JP2002216694A - Defect inspecting device and method for manufacturing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspecting device capable of reliably inspecting defects even if irradiation energy of primary charged particle beam is raised for a sample surface to be charged. SOLUTION: A measurement image data is generated in a step 12 based on the intensity of secondary electrons detected in a step 11. In a step 13, a distortion correcting data is generated to correct an image distorted by charging. In a step 14, the entire measurement image data is corrected based on the distortion correcting data to generate a corrected image data. In a step 15, the image is compared with any one of a reference image data, a corrected image of other small region of the same sample, and a corrected image of the same small region of other sample, and outputs a defectiveness in case of inconsistency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for irradiating a sample with a charged particle beam, detecting secondary charged particles generated from an irradiation point of the sample, and performing a defect inspection of a device, and a device using the same. It relates to a manufacturing method.

[0002]

2. Description of the Related Art A defect inspection of a mask pattern for manufacturing a semiconductor device or a pattern formed on a semiconductor wafer is performed by detecting secondary electrons emitted from a sample when the surface of the sample is irradiated with a primary electron beam. This is performed by obtaining a pattern image of the sample and comparing it with one of the reference pattern, the pattern image of another sample, and the pattern image of another portion of the same sample. As a method of obtaining an image by secondary electrons, a method of scanning the sample surface with a primary electron beam to obtain an image pattern (hereinafter, simply referred to as “scanning defect inspection apparatus”), a one-dimensional image of secondary electrons or 2. Description of the Related Art There is known an image forming apparatus that forms a two-dimensional image on a detection unit by an image projection optical system (hereinafter, simply referred to as an “image projection type defect inspection apparatus”).

[0003]

In either case, in order to obtain a high-accuracy image by secondary electrons, one method is required.
Although it is necessary to increase the irradiation amount of the secondary electron beam, when the irradiation amount is increased, there is a problem that the sample surface is charged and an image due to the secondary electrons is distorted. The method of performing the averaging process by irradiating a plurality of times and reducing the irradiation amount so that the image distortion is sufficiently reduced has a problem that the throughput of the defect inspection is reduced.

An object of the present invention is to provide a defect inspection apparatus capable of performing a highly reliable defect inspection even when the sample surface is charged by increasing the irradiation amount of the primary charged particle beam in order to increase the throughput. And

[0005]

A defect inspection apparatus according to the present invention detects a secondary charged particle generated from an irradiation point when a charged particle beam is irradiated on a sample, and divides the inspection area of the sample into small particles. Means for performing a defect inspection of the sample on a region-by-region basis, wherein a means for creating image data of the small region based on the secondary charged particles; and a plurality of image data between the created image data and the reference image data. Based on an error at a specific point, an image in which distortion correction data due to electrification of the sample surface due to the charged particle irradiation is obtained, and based on the distortion correction data, the entire generated image data is corrected to generate corrected image data Correcting means, the corrected image data, corrected image data of another small area, corrected image data of another sample,
Image comparison means for comparing at least one image data of the reference image data with respect to the entire image, wherein a defect of the sample is detected based on an output of the image comparison means.

Further, the plurality of specific points are selected from corners of a pattern included in the created image data and the reference image data.

Further, the present invention is applied to an apparatus for performing a defect inspection by irradiating a sample with a plurality of primary charged particle beams.

[0008] Further, a defect inspection of a device is performed using the defect inspection apparatus described above.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

First, a description will be given of an image distortion due to charging of a sample surface by taking a scanning defect inspection apparatus as an example. FIG. 3 is a diagram for explaining the influence of charging of the sample surface. The inspection area 1 of the sample is divided into a plurality of small areas 2 and an inspection is performed for each small area. It is assumed that primary electron beam irradiation and secondary electron detection are performed only by electrical scanning by deflecting the primary electron beam.

The emission efficiency η of secondary electrons when an insulator is irradiated with an electron beam is expressed as shown in FIG. 4. At a beam energy where η is greater than 1, more electrons are emitted than incident electrons. Therefore, the surface of the insulator is positively charged. Therefore, when scanning is started from the starting point 5 of the small area 2 in FIG.
Since the scanned area is positively charged and the electron beam is returned to the positive charge, it is necessary to scan to the position 7 in order to irradiate the original position 6. Therefore, in order to scan the small area 2, it is necessary to instruct the scanning of the area 3. Conversely, an image due to secondary electrons when a rectangular region scanning instruction is issued will be distorted.

Therefore, in order to inspect the small area 2, it is necessary to instruct the scanning of the area 4 large enough to cover the area 3, and to detect the secondary electrons at that time to create an image. . This is the same in the case of the projection type defect inspection apparatus, and it is necessary to set the irradiation area of the primary electrons and the image formation area to be large in consideration of the influence of distortion due to charging.

FIG. 1 shows a schematic flow of the defect inspection processing of the present invention. In step 11, the intensity of secondary electrons emitted from the sample surface when the small region 2 is irradiated with the primary electron beam is detected. A scanning type defect inspection apparatus uses a scintillator or the like, and a projection type defect inspection apparatus uses a one-dimensional or two-dimensional CCD (Charge Coupled Device) or the like.

In step 412, measurement image data is created based on the detected intensity of the secondary electrons, the irradiation position of the primary electron beam, and the position information of the stage for holding and moving the sample. This measurement image is as shown in FIG. The reference image of the corresponding small area is shown in FIG.
It is as shown in (1).

Next, in step 13, distortion correction data for correcting an image distorted by charging is created.
When creating the distortion correction data, first, the coordinates of a plurality of corners of the pattern included in the reference image and the measurement image are compared. Since the corners of the measurement image cannot be obtained accurately, the intersection of two sides (for example, the sides in the X direction and the Y direction) is calculated and used as the coordinates of the corner. In the example of FIG. 2, the coordinates (x ₁ , y ₁ ), (x ₂ , y ₁ ),... (X _i ,
y ₁ ), (x ₁ , y ₂ ),... (x _i , y ₂ ) _,.
y _i ) are the coordinates (X ₁ , Y ₁ ), (X ₂ ,
(Y ₁ ),... (X _i , Y ₁ ), (X ₁ , Y ₂ ) _,.
Y ₂ ),... (X _i , Y _i ). Based on these errors, distortion correction data for making the measurement image of FIG. 2B correspond to the reference image of FIG. 2A is created. As a method for creating the distortion correction data, a method described in JP-A-62-58621 can be adopted.

Subsequently, in step 14, the entire measurement image data is corrected based on the distortion correction data to generate corrected image data. The corrected image data is data from which the influence of the charging of the sample surface has been removed.

Finally, in step 15, the image is compared with any one of the reference image data, the corrected image of another small region of the same sample, and the corrected image of the same small region of another sample. The point is output as a defect position. As described above, since the corners of the measurement image are rounded and cannot be obtained accurately, a mismatch at this portion is not determined to be a defect. Note that the processing of steps 12 to 15 can be realized using one or a plurality of processors.

The embodiment of the present invention described above is more effective when applied to a defect inspection apparatus that irradiates a sample by scanning a plurality of primary charged particle beams. FIG. 6 is a diagram schematically illustrating an example of a defect inspection apparatus using a plurality of primary electron beams. In the figure, an electron beam emitted from an electron gun 41 is converged by a condenser lens 42 to form a crossover at a point CO. At this crossover point CO, a stop 44 having an aperture for determining NA is arranged.

Below the condenser lens 42, a first multi-aperture plate 43 having a plurality of openings is arranged, thereby forming a plurality of primary electron beams. Each of the primary electron beams formed by the first multi-aperture plate 43 is reduced by a reduction lens 45 and
6 is projected onto the principal deflection surface. That is, after focusing at the point 55, the sample 48 is focused by the objective lens 47. The plurality of primary electron beams emitted from the first multi-aperture plate 43 are deflected by a deflector located between the reduction lens 45 and the objective lens 47 so as to simultaneously scan the surface of the sample 48.

As shown in FIG. 6, the multi-aperture plate 43 has a larger distance from the condenser lens 42 from the center to the periphery, as shown in FIG. It has a stepped structure.

The plurality of focused primary electron beams irradiate a plurality of points on the sample 48, and the secondary electron beams emitted from the plurality of irradiated points are attracted to the electric field of the objective lens 47. It is focused to a point 56 in front of the EXB separator 46, that is, a point 56 on the sample 48 side with respect to the main deflection surface of the EXB separator 46. This is because each primary electron beam has energy of 500 eV on the sample surface, whereas the secondary electron beam has energy of only several ev. The plurality of secondary electron beams emitted from the sample 48 are deflected by the EXB separator 46 below the axis connecting the electron gun 41 and the sample 48, separated from the primary electron beam, and incident on the secondary optical system.

The secondary optical system has magnifying lenses 49 and 50, and the secondary electron beam passing through these magnifying lenses 49 and 50 passes through a plurality of openings of the second multi-aperture plate 51, Is imaged on the detector 52. The plurality of openings formed in the second multi-aperture plate 51 disposed in front of the detector 52 correspond to the plurality of openings formed in the first multi-aperture plate 3 on a one-to-one basis. .

Each detector 52 converts the detected secondary electron beam into an electric signal representing its intensity. The electric signals output from the respective detectors 52 are respectively amplified by the amplifiers 53 and then received by the image processing unit 54 and converted into image data. Since a scanning signal for deflecting the primary electron beam is further supplied to the image processing unit 54, the image processing unit 54 displays an image representing the surface of the sample 48. By comparing this image with a standard pattern, a defect of the sample 48 can be detected.
The sample 48 is moved to a position near the optical axis of the primary optical system by registration, and a line width evaluation signal is taken out by line scanning, and the signal is calibrated appropriately to measure the line width of the pattern on the sample 48. be able to.

Here, the primary electron beam passing through the opening of the first multi-aperture plate 43 is focused on the surface of the sample 48, and the secondary electron beam emitted from the sample 48 is imaged on the detector 52. At this time, it is necessary to pay particular attention to minimize the effects of the three aberrations of the primary optical system and the secondary optical system, namely, distortion, field curvature, and field astigmatism. Regarding the relationship between the irradiation position intervals of a plurality of primary electron beams and the secondary optical system, crosstalk between a plurality of beams can be eliminated by separating the primary electron beams by a distance larger than the aberration of the secondary optical system. be able to.

In the defect inspection apparatus for irradiating a plurality of electron beams as shown in FIG. 6, since the irradiation amount of the electron beam is large,
The influence of charging increases. Therefore, there is a great merit that the correction as described in the above embodiment is performed to remove the influence of charging.

The defect inspection apparatus thus configured can be used for defect inspection of a semiconductor device.

FIG. 5 is a flowchart showing an example of a method for manufacturing a semiconductor device. In the chip inspection process in this example, if the defect inspection device of the present invention is used,
Inspection can be performed with high throughput, and 100% inspection is also possible.
Product yield can be improved and defective products can be prevented from being shipped.

[0028]

As is clear from the above description, according to the present invention, even if the measured image is distorted due to the charging of the sample, the image corrected for the distortion can be inspected for defects, so that the primary electron beam can be inspected. Since the emission efficiency of secondary electrons can be increased by increasing the irradiation amount, a detection signal with a good S / N ratio can be obtained, and the reliability of defect inspection is improved.

Also, since the intersection of the pattern sides is used as the corner coordinates of the measured image, and the mismatch of the corners is not determined as a defect, the probability of detecting an erroneous defect due to the influence of the R of the corner inherent in the measured image. Becomes lower.

[Brief description of the drawings]

FIG. 1 is a schematic flowchart of a defect inspection process of the present invention.

FIG. 2 is a diagram showing an example of a reference image and a measurement image of a small area.

FIG. 3 is a diagram for explaining the influence of charging of a sample surface.

FIG. 4 is a diagram showing a relationship between electron beam irradiation energy and secondary electron emission efficiency η.

FIG. 5 is a flowchart illustrating an example of a method for manufacturing a semiconductor device.

FIG. 6 is a diagram schematically showing an example of a defect inspection apparatus using a plurality of primary electron beams.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inspection area 2 ... Small area 3 ... Scanning area corresponding to a small area 4 ... Scan instruction area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/66 H01L 21/66 J (72) Inventor Atsushi Onishi 8th Shin-Sugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock In-house Toshiba Semiconductor Company (72) Inventor: Mamoru Nakasuji, 11-1 Haneda Asahimachi, Ota-ku, Tokyo Ebara Meister Co., Ltd. (72) Inventor Tohru Satake 11-1, Asahimachi, Haneda, Ota-ku, Tokyo Ebara Corporation (72) Inventor Masanori Hatakeyama 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation (72) Inventor Toshifumi Kanma 11-1 Haneda Asahi-cho, Ota-ku, Tokyo F-term in Ebara Corporation ( 2F067 AA62 BB02 BB04 CC16 CC17 HH06 HH13 JJ05 KK04 LL16 2G001 AA03 BA07 CA03 DA01 DA09 EA04 FA01 FA08 GA04 GA05 GA06 HA13 KA03 KA20 LA11 MA05 SA 01 4M106 AA01 BA02 CA38 DB05 DB21 DJ18 DJ19 DJ20 5C033 UU02 UU04 UU05

Claims (5)

[Claims] 1. A defect inspection for detecting a secondary charged particle generated from an irradiation point when a charged particle beam is irradiated on a sample and performing a defect inspection of the sample in small area units obtained by dividing an inspection area of the sample. An apparatus for generating measurement image data of the small area based on the secondary charged particles; and detecting the charge based on errors at a plurality of specific points between the measurement image data and the reference image data. Image correction means for obtaining distortion correction data due to charging of the sample surface due to particle irradiation, and correcting the entire measurement image data to create corrected image data based on the distortion correction data; and Corrected image data of a small area of
Image comparison means for comparing the corrected image data of another sample and at least one image data of the reference image data for the entire image, and a defect inspection for detecting a defect of the sample based on an output of the image comparison means apparatus. 2. The defect inspection apparatus according to claim 1, wherein the plurality of specific points are selected from corners of a pattern included in the measurement image data and the reference image data. 3. A defect inspection for detecting a secondary charged particle generated from an irradiation point when a charged particle beam is irradiated on a sample, and performing a defect inspection of the sample in small area units obtained by dividing an inspection area of the sample. An apparatus, comprising: means for creating measurement image data based on the secondary charged particles, wherein the irradiation of the charged particle beam is instructed to irradiate an area wider than the small area, A defect inspection apparatus that detects a defect of a sample based on the measurement image data created for a wide area. 4. The defect inspection apparatus according to claim 1, wherein at least one or more primary optical systems for irradiating the sample with a plurality of primary charged particle beams, and the secondary charging. At least one or more secondary optical systems for guiding particles to at least one or more detectors, wherein the plurality of primary charged particle beams are applied to positions separated from each other by a distance resolution of the secondary optical system. Inspection equipment. 5. A device manufacturing method for performing a device defect inspection using the defect inspection device according to claim 1.