JP4313162B2 - Alignment mark detection method and inspection apparatus - Google Patents

Description

  The present invention relates to a method for recognizing the position of an inspection reference such as a substrate which is an inspection symmetry object of an inspection apparatus such as a line width measuring apparatus, and an inspection apparatus using the method.

  A conventional line width measurement method will be described with reference to FIG. FIG. 3 is a block diagram showing an example of the configuration of a conventional line width measuring apparatus.

  In line width measuring devices for measuring the width and spacing of thin films and thin film patterns formed on a substrate, and inspection devices for inspecting defects and flaws on a substrate, dimensional errors may occur on each measurement target substrate. Since there is a difference in pattern formation or the like, it is necessary to detect these errors before starting the inspection. For this reason, the position of a reference pattern, for example, an alignment mark or the like, generated in the same process as the pattern to be measured or simultaneously with the pattern to be measured is recognized. Then, by correcting the recognized inspection position with respect to the reference position of the apparatus, a normal inspection can be performed even if there is a deviation of the substrate or the like (see Patent Documents 1 and 2).

JP-A-8-222611 (page 5-6, FIG. 1) JP 2001-221628 A

  5A to 5F are examples of captured images of the alignment marks. Conventionally, as shown in FIG. 5 (b), an image within a broken line range 113 is used as a registered image 114. In the prior art, as shown in FIG. 5 (e) and FIG. 5 (f), when only a part of the alignment mark 111 (or 112) registered visually is visible, the alignment mark cannot be detected. Sometimes. This is because when an image that matches the registered image 114 at a predetermined rate is recognized (for example, the similarity between the registered image 114 and the luminance value for each pixel is 60% or more by a method such as pattern matching). This is because it has been detected. When the alignment mark cannot be detected at all or when only a part of the alignment mark can be detected, the detection device assumes that there is an alignment mark around the alignment mark, and searches for the periphery around the part, for example, in a spiral shape. First, the search is performed until a pattern having a shape matching the registered image 114 is found. This has the disadvantage of requiring a long search time.

One of the reasons that the alignment mark cannot be detected is that it is necessary to use a plurality of objective lenses having different magnifications. That is, in order to detect the alignment mark, a low-magnification objective lens may be used. However, the size of the inspection portion (for example, the line width of the circuit pattern) in the detection target is compared with that of the alignment mark. Since it is very small, it is necessary to switch to a high-magnification objective lens to obtain a corresponding magnification. In addition, if the magnification of the objective lens is wrongly selected, it takes time to correctly detect the alignment mark, and the search time as a whole increases, and the inspection time generally increases.
An object of the present invention is to provide a position detection method and an inspection apparatus that can detect the position of the alignment mark by solving the above-described problems and searching for an image of at least a part of the alignment mark. .

  In order to achieve the above object, in the method for recognizing the position of the inspection reference of the inspection object according to the present invention, the position of the alignment mark can be detected by recognizing a part of the captured image of the alignment mark. Features. Another feature is that the detection range of the alignment mark is substantially enlarged without changing the magnification of the microscope. This prevents the alignment mark from being undetectable on the inspection target substrate. In order to expand the detection range of the alignment mark, not only the pattern at the center of the alignment mark or the entire pattern is registered, but also the four or part of characteristic patterns of the alignment mark are registered respectively.

  Further, according to another aspect of the position recognition method of the present invention, in an inspection apparatus such as an automatic line width measuring apparatus that acquires and measures an enlarged image through a microscope, an image of a pattern at the substantially central portion of the alignment mark is obtained. While registering as a representative image, at least one of four patterns (periphery (edge) portion) or a partial pattern of the alignment mark is registered as a partial image. Then, by recognizing (detecting) an image that matches one of the registered representative image or partial image from the captured image of the inspection object, the magnification of the microscope is changed in the detection range of the alignment mark. In other words, it is possible to prevent the detection of the alignment mark without using the high-magnification inspection objective lens.

  That is, according to one aspect of the position recognition method of the present invention, a mounting table on which a substrate having a pattern and an alignment mark is placed, an imaging unit that images a predetermined portion of the substrate, and an image from the imaging unit In a pattern measuring apparatus including a signal processing unit that processes a signal and a control unit that controls the operation of the mounting table, the imaging unit captures a first alignment mark serving as a reference, and the captured first alignment mark Registering substantially the whole alignment mark and at least a part of the first alignment mark imaged, imaging the second alignment mark of the substrate to be measured by the imaging unit, and the imaged first The alignment mark of the first alignment mark registered with the alignment mark of 2 In which a step of detecting a first position of the second alignment marks on the basis of one of the alignment marks of at least a portion of the alignment mark of the alignment marks image.

According to another aspect of the position recognition method of the present invention, the imaging unit captures a third alignment mark at a position different from the reference first alignment mark, and the captured third The method includes a step of registering substantially the entire alignment mark and at least a part of the imaged third alignment mark.
According to another aspect of the position recognition method of the present invention, the imaging unit further includes a step of imaging a fourth alignment mark at a position different from the second alignment mark of the substrate to be measured; The position of the fourth alignment mark is detected on the basis of substantially the entire alignment mark of the third alignment mark registered as the alignment mark and at least a part of the imaged third alignment mark.
According to another aspect of the position recognition method of the present invention, the signal processing unit calculates the offset and inclination of the substrate to be measured based on the position measurement results of the second and fourth alignment marks, and the offset The position coordinates of the detected second and fourth alignment marks are corrected based on the inclination.

According to another aspect of the position recognition method of the present invention, at least one of the first alignment mark and the almost entire alignment mark of the registered first alignment mark and at least the first alignment mark imaged. In the step of detecting the position of the second alignment mark based on any one of some alignment marks, if the second alignment mark is not detected in any of the first alignment marks, a signal The processing unit outputs error information.
According to another aspect of the position recognition method of the present invention, at least one of the first alignment mark and the almost entire alignment mark of the registered first alignment mark and at least the first alignment mark imaged. The step of measuring the position of the second alignment mark based on any one of some alignment marks is performed using gray scale pattern matching.
According to another aspect of the position recognition method of the present invention, in the pattern detection method, the imaging unit further includes a first optical system and a second optical system with different magnifications, and the alignment mark is An image is picked up by the first optical system, and the wiring pattern is picked up by the second optical system.

  In addition, the pattern inspection apparatus of the present invention processes a video signal from the mounting table on which a pattern is formed and on which a substrate having an alignment mark is mounted, an imaging unit that images a predetermined portion of the substrate, and the imaging unit The image processing unit includes a signal processing unit, a storage unit that stores video data, and a control unit that adjusts a visual field range so that a predetermined portion of the substrate placed on the mounting table can be imaged by the imaging unit. The first alignment mark serving as the reference and the second alignment mark of the substrate to be measured are imaged, and substantially the entire alignment mark of the first alignment mark imaged in the storage unit is imaged. At least a part of the alignment marks is registered, and the signal processing unit registers the first alignment mark in which the imaged second alignment mark is registered. A function of detecting the position of the second alignment mark based on any one of the alignment marks of substantially the entire alignment mark and at least a part of the first alignment mark imaged. .

According to another aspect of the pattern inspection apparatus of the present invention, the control unit for adjusting the visual field range moves the reference substrate, and the imaging unit is located at a position different from the first alignment mark as the reference. Having a function of imaging the third alignment mark, and registering at least a part of the imaged third alignment mark and at least a part of the imaged third alignment mark in the storage unit It is.
In addition, according to another aspect of the pattern inspection apparatus of the present invention, the imaging unit further has a function of imaging a fourth alignment mark at a position different from the second alignment mark of the substrate to be measured, The signal processing unit uses the fourth alignment mark based on substantially the entire alignment mark of the third alignment mark registered in the storage unit and at least a part of the imaged third alignment mark. It has a function of detecting the position of the alignment mark.
According to another aspect of the pattern inspection apparatus of the present invention, the signal processing unit calculates the offset and inclination of the substrate to be measured based on the position detection results of the second and fourth alignment marks, and the offset It has a function of correcting the position coordinates of the substrate to be measured based on the value.

According to another aspect of the pattern inspection apparatus of the present invention, at least one of the first alignment mark and the entire alignment mark of the registered first alignment mark and at least the first alignment mark that has been imaged are registered. When the position of the second alignment mark is detected based on any one of some alignment marks, signal processing is performed when the second alignment mark is not detected in any of the first alignment marks. The section outputs error information.
According to another aspect of the pattern inspection apparatus of the present invention, at least one of the first alignment mark and the entire alignment mark of the registered first alignment mark and at least the first alignment mark that has been imaged are registered. When detecting the position of the second alignment mark based on any one of some alignment marks, the signal processing unit performs pattern matching using grayscale pattern matching.
According to another aspect of the pattern inspection apparatus of the present invention, the imaging unit further includes a first optical system and a second optical system having different magnifications, and the alignment mark is the first optical system. An image is taken and the wiring pattern is taken by the second optical system.
According to another aspect of the pattern inspection apparatus of the present invention, the magnification of the second optical system is larger than the magnification of the first optical system.

According to still another aspect of the position recognition method of the present invention, the present invention can be used for inspection of the line width of a substrate or the like. In general, line width inspection apparatuses often use image recognition and image processing techniques to inspect or measure the line width and line spacing of circuit patterns or circuit element patterns. The position recognition method of the present invention can realize the position recognition of the alignment mark by using a known method similar to the image recognition and image processing used at the time of line width inspection. Therefore, it is not necessary to add new hardware only to recognize the alignment mark.
Further, the conventional position recognition apparatus uses a mechanism for performing a search until an entire image of the alignment mark is found as described above when no alignment mark is found. On the other hand, in the present invention, since the position of the alignment mark can be detected only by recognizing a partial image of the alignment mark, the range of position recognition can be substantially expanded. Therefore, such a mechanism of the prior art becomes unnecessary.

As described above, according to the present invention, it is possible to greatly expand the detection range by registering a partial image of a part of the representative image in addition to the representative image.
Further, even if the alignment mark is large, the detectable range can be widened.
Furthermore, the objective lens used for alignment image recognition can be used at as high a magnification as possible, and the XY position recognition error can be reduced when shifting to a higher inspection magnification.
Furthermore, the focal depth of the objective lens needs to be detected in a wide range when the objective lens is shifted to a high magnification. However, since it is sufficient to detect the focus in a narrower range than before, the focus detection time can be shortened. It became possible.
Furthermore, generally, it is necessary to use a low-magnification preliminary objective lens to recognize the alignment mark, and to inspect an inspection object, it is necessary to use a high-magnification inspection objective lens.
Conventionally, it has been necessary to inspect an inspection point (for example, line width) of an inspection object after recognizing an alignment mark using a low-power preliminary objective lens and then changing to a high-power inspection objective lens. . However, in the present invention, the alignment mark can be recognized only by using a high-power inspection objective lens (for inspecting an object to be inspected). After recognizing the alignment mark, the line width of the object to be inspected can be inspected immediately without changing the magnification of the objective lens as in the prior art. Therefore, the time required for the inspection could be greatly shortened. Although the position recognition method of the present invention has been described using a line width measuring apparatus, it can also be applied to other apparatuses (for example, a semiconductor stepper apparatus).

Embodiments of a position recognition method for recognizing the position of an inspection reference on an inspection object according to the present invention and an inspection apparatus using the method will be described below.
The operation of the line width measuring apparatus will be described with reference to FIGS.
In the line width measuring device, for example, a projection image of a measurement object (measurement object) projected by an optical microscope is captured by a video camera (for example, a CCD camera) or the like, and the dimension of a desired portion is measured by a dimension measurement processing unit. In some cases, an image of the object to be measured and a dimension measuring device are displayed on a video monitor.
FIG. 8 is a view showing a display example of the screen of the video monitor during the dimension measurement, and L1, L2, and Li respectively indicate scanning lines. As shown in FIG. 8, the luminance distribution on one horizontal scanning line Li in the monitor image 55 of the measured object captured by the video camera is the luminance of each pixel position obtained by N-decomposing the corresponding video signal on the scanning line Li. Thus, a luminance one-pixel characteristic is obtained. This luminance-one-pixel characteristic is shown in FIG. In FIG. 9, the vertical axis represents luminance, and the horizontal axis represents pixels. As a conventional countermeasure, the dimension is obtained from this characteristic. In FIG. 9, the maximum luminance level 51 in the luminance distribution is set to 100%, and the minimum luminance level 52 is set to 0%. The position difference Nab between the a-th pixel and the b-th pixel corresponding to the 50% luminance level Vs 153 is obtained. Multiplying this position difference Nab by a factor k determined by the measurement magnification of the microscope at this time and the object distance from the video camera to the object to be measured, the dimension value X = K × Nab of the corresponding object is obtained. .
Such a method for recognizing an image is disclosed in, for example, USP 6,571,196, and is called gray scale pattern matching. In the luminance-one-pixel characteristic, the number of N may be equal to the number of pixels.

The image registration method and recognition method in the present invention will be described below.
FIG. 3 is a configuration diagram of an example of a line width measuring apparatus to which the present invention is applied.
The object to be inspected (SUBJECT TO BE INSPECTED) 1 is fixed by adsorbing the back surface with a substrate clamp stand (SUBSTRATE CLAMP STAND) 2. The substrate clamp table 2 is on a Y-axis moving stage 4 and an X-axis moving stage (X-AXIS MOVING STAGE) 3 arranged on the fixed table 5. The inspection object 1 consists of an X-axis movement stage 3 and a Y-axis movement stage (Y-AXIS MOVING STAGE) 4 via an XY movement control unit (XY MOVEMENT CONTROL UNIT) 7 in the X-axis direction and the Y-axis direction, respectively. By moving it, it can be moved in a plane, and an arbitrary position in the inspection object 1 can be observed with an optical microscope (OPTICAL MICROSCOPE) 8. The X-axis movement stage 3 and the Y-axis movement stage 4 are each operated according to a program in a CPU unit 163, which will be described later, manually or previously registered by the measurement control unit 16.
In FIG. 3, an inspection object 1 is a substrate used for an FPD (Flat Panel Display) such as a semiconductor wafer, LCD (Liquid Crystal Device), PDP (Plasma Display Panel), or the like. For example, in the case of an automatic line width measuring device, the inspection location is an electrode pattern, a wiring pattern, or an insulating layer pattern formed on a substrate such as a substrate wafer, and measures the pattern line width and pattern interval.

  The illumination power supply (ILLUMINATING POWER SUPPLY) 6 is configured to introduce light into the optical microscope 8 by a light guide (LIGHT GUIDE) 9. The light is projected onto the inspection object 1 through the inspection objective lens 11. The projected light is incident on the image sensor 15 via the inspection object 1 and the intermediate lens 14. The image sensor 15 converts incident light into an electrical signal and outputs it to a measurement control unit (MEASUREMENT CONTROL UNIT) 16. The imaging element 15 is a CCD camera or the like that can convert light such as visible light, infrared light, ultraviolet light, and X-rays into an electrical signal.

The magnification changing mechanism (revolver: CHANGE MECHANISM) 10 replaces the inspection objective lens (INSPECTION OBJECTIVE LENS) 11 with another objective lens (preliminary objective lens: PRELIMINARY OBJECTIVE LENS) 12 having a different magnification according to the purpose. The inspection objective lens 11 is mainly used for inspection of line width and the like. The preliminary objective lens 12 having a lower magnification than the inspection objective lens 11 is mainly used for recognizing and detecting the alignment mark. The optical axis (Z-axis) moving stage (OPTICAL AXIS MOVING STAGE) 13 moves the entire optical microscope 8 equipped with the inspection objective lens 11 in the direction of the optical axis (Z-axis) for focusing. The intermediate lens (INTERMEDIATE LENS) 14 enlarges the image from the inspection objective lens 11 and projects it onto the CCD camera 15. The image captured by the CCD camera (CCD CAMERA) 15 is input to an image capturing / display unit (IMAGE FETCH / DISPLAY UNIT) 161 in the measurement control unit (inspection control unit) 16.
The user gives an instruction to the device to the CPU unit 163 through the input unit (INPUT UNIT) 164.

  The optical axis (Z-axis) movement / autofocus control unit (OPTICAL AXIS MOVEMENT / AUTO-FOCUS CONTROL UNIT) 162 is used to light the entire optical microscope 8 equipped with the inspection objective lens 11 in order to adjust the focal length of the inspection objective lens 11. It is a control unit for moving in the direction of the axis (Z axis). The CPU 163 includes a program that executes the entire control. A video monitor (DISPLAY UNIT) 17 that is a display device displays images such as inspection points and alignment marks, and operation switches that operate in a GUI (Graphical User Interface) environment.

As shown in FIG. 4, the registration method of the inspection position coordinates will be described by showing the positional relationship between the inspection object 1 and the inside of the object. In FIG. 4, an arbitrary one is selected from the inspection objects 1 and described as a substrate 1.
In an inspection device such as an automatic line width measurement device, the measurement values or design values of the position coordinates 121 to 128 on the substrate 1 to be inspected are registered in advance with the X-direction reference surface 101 and the Y-direction reference surface 102 of the substrate 1 as a reference. The position coordinates are sequentially read out when inspecting the substrate that is the inspection object 1, and the inspection is performed with the registered coordinates. Here, even if the substrate to be inspected is the substrate used at the time of registration, if it is set again in the apparatus, it will be misaligned with the origin (reference coordinates) of the apparatus. It is necessary to correct the inspection position. In FIG. 4, the upper left corner is the reference coordinate (X ₀ , Y ₀ ).
This will be described in more detail below.

First, one arbitrary inspection board is selected, and the coordinates of the alignment mark and each inspection coordinate are registered in the following procedure. This inspection substrate may be a standard substrate prepared in advance or any one substrate in each production lot. In this example, the substrate has two left and right alignment marks. However, the present invention can be applied to a substrate having an arbitrary number of alignment marks.
That is, the installation positions of the X-direction reference surface 101 and the Y-direction reference surface 102 of the substrate 1 are fixed by contact of the X-direction fixing roller 201, the X-direction fixing roller 202, and the Y-direction fixing roller 211.
In this state, the back surface of the substrate 1 is sucked and held, and the substrate pressing of the X-direction pressing rollers 203 and 204 and the Y-direction pressing roller 212 is released. The X-direction fixed rollers 201 and 202 and the Y-direction fixed roller 211 can be fixed or retracted to the outside, but are held with a force that does not lose the force of the pressing rollers 203, 204, and 212.
In this state, the positions of the left alignment mark 111 and the right alignment mark 112 are observed by the inspection objective lens 11, and the XY coordinates and detection images of the XY stage on the detection side of the alignment marks 111 and 112 are registered by the CPU unit 163. .

Next, the position coordinates (position coordinates of inspection points) S ₁₂₁ to S ₁₂₈ to be inspected are registered in the following procedure in the same manner as the left alignment mark 111 and the right alignment mark 112 described above.
For example, the tolerances of the distance from the reference plane 101 and the Y-direction reference plane 102 to the left alignment mark 111 and the right alignment mark 112 by the method of the substrate 1 in the X direction are each within ± 0.1 mm. If an optical microscope with an intermediate lens 14 magnification of 3.3 is used and an inspection objective lens 11 with a magnification of 5 is used, the optical magnification is 5 × 3.3 = 16.5 times. When a CCD camera 15 with a CCD camera size of 6 mm square is used, the field of view of the CCD camera 15 is
The range is 6 mm ÷ 16.5 times = 0.36 mm.
The error in the distance from the reference planes 101 and 102 in the X and Y directions of the substrate 1 to the left alignment mark 111 and the error in the distance to the right alignment mark 112 are ± 0.1 mm. Can do.
After registering the alignment mark and the position coordinates to be inspected, return the board 1 from the board clamp base 2 to the storage location. Then, the next substrate to be inspected is set on the substrate clamp table. An imaging part images the predetermined location of a board | substrate. The signal processing unit processes the video signal from the imaging unit. The storage unit stores video signal data. The control unit controls the operation of the inspection apparatus. An alignment mark is detected by image processing, and information (offset and inclination) of the difference from the registered alignment mark is calculated. The inspection is performed by correcting the position coordinates of the detected portion.

In other words, after detecting the left alignment mark 111 and the right alignment mark 112 for the substrate to be inspected, the inclination and offset of the substrate 1 are recalculated. Inspected more locations (inspection point) coordinates of S ₁₂₁ ~ S inspection points S ₁₂₁ after the correction from the position coordinate value of ₁₂₈ ~ S ₁₂₈ (hereinafter, referred to as the test position coordinates) movement to the, X-axis moving stage 3, This can be done within several μm, which is the error of each Y-axis moving stage 4. In other words, 50 times can be used as the magnification of the inspection objective lens 11. In this case, the field of view is 6 mm ÷ (50 times × 3.3 times) = 36 μm. Therefore, since the error is only a few μm, there is always an inspection point within the field of view of 36 μm, so a reliable inspection can be performed.

Next, an image registration method and an image detection method for the left alignment mark 111 and the right alignment mark 112 will be described more specifically with reference to FIGS. 1 (b) to (g) and FIGS. 5 (a) to (f). explain.
(1) Image Registration Method First, a method for registering a representative image (here, the central image) of the alignment mark image will be described.
Operate the XY movement control unit 7 (referred to as XY remote) to move the left alignment mark 111 on the substrate 1 using the X-axis movement stage 3 and the Y-axis movement stage 4 and bring it into the imaging field of the CCD camera 15 Put in. That is, the image of the alignment mark 111 is placed in the monitor screen of the video monitor 17.
Next, the optical axis movement / autofocus control unit 162 is manually operated (referred to as Z manual remote) and moved using the Z axis movement stage 13 to focus.
As described above, as shown in FIG. 1 (b) and FIG. 5 (b), the left alignment mark 111 is imaged so as to be in the center of the screen, and a dashed mark frame (dashed line) displayed on the screen at the time of registration is displayed. (Range) 113 is selected by operating a GUI using an input device, for example, a mouse. The broken line mark frame 113 is dragged with the mouse, the center of the broken line mark frame 113 is aligned with the center of the image of the left alignment mark 111, and a registration button (not shown) displayed on the screen is pressed. Furthermore, when it is desired to change the size of the broken-line mark frame 113, it can be changed by selecting and dragging the frame out of the mouse. Note that an image may be selected by a method of forming a frame on the screen. As a result, the image within the broken line range 113 is registered as the registered image 114. Further, the center of the broken line range 113 is the center coordinate of the registered image.

Next, press the position coordinate recognition button (not shown) displayed on the screen of the video monitor 17 during registration, and set the center position coordinates (XY coordinates (X, Y)) of the alignment mark 111 to AL1 (X, Y) = to register as (Xs _1, Ys _1). Here, (Xs, Ys), the position coordinates relative to the reference coordinates of the substrate of FIG. 4 (X _0, Y ₀₎ is a XY stage coordinates.
Through the above processing, the image at the center of the alignment mark 111 is registered as a representative image.
On the other hand, the entire image of the alignment mark 111 (see FIG. 1G) may be registered as a representative image.

Next, as shown in FIG. 1 (c), drag the broken mark frame 113 to align it with the corner of the alignment mark 111 (for example, the lower right lower part). Similarly, only the lower right image of the alignment mark 111 is registered. (Fig. 1 (c) Inside the lined frame). This is a registered image (partial image) 114-1. Next, as shown in FIG. 1D, only the upper right image of the left alignment mark 111 is registered (FIG. 1D). This is registered image (partial image) 114-2. Next, as shown in FIG. 1 (e), only the lower left image of the left alignment mark 111 is registered. This is designated as a registered image (partial image) 114-3 (FIG. 1 (e) in a broken line frame). Next, as shown in FIG. 1 (f), only the upper left image of the left alignment mark 111 is registered. This is designated as a registered image (partial image) 114-4 (FIG. 1 (f) in a broken line frame).
Similarly, for the right alignment mark 112, the same images (representative images and partial images) as in FIGS. 1A and 1C to 1F are registered. However, if the pattern of the right alignment mark 112 is similar to that of the left alignment mark 111, registration of the image can be omitted by registering the position coordinates.

The right alignment mark 112 is registered in the same manner as described above. Then, the registration center position coordinates of the alignment marks 112 (XY coordinates (X, Y)) of AL2 (X, Y) = a (Xs _2, Ys _2).
Further, partial registration of each part of the broken-line mark frame 113 is performed in the same manner. Similar to the alignment marks described above, the position coordinates of each detection location are registered. In other words, after moving to the vicinity of the detection location by manual remote operation and focusing, the mark (not shown) displayed on the screen during registration is dragged with the mouse to match the detection location and displayed on the screen during registration Press the coordinate recognition button (not shown). Thereby, the coordinates of the mark position become the registered position coordinates. To the registered order, for example, inspection position coordinates _{S 121 (X 121, Y 121} ) of FIG. _{4, S 122 (X 122,} Y 122), ‥‥‥, registered as _{S 128 (X 128, Y 128} ) The

(2) Image Detection Unit Next, a method for detecting an image at each inspection location will be described.
First, fixed rollers 201 and 202 on the X-direction reference surface of substrate 1 and fixed roller 211 on the Y-direction reference surface are moved to fixed positions, and substrate 1 is moved by X-direction pressing rollers 203 and 204 and Y-direction pressing roller 212. Press down.
Next, the substrate 1 is sucked and held. Thereafter, the X direction pressing rollers 203 and 204 and the Y direction pressing roller 212 are released from the pressing of the substrate 1. Further, the fixed roller 201 and the fixed roller 202 on the substrate reference surface side and the fixed roller 211 on the Y-direction reference surface are moved to a fixed position and are avoided.

The entire screen is auto-focused at the alignment mark position coordinate AL1 (X, Y).
Due to the dimensional variation of the substrate 1, for example, as shown in FIG. 5C, an image deviated from the center position coordinate where the alignment mark is registered may be obtained. In such a case. Drift correction as shown below is performed.
First, this image is recognized, and the left alignment mark coordinate position AL1 (X ₁ , Y ₁ ) of this inspection target substrate is obtained.
Next, at the alignment mark coordinate position AL2 (X, Y), the entire screen is auto-focused, and an image in which the alignment mark is displaced as shown in FIG. May be obtained. The image recognize, to obtain the right alignment mark coordinate position of the inspection target board _{AL2 (X 2, Y 2)} .

From AL1R and AL2R, a slope θR and an offset OFR (X, Y) with respect to the position coordinates of a registered image to be described later are obtained.
For example, registered in inclination 0 and offset 0, the test position coordinates _{S 121 (X 121, Y 121} ), S 122 (X 122, Y 122), ‥‥‥, the slope of the _{S 128 (X 128, Y 128} ) The inspection position coordinates S _121R (X _121R , Y _121R ), S _122R (X _122R , Y _122R ),..., S 128R are corrected with the previously obtained θR and offset OFR (X, Y) _. (X _128R, Y _128R) is calculated, detecting an inspection position S ₁₂₁ ~ S _128. Based on these detected detection positions, the inspection point is moved to the inspection location.
Then it moved to the inspection position S _122, the check the inspection point, to inspect all registered inspection point moves similarly sequentially from the inspection position S ₁₂₂ to the inspection position S _128.

(2) Image detection method As described in the above description of the image registration method, the substrate 1 is fixed to the substrate clamp base 2 by the fixing rollers 201, 202, 211, the pressing rollers 203, 204, 212, etc. Adsorb and hold.
Next, move to the left alignment mark registration position coordinate AL1 (X, Y), and auto-focus the entire screen to focus.
It is assumed that an image in which the alignment mark is shifted from the center of the screen is obtained due to the variation of the substrate 1, for example, as in the screen of FIG. At this time, the detected image may be the case shown in FIG. 2 (a), FIG. 2 (c) to FIG. 2 (e), or the case where no alignment mark is detected (not shown).
In the present invention, even in such a case, by registering a partial image in addition to the representative image as described above, it is possible to detect the alignment mark even when only a part of the alignment mark enters the field of view. To do.

By using an image and the flowchart of FIG. 7 in FIG. 2 (a) ~ (f) , will be described further how the detection in detail. FIG. 7 is a flowchart showing the processing of one embodiment of the position recognition method of the present invention, which is executed according to the program in the CPU unit 163.
In step 1001, it is determined whether detection of the left alignment mark has been completed. If the detection is completed, the process proceeds to step 1017. If the detection is not performed, the process proceeds to step 1011.
Next, image recognition of the left alignment mark is performed. Here, as a method for recognizing the alignment mark, for example, gray scale pattern matching disclosed in US Pat. No. 6,571,196 is used. The procedure for obtaining the coordinates of the left alignment mark 111 will be described in the following steps 1011 to 1017.
In step 1011, it is determined whether or not the entire alignment mark image 114 has been detected. If the whole is detected, go to step 1017. If not, go to step 1012.

  The following steps are similar. That is, in step 1012, it is determined whether or not the alignment mark image 114 has been detected. If the alignment mark image 114-1 is detected, the process proceeds to step 1017. If the alignment mark image 114-1 is not detected, the process proceeds to step 1013.

In step 1013, it is determined whether or not the alignment mark image 114-2 has been detected. If the alignment mark image 114-2 is detected, the process proceeds to step 1017. If the alignment mark image 114-2 is not detected, the process proceeds to step 1014.
In step 1014, it is determined whether or not the alignment mark image 114-3 has been detected. If the alignment mark image 114-3 is detected, the process proceeds to step 1017. If the alignment mark image 114-3 is not detected, the process proceeds to step 1015.
In step 1015, it is determined whether or not the alignment mark image 114-4 has been detected. If the alignment mark image 114-4 is detected, the process proceeds to step 1017. If the alignment mark image 114-4 is not detected, the detection has failed and the process proceeds to step 1016.

In step 1016, the operator is notified of the failure in detecting the left alignment mark by displaying an alarm on the monitor screen or outputting an alarm sound, etc., and the process is interrupted. This step informs the user that the alignment mark was not within a certain error range. In this case, it can also be assumed that the alignment mark is not within the range of the inspection standard. That is, this substrate can be detected as a defective product.
In step 1017, position coordinates are recognized (that is, position coordinates AL1 (X, Y)) are obtained from the detected image (114, 114-1, 114-2, 114-3, 114-4). ) Proceed to step 1018 and proceed to the next right alignment mark recognition process.

  Next, the right alignment mark is recognized in the same manner to obtain the position coordinate AL2 (X, Y). That is, in step 1018, it is confirmed whether or not the position coordinates of both the left and right alignment marks have been calculated. If the position coordinate of the right alignment mark has not been calculated, in step 1019, the same processing as in step 1001 is performed to recognize the right alignment mark. Thereafter, as described above, the right alignment mark is recognized and detected, and the position coordinates are calculated.

Through the above recognition operation, the actual positions of the left alignment mark and the right alignment mark on the substrate are recognized. Thereby, the relative coordinate error of the board relative to the board registered first can be known. Therefore, the position of each inspection coordinate can also be calculated based on these coordinate errors. For example, the inclination θR and the offset OFR (X, Y) are obtained from the position coordinates AL1 (X, Y) and AL2 (X, Y). Here, the inclination θR indicates the inclination between AL1 (X, Y) and AL2 (X, Y), and the offset OFR (X, Y) indicates the difference between AL1 (X, Y) and the registered coordinates. Show (step 1020).
Inspection positions S ₁₂₁ (X ₁₂₁ , Y ₁₂₁ ), S ₁₂₂ (X ₁₂₂ , Y ₁₂₂ ), ..., S ₁₂₈ (X ₁₂₈ , Y ₁₂₈ ) registered with the inclination 0 and the offset 0 at the time of registration and modified in inclination θR and offset OFR (X, Y), corrected inspection position coordinates _{S 121R (X 121R, Y 121R} ), S 122R (X 122R, Y 122R), ‥‥‥, S 128R (X _128R , _Y128R ) is calculated (step 1021).
Thereafter, the inspection point on the corrected correct inspection position S ₁₂₁ (X ₁₂₁ , Y ₁₂₁ ) is inspected. Next, the inspection point on the correct correct S ₁₂₂ (X ₁₂₂ , Y ₁₂₂ ) is inspected, and the inspection is performed in the same manner to the inspection point on the inspection position S ₁₂₈ (X ₁₂₈ , Y ₁₂₈ ). .

Next, it is verified how much the detection range of the alignment mark has been improved by the present invention.
First, in the conventional detection range shown in FIG.
Screen field of view 0.36 mm
The alignment mark detection range is 0.16 mm.
Therefore, the detectable range is
Detectable range = screen field of view-detection range
= 0.36 -0.16
= 0.2 mm.

In the detection range of the present invention shown in FIG.
Screen field of view 0.36 mm
The alignment mark detection range is 0.16 mm.
Therefore, the detectable range is
Detectable range = screen field of view + detection range
= 0.36 + 0.16
= 0.51 mm.
Therefore, by carrying out the present invention, the detection range per direction is changed from 0.2 mm to 0.51 mm, which is about 2.5 times larger.

Conventionally, the detection range is narrow when the alignment mark detection range is wide (the alignment mark is large). However, in the present invention, when the distance between the alignment mark detection ranges is long (the alignment mark is large), the detection range is wide. There are advantages you can do.
In addition, the objective lens used for image recognition of alignment marks can be used at as high a magnification as possible (using a magnification of 2.5 to expand the field of view without expanding the field of view at 5 times), and when shifting to a higher inspection magnification (50 times) , XY position recognition error can be reduced.

The depth of focus of the objective lens is
100 μm at 2.5x inspection magnification
5 times 20 μm
50 times is 1 μm.
If the inspection magnification is 2.5, it is necessary to detect the focal point (center coordinate) in the range of 100 μm. However, when the inspection magnification is shifted from 2.5 times to 50 times, the focus of the alignment mark may be detected within the range of 20 μm. Therefore, the focus detection time of the alignment mark can be shortened by the narrow focus detection range.

In the above-described embodiment, the operator is burdened with five registration operations for the registration operation of one alignment mark. In order to solve this problem, an area can be set in advance and can be automatically recognized.
Hereinafter, an embodiment of the method will be described with reference to FIGS. 1 (c) to 1 (f).
First, the moving distances m1 to m4 and the area ranges a1 to a4 are determined. Next, it is possible to automatically register the other four points simply by designating the entire registered image (representative image) 114. That is, the following procedure is performed.
(1) The registered image (partial image) 114-1 moves to the lower right by a predetermined distance m1, and the area is set to a predetermined range a1. Thereafter, the procedure is repeated in the same manner.
(2) The registered image (partial image) 114-2 moves to the upper right by m2 and the area is a2.
(3) The registered image (partial image) 114-3 moves to the lower left by m3, and the area is a3.
(4) The registered image (partial image) 114-4 moves to the upper left by m4, and the area is a4.
Note that m1 to m4 are arbitrary lengths and may be all equal.
The number of representative images and partial images can be arbitrarily set, and the moving direction, moving distance, and area range can be individually set for each of the registered images 114-1 to 114-4.
In order to save the registration time, registration data of a plurality of images may be stored in a medium such as a flexible disk and read when necessary.

The figure for demonstrating one Example of this invention. The figure for demonstrating one Example of this invention. The block diagram which shows an example of a structure of the conventional line | wire width measuring apparatus. The figure for demonstrating the positional relationship inside a test target object and its inside. The figure for demonstrating the image registration means and image detection means of the conventional alignment mark. The figure for demonstrating the difference with the past and this invention. The flowchart which shows the process of one Example of the position recognition method of this invention. The figure for demonstrating an example of the conventional line width measuring method in a line width measuring apparatus. The figure which showed the data obtained by the line | wire width measurement of FIG.

Explanation of symbols

1: inspection object, 2: substrate clamp table, 3: X axis movement stage, 4: Y axis movement stage, 5: vibration isolation table, 6: illumination power supply, 7: XY movement control unit, 8: optical microscope, 9 : Light guide, 10: Variable magnification mechanism (revolver), 11: Inspection objective lens , 12: Preliminary objective lens, 13: Optical axis (Z-axis) moving stage, 14: Intermediate lens, 15: CCD camera, 16: Measurement control (Inspection control unit), 161: image capture / display unit, 162: optical axis (Z-axis) movement / autofocus control unit, 163: CPU and program, 17: CRT, 101: X-direction reference plane, 102: Y direction reference plane, 111, 112: an alignment mark, 113: mark frame, 114 :, S ₁₂₁ ~ S ₁₂₈ : Inspection location, 201: X direction fixed roller A, 202: X direction fixed roller B, 203: X direction pressing roller A, 204: X direction pressing roller B, 212: Y direction pressing roller, 111: Left alignment Mark, 112: Right alignment mark .

Claims (4)

A mounting table on which a substrate on which a pattern is formed is mounted; an optical microscope that enlarges a predetermined portion of the substrate to a first magnification; an imaging unit that images the enlarged predetermined portion; A signal processing unit that processes the video signal and a control unit that controls the operation of the mounting table. The representative image and partial image of an arbitrary number of alignment marks and the position coordinates of the inspection location are registered in advance, and the first In the alignment mark detection method of the inspection apparatus that inspects the inspection location at a magnification of
Capturing a representative image of the alignment mark at a registered position coordinate;
Detecting a representative image of the alignment mark from the picked-up video signal, and detecting a partial image of the alignment mark from the picked-up video signal if a representative image of the alignment mark is not detected And a step of recognizing position coordinates from the detected partial image . 2. The alignment mark detection method according to claim 1, wherein the step of moving to the position coordinates where the representative image of the alignment mark is registered and taking the image is enlarged to the first magnification for inspecting the inspection location. An alignment mark detection method characterized by the above. A mounting table on which a substrate on which a pattern is formed is mounted; an optical microscope that enlarges a predetermined portion of the substrate to a first magnification; an imaging unit that images the enlarged predetermined portion; A signal processing unit for processing a video signal, a storage unit for storing data of the video signal, a representative image and a partial image of an arbitrary number of alignment marks registered in advance , and the imaging unit with position coordinates of an inspection location In the inspection apparatus for inspecting the inspection location at the first magnification, comprising a control unit that can image an arbitrary position of the substrate,
The control unit is operated so that the optical microscope can be imaged at a second magnification at a pre-registered position coordinate of the representative image of the alignment mark,
From the data of the video signal which the imaging unit is imaging, detecting a representative image of the alignment mark, if the above alignment mark of the representative image is not detected, the portion of the alignment mark from the data of the captured video signal detecting the image, inspection apparatus and recognizes the position coordinates at the detected partial images.   4. The inspection apparatus according to claim 3, wherein the control unit has the same magnification as the second magnification and the first magnification.

Images