JP2003172710A - Method and device for inspecting pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an accuracy in inspecting a pattern for a minute pattern by recognizing the pattern precisely without being affected by the density of a pattern arrangement or the like. <P>SOLUTION: An image of a pattern P formed on a photomask is picked up. In advance of inspecting the pattern P based on the image obtained by the image pickup, a correction mask having the pattern on which pattern constitution graphics in plural sizes are arranged by plural kinds of pitches is prepared, the image of an image pickup result for the pattern on the correction mask and a design value of the same are compared each other, and a correction value table concerning the image is made based on a comparison result. Then, the image pick up result of the pattern P to be inspected is corrected using the correction value table, and the pattern P is inspected based on the corrected image pickup result. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection method and a pattern inspection method for inspecting, for example, a defect of a pattern formed on a photomask used in a lithography process in a semiconductor device manufacturing process. Regarding the device.

[0002]

2. Description of the Related Art Generally, in a semiconductor device manufacturing process, short wavelength ultraviolet light or the like is irradiated onto a wafer substrate through a photomask having a light transmitting region and a light shielding region, thereby A lithographic process such as forming a desired circuit pattern on a wafer substrate is widely used. A circuit pattern or the like formed in this lithography process is specified by a pattern composed of a light transmitting region and a light shielding region on the photomask. Therefore, in order to obtain a desired circuit pattern or the like, it is necessary to inspect the pattern for defects on the photomask in advance.

The pattern inspection of the photomask is performed by, for example,
The pattern to be inspected is CCD (Charge Coupled Dev
ice) An image is picked up by an image pickup means such as a camera, and an image obtained by this is used. That is, an image of a pattern that is an imaging result and a CAD for the pattern
(Computer Aided Design) data and the like are compared to detect differences and defects between them.
In addition, for example, using a scanning electron microscope (SEM),
It may be performed by scanning the pattern to be inspected with an electron beam.

The inspection result thus obtained is fed back to the design data of the pattern. For example, even if the pattern is a corner on the design data, the corner is often rounded when formed because the pattern is minute. In such a case, the result of the inspection becomes clear, so the design data is corrected so that the corners are not rounded. That is, the pattern defect inspection corrects the design data so that an image having the same shape as that of the characteristic portion of the characteristic pattern arbitrarily selected on the design data can be obtained. This correction is uniformly applied to the entire surface of the inspected area on the photomask.

[0005]

By the way, in recent years, as semiconductor devices have been further miniaturized, the size of the pattern formed on the photomask has become smaller and smaller. Such a reduction in the pattern causes difficulty in accurately obtaining an image or the like of the pattern when performing the above-described pattern inspection.

More specifically, as the pattern shrinks and its size approaches the wavelength of illumination light for image acquisition,
Due to the effect of optical resolution, the contrast of the image obtained by the image pickup means will be reduced. Therefore, a difference may occur between the actual pattern shape and the acquired image depending on the size of the pattern constituent figure, the arrangement pitch thereof, and the like. Specifically, even if the pattern constituent figures have the same line width, the acquired image may differ depending on the density of the arrangement. For example, the line width of the image may be different in the dense part compared to the sparse part. It can happen that it gets bigger.

Such a difference in the acquired images has a bad influence on the result of the pattern inspection. That is, if the image of the pattern cannot be accurately acquired, it is possible that the pattern is erroneously detected as a defect as a result of the pattern inspection even though the pattern is formed according to the design data.

Therefore, according to the present invention, even a pattern corresponding to further miniaturization can be accurately recognized without being affected by the density of the arrangement and the like. An object of the present invention is to provide a pattern inspection method and a pattern inspection apparatus that can improve accuracy.

[0009]

The present invention is a pattern inspection method devised to achieve the above object. That is, the pattern formed on the photomask is imaged,
A pattern inspection method for inspecting the pattern based on an image obtained by the image pickup, comprising preparing a correction mask having a pattern in which pattern constituent figures of a plurality of sizes are arranged at a plurality of types of pitches, respectively, and An image of the pattern formed on the mask for inspection is imaged, the value obtained from the image as the imaged result is compared with the design value of the pattern on the correction mask, and the difference between the two specified by the comparison is used. Then, a correction value table for the image is created, and after that, the pattern to be inspected is imaged, and the image of the imaging result is corrected using the correction value table to inspect the pattern. Characterize.

The pattern inspection method of the present invention is a pattern inspection method of scanning a pattern formed on a photomask with an electron beam and inspecting the pattern based on the scanning result. A correction mask having patterns in which pattern constituent figures are respectively arranged at a plurality of types of pitches is prepared, the pattern formed on the correction mask is scanned, and the value obtained from the scanning result and the correction mask The design value of the pattern is compared, and a correction value table for the scanning result is created based on the difference between the two specified by the comparison, and then the pattern to be inspected is scanned and the scanning is performed. The result is corrected using the correction value table, and the pattern is inspected.

Further, the present invention is a pattern inspection apparatus devised to achieve the above object. That is, a pattern inspection device for capturing an image of a pattern formed on a photomask and inspecting the pattern based on the image obtained by the image capturing, in order to correct the image obtained by the image capturing. In addition to the correction value table, the correction value table captures an image of a correction mask having a pattern in which pattern constituent figures of a plurality of sizes are arranged at a plurality of types of pitches, respectively, prior to the imaging of the pattern to be inspected. It is characterized in that it is created based on the result of comparison by comparing the value obtained from the image which is the image pickup result with the design value of the pattern on the correction mask.

The pattern inspection apparatus of the present invention is a pattern inspection apparatus for scanning a pattern formed on a photomask with an electron beam and inspecting the pattern based on the scanning result. In addition to providing a correction value table for correcting the result, the correction value table includes a pattern in which pattern constituent figures of a plurality of sizes are arranged at a plurality of types of pitches prior to scanning of the pattern to be inspected. The correction mask included therein is scanned, the value obtained from the scanning result is compared with the design value of the pattern on the correction mask, and the correction mask is created based on the comparison result.

According to the pattern inspection method and the pattern inspection apparatus having the above-described procedure, the correction value table is created based on the imaging result or the scanning result of the correction mask. A pattern whose constituent figures are arranged at a plurality of types of pitches is used. That is, the correction value table takes into consideration the influence of the density of the pattern constituent figures on the imaging result or the scanning result. Therefore, by correcting the imaging result or scanning result obtained from the photomask to be inspected using the correction value table, the adverse effect due to the density of the arrangement of the pattern formed on the photomask is eliminated. While doing so, it becomes possible to perform an appropriate inspection.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pattern inspection method and a pattern inspection apparatus according to the present invention will be described below with reference to the drawings.

First, a schematic structure of the pattern inspection apparatus will be briefly described. FIG. 1 is a schematic configuration diagram showing an example of a pattern inspection apparatus according to the present invention. The pattern inspection apparatus described here is for inspecting the pattern P formed on the photomask, and as shown in the figure, the camera 1, the illumination lamp 2, the optical system 3,
The control unit 4 and the image output unit 5 are provided.

The camera 1 is for taking an image of the pattern P to be inspected, and is configured to take the image by using an image sensor such as a CCD. By the photoelectric conversion in the camera 1, the imaged pattern P is converted into image data.

The illumination lamp 2 emits illumination light necessary for the camera 1 to take an image. This lighting lamp 2
Then, in order to increase the resolution of imaging and improve the inspection accuracy, light having a short wavelength such as blue light or violet light is emitted.

The optical system 3 guides the irradiation light from the illumination lamp 2 to the pattern P on the photomask to be inspected and guides the transmitted light from the pattern P to the camera 1. It may be possible to use various lenses such as a condenser lens and an objective lens.
However, the optical system 3 may include a beam splitter, a mirror, and the like, and may be configured to guide the reflected light from the pattern P to the camera 1.

The control unit 4 includes a CPU (Central Processing).
Unit), RAM (Random Access Memory), ROM (R
(Ead Only Memory), other circuits, etc. are combined to control the operation of the entire pattern inspection apparatus and also to process the image data received from the camera 1. Then, for the processing, the control unit 4 has functions as the data correction unit 4a and the correction value table 4b.

The data correction unit 4a performs a correction process on the image data received from the camera 1. The correction value table 4b is a table of correction values necessary for the correction processing. The details of the correction process and the correction value table 4b will be described later.

In addition to the data correction unit 4a and the correction value table 4b, the control unit 4 has an A / D conversion circuit 4c for performing A / D conversion processing on image data from the camera 1, and
A comparison circuit 4d or the like for comparing the image data received from the camera 1 with design data (CAD data, etc.) for the pattern P to be inspected, which is the basis of the image data, and for specifying the difference or defect between them. It may have a function as. The camera 1 may have functions as the data correction unit 4a, the correction value table 4b, the A / D conversion circuit 4c, the comparison circuit 4d, and the like included in the control unit 4, for example.

The image output unit 5 is a CRT (Cathode Ray Tu
be) or a display device such as a liquid crystal panel, which receives the image data corrected by the data correction section 4a and outputs it as an image. If the control unit 4 has a function of identifying a defect or the like in the pattern P, information regarding the identified defect or the like is also displayed as an image.

Next, a pattern inspection method performed by using the pattern inspection apparatus having the above configuration will be described.
The pattern inspection using the pattern inspection apparatus is performed by imaging the pattern P to be inspected with the camera 1.

FIG. 2 is an explanatory view showing a specific example of a pattern to be inspected and its image pickup result. Here, as the pattern P to be inspected, as shown in FIG. 2A, pattern constituent figures P1 and P2 having mutually different sizes.
However, consider the ones arranged at different pitches.

In this case, the signal intensity of the image data obtained by the camera 1 by imaging the pattern P is as shown in FIG.
As shown in (b). That is, the cross section of the signal intensity tends to decrease as the line widths of the pattern constituting figures P1 and P2 become thinner. Further, in a repetitive pattern lined up at a narrow pitch, interference occurs between adjacent constituent figures, which lowers the contrast, and conversely tends to increase the cross-sectional width of the signal intensity.

By the way, when the image data obtained by the camera 1 is imaged, the threshold value TH set in advance is used to binarize the image data. Therefore, if the signal intensity of the image data has the above-mentioned tendency, the image obtained by binarization reflects the tendency as it is, as shown in FIG. It may be inaccurate due to the influence of P2 density.

Therefore, in this embodiment, the data correction unit 4a corrects the image data obtained by the camera 1 by using the correction value table 4b to ensure the accuracy of the image.

The correction value table 4b necessary for correcting the image data needs to be created prior to the pattern inspection, but in this embodiment, the creation is performed by the procedure described below.

In creating the correction value table 4b,
First, a correction mask having patterns in which pattern-forming figures of a plurality of sizes are arranged at a plurality of types of pitches is prepared. FIG. 3 is an explanatory diagram showing a specific example of the pattern of the correction mask. The pattern shown in the figure is a pattern constituent figure P3 having a line width of 0.5 μm and a line width of 1.
0 μm size pattern constituent figure P4, line width 2.0 μ
Each of the m-sized pattern constituent figures P5 is 0.1
Predetermined pitch such as μm interval (see A in the figure), 1.5 times the pitch (see B in the figure), 2 times the pitch (see C in the figure), 3 times the pitch (see D in the figure) It was arranged in.

After preparing such a correction mask,
The camera 1 takes an image of the pattern formed on the correction mask. Then, each pattern constituent figure P3, P4, P
Regarding the line width and pitch of No. 5, the values obtained from the image as the image pickup result are compared with the design values of the pattern on the correction mask, and the coincidence points and the difference points between them are specified. As a result, the amount of deviation on the image with respect to the design value of the pattern becomes clear, and the correction value table 4b may be created based on the amount of deviation.

FIG. 4 is an explanatory diagram showing a specific example of the correction value table. In the correction value table 4b in the illustrated example, the deviation amount when the line width is 3 μm and the pattern pitch is 1: 3 is set to “0” (the value obtained from the image and the design value are the same), and other line widths and the like are set. Sets the correction coefficient appropriately. In the correction value table 4b, between correction values, the values may be interpolated and complemented by using, for example, a linear coefficient.

After the correction value table 4b is created in this way, the correction value table 4b is stored in a predetermined memory area in the control unit 4. As a result, when the control unit 4 is provided with the correction value table 4b, the data correction unit 4a then applies the correction value table 4b to the image data obtained by the camera 1 from the pattern P to be inspected. Perform correction using. That is, the correction value table 4
The line width of the pattern P on the image is corrected based on b. Since the correction itself at this time and the image processing and the like associated therewith may be performed by using well-known arithmetic processing and the like, description thereof will be omitted here.

As described above, according to the pattern inspecting method and the pattern inspecting apparatus used in this embodiment, the image of the pattern P to be inspected is corrected using the correction value table 4b, Since the pattern P is inspected based on the corrected image, the image of the pattern can be acquired accurately. Therefore, even with respect to the pattern P corresponding to further miniaturization, the pattern P can be accurately recognized, erroneous detection of defects and the like can be suppressed as much as possible, and as a result, the accuracy of pattern inspection can be improved.

Moreover, according to the pattern inspection method and the pattern inspection apparatus of this embodiment, the correction value table 4b required for improving the accuracy of the pattern inspection is arranged with the pattern constituent figures of a plurality of sizes at a plurality of types of pitches. It is created by using a correction mask having a different pattern.
In other words, as the correction mask that is the basis of the correction value table 4b, one that regularly expresses the density of the pattern constituent figures P3, P4, and P5 is used. Therefore, the correction value table 4b created based on this is one in which the amount of image shift caused by the density of the pattern is properly reflected, and is therefore used to correct the amount of shift. It can be said that it is suitable. Furthermore, the pattern constituent figure P3
Since the correction mask in which the density of P4 and P5 is regularly expressed is used as a base, the interpolation of the correction value becomes easy.
It is possible to deal with any pattern P to be inspected, and as a result, the versatility of the pattern inspection can be improved. Even when the pattern P to be inspected is miniaturized and its size becomes substantially the same as the wavelength of the illumination light from the illumination lamp 2, the line width of the pattern constituent figure on the correction mask is particularly large. By appropriately setting, it is possible to deal with the amount of image shift due to the influence on the optical resolution. That is, it can be said that it is suitable for improving the inspection accuracy of a fine pattern.

It is needless to say that the specific mode described in the present embodiment is only one specific example of the present invention, and the present invention is not limited to the specific example. In particular, the line widths of the pattern constituting figures P3, P4 and P5 on the correction mask and the arrangement pitches thereof may be of course different from those described in the present embodiment.

Further, in the present embodiment, the case where the pattern inspection is based on the imaging result of the pattern to be inspected has been described as an example, but the present invention is not limited to this, and for example, SEM. It is conceivable to apply exactly the same even in the case of performing a pattern inspection using. That is, even when the pattern to be inspected is scanned with an electron beam and the pattern is inspected based on the scanning result, correction is performed based on the scanning result of the correction mask before scanning the pattern. Create a value table,
If the scanning result for the pattern to be inspected is corrected using the correction value table, the accuracy of the pattern inspection can be improved.

[0037]

As described above, the pattern inspection method and the pattern inspection apparatus according to the present invention have an influence on the density of the pattern arrangement and the like even if the pattern formed on the photomask is further miniaturized. Since the pattern can be correctly recognized without receiving the pattern, the accuracy of the pattern inspection can be improved. Therefore, by using the present invention, it is expected that further miniaturization, higher precision, higher processing efficiency, etc. can be realized in the lithography process using a photomask.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a specific example of a pattern to be inspected and its imaging result.

FIG. 3 is an explanatory diagram showing a specific example of a pattern included in a correction mask.

FIG. 4 is an explanatory diagram showing a specific example of a correction value table.

[Description of Reference Signs] 1 ... Camera, 4 ... Control unit, 4a ... Data correction unit, 4b ...
Correction value table, 5 ... Image output unit, P ... Pattern, P
1, P2, P3, P4, P5 ... Pattern constituent figure

Claims (4)

[Claims] 1. A pattern inspecting method for imaging a pattern formed on a photomask and inspecting the pattern based on an image obtained by the imaging, wherein pattern constituent figures of a plurality of sizes are respectively of a plurality of types. A correction mask having a pattern arranged at a pitch is prepared, a pattern formed on the correction mask is imaged, and a value obtained from an image as a result of the imaging and a design value of the pattern on the correction mask And a correction value table for the image is created based on the differences between the two specified by the comparison, and then a pattern to be inspected is imaged, and the image of the imaging result is corrected by the correction. A pattern inspecting method, which comprises inspecting the pattern by performing correction using a value table. 2. A pattern inspecting method of scanning a pattern formed on a photomask with an electron beam and inspecting the pattern based on the scanning result, wherein pattern forming figures of a plurality of sizes each have a plurality of types. Prepare a correction mask having a pattern arranged at a pitch, scan the pattern formed on the correction mask, and compare the value obtained from the scanning result with the design value of the pattern on the correction mask. Then, a correction value table for the scanning result is created based on the differences between the two specified by the comparison, and then the pattern to be inspected is scanned and the scanning result is used in the correction value table. The pattern inspection method is characterized in that the pattern is inspected and corrected. 3. A pattern inspection apparatus for capturing an image of a pattern formed on a photomask and inspecting the pattern based on the image obtained by the image capturing, the correction being performed on the image obtained by the image capturing. And a correction mask having a pattern in which pattern-forming figures of a plurality of sizes are arranged at a plurality of types of pitches, respectively, prior to the imaging of the pattern to be inspected. Is imaged, and the value obtained from the image that is the imaged result is compared with the design value of the pattern on the correction mask,
A pattern inspection apparatus, which is created based on the comparison result. 4. A pattern inspection apparatus for scanning a pattern formed on a photomask with an electron beam and inspecting the pattern based on the scanning result, which is for correcting the scanning result. With a correction value table, the correction value table, prior to the scanning of the pattern to be inspected, scan the correction mask having a pattern in which the pattern constituent figures of a plurality of sizes are respectively arranged at a plurality of types of pitch, A pattern inspection apparatus characterized by being created based on a result of comparison by comparing a value obtained from the scanning result with a design value of a pattern on the correction mask.