JP2009282043A - Optical image acquisition device, pattern inspection device, optical image acquisition method, and pattern inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate the focus matching of the pattern image thrown on the light reception surface of an optical image receptor. <P>SOLUTION: This optical image acquisition device is equipped with a mounting part on which a sample to be inspected is placed, a light irradiation part for irradiating the sample to be inspected placed on the mounting part with irradiation light, an optical image receptor for receiving the irradiation light thrown on the sample to be inspected, a focus adjusting device for matching the focus of the pattern image of the sample to be inspected with the optical image detecting part, a slit image forming device for forming a slit image on the sample to be inspected and an observation display device for displaying the slit image on the sample to be inspected. The focus of the pattern image of the sample to be inspected in the optical image receptor is adjusted from the slit image on the sample to be inspected displayed on the observation display device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical image acquisition device that acquires an optical image from a pattern created on an inspection target sample such as a mask, an optical image acquisition method, a pattern inspection device that inspects a pattern defect, and a pattern inspection method. is there.

  Conventionally, in a pattern inspection apparatus, continuous light emitted from a light source such as a lamp or a continuous wave laser is guided to an inspection target sample such as a reticle or mask through an irradiation optical system, and the inspection target sample is irradiated. Here, the irradiation light irradiates a limited area on the inspection target sample in a spot shape or a rectangular shape. Irradiation light from the spot-irradiated region or rectangular region is collected through an imaging optical system and irradiated onto a light receiving surface of an optical image light receiving unit such as a CCD or TDI. Thereby, the pattern image of the irradiation area | region of a test object sample is formed on the light-receiving surface of an optical image light-receiving part. A photoelectric detection signal (image information) from the optical image light receiving unit is input to the image processing system. The image processing system performs image processing for detecting defects in the inspection target sample. However, in recent years, circuit patterns such as semiconductor manufacturing masks have become finer year by year, and the resolution required for pattern inspection apparatuses has become stricter. Therefore, in order to improve the resolution, the wavelength of the light source is shortened and the NA of the objective lens is increased. For this reason, the depth of focus is lowered due to the increase in NA, and the required accuracy for the autofocus mechanism (autofocus function) for focusing on the light receiving surface of the optical image light receiving unit is severe.

(1) An object of the present invention is to make it easy to focus a pattern image irradiated on a light receiving surface of an optical image light receiving unit.
(2) Alternatively, the present invention is to provide a highly accurate autofocus mechanism.

(1) The present invention provides an optical image acquisition apparatus that acquires an optical image of a pattern of a sample to be inspected, a placement unit on which the sample to be inspected is placed, and an irradiation light to the sample to be inspected placed on the placement unit A light irradiating unit that irradiates the sample to be inspected, an optical image receiving unit that receives the irradiation light applied to the sample to be inspected, a focus adjustment device that focuses the pattern image of the sample to be inspected on the optical image receiving unit, A slit image forming device that forms a slit image on the substrate and an observation display device that displays the slit image on the sample to be inspected. From the slit image on the sample to be inspected displayed on the observation display device, an optical image is obtained. The optical image acquisition apparatus adjusts the focus of the pattern image of the sample to be inspected in the light receiving unit.
(2) In the pattern inspection apparatus for inspecting the pattern of the inspection target sample, the present invention irradiates the mounting portion on which the inspection target sample is mounted, and the irradiation light on the inspection target sample mounted on the mounting portion. A light irradiating unit, an optical image light receiving unit that receives irradiation light irradiated on the inspection target sample, a focus adjusting device that focuses the pattern image of the inspection target sample on the optical image receiving unit, and a slit on the inspection target sample Slit image forming apparatus for forming an image, display device for observation for displaying a slit image on a specimen to be inspected, an optical image storage unit for storing an optical image, a reference image storage unit for storing a reference image, and an optical image And a comparison processing unit that compares the reference image, and adjusts the focus of the pattern image of the inspection target sample in the optical image light receiving unit from the slit image on the inspection target sample displayed on the observation display device. In the emissions inspection equipment.
(3) Further, the present invention provides an optical image acquisition method for acquiring an optical image of a pattern of an inspection target sample, a slit image forming step for forming a slit image on the inspection target sample, and irradiating the inspection target sample with irradiation light. An optical image acquisition step for forming a pattern of the specimen to be inspected in the optical image light receiving unit, a slit image display step for displaying a slit image on the specimen to be inspected, and a slit image to display the pattern image of the specimen to be inspected. And a focus adjustment step for adjusting the focus.
(4) Further, in the pattern inspection method for inspecting a pattern of an inspection target sample, the present invention provides a slit image forming step for forming a slit image on the inspection target sample, irradiating the inspection target sample with irradiation light, and receiving an optical image. An optical image acquisition step for forming a pattern of the specimen to be inspected on the part, a slit image display step for displaying a slit image on the specimen to be inspected, and a slit image to display and adjust the focus of the pattern image of the specimen to be inspected The pattern inspection method includes a focus adjustment step and a comparison processing step for comparing the optical image and the reference image.

Block diagram of pattern inspection equipment Explanatory drawing which shows the structure of an optical image acquisition apparatus Diagram of slit image and pattern image displayed on observation display device Explanatory drawing showing the overall configuration of the pattern inspection apparatus Flow chart of pattern inspection method

  Hereinafter, a pattern inspection apparatus, an optical image acquisition apparatus, a pattern inspection method, and an optical image acquisition method according to embodiments of the present invention will be described.

(Outline of pattern inspection equipment)
The pattern inspection apparatus inspects a defect of a pattern formed on a sample to be inspected. The pattern inspection apparatus includes an optical image acquisition apparatus. The optical image acquisition device irradiates a pattern formed on a sample to be inspected with light and acquires the pattern as an optical image. The sample to be inspected is a reticle such as a reticle or a photomask for transferring a fine circuit pattern onto a photosensitive substrate such as a wafer or glass, a wafer on which a pattern on the reticle such as a reticle or mask is transferred, A substrate such as glass. The pattern inspection apparatus examines defects in these original plates or substrates.

  FIG. 1 shows a block configuration of the pattern inspection apparatus. The pattern inspection apparatus includes a light irradiation unit 40, a mounting unit 44, a slit image forming device 20, an observation display device 30, an automatic focus adjustment device 70, an optical image light receiving unit 62, an optical image storage unit 64 that stores an optical image, and A reference image creation unit 80 for creating a reference image, a reference image storage unit 82 for storing the reference image, a comparison processing unit 156 for comparing the optical image and the reference image, and the like. The light irradiation unit 40, the placement unit 44, the slit image forming device 20, the observation display device 30, the automatic focus adjustment device 70, the optical image light receiving unit 62, and the optical image storage unit 64 constitute an optical image acquisition device. . The optical image acquisition device automatically adjusts the focus of the pattern image irradiated on the optical image light receiving unit 62 by the automatic focus adjustment device 70. Further, the optical image acquisition device forms a slit image on the pattern surface of the sample to be inspected, and displays the slit image on the observation display device 30. Since the slit image can be directly observed by the observation display device 30, the focusing state can be accurately confirmed. Thereby, the optical image acquisition apparatus can easily acquire an optical image of the pattern of the inspection target sample. In the following, an automatic focus adjustment device (autofocus device) 70 will be described as a focus adjustment device, but a focus adjustment device that is manually adjusted may be used.

  The pattern inspection apparatus includes a data processing apparatus together with the optical image acquisition apparatus, and inspects a defect of the pattern drawn on the inspection target sample by comparing the optical image with the reference image. Here, the reference image includes a reference image for DB comparison (die-database comparison) or an optical image for DD comparison (die-die comparison). The data processing apparatus performs the image processing in synchronization with the two-dimensional movement of the placement unit on which the specimen to be examined is placed and the capture of the optical image (capture of the photoelectric detection signal by the optical image light receiving unit 62), thereby performing the inspection process. A two-dimensional optical image of the sample can be obtained. Here, the reference image is stored in a storage device provided inside the data processing device in order to determine the quality of the sample to be inspected, and the optical image and the reference image are compared and inspected by the comparison processing unit 156. As a result, foreign matters such as scratches, defects, dust and the like occurring in the sample to be inspected can be found. Then, the comparison determination result from the comparison processing unit inside the data processing device is displayed on a display device such as a CRT monitor.

(Optical image acquisition device)
FIG. 2 shows an example of an optical image acquisition device. The optical image acquisition device includes a light irradiation unit 40, a mounting unit 44 for mounting a sample to be inspected, an imaging optical system, a slit image forming device 20, an observation display device 30, an optical image light receiving unit 62, and an automatic focus adjustment device. 70 and the like. The imaging optical system forms an image 14 of the pattern 12 of the specimen 10 to be inspected on the optical image light receiving unit 62, and includes a first lens 46 serving as an objective lens, a second lens 48 serving as a tube, and a third lens serving as a collimator. 50, a fourth lens 52 of an imaging lens, and the like. The slit image forming apparatus 20 forms an image 28 of the slit 26 on the pattern forming surface of the specimen 10 to be inspected, and includes an illumination unit 22, a slit substrate 24, a slit 26, a fifth lens 54 such as a reflection tube, and a half. A mirror 58 and the like are provided. The observation display device 30 is displayed for observing the slit image 28, and includes a camera 32, a sixth lens 56, an optical path changing mirror 60, and the like. As the optical path changing mirror 60, a half mirror may be used, or a normal mirror may be arranged and rotated at every observation to change the optical path. The optical image light receiving unit 62 receives the pattern image 14 of the pattern 12 of the sample to be inspected and transmits the optical image to an optical image storage unit 64 such as a buffer memory. The automatic focus adjustment device 70 automatically adjusts the focus of the pattern image 14 irradiated to the optical image light receiving unit 62, and includes a detection slit F74 disposed in the front stage of the optical image light receiving unit 62, and a detection disposed in the rear stage. A slit R76, a fine movement device 72 that moves the placement portion 44, a position adjustment device 78, and the like are provided. The fine movement device 72 finely moves the mounting portion 44 along the optical axis. The position adjusting device 78 adjusts the positions of the optical image light receiving unit 62, the detection slit F74, and the detection slit R76 so that the pattern 12 of the inspection target sample 10 and the pattern of the slit 26 are focused on the optical image light receiving unit 62. adjust. The detection slit F74 and the detection slit R76 are each provided with a light amount detection element that detects the light amount, although not shown.

  Specifically, the optical image acquisition apparatus irradiates the inspection target sample 10 with irradiation light 42 having various shapes such as a spot shape and a rectangular shape from the light irradiation unit 40. The irradiation light 42 is applied to the pattern 12 of the sample 10 to be inspected, and is output as a pattern image 14. The pattern image 14 is irradiated to the optical image light receiving unit 62 through an imaging optical system including lenses 46, 48, 50, and 52. Further, the optical path of the pattern image 14 is changed by the optical path changing mirror 60, and the pattern image 14 is irradiated to the camera 32 through the lens 56.

  Regarding the formation of the slit image 28, the illumination light 23 from the illumination unit 22 is irradiated to the slit substrate 24. The illumination light 23 passes through the slit 26 and becomes a slit image 28. The slit image 28 passes through the fifth lens 54, is reflected by the half mirror 58, passes through the first lens 46, and is projected onto the surface of the pattern 12 of the inspection target sample 10.

  The slit image 28 projected onto the inspection target sample 10 passes through the first lens 46, the second lens 48, and the third lens 50 of the imaging optical system, and the optical path is changed by the optical path changing mirror 60. The changed slit image 28 e passes through the sixth lens 56 and is irradiated to the camera 32. FIG. 3B is an image displayed on the display unit 34 of the camera 32 and shows a pattern image 14 and a slit image 28 of the sample 10 to be inspected. FIG. 3A shows the slit 26 formed in the slit substrate 24. The slits 26 are positioned at the corners so as not to overlap the pattern 12 of the sample 10 to be inspected. By providing the observation display device 30 in this way, the slit image 28 can be easily observed.

  Further, the slit image 28 projected on the specimen 10 to be inspected passes through the imaging optical system, and further passes through the detection slit F74 and the detection slit R76. In each of the detection slit F74 and the detection slit R76, the light quantity of the slit image 28 is measured. The focus is automatically adjusted according to the difference between these light quantities. This automatic focusing mechanism is a confocal method using a slit image. The amount of light at the focus position before and after the optical image light receiving unit 62 of the slit image 28 is defined by the detection slit F74 and the detection slit R76, and is measured by a light amount detection element (not shown). Based on the light quantity balance transmitted through the detection slit F74 and the detection slit R76, the focus position of the optical image light receiving unit 62 is calculated. For example, when the focal position is on the detection slit F74 side, the amount of light detected by the detection slit F74 is greater than the amount of light detected by the detection slit R76. Conversely, when the focal position is on the detection slit R76 side, the amount of light detected by the detection slit F74 is less than the amount of light detected by the detection slit R76. When there is a focus, the amount of light detected by the detection slit F74 and the detection slit R76 is equal. In this way, focusing can be performed automatically or manually. This focus adjustment can be performed by the fine movement device 72. The fine movement device 72 is arranged so that the placement unit 44 can move along the optical axis between the pattern 12 of the specimen 10 to be inspected and the optical image light receiving unit 62. In this focus adjustment, the fine movement device 72 is finely operated while observing the signal characteristics of the detection slit F74 and the detection slit R76, and the optimum position on the optical axis of the pattern 12 of the inspection target sample 10 is calculated. At this time, by directly observing the slit image 28 displayed on the observation display device 30, focusing can be performed easily and with high accuracy. The sharpness of the slit image 28 is observed for focusing. The focus adjustment is determined by measuring the image quality of the optical image light receiving unit 62.

(Overall configuration of pattern inspection equipment)
FIG. 4 shows the overall configuration of the pattern inspection apparatus 100. The pattern inspection apparatus 100 includes an optical image acquisition device 110 and a data processing device 130. The optical image acquisition device 110 and the data processing device 130 do not need to be clearly distinguished, and each component can be shared. The optical image acquisition device 110 includes an autoloader 112, a light source 114, an irradiation optical system 116, a laser measurement system 118, a placement unit 44 such as an XYθ table, a θ motor 120, an X motor 122, a Y motor 124, and an imaging optical system 126. An optical image light receiving device 62 having a photoelectric detection element such as a CCD, TDI, or photodiode array, a sensor circuit 128 having a buffer memory, and the like. The light irradiation unit 40 can be configured by the light source 114 and the irradiation optical system 116.

  The optical image acquired by the optical image light receiving device 62 is stored in the buffer image in the sensor circuit 128, the main storage device 134, the optical image storage unit 64 of a storage device such as the mass storage device 136. The pattern image formed on the optical image light receiving unit 62 is photoelectrically converted by the optical image light receiving unit 62 and further A / D (analog / digital) converted by the sensor circuit 128. In addition, although the acquired optical image uses the transmission image by the transmitted light, it uses the reflected image using the reflected light, or the scattered image, the polarization scattered image, the polarized transmission image, the phase-enhanced image reflected light, etc. Also good.

  The data processing device 130 includes a central processing unit 132, a bus 142, a main storage device 134 connected to the bus 142, a mass storage device 136, a display device 138, a printing device 140, an autoloader control unit 144, and a placement unit 44. A reference unit that receives pattern data of design data from the table control unit 146, the database 148, the database creation unit 150, the development unit 152, and the development unit 152, and receives an optical image from the sensor circuit 128 and creates a reference image. 154, an optical image is received from the sensor circuit 128, a reference image is received from the reference unit 154, a comparison processing unit 156 that compares the optical image and the reference image, and a position signal of the mounting unit 44 from the laser measurement system 118. A position measuring unit 158 for receiving is provided. The pattern inspection apparatus 100 can be configured by an electronic circuit, a program, or a combination thereof.

(Reference image creation part)
The reference image creation unit 82 creates a reference image or an optical image acquired by the optical image acquisition device 110 as a reference image. The reference image creating unit 80 that creates the reference image performs various conversions on the design data of the specimen 10 to be inspected, and creates a reference image that is an image resembling an optical image. Specifically, the reference image standard image creation unit 82 can be configured by a development unit 152 and a reference unit 154 as shown in FIG. The development unit 152 reads design data of the image of the specimen to be inspected from the large-capacity storage device 136 through the central processing unit 132 and converts it into image data. The reference unit 154 receives the image data from the development unit 152, performs processing to resemble the optical image by rounding or slightly blurring the corners of the figure, and creates a reference image. Further, the reference image creating unit 82 that creates an optical image of the reference image stores, for example, a high-precision optical image obtained by the optical image obtaining apparatus 110 in the reference image storage unit 82 so that the comparison process is easy. And a reference image.

(Pattern inspection method)
FIG. 5 shows a flowchart of the pattern inspection method. In the pattern inspection method, the optical image acquired by the optical image acquisition method and the reference image created by the reference image creation unit are compared by the comparison processing unit, and the pattern inspection of the inspection target sample 10 is performed. In the optical image acquisition method, first, the inspection target sample 10 is placed on the placement unit 44 (placement step: S1). Next, the irradiation object 42 is irradiated with the irradiation light 42 by the light irradiation unit 40 (irradiation step: S2). At the same time, in the slit image forming apparatus 20, the illumination unit 22 irradiates the slit substrate 24 with illumination light 23. The illumination light 23 passes through the slit 26 of the slit substrate 24 and is generated as a slit image 28a. The generated slit image 28a passes through the fifth lens 54, is reflected by the half mirror 58, passes through the first lens 46, and is irradiated onto the pattern surface of the specimen 10 to be inspected (slit image forming step: S3). The slit image 28 of the sample 10 to be inspected passes through the imaging optical system and passes through the detection slit F74 and the detection slit R76. The light amount of the slit image 28 is measured by a light amount detection element disposed in the detection slit F74 and the detection slit R76. The automatic focus adjustment device 70 calculates the focal position of the slit image 28 of the optical image light receiving unit 62 based on the light quantity balance transmitted through the detection slit F74 and the detection slit R76. For this purpose, the position of the specimen 10 to be inspected is moved by the fine movement device 72 to perform focusing (focus adjustment step: S4). At the same time, the slit image 28 of the sample to be inspected passes through the imaging optical system, is reflected by the optical path changing mirror 60, passes through the sixth lens 56, enters the camera 32, and is displayed on the display unit 34 of the camera. (Slit image display step: S5). If the slit image 28 is not in focus, the process returns to the focus adjustment step (S4), and the focus is adjusted while looking at the characteristics of the light quantity signals of the detection slit F74 and the detection slit R76. When focused, the pattern image 14 of the specimen 10 to be inspected input to the optical image light receiving unit 62 is acquired as an optical image (optical image acquisition step: S6). The acquired optical image is input to the optical image storage unit 64 (optical image storage step: S7). The pattern inspection method creates a reference image (reference image creation step: S8). The reference image is input to the reference image storage device (reference image storage step: S9). The optical image and the reference image are compared, and an appropriate pattern inspection is performed (comparison processing step: S10).

10. Sample 14 to be inspected. Pattern image 20. Slit image forming device 24. Slit substrate 28. Slit image 30. Display device 32 for observation. Camera 40. Light irradiation unit 60. Optical path. Change mirror 62... Optical image light receiving unit 64... Optical image storage device 70... Automatic focus adjustment device 72... Fine movement device 100. 126, imaging optical system 128, sensor circuit 130, data processing device 134, main storage device 136, large-capacity storage device 142, bus 146, table control unit 152, expansion unit 154, reference unit 156, position measurement unit

Claims (6)

In an optical image acquisition device that acquires an optical image of a pattern of a sample to be inspected,
A placement unit for placing a sample to be inspected;
A light irradiation unit for irradiating the sample to be inspected placed on the placement unit with irradiation light;
An optical image receiver for receiving the irradiation light irradiated on the specimen to be inspected;
A focus adjustment device that focuses the pattern image of the sample to be inspected on the optical image light receiving unit;
A slit image forming apparatus for forming a slit image on a sample to be inspected;
An observation display device that displays a slit image on the specimen to be inspected,
An optical image acquisition device that adjusts the focus of a pattern image of a sample to be inspected in an optical image light receiving unit from a slit image on the sample to be inspected displayed on an observation display device. The optical image acquisition device according to claim 1.
The slit image forming apparatus has an illumination unit, a slit and a half mirror,
An optical image acquisition apparatus in which a half mirror is disposed in an optical path between a sample to be inspected and an optical image light receiving unit, and a surface of the sample to be inspected is irradiated with a slit image emitted from a slit. The optical image acquisition device according to claim 1.
Arranged in the optical path between the sample to be inspected and the optical image light receiving unit, equipped with an optical path changing mirror for changing the optical path,
The observation display device receives the slit image whose optical path has been changed by the optical path changing mirror, and displays the slit image formed on the specimen to be inspected. In a pattern inspection device that inspects the pattern of a sample to be inspected,
A placement unit for placing a sample to be inspected;
A light irradiation unit for irradiating the sample to be inspected placed on the placement unit with irradiation light;
An optical image receiver for receiving the irradiation light irradiated on the specimen to be inspected;
A focus adjustment device that focuses the pattern image of the sample to be inspected on the optical image light receiving unit;
A slit image forming apparatus for forming a slit image on a sample to be inspected;
An observation display device for displaying a slit image on the specimen to be inspected;
An optical image storage unit for storing optical images;
A reference image storage unit for storing a reference image;
A comparison processing unit that compares the optical image and the reference image,
A pattern inspection apparatus that adjusts a focus of a pattern image of a sample to be inspected in an optical image light receiving unit from a slit image on the sample to be inspected displayed on an observation display device. In an optical image acquisition method for acquiring an optical image of a pattern of a sample to be inspected,
A slit image forming step for forming a slit image on the specimen to be inspected;
An optical image acquisition step of irradiating the sample to be inspected with irradiation light, and forming a pattern of the sample to be inspected in the optical image receiving unit;
A slit image display step for displaying a slit image on the specimen to be inspected;
A focus adjustment step of displaying a slit image and adjusting the focus of the pattern image of the sample to be inspected, and an optical image acquisition method. In a pattern inspection method for inspecting a pattern of a sample to be inspected,
A slit image forming step for forming a slit image on the specimen to be inspected;
An optical image acquisition step of irradiating the sample to be inspected with irradiation light, and forming a pattern of the sample to be inspected in the optical image receiving unit;
A slit image display step for displaying a slit image on the specimen to be inspected;
A focus adjustment step for displaying the slit image and adjusting the focus of the pattern image of the sample to be inspected;
A pattern inspection method comprising: a comparison processing step for comparing an optical image with a reference image.

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