JPH10260366A - Pattern inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce inspection errors such as a size measurement error in the case of a fine pattern by evaluating image contrast at an inspection object position and deciding the position where the image contrast becomes maximum as a focusing point. SOLUTION: An image of a sample 16 is formed at an image pickup part 12 by an image forming means 13 consisting of an objective 14 and various optical elements of a mictoscope device. The image signal picked up by the image pickup part 12 is sent to an image processor 1 and passed to respective processing parts 3 to 6 after being passed through an input-stage processing part 2. An object-sample distance control part 7 controls the operation of an object-sample distance variation part 15 of the microscope device. A contrast detection part 5 is equipped with a distance table, and detects, evaluates, and hold contrast information at each operation position at the time of the focusing operation of the object-sample distance variation part 15 and also determines the position of the objective 14 where the largest contrast, i.e. focusing position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection apparatus, and more particularly to a pattern inspection apparatus having a feature in a focusing system at a position to be inspected.

[0002]

2. Description of the Related Art With the development of semiconductor technology in recent years, patterns formed on silicon wafers and quartz substrates for liquid crystals have become increasingly finer. Along with this, it is important to reliably detect the fine structure with high accuracy in a device inspection process.

In an inspection process of semiconductor manufacturing, a pattern inspection apparatus that processes an image captured by an imaging unit of a microscope and measures a minute dimension is widely used. In order to detect the above microstructure reliably and with high accuracy, it is necessary to surely focus on a position to be inspected and, if the inspection is a dimensional measurement, a measurement site.

Generally, in such an inspection apparatus, a means for adjusting the distance to the specimen and an image forming means are connected to the image processing section, and the whole or fixed area within the image is fixed based on the processing of the image processing section. The distance between the specimen and the imaging means is adjusted so that the contrast in the partial range is maximized. In another focusing method, a laser is used to focus on a specific spot in an image.

[0005]

However, focusing means using a laser or a focusing means for maximizing the contrast of the entire surface or a predetermined range in the above-mentioned image, in particular, requires the measurement site itself to be measured having a very small size. Not in focus.

[0006] Even in the conventional focusing method, focusing is ensured in the entire image or in the vicinity of a predetermined range. However, focusing on the entire image does not always completely focus the measurement site in the image. In addition, as described above, in response to further miniaturization of the pattern, reliable and high In order to realize accurate focusing, the degree of focusing may not always be sufficient in the conventional method.

That is, in many cases, since the contrast evaluation portion at the time of focusing does not correspond one-to-one with the portion to be measured, there is a case where the measurement portion is not sufficiently focused at the dimension measurement with a minute pattern. , Causing an error.

The present invention has been made in view of such circumstances, and provides a pattern inspection apparatus which ensures the focusing at the inspection target position and has few inspection errors such as a dimensional measurement error in a minute pattern. The purpose is to do.

[0009]

According to a first aspect of the present invention, there is provided a pattern inspection apparatus for inspecting a position of an inspection object by focusing on the sample. Imaging means for projecting a specimen image onto the imaging means; position adjusting means for adjusting the distance between the imaging means and the specimen; and the imaging means for detecting a position specifying shape in the captured image. The distance between the imaging means and the sample is changed by the image processing means, the inspection target specifying means for specifying the inspection target position based on the position of the position specifying shape detected by the image processing means, and the position adjusting means. And a focus position detection unit that evaluates the image contrast at the position to be inspected in (1) and sets the position where the image contrast is the maximum as the focus position.

A second aspect of the present invention is the invention according to the first aspect, wherein the position adjusting means evaluates the image contrast at the position to be inspected.
This is a pattern inspection apparatus that specifies an inspection target position by an inspection target specifying unit every time the distance between samples is changed.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the distance between the imaging means and the sample is determined by the position adjustment means when the focus position is detected by the focus position detection means. This is a pattern inspection apparatus in which a change is started from a shortest distance or a maximum distance, and the distance is sequentially increased or shortened, and a position immediately before a position where image contrast is reduced is set as a focus position. (Operation) Therefore, in the pattern inspection apparatus according to the first aspect of the present invention, the position specifying shape is detected by the image processing unit in the image captured by the imaging unit. As the position specifying shape, a shape in which the image in the sample is easily recognized is previously selected and set.

Further, the inspection target position is specified by the inspection target specifying means based on the detected position of the position specifying shape. The distance between the imaging means and the sample is sequentially changed by the position adjusting means in accordance with a command from the in-focus position detecting means, images at each distance are captured, and the image contrast at the inspection target position is evaluated. Then, the position where the image contrast becomes maximum is set as the focus position.

In the present invention, the specimen is inspected by focusing on the specimen at the in-focus position, so that the in-focus at the inspected position is reliably ensured, and the inspection such as a dimensional measurement error in a minute pattern is performed. A pattern inspection apparatus with few errors can be provided.

Next, the pattern inspection apparatus according to the second aspect of the present invention operates in the same manner as the first aspect of the invention, and furthermore, when evaluating the image contrast at the inspection target position, the distance by the position adjusting means. Each time the change is made, the position to be inspected is specified.

Therefore, for example, even when the moving axis of the position adjusting means is inclined and there is a slight shift in the captured image every time the distance is changed, it is possible to reliably perform the image contrast evaluation at the inspection target position.

Further, the pattern inspection apparatus according to the third aspect of the present invention operates in the same manner as the first or second aspect of the present invention.
The distance between the samples is changed from the shortest distance or the maximum distance, and the distance is sequentially increased or shortened, and the position immediately before the position where the image contrast is reduced is set as the focus position.
Therefore, the in-focus position can be detected with the minimum number of movements.

[0017]

Embodiments of the present invention will be described below. (First Embodiment of the Invention) FIG. 1 is a configuration diagram showing an example of a pattern inspection apparatus according to an embodiment of the present invention.

This pattern inspection apparatus includes a sample setting section (not shown), an image pickup section 12, an image forming means 13, and an objective-sample distance movable section 15 which are configured so that a sample 16 can be set.
And an image processing apparatus 1 that processes an imaging result and controls the microscope apparatus. Here, the image processing apparatus 1 reads a program recorded on a recording medium such as a magnetic disk, and
It is realized by a computer whose operation is controlled by this program.

An image of the specimen 16 is formed on the image pickup section 12 by an image forming means 13 comprising an objective lens 14 of a microscope device and various optical elements. The image signal captured by the imaging unit 12 is sent to the image processing device 1, passes through the input stage processing unit 2, and is passed to each of the processing units 3, 4, 5, and 6.

An input device 9, a storage device 10, and an output device 11 are connected to the image processing device 1 via an input / output processing unit 8, and are used for specifying a position to be inspected, focusing, and measuring dimensions. In addition, an image storage unit 3, an image detection unit 4, a contrast detection unit 5, a dimension measurement unit 6, and an object / sample distance control unit 7 are provided. In the image processing apparatus 1, the operation of each processing unit is controlled by a control unit (not shown), and a series of processes such as focusing and dimension measurement are performed.

FIG. 2 is a diagram for explaining measurement site detection and focusing in the pattern inspection apparatus of the present embodiment.
FIG. 2A shows an example of an image for setting a certain measurement site captured by the imaging unit 12, and FIG. 2B shows an example of an image at the time of actual pattern inspection.

First, when setting a measurement site, a reference point 17b for specifying coordinates in the feature model 17a is provided on a screen 19a in FIG. 9A, and distances x and y on the screen with respect to the reference point 17b are specified. Measurement model 18
The measurement site 18b on a is specified.

At the time of pattern inspection, a characteristic model 17c in an image pickup screen 19b shown in FIG.
The measurement model 1 is obtained from the positional relationship with the feature model 17c.
8c is specified, focused, and the measurement site 18
The dimension measurement of d is performed. Focusing is performed on the measurement model 18c, whereby reliable and highly accurate focusing of the position to be measured is realized.

In order to realize such processing, each processing section of the image processing apparatus 1 is provided with the following functions. The image storage unit 3 stores the image information from the imaging unit 12 and, as the position detection information of the measurement site, for example, as shown in FIG.
(A) Shape of feature model 17a and its reference point 17b
And the shape of the measurement model 18a and the measurement site 18b
And the position information (x, y) of the measurement site 18b from the reference point 17b of the feature model 17a. Also,
The image storage unit 3 can store position detection information of a measurement site similar to that in FIG. 2A for a plurality of types of specimens.

The image detecting section 4 detects a feature model in the image by image processing based on the image and the shape of the feature model input through the input stage processing section 2. Specifically, the captured image is binarized, further divided into a plurality of blocks, and each block is compared with the feature model shape stored in the image storage unit 3 to detect a feature model. Further, by detecting the feature model 17c, the positions of the measurement model 18c and the measurement site 18d are further specified from the position detection information, and are notified to the contrast detection unit 5 and the dimension measurement unit 6.

The objective / sample distance control section 7 controls the operation of the objective / sample distance movable section 15 of the microscope apparatus. When the feature model is detected, the position of the objective lens 14 is adjusted by controlling the objective-sample distance movable section 15 of the microscope apparatus according to a predetermined algorithm.

The contrast detection unit 5 includes a distance table, detects and stores contrast information at each operation position when the objective-sample distance movable unit 15 performs a focusing operation, and at the same time, an objective lens position at which the contrast becomes maximum, that is, an objective lens position. Determine the focus position.

The dimension measuring section 6 finally has the objective lens 14
When is adjusted to the in-focus position, the dimension of the measurement site is measured, and the dimension value is stored. The input / output processing unit 8 includes an image processing device 1, an input device 9, a storage device 10, and an output device 11.
In the meantime, input / output operations such as setting and saving of position detection information of a measurement site, saving of measured dimensions, or image output at the time of setting of position detection information and measuring dimensions are performed.

The storage device 10 stores position detection information of measurement sites for various specimens, dimension measurement results of each measurement site subjected to pattern inspection, and the like. The output device 11 is a CRT
And a display device such as a liquid crystal display.

Next, the operation of the pattern inspection apparatus according to the embodiment of the present invention configured as described above will be described. This pattern inspection apparatus is used, for example, in an inspection process in a semiconductor manufacturing process. Products or semi-finished products on the wafer to be inspected are automatically set in the sample setting section sequentially, and a measurement site such as a device line width is automatically measured by a flow described later.

In measuring the measurement site, the position detection information of the measurement site of the device to be inspected is stored in the image storage unit 3.
Is set to In this setting operation, first, an image of a sample for data setting is displayed on the output device 11 in a state as shown in FIG.

The data setter specifies a feature model 17a for specifying a position in the wafer by using a pointing device such as a mouse or a trackball. Specifically, first, a reference point 17b is set, and then a diagonal point 17e is specified with a trackball.
And a rectangular area having the point 17e as a diagonal point is set, and thereby the feature model 17a is specified. Here, the shape selected as the feature model is a shape such as a characteristic wiring pattern that can be easily recognized by an image.

Next, the measurement site 18 on the measurement model 18a
When the center point of b is input with a trackball, the reference point 17
The x-direction distance and the y-direction distance between a and the measurement site 18b are calculated, and the position information (x, y) is determined.

The position detection information of the measurement site obtained in this manner is set in the image storage unit 3 and also stored in the storage device 10 as a secondary storage device, and is used for the next setting and the like. You. That is, the setting of the position detection information of the measurement site may be performed before and the information stored in the storage device 10 may be used.

After such preparations have been made, the apparatus is subjected to pattern inspection in an inspection step. The operation flow at this time is shown in FIG. FIG. 3 is a flowchart showing the operation of the pattern inspection apparatus according to the present embodiment.

In this processing operation, each processing unit of the image processing apparatus 1 is controlled by control means (not shown), and a series of processing is executed. First, sample 1
6 is set and the pattern inspection is started.
The position of the objective lens 14 is moved to the upper limit by the inter-sample distance movable section 15 (ST1).

Next, the operation of the objective / sample distance movable section 15 based on a command from the objective / sample distance control section 7 causes
The position of the objective lens 14 approaches the sample 16 side by one step (ST2), and in synchronization with this, the image is taken by the image processing apparatus 1 one by one (ST3).

Based on the captured image and the position detection information of the measurement site stored in the image storage unit 3, a characteristic model 17 c shown in FIG. 2B is detected by image processing by the image detection unit 5. A reference point 17d is obtained. Further, by using the reference point 17d, the measurement model 1
8c is detected, and the position information of the measurement site 18d is sent to the contrast detection unit 5 (ST4). Sample 16
Measurement model 1 every time the distance between objective lenses 14 is changed
8c is performed even if the objective lens 14 is tilted from the sample orthogonal axis or the sample 16 is tilted, or even if the objective lens movement axis is not parallel to the optical axis.
This is to enable contrast detection at 8d. Therefore, for example, if the moving axis of the objective lens 14 is exactly along the orthogonal axis to the sample 16 and the optical axis is parallel to the moving axis of the objective lens, the detection of the measurement site 18d in step ST4 involves the objective lens 14 being detected. It only needs to be performed once immediately after moving to the upper limit.

Next, based on the received position information of the measurement site 18d, the contrast detection unit 5 executes contrast detection at the position (ST5), and the measurement site 1 is detected.
The 8d contrast information is stored in a table corresponding to the distance between the object and the sample (ST6).

It is determined whether or not the position of the objective lens 14 has reached the final position (ST7). If not, the process returns to step ST2. On the other hand, when the movement of the movable section 15 between the objective and the sample within the entire movement range is completed (ST7),
The distance table is referred to by the contrast detector 5 (ST8), and the distance between the object and the sample at which the contrast becomes maximum is obtained (ST9).

The objective / sample distance control unit 7 moves the objective lens 14 so as to move the objective lens 14 to the determined position.
A command is output to the inter-sample distance movable unit 15 and the objective lens 1
4 is moved to the corresponding position, so that the measurement site 18d
Is focused (ST10).

After focusing, the dimensions of the measurement site 18 of the device to be inspected are measured by the dimension measuring unit 6, and the results are stored in the storage device 10 (ST1).
1). As described above, the pattern inspection apparatus according to the embodiment of the present invention uses the feature model 17c set in the image storage unit 3 in the image captured by the imaging unit 12.
Is detected based on the positional relationship between the two, and the distance between the objective and the sample at which the contrast value becomes maximum at the measurement site 18d is determined as the focusing position.
Since the position of No. 4 is determined, focusing at the measurement site 18d is reliably and accurately performed, and
It is possible to reduce the size measurement error in the minute pattern.

Further, the pattern inspection apparatus of the present embodiment
In evaluating the image contrast at the measurement site, each time the distance is changed by the objective-sample distance movable unit 15, the specific site 1
Since the position identification of 8d is performed, even if, for example, the moving axis of the movable section 15 between the objective and the sample has an inclination from the optical axis and the captured image is slightly deviated every time the distance is changed, it is ensured. The image contrast can be evaluated at the inspection target position. (Second Embodiment of the Invention) In the first embodiment, the movable section 15 between the object and the sample is moved from the upper limit position to the lower limit position, and the contrast information of the measurement site 18d, that is, light and dark, is provided every moving step. The difference information is stored in the movement table, and the position having the maximum contrast in all the movement steps is detected. On the other hand, in the present embodiment, the contrast information is compared for each movement step, and a position where the contrast value becomes a peak is searched for.
The in-focus position is detected without moving the movable section 15 between the object and the sample over the entire range.

The pattern inspection apparatus according to the present embodiment
Each unit shown in FIG. 1 is configured in the same manner as in the first embodiment, and a description of each unit in FIG. 1 will be omitted. In the present embodiment, FIG.
The operation procedure of a control unit (not shown) for controlling each unit is different from that of the first embodiment, and the contents will be described below with reference to FIG.

FIG. 4 is a flowchart showing the operation of the pattern inspection apparatus according to the embodiment of the present invention. First, setting of position detection information of a measurement site and 16 sets of samples in the sample setting section are processed in the same manner as in the first embodiment.

In FIG. 4, steps ST21 to ST25 are processed in the same manner as steps ST1 to ST5 in FIG. 3 in the first embodiment.

As the contrast information obtained in step ST25, the past one step and the one created this time are stored. Next, the current and previous contrast information are compared. If the current contrast value is larger, (S
T26), and return to step ST22. Thereby, in step ST22, the position of the objective lens is further moved by one step. Note that the process returns to step ST22 unconditionally for the first time, that is, in the case of the upper limit of the object position.

On the other hand, if the previous contrast value is larger (ST26), a contrast peak is obtained at the previous objective lens position. Therefore, the distance between the objective and the sample is returned by one step. That is, focusing is performed by increasing the distance by one step (ST27).

After focusing, the dimensions of the measurement site 18 of the device to be subjected to pattern inspection are measured by the dimension measuring unit 6, and the results are stored in the storage device 10 (ST2).
8). As described above, the pattern inspection apparatus according to the embodiment of the present invention is provided with the same configuration as that of the first embodiment, and also detects the distance between the objective lens 14 and the sample 16 when detecting the focus position. Since the change is started from the maximum distance and the distance is sequentially shortened, and the position immediately before the position where the image contrast is reduced is set as the focus position, the same effect as in the first embodiment can be obtained. In addition to playing, the in-focus position can be detected with the minimum number of movements.

In this embodiment, the objective lens 14,
The distance change between the specimens 16 was started from the maximum distance. Conversely, starting from the shortest distance and gradually increasing the distance, the position immediately before the position where the image contrast was reduced was set as the in-focus position. You may. (Third Embodiment of the Invention) In the first and second embodiments, one measurement model 18a and one measurement site 18b are designated, and focusing is performed at the measurement site.

On the other hand, in the present embodiment, it is possible to designate a plurality of measurement models 18a and measurement sites 18b, and to precisely measure the dimensions by focusing each of them at one inspection. Things.

The configuration of each part of the pattern inspection apparatus of this embodiment is the same as that of the first and second embodiments shown in FIG. The setting of the measurement site 18b is performed in the same manner as in the case described in the first embodiment. However, since there are a plurality of setting locations, the input of the center point of the measurement site 18b is performed a plurality of times.

The operation of the pattern inspection apparatus of this embodiment is as follows.
In the case of the device corresponding to the first embodiment, first, FIG.
The processing of steps ST1 to ST11 is performed by
Is repeated a plurality of times in accordance with the set number.

Similarly, in the case of the apparatus corresponding to the second embodiment, the processing of steps ST21 to ST28 in FIG. 4 is repeated a plurality of times according to the set number. As described above, the pattern inspection apparatus according to the embodiment of the present invention is configured in the same manner as the first or second embodiment, is provided with a plurality of measurement sites, and is provided for each inspection of each measurement site. Since the focus is adjusted to the detected focus position, the first or second focus is set.
In addition to the effect similar to that of the embodiment, the dimensions can be measured reliably and with high accuracy at a plurality of locations in the same image with one specimen set.

The present invention is not limited to the above embodiments, but can be variously modified without departing from the scope of the invention. For example, in each of the above embodiments, the case of a semiconductor inspection device formed on a wafer has been described. However, the present invention is not limited to this, and is formed on a substrate for a liquid crystal panel or a PDP (plasma display panel). It can also be used when inspecting a pattern or the like.

Further, in each embodiment, the contrast at a specific position is measured for each step between the objective lens and the sample, and
Although the focusing is performed at the position of the maximum contrast, the present invention is not limited to this. For example, the present invention can be applied to a method of focusing on a specific spot in an image using a laser. Specifically, the sample setting unit may be moved so that the measurement site to be focused is at the spot position of the focusing laser, and the laser may be irradiated at this position to perform focusing.

The method described in the embodiment may be a computer-executable program such as a magnetic disk (floppy disk, hard disk, etc.), an optical disk (CD-ROM, DVD, etc.), or a storage medium such as a semiconductor memory. And can also be transmitted and distributed via a communication medium. A computer that implements the present apparatus reads a program recorded on a storage medium, and executes the above-described processing by controlling the operation of the program.

Although the present invention has been described based on the embodiments, the present invention includes the following inventions. (1) A plurality of inspection target positions are provided, and each inspection of each inspection target position focuses on a corresponding in-focus position detected by the in-focus position detecting means. The pattern inspection apparatus according to any one of the above. (2) The pattern inspection apparatus according to any one of (1) to (3) or (1), wherein the inspection at the inspection target position is a dimension measurement. (3) In a pattern inspection apparatus for inspecting a position to be inspected by focusing on the sample, an imaging unit for imaging the sample, an imaging unit for projecting the sample image to the imaging unit,
Position adjusting means for adjusting the distance between the image forming means and the sample, and a position specifying shape serving as a reference for specifying a position in the sample in an image taken by the imaging means, and the position specifying shape and the inspection target position Position specifying information storage means for storing relative position information with respect to the image, image processing means for detecting the position specifying shape in the image captured by the imaging means, and the position specification detected by the image processing means Inspection target specifying means for specifying the inspection target position based on the shape position and the relative position information,
The distance between the imaging unit and the specimen is changed by the position adjusting unit, and the image contrast at the inspection target position at each distance is evaluated. The position where the image contrast is maximized is set as the focusing position. A pattern inspection apparatus comprising: a position detection unit.

The functions and effects (1) to (3) will be described. First, the pattern inspection apparatus of the invention corresponding to the above (1) operates in the same manner as the invention according to any one of the first to third aspects, and has a plurality of inspection target positions,
Focusing is performed on the corresponding in-focus position detected by the in-focus position detecting means for each inspection of each inspection target position. This makes it possible to reliably and accurately measure the dimensions of a plurality of locations in the same image with one specimen set.

Next, the pattern inspection apparatus of the invention corresponding to the above (2) operates in the same manner as the invention corresponding to any one of the first to third aspects or the above (1), and also inspects the inspection target position. Means dimensional measurement. Therefore, it is possible to provide a minute dimension measuring device capable of surely and highly accurately measuring a dimension.

Further, in the pattern inspection apparatus according to the invention corresponding to the above (3), in addition to the same operation as the invention according to the first aspect, the position identification information storage means allows the image captured by the image pickup means to include: A position specifying shape serving as a reference for specifying a position in the specimen and relative position information between the position specifying shape and the inspection target position are stored in the position specifying information storage unit in advance. Then, the image processing unit and the inspection target specifying unit execute the processing of each unit using the stored information. Therefore, the effect of the invention corresponding to claim 1 can be reliably achieved.

[0062]

As described above in detail, according to the present invention, since the optical position having the maximum contrast at the inspection target position in a predetermined positional relationship from the position specifying shape in which the image can be easily recognized is determined as the in-focus position. It is possible to provide a pattern inspection apparatus in which the focusing at the target position is reliably ensured and the inspection error such as a dimension measurement error in a minute pattern is small.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a pattern inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a view for explaining measurement site detection and focusing in the pattern inspection apparatus of the embodiment.

FIG. 3 is a flowchart showing an operation of the pattern inspection apparatus in the embodiment.

FIG. 4 is a flowchart showing an operation of the pattern inspection apparatus according to the embodiment of the present invention.

[Description of Signs] 1 ... Image processing device 3 ... Image storage unit 4 ... Image detection unit 5 ... Contrast detection unit 6 ... Dimension measurement unit 7 ... Object / sample distance control unit 9 ... Input device 10 ... Storage device 11 ... Output Apparatus 12 ... Imaging unit 13 ... Imaging means 14 ... Objective lens 15 ... Movable part between objective and sample 16 ... Sample

Claims (3)

[Claims] 1. A pattern inspection apparatus for inspecting a position to be inspected by focusing on a sample, an imaging unit for imaging the sample, an imaging unit for projecting a sample image to the imaging unit, and the imaging unit Position adjusting means for adjusting the distance between the sample and the sample; image processing means for detecting a position specifying shape in the captured image by the imaging means; and a position specifying shape detected by the image processing means. Based on a position, an inspection target specifying unit that specifies the inspection target position, and a distance between the imaging unit and the sample is changed by the position adjustment unit, and an image contrast at the inspection target position at each distance is evaluated. A focus position detecting means for setting a position where the image contrast becomes maximum as a focus position. 2. The method according to claim 1, wherein said image adjusting means is used by said position adjusting means when evaluating image contrast at said inspection target position.
2. The pattern inspection apparatus according to claim 1, wherein the inspection target position is specified by the inspection target specifying unit every time the distance between the samples is changed. 3. When detecting the in-focus position by the in-focus position detecting means, the position adjusting means starts changing the distance between the imaging means and the sample from a shortest distance or a maximum distance and sequentially increases the distance. 3. The pattern inspection apparatus according to claim 1, wherein a position immediately before the position where the image contrast is reduced is set as a focus position. 4.