JP4104934B2 - Sample image measuring method and sample image measuring apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sample image length measuring method and a sample image length measuring apparatus used in a scanning electron microscope, a length measuring SEM, and the like that perform inspection, length measurement, and the like of semiconductor elements.
[0002]
[Prior art]
Conventionally, in the inspection of semiconductor elements, a pattern of a sample image has been measured using a scanning electron microscope, a length measuring SEM, etc. In the field of inspection of semiconductor elements, various sample image length measurements are performed. A method and a sample image length measuring apparatus have been proposed (see, for example, Japanese Patent Laid-Open Nos. 6-231715, 7-134965, and 2001-148016).
[0003]
Conventionally, for example, as shown in FIG. 1, in the case of a sample image having a plurality of patterns 1 having the same shape, a square reference image 2 for pattern matching as shown in FIG. 2 is prepared. In FIG. 2, 3 is a feature pattern shape portion, and O <b> 1 is a center position as an intersection of diagonal lines of the reference image 2.
[0004]
Then, as shown in FIG. 1, for example, the reference image 2 is shifted in the direction of the arrow, and it is determined that the pattern matching is performed at the position with the highest correlation coefficient, and the center position of the reference image 2 as shown in FIG. A measurement region 4 is set around a position O1 ′ corresponding to O1. Next, an arithmetic control means (not shown) measures the distance L1 of the contour line 5 of the pattern 1 within the measurement region 4.
[0005]
It should be noted that a known method is used for pattern matching, for example, masking is performed in areas other than the matching detection area.
[0006]
[Problems to be solved by the present invention]
By the way, the pattern 1 which approaches or leaves | separates may be formed depending on the pattern formation conditions of a pattern formation apparatus such as a stepper. FIG. 4 shows a case where adjacent patterns 1 are too close, and FIG. 5 shows a case where adjacent patterns 1 are too far apart.
[0007]
Thus, when the pattern 1 of the sample image is too close or too far away, accurate pattern matching cannot be performed even if pattern matching is performed using one reference image 2 shown in FIG. Originally, it is judged that the pattern is matched at a position different from the position to be matched, or the matching position cannot be detected at all.
[0008]
The present invention has been made in view of the above circumstances, and the object thereof is simple and quick even when there are variations in sample images obtained by pattern formation conditions of a pattern forming apparatus such as a stepper. Another object of the present invention is to provide a sample image length measuring method and a sample image length measuring apparatus capable of setting a measurement region by surely matching a plurality of reference images with a pattern of a sample image.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the sample image length measuring method according to claim 1 irradiates an electron beam on a sample, forms a sample image with charged particles generated from the sample, and obtains a pattern of the obtained sample image. In the sample image length measurement method to measure,
Prepare two reference images having different characteristic shapes extracted from the pattern, have row pattern matching for each of the sample images based on the two reference images prepared, one of which is determined by pattern matching In the position of the reference image and the position of the other reference image , set a measurement region for the pattern based on a point on a line segment connecting the specific point of the one reference image and the specific point of the other reference image , The length of the pattern of the sample image is measured in the measurement area.
[0010]
In order to solve the above-described problem , the sample image length measuring apparatus according to claim 2 irradiates the sample with an electron beam irradiating unit for irradiating the sample with an electron beam and an electron beam by the electron beam irradiating unit. Charged particle detection means for detecting charged particles generated at the time, and image processing means for measuring the pattern of the sample image obtained by forming the sample image based on the signal detected by the charged particle detection means In the sample image measuring device,
Storage means for storing two reference images having different characteristic shapes extracted from the pattern;
Pattern matching is performed on the sample image based on the two reference images, and the specific point of the one reference image and the other reference at the position of one reference image and the position of the other reference image determined by pattern matching. A calculation control means for setting a measurement region for the pattern with reference to a point on a line segment connecting a specific point of the image, and measuring the pattern of the sample image in the measurement region;
It is characterized by having .
[0011]
In order to solve the above problems, a sample image length measuring apparatus according to claim 3 is an electron beam irradiation means for irradiating an electron beam onto a sample in which a pattern having the same shape having symmetry is repeatedly present ; Charged particle detection means for detecting charged particles generated when the sample is irradiated with an electron beam by the beam irradiation means, and a sample image obtained by forming a sample image based on a signal detected by the charged particle detection means In a sample image length measuring apparatus having an image processing means for measuring the pattern of
Storage means for storing two rectangular reference images having a characteristic pattern shape portion formed corresponding to the shape of the portion constituting the symmetry of the pattern;
Performing pattern matching on the sample image based on the feature pattern shape part of the two reference images, and at the position of one reference image and the position of the other reference image determined by pattern matching, the center position of the one reference image and connecting the center position of the other of the reference image using the distance of the line segment to set the rectangular measurement region, an arithmetic control means for measuring the pattern of the sample image in the measurement region, that it has a Features.
[0012]
5. The sample image measuring apparatus according to claim 4, further comprising storage means for storing a reference image for magnification comparison with respect to the pattern of the sample image, wherein the calculation control means sequentially changes the magnification of the reference image for magnification comparison. Then, pattern matching with respect to the pattern of the sample image is performed, and the measurement region set for the reference image is changed in accordance with the magnification when the pattern of the sample image and the reference image for magnification comparison are matched. It is characterized by that.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the invention will be described with reference to the drawings.
[0014]
FIG. 6 shows the overall configuration of the sample image length measuring apparatus according to the present invention. Reference numeral 10 denotes a disk-shaped moving table on which a sample 11 such as a semiconductor wafer or chip is placed. This sample image length measuring apparatus is roughly composed of a scanning electron microscope 12, a host computer 13, and a monitor 14.
[0015]
A scanning electron microscope (electron microscope) 12 includes an electron gun 16, a condenser lens coil 17, an X-direction deflection coil 18, a Y-direction deflection coil 19, and a detector (charged particle detection means) 20 provided on the upper part of a lens barrel 15. The objective lens coil 21 is generally configured.
[0016]
The electron gun 16, the condenser lens coil 17, the X direction deflection coil 18, the Y direction deflection coil 19, and the objective lens coil 21 constitute an electron beam irradiation means, and the electron beam 16 a emitted from the electron gun 16 is converted into the condenser lens coil 17. The sample 11 is irradiated through the objective lens coil 21. Further, the electron beam 16 a is appropriately deflected by the X direction deflection coil 18 and the Y direction deflection coil 19.
[0017]
The secondary electron beam from the sample 11 generated by the electron beam 16a irradiation is detected by the detector 20, a detection signal is input to the host computer 13, and the host computer (image processing means) 13 outputs the detection signal. Image processing is appropriately performed, and the sample image is displayed on the monitor 14.
[0018]
The moving table 10 is installed in a sample chamber 22 in a vacuum state, and the moving table 10 is movable in the X direction and the Y direction orthogonal to each other. As shown in FIG. 7, the movement in the X direction and the Y direction is performed by the X direction actuator 23, the X direction feed screw 24, the X direction guide bar 25, the Y direction actuator 26, the Y direction feed screw 27, and the Y direction guide. This is done by bar 28. An X-direction actuator control circuit 29 and a Y-direction actuator control circuit 30 are connected to the X-direction actuator 23 and the Y-direction actuator 26, and an X-direction movement command value setting is set in the X-direction actuator control circuit 29 and the Y-direction actuator control circuit 30. A device 31 and a Y-direction movement command value setting device 32 are connected. Control signals from the host computer 13 are input to the X direction movement command value setter 31 and the Y direction movement command value setter 32.
[0019]
The movable table 10 is moved to a position to be measured, and irradiation of the charged particles to the visual field region 34 ′ to be measured, for example, in the case shown in FIG. As shown, the sample image 11 a is displayed in the display area 34 of the screen 14 </ b> A of the monitor 14.
[0020]
In FIG. 8, reference numeral 33 denotes a cursor, and reference numeral 35 denotes a pattern formed by repetition of the same shape of the sample image 11a. FIG. 9 is an explanatory diagram used for explaining the length measurement of the repeated pattern 35 having the same shape. The cursor 33 is used, for example, for specifying a length measurement target pattern.
[0021]
The host computer (arithmetic control means) 13 is connected to the storage means 13a. The storage means 13a has a feature pattern shape portion 35a of the repetitive pattern 35 as shown in FIGS. 9 (a) and 9 (b). , 35b, a square first reference image 36 and a square second reference image 37 are stored in advance. The reference images 36 and 37 are created when creating a procedure (recipe) for length measurement.
[0022]
In FIGS. 9A and 9B, O2 is the image center of the first reference image 36, and O3 is the image center of the second reference image.
[0023]
Next, as shown in FIG. 9C, pattern matching is performed on the first reference image 36 with respect to the repetitive pattern 35 of the sample image. Thereby, the position O2 ′ of the repetitive pattern 35 corresponding to the center position O2 of the first reference image 36 is determined. Further, pattern matching is performed on the second reference image 37 with respect to the repetitive pattern 35 of the sample image. Thereby, the position O3 ′ of the repetitive pattern 35 corresponding to the center position O3 of the second reference image 37 is determined.
[0024]
Next, the host computer 13 obtains a center position O4 ′ on the line segment L connecting the positions O2 ′ and O3 ′, and as shown in FIG. 9 (d), a rectangle having the center position O4 ′ as a diagonal center. A shape measurement area 38 is set.
[0025]
Then, the contour line 35a of the repetitive pattern 35 is detected in the measurement region 38, and for example, the shortest distance L1 from the contour line 35a to the contour line 35a is measured.
[0026]
In FIG. 9, the pattern matching for the horizontally long repetitive pattern 35 has been described. However, even in the case of the vertically long sample pattern 35, as shown in FIGS. 10 (a) and 10 (b), depending on the formation conditions of the pattern forming apparatus. Since the width of the repetitive pattern 35 of the sample image becomes thicker or narrower, when pattern matching is performed on the repetitive pattern 35 using one horizontally long reference image 39 shown in FIG. 10C, FIG. Although the pattern matching can be performed on the repetitive pattern 35 shown in FIG. 10, the pattern matching cannot be obtained on the wide repetitive pattern 35 as shown in FIG.
[0027]
Therefore, as shown in FIGS. 10D and 10E, a square first reference image 40 and second reference image 41 having sample image feature pattern shape portions 40a and 40b are prepared, and FIG. As shown in FIG. 10, pattern matching is performed, and based on the result, the measurement region 42 is set as shown in FIG. The method for obtaining the center position O4 ′ of the measurement region 42 may be the same as that described with reference to FIG. In FIG. 10C, 39a indicates a pattern shape portion.
[0028]
In the measurement, the outline 35a of the pattern 35 is detected by a plurality of scanning lines 43 within the measurement region 42, and the average value is obtained, for example.
[0029]
In the embodiment of the invention shown in FIG. 10, the case where the pattern matching is performed using the two reference images 41 and 42 shown in FIGS. 10D and 10E has been described, but one reference image 39 is used. When the pattern matching for the repeated pattern 35 is not obtained, the magnification of the reference image 39 is gradually changed, and this is repeated until the pattern matching is obtained. The measurement area may be changed at a magnification corresponding to the magnification.
[0030]
That is, the reference image 39 shown in FIG. 10C is used as a magnification comparison reference image, the magnification of the magnification comparison reference image is sequentially changed, pattern matching is performed on the pattern 35, and the pattern of the sample image and the magnification The measurement region 42 may be changed in correspondence with the magnification when the reference image for comparison is matched.
[0031]
FIG. 10 (h) shows an example in which pattern matching is performed by doubling the reference image 39 vertically and horizontally, and 39 ′ indicates a reference image enlarged twice. The measurement area 42 corresponding to the reference image 39 is doubled corresponding to the magnification. In FIG. 10I, the measurement area 42 shown in FIG. An example in which the measurement region 42 is doubled in the horizontal direction is shown.
[0032]
The reference image 39 is registered and stored in the storage means 13a when the recipe is created, and the host computer 13 changes the magnification and the like.
[0033]
Here, the pattern length measurement of the sample image 11a in which patterns having the same shape repeatedly exist has been described, but the present invention is not limited to this.
[0034]
【The invention's effect】
Since the present invention is configured as described above, for example, a sample on which a pattern that approaches or separates depending on the pattern forming conditions of a pattern forming apparatus such as a stepper is simple, quick, and The measurement region can be set surely by matching a plurality of reference images with the pattern of the sample image.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a sample image having a repeated pattern of the same shape.
FIG. 2 is a diagram showing an example of a reference image used for pattern matching of the sample image shown in FIG.
FIG. 3 is a diagram illustrating an example of a measurement region set based on pattern matching with respect to the sample image illustrated in FIG.
FIG. 4 is an explanatory diagram showing an example of a pattern obtained when charged particle irradiation conditions are different at the same magnification, and shows a case where adjacent patterns are too close to each other.
FIG. 5 is an explanatory diagram showing an example of patterns obtained when charged particle irradiation conditions are different at the same magnification, and shows a case where adjacent patterns are too far apart.
FIG. 6 is an overall configuration diagram of a sample image length measuring apparatus according to the present invention.
FIG. 7 is a plan view showing a structure of a moving table of the sample image length measuring apparatus according to the present invention.
FIG. 8 is an enlarged view showing a display area of a sample image displayed on the monitor screen of the sample image observation apparatus of the present invention at a magnification of 10,000 times.
FIGS. 9A and 9B are explanatory diagrams of a sample image measuring method according to the present invention, in which FIG. 9A shows a reference image set by extracting a characteristic pattern portion on the right side of the sample image, and FIG. 9B shows a sample image; The reference image which extracted and set the characteristic pattern part of the left side is shown, (c) is explanatory drawing in the case of performing pattern matching using the reference image shown in (a) and the reference image shown in (b) (D) is explanatory drawing which sets a measurement area | region based on the pattern matching.
FIGS. 10A and 10B are explanatory diagrams of another example of the sample image length measuring method of the present invention, in which FIG. 10A shows a vertically long pattern with a small lateral width obtained by charged particle irradiation, and FIG. 10B shows charged particle irradiation. (C) shows an example of one conventional reference image, and (d) shows a reference image set by extracting a characteristic pattern portion on the right side of the sample image. (E) shows a reference image set by extracting the characteristic pattern portion on the left side of the sample image, and (f) is an explanatory diagram when pattern matching is performed using the reference image shown in (e). (G) shows a measurement region set by pattern matching, (h) shows an example of performing pattern matching by doubling the reference image shown in (c), and (i) shows (j). An example in which the measurement area is set to be doubled horizontally is shown (j) Indicates a reference area set for the reference image shown in FIG.
[Explanation of symbols]
35 ... Patterns 36, 37 ... Reference image 38 ... Measurement area

Claims (4)

In a sample image length measurement method in which an electron beam is irradiated on a sample, a sample image is formed by charged particles generated from the sample, and a pattern of the obtained sample image is measured.
Prepare two reference images having different characteristic shapes extracted from the pattern, have row pattern matching for each of the sample images based on the two reference images prepared, one of which is determined by pattern matching In the position of the reference image and the position of the other reference image , set a measurement region for the pattern based on a point on a line segment connecting the specific point of the one reference image and the specific point of the other reference image , A sample image length measuring method comprising measuring a length of a sample image pattern in the measurement region. Electron beam irradiation means for irradiating a sample with an electron beam, charged particle detection means for detecting charged particles generated when the sample is irradiated with an electron beam, and the charged particle detection means In a sample image length measuring apparatus having image processing means for measuring a pattern of a sample image obtained by forming a sample image based on a signal detected by
Storage means for storing two reference images having different characteristic shapes extracted from the pattern;
Pattern matching is performed on the sample image based on the two reference images, and the specific point of the one reference image and the other reference at the position of one reference image and the position of the other reference image determined by pattern matching. A calculation control means for setting a measurement region for the pattern with reference to a point on a line segment connecting a specific point of the image, and measuring the pattern of the sample image in the measurement region;
A sample image length measuring apparatus comprising: Electron beam irradiating means for irradiating an electron beam on a sample having a symmetrical pattern of the same shape repeatedly, and detecting charged particles generated when the sample is irradiated with an electron beam A sample image length measuring apparatus comprising: a charged particle detection unit configured to perform measurement; and an image processing unit configured to measure a pattern of a sample image obtained by forming a sample image based on a signal detected by the charged particle detection unit.
Storage means for storing two rectangular reference images having a characteristic pattern shape portion formed corresponding to the shape of the portion constituting the symmetry of the pattern;
Performing pattern matching on the sample image based on the feature pattern shape part of the two reference images, and at the position of one reference image and the position of the other reference image determined by pattern matching, the center position of the one reference image A rectangular measurement region using the distance between the line segment connecting the center position of the other reference image and the calculation control means for measuring the length of the sample image pattern in the measurement region ;
A sample image length measuring apparatus comprising: Storage means for storing a reference image for magnification comparison with respect to the pattern of the sample image; and the arithmetic control means performs pattern matching with respect to the pattern of the sample image by sequentially changing the magnification of the reference image for magnification comparison. , to claim 2 or claim 3, characterized in that to change the measurement area set with respect to the reference image in correspondence with the magnification at which the pattern and the magnification comparison reference image of the sample image is matched The sample image length measuring apparatus described.

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