JP2009294123A - Pattern discriminator, pattern discriminating method and inspection device of sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discriminate a specific pattern from patterns of a sample using a transmitted image and a reflected image. <P>SOLUTION: This pattern discriminator includes an optical image acquiring part for simultaneously acquiring the transmitted image and reflected image of the sample having the pattern and a specific pattern discriminating part for discriminating the specific pattern from the pattern shapes of the transmitted image and the reflected image by the discriminating condition of the specific pattern. This inspection device of the sample includes an optical image acquiring part for simultaneously acquiring the optical images of the transmitted image and reflected image of the sample having the pattern, the specific pattern discriminating part for discriminating the specific pattern from the pattern shapes of the transmitted image and the reflected image by the discriminating condition of the specific pattern, a specific inspection executing region setting part for setting the specific pattern to a specific inspection executing region, and a comparative determining part for inspecting the patterns of the optical images obtained by the optical image acquiring part in the specific inspection executing region. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to identification and inspection of a pattern of a sample, and more particularly to identification and inspection of a pattern such as a photomask, a wafer, or a liquid crystal substrate used when manufacturing a semiconductor element or a liquid crystal display (LCD).

  Patterns that make up large scale integrated circuits (LSIs) are on the order of submicrons to nanometers. One of the major causes of a decrease in yield in the manufacture of LSI is a defect of a photomask used when an ultrafine pattern is exposed and transferred onto a semiconductor wafer by a photolithography technique. In particular, with the miniaturization of the pattern dimensions of LSIs formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small.

  On the other hand, with the development of multimedia, LCDs are increasing in size of liquid crystal substrates and miniaturization of patterns such as TFTs formed on the liquid crystal substrates. Therefore, it is required to inspect a very small pattern defect over a wide range.

For this reason, there is an urgent need to develop a sample inspection apparatus that efficiently inspects defects of a high-precision photomask in a short time. Therefore, it is known to inspect a pattern by changing the inspection accuracy using the feature of the pattern (see Patent Documents 1 to 5).
JP2004-191957 JP2007-072173 JP2007-072232A JP2007-086534 JP2007-102153

(1) The present invention is to identify a specific pattern from a pattern of a sample using a transmission image and a reflection image.
(2) Further, the present invention is to optimize inspection sensitivity for a specific pattern of a sample.

(1) In the embodiment of the present invention, an optical image acquisition unit that simultaneously acquires a transmission image and a reflection image of a sample having a pattern, and a specific pattern is identified from the pattern shape of the transmission image and the reflection image by a specific pattern identification condition And a specific pattern identification unit.
(2) In the embodiment of the present invention, a transmission pattern and a reflection image of a sample having a pattern are simultaneously acquired, and a specific pattern is identified from the pattern shape of the transmission image and the reflection image according to a specific pattern identification condition. In the identification method.
(3) In the embodiment of the present invention, the optical image acquisition unit that simultaneously acquires the transmission image of the sample having a pattern and the optical image of the reflection image, and the pattern shape of the transmission image and the reflection image according to the identification condition of the specific pattern The specific pattern identifying unit for identifying the specific pattern from the above, the specific inspection execution region setting unit for setting the specific pattern in the specific inspection execution region, and the pattern inspection of the optical image acquired by the optical image acquisition unit in the specific inspection execution region A sample inspection apparatus including a comparison determination unit.
(4) In the embodiment of the present invention, an optical image acquisition unit that simultaneously acquires a transmission image of a sample having a pattern and an optical image of a reflection image, and pattern inspection of the optical image acquired by the optical image acquisition unit are performed. A comparison / determination unit that extracts a portion determined to be a defect, a specific pattern identification unit that identifies a specific pattern from a pattern shape of a transmission image and a reflection image according to a specific pattern identification condition, and a defect If the region is a specific pattern, the sample inspection apparatus includes a specific inspection execution unit that executes a specific inspection.

(1) In the present invention, a specific pattern can be identified from a pattern of a sample using a transmission image and a reflection image.
(2) Further, the present invention can optimize the inspection sensitivity for a specific pattern of a sample.

Hereinafter, the details of the present invention will be described with reference to embodiments.
(Sample pattern identification device)
FIG. 1 is a block diagram illustrating a sample inspection apparatus 10 including a pattern identification apparatus 20 according to an embodiment of the present invention. The pattern identification device 20 includes an optical image acquisition unit 110 that acquires optical images of the transmission image 22 and the reflection image 24 from the pattern of the inspection target sample 100 such as a photomask, a wafer, or a liquid crystal substrate, and the transmission image 22 and the reflection image 24. And a specific pattern identification unit 40 for identifying a specific pattern using the specific pattern identification condition 36. The specific pattern identification condition 36 is a condition for identifying a specific pattern using the optical characteristics of the specific pattern. The specific pattern is a pattern that requires special processing in the pattern of the sample 100. For example, when the pattern area is small or thin, the transmission image 22 and the reflection image 24 of the pattern are mutually imaged. Appears as pattern images with different areas. By using the optical characteristics of the transmission image 22 and the reflection image 24, it is possible to identify a specific pattern.

  The specific pattern is a pattern having a pattern shape, pattern size, etc., and taking a rectangular pattern as an example, it is relatively large with respect to the main pattern contact hole and main pattern, so as to fill the space on the mask. There are accessory patterns that exist, assist patterns that are relatively small, and are added to the main pattern. In these determination processes, rectangular patterns are first extracted as specific pattern candidates, and then classified into three specific patterns of assist, main, and accessory according to size.

  Desense inspection that lowers sensitivity is desired for accessory patterns and assist patterns, while high inspection sensitivity is required for contact holes. When design data with a defined size is obtained, the design data can be utilized, but the present invention obtains the size from the optical image in the case of DD inspection or when the data with the defined size cannot be obtained, Assist, determine specific patterns such as main and accessories. In the conventional method, when a specific pattern is to be inspected by performing a specific process, data indicating which specific pattern is required is required, and can be used when data cannot be obtained by DD inspection or DB inspection. There wasn't.

  As an example of the determination process, there is the following method. Here, the total amount of light transmitted or reflected by the pattern is called a volume. In general, in an optical system that simultaneously acquires a transmission image and a reflection image, the volume ratio (R = Vt / Vr) of the transmission volume (Vt) and the reflection volume (Vr) decreases as the pattern size becomes the same as the wavelength of the inspection light. It changes depending on the physical phenomenon. Since this change depends on the pattern size, the approximate pattern size can be known by measuring this change.

  The sample inspection apparatus 10 includes a pattern identification device 20, compares the transmission image 22 and the reflection image 24 with a comparison / determination unit 180, inspects a defect in the pattern of the sample, and obtains inspection result information 54. At this time, more appropriate pattern inspection can be performed using the information 52 of the specific inspection execution area including the specific pattern. The specific inspection execution area information 52 is obtained by the specific inspection execution area setting unit 50 using the specific pattern identification information 42 obtained from the pattern identification device 20.

  The specific inspection is a special process performed on a specific pattern, for example, a process for changing the accuracy of the pattern inspection, such as a process for loosening or tightening the inspection accuracy. Alternatively, the specific inspection is processing for changing an inspection method or means, for example, processing specialized for pattern width, positional deviation, edge roughness, volume, and the like. For example, the specific inspection is an inspection for determining a defect depending on whether or not there is a difference in volume between corresponding patterns when optical images are compared and inspected. This inspection is effective when the amount of light transmitted through the pattern only needs to be the same even if the pattern shapes are slightly different. The specific inspection execution area setting unit 50 sets an area for performing such an inspection.

  1 uses the transmission image 22 and the reflection image 24 to inspect defects in the pattern of the sample, but various comparison methods that are usually performed can be used. For example, a comparison between transmission images, a comparison between reflection images, or a comparison between a reference image obtained from design data of a pattern of a sample and an optical image (transmission image or reflection image) may be used. In that case, the sample inspection apparatus 10 is the same as the comparison between the transmission image 22 and the reflection image 24 in that the specific inspection execution area 52 is used for comparison.

  FIG. 2 shows a procedure of a sample inspection method related to the sample inspection apparatus 10 of FIG. In the sample inspection method, the specific pattern identification condition setting unit 30 first sets a specific pattern identification condition 36 using the representative image 32 and the sample information 34 (S1). Taking a rectangular pattern as an example, some accessories, mains, and assists are appropriately picked up and pointed to the inspection device before inspection. The inspection apparatus obtains a transmission volume and a reflection volume for each of the indicated patterns, and then determines a boundary condition as a boundary value thereof. As the boundary value between the assist pattern and the main pattern, a value between the intermediate values of the volumes (referred to as a boundary volume value) is determined. In addition, as a boundary value between the main pattern and the accessory pattern, a value between the intermediate values of these volumes (referred to as a boundary volume value) is determined.

  Regardless of before and after step S1, the optical image acquisition unit 110 acquires the transmission image 22 and the reflection image 24 from the inspection target sample 100 (S2). The specific pattern identifying unit 40 extracts a specific pattern using the transmission image 22, the reflection image 24, and the boundary volume value (S3). The specific inspection execution area setting unit 50 sets a specific pattern in the specific inspection execution area (S4). Finally, in the comparison processing unit 180, the specific inspection execution area information 52 is used to perform a specific inspection such as loosening the inspection accuracy in the case of an accessory pattern or assist pattern, and stricter inspection accuracy in the case of a main pattern. Then, the transmission image 22 and the reflection image 24 are compared and determined to obtain the inspection result 54 of the sample pattern (S5). The specific pattern identification condition setting unit 30 is provided outside the pattern identification device 20 in FIG. 1, but may be provided inside the pattern identification device 20.

  3 is the same as FIG. 1 in that the pattern identification device 20 is used, but the means and method for sample inspection are different. The sample inspection apparatus 10 in FIG. 3 inspects the defect of the pattern of the sample by comparing the transmission image 22 and the reflection image 24 by the comparison determination unit 180. This inspection is obtained as provisional inspection result information 56, not the final inspection. The specific pattern identification unit 40 of the pattern identification device 20 refers to the provisional inspection result information 56 and the specific pattern identification condition 36 to identify a specific pattern from the transmission image 22 and the reflection image 24 and obtain specific pattern identification information 42. The sample inspection apparatus 10 includes a specific inspection execution unit 60, and uses the temporary inspection result information 56 and the specific pattern identification information 42 to obtain final inspection result information 62 that is a final inspection result. The sample inspection apparatus 10 in FIG. 3 can use various comparison methods that are usually performed in addition to the comparison between the transmission image 22 and the reflection image 24 as in the sample inspection apparatus 10 in FIG.

  FIG. 4 shows the procedure of the sample inspection method related to the sample inspection apparatus 10 of FIG. In the sample inspection method, as in step S1 of FIG. 2, the specific pattern identification condition setting unit 30 first sets a specific pattern identification condition 36 using the representative image 32 and the sample information 34 (S11). Regardless of before and after step S11, the optical image acquisition unit 110 acquires the transmission image 22 and the reflection image 24 from the specimen 100 to be inspected (S12). In the comparison processing unit 180, the transmission image 22 and the reflection image 24 are compared and determined to obtain a provisional inspection result 56 of a portion estimated to be a defect in the pattern of the sample (S13). In the specific pattern identification unit 40, the specific pattern identification information 42 is obtained for the defective part using the transmission image 22, the reflection image 24, and the specific pattern identification condition 36 (S14). Finally, the specific inspection execution unit 60 executes the specific inspection if the defective part is on the specific pattern, and obtains definite inspection result information 62 (S15).

(Configuration of sample inspection equipment)
FIG. 5 is a conceptual diagram showing an internal configuration of the sample inspection apparatus 10. The sample inspection apparatus 10 inspects a pattern defect of the sample 100 using a substrate such as a mask or a wafer as the sample 100. The sample inspection apparatus 10 includes an optical image acquisition unit 110, a control system circuit 150, and the like. The optical image acquisition unit 110 includes an autoloader 112, an illumination device 114 that generates illumination light, an illumination device 1140 that generates reflected illumination light, an XYθ table 116, an XYθ motor 118, a laser length measurement system 120, an enlargement optical system 122, A piezo element 124, a CCD that receives the transmitted light 22 and the reflected light 24, a light receiving device 126 having a sensor such as a photodiode array, a sensor circuit 128, and the like are provided.

  In the control system circuit 150, a CPU 152 serving as a control computer is connected to a mass storage device 156, a memory device 158, a display device 160, a printing device 162, an autoloader control unit 170, and a table control unit via a bus 154 serving as a data transmission path. 172, autofocus control unit 174, development unit 176, reference unit 178, comparison determination unit 180, position unit 182, specific pattern identification condition setting unit 30, specific pattern identification unit 40, specific inspection execution region setting unit 50, specific inspection execution Part 60 and the like. Further, the development unit 176, the reference unit 178, the comparison determination unit 180, and the position unit 182 are connected to each other as shown in FIG. The optical image acquisition unit 110 in FIGS. 1 and 3 can be configured by the optical image acquisition unit 110 in FIG. In FIG. 5, description of components other than those necessary for describing the present embodiment is omitted. The sample inspection apparatus 10 usually includes other necessary configurations.

(Operation of optical image acquisition unit)
The sample 100 is automatically transported from the autoloader 112 driven by the autoloader control unit 170 and placed on the XYθ table 116. The sample 100 is irradiated with light from above to obtain transmitted light by the illumination device 114, and is irradiated with light from below to obtain reflected light by the illumination device 1140. Below the sample 100, an enlargement optical system 122, a light receiving device 126, and a sensor circuit 128 are arranged. Light that has passed through or reflected by the sample 100 such as an exposure mask forms an optical image on the light receiving device 126 via the magnifying optical system 122. The autofocus control unit 174 controls the piezo element 124 to absorb the deflection of the sample 100 and the change in the Z-axis (perpendicular to the X-axis and Y-axis) direction of the XYθ table 116, thereby focusing on the sample 100. Align.

  The XYθ table 116 is driven by the table control unit 172 under the control of the CPU 152. It can be moved by a drive system such as a three-axis (XY-θ) motor 118 that drives in the X-axis direction, the Y-axis direction, and the θ-direction. For example, step motors can be used as these X motor, Y motor, and θ motor. The movement position of the XYθ table 116 is measured by the laser length measurement system 120 and supplied to the position unit 182. The light receiving device 126 acquires pattern electronic data. The sensor circuit 128 outputs electronic data of the optical image as an optical image. The optical images of the transmission image 22 and the reflection image 24 output from the sensor circuit 128 are sent to the comparison determination unit 180 together with data indicating the position of the sample 100 on the XYθ table 116 output from the position unit 182. The sample 100 on the XYθ table 116 is automatically discharged by the autoloader control unit 170 after the inspection is completed. Note that the optical image is, for example, 8-bit unsigned data, and expresses the brightness gradation of each pixel.

  FIG. 6 is a diagram for explaining an optical image acquisition procedure. The inspection area of the sample 100 is virtually divided by the scan width W in the Y-axis direction. That is, the inspection area is virtually divided into a plurality of strip-like stripes 102 having a scan width W. Further, the XYθ table 116 is controlled so that the divided stripes 102 are continuously scanned. The XYθ table 116 moves along the X axis, and an optical image is acquired as the stripe 102. In FIG. 6, the stripe 102 has a rectangular shape having a scan width W in the Y-axis direction and a longitudinal direction having a length in the X-axis direction. The light transmitted through the sample 100 or the light reflected by the sample 100 enters the light receiving device 126 through the magnifying optical system 122. The light receiving device 126 continuously receives images with a scan width W as shown in FIG. After acquiring the image in the first stripe 102, the light receiving device 126 continuously inputs the image having the scan width W while moving the image in the second stripe 102 in the opposite direction. When acquiring the image in the third stripe 102, the image is acquired while moving in the direction opposite to the direction in which the image in the second stripe 102 is acquired, that is, in the direction in which the image in the first stripe 102 is acquired. To do. The scan width W is about 2048 pixels, for example.

(Reference image generation)
The design data used when the pattern of the sample 100 is formed is stored in the mass storage device 156. The design data is input from the mass storage device 156 to the expansion unit 176 by the CPU 152. As a design data development process, the development unit 176 converts the design data of the sample 100 into binary or multivalued original image data, and the original image data is sent to the reference unit 178. The reference unit 178 performs an appropriate filter process on the original image data, and generates a reference image similar to the optical image. It can be said that the optical image obtained from the sensor circuit 128 is in a state in which a filter acts due to the resolution characteristics of the magnifying optical system 122, the aperture effect of the light receiving device 126, and the like. In this state, since there is a difference between the optical image and the original image data on the design side, a filtering process is performed on the original image data on the design side by the reference unit 178 to match the optical image.

(Identification of specific patterns)
FIG. 7 is a schematic example of a sample 100 having a rectangular specific pattern, and shows a sample 100 with an assist pattern 14, a main pattern 16, and an accessory pattern 18. FIG. 8A shows a transmission image 22 of the assist pattern 14a, the main pattern 16a, and the accessory pattern 18a. FIG. 8B shows a reflected image 24 of the assist pattern 14b, the main pattern 16b, and the accessory pattern 18b.

  In the accessory pattern 18 of the transmission image of FIG. 8A and the reflection image of FIG. 8B, the main pattern 16 and the assist pattern 14, the volume ratio of the transmission volume (Vt) to the reflection volume (Vr) (R = Vt / Vr) is obtained. The accessory pattern volume ratio R = Vt / Vr = 1, the main pattern volume ratio R = Vt / Vr = 0.6, and the assist pattern volume ratio R = Vt / Vr = 0.25.

  Here, before the inspection, some accessories, mains, and assists are appropriately picked up, and a boundary volume ratio Rth = 0.8, which is a boundary between the accessory pattern and the main pattern, is obtained in advance. Further, a boundary volume ratio Rth = 0.4, which is a boundary between the main pattern and the assist pattern, is obtained in advance. The accessory pattern, the main pattern, and the assist pattern can be identified by the boundary volume ratio Rth.

  As described above, the identification of the specific pattern has been described using the sample of the blank pattern, but the boundary volume ratio Rth between the accessory pattern, the main pattern, and the assist pattern should be obtained in advance for the sample of the remaining pattern. Thus, the specific pattern can be identified by the same method.

  In the above description, what is described as “to part”, “to circuit” or “to process” and “to step” can be configured by a computer-operable program. Or you may make it implement by not only the program used as software but the combination of hardware and software. Alternatively, a combination with firmware may be used. Alternatively, a combination of these may be realized. When configured by a program, the program is recorded on a recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (Read Only Memory).

  The present invention is not limited to the specific examples described above. Descriptions of parts that are not directly necessary for the description of the present invention, such as the apparatus configuration and control method, are omitted, but the required apparatus configuration and control method can be appropriately selected and used. In addition, all sample inspection apparatuses that include the elements of the present invention and whose design can be appropriately changed by those skilled in the art are included in the scope of the present invention.

It is a block diagram for demonstrating the sample inspection apparatus in embodiment. It is a figure which shows the process sequence using the sample inspection apparatus of FIG. It is a block diagram for demonstrating the other sample inspection apparatus in embodiment. It is a figure which shows the process sequence using the sample inspection apparatus of FIG. It is a lineblock diagram of the sample inspection device in an embodiment. It is explanatory drawing which acquires an optical image. It is explanatory drawing of the pattern of extraction of a test object sample. It is explanatory drawing of the pattern of a transmitted image and a reflected image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Sample inspection apparatus 14 ... Assist pattern 14a ... Assist pattern transmission image 14b ... Assist pattern reflection image 16 ... Main pattern 16a ... Main pattern transmission image 16b ... Reflection of main pattern Image 18 ... Accessory pattern 18a ... Accessory pattern transmission image 18b ... Accessory pattern reflection image 20 ... Pattern identification device 22 ... Transmission image 24 ... Reflection image 30 ... Specific pattern identification condition Setting unit 32 ... representative image 34 ... sample information 36 ... specific pattern identification condition 40 ... specific pattern identification unit 42 ... specific pattern identification information 50 ... specific inspection execution region setting unit 52 ..Specific inspection execution area information 54 ... Inspection result information 56 ... Temporary inspection result information 60 ... Special Inspection execution unit 62... Confirmed inspection result information 100... Sample 102... Stripe 110... Optical image acquisition unit 112... Autoloader 114 ... Transmission illumination device 1140 Reflection illumination device 116 XYθ table 118 XYθ Motor 120 .. Laser length measurement system 122 .. Enlargement optical system 124 .. Piezo element 126 .. Light receiving device 128 .. Sensor circuit 150 .. Control system circuit 152.
154 ·· Bus 156 · · Mass storage device 158 · · Memory device 160 · · Display device 162 · · Printing device 170 · · Autoloader control unit 172 · · Table control unit 174 · · Autofocus control unit 176 · · Expansion unit 178 ··· Reference unit 180 ·· Comparison judgment unit 182 · · Position part

Claims (4)

An optical image acquisition unit that simultaneously acquires a transmission image and a reflection image of a sample having a pattern;
A pattern identification apparatus comprising: a specific pattern identification unit that identifies a specific pattern from the pattern shape of a transmission image and a reflection image according to a specific pattern identification condition. Acquire a transmission image and a reflection image of a sample with a pattern at the same time,
A pattern identification method for identifying a specific pattern from a pattern shape of a transmission image and a reflection image according to a specific pattern identification condition. An optical image acquisition unit for simultaneously acquiring a transmission image of a sample having a pattern and an optical image of a reflection image;
A specific pattern identification unit for identifying a specific pattern from the pattern shape of the transmission image and the reflection image according to the identification condition of the specific pattern;
A specific inspection execution area setting unit for setting a specific pattern in the specific inspection execution area;
A sample inspection apparatus comprising: a comparison determination unit that performs pattern inspection of an optical image acquired by an optical image acquisition unit in a specific inspection execution region. An optical image acquisition unit for simultaneously acquiring a transmission image of a sample having a pattern and an optical image of a reflection image;
A comparison / determination unit that performs pattern inspection of the optical image acquired by the optical image acquisition unit, and extracts a portion that is regarded as a defect,
A specific pattern identification unit that identifies a specific pattern from the pattern shape of the transmission image and the reflection image according to the identification condition of the specific pattern, in a part that is a defect,
A sample inspection apparatus, comprising: a specific inspection execution unit that executes a specific inspection if a site that is a defect is a specific pattern.

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