JP2001101414A - Mask pattern shape measurement / evaluation apparatus, shape measurement / evaluation method, and recording medium recording shape measurement / evaluation program - Google Patents

Abstract

An object of the present invention is to provide an accurate and high-precision shape measurement and evaluation device, a shape measurement and evaluation method, and a shape measurement and evaluation program by enabling quantitative measurement of a pattern shape of a photomask including a fine pattern. And a recording medium on which is recorded. In a mask pattern shape measurement and evaluation device, mask pattern image data is input, computer processing is performed to extract pattern shape data, and then a predetermined shape characteristic value is measured and processed. It is characterized by being evaluated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask pattern shape measuring / evaluating apparatus for extracting a pattern shape of a photomask used in a lithography process of semiconductor manufacturing from a pattern image and measuring and evaluating a predetermined pattern shape characteristic value. The present invention relates to a measurement evaluation method and a recording medium on which a shape measurement evaluation program is recorded.

[0002]

2. Description of the Related Art With the recent miniaturization of semiconductor LSI patterns, photomasks as pattern masters are also required to respond to miniaturization, and at the same time, demands for high precision are extremely severe. Conventionally, three items of defects, dimensional accuracy, and alignment have been particularly emphasized as important items in photomask quality. At present, as semiconductor miniaturization advances, a high-precision dedicated photomask inspection apparatus for measuring each item. Has been developed and used. However, the demand for higher precision by making photomask patterns finer is the above 3
The same is true for all quality items other than the items (pattern shape, pattern data guarantee, durability, cleanliness, etc.). The accuracy of the pattern shape is particularly important because it directly affects the accuracy and performance of the LSI circuit. It has come to be.

As for the pattern shape of a photomask, it is naturally desirable that a pattern exactly as shown in the design drawing of the mask pattern designed in the mask layout design of the semiconductor circuit is accurately reproduced on the mask. However, in practice, a fine pattern is processed on a metal thin film on glass using lithography technology.Therefore, the mask pattern and the design pattern are not completely the same shape, and there are minute differences such as dimensional differences and round corners. There are significant differences. In most cases, this difference is about several tens to several hundreds of nanometers on the mask. However, with the recent progress in miniaturization of the VLSI, there is a concern that this may affect the characteristics of the semiconductor circuit. Has begun. In other words, the finer the pattern, the greater the difference in the pattern shape with respect to the pattern itself, which affects the characteristic value.

With the rapid miniaturization in recent years, attempts to solve the above-mentioned problem of the pattern shape by actively utilizing the optical principle in the projection exposure technique have been actively made. A typical example is an optical proximity effect correction mask (hereinafter, referred to as an OPC mask). Here, the OPC mask will be described. The OPC mask is designed to transfer the circuit pattern shape with high accuracy during wafer exposure transfer.
This is a mask to which a fine optical proximity effect correction pattern (hereinafter referred to as an OPC pattern) is added so as to be close to or in contact with the original circuit pattern. The OPC pattern can correct the shape of the transfer pattern caused by the optical proximity effect at the time of projection exposure transfer by using the optical interference effect between adjacent patterns, and the original design pattern can be transferred accurately. And is often disposed at the four corners of the original circuit pattern or at the part closest to the adjacent pattern. Recently, a type of OPC pattern that makes the entire circuit pattern complicatedly deformed has also been proposed. However, since it is unnecessary as an original circuit pattern, the OPC pattern itself must be fine enough not to be transferred. Therefore,
Since the OPC pattern is considerably finer than the conventional pattern, the dimensional rule of the mask pattern will be drastically finer than the conventional mask, and a very advanced fine processing technology is required in terms of the mask manufacturing technology. And Of course, in terms of miniaturization, it is certain that conventional photomasks will also evolve in the same way, and advanced microfabrication technology is also required. Therefore, the above-mentioned problem of the pattern shape accuracy has come to be emphasized as a problem of the photomask manufacturing and inspection technology.

[0005] The mask pattern shape is inspected in the mask inspection step by the following method. First, the items of the mask shape will be described. When the pattern shape is expressed as an inspection item on the mask quality, there are various items. For example, the roundness (=
There are items to be checked for each part of the pattern, such as corner shape roundness, jaggedness (= edge roughness) of a linear pattern edge, pattern misalignment (= batting error) during drawing, shape distortion, and tapered shape. Note that items in parentheses are item names usually used in the photomask inspection process.

Next, the inspection process will be described. FIG. 3 shows a flow of the pattern shape inspection process in the current photomask inspection process. First, in a high magnification microscope inspection 31, the shape of a mask pattern is observed using an optical microscope. Generally, the pattern is visually observed at a magnification of about 600 to 1000 times, and abnormalities are found in items such as jagged pattern and tapered shape of the pattern edge (a shape in which the pattern edge is obliquely etched rather than perpendicularly), and roundness of the pattern corner. Determine if there is any. In this case, the shape is determined by visual inspection of the inspector.

Next, in the defect inspection 32, the presence or absence of a defect is inspected by using an automatic defect inspection machine. At this time, the defective portion can be observed with a monitor screen of the inspection machine and an attached optical microscope, and the abnormal shape can be observed. Can be determined. However, since only the defect part detected by the automatic defect inspection machine is observed, emphasis is placed on judging whether it is a pseudo defect or not, and any abnormal shape is only detected by chance when it stands out. Lack of sex. Here, the pseudo defect is a defect that is detected as a defect by the inspection machine, but is determined to be not a true defect by detailed observation. In most cases, the cause of a pseudo defect is a pattern that is compared with a defective portion (the pattern is compared with a pattern on the same mask depending on the inspection period, or the pattern is compared with pattern data). This deviation is caused by the detection sensitivity / alignment accuracy of the apparatus, the pattern position accuracy, or the pattern dimensional difference.

In the above-described pattern shape inspection process, in the shape inspection using an optical microscope (including a pattern observation device such as a laser microscope or a confocal microscope which is also intended for observation at a high magnification), the judgment is as follows. Since it depends on the subjectivity of the examiner, there is a possibility that the judgment may be made differently by the examiner. Further, since the shape determination of the defective portion by the defect inspection machine is also performed by the subjective determination by the inspector, there is a similar problem. Further, when the shape is determined by the defect inspection machine, there is a problem that only a portion detected as a defect can be determined. Also, in order to detect a pattern shape abnormality compared to a defect, it is necessary to observe a portion smaller than the defect, and for that purpose, inspection must be performed with high sensitivity exceeding the standard of the defect, and a minute A serious problem occurs in that defects are excessively detected, inspection time increases, and throughput decreases. Furthermore, the number of pseudo defects may increase. As described above, the inspection by the defect inspection machine is insufficient for detecting the pattern shape.

In the above-described shape inspection process, the judgment is subject to the examiner's subjectivity, so that there is a possibility that the judgment may vary depending on the inspector. The fundamental problem of such an inspection method is that it is not possible to numerically express it for objective evaluation, that is, it is not possible to quantitatively measure the characteristic value of the pattern shape and accurately evaluate it.
In the case of other quality items, the defect is the number and size of defects, the dimension is the dimension value, the alignment is the deviation amount, etc. However, since no clear standard has been established, there is a problem that a sensory inspection method based on visual observation by an inspector is used.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been made in view of the above circumstances. An object of the present invention is to provide a shape measurement and evaluation device, a shape measurement and evaluation method, and a recording medium that records a shape measurement and evaluation program.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. According to a first aspect of the present invention, in a mask pattern shape measuring and evaluating apparatus, mask pattern image data is input and processed by a computer. A mask pattern shape measurement / evaluation apparatus characterized in that a pattern shape is evaluated by extracting predetermined pattern characteristic values after extracting the pattern shape data.

According to the second aspect of the present invention, the first aspect is provided.
In the mask pattern shape measurement and evaluation device, image input means for inputting mask pattern image data, pattern shape extraction processing means for computer processing the mask pattern image to extract shape data of an arbitrary pattern from a predetermined image area, Shape measurement means for computer processing the pattern shape data to measure a predetermined shape characteristic value,
A mask pattern shape measurement / evaluation apparatus comprising a shape evaluation means for recording and analyzing and evaluating measured shape characteristic value data.

According to a third aspect of the present invention, in the mask pattern shape measuring and evaluating apparatus according to the first aspect, a mask pattern is photographed, and the photographed mask pattern is converted into digital data to generate mask pattern image data. Is output and the mask pattern image data is input.

According to a fourth aspect of the present invention, in the mask pattern shape measuring and evaluating apparatus according to the second aspect, a mask pattern observing means for photographing the mask pattern, and converting the photographed mask pattern into digital data. And external image output means for outputting mask pattern image data, and the mask pattern image data is inputted by an image input means.

According to a fifth aspect of the present invention, in the mask pattern shape measuring and evaluating method, pattern shape data of an arbitrary image area is extracted from the mask pattern image data.
This is a mask pattern shape measurement and evaluation method characterized by analyzing and evaluating a pattern shape by measuring predetermined shape characteristic value data by computer processing.

The invention according to claim 6 of the present invention is directed to the above-mentioned claim 5.
In the mask pattern shape measurement and evaluation method, edge detection processing, smoothing processing, binarization processing, contour extraction processing,
A method for measuring and evaluating a mask pattern shape is characterized in that pattern shape data is extracted by using a combination of image processing techniques such as thinning processing and the like.

According to a seventh aspect of the present invention, there is provided a recording medium on which a shape measurement evaluation program for measuring and evaluating a shape of a mask pattern is recorded by a program, wherein the shape measurement evaluation program causes a computer to input mask pattern image data. After processing and extracting pattern shape data, a predetermined shape characteristic value is measured and processed to evaluate the pattern shape, and a recording medium storing a mask pattern shape measurement evaluation program. It was done.

According to an eighth aspect of the present invention, there is provided a recording medium on which the mask pattern shape measuring and evaluating program according to the seventh aspect is recorded, wherein the shape measuring and evaluating program causes a computer to input mask pattern image data. Pattern shape extraction processing means for processing the mask pattern image and extracting shape data of an arbitrary pattern from a predetermined image region; shape measurement means for processing the pattern shape data to measure a predetermined shape characteristic value; And a shape evaluation means for recording and analyzing and evaluating the measured shape characteristic value data. The present invention provides a recording medium storing a mask pattern shape measurement evaluation program.

According to a ninth aspect of the present invention, there is provided a recording medium on which the mask pattern shape measuring and evaluating program according to the seventh aspect is recorded, wherein the mask pattern shape measuring and evaluating program causes a computer to photograph a mask pattern. And converting the mask pattern into digital data, outputting mask pattern image data, and inputting the mask pattern image data.

According to a tenth aspect of the present invention, there is provided a recording medium storing the mask pattern shape measuring and evaluating program according to the eighth aspect, wherein the mask pattern shape measuring and evaluating program causes a computer to photograph a mask pattern. Means for converting the photographed mask pattern into digital data to output mask pattern image data, wherein the mask pattern image data is input by image input means. This is a recording medium on which a shape measurement evaluation program is recorded.

According to an eleventh aspect of the present invention, there is provided a recording medium on which a shape measurement and evaluation program for measuring and evaluating the shape of a mask pattern by a computer is recorded. Edge detection processing,
The pattern shape data of an arbitrary image area is extracted by using a combination of image processing techniques such as smoothing processing, binarization processing, contour extraction processing, and thinning processing. A recording medium on which the mask pattern shape measurement evaluation program according to any one of the above items is recorded.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing one embodiment of the configuration of the mask pattern shape measurement and evaluation apparatus of the present invention. In FIG. 1, the inside of a dotted line indicates the shape measurement / evaluation apparatus main body 1. The target mask pattern image data is sent from the mask pattern observation device 2 to the shape measurement evaluation device main body 1 via the external image output device 3. The mask pattern observing device may be any device having an observing function and image photographing usually used in a mask inspection process, or an image photographing device provided as an option outside the observing device may be used. For example, the above-mentioned optical microscope, automatic defect inspection machine, or length measuring SEM (electron microscope) are often used because they often satisfy these functions. The target mask pattern is observed using the mask pattern observation device 2, an image is taken, and the image is sent to the external image output device 3. When an image captured by the observation device 2 is output as analog data such as a photograph, the image is converted into a digital image by the external image output device 3 and the shape measurement and evaluation device main body 1
Send to As the external image output device 3, a computer system or the like to which a scanner is connected is used. Here, the image data is an image of the observed mask pattern, and the digital image data has a predetermined format (in most cases, a bitmap format, and a compression format may be used). It is recorded in pixel units. The conversion of image data from analog to digital can be technically converted by either hardware or software.
Either one may be selected and the conversion may be performed at any stage. When the digital image output function is directly incorporated in the mask pattern observation device 2, the external image output device 3 becomes unnecessary. Further, the mask pattern observation device 2 and the external image output device 3 may be incorporated in the shape measurement and evaluation device main body 1.

Next, the image data sent to the shape measuring and evaluating apparatus main body 1 is input by selecting desired image data in the image input means 4. Here, when there are a plurality of pieces of the photographed image data, a desired processing order is selected from the plurality of photographed image data. When the image range is wide, only a desired pattern area is cut out, or the image quality is inappropriate. In such a case, an image that appropriately optimizes subsequent processing, such as performing appropriate image processing using various image conversion means, is selected and input.

From the input image data, shape data for measuring the pattern shape is extracted by the pattern shape extraction processing means 5. The shape data is such that only contour lines of a pattern are extracted based on the image data, and is realized by using shape extraction processing software combining various image processing algorithms.

Here, the shape data will be described with reference to FIG. FIG. 4A shows an example of a design drawing of a mask pattern, in which a rectangular design pattern is arranged. The size of the pattern is close to the state-of-the-art device rules in current microfabrication technology, for example, 0.8 μm at present
Near. The reason for such a size is that as described above, the finer the pattern rule, the greater the effect of the shape accuracy, which is considered to be a problem. FIG. 4B is a mask pattern image in which the design pattern is formed on a mask. The four corners of the mask pattern are rounded as shown. This is called the corner roundness,
This phenomenon is peculiar to the lithography technology, and occurs because the shape accuracy is somewhat degraded in each step of electron beam drawing, development, etching and the like. FIG.
(C) shows shape extraction data obtained by extracting an outline from the mask pattern image of (b). The shape extraction data is generated by using a known digital image processing technique in combination based on the mask pattern image. The basic image processing procedure for extracting the shape is to perform image processing in the order of edge detection processing, binarization processing, and thinning processing. However, the optimal procedure for shape extraction may be set by changing the processing procedure depending on the image quality, using a different image processing algorithm, or by appropriately combining the processing procedures. The shape extraction data generated in this way is only binary data of the outline portion of the shape and the other portion. The data format may be a bitmap format in pixel units or a format similar thereto, or may be converted to a vector data format depending on the intended use.

Next, the description returns to FIG. Using the pattern shape data extracted by the pattern shape extraction processing means 5, the shape measuring means 6 measures a predetermined shape characteristic value. There are a plurality of shape characteristic values measured here, which are appropriately selected according to the graphic characteristics of the pattern. An example of the shape characteristic value and the measurement processing will be described later. Next, the shape evaluation means 7 analyzes and evaluates the measured shape characteristic value. That is, whether the characteristic value of the pattern shape extracted and measured from the mask pattern image is within the standard, or comparison with another pattern similarly measured is performed.

In the above description of FIG. 1, all means and processing in the apparatus main body 1 are controlled by the control processor 8. The operator can confirm and judge these means and processing contents through the screen of the monitor 9, the processing instruction can be sent using the input means 10, and the processing result can be output using the output means 11. Further, these processing contents can be appropriately selected and the information can be stored by the information recording means 12. Note that a general computer input device such as a keyboard and a mouse may be used as the input unit 10, and an output device such as a printer and a floppy (registered trademark) disk may be used as the output unit 11. A large-capacity recording medium is suitable for the information recording means 12, and it is desirable to store data in a hard disk, a network file server, or the like. With the above-described apparatus configuration, it is possible to extract pattern shape data from a mask pattern image and measure and evaluate a desired shape characteristic value.

FIG. 2 is a flow chart showing an embodiment of the procedure of the mask pattern shape measurement and evaluation method of the present invention. First, in the pattern shape observation 21 of FIG. 2, a target photomask is observed using an observation device capable of high-magnification observation such as an optical microscope or a length measuring SEM. At this time, a pattern whose shape is to be measured is determined, and image data is generated using an image capturing function of the observation device. Alternatively, if the image is a photograph, the photograph can be scanned using a scanner and converted into image data. Next, in the image data conversion 22, if the image data is analog data such as a photograph or a scanning line image, the image is captured using a scanner or the like and converted into digital image data. This is because image data needs to be converted into digital information for computer processing. Then, in a pattern shape extraction process 23, the data is processed using a predetermined image processing algorithm to extract pattern shape data. Next, in a shape measurement process 24, various shape characteristic values are measured based on the pattern shape data.
The measurement result is evaluated under predetermined conditions in the shape evaluation 25. If the shape characteristic value is within the criterion, the result is judged as pass. In this shape evaluation, not only a single shape characteristic value but also a plurality of characteristic value data can be analyzed and evaluated using a statistical method. The measurement and evaluation of the pattern shape could be performed by the above procedure.

FIG. 5 is a diagram showing examples of some shape characteristic values from the extracted pattern shape data. These are only a part of those defined as shape characteristic values, and it is also possible to measure other shape characteristic values from the same pattern shape data. That is, it is possible to define and measure a new shape characteristic value from a pattern shape by creating a corresponding software program in the same procedure. FIG. 5A shows the shape characteristic values of the corner roundness. a and b represent the horizontal and vertical lengths of the corner portion, respectively, and s represents the area of the portion missing from the original pattern due to roundness. These characteristic values can be measured by detecting the part where the contour of the pattern shape changes in a curve and determining the difference from the case of the linear shape, and creating a computer program for that purpose. Processed. FIG. 5B shows a case where the jaggedness (edge roughness) of the pattern edge portion is measured. When the pattern edge is jagged as shown in the figure, an average line thereof is obtained, and further, the edge roughness can be calculated by using a statistical method such as a maximum swing width or an average swing width. FIG. 5C shows a shift of a pattern connection portion which occurs in a pattern drawing process by electron beam drawing. In this figure, there is a step difference due to drawing deviation in the right and left halves of the pattern, and c and d indicate the upper and lower deviation amounts, respectively. These may be obtained by measuring the displacement of the straight line portion in the vertical direction.

[0030]

As described above, in the inspection process of the mask pattern shape, by using the mask pattern shape measuring and evaluating apparatus, the shape measuring and evaluating method or the recording medium in which the shape measuring and evaluating program of the present invention is recorded, it is possible to perform a conventional microscope observation. The pattern shape inspection, which has been performed by sensory inspection by means of inspection or observation of only a defective portion by a defect inspection device, can be quantitatively measured, and accurate and highly accurate evaluation has become possible. Further, it is possible to newly define and measure a desired shape characteristic value only by creating a corresponding software program.

[Brief description of the drawings]

FIG. 1 shows a mask pattern shape measurement and evaluation apparatus 1 of the present invention.
FIG. 3 is a block diagram illustrating a configuration example of an embodiment.

FIG. 2 shows a mask pattern shape measurement evaluation method 1 of the present invention.
6 is a flowchart illustrating a procedure of the embodiment.

FIG. 3 is a flowchart illustrating a conventional pattern shape inspection process.

FIG. 4 is an explanatory diagram showing that a photomask pattern is created from design data of a mask pattern, and further that shape data of the mask pattern is extracted.

FIG. 5 is an explanatory view showing the concept of measuring three types of pattern shape characteristic values.

[Explanation of symbols]

1 ... Main body of shape measurement and evaluation device 2 ...
Mask pattern observation device 3 ... External image output device 4 ... Image input means 5 ... Pattern shape extraction processing means 6 ... Shape measurement means 7 ... Shape evaluation means 8 ... Control processor 9 ..Monitor 10 ... Input means 11 ... Output means 12 ... Information recording means 21 ... Pattern shape observation 22 ... Image data conversion 23 ... Pattern shape extraction processing 24 ...
・ Shape measurement processing 25 ・ ・ ・ Shape evaluation 31 ・ ・ ・ High magnification microscope inspection 32 ・ ・ ・ Defect inspection

Continued on front page F-term (reference) 2F065 AA49 AA56 BB02 CC18 JJ03 QQ03 QQ04 QQ21 QQ23 QQ24 QQ32 QQ42 RR05 RR08 5B057 AA03 BA11 CE05 CE12 CF01 CH01 CH11 DA03 DB02 DC03 DC09 DC16

Claims (11)

[Claims] In a mask pattern shape measuring and evaluating apparatus, mask pattern image data is input, computer-processed to extract pattern shape data, and a predetermined shape characteristic value is measured and processed. A mask pattern shape measurement and evaluation device, characterized in that: 2. An apparatus for measuring and evaluating a mask pattern shape according to claim 1, wherein: an image input means for inputting mask pattern image data; and computer processing of the mask pattern image to obtain shape data of an arbitrary pattern from a predetermined image area. Pattern shape extraction processing means to be extracted; shape measurement means for computer processing the pattern shape data to measure a predetermined shape characteristic value; and shape evaluation means for recording and analyzing and evaluating the measured shape characteristic value data. A mask pattern shape measurement and evaluation device, characterized in that: 3. The mask pattern shape measuring and evaluating apparatus according to claim 1, wherein the mask pattern is photographed, the photographed mask pattern is converted into digital data, and mask pattern image data is output. A mask pattern shape measurement and evaluation device characterized by inputting data. 4. A mask pattern shape measuring and evaluating apparatus according to claim 2, wherein the mask pattern observing means for photographing the mask pattern, and converting the photographed mask pattern into digital data to output mask pattern image data. An external image output means, and the mask pattern image data is input by an image input means. 5. A mask pattern shape measurement and evaluation method, wherein pattern shape data of an arbitrary image area is extracted from mask pattern image data, and predetermined shape characteristic value data is measured and processed by computer processing to analyze the pattern shape. A mask pattern shape measurement evaluation method characterized by evaluating. 6. The mask pattern shape measurement and evaluation method according to claim 5, wherein the mask pattern image data is subjected to edge detection processing, smoothing processing by computer processing,
A mask pattern shape measurement / evaluation method characterized by extracting pattern shape data by using a combination of image processing techniques such as a value conversion process, a contour extraction process, and a thinning process. 7. A recording medium on which a shape measurement evaluation program for measuring and evaluating a shape of a mask pattern by a program is recorded. The shape measurement evaluation program causes a computer to input mask pattern image data, process the mask pattern image data, and process the pattern data. A recording medium on which a mask pattern shape measurement evaluation program is recorded, wherein a pattern shape is evaluated by measuring predetermined shape characteristic values after extracting data. 8. A recording medium on which the mask pattern shape measurement / evaluation program according to claim 7 is recorded, said shape measurement / evaluation program processing means for inputting mask pattern image data to a computer, and processing the mask pattern image. Pattern shape extraction processing means for extracting shape data of an arbitrary pattern from a predetermined image area, and shape measurement means for processing the pattern shape data to measure a predetermined shape characteristic value; A recording medium recording a mask pattern shape measurement evaluation program, comprising: a shape evaluation means for performing recording and analysis evaluation. 9. A recording medium recording the mask pattern shape measurement evaluation program according to claim 7, wherein the mask pattern shape measurement evaluation program causes a computer to photograph a mask pattern, and converts the photographed mask pattern into digital data. A recording medium on which a mask pattern shape measurement evaluation program is recorded, wherein the mask pattern image data is converted and output, and the mask pattern image data is input. 10. A recording medium on which the mask pattern shape measurement and evaluation program according to claim 8 is recorded, said mask pattern shape measurement and evaluation program comprising: a mask pattern observation means for causing a computer to photograph a mask pattern;
External image output means for converting the photographed mask pattern into digital data and outputting mask pattern image data, wherein the mask pattern image data is input by image input means. A recording medium on which a program is recorded. 11. A recording medium recording a shape measurement evaluation program for measuring and evaluating a mask pattern shape by a computer, wherein the mask pattern shape measurement evaluation program causes the computer to perform edge detection processing and smoothing on the mask pattern image data. The pattern shape data of an arbitrary image area is extracted by using a combination of image processing techniques such as image processing, binarization processing, contour extraction processing, and thinning processing.
0. A recording medium on which the mask pattern shape measurement evaluation program according to any one of 0 is recorded.