JPH11345867A - Method and device for determining rotating direction of wafer and wafer measuring position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the accurate measuring point of a wafer, by determining the candidate of the wafer reference direction from the multiplicity of rotational symmetry, setting one candidate direction selected when the multiplicity is 1 as the reference direction, performing matching process by using the template image when the multiplicity is 2 or more and specifying the one adequate reference direction. SOLUTION: The image to be processed received by a rotating-direction limiting means 150 and a pattern-matching means 154 and a reference-lamp rate image are used, and a reference candidate point which becomes the reference point of a wafer to be measured is obtained. When the reference template image without rotational symmetry wherein the multiplicity (n) of the rotational symmetry is 1 is used, the selected one candidate direction is specified as the reference direction. When the reference plate image having the rotational symmetry wherein (n) is 2 or more is used, the number of the rotational plates of image (360 deg./10 deg./n) used in pattern matching is limited. Then, one adequate reference direction is specified from a plurality of the candidates by the pattern matching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for determining a measurement position on a wafer.

[0002]

2. Description of the Related Art A semiconductor wafer is measured by various measuring devices in a manufacturing process. During the measurement process, a “positioning process (alignment process)” for accurately positioning a measurement probe (optical element, electrode, or the like) at a predetermined measurement point on the wafer is performed.

[0003]

However, when a wafer is set on a measuring apparatus, the orientation (wafer rotation direction) and position (center position of the wafer) of the wafer relative to the measuring system of the measuring apparatus are always in a fixed state. In this case, there is a problem that the coordinates of the measurement points on the wafer have different values for each wafer.

The present invention has been made to solve such a problem in the prior art, and has as its first object to provide a technique capable of determining the orientation of a wafer. It is a second object of the present invention to provide a technique capable of determining an accurate measurement point on a wafer by specifying the direction and position of the wafer.

[0005]

In order to solve at least a part of the above-described problems, a first method of the present invention is a method for determining a rotation direction of a wafer held by a wafer holding unit. (A) a first, which exists near a first predetermined position on the wafer and has rotational symmetry,
(B) preparing in advance a first template image including the reference pattern of (1) and rotational symmetry information indicating the number n of rotational symmetries of the first reference pattern; and (b) a second predetermined pattern on the wafer. Preparing in advance a second template image including a second reference pattern existing near the position;
(C) capturing a first processing target image near the first predetermined position on the wafer while being held by the wafer holding unit; and (d) capturing a first processing target image within the first processing target image. Determining a direction of a matching image that matches the first template image; and (e) determining n candidate directions as reference directions of the wafer from the direction of the matching image and the rotational symmetry information. Process and
(F) When the number of times of rotational symmetry n is 1, the candidate direction is selected as the reference direction. When the number of times of rotational symmetry n is 2 or more, the candidate direction is selected from the n candidate directions. Estimating the second predetermined position on the wafer, capturing a second processing target image near the estimated second predetermined position, and extracting the second template image with respect to the second processing target image Selecting one appropriate direction as the reference direction from the n candidate directions by performing the used pattern matching.

In the above-described method of determining the rotation direction of the wafer, the first template image including the first reference pattern that can limit the direction in which the second reference pattern indicating the reference direction of the wafer exists is used. Pattern matching is performed with the first processing target image. From the result of the pattern matching, n candidate directions of the wafer reference direction can be selected, and in step (f), one of the n candidate directions is selected from the n candidate directions according to the rotational symmetry information of the first template image. Candidate directions can be specified. That is, when the number of times of the rotational symmetry of the first template image is 1, one selected candidate direction can be specified as the reference direction. When n is 2 or more, pattern matching is performed using the second template image in some regions estimated to include the second reference pattern from the plurality of selected candidate directions. One reference direction can be specified based on the result of the matching. This makes it possible to accurately determine the rotation direction on the wafer held by the wafer holding unit.

In the above-described method of determining the rotation direction of a wafer, the first predetermined position is a center position of the wafer, the second predetermined position is a position on an outer edge of the wafer, and the second predetermined position is a position on an outer edge of the wafer. Is preferably a notch formed at the outer edge of the wafer.

As described above, if the center position of the wafer is set to the first predetermined position, the first reference pattern can be easily determined, and the first processing target image can be easily formed in the step (c). It is possible to take an image. Furthermore, the second
If the notch formed at the second predetermined position on the outer edge of the wafer is adopted as the reference pattern, the rotation direction of the wafer can be easily specified.

A first apparatus of the present invention is an apparatus for determining a rotation direction of a wafer, wherein the position of the wafer in a plane parallel to the surface of the wafer can be held within a predetermined error range. A holding unit, an imaging unit that captures an image on the wafer held by the wafer holding unit, and a first reference pattern that is present near a first predetermined position on the wafer and has rotational symmetry. Including the first template image and the number n of rotational symmetries of the first reference pattern
And a second template image including a second reference pattern present in the vicinity of a second predetermined position on the wafer, and a memory for storing the first symmetry information on the wafer. A pattern matching unit that determines a direction of a matching image that matches the first template image in a first processing target image captured in the vicinity of a predetermined position; A candidate direction determining unit for determining n candidate directions as a reference direction of the wafer; and selecting the candidate direction as the reference direction when the number of times of rotational symmetry n is one, When the number of times n is 2 or more, the second position on the wafer is determined from the n candidate directions.
By performing pattern matching using the second template image on a second processing target image captured in the vicinity of the estimated second predetermined position, thereby obtaining the n candidates. A reference direction determining unit that selects one appropriate direction as the reference direction from the directions.

In the above-described apparatus for determining the rotation direction of a wafer, since the wafer holding section capable of holding the wafer within a predetermined error range is provided, a desired position of the wafer can be easily imaged by the imaging section. . If such an apparatus is used, an accurate rotation direction on the wafer can be determined in the same manner as in the first method. That is, the pattern matching unit uses the first template image including the first reference pattern, which can limit the direction in which the second reference pattern indicating the reference direction of the wafer exists, to the first processing target image on the wafer and Perform pattern matching. From the result of the pattern matching, the candidate direction determining unit can select n candidate directions as the reference direction of the wafer. Further, the reference direction determination unit can specify one candidate direction from the n candidate directions according to the rotational symmetry information of the first template image.

In the above-described apparatus for determining the direction of rotation of a wafer, the first predetermined position is a center position of the wafer, the second predetermined position is a position on an outer edge of the wafer, and the second predetermined position is a position on an outer edge of the wafer. Is preferably a notch formed at the outer edge of the wafer.

As described above, when the center position of the wafer is set to the first predetermined position, the first reference pattern can be easily determined, and the first processing target image can be easily captured by the imaging unit. Becomes possible. Furthermore, if the notch formed at the second predetermined position on the outer edge of the wafer is adopted as the second reference pattern, the rotation direction of the wafer can be easily specified by the reference direction determination unit.

A second method according to the present invention is a method for determining the position of a measurement point on a wafer to be measured held by a wafer holding unit, wherein: (a) a first predetermined position on the wafer to be measured; A first template image including a first reference pattern having a rotational symmetry in the vicinity of the first reference pattern, rotational symmetry information indicating the number n of rotational symmetries of the first reference pattern, Reference point position information indicating the positional relationship between the position of the first reference pattern and a predetermined reference point on the measured wafer, and measurement point position information indicating the position of the measurement point on the measured wafer, (B) preparing in advance a second template image including a second reference pattern existing near a second predetermined position on the wafer to be measured; and (c) preparing the wafer State held by holding part Capturing a first processing target image in the vicinity of the first predetermined position on the wafer to be measured, and (d) matching matching with the first template image in the first processing target image Determining a position and a direction of an image; and (e) determining n candidate directions as a reference direction of the measured wafer from the direction of the matching image and the rotational symmetry information;
(F) When the number of times of rotational symmetry n is 1, the candidate direction is selected as the reference direction. When the number of times of rotational symmetry n is 2 or more, the position of the matching image and the n number of times are selected. And estimating the second predetermined position on the wafer to be measured from the candidate direction, capturing a second processing target image in the vicinity of the estimated second predetermined position,
By performing pattern matching using the second template image for the processing target image,
Selecting one suitable direction as the reference direction from among the candidate directions; (g) the reference direction determined in step (f) and the matching determined in step (d) Determining a position of the reference point of the wafer to be measured in a state held by the wafer holding unit from the image position and the reference position information; and (h) determining the position of the reference point in the step (f). From the reference direction, the position of the reference point determined in the step (g), and the measurement point position information, the position of the measurement point on the wafer to be measured in a state held by the wafer holding unit And determining the following.

In the above-described method for determining a measurement position of a wafer, a wafer to be measured is determined by using a first template image including a first reference pattern that can limit a direction in which a second reference pattern indicating a reference direction of the wafer exists. Is subjected to pattern matching with the first image to be processed. From the result of the pattern matching, n candidate directions of the reference direction of the wafer to be measured can be selected, and in the step (f), from the n candidate directions according to the rotational symmetry information of the first template image. One candidate direction can be specified. That is, when the number of times of the rotational symmetry of the first template image is 1, one selected candidate direction can be specified as the reference direction. When n is 2 or more,
In some regions estimated to include the second reference pattern from the selected plurality of candidate directions, pattern matching is performed using the second template image, and one reference direction is determined based on the result of the pattern matching. Can be identified. Since the reference point can be determined in the step (g) based on the reference direction specified in this way, it is possible to accurately determine the measurement point on the measured wafer held by the wafer holding unit. Become.

In the above-described method for determining a measurement position of a wafer, the first predetermined position is a center position of the wafer to be measured, and the second predetermined position is a position on an outer edge of the wafer to be measured. Preferably, the second reference pattern is a notch formed at an outer edge of the wafer to be measured.

A second apparatus of the present invention is an apparatus for determining a position of a measurement point on a wafer to be measured, wherein the position of the wafer to be measured in a plane parallel to the surface of the wafer to be measured is predetermined. A wafer holding unit that can be held within an error range of: an imaging unit that captures an image on the wafer to be measured held by the wafer holding unit; and an imaging unit that is located near a first predetermined position on the wafer to be measured. The first with rotational symmetry
A first template image including the reference pattern, rotational symmetry information indicating the number of times n of rotational symmetry of the first reference pattern, a position of the first reference pattern on the wafer to be measured, and the measurement target. Reference point position information indicating a positional relationship with a predetermined reference point on the wafer, measurement point position information indicating a position of the measurement point on the measured wafer, and a vicinity of a second predetermined position on the measured wafer The second that exists in
A second template image including a reference pattern of the first and second patterns, and a first template image in a first processing target image captured in the vicinity of the first predetermined position on the wafer to be measured. A pattern matching unit that determines a position and a direction of a matching image that matches the direction of the matching image, and a candidate direction that determines n candidate directions as a reference direction of the measured wafer from the direction of the matching image and the rotational symmetry information A determining unit, and the number n of times of the rotational symmetry
Is 1, the candidate direction is selected as the reference direction. On the other hand, when the number of times of rotational symmetry n is 2 or more, the candidate direction is selected from the position of the matching image and the n candidate directions. The second predetermined position on the wafer to be measured is estimated, and pattern matching using the second template image is performed on a second processing target image captured near the estimated second predetermined position. Thus, a reference direction determining unit that selects an appropriate one of the n candidate directions as the reference direction, the reference direction determined by the reference direction determining unit, and a reference direction determined by the pattern matching unit A reference position for determining a position of the reference point of the measured wafer in a state held by the wafer holding unit from the position of the matched image thus obtained and the reference position information Fixed part, the reference direction determined by the reference direction determination part, the position of the reference point determined by the reference position determination part, and the measurement point position information, which is held by the wafer holding part. A measurement position determining unit that determines the position of the measurement point on the measurement target wafer in the state.

Since the above-described wafer measurement position determining apparatus includes a wafer holding unit capable of holding the measured wafer within a predetermined error range, the desired position of the measured wafer can be easily imaged by the imaging unit. can do. By using such an apparatus, it is possible to determine an accurate measurement point on the wafer as in the second method. That is, the pattern matching unit uses the first template image including the first reference pattern that can limit the direction in which the second reference pattern indicating the reference direction of the wafer exists, and performs processing on the first processing target on the wafer to be measured. Perform image and pattern matching. From the result of the pattern matching, the candidate direction determining unit can select n candidate directions of the reference direction of the measured wafer. Further, the reference direction determination unit can specify one candidate direction from the n candidate directions according to the rotational symmetry information of the first template image. Since the reference position determination unit can determine the reference point based on the specified reference direction, the measurement position determination unit accurately determines the measurement point on the measurement target wafer held by the wafer holding unit. It becomes possible.

In the above-mentioned apparatus for determining a measurement position of a wafer, the first predetermined position is a center position of the wafer to be measured, and the second predetermined position is a position on an outer edge of the wafer to be measured. Wherein the second reference pattern is
Preferably, the notch is formed at an outer edge of the wafer to be measured.

[0019]

Other Embodiments of the Invention The present invention includes the following embodiments. A first aspect is a recording medium that records a computer program that causes a computer to execute the functions of each step or each means of the above invention. Examples of the recording medium include a computer-readable portable storage medium such as a flexible disk and a CD-ROM, an internal storage device (memory such as RAM and ROM) and an external storage device of a computer system, or a computer other than the above. Various media on which a program is recorded and which can be read by a computer system can be used.

According to a second aspect, there is provided a program supply device for supplying, via a communication path, a computer program for causing a computer to execute the functions of each step or each means of the above invention.

[0021]

DETAILED DESCRIPTION OF THE INVENTION Configuration of Apparatus: Next, an embodiment of the present invention will be described based on examples. FIG. 1 is an explanatory view showing a wafer measurement position determining apparatus according to the present invention. The present wafer measurement position determination device has a function of performing a semiconductor wafer alignment process (alignment process).
This apparatus includes a control operation unit 30 and a wafer holding unit 1.
00, a frame 110, an Rθ stage 130, and an optical unit 140 as an imaging optical system.

The wafer holding unit 100 has a lower surface 100u
Is provided with a suction surface having a large number of suction holes, and the wafer W
It has a function to hold F by vacuum suction. The lower surface 100u of the wafer holding unit 100 is provided with a circular guide ring 102 slightly larger than the wafer WF.
With this guide ring 102, the center of the wafer WF is
It is held substantially at the center of the wafer holding unit 100. The wafer holding unit 100 can be moved up and down by a holding control unit (not shown).

The frame 110 has a function of positioning the wafer holder 100 such that the center of the field of view is substantially at the center of the lower surface 100u of the wafer holder 100 at the initial position of the optical unit 140 (the center position of the Rθ stage). Have. The frame 110 has a substantially cylindrical shape, and has a movable positioning portion 120 for positioning the wafer holding portion 100 at an upper portion thereof. The positioning unit 120 is located at the center axis 100 a of the wafer holding unit 100.
A central axis adjusting mechanism 121 for arranging the wafer within a certain error range from the central axis of the frame 110, and a parallelism adjusting mechanism 122 for keeping the lower surface 100u of the wafer holding unit 100 almost perpendicular to the Z-axis direction. Have. The center axis adjusting mechanism 121 has a ring shape having a diameter slightly larger than the outer shape of the wafer holding unit 100. If the wafer holder 100 is arranged inside the center axis adjusting mechanism 121, it can be automatically arranged within a certain error range. The parallelism adjusting mechanism 122 is connected to the lower surface 10 of the wafer holder.
It has a ring-like shape having a diameter larger than that of the guide ring 102 provided at 0u and smaller than that of the wafer holding unit 100. Since the parallelism adjusting mechanism 122 supports the wafer holding unit 100 from the lower surface side, the lower surface 100u of the wafer holding unit 100 can be arranged substantially perpendicular to the Z-axis direction.

FIG. 2 is an explanatory diagram showing the operation of the positioning unit 120. When the wafer holding unit 100 is lowered, first, as shown in FIG. 2A, the wafer holding unit 100 comes into contact with the parallelism adjustment mechanism 122, and the lower surface 100u of the wafer holding unit 100 is arranged substantially perpendicular to the Z-axis direction. Is done. Next, as shown in FIG. 2B, the positioning unit 120 is moved toward the central axis of the frame 110 so that the central axis 100a of the wafer holding unit 100 is within a certain error range from the central axis of the frame 110. Can be placed within. This positioning error range is sufficiently smaller than the field of view of the optical unit 140 (for example, 1/1 of the short side of the field of view).
0 or less), for example, it is preferably set to about 1 mm or less. Note that this frame 110
Is composed of three partial positioning portions 120a to 120c as shown in the plan view of FIG. Thus, the frame 110 can be moved in the direction of the central axis so that the partial positioning portions 120a to 120c do not interfere with each other. The configuration shown in FIGS. 2A to 2C has an advantage that the possibility of contact with the frame when the wafer holding unit 100 is moved up and down is reduced.

The structure of the frame does not need to employ the movable positioning portion 120 as described above, and may be fixed. That is, the frame may have any configuration as long as the center axis 100a of the wafer holding unit 100 substantially coincides with the center axis of the frame.

FIG. 3 is an explanatory view showing a modified example of the frame and the wafer holder. In this modification, the positioning portion 124 and the wafer holding portion 105 have a conical tapered surface. When the wafer holding unit 105 is lowered, the wafer holding unit 105 stops with the tapered surface of the wafer holding unit 105 and the tapered surface of the positioning unit 124 in contact with each other. As a result, the wafer holding unit 1
00 is located within a certain error range from the central axis of the frame 112, and the wafer holding unit 10
5 is arranged substantially perpendicular to the Z-axis direction.
That is, the tapered positioning portion 124 has both functions of the central axis adjusting mechanism 121 and the parallelism adjusting mechanism 122 of the positioning portion 120 in FIG.

As shown in FIG. 1, the Rθ stage 130
Is composed of a θ stage 131 and an R stage 132, and an R stage 132 is installed on the θ stage 131. The optical unit 1 installed on the Rθ stage 130 by rotating the θ stage 131
40 can be rotated about a central axis 100 a of the wafer holder 100. In addition, by moving the R stage 132, the optical unit 140 installed on the Rθ stage 130 can be moved in the radial direction of the wafer holding unit 100. In this embodiment, the Rθ stage 13 is used as a moving mechanism of the optical unit 140.
Although 0 is used, an XY stage may be used instead. That is, as the moving mechanism, the wafer holding unit 1
Various mechanisms that can relatively move at least one of the optical unit 00 and the optical unit 140 in a plane parallel to the lower surface 100u of the wafer holding unit 100 can be used.

The optical unit 140 captures an image of the surface of the semiconductor wafer WF by a known configuration including a camera, a light source for illumination, an objective lens, and the like. In this embodiment, the imaging area of the optical unit 140 is smaller than the size of one semiconductor chip formed on the surface of the semiconductor wafer. As described later, the multi-tone image of the semiconductor wafer WF is processed by the image processing unit 50, whereby the rotation direction of the semiconductor wafer WF is detected. On the monitor 136 of the control operation unit 30 (FIG. 1), a multi-tone image of a partial imaging region of the semiconductor wafer WF is displayed.

The control operation unit 30 includes a display unit 31,
An operation unit 32, a control unit 33, a stage driving unit 34,
Stage coordinate reading unit 35 and image processing unit 50
And a monitor 136. As the display unit 31, for example, a CRT or a liquid crystal display is used.
As the operation unit 32, for example, a keyboard or a mouse is used.

When the user operates the operation unit 32 to input a movement command for the Rθ stage 130, the control unit 33 controls the stage driving unit 34 to
The stage 130 is moved in the R direction and the θ direction. Also,
When a stage coordinate reading command is input from the operation unit 32, the stage coordinate information at that time is read by the stage coordinate reading unit 35 and supplied to the control unit 33. The stage coordinate information is displayed on the display unit 31 as needed. The stage coordinate information is further supplied from the control unit 33 to the image processing unit 50. As described later, the image processing unit 50 determines an accurate rotation direction and a measurement position of the wafer by using the rotation direction of the wafer recognized by the image processing and the stage coordinate information.

FIG. 4 is a block diagram showing the internal configuration of the image processing unit 50. This image processing unit 50
Are a CPU 210, a ROM 214, and a RAM 216
, Image memory 218, input / output interface 240
Are configured as a computer system connected to the bus line 212. Input / output interface 24
The monitor 136, the magnetic disk 138, and the control unit 33 are connected to 0.

In the RAM 216, the rotation direction limiting means 15
0, an imaging position determination unit 152, a pattern matching unit 154, a rotation direction determination unit 158, a reference position determination unit 160, a measurement position determination unit 162, and a coordinate conversion unit 164. Is stored. The function of each of these means will be described later.

A computer program (application program) for realizing the function of each of these means
Is provided in the form of being recorded on a portable recording medium (portable recording medium) such as a flexible disk or a CD-ROM, and is transferred from the recording medium to an external storage device of the computer system. At the time of execution, the RAM 216
Is stored. Alternatively, a computer program may be supplied from a program supply device to a computer system via a communication path. In this specification, a computer system refers to a device that includes hardware and an operating system and operates under the control of the operating system. The application program causes such a computer system to realize the functions of the above-described units. Some of the functions described above may be realized by an operation system instead of the application program.

B. Outline of Alignment Processing: FIG. 5 is an explanatory diagram showing an outline of the wafer alignment processing in the embodiment. The reference wafer (FIG. 5A) is a wafer on which the same pattern as the wafer to be measured (FIG. 5B) to be aligned is formed. Generally, one of a plurality of wafers processed in the same lot is used as a reference wafer WF.
1, and the other wafer is used as the wafer to be measured WF2. One wafer has a notch reference point PN,
A wafer reference point PC, a plurality of measurement points M1 to M15 (shown by white circles), and measurement reference points (not shown) near the measurement points M1 to M15 are set. As shown in FIGS. 5A and 5B, it is assumed that the wafers WF1 and WF2 can take an arbitrary rotation direction when the wafers WF1 and WF2 are held by the wafer holding unit 100 (FIG. 1). I have. In this embodiment, since the guide ring 102 is provided on the wafer holding unit 100, the wafer can be held so that the center of the wafer is substantially at the center of the wafer holding unit 100. The center with the wafer holding unit 100 does not always coincide. That is, a positional shift due to a dimensional difference between the diameter of the wafer and the diameter of the guide ring 102 may occur.
Therefore, in the present embodiment, the center of the wafer is
It is assumed that they are not placed exactly at the center of 00.

FIG. 6 is a flowchart showing the overall procedure of the wafer positioning process in the embodiment. The pre-alignment pre-processing using the reference wafer (step T1) and the fine alignment pre-processing using the reference wafer (step T2)
And a pre-alignment process using a wafer to be measured (step T3) and a fine alignment process using a wafer to be measured (step T4).

Reference wafer W in step T1 of FIG.
In the pre-alignment pre-processing using F1, processing for determining wafer coordinates on the reference wafer WF1 is performed. In this process, a characteristic region near the center of the reference wafer WF1 and a wafer reference point PC (FIG. 5A) serving as a reference for wafer alignment near the region are specified. From the positional relationship between the designated area and the wafer reference point PC, the wafer coordinates of the reference wafer WF1 can be determined, and the coordinate conversion coefficient between the wafer coordinates and the stage coordinates can be obtained. Here, the “wafer coordinates” are coordinates in a coordinate system defined on the wafer (referred to as “wafer coordinate system”). “Stage coordinates” is Rθ
These are coordinates in a coordinate system (referred to as a “stage coordinate system”) defined by converting coordinates represented by polar coordinates on the stage 130 to an XY plane (FIG. 1). The stage coordinate system is defined in a state where the Rθ stage 130 is at the initial position, and the stage coordinate system does not move even if the Rθ stage 130 moves.

The coordinate conversion coefficient between the stage coordinates and the wafer coordinates is determined from the rotation angle θ _WF1 of the reference wafer WF1 held in the wafer holding unit 100 and the stage coordinate value of the wafer reference point PC (FIG. 5 (A)). Here, the rotation angle θ _WF1 of the reference wafer WF1 is an angle between the reference direction Ds of the stage coordinate system and the reference direction D _WF1 of the reference wafer WF1. The reference direction Ds of the stage coordinate system is a direction fixed with respect to the position of the Rθ stage 130 in the initial state.
= 0 ° (3 o'clock direction of the clock).
The reference direction D _WF1 of the reference wafer _WF1 is
1 is a direction fixed with respect to the reference wafer W, for example.
The notch NT of F1 is set to 3 o'clock when the notch NT of the watch is set to 12 o'clock. Note that these reference directions Ds, D
The setting method of _WF1 is arbitrary, and other definitions are also possible.

In the pre-fine alignment processing using the reference wafer WF1 in step T2, the reference wafer W
A plurality of measurement points M1 to M15 on F1 and positions of measurement reference points near each measurement point are registered. The position information of each point is registered as a coordinate value in a wafer coordinate system. Step T
1. Measurement information 139 including various information determined in T2
Are stored on the magnetic disk 138.

Steps T3 and T4 correspond to the measured wafer WF.
2 are pre-alignment processing and fine alignment processing. In the pre-alignment process in step T3, a coordinate conversion coefficient between the stage coordinates and the wafer coordinates of the wafer to be measured is determined as in step T1 (FIG. 5B). This makes it possible to associate the wafer coordinates of the reference wafer with the wafer coordinates of the measured wafer via the stage coordinates. In the fine alignment processing in step T4, the measurement information 139
, Each measurement point M1 to M15 on the wafer to be measured
Is determined.

C. FIG. 7 is a flowchart showing the procedure of the pre-alignment pre-processing using the reference wafer WF1 shown in step T1 of FIG. In step S101, the optical unit 140 on the Rθ stage 130 is moved by controlling the Rθ stage 130, and an image is captured at a position including the notch NT of the reference wafer WF1 in the imaging region FV. The control of the Rθ stage is performed by the imaging position determination unit 152.

FIG. 8 is an explanatory diagram showing a process for imaging the notch NT of the reference wafer WF1. Wafer holder 1
When R.00 (FIG. 1) is positioned by frame 110, Rθ stage 130 is set at the initial position (the origin of the stage coordinate system shown in FIG. 8D). At this time, the imaging area FV of the optical unit 140 is as shown in FIG.
As shown in the figure, the reference wafer WF1 is located near the center. The optical unit 140 captures an image of the pattern near the center of the reference wafer WF1, and the captured image is displayed on the monitor 136. As shown in FIG. 8, one side of the imaging region FV in the + R direction is indicated by a double line to indicate the + R direction of the Rθ stage 130.

A plurality of chips CP divided by scribe lines SL are formed on the wafer. The pattern formed on each chip CP on the wafer is often formed along the scribe line SL, and the direction of the scribe line SL can be known from the shape of the pattern near the center of the wafer (linear edge of the pattern). Often. In addition, the scribe line SL on the wafer is often formed parallel and perpendicular to the diameter direction of the wafer having the notch NT as one end, so if the direction of the scribe line SL is known from the pattern shape, Can be limited to four directions in many cases. Therefore, when the pattern on the wafer is formed along the scribe line SL, the notch direction can be estimated from the shape of the captured pattern near the center of the wafer.

FIG. 8B shows the relationship between the reference wafer WF1 and the imaging region FV when the imaging region FV is rotated by controlling the Rθ stage 130 in the θ direction based on the edge of the imaged pattern. Is shown. At this time, the orthogonal scribe line SL and the rectangular imaging region FV are parallel. In FIG. 8C, the Rθ stage 130 is set to + R
By controlling the direction, the imaging region FV is moved to the outer edge of the wafer. At this time, the imaging region FV is
It moves along the scribe line SL as shown in FIG. Notch N in imaging area FV at the outer edge of wafer
When T is not imaged, the imaging region FV is rotated by 90 degrees in the + θ direction, and is moved to a position including the notch NT in the imaging region FV to perform imaging. Thus, the reference wafer WF is determined based on the shape of the pattern formed on the wafer.
One notch NT can be held and an image can be taken.

As a procedure for imaging the notch NT of the reference wafer WF1, the step of FIG. 8B may be omitted. For example, if the direction of the scribe line SL cannot be estimated by the edge of the pattern imaged near the center of the wafer in FIG. 8A, the process of FIG. From the state ()), the imaging region FV may be moved toward the outer edge of the wafer in the + R direction. Then, the Rθ stage 130 is rotated in the θ direction to move the imaging region FV along the outer edge of the wafer and search for the notch NT of the wafer. However, as shown in FIG. 8B, if the imaging area FV is rotated along the orthogonal scribe line SL, in the step of searching for a notch in FIG. Need only be rotated, it is not necessary to search for the notch NT at the entire outer edge of the reference wafer WF1.
There is an advantage that an image can be captured.

In step S102 of FIG. 7, an area including the notch NT among the areas imaged as described above is designated using the operation unit 32 such as a mouse, and registered as a notch template image. At this time, a notch reference point which is an image reference point of the notch template image is also designated and registered. FIG. 9 is an explanatory diagram showing an area designated as the notch template image TMN and a notch reference point PN. Since the notch template image TMN is used in the pattern matching process in step T3 (FIG. 6) described later, it is preferable to specify a region including all the V-shaped notches NT as shown in FIG. Further, in FIG. 9, the notch reference point PN is designated at a position near the inflection point of the “V” -shaped notch, but is not limited to this position. For example, the point at the upper left corner of the notch template image TMN may be used. The notch template image TMN and the notch reference point PN specified in this way are stored in the measurement information 139.
Is registered in the magnetic disk 138 (FIG. 4). The coordinate value of the notch reference point PN is registered as a coordinate value (X _PN , Y _PN ) st in the stage coordinate system. Here, the suffix “st” means a coordinate value in the stage coordinate system.

In step S103 of FIG. 7, the imaging area FV is returned to the center of the stage, and an image is taken by capturing an image near the center of the reference wafer WF1. FIG. 10 is an explanatory diagram showing a process when capturing an image near the center of the reference wafer WF1. As shown in FIG.
When the control is performed in the direction and the vicinity of the center of the reference wafer WF1 is imaged, a pattern having straight edges substantially parallel to the rectangular imaging region FV is imaged.

In step S104, an image of a region including a pattern in which the notch direction can be limited to several directions in the imaging region FV near the center of the reference wafer WF1 is designated as the reference template image TMC. In addition,
This reference template image TMC is stored in a step T described later.
3 (FIG. 6) is used for pattern matching processing.

FIG. 11 is an explanatory diagram showing various patterns that can be included in the imaging region FV shown in FIG. As shown in FIG. 11, a pattern PTC1 having no rotational symmetry, a pattern PTC2 exhibiting 180-degree rotational symmetry, and a pattern P exhibiting 90-degree rotational symmetry are provided on the reference wafer WF1.
TC3 and the like may be present. In general, a figure obtained when the same figure is rotated by 2π / n (n is an integer of 1 or more) around the central axis is called “a figure having n times rotational symmetry”. In the present specification, a pattern having one rotational symmetry is referred to as a “pattern having no rotational symmetry”, and a pattern having two or more rotational symmetries is also referred to as a “pattern having rotational symmetry”. is there. Further, a pattern having two rotational symmetries such as the pattern PTC2 is also referred to as a “having a 180-degree rotational symmetry” pattern, and a pattern having four rotational symmetries such as the pattern PTC3 is referred to as a “90-degree rotational symmetry”. Has rotational symmetry "
Also called a pattern.

In FIG. 11, patterns PTC1-PTC
An area including TC3 is defined as a reference template image T
It can be designated as MC1 to TMC3. However, in actual processing, one of these is designated as the reference template image. In the reference template images TMC1 to TMC3 specified as shown in FIG. 11, the notch direction Dn can be limited to four or less from the rotational symmetry of the entire image. That is, the reference template image TMC1 including the pattern PTC1 having no rotational symmetry
Has no rotational symmetry even in the entire image, and it is possible to limit the notch direction of the wafer to one direction from the image. Also, a pattern PT having 180-degree rotational symmetry
The reference template image TMC2 including C2 has 180 ° rotational symmetry as a whole image, and the notch direction Dn of the wafer can be limited to two directions from the image. Similarly, the reference template image TMC3 including the pattern PTC3 having the rotational symmetry of 90 degrees is:
From the image, the notch direction Dn of the wafer can be limited to four directions.

In step S104 of FIG. 7, one of the regions including the pattern that can limit the notch direction to several directions as described above is designated and registered as a reference template image (for example, TMC1). At this time, a wafer reference point PC1 serving as an image reference point of the reference template image TMC1 is designated and registered. In the following, each of the three reference template images TMC1 to TMC3 may be described. However, in practice, only one reference template image is registered and used.

FIG. 12 is an explanatory diagram showing details of three types of reference template images TMC1 to TMC3. FIG.
As shown in (a) to (c), the reference template image T
Each of MC1 to TMC3 has a region with a width w added outside the circumscribed rectangle of patterns PTC1 to PTC3 having n times of rotational symmetry. In addition, upper left points are designated as wafer reference points PC1 to PC3 as image reference points of reference template images TMC1 to TMC3, respectively. Note that the wafer reference point PC is not limited to the upper left point of the reference template image, and another point may be used as the wafer reference point. The reference template image TMC and the wafer reference point PC specified in this way are registered as measurement information 139 on the magnetic disk 138 (FIG. 4). The wafer reference points PC1 to PC3 are registered as coordinate values (X _PC1 , Y _PC1 ) st of the stage coordinate system.

At this time, the reference template image T
The attribute information on the rotational symmetry of the MC is registered together with the reference template image TMC and the wafer reference point PC.
That is, when the reference template image TMC has no rotational symmetry, “1” is registered as the attribute information. Similarly, in the case of 180 degrees and 90 degrees of rotational symmetry,
“2” and “4” are registered as attribute information, respectively. That is, in the present embodiment, the attribute information is registered as “n” for the reference template image TMC having n times rotational symmetry.

In this embodiment, when the user specifies a pattern included in the reference template image TMC, the determination of the area of the reference template image TMC, the determination of the wafer reference point PC, and the determination of the attribute information will be described below. This is automatically performed by the reference position determining means 160 (FIG. 4).

FIG. 13 is an explanatory diagram showing the processing for determining the area of the reference template image TMC and the wafer reference point PC in this embodiment. FIG. 13A illustrates a captured image including the pattern PTC1 existing near the center of the wafer. This image is displayed on the monitor 136.
It is a display image displayed on (FIG. 1). As shown in FIG. 13A, an image captured near the center of the wafer is R
From the positional relationship between the θ stage 130 and the reference wafer WF1, for each side of the rectangular imaging region FV, the pattern PT
The straight edges of C1 may not be parallel. In this case, the image of the imaging region FV is rotated clockwise by the angle α1 by image processing and displayed on the monitor 136 as shown in FIG. The rotation of the image is performed by affine transformation. With respect to the image displayed in this manner, the user may select an area A1 including at least the entire pattern PTC1 used for the reference template image.
Is roughly specified. In FIG. 13C, the multi-tone image in the area A1 is processed, and the circumscribed rectangle A of the pattern PTC1 is processed.
2 are determined, and coordinate values (Smin, Tmin) and (Smax, Tmax) of two points indicating the range of the circumscribed rectangle A2 are obtained. In addition,
These two coordinate values are coordinate values in the display coordinate system represented by the S axis and the T axis in the display image of FIG. FIG.
In (d), the area of the reference template image is obtained from the two coordinate values. Area A3 of reference template image
Is determined as a region (L1 × L2) having a size obtained by adding a region having a width w to the entire outer periphery of the circumscribed rectangle A2 in FIG. 13C. That is, the area A3 is (Smax-Smin
+ 2w) × (Tmax−Tmin + 2w). In FIG. 13D, the coordinate value (Smin-w, Tmax + w) of the upper left corner of the area A3 is the wafer reference point PC1.
Is determined as In this way, as shown in FIG. 13E, the reference template image TMC1 including the pattern PTC1 is determined and registered on the magnetic disk 138 as the measurement information 139. The coordinate values (Smin-w, Tmax + w) of the wafer reference point PC1 in the display coordinate system are shown in FIG.
The coordinate value (X _PC1 , Y _PC1 ) st of the stage coordinate system is converted and registered by the inverse conversion of the conversion performed in 3 (b).

FIG. 14 is a flowchart showing a procedure for determining attribute information relating to rotational symmetry of a registered reference template image. Note that the reference template image of the original image used for determining the rotational symmetry of the registered reference template image (for example, the TMC in FIG. 13E)
1) is hereinafter also referred to as “0 ° template image”.

In step S105a, using the 0 ° template image, k rotated template images sequentially rotated at an angular interval of 360 ° / k are prepared. FIG.
FIG. 4 is an explanatory diagram showing a method for creating a rotated template image. FIG. 15 shows a case where four rotated template images TMCr sequentially rotated at 90 ° intervals (k = 4) are created. FIG. 15A shows the same 0 as the registered reference template image TMC1 (FIG. 13E).
The rotated template image TMCr ₀ is shown.
The magnetic disk 138 has a reference template image TMC
An image IM (wide area template image) of an area slightly larger than 1 is stored. 0 ° template image TMC
A rotated template image TMCr ₉₀ obtained by rotating r ₀ by 90 ° counterclockwise (FIG. 15B) is extracted in a state where the wide area template image IM is rotated by 90 ° around its center C. Rotated template images TMCr ₁₈₀ and TMCr ₂₇₀ rotated by 180 ° and 270 ° (FIG. 15
The same applies to (c) and (d)). As a result, step S
At 105a, four rotation template images TMCr created at rotation angles of 90 ° are obtained. Note that the rotation center of the rotated template image may not be the center C of the reference template image as shown in FIG. 15. Is also good.

In step S105b, a pattern matching process is performed between the wide area template image IM, which is an image of a slightly wide area including the reference template image TMC1, and the four prepared rotated template images TMCr. The pattern matching means 154 (FIG. 4) executes pattern matching processing with the wide area template image IM using each rotation template image TMCr, and calculates a matching degree (coincidence degree) in the range of the area of each rotation template image. .

In the pattern matching process, from the upper left end to the lower right end of the wide area template image IM,
While sequentially scanning with reference to the upper left point of each rotation template image TMCr, each rotation template image TM
The matching degree between the Cr area and the corresponding area of the wide area template image IM is checked. In this way, pattern matching processing is performed on all the rotated template images TMCr.

All prepared rotation template images TM
When the pattern matching process for Cr is completed,
In step S105c of FIG. 14, the number of rotated template images for which the degree of matching is equal to or greater than a predetermined value (hereinafter, referred to as the “number of matching images”) is checked. When the reference template image has no rotational symmetry as shown in FIG. 15, the number of matching images is one. FIG.
If the pattern matching process is performed on the reference template images shown in 2 (b) and (c), the number of matching images becomes two and four, respectively.

In step S105d, attribute information for the template image TMC is determined from the number of matching images obtained as described above. If the number of matching images is one, “1” is determined as the attribute information. Similarly, when the number of matching images is two or four, “2” and “4” are determined as attribute information, respectively. That is, since the number of matching images indicates the number of times of rotational symmetry, in this embodiment, the number of matching images is directly registered as attribute information indicating the rotational symmetry of the reference template image.

In FIG. 15, four rotated template images TMCr are prepared as the k rotated template images TMCr created in step S105a, but the value of k is arbitrary. The value of k is preferably determined in step S104 (FIG. 7) according to the least common multiple of the possible number of times n of the rotational symmetry of the reference template image TMC that may be specified by the user. For example, the pattern used for the reference template image TMC is a pattern having one, two, or four rotational symmetry (the pattern PTC shown in FIG. 12).
In the case where the value is limited to 1 to 3), the value of k may be set to “4”, which is the least common multiple of 1, 2, and 4, and the rotational symmetry may be checked at 90 ° intervals. If there is a possibility that a pattern having three rotational symmetries (eg, a regular triangular pattern) may be specified as the reference template image,
The value of k may be set to “12” which is the least common multiple of 1 to 4, and the rotational symmetry may be checked at 30 ° intervals.

According to the above, step S1 in FIG.
In 04, it is possible to automatically determine the area of the template image TMC including the pattern specified by the user, determine the wafer reference point PC, and determine the attribute information.

D. FIG. 16 is a flowchart showing the procedure of the fine alignment pre-processing using the reference wafer WF1 shown in step T2 of FIG. Note that the processing in step T2 is performed by the measurement position determining means 162 (FIG. 4).

In step S201, the user sets the monitor 1
The measurement point is searched while viewing 36, and the imaging region FV is moved to a position including the measurement point. FIG. 17 shows an Rθ stage 130.
Is an explanatory diagram showing a process when the imaging area FV is moved from the vicinity of the center of the wafer to the vicinity of the measurement point by controlling the imaging area FV. At this time, the optical unit 140 captures an image of a measurement point and a pattern existing near the measurement point. FIG. 18 is an explanatory diagram illustrating an imaging region FV including a measurement point. In the imaging region FV shown in FIG.
M1 exists.

In step S202, the image pickup area F
A measurement point included in V is designated and registered. In FIG. 18, when the measurement point M1 is designated, its coordinate value is registered as the coordinate value (X _M1 , Y _M1 ) st of the stage coordinate system.

In steps S203 and S204,
Around the measurement point M1, a region including a pattern suitable as a measurement template image is searched. In the imaging area FV, FIG.
If the image does not include an appropriate pattern as shown in FIG. 8, the imaging area FV is moved around the measurement point M1 and searched. When an appropriate pattern is found in the imaging region FV, in step S205, an image of the imaging region including the pattern is captured. The appropriate pattern here needs to be a pattern that can specify the position of the measurement point as one in the pattern matching processing in step T4 described later. Therefore, a pattern having no rotational symmetry is most preferable. However, a later-described step T3
If the wafer coordinates of the wafer to be measured are determined in the above, there is a possibility that a single measurement point can be determined even with a pattern having rotational symmetry.

In step S206, an area including an appropriate pattern in the captured image area is designated and registered as a measurement template image. In addition, an image reference point of the measurement template image is designated together with the measurement template image and registered as a measurement reference point. The process in step S206 is performed when a reference template image and a wafer reference point are specified in step T1 (see FIG. 1).
Since it is the same as 3), detailed description is omitted. In FIG. 18, the measurement template image TMM1 is designated.
The measurement reference point PM1 at the upper left corner of the template image TMM1 is designated as the image reference point. Note that the measurement reference point PM1 is represented by coordinate values (X _PM1 ,
Y _PM1 ) Registered as st.

In step S207, the measurement reference point PM1 (X _PM1 ,
Y _PM1) from st measurement point _M1 (X M1, Y M1) the vector to st movement amount _{ΔM1 (ΔX M1, ΔY M1)} = (X M1 -
X _MP1 , Y _M1 −Y _MP1 ). The movement amount ΔM1 (ΔX _M1 , ΔY _M1 ) is used when a measurement point on a wafer to be measured is obtained in step T4 described later.

In step S208, it is determined whether or not there is another measurement point. If there is another measurement point, the process returns to step S201 and the processes in steps S201 to S207 are repeated. Thus, a plurality of measurement points M on the reference wafer
By repeatedly executing steps S201 to S207 for 1 to M15, the coordinate values of the measurement points M1 to M15 and the measurement reference points PM1 to PM15 in the stage coordinate system can be determined. Further, the respective movement amounts Δ from the measurement points M1 to M15 and the measurement reference points PM1 to PM15
M1 to ΔM15 can be determined by values in the stage coordinate system.

As described above, steps T1 and T2 (FIG. 6)
Reference point PC, notch reference point P registered in
N, measurement reference points PM1 to PM15, movement amounts ΔM1 to ΔM
Numeral 15 converts the coordinate values of the stage coordinate system into the coordinate values of the wafer coordinate system. Note that this coordinate conversion is executed by the coordinate conversion means 164 (FIG. 4).

FIG. 19 is an explanatory diagram showing the relationship between the stage coordinate system and the wafer coordinate system in this embodiment. In this embodiment, the wafer coordinate system represented by the U1-V1 axis is defined based on the registered reference template image TMC1. That is, the wafer reference point PC1 registered as the image reference point of the reference template image TMC1 is adopted as the origin of the wafer coordinate system. The U1 axis and the V1 axis are set in directions along two orthogonal sides of the rectangular reference template image TMC1. The origin (0,0) wf of the wafer coordinate system is a point represented by (X _PC1 , Y _PC1 ) st in the stage coordinate system. Here, the suffix “wf” means a coordinate value in the wafer coordinate system. Further, the coordinate axis U of the wafer coordinate system is used.
1, V1 is an angle δ1 from the coordinate axes X, Y of the stage coordinate system.
Only rotating counterclockwise. The angle δ1 is due to the rotation direction when the reference wafer WF1 is held by the wafer holding unit 100. The angle δ1 is obtained from the rotation angle θw1 of the Rθ stage 130 in the θ direction and the angle α1 obtained by rotating the image in the display image system when registering the reference template in FIG. Note that the angle α1
Is 0 °, the angle δ1 can be obtained only from the rotation angle θw1 of the Rθ stage 130 in the θ direction.

FIG. 19 shows the wafer coordinate system and the stage coordinate system.
In the case where there is a relationship as shown in the following, the coordinate transformation from the stage coordinates (X, Y) st to the wafer coordinates (U, V) wf is given by a two-dimensional affine transformation shown in the following equation (1). Can be

[0073]

(Equation 1)

According to equation (1), steps T1 and T1
Notch reference point PN, measurement reference point P registered in 2
M1 to PM15 and movement amounts ΔM1 to ΔM15 are converted from values in the stage coordinate system to values in the wafer coordinate system. FIG. 19 shows values of the notch reference point PN, the measurement reference point PM1, and the moving amount ΔM1 in the stage coordinate system and the values in the wafer coordinate system. Each value converted in this way is replaced with the value before the coordinate conversion, and
(FIG. 4).

E. FIG. 20 is a flowchart showing the procedure of the pre-alignment process using the wafer to be measured WF2 shown in step T3 in FIG. In step S301, the Rθ stage 130 is moved to the initial position (the coordinate origin of the stage coordinate system).
And captures an image of the vicinity of the center of the wafer to be measured WF2 and captures an image to be processed. The same design pattern as that of the reference wafer WF1 is formed on the surface of the measured wafer WF2, but the notch direction can take any direction.

In step S302, step S301
Using the processing target image fetched in step 1 and the reference template image TMC registered in advance in step T1,
While limiting the notch direction to some candidate directions,
A reference candidate point to be a wafer reference point on the wafer to be measured is obtained. The processing in step S302 is executed by the rotation direction limiting unit 150 and the pattern matching unit 154 in cooperation. The rotation direction limiting unit 150 and the pattern matching unit 154 correspond to a candidate direction determining unit of the present invention. The reference template image TMC registered in step T1 is used as a 0 ° template image in the following pattern matching processing.

FIG. 21 is a flowchart showing a procedure for obtaining a reference candidate point on a wafer to be measured. In step S302a, using the reference template image TMC registered in advance in step T1, a plurality of rotated template images TMCr sequentially rotated at intervals of 10 ° are prepared, and a plurality of rotated template images TMCr are combined with the processing target image captured in step S301 (FIG. 20). A pattern matching process is performed between them. The number of rotated template images prepared in step S302a is determined by the attribute information of the reference template image. That is, in the present embodiment, the number of prepared rotated template images is represented by (360 ° / 10 °) / n. Here, n is the number of times of rotational symmetry of the reference template image indicated by the attribute information of the reference template image.

For example, when the attribute information of the reference template image is “1”, that is, when the reference template image has no rotational symmetry, the rotated template image is set to 10 ° in an angle range of 0 ° to 350 °. 36 images (= (360 ° / 10 °) / 1) sequentially rotated at intervals are prepared. When the attribute information of the reference template image is “2”, that is, when the reference template image has two rotational symmetries, the reference template image is sequentially rotated at an interval of 10 ° within an angle range of 0 ° to 170 °. 18 (= (36
A rotated template image of (0 ° / 10 °) / 2) is prepared. Similarly, the attribute information of the reference template image is “4”.
In other words, if the reference template image has four rotational symmetries, nine (= (360 ° / 10 °) / 4) rotated template images are set in an angle range of 0 ° to 80 °. prepare. The rotation template image TM
Cr is extracted with the wide area template image rotated as in the case shown in FIG. Therefore,
The rotated template image prepared in step T1 can be used as it is in the processing of FIG.

FIG. 22 is an explanatory diagram showing a part of a plurality of prepared rotated template images TMCr. As for the 0 ° template image TMCr ₀ shown in FIG. 22, there is no rotational symmetry, so that 36 template images sequentially rotated at 10 ° intervals are prepared. Further, when creating the rotation template image TMCr, the coordinates obtained by rotating the coordinates of the wafer reference point around the center C are also prepared.

[0080] Figure 22 wafer reference point PCr in the template image TMCR ₀ of 0 ° shown in (a) _0, the table the center C as a coordinate origin, the coordinate axis F along each side of the rectangular template image TMCR _0, with G Is prepared as coordinate values of the coordinate system (FG coordinate system) to be performed. FIG.
The wafer reference points P in the 10 ° and 20 ° rotated template images TMCr ₁₀ and TMCr ₂₀ shown in (b) and (c).
Cr _10, PCr ₂₀ are also respectively prepared as the coordinate value of the F-G coordinate system along each side of the rectangular rotary template image TMCr _10, TMCr _20. Wafer reference points PCr ₀ , PC prepared as coordinate values of the FG coordinate system in this manner
r ₁₀ and PCr ₂₀ are used when obtaining a wafer reference point candidate point in step S302c described later.

After preparing a plurality of rotated template images TMCr as shown in FIG. 22, step S301 (FIG.
A pattern matching process is performed with the image to be processed in the vicinity of the center of the wafer to be measured, which is captured in step 0). This processing is performed while scanning each of the plurality of rotated template images TMCr in the processing target image in the same manner as described above.

When a reference template image having no rotational symmetry as shown in FIG. 22 is used, pattern matching processing is performed in an angle range of 0 to 350 ° using 36 rotated template images at 10 ° intervals. . On the other hand, when a reference template image having rotational symmetry is used, for example, when two reference template images having rotational symmetry are used, 18 rotational template images at 10 ° intervals are used, and 0 to 170 ° are used. Is performed in the angle range of. When a reference template image having four rotational symmetries is used, 9
The pattern matching process is performed in the angle range of 0 to 80 ° using the rotated template images. Step S30
In 2a, the pattern matching process is performed in such an angle range to obtain the rotation angle (coarse matching angle) of the rotated template image having the highest matching degree.

In step S302b, step S30
In the vicinity of the rough matching angle obtained from the result of the pattern matching process in 2a, the pattern matching process is further performed by preparing rotated template images at 1 ° intervals. In the pattern matching processing in step S302b, the rotation angle of the wafer to be measured can be more accurately obtained by obtaining the rotation angle (matching angle) having the highest matching degree.

In step S302b, only one matching angle is obtained regardless of the presence or absence of rotational symmetry of the reference template image. Also in this case, step S
From one matching angle obtained in 302b,
N candidate directions are determined as the notch directions. That is, when the pattern matching process is performed using the reference template image having two rotational symmetries twice, the matching angle obtained in step S302b and the angle obtained by adding 180 ° to the matching angle are calculated as 2
One candidate direction is determined. Similarly, when the pattern matching processing is performed using the reference template image having four rotational symmetries, the matching angle obtained in step S302b and the matching angle are set to 9
Four candidate directions are determined from the three angles added by 0 °.

As described above, the number of rotation template images used in the pattern matching process, that is, the angle range in which the pattern matching process is performed, is determined by the attribute information on the rotation symmetry of the reference template image, ie, the number of rotation symmetries “n”. Is limited, all candidate directions can be easily known simply by performing pattern matching processing only in the angle range.

Note that the rotation angle when creating a rotation template image in steps S302a and S302b is not limited to 10 ° and 1 °, respectively, and can be arbitrarily set by the user.

In step S302c, a reference candidate point of the wafer reference point on the measured wafer is obtained from the rotated template image having the highest matching degree. FIG.
FIG. 14 is an explanatory diagram showing reference candidate points obtained from the result of the pattern matching process in step S302b. FIG. 23A shows a rotated template image TM showing the highest matching degree in a pattern matching process using a reference template image having no rotational symmetry.
Cβ1 is shown. FIG. 23B shows a rotated template image TMCβ2 showing the highest matching degree in the pattern matching process using the reference template image having two rotational symmetries. Similarly, FIG. 23 (c) shows the rotated template image TMCβ3 showing the highest matching degree in the pattern matching process using the reference template image having four rotational symmetries. FIG. 23 (a)
In (c), the rotated template images TMCβ1
The position where TMCβ3 is shown indicates the scanning position where the matching degree is the highest.

As shown in FIGS. 23A to 23C, when the scanning position with the highest matching degree is determined, the coordinate value corresponding to the center C of the rotated template images TMCβ1 to TMCβ3 is determined by j of the image to be processed. Determined in k-coordinate system. When the coordinate value of the center C of the rotation template image is determined in the jk coordinate system, the rotation template image T
The coordinate value of MCβ corresponding to wafer reference point PCβ is also determined. Note that the wafer reference point PCβ in the jk coordinate system
Is the coordinate value of the center C in the jk coordinate system,
This is obtained by adding the coordinate value of the wafer reference point in the FG coordinate system shown in FIG. 22 as it is. As described above, when the coordinates of the wafer reference point PCβ are determined in the jk coordinate system according to the rotated template image TMCβ, the wafer reference point PCβ
The coordinate value of β in the stage coordinate system can be determined.

From the pattern matching process using a reference template image having no rotational symmetry as shown in FIG. 23A, one reference candidate point of the wafer reference point is obtained. FIG. 23A shows one candidate point PCβ1a. Therefore, this one reference candidate point PCβ1a is obtained as the wafer reference point PC on the measured wafer.

On the other hand, a plurality of reference candidate points of the wafer reference point are obtained from the pattern matching processing using the reference template image having the rotational symmetry as shown in FIGS. As shown in FIG. 23 (b), when the pattern matching processing is performed using the reference template image having two rotational symmetries, two candidate points of the wafer reference point are obtained. That is, the first candidate point PCβ2a of the wafer reference point is obtained from the rotation template image having the highest matching degree among the rotation angles subjected to the pattern matching processing. In addition to the first candidate point PCβ2a obtained by the pattern matching process, a point obtained by rotating the first candidate point PCβ2a by 180 ° around the center C can also be a candidate point. PC
β2b. As shown in FIG. 23C, when pattern matching is performed using four times of reference template images having rotational symmetry, four reference candidate points of the wafer reference point are obtained. That is, the first candidate point PCβ3a of the wafer reference point is obtained from the rotation template image having the highest matching degree among the rotation angles subjected to the pattern matching processing. Further, in addition to the first candidate point PCβ3a obtained by the pattern matching processing, other equivalent points obtained by rotating the first candidate point by 90 ° around the center C can also be candidate points. The second to fourth candidate points PCβ3b to PCβ3d are obtained.

When the coordinate values of the reference candidate point in the stage coordinate system are obtained in this way, in step S302d,
A wafer coordinate system corresponding to each reference candidate point is generated, and a notch candidate point of the notch reference point is obtained as a coordinate value of the stage coordinate system.

FIG. 24 is an explanatory diagram showing a wafer coordinate system generated corresponding to the reference candidate points of the wafer reference points shown in FIG. 23A together with a stage coordinate system. Wafer coordinate system represented by U2'β _1a -V2'β _1a axis shown in FIG. 24, based on the one reference candidate points PCβ1a obtained from the rotating template image TMCβ1 highest matching degree in FIG 23 (a) This is the generated coordinate system. FIG.
Wafer coordinate system is the coordinate value of the stage coordinate system of the reference candidate point _{PCβ1a (X PC β 1a, Y} PC β 1a) a st as coordinate origin (0,0) wf wafer coordinate system, the rectangular reference template image TMC1 Are set in directions along two sides of the region. Coordinate axes U2′β _1a , V2′β of wafer coordinate system
_1a is rotated by counterclockwise angle .delta..beta _1a from axes X, Y of the stage coordinate system. The angle δβ _1a is due to the rotation direction when the wafer to be measured WF2 is held by the wafer holding unit 100. This angle δβ _1a is shown in FIG.
9, the rotation angle θ of the Rθ stage 130 in the θ direction.
w2 and the rotation angle β1 at which the degree of matching of the rotated template image is the highest. When the rotation angle θw2 of the Rθ stage 130 is 0 °, the wafer coordinates can be obtained only from the matching angle β1.

When the wafer coordinate system as shown in FIG. 24 is determined, based on the positional relationship of the notch reference point PN with respect to the wafer reference point PC1 obtained on the reference wafer WF1 shown in FIG. One candidate point PN1a of the notch reference point for one candidate point PCβ1a is determined. When the reference candidate point PCβ1a is represented by the coordinate value (0,0) wf in the wafer coordinate system, the notch reference point candidate point P
N1a the coordinate value of the wafer coordinate system (U _PN, V _PN) represented by wf.

FIG. 24 shows the wafer coordinate system and the stage coordinate system.
In the case of having the relationship shown in FIG.
V) The coordinate transformation from wf to the stage coordinates (X, Y) st is given by a two-dimensional affine transformation shown in the following equation (2).

[0095]

(Equation 2)

According [0096] Equation (2), the candidate point PN1a notch reference point is converted coordinate value of the wafer coordinate system (U _PN, V _PN) from wf coordinate values of the stage coordinate system (X _PN1a, Y _PN1a) to st You. As described above, when the wafer coordinate system is generated based on the rotation template image TMCβ1 having no rotational symmetry and the reference candidate point PCβ1a as shown in FIG. 23A, there is only one notch reference point candidate point. And is stored as the coordinate value of the stage coordinate system.

FIG. 25 is an explanatory diagram showing two wafer coordinate systems generated corresponding to the two reference candidate points of the wafer reference points shown in FIG. 23B together with the stage coordinate system.
First wafer coordinate system represented by U2'β _2a -V2'β _2a-axis shown in FIG. 25, a first reference candidate points matching level is determined from the highest rotation template image TMCβ2 shown in FIG. 23 (b) This is a coordinate system generated based on PCβ2a. Coordinate axes U2′β _{2a of} the first wafer coordinate system,
V2′β _2a is an angle δ from the coordinate axes X and Y of the stage coordinate system.
It rotates counterclockwise by _β2a . This angle δβ
_2a is the rotation angle θ2 of the Rθ stage 130 in the θ direction,
It is obtained from the rotation angle β2 at which the matching degree of the rotation template image is the highest. On the other hand, U2'β _2b -V
The second wafer coordinate system represented by the 2'β _2b axis is shown in FIG.
3 (b) second reference candidate point PCβ2 obtained from rotated template image TMCβ2 having the highest matching degree
This is a coordinate system generated based on b. The coordinate axes U2′β _2b and V2′β _2b of the second wafer coordinate system are rotated counterclockwise by an angle δβ _2b from the coordinate axes X and Y of the stage coordinate system. This angle δβ _2b is an angle obtained by adding 180 ° to the rotation angle δβ _2a of the first wafer coordinate system.

When two wafer coordinate systems are generated as shown in FIG. 25, as in FIG. 24, two notch reference points for two candidate points PCβ2a and PCβ2b of the wafer reference point are set.
The coordinate values of the two candidate points PN2a and PN2b in the stage coordinate system are determined. That is, the first reference candidate point PCβ2
When a is represented by the first coordinate value of the wafer coordinate system (0,0) wf, candidate points PN2a notch reference point, the coordinate value of the first wafer coordinate system (U _PN, V _PN) in wf expressed. Notch candidate point PN2a represented by the coordinate value of the first wafer coordinate system
Is converted into a coordinate value (X _PN2a , Y _PN2a ) st of the stage coordinate system by a two-dimensional affine transformation similar to the equation (2) from the relationship between the first wafer coordinate system and the stage coordinate system.
When the second reference candidate point PCβ2b is represented by the coordinate value (0,0) wf in the second wafer coordinate system, the notch reference point candidate point PN2b is represented by the coordinate value ( U
_PN , V _PN ) wf. The notch candidate point PN2b represented by the coordinate value of the second wafer coordinate system is converted into the coordinate value ( _XPN2b , _YPN2b ) st of the stage coordinate system from the relationship between the second wafer coordinate system and the stage coordinate system. Is done.

As described above, the rotation template image TMCβ2 having two rotational symmetries as shown in FIG.
When two wafer coordinate systems are generated based on the two reference candidate points PCβ2a and PCβ2b, two notch reference point candidate points are obtained and stored as coordinate values of the stage coordinate system.

Similarly, for the four reference candidate points of the wafer reference points shown in FIG. 23C, four wafer coordinate systems are generated from the respective reference candidate points. When four wafer coordinate systems are generated, the notch candidate points are coordinate-transformed according to the relationship between each wafer coordinate system and the stage coordinate system, and the coordinate values of the four notch candidate points in the stage coordinate system are stored.

In steps S303 to S305 in FIG. 20, one of the notch reference point candidate points obtained in step S302 is specified as a notch reference point, and the specified notch reference point is set to the notch reference point. Identify the corresponding wafer reference point. Therefore, when there is only one reference candidate point PCβ1a as shown in FIG. 24, the notch reference point and the wafer reference point are specified as the notch candidate point PN1a and the reference candidate point PCβ1a, respectively. The process of S305 may be omitted. Of course, for confirmation, step S303
To S305 may be executed. Step S
The processing of steps 303 to 305 is executed by the rotation direction determining means 158 (FIG. 4), and determines the rotation direction of the wafer by specifying the notch reference point. The rotation direction determining means 158 corresponds to the wafer reference direction determining unit of the present invention.

In step S303, step S303
The Rθ stage 130 is controlled based on the coordinate values of the plurality of notch candidate points obtained in the stage coordinate system in the stage coordinate system, and the images of the imaging regions around each notch candidate point are captured. For example, in FIG. 25, images around the first and second notch candidate points PN2a and PN2b are captured.

In step S304, step S303
The same pattern matching processing as described above is performed using the notch template image TMN (FIG. 9) pre-registered in step T1 with the images of the imaging areas around the plurality of notch candidate points captured in the above as the processing target images.

In step S305, step S304
The notch candidate point included in the processing target image with the highest matching degree is specified as the notch reference point from the result of the pattern matching processing in. When the notch reference point is specified, the candidate point of the wafer reference point corresponding to the notch reference point is specified as the wafer reference point. For example,
First and second notch candidate points PN2a, PN shown in FIG.
When the first notch candidate point PN2a is specified as the wafer reference point from among 2b, the first reference candidate point PCβ2a is specified as the wafer reference point.

Steps S303 to S305 (FIG. 2)
The processing of 0) may not be performed for all the notch candidate points. For example, as shown in FIG.
If there is one, the pattern matching process may be performed on one of the notch candidate points. That is, the first
Of the notch candidate point PN2a, the first notch candidate point PN2a is specified as a notch reference point when a high matching degree is obtained, and the second notch candidate point PN2a is specified as a notch reference point when a high matching degree is not obtained. The second notch candidate point PN2a may be specified as the notch reference point. In short, the processing of steps S303 to S305 is
The operation may be performed until the notch reference point can be specified. Therefore, when there are four notch candidate points, the pattern matching process may be performed on up to three notch candidate points. By doing so, the number of pattern matching processes can be reduced, so that a notch reference point can be easily specified, and a wafer reference point can be specified from the specified notch reference points. Of course, the processing of S303 to S305 may be performed for all notch candidate points for confirmation.

When the wafer reference point is specified as described above,
One of the plurality of wafer coordinate systems as shown in FIG. 25 is specified as the wafer coordinate system of the wafer to be measured WF2, and the information on the measurement point obtained in step T2 (FIG. 6) is used for the wafer to be measured WF2. Measurement points can be determined.

F. Fine Alignment Processing Using Wafer to be Measured: FIG. 26 is a flowchart showing the procedure of the fine alignment processing using the wafer to be measured WF2 shown in step T4 of FIG. The processing in step T4 is performed under the control of the measurement position determination means 162 (FIG. 4). In step S401, the Rθ stage 130
To control the imaging area F at the position of the measurement reference point on the measured wafer WF2 corresponding to the measurement reference point on the reference wafer WF1.
Move V. The measurement reference point on the measured wafer WF2 is a point registered as a coordinate value in the wafer coordinate system shown in FIG. Therefore, in step S401, first, in order to control the Rθ stage 130,
In step T3, the coordinate value of the measurement reference point represented in the wafer coordinate system specified is coordinate-transformed into the coordinate value of the stage coordinate system. This coordinate conversion is executed by the coordinate conversion means 164.

FIG. 27 is an explanatory diagram showing the relationship between the wafer coordinate system specified on the measured wafer WF2 and the stage coordinate system. Wafer coordinate system consisting of U2-V2-axis shown in FIG. 27 is a wafer coordinate system represented by U2'β _1a -V2'β _1a axis shown in FIG. 24 is specified by the processing in step T3. In the wafer coordinate system specified in this way, as shown in FIG. 27, measurement reference points PM1 to PM15, which are image reference points of the measurement template image registered in step T2, and measurement reference points PM1 to PM15, respectively. Measurement points M1 to M15
The movement amounts ΔM1 to ΔM15 are associated with each other.

Each point expressed in the wafer coordinate system is transformed into a stage coordinate system by a two-dimensional affine transformation similar to the above-mentioned equation (2). By this coordinate conversion, the coordinate value ( _UPM1 , _VPM1 ) wf of the measurement reference point PM1 in the wafer coordinate system.
Is the coordinate value (X _PM β ₁ , Y _PM β ₁ ) st in the stage coordinate system
Is converted to In addition, from the measurement reference point PM1 to the measurement point M1
Vector value of the movement amount ΔM1 in the wafer coordinate system (Δ
U _M1 , ΔV _M1 ) wf is converted into a vector value (ΔX _M β ₁ , ΔY _M β ₁ ) st in the stage coordinate system.

In step S401, the Rθ stage 130 is controlled in accordance with the coordinate values converted into the stage coordinate system to move the imaging area FV to the position of the measurement reference point PM near each measurement point M. Let it. In addition,
As described above, the stage coordinate value of the measurement reference point PM obtained by the coordinate conversion indicates the predicted position of the measurement reference point PM. That is, the stage coordinate value of the measurement reference point PM obtained by the coordinate conversion is the lower surface 10 of the wafer holder 100 shown in FIG.
When 0u is not arranged perpendicularly to the Z-axis direction, etc.,
There is a possibility that the coordinates may be slightly deviated from the stage coordinate value of the actual measurement reference point. Therefore, in the present embodiment, a pattern matching process is performed between an image captured near the predicted position of the measurement reference point PM and a pre-registered measurement template image, and the position of the accurate measurement reference point is determined from the result of the pattern matching process. Ask.

In step S402, an image captured near the expected position of the measurement reference point PM is fetched as a processing target image, and a plurality of rotation template images are prepared from the measurement template image TMM (FIG. 18) registered in step T2. Then, a pattern matching process is performed. In step S403, the stage coordinate value of the measurement reference point PM, which is the image reference point, is obtained from the rotated template image having the highest matching degree in step S402. As described above, by performing the pattern matching process using the pre-registered measurement template image TMM near the measurement reference point PM, the measured wafer WF2
, The coordinate value of the measurement reference point PM in the stage coordinate system can be accurately obtained.

In step S404, step S403
The measurement point M is determined by using the measurement reference point PM determined in the above, and the measurement point M is determined as a coordinate value in the stage coordinate system. The coordinate value of the measurement point M in the stage coordinate system is obtained by adding the movement amount ΔM converted to the stage coordinate system as shown in FIG. Determined by plus. Since the coordinate value of the measurement point M determined in this way is determined based on the accurate measurement reference point PM obtained by the pattern matching processing in step S403, the pattern matching processing in step S403 is omitted. The coordinate value of the measurement point M is determined as a coordinate value with higher accuracy as compared with a case where the coordinate value is determined by performing coordinate conversion as it is. Of course, the coordinate value when the pattern matching process of S403 is omitted may be determined as the coordinate value of the measurement point M.

In step S405, it is determined whether or not there is another measurement point. If there is another measurement point, the process returns to step S401 and the processes in steps S401 to S404 are repeated. Thus, steps S401 to S401 are performed for a plurality of measurement points M1 to M15 (FIG. 5) on the measured wafer.
By repeatedly executing 404, the actual measurement position of each measurement point can be accurately determined. The measurement process (for example, film thickness measurement) at each measurement point can be performed between step S404 and step S405. Alternatively, the steps S401 to S404 may be repeatedly performed for all the measurement points, and then the measurement processing at each measurement point may be sequentially performed.

As described above, in this embodiment, when registering a reference template image serving as a reference for wafer coordinates, attribute information (rotational symmetry information) indicating the rotational symmetry of the image is also registered. I have. With this attribute information, even when the reference template image has rotational symmetry, one wafer coordinate can be specified from among a plurality of wafer coordinate candidates. Further, when determining the wafer coordinates of the wafer to be measured by the pattern matching processing, the processing range (rotation angle of the rotating template image) in which the pattern matching processing is to be performed can be limited based on the attribute information. It becomes possible to determine the wafer coordinates by performing the pattern matching process with time. This makes it possible to determine the direction and position of the wafer held in an arbitrary rotation direction, and to determine an accurate measurement point on the wafer.

The present invention is not limited to the above Examples and Embodiments, but can be implemented in various modes without departing from the gist of the invention.
For example, the following modifications are possible.

(1) In the above embodiment, part of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware. You may do so.

(2) In the above embodiment, the image including the notch NT (notch template image) is used as the image including the second reference pattern for determining the rotation direction of the wafer. May be included. That is, the second for determining the rotation direction of the wafer
May be used as long as the same pattern does not exist in the entire wafer. However, even when there are a plurality of the same patterns on the wafer, it is sufficient if there are no other same pattern groups when the entire patterns are viewed as one pattern group.

(3) In the above embodiment, the image of the area including the pattern existing near the center of the wafer is used as the first template image. However, the pattern included in the first template image exists near the center of the wafer. The pattern need not be a pattern, and may be a pattern at a position distant from the vicinity of the center of the wafer. However, if the initial position of the Rθ stage is set near the center of the wafer as in this embodiment, it is possible to easily capture an image including the pattern if the pattern is near the center of the wafer.

(4) In the above embodiment, the image of the area including the pattern existing near the measurement point M is registered as the measurement template image TMM, and the image reference point of the measurement template image TMM is set to the measurement reference point PM. However, the measurement reference point PM need not be registered. That is, the measurement point M may be registered as the image reference point of the measurement template image TMM. By doing so, the pattern matching process using the measurement template image TMM performed when the measurement point M is determined on the wafer to be measured,
The measurement point M, which is the image reference point, can be directly determined.

(5) In the above embodiment, in order to image an arbitrary position on the wafer surface, the imaging optical system (optical unit 140) is set to Rθ with the wafer fixed to the wafer holding unit.
Although it is moved using the stage 130, it is not limited to this. That is, the imaging optical system may be fixed, and the wafer may be held and moved by the moving stage. Further, both the wafer and the imaging optical system may be movable. For example, rotating the wafer in the θ direction,
The imaging optical system may be moved in the R direction.

(6) In the above embodiment, the apparatus for determining the measurement position of the wafer has been described, but this apparatus can also be used as a device for determining the rotational direction of the wafer. When only the rotation direction of the wafer is determined, the processes in steps T2 and T4 shown in FIG. 6 may be omitted.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a wafer measurement position determination device of the present invention.

FIG. 2 is an explanatory diagram showing an operation of a positioning unit 120.

FIG. 3 is an explanatory view showing a modified example of a frame and a wafer holding unit.

FIG. 4 is a block diagram showing an internal configuration of an image processing unit 50.

FIG. 5 is an explanatory diagram showing an outline of a wafer alignment process in the embodiment.

FIG. 6 is a flowchart showing an overall procedure of a wafer alignment process in the embodiment.

7 is a flowchart showing a procedure of pre-alignment pre-processing using a reference wafer WF1 shown in step T1 of FIG.

FIG. 8 is an explanatory diagram showing a process when imaging the notch NT of the reference wafer WF1.

FIG. 9 is an explanatory diagram showing an area designated as a notch template image TMN and a notch reference point PN.

FIG. 10 is an explanatory diagram showing a process when capturing an image near the center of a reference wafer WF1.

11 is an explanatory diagram showing various patterns that can be included in the imaging region FV shown in FIG.

FIG. 12 shows three types of reference template images TMC1 to TMC.
Explanatory drawing which shows the detail of MC3.

FIG. 13 is a reference template image TM according to the present embodiment.
Explanatory drawing which shows the process at the time of determining the area | region of C and the wafer reference point PC.

FIG. 14 is a flowchart illustrating a procedure for determining attribute information relating to rotational symmetry of a registered reference template image.

FIG. 15 is an explanatory diagram showing a method for creating a rotated template image.

FIG. 16 shows a reference wafer WF1 shown in step T2 of FIG.
9 is a flowchart showing a procedure of a pre-alignment process using the method shown in FIG.

FIG. 17 is a diagram illustrating an example of controlling the Rθ stage 130 to adjust the imaging area F;
FIG. 9 is an explanatory diagram showing a process when V is moved from the vicinity of the center of the wafer to the vicinity of the measurement point.

FIG. 18 is an explanatory diagram showing an imaging region FV including a measurement point.

FIG. 19 is an explanatory diagram showing a relationship between a stage coordinate system and a wafer coordinate system in the present embodiment.

20 is a measured wafer WF shown in step T3 of FIG.
9 is a flowchart showing a procedure of a pre-alignment process using the second embodiment.

FIG. 21 is a flowchart showing a procedure for obtaining a reference candidate point on a wafer to be measured.

FIG. 22 shows a plurality of prepared rotation template images TM.
Explanatory drawing which shows some Cr.

FIG. 23 is an explanatory diagram showing reference candidate points obtained from the result of the pattern matching process in step S302b.

FIG. 24 is an explanatory view showing a wafer coordinate system generated corresponding to the reference candidate points of the wafer reference points shown in FIG. 23A together with a stage coordinate system.

FIG. 25 is an explanatory diagram showing two wafer coordinate systems generated corresponding to two reference candidate points of the wafer reference points shown in FIG. 23 (b) together with a stage coordinate system.

26 is a wafer under test WF shown in step T4 of FIG.
4 is a flowchart showing the procedure of a fine alignment process using the second embodiment.

FIG. 27 is an explanatory diagram showing a relationship between a wafer coordinate system and a stage coordinate system specified on a wafer to be measured WF2.

[Explanation of symbols]

 Reference Signs List 30 control operation unit 31 display unit 32 operation unit 33 control unit 34 stage driving unit 35 stage coordinate reading unit 50 image processing unit 100, 105 wafer holding unit 100a, 105a central axis of wafer holding unit 100u, 105u Lower surface of wafer holding part 102 Guide ring 110, 112 Frame 120, 124 Positioning part 120a-120c Partial positioning part 121 Central axis adjustment mechanism 122 Parallelism adjustment mechanism 130 Rθ stage 131 θ Stage 132 R stage 136 Monitor 138 Magnetic disk 139 Measurement information 140 Optical unit 150 Rotation direction limiting unit 152 Imaging position determination unit 154 Pattern matching unit 158 Rotation direction determination unit 160 Reference position determination unit 162 … Measurement position Determination means 164 Coordinate conversion means 210 CPU 212 Bus line 214 ROM 216 RAM 218 Image memory 240 Input / output interface CP Chip NT Notch SL Scribe line WF Semiconductor wafer WF1 Reference wafer WF2 Wafer to be measured

Claims (8)

[Claims] 1. A method for determining a rotation direction of a wafer held by a wafer holding unit, comprising: (a) a first direction having rotation symmetry near a first predetermined position on the wafer;
(B) preparing in advance a first template image including the reference pattern of (1) and rotational symmetry information indicating the number n of rotational symmetries of the first reference pattern; and (b) a second predetermined pattern on the wafer. Preparing in advance a second template image including a second reference pattern existing near the position;
(C) capturing a first processing target image near the first predetermined position on the wafer while being held by the wafer holding unit; and (d) capturing a first processing target image within the first processing target image. Determining a direction of a matching image that matches the first template image; and (e) determining n candidate directions as reference directions of the wafer from the direction of the matching image and the rotational symmetry information. Process and
(F) When the number of times of rotational symmetry n is 1, the candidate direction is selected as the reference direction. When the number of times of rotational symmetry n is 2 or more, the candidate direction is selected from the n candidate directions. Estimating the second predetermined position on the wafer, capturing a second processing target image near the estimated second predetermined position, and extracting the second template image with respect to the second processing target image Selecting one appropriate direction as the reference direction from the n candidate directions by performing the used pattern matching. 2. The method according to claim 1, wherein the first predetermined position is a center position of the wafer, and the second predetermined position is on an outer edge of the wafer. A rotation direction of the wafer, wherein the second reference pattern is a notch formed on an outer edge of the wafer. 3. An apparatus for determining a rotation direction of a wafer, comprising: a wafer holding unit capable of holding a position of the wafer in a plane parallel to a surface of the wafer within a predetermined error range; An imaging unit that captures an image on the wafer held by the unit, a first template image that is present near a first predetermined position on the wafer and includes a first reference pattern having rotational symmetry, A rotational symmetry information indicating the number n of rotational symmetries of the first reference pattern, and a second template image including a second reference pattern existing near a second predetermined position on the wafer. Determining a direction of a matching image that matches the first template image in a first processing target image captured in the vicinity of the first predetermined position on the wafer; A pattern matching unit, a candidate direction determining unit that determines n candidate directions as a reference direction of the wafer from the direction of the matching image and the rotational symmetry information, and a case where the number n of rotational symmetries is 1. Selecting the candidate direction as the reference direction, while estimating the second predetermined position on the wafer from the n candidate directions when the rotational symmetry number n is 2 or more. Then, by performing pattern matching using the second template image on the second processing target image captured in the vicinity of the estimated second predetermined position, the n candidate directions are selected from among the n candidate directions. A reference direction determining unit that selects one appropriate direction as the reference direction. 4. The apparatus according to claim 3, wherein the first predetermined position is a center position of the wafer, and the second predetermined position is on an outer edge of the wafer. A rotation direction determining device for the wafer, wherein the second reference pattern is a notch formed on an outer edge of the wafer. 5. A method for determining a position of a measurement point on a wafer to be measured held by a wafer holding unit, the method comprising: (a) rotating near a first predetermined position on the wafer to be measured; A first template image including a first reference pattern having symmetry, rotational symmetry information indicating the number n of rotational symmetries of the first reference pattern, and the first reference pattern on the wafer to be measured Reference point position information indicating a positional relationship between the position of the measurement target wafer and a predetermined reference point, and measurement point position information indicating the position of the measurement point on the measurement target wafer, a step of preparing in advance, (B) a step of preparing in advance a second template image including a second reference pattern existing near a second predetermined position on the wafer to be measured; and (c) a state of being held by the wafer holding unit. On the wafer to be measured Capturing a first processing target image near the first predetermined position; and (d) determining a position and a direction of a matching image that matches the first template image in the first processing target image. (E) determining n candidate directions as reference directions of the measured wafer from the direction of the matching image and the rotational symmetry information; and (f) the number of times of the rotational symmetry. When n is 1, the candidate direction is selected as the reference direction. When the number of rotational symmetries n is 2 or more, the target direction is selected from the position of the matching image and the n candidate directions. Estimating the second predetermined position on the measurement wafer, capturing a second processing target image near the estimated second predetermined position, and setting the second template image with respect to the second processing target image Using Selecting one appropriate direction as the reference direction from the n candidate directions by performing the pattern matching described above; (g) selecting the reference direction determined in the step (f); (H) determining a position of the reference point of the measured wafer in a state held by the wafer holding unit from the position of the matching image determined in step (d) and the reference position information; The position of the reference point determined in the step (f), the position of the reference point determined in the step (g), and the measurement point position information. Determining a position of the measurement point on the wafer to be measured. 6. The method according to claim 5, wherein the first predetermined position is a center position of the wafer to be measured, and the second predetermined position is the wafer to be measured. A method for determining a measurement position of a wafer, wherein the second reference pattern is a notch formed on an outer edge of the wafer to be measured. 7. An apparatus for determining a position of a measurement point on a wafer to be measured, wherein the position of the wafer to be measured in a plane parallel to the surface of the wafer to be measured is held within a predetermined error range. A wafer holding unit to be obtained; an imaging unit that captures an image on the wafer to be measured held by the wafer holding unit; and a rotation symmetry that is present near a first predetermined position on the wafer to be measured. A first template image including a first reference pattern; rotational symmetry information indicating the number n of rotational symmetries of the first reference pattern; a position of the first reference pattern on the wafer to be measured; Reference point position information indicating a positional relationship with a predetermined reference point on the measured wafer, measurement point position information indicating a position of the measurement point on the measured wafer, and a second predetermined position on the measured wafer Neighborhood of A second template image including a second reference pattern present in the memory; and a first processing target image captured in the vicinity of the first predetermined position on the measured wafer. A pattern matching unit that determines the position and direction of a matching image that matches the first template image; and n candidate directions as reference directions for the wafer to be measured, based on the direction of the matching image and the rotational symmetry information. A candidate direction determining unit for determining the number of times of rotation symmetry, when the number of times of rotational symmetry n is 1, the candidate direction is selected as the reference direction, while when the number of times of rotational symmetry n is 2 or more, From the position of the matching image and the n candidate directions, the second predetermined position on the wafer to be measured is estimated, and an image is taken in the vicinity of the estimated second predetermined position. A reference direction determining unit that selects one appropriate direction as the reference direction from the n candidate directions by performing pattern matching on the second processing target image using the second template image. The reference direction determined by the reference direction determination unit, the position of the matching image determined by the pattern matching unit, and the reference position information, the measurement target in a state held in the wafer holding unit A reference position determination unit that determines the position of the reference point on the wafer; the reference direction determined by the reference direction determination unit; the position of the reference point determined by the reference position determination unit; and the measurement point position And a measurement position determining unit that determines the position of the measurement point on the measured wafer in a state held by the wafer holding unit from the information. Characteristic wafer measurement position determination device. 8. The measurement position determining apparatus for a wafer according to claim 7, wherein the first predetermined position is a center position of the measured wafer, and the second predetermined position is the measured wafer. A position on an outer edge of the wafer, wherein the second reference pattern is a notch formed on an outer edge of the wafer to be measured.