnormality detection unit, and compares the image data of the same pattern on the sample to be measured, thereby obtaining the surface of the sample to be measured. Abnormalities are detected.

If the sample to be measured is a bare wafer having no circuit pattern, the reflected light observation means includes an illuminating unit for irradiating the surface of the sample with beam light, and a reflected light from the surface of the sample to be measured. It is preferable to provide a light detector for receiving light. In this case, the information processing unit detects an abnormality on the surface of the sample to be measured from a change in the intensity of the reflected light obtained by the photodetector of the reflected light observation unit.

With the above configuration, it is possible to accurately detect foreign matter on a silicon wafer having a complicated circuit pattern.

In the sample inspection apparatus thus configured, when an abnormal point on the surface of the measurement sample is detected by the information processing means based on the information obtained by the reflected light observation means, the detected information is detected. The coordinates are stored in the coordinate storage means. On the basis of the position coordinates of the abnormal part stored in the coordinate storage means, the control unit moves the moving means, and puts the abnormal part on the surface of the measurement sample within the visual field of the abnormal observation / analysis means. Thereby, the abnormal part on the surface of the measurement sample is observed in detail by the observation means of the abnormality observation / analysis means, and further analyzed by the analysis means.

The observation means of the foreign substance observation / analysis means is preferably an electron microscope.
An atomic force microscope may be used.

The analyzing means of the foreign substance observing / analyzing means is desirably an X-ray detector, but may be an Auger electron detector, a time-of-flight secondary ion mass spectrometer, or a laser microprobe mass spectrometer. It may be a device.

Further, based on the information obtained by the foreign substance observing / analyzing means, classification based on the properties of the foreign substance such as composition and shape, and foreign substance map creation may be performed by the information processing means.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram for explaining a configuration of a sample inspection apparatus according to an embodiment of the present invention. As shown in FIG.
A vacuum sample chamber 1 whose inside is evacuated by an exhaust pump is provided. A reflected light observation unit 2 and an abnormal observation / analysis unit 3 are separately provided in the upper part of the vacuum sample chamber 1. The reflected light observation unit 2 irradiates the surface of the sample to be measured with a beam light as described later, and observes the reflected light from the surface. In this embodiment, the means for observing abnormalities in the abnormal observing / analyzing unit 3 is a scanning electron microscope, but may be an ion microscope or an atomic force microscope. In this embodiment, the means of the abnormality analysis is an energy dispersive X-ray analyzer (EDX), but it is an Auger electron detector, a time-of-flight secondary ion mass spectrometer, or a laser microprobe mass analyzer. Is also good.

A sample 4 to be measured, such as an LSI wafer, is mounted in a lower portion of the sample chamber 1, and the reflected light observation unit 2
A moving stage 5 that moves between and within the visual fields of the analysis unit 3 is provided. The optical axis when irradiating the light beam with the reflected light observation unit 1 and the optical axis when observing or analyzing an abnormal part with the observation means or analysis means of the abnormal observation / analysis unit 3 are at least on the sample to be measured. Match.

Further, outside the vacuum sample chamber 1, information obtained by the reflected light observation section 2 and the abnormal observation / analysis section 3 is stored, and an information processing section 6 for processing into a desired form based on the information.
A coordinate storage unit 7 for storing a position of an abnormal spot on the surface of the sample 4 to be measured, which is confirmed by the information processing unit 6 based on information from the reflected light observation unit 2; A control unit 9 for driving and controlling the moving stage 5 based on the position coordinates of the abnormal portion on the surface of the measurement sample 4, a display unit 8 for displaying a processing result of a desired form in the information processing unit 6 to the outside, Is provided.

When information about the surface of the sample 4 to be measured is obtained by the reflected light observation unit 2, the information processing unit 6 detects the presence of an abnormal portion on the surface of the sample to be measured based on the information. . When the foreign substance observation / analysis unit 3 obtains the observation / analysis information on the abnormal portion on the surface of the sample to be measured, it is determined whether the abnormality is a foreign substance or what kind of foreign substance is based on the information. It takes a processing form of judging whether or not the user is alive.

When a sample is inspected by such an apparatus, first, the sample 4 to be measured is placed on the moving stage 5 in the vacuum sample chamber 1. By moving the moving stage 5 in the X direction and the Y direction, the surface of the sample 4 to be measured is moved in the XY direction by the light beam from the illumination unit of the reflected light observation unit 2.
Scanned. The beam light from the illumination unit may be white light.

When the sample 4 to be measured has a circuit pattern, the reflected light observation unit 2 includes, for example, an illuminating unit (not shown) for irradiating the surface of the sample 4 with a light beam as shown in FIG. A CCD camera 10 serving as an image pickup unit for observing an image based on light reflected from the surface of the sample 4 to be measured, and an objective lens 11 and an eyepiece 12 for imaging the reflected light from the sample 4 to be measured on the CCD camera 10 And In this case, the surface of the sample 4 to be measured is XY-scanned by the beam light from the illumination unit of the reflected light observation unit 2, and an image based on the light reflected from the surface of the sample 4 to be measured is reflected by the reflected light observation unit 2
And the image data is sent to the information processing section 6. The information processing unit 6 includes an image memory, and sequentially stores the image data sent from the reflected light observation unit 2. Each of these image data is compared in the information processing section 6 with image data of a portion having the same pattern on the sample to be measured, thereby detecting the presence of an abnormality. When the sample 4 to be measured is a wafer, the information processing unit 6
Abnormal spots on the wafer surface are detected by comparing the image data of the dies on the wafer obtained by the reflected light observation unit 2 with the dies or the same circuit pattern. At this time, the position coordinates of the abnormal part on the sample 4 to be measured are stored in the coordinate storage unit 7.

When the sample 4 to be measured does not have a circuit pattern on the surface, the reflected light observation unit 2 irradiates the surface of the sample 4 with a laser beam as shown in FIG. A laser light source 13 serving as an illuminating unit and a laser beam light from the laser light source 13
And a photodiode 15 that is a photodetector that receives (observes) reflected light from the surface of the sample 4 to be measured via the half mirror 14. . In this case, the surface of the sample 4 to be measured is X-rayed by the light beam from the illumination unit of the reflected light observation unit 2.
Y scanning is performed, and the reflected light from the surface of the sample 4 to be measured is detected (observed) by the photodiode 15 of the reflected light observation unit 2, and the detection signal is sent to the information processing unit 6. Since the reflected light from the sample 4 to be measured has a constant intensity as long as there is no abnormality on the surface, the detection signal from the photodiode 15 associated therewith is also constant. However, when there is an abnormality on the surface of the sample 4 to be measured, the reflected light is scattered from the sample 4 to be measured, and the intensity decreases.
Accordingly, the signal level from the photodiode 15 also decreases. Therefore, the presence of the abnormality is detected by the information processing unit 6 detecting a change in the signal level according to the intensity of the reflected light. At this time, the position coordinates of the abnormal part on the sample 4 to be measured are stored in the coordinate storage unit 7.

When the detection of an abnormal portion on the sample 4 to be measured by the reflected light observation unit 2 is completed, the control unit 9 sets the coordinate storage unit 7
The moving stage 5 is moved within the visual field of the abnormal observation / analysis unit 3 based on the position data of the abnormal site stored in the storage unit, and an arbitrary abnormal site on the surface of the sample 4 to be measured is detected in the abnormal observation / analysis unit 3. It is positioned on the optical axis of the observation means. Then, an electron beam is applied to the abnormal portion by an electron gun of a scanning electron microscope as the abnormal observation means, and detailed shape observation and accurate coordinate confirmation of the abnormal portion are performed. It is desirable that the accurate confirmation of the coordinates of the abnormal part be performed by software based on image data obtained by a scanning electron microscope. The exact coordinates of the confirmed abnormal location are stored in the coordinate storage unit 7, and the control unit 9 finely moves the moving stage 5 based on this, and the abnormal location is the abnormality analysis unit of the abnormality observation / analysis unit 3. The energy dispersive X-ray analyzer described above is used to detect the characteristic X-rays from an abnormal location and analyze the composition of the foreign matter. By repeating such an operation for each detected abnormal point, it is possible to observe and analyze all the abnormal points on the surface of the sample 4 to be measured. In addition, abnormal observation
The analysis unit 3 does not perform the composition analysis, and may end up only observing the detailed shape of the abnormal part.

The observation information and analysis information of the abnormal part obtained by the abnormality observation / analysis part 3 are sent to the information processing part 9 and classified and detected based on the detailed shape of the abnormal part and the elemental composition. It is determined whether the surface abnormality was a foreign substance or what kind of foreign substance was. Further, a foreign matter map indicating which kind of foreign matter exists at which position on the surface of the sample 4 to be measured is also created. These results are output to the display unit 8 so that the user can obtain them. Note that the criteria for the classification of the abnormal portion may be other than the shape and element composition.

Further, the sample inspection apparatus as described above generates an alarm when the number of detected foreign substances is larger than the pre-registered arbitrary data or when the analysis result matches the pre-registered arbitrary element. By emitting
It may be configured to notify the user that the abnormality has been detected and that the result of the abnormality analysis has been obtained.

[0030]

According to the present invention, not only can a large number of fine foreign substances and crystal defects adhering to the surface of a sample to be measured such as an LSI wafer be detected at high speed, but also the shape of each of these fine foreign substances can be observed. It is possible to classify foreign substances based on these data by performing composition analysis or composition analysis. In addition, all of these series of operations can be performed automatically and at high speed. Furthermore, the method of acquiring image data based on the reflected light from the surface of the measurement sample and comparing them for the detection of abnormal spots has been adopted, so it is possible to accurately detect minute foreign matter on a wafer with a circuit pattern, etc. Can be. As a result, it is possible to investigate the cause of the generation of foreign matter in the manufacturing process of a semiconductor or the like, and it is possible to significantly improve the yield of products.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a sample inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a reflected light observation unit for a sample to be inspected with a pattern to be inspected by the sample inspection apparatus according to the embodiment of the present invention;

FIG. 3 is a schematic diagram for explaining a reflected light observation unit for a pattern-free sample to be inspected by the sample inspection apparatus according to the embodiment of the present invention;

FIG. 4 is a block diagram illustrating a conventional sample inspection apparatus.

FIG. 5 is a schematic diagram for explaining a foreign substance detection unit of the sample inspection device shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 vacuum sample chamber 2 reflected light observation unit 3 abnormal observation / analysis unit 4 sample to be measured 5 moving stage 6 information processing unit 7 coordinate storage unit 8 display unit 9 control unit 10 CCD camera 11 objective lens 12 eyepiece 13 laser light source 14 half Mirror 15 Photodiode

Claims (15)

[Claims] Irradiating a light beam on a surface of a sample to be measured;
Reflected light observation means for observing reflected light from the surface; abnormal observation / analysis means for observing and analyzing an abnormal portion of the surface of the sample to be measured; and the reflected light observation means on which the sample to be measured is placed. A moving unit that moves between and within the visual fields of the abnormal observation / analysis unit, and detects an abnormal portion on the surface of the measurement sample based on information obtained by the reflected light observation unit, and Based on the information obtained by the observation / analysis means, based on the information obtained by the observing / analyzing means, whether or not the detected surface abnormality was a foreign substance, or an information processing unit for determining what kind of foreign substance was, Coordinate storage means for storing position coordinates when an abnormal point on the surface of the measurement sample is detected, and moving the moving means based on the position coordinates of the abnormal point stored in the coordinate storage means, and A sample inspection apparatus, comprising: a control unit for bringing an abnormal portion of the surface of the surface into a visual field of the abnormal observation / analysis unit; and a display unit for externally displaying a processing result by the information processing unit. . 2. An optical axis when irradiating the abnormal light with the reflected light by the reflected light observation means, and an optical axis when observing or analyzing the abnormal spot by the observation means or analysis means of the abnormal observation / analysis means. 2. The sample inspection apparatus according to claim 1, wherein the values are identical at least on the sample to be measured. 3. The reflected light observing means includes an illuminating unit for irradiating a light beam on the surface of the sample to be measured, and a photodetector for receiving light reflected from the surface of the sample to be measured. The sample inspection device according to claim 1, wherein 4. The information processing means detects an abnormality on the surface of the sample to be measured from a change in the intensity of the reflected light obtained by a photodetector of the reflected light observation means. 4. The sample inspection device according to 3. 5. The apparatus according to claim 1, wherein the reflected light observation unit includes an illuminating unit that irradiates the surface of the sample to be measured with a light beam, and an imaging unit that captures an image using light reflected from the surface of the sample to be measured. The sample inspection device according to claim 1, wherein 6. The information processing means detects an abnormality on the surface of the measured sample by comparing image data of the same pattern on the measured sample obtained by the imaging unit of the abnormality detecting means. The sample inspection device according to claim 5, wherein: 7. The information processing means, based on information obtained by the abnormality observation / analysis means, generates a foreign matter map indicating which kind of foreign matter exists at which position on the surface of the substrate to be measured. The sample inspection device according to claim 1, wherein the sample inspection device is created. 8. The sample inspection apparatus according to claim 1, wherein the observation means of the observation / analysis means is an electron microscope. 9. The sample inspection apparatus according to claim 1, wherein the observation means of the observation / analysis means is an ion microscope. 10. The sample inspection apparatus according to claim 1, wherein the observation means of the observation / analysis means is an atomic force microscope. 11. The sample inspection apparatus according to claim 1, wherein the analysis means of the observation / analysis means is an X-ray detector. 12. The sample inspection apparatus according to claim 1, wherein the analysis means of the observation / analysis means is an Auger electron detection device. 13. The sample inspection apparatus according to claim 1, wherein the analysis means of the observation / analysis means is a time-of-flight secondary ion mass spectrometer. 14. The sample inspection apparatus according to claim 1, wherein the analysis means of the observation / analysis means is a laser microprobe mass spectrometer. 15. The sample inspection apparatus according to claim 1, wherein when the number of detected foreign substances is larger than pre-registered arbitrary data, or when the analysis result matches an pre-registered arbitrary element, A sample inspection device which detects an abnormality by issuing an alarm and notifies that an abnormality analysis result has been obtained.