JP2000077323A - Method for detecting alignment mark in semiconductor- manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain absolute coordinates of the reference position of an alignment mark by using an image that is obtained so that a symmetrical alignment mark on a sample can be included and in image that is obtained by rotating the image, obtaining the reference position of the alignment mark, and creating a template image in reference to its position. SOLUTION: For acquiring an image for creating a template image, a deflector 13 is controlled to scan a region including a symmetrical alignment mark 18 such as a cross and a well curb being arranged on a wafer 19 with electron beams 12. Secondary electrons and reflection electrons being generated from a position on the wafer 19 where the electron beams 12 are applied due to irradiation with the electron beams are detected by an electron detector 16. The output of the electron detector 16 is amplified by an amplifier 14 and then inputted to an alignment mark detector 15 as image data. Then, in an image for forming a template image, the alignment mark position can be roughly obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of detecting a registration mark which is performed when a fine pattern is superimposed on a sample and drawn or exposed by using a semiconductor manufacturing apparatus such as an electron beam drawing apparatus or a light exposure apparatus. And a method of drawing or exposing a pattern using an alignment mark.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a fine pattern such as an element pattern or a circuit pattern is formed on a sample such as a semiconductor wafer using a fine pattern forming apparatus such as an electron beam lithography apparatus or a light exposure apparatus. Done. In forming these device patterns, it is necessary to form the pattern of the next layer with high precision with respect to the pattern already formed on the sample. Is used. In addition, in order to inspect whether a pattern formed on a semiconductor wafer or the like is as designed, dimensions of a predetermined portion of the pattern are measured using an electron microscope. An alignment mark is used to specify the measurement position. The alignment mark may be prepared on the sample as a dedicated mark separate from the device pattern, or a part of the device pattern may be used as the alignment mark.

As a registration mark detection method, an image corresponding to a registration mark on a sample is registered in advance as a template image, and a normalized correlation is obtained from a detected image obtained by electron beam scanning or optical imaging of the sample. There is a method called template matching for detecting the reference position of the alignment mark included in the template image by using. There is also a method of directly detecting an alignment mark from a detected image obtained by electron beam scanning or optical imaging of a sample without using a template image.

Japanese Patent Application Laid-Open No. 8-148402 discloses that a correlation operation is performed using a mark waveform obtained by scanning a mark to be detected with an electron beam and a mark waveform obtained by horizontally inverting the waveform. Describes a method of detecting a mark center position relatively from an extreme value position of the correlation function.

[0005]

FIG. 12 is an explanatory diagram of a template image extracted by a worker by a conventional method. The operator registers the template image T1 by arbitrarily cutting out an area corresponding to the alignment mark M1 from the image of the sample on the stage. In order to form a pattern on the sample held by the stage by electron beam drawing or exposure, the absolute position of the alignment mark M1 in the stage coordinates is required. However, in the conventional template matching method, the template image T
1 is registered by the operator by arbitrarily cutting out an area corresponding to the alignment mark M1 from the image of the sample on the stage. Therefore, the reference position of the alignment mark M1 with respect to the template image T1, for example, the coordinates (X _{p1) of} P1 , Y _p1 ) was not known, and the absolute position of the alignment mark M1 in the stage coordinates could not be known.

As a countermeasure, there is a method of detecting an alignment mark by forming an ideal template image T2 as shown in FIG. 13 based on a design value representing a feature of the shape of the alignment mark. In this method, the template image T2
At the time of creation, the reference position of the alignment mark M1 in the template image T2, for example, the coordinate of P1 is changed to, for example, (0,
0), the absolute position of the alignment mark in the stage coordinates can be known.

However, in the case of the template image T2 formed based on the design values, for example, the shape of the alignment mark and the step structure may be different for each process due to the influence of the semiconductor manufacturing process. FIG. 11 schematically shows this state. The alignment mark formed on the sample may be deformed by being processed in a semiconductor manufacturing process or the like.
Therefore, the image 110 of the alignment mark on the sample obtained by actual electron beam scanning or optical imaging is different from the alignment mark 111 of the template image formed based on the design value in shape and step structure. As a result, there were cases where accurate alignment marks could not be detected.

Further, in a method of directly detecting an alignment mark from a detected image obtained by electron beam scanning or optical imaging of a sample without using a template image, as far as the inventors know, the detected mark is not detected. There is no known method for determining the reference position of the alignment mark with high accuracy by image processing of a two-dimensional image. In the method described in Japanese Patent Application Laid-Open No. 8-148402, only the mark center position on the electron beam scanning line can be detected. Further, when the wafer on which the mark is formed is rotated, the peak position of the mark waveform obtained by scanning the mark with an electron beam with the rotation of the wafer is shifted, so that the center of the detected mark is shifted. The position also includes an error.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and can obtain absolute coordinates of a reference position of an alignment mark in a stage coordinate system.
It is an object of the present invention to provide a novel method that can correctly determine a reference position of an alignment mark without being affected by a semiconductor manufacturing process.

[0010]

According to the present invention, when a symmetrical alignment mark is arranged on a sample, an image obtained by including the alignment mark and an image obtained by rotating the image are used. Find the reference position of the alignment mark. Then, a template image is created based on the position, and the reference position of the alignment mark in the template image is known, thereby obtaining the absolute coordinates of the reference position of the alignment mark in the stage coordinate system. Similarly, the absolute coordinates of the reference position of the alignment mark in the stage coordinate system are obtained by directly obtaining the reference position of the alignment mark using the detected image obtained so as to include the alignment mark and the image obtained by rotating the image. .

[0011] The symmetric mark in this specification is a rotationally symmetric mark. The image of the sample including the alignment mark is
For example, in the case of an electron beam lithography apparatus, it is obtained by scanning an alignment mark formed on a sample with an electron beam, and in the case of a light exposure apparatus, an area of the sample including the alignment mark is optically imaged. Obtained by: That is,
An alignment mark detection method according to the present invention is a alignment mark detection method for detecting a symmetric alignment mark formed on a sample, wherein a step of acquiring a detected image including the alignment mark from the sample, Detecting the reference position of the alignment mark in the detected image using the rotated image.

The detected image does not necessarily need to completely include the entire alignment mark. For example, the position of a specific point on the detected image with respect to the alignment mark when the detected image is rotated is determined, and the midpoint between the two points before and after the movement is detected. Can be determined. Thus, what is directly obtained by the above-described image operation is the symmetric center position of the symmetrical alignment mark. The reference position of the alignment mark may be the position of this center of symmetry, or may be a position where a bias whose direction and length are known is applied to the center of symmetry. The reference position can also be detected using the detected image and a plurality of rotated images obtained by rotating the detected image at different angles.

According to another aspect of the present invention, there is provided an alignment mark detecting method for detecting an alignment mark formed on a sample using a template image, with reference to the reference position detected by the above-described alignment mark detection method. A template image is extracted from the detected image. The alignment mark detection method according to the present invention also includes a registration mark detection method for detecting an alignment mark formed on a sample, the method comprising: acquiring a detected image including the alignment mark from the sample; Among the evaluation values obtained when detecting the alignment mark from the detected image using the image of the partial area including the temporary region as the temporary template image, the tendency of the evaluation value at the pixel position at which the highest evaluation value is obtained and the pixel positions around the pixel position Estimating the reference position of the alignment mark in the detected image from the detected image, and detecting the reference position of the alignment mark with a resolution equal to or less than the pixel.
The image of the partial region of the detected image including the alignment mark does not necessarily need to completely include the entire alignment mark.

According to a second aspect of the present invention, there is provided an alignment mark detecting method for detecting an alignment mark formed on a sample using a template image, wherein the reference position of the alignment mark formed on the sample by the above-described method is determined. The detection is performed with a resolution equal to or less than the pixel, the reference position is rounded in pixel units, a template image is extracted based on the pixel including the reference position, and the rounded-down portion is held as a correction value, and the template image and the correction are stored. The reference position of the alignment mark formed on the sample is detected using the value. The correction value is used, for example, to supply a drawing control system as an offset at the time of drawing by the electron beam drawing apparatus to correct the drawing position, and to correct the offset of the result of the alignment mark detection.

According to the alignment mark detecting method of the present invention, in the alignment mark detecting method for detecting an alignment mark formed on a sample using a template image, the reference position of the alignment mark formed on the sample by the above-described method is determined. Detection is performed with a resolution equal to or less than the pixel, the detected image including the alignment mark is reacquired from the sample such that the reference position is the reference position of the template image, and the template image is extracted from the reacquired detected image. And

In the above-described alignment mark detection method, the reference position of the alignment mark is roughly determined before the reference position of the alignment mark is detected using a template image formed in advance based on the design value of the alignment mark. Is also good. Alternatively, determine the feature amount of the alignment mark,
By extracting a region including the feature amount from the detected image, the reference position of the alignment mark may be roughly determined before detecting the reference position of the alignment mark.

A pattern forming method according to the present invention is directed to a pattern forming method for forming a pattern on a sample using an electron beam lithography apparatus or a light exposure apparatus. Is detected, and a pattern is formed so as to have a predetermined positional relationship with the detected alignment mark.

According to the alignment mark detection method of the present invention, since the reference position of the alignment mark is obtained by rotating the image including the alignment mark, the electron beam is not affected by the variation in the shape of the alignment mark in each semiconductor manufacturing process. A reference position of an alignment mark in an absolute coordinate system in a device such as a drawing device can be detected with high accuracy. Further, by forming the template image based on the reference position detected with high accuracy, the reference position coordinates of the alignment mark in the template image can be known, so that the stage of the alignment mark detected using the template image You can know the absolute position in coordinates.

Also, among the evaluation values obtained when a mark is detected using an image to be detected, the evaluation value at a pixel position at which the highest evaluation value is obtained and the tendency of the evaluation values at pixel positions surrounding the pixel position are obtained. By estimating the position in the detected image that coincides with the reference position of the alignment mark, the reference position of the alignment mark can be obtained with a resolution equal to or less than the pixel unit, and highly accurate alignment mark detection becomes possible.

According to the present invention, the two-dimensional reference position of the alignment mark can be detected at once with high accuracy. Further, even if the wafer or the like on which the alignment mark is formed rotates, the reference position of the alignment mark can be detected with high accuracy without being affected by the rotation.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. Here, the detection of the alignment mark of the wafer in the electron beam lithography apparatus will be described. Also,
The description will be made on the assumption that the symmetry center of the alignment mark is the reference position. However, the description here is merely an example of the present invention, and is not intended to limit the present invention. For example, the reference position of the alignment mark can be any position that has a known relationship with the center of symmetry of the alignment mark.

FIG. 1 is a schematic diagram of an electron beam drawing apparatus for detecting the position of a registration mark according to the present invention. The electron beam 12 emitted from the electron gun 11 is deflected by a deflector 13, focused by a lens system (not shown), and irradiated on a wafer 19 held on a stage 20. The electron beam lithography apparatus includes an electron detector 16 and an amplifier 1 for amplifying an output of the electron detector 16 as a mechanism for detecting an alignment mark 18 provided on a wafer 19 as an image.
4. An alignment mark detector 15 is provided. The data of the alignment mark detected by the alignment mark detector 15 is supplied to the drawing control system 17 and used for electron beam drawing.

FIG. 2 is a flowchart for explaining the process of detecting the center position of the alignment mark for creating a template image according to the present invention. First, in step 210, an image for creating a template image is obtained. In obtaining an image for creating a template image, the deflector 13 is controlled to scan an area including a symmetrical alignment mark 18 such as a cross or a cross arranged on the wafer 19 by the electron beam 12. Secondary electrons and reflected electrons generated from the position on the wafer 19 irradiated with the electron beam 12 by the electron beam irradiation are detected by the electron detector 16. The output of the electronic detector 16 is amplified by the amplifier 14 and then input to the alignment mark detector 15 as image data. Before the output of the amplifier 14 is input to the alignment mark detector 15, a level setting is performed to adjust the contrast of an image and the like.

Next, in step 220, the position of the alignment mark is roughly determined in the image for forming the template image. In this step 220, after the reference position of the alignment mark is roughly determined, the size of the area around the alignment mark is set around step 23 around the result.
By performing the processing of 0, the processing time can be reduced and accurate detection can be performed regardless of the surrounding pattern. Step 220 is skipped and the process immediately proceeds to step 230.
It is also possible to perform processing for determining the center position of the alignment mark in the image for creating a template for the entire area of the image for creating the template image. The following two methods are examples of the method of performing step 220.

The first method is a method in which an ideal template image is formed in advance based on design values representing the characteristics of the shape of the alignment mark, and the center position of the alignment mark is narrowed down using the image. What is an ideal template image?
For example, the shape is determined by the mark width of the alignment mark and the vertical and horizontal sizes of the mark, and further, it is created by expressing the pixel values of the alignment mark and the background in a binary (multi-valued) manner. The narrowing of the center position of the alignment mark is obtained by, for example, normalized correlation.

The second method is to use the feature amount of the alignment mark. For example, the variance is used as the feature quantity, the size of the filter for obtaining the variance is set to about the size of the alignment mark, and this filter is moved by all pixels of the image for calculation. By moving the filter, the area of the alignment mark included in the filter changes. for that reason,
The larger the area including the alignment mark, the higher the dispersion value. By utilizing this, it is possible to narrow down the portion where the magnitude of the variance value is the highest as the center position of the alignment mark.

In addition to the variance, for example, a differential value, entropy, power spectrum, or the like may be used as the characteristic amount, or a plurality of characteristic amounts may be used in combination. In addition, after extracting only the alignment mark by using a threshold method or a shortest distance method based on a previously-provided teacher signal, an area having the size of the feature amount of the alignment mark is extracted.
The connected area extracted as the alignment mark is taken out, and the position of the center of gravity can be narrowed down as the center position of the alignment mark.

Next, a template image is created in step 230 of FIG. In the template image, it is necessary to find the center position of the alignment mark. As a method for performing this, there is a method shown in FIG. 4, for example, in the case of a rotationally symmetric alignment mark that overlaps when rotated 180 degrees such as a cross shape or a cross girder shape. FIG. 4 is a diagram illustrating an example of a method of determining the center position of the alignment mark 40 performed in step 230. The method shown in FIG. 4 will be described with reference to the flowchart in FIG. FIG.
The image 42 shown in (a) is an image for creating a template image, which is cut out based on the alignment mark position roughly obtained in step 220 of FIG. Step 5
In FIG. 4, an image 43 of a vertically and horizontally symmetrical area having a vertical and horizontal size A is extracted as shown in FIG. 4B around a center position 41 of an image 42 for creating a template image. Next, in step 520, the image 43 is
By rotating it by 0 degrees, a temporary template image 44 is created as shown in FIG.

Next, in step 530, the temporary template image 44 and the image 42 for creating the template image are subjected to template matching using normalized correlation or the like, and as shown in FIG. (Position corresponding to the center position of image 44 in image 42)
Get 45. Subsequently, in step 540, the obtained position 45 and the image 4 for creating the template image are set.
The midpoint between the center position 41 and the center position 2 is determined. The center point is the center position 46 of the alignment mark. In step 550, an area symmetrical in the vertical and horizontal directions around this position 46 is extracted and used as a template image.

Here, the center position 41 of the image 42 for creating the template image is moved to a position 45 by template matching between the temporary template image 44 based on the image rotated by 180 ° and the original image 42. And the midpoint 46 between the position 41 and the position 45 was determined as the center of symmetry of the alignment mark 40. However, image 42
Instead of the center position 41 of the image 42, focus on an arbitrary point included in the image 43 extracted from the image 42 or an arbitrary point having a known positional relationship with the image 43, and the point rotates the image 42 by 180 °. The template matching between the image 44 and the original image 42 detects where to move, and the midpoint before and after the movement of the point on the image 42 for creating the template image is the same as the symmetrical midpoint of the alignment mark. The result is obtained.

FIG. 6 is an explanatory diagram of another method for obtaining the center position of the alignment mark using the same image. First, FIG.
5A and 5B, the method of obtaining the alignment mark center position using the same image has been described. In the case where the alignment mark is a mark that is rotationally symmetric three or more times, such as a cross or a girder, FIG.
Is more resistant to noise than the above-described method of rotating the image by 180 degrees, and it is a method of easily verifying whether the center position of the alignment mark is correctly obtained. This method will be described with reference to the flowchart shown in FIG.

In step 710 of FIG. 7, an image having a vertical and horizontal size A is extracted from the center position 61 of the image 60 for creating a template image. Next, step 7
At 20, a temporary template image 62 obtained by rotating the image by 90 ° is created. In the following step 730, the created provisional template image 62 and the image 60 for creating the template image are subjected to template matching using normalized correlation or the like, and in step 740, the position D1 at which the best match is obtained. The processing of steps 720 to 740 is repeated three times, and matching positions D2 and D3 when the images rotated 180 ° and the images rotated 270 ° are provisional template images 63 and 64, respectively, are obtained. Next, the process proceeds from step 750 to step 760, in which four center-of-gravity positions 65 including the obtained three detection positions D1 to D3 and the center position 61 of the image 60 for creating the template image are obtained. In step 770, the position of the center of gravity 65
A region symmetrical in the vertical and horizontal directions with respect to is extracted to create a template image.

In this method, since three alignment marks are detected by one imaging of the alignment mark, the method shown in FIG.
Compared with the method of rotating by 0 degrees, there is an effect that the alignment mark center position that is strong against image noise can be detected while making the imaging time equal. Further, the center position 6 of the image 60
1 and the detection positions D1 to D3 form a square when the alignment mark detection is accurately performed, so that it is determined whether the alignment mark center position 65 has been correctly obtained.
It can be verified by the square shape formed by the points 61 and D1 to D3.

Here, the center position 61 of the image 60 for creating the template image is 90 °,
The template matching between the tentative template images 62, 63, 64 based on the images rotated by 180 ° and 270 ° and the original image 60 is detected as moving to positions D1, D2, and D3, and their center of gravity position 65 is determined. It was determined as the center of symmetry of the alignment mark. However, the center position 61 of the image 60
Instead of focusing on an arbitrary point included in the image extracted from the image 60 or an arbitrary point having a known positional relationship with the extracted image, the point is used as the temporary template image 6.
The same result can be obtained by detecting where to move by template matching between 2, 63, 64 and the original image 60 and setting their centers of gravity as the symmetric midpoints of the alignment marks.

Now, return to FIG. By the way, as the center position of the alignment mark, a resolution of a sub-pixel unit or less is required for the accuracy of drawing or exposure. However, FIG.
In the method described with reference to FIGS. 4 to 7 regarding the step 230, the center position of the alignment mark can be obtained only with the resolution of the pixel unit. On the other hand, for example, an area including an alignment mark is extracted from an image for creating a template image, and the extracted area is used as a temporary template image. The temporary template image is used, and a correlation value is adopted as an evaluation value. When template matching is performed with an image for creating the matching mark, the correlation value becomes maximum at the alignment mark center position and decreases as the distance from the alignment mark center position increases, as shown in FIG. Therefore, in step 240 of FIG. 2, the center position of the alignment mark is obtained at a resolution of sub-pixel or less using this method.
Here, template matching is performed on the pixel including the center position of the alignment mark obtained in step 230 and the surrounding pixels using a temporary template image including an area including the alignment mark, as shown in FIG. The evaluation value is obtained as follows. Among the evaluation values thus obtained, a change in the evaluation values is obtained from the plurality of evaluation values obtained at the pixel position B0 having the highest evaluation value as the center position of the alignment mark and the surrounding pixel positions Bi. Is approximated by, for example, a two-dimensional quadratic expression in the X-axis direction and the Y-axis direction at the same time, and from the approximate expression, a position at which the evaluation value is maximum is obtained, and this is estimated as the center position of the alignment mark. Thus, the center position of the alignment mark is obtained with a resolution of a subpixel unit or less.
In addition, the approximation formula includes various orders other than a two-dimensional quadratic formula, a formula of another order, a method of separately approximating the X-axis direction and the Y-axis direction in one dimension, a method of approximating by a spline, and the like. It is conceivable, and any of those methods may be used.

In the next step 250, step 240
The template image is extracted from the image for creating the template image with reference to the center position of the alignment mark expressed with the resolution equal to or less than the sub-pixel unit obtained by the above. Step 2 in extracting the template image
Using the integer part of the result obtained in step 40, the center position 105 of the alignment mark is rounded in pixel units as shown in FIG.
An image is extracted symmetrically up, down, left and right around pixel position 101 of 00 to form a template image. The residual 106 due to the decimal part is stored and held as a correction value, and this correction value is used for applying feedback as an offset at the time of pattern drawing or for correcting the alignment mark detection result. Alternatively, similarly, after determining the center position 105 of the alignment mark at a resolution of sub-pixel unit or less, the stage 20 is adjusted so that the position becomes the center pixel position of the image for creating the template image.
May be moved to re-image the alignment mark 18, and a vertically symmetrical area may be extracted from the center position of the image for creating the template image to form the final template image.

When a template image with a known position of the alignment mark is obtained by the processing from step 210 to step 250, the process proceeds to step 260 to perform mark detection using the template image. Step 2
The template images formed in 10 to 250 are held by the alignment mark detector 15, and when performing mark detection, the alignment mark to be detected is scanned, and a signal obtained therefrom is detected as an image to be detected. Input to the container 15. After that, for the template image and the detected image, for example, normalized correlation is performed to perform alignment mark detection. The process of step 260 is repeated until it is determined in step 270 that detection of all alignment marks has been completed. When the alignment mark is detected on the next wafer, the template images held in the alignment mark detector 15 are used to perform steps 210 to 25.
0 may be omitted, and only the processing of steps 260 to 270 may be performed.

The method of forming a template image whose alignment mark position is known from an image acquired to create a template image has been described above. By the way, an image for creating a template image described above, a method of detecting an alignment mark by rotating the same image as the image, and a method of approximating a plurality of evaluation values to determine the center position of the alignment mark in sub-pixel units The method of obtaining with the following resolution is not only for obtaining the center position of the alignment mark to form the template image as described above, but also for directly detecting the center position of the alignment mark for drawing and exposure. It is also possible to use it.

The basic processing in this case is as shown in the flowchart of FIG. That is, first, in step 310, a detected image on which alignment marks are detected is acquired. Specifically, an alignment mark to be detected is scanned, and a signal obtained therefrom is input to the alignment mark detector 15 as a detected image. Next, in step 320, the position of the alignment mark is roughly determined in the detected image, and in step 330, the position of the alignment mark in the detected image is determined. Next, in step 340, the position of the alignment mark in the detected image is determined with a resolution of a pixel or less. This process is repeated until it is determined in step 350 that detection of all marks has been completed.

Steps 310, 320, 330,
340 are steps 210, 220, 2 in FIG.
The same processing as in the case of FIG. Step 330 is similarly performed according to the flowchart shown in detail in FIG. 5 or FIG.
However, when the center position of the alignment mark is detected for drawing or exposure, the process of step 550 in FIG.
Step 770 is excluded. The specific processing method in each step is the same as that in the case of creating a template image, and a description thereof will be omitted.

The case where the present invention is applied to the detection of alignment marks on a wafer in an electron beam lithography apparatus has been described above. However, the application of the present invention is not limited to the detection of alignment marks in an electron beam lithography apparatus. For example, the present invention can of course be applied to the detection of alignment marks in a light exposure apparatus schematically shown in FIG. The light exposure apparatus projects and exposes an image of a reticle 1402 illuminated with exposure light from a light source 1401 onto a substrate (sample) 1404 such as a semiconductor wafer coated with a photosensitive material such as a photoresist by a projection optical system 1403. It is.

The substrate 1404 is held by a moving stage 1405, and the moving stage 1405 is precisely controlled so that the exposure area of the substrate 1404 exactly matches the projection area of the reticle 1402. An alignment mark 1406 is formed on the substrate 1404, and the position of the alignment mark 1406 is determined by using the substrate alignment microscope 1411,
The movement stage 1405 is controlled by detection by an alignment optical system including an imaging device 1414 such as a CCD camera. Alignment mark 140 on substrate 1404
6 is a substrate alignment microscope 1411, a mirror 141
2. Image data is captured by the imaging device 1414 via the relay lens 1413, and image data output from the imaging device is supplied to the alignment mark detector 1415. The alignment mark detector 1415 performs the same processing as that described above in relation to the electron beam lithography apparatus to perform the alignment mark 1406.
The stage control system 1416 controls the stage driving unit 1417 based on the detection result, and
404 is aligned.

In addition to the above-described electron beam lithography apparatus and light exposure apparatus, an apparatus which needs to detect an alignment mark, for example, dimensional measurement of a position specified on a pattern formed on a wafer with reference to the alignment mark The present invention can be similarly applied to an electron beam image, an ion beam image, an X-ray image, and the like in a scanning electron microscope, a transmission electron microscope, or a focused ion beam processing apparatus for performing fine processing. It is possible.

[0044]

According to the present invention, it is possible to detect a reference position of an alignment mark with high accuracy in an absolute coordinate system in the apparatus without being affected by variations in the shape of the alignment mark due to a semiconductor manufacturing process. Further, since the reference position of the alignment mark can be obtained with a resolution of a pixel unit or less, highly accurate alignment mark detection can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic view of an electron beam drawing apparatus.

FIG. 2 is a detection flowchart of a registration mark center position for creating a template image.

FIG. 3 is a flowchart for detecting a center position of an alignment mark for drawing (exposure) and the like.

FIG. 4 is an explanatory diagram of an example of a method for obtaining a center position of an alignment mark.

FIG. 5 is a flowchart of an example of a method for obtaining a center position of an alignment mark.

FIG. 6 is an explanatory diagram of another example of a method for obtaining the center position of the alignment mark.

FIG. 7 is a flowchart of another example of a method for obtaining a center position of an alignment mark.

FIG. 8 is a diagram showing an example of a tendency of a correlation value.

FIG. 9 is an explanatory diagram for obtaining a center position of an alignment mark at a resolution of a pixel unit or less.

FIG. 10 is an explanatory diagram of a residual generated when the center position of the alignment mark is rounded in pixel units.

FIG. 11 is an explanatory diagram of alignment marks created based on design values and actual alignment marks.

FIG. 12 is an explanatory diagram of a template extracted by an operator.

FIG. 13 is an explanatory diagram of a template created based on design values.

FIG. 14 is a schematic view of a light exposure apparatus.

[Explanation of symbols]

11 electron gun, 12 electron beam, 13 deflector, 14 amplifier, 15 alignment mark detector, 16 electron detector,
17: Drawing control system, 18: alignment mark, 19: wafer, 20: stage, 40: alignment mark, 41: central position of image, 42: image or detected image for creating template image, 43: central position , A region extracted symmetrically from top to bottom, left and right, 44... A temporary template image, 45.
The most matched position, 46... The mark center position, 60... An image or a detected image for creating a template image,
61: Center position of image, 62 to 64: Temporary template image, 65: Center of gravity position, 100: Pixel including mark center position, 101: Pixel position, 105: Mark center position, 106: Rounding error, 110: Actual Alignment mark, 111 Alignment mark created based on design values, 1401 illuminant, 1402 reticle, 1403…
Projection optical system, 1404 substrate, 1405 moving stage, 1406 alignment mark, 1411 substrate alignment microscope, 1412 mirror, 1413 relay lens, 1414 imaging device, 1415 alignment mark detector, 1416 stage control system , 1417: stage drive system, T1, T2: template image, M1, M2: alignment mark, P1: center position of alignment mark

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuki Onuki 882-mo, Oaza-shi, Hitachinaka-city, Ibaraki Pref. Inside the Measuring Instruments Division, Hitachi, Ltd. 5F046 AA26 DB05 EA02 EB01 ED01 FC06 5F056 BD02 BD05 CC10 FA06

Claims (9)

[Claims] 1. A method for detecting a symmetrical alignment mark formed on a sample, the method comprising: acquiring a detected image including the alignment mark from the sample; rotating the detected image and the detected image. Detecting the reference position of the alignment mark in the detected image using the rotated image. 2. The alignment mark detection method according to claim 1, wherein the reference position is detected using the detected image and a plurality of rotation images obtained by rotating the detected image at different angles. Alignment mark detection method. 3. A registration mark detection method for detecting a registration mark formed on a sample using a template image, wherein the detected image is detected based on a reference position detected by the registration mark detection method according to claim 1 or 2. A matching mark detection method, wherein a template image is extracted from the image. 4. A registration mark detection method for detecting a registration mark formed on a sample, wherein a step of obtaining a detection image including the registration mark from the sample includes a step of obtaining a partial area including the registration mark in the detection image. From the evaluation values obtained when detecting the alignment mark from the detected image using the image as a temporary template image, from the tendency of the evaluation value at the pixel position where the highest evaluation value is obtained and the surrounding pixel positions, Estimating the reference position of the alignment mark in the detected image, and detecting the reference position of the alignment mark at a resolution of not more than a pixel. 5. A registration mark detecting method for detecting a registration mark formed on a sample by using a template image, wherein the reference position of the registration mark formed on the sample by the registration mark detection method according to claim 4 is set to a pixel or less. Detected at a resolution, the reference position is rounded in pixel units, a template image is extracted based on the pixel including the reference position, and a portion rounded off by rounding is held as a correction value, and the template image and the correction value are stored. A method for detecting a reference position of an alignment mark formed on a sample using the method. 6. A registration mark detection method for detecting a registration mark formed on a sample by using a template image, wherein the reference position of the registration mark formed on the sample by the registration mark detection method according to claim 4 is set to a pixel or less. Detecting at a resolution, re-acquiring a detected image including the alignment mark from the sample such that the reference position becomes the reference position of the template image, and extracting a template image from the re-acquired detected image. Alignment mark detection method. 7. The alignment mark detection method according to claim 1, wherein a reference position of the alignment mark is detected using a template image formed in advance based on a design value of the alignment mark. A registration mark detection method, wherein a reference position of the registration mark is roughly determined. 8. The alignment mark detection method according to claim 1, wherein a characteristic amount of the alignment mark is obtained, and a region including the characteristic amount is extracted from the detected image. Before detecting the reference position of the alignment mark, the reference position of the alignment mark is roughly determined. 9. A pattern forming method for forming a pattern on a sample using an electron beam drawing apparatus or a light exposure apparatus,
A method of detecting a registration mark of a sample by the registration mark detection method according to any one of claims 1 to 8, and performing pattern formation such that the detected registration mark has a predetermined positional relationship. Pattern forming method.