JP2010225825A - Position detecting method and charged-particle beam lithography method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detecting method capable of accurately detecting an edge position of a sample even if blue light or red light is used for illumination by employing a color CCD camera including a plurality of light receiving elements on which color filters of Bayer arrangement are disposed, and a charged-particle beam lithography method. <P>SOLUTION: The color CCD camera is positioned so that the array direction of the light receiving elements of the color CCD camera is diagonal to one side of a mask which is subjected to edge position detection. An image of a region including a mask edge and its vicinity is photographed by using the color CCD camera with a region including the mask edge illuminated with blue light. Blue gray-scale values at a plurality of points in the image are determined, and then a plurality of coordinates corresponding to the mask edge are determined on the basis of variations of the gray-scale values. A regression line Lr determined on the basis of the plurality of coordinates is regarded as the edge position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a position detection method and a charged particle beam writing method.

  Along with the high integration of semiconductor devices, the circuit pattern of the semiconductor device is miniaturized. In order to form a fine circuit pattern in a semiconductor device, a highly accurate original pattern (that is, a reticle or mask) is required. In order to produce an original pattern, an electron beam drawing apparatus having excellent resolution is used.

  This type of electron beam drawing apparatus includes a transport robot, and mask blanks (hereinafter referred to as “mask”) as a sample are transported and placed on the stage by the transport robot. If the mounting position of the mask on the stage is shifted from the normal position, the position of the pattern drawn on the mask is shifted. Therefore, the mask is aligned before and / or after the mask is transferred onto the stage. In order to perform alignment, it is necessary to detect the position of the mask in advance, but the alignment mark is not formed on the mask before drawing. For this reason, the edge position of the mask is detected, and alignment is performed based on the detected edge position. For example, Japanese Patent Laying-Open No. 2008-210951 (Patent Document 1) discloses a method of capturing an image of a sample with a CCD camera and detecting the edge position of the sample from the captured image.

  Here, there is a case where an appearance inspection is performed to detect the edge position of the mask and to detect foreign matters and scratches existing on the mask surface. In this case, since it is necessary to detect the shading of the mask surface, a color imaging device such as a color CCD camera is used. As a color filter provided on a light receiving element of a color CCD camera, a Bayer array filter that is relatively inexpensive and can be easily realized is often used. In the Bayer array, four light receiving elements (2 elements in the X direction × 2 elements in the Y direction) surrounded by a one-dot chain line in FIG. 6A are used as a basic array (1 pixel), and this basic array is repeatedly arranged. . As shown in FIG. 6B, a green (G) filter 61 is provided on two diagonal light receiving elements (hereinafter also referred to as “elements”) 51 in this basic array, and one of the remaining two elements. A blue (B) filter 62 is disposed on each element 52. Further, although not shown, a red (R) filter is disposed on the remaining one element of the basic array. These light receiving elements are formed on the substrate 50, and lenses (not shown) are arranged on the filters of the respective colors. According to such an arrangement, the element 51 in which the green filter 61 is disposed and the element 52 in which the blue filter 62 is disposed are alternately repeated in one line L1, and the red filter is disposed in the other line L2. The element and the element 51 in which the green filter 61 is arranged are repeated alternately.

  By the way, when using a color CCD camera, it is conceivable to use blue light having a short wavelength as illumination light in order to acquire a high-resolution image. When illuminating blue light, the light received by the light receiving elements in which the green and red filters are disposed other than the light receiving element in which the blue filter is disposed (hereinafter also referred to as “B element”) is cut off. In general, as shown in FIG. 7, the color CCD camera 30 is arranged so that the light receiving element arrangement direction 30 a of the color CCD camera 30 is parallel to one side Mb that is an edge position detection target of the mask M. . When the color CCD camera 30 is arranged in this way and the mask M is illuminated with blue light, the edge position information of the mask M can be obtained only in a cycle of two elements. In FIG. 6, when the mask M is moved from bottom to top, information is obtained from the B element when one side, which is the edge portion of the mask M, is at the position of Mb1 and Mb3, but when that side is at the position of Mb2. Cannot obtain information on the B element. That is, as long as one side Mb of the mask M does not reach the B element, the information of the B element is interpolated, and the image captured by the color CCD camera 30 does not change, so the detected edge position does not change. As a result, there is a problem that an error occurs between the edge position of the mask M obtained from the information of the B element and the actual edge position.

  As described above, when the color CCD camera 30 in which the color filters of the Bayer array are arranged and the edge position of the mask M is detected by illuminating blue light, the light receiving element array direction 30a of the color CCD camera 30 and the mask If the color CCD camera 30 is arranged so that one side Mb that is an M edge detection target is parallel, the detection accuracy of the edge position of the mask M due to the sampling period of the element (B element) in which the blue filter is arranged There was a problem that decreased.

JP 2008-210951 A

  In view of the above problems, an object of the present invention is to accurately detect the edge position of a sample even when illuminating blue light or red light using a color CCD camera in which a Bayer array color filter is arranged. It is an object of the present invention to provide a position detection method and a charged particle beam writing method capable of performing the above.

  In order to solve the above-mentioned problem, a first aspect of the present invention is to provide a color CCD camera including a plurality of light receiving elements in which a red filter, a blue filter, and a green filter are arranged according to a Bayer array. A position detection method for picking up an image and detecting the position of an edge portion from the image. In the state where the camera is arranged and the region including the edge portion is illuminated with blue light or red light, an image in the vicinity of the edge portion is captured by the color CCD camera, and a plurality of coordinates corresponding to the edge portion in this image are obtained, A regression line is obtained from the plurality of coordinates, and the regression line is used as the position of the edge portion.

  In this first aspect, it is preferable to arrange the color CCD camera so that the angle formed by the light receiving element arrangement direction and one side of the sample is 45 degrees.

  In the first aspect, when blue light is illuminated, it is preferable to obtain blue shade values at a plurality of points in the image and obtain a plurality of coordinates corresponding to the edge portion from the change rate of the shade values.

  In this first aspect, when red light is illuminated, it is preferable to obtain red shade values at a plurality of points in the image and obtain a plurality of coordinates corresponding to the edge portion from the change rate of the shade values.

  In the second aspect of the present invention, the position of the edge portion of the sample is detected using the position detection method of the first aspect, the sample is aligned based on the detected position, and then charged particles are applied to the sample. It is characterized by irradiating a beam.

  According to the present invention, the edge position of the sample can be obtained with high accuracy even when a color CCD camera having a Bayer array color filter is used to illuminate blue light or red light.

In this Embodiment, it is the schematic which shows the structure of an electron beam drawing apparatus. It is the schematic which shows the structure of the position detection apparatus applied to an electron beam drawing apparatus. In this Embodiment, it is a figure which shows the positional relationship of a color CCD camera and a mask. In this Embodiment, it is a figure which shows the sampling period of the light receiving element by which the blue filter is arrange | positioned. In this Embodiment, it is a figure which shows the several coordinate corresponding to the mask edge part in the image imaged with the color CCD camera, and the regression line calculated | required from several coordinate. (A) is a figure which shows the Bayer arrangement | sequence of the color filter of a color CCD camera, (b) is A'-A 'sectional drawing of (a). It is a figure which shows the positional relationship of the conventional color CCD camera and a mask.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic diagram showing a configuration of an electron beam drawing apparatus which is an example of a charged particle beam drawing apparatus in the present embodiment. The electron beam drawing apparatus draws a predetermined pattern by irradiating a mask M as a sample with an electron beam. The electron beam drawing apparatus includes a drawing chamber 1 that draws a pattern on a mask M, a robot chamber 2 that is located adjacent to the drawing chamber 1 and has a built-in transfer robot R, and a robot chamber 2 opposite to the drawing chamber 1. A load lock chamber 5 disposed at a position adjacent to the robot chamber 2 and a mask loading device 7 disposed at a position adjacent to the load lock chamber 5 on the opposite side to the robot chamber 2 are provided. Gate valves 3, 6, and 8 are provided between the robot chamber 2, the drawing chamber 1, and the load lock chamber 5, and between the load lock chamber 5 and the mask loading device 7, respectively. Further, an alignment chamber 4 for positioning the mask M is disposed around the drawing chamber 1 and the load lock chamber 5 of the robot chamber 2 that are not adjacent to each other.

  The mask M is loaded into the load lock chamber 5 from the mask loading device 7 by a robot (not shown). Then, after closing the gate valve 8 and evacuating the load lock chamber 5, the gate valve 6 is opened, and the mask M is transferred from the load lock chamber 5 to the alignment chamber 4 by the transfer robot R. When alignment (positioning) is performed in the alignment chamber 4, the gate valve 3 is opened, and the mask M is transferred onto the stage St in the drawing chamber 1 by the transfer robot R. In the drawing chamber 1, after alignment, a predetermined pattern is drawn on the mask M by irradiating the mask M placed on the stage St with an electron beam.

  By the way, when the alignment is performed in the alignment chamber 4 and the drawing chamber 1, the edge position of the mask M is detected. Hereinafter, detection of the edge position of the mask M will be described.

  FIG. 2 is a schematic diagram showing a configuration of a position detection apparatus applied to the electron beam drawing apparatus. The position detection device 10 is disposed in the drawing chamber 1 and the alignment chamber 4. As shown in FIG. 2, the position detection device 10 includes an illumination device 11, a color CCD camera 13, an illumination controller 15, a camera controller 16, and a control device (arithmetic processing unit) 20.

  The illumination device 11 is disposed above the mask M and irradiates light in a direction perpendicular to the front surface (upper surface) or the rear surface (lower surface) of the mask M. For example, a blue LED that emits blue light is used as the illumination device 11. The illumination device 11 has an illumination range 12 that sufficiently illuminates the edge portion (one side Ma) of the mask M. The illumination range 12 is, for example, 60 mm × 60 mm.

  The color CCD camera 13 is disposed below the mask M and captures an image in a state where the illumination device 11 emits blue light. The color CCD camera 13 has a plurality of light receiving elements in which color filters with a Bayer arrangement as shown in FIGS. 6A and 6B are arranged. Here, the distance (imaging distance) d1 from the color CCD camera 13 to the back surface of the mask M is, for example, about 160 mm. This imaging distance d1 is determined from the relationship between the focal length determined by the combination of the color CCD camera 13 and the lens, the required imaging range (field size) 14, and the detection resolution per element of the color CCD camera 13. The imaging range 14 of the color CCD camera 13 is 40 mm × 40 mm, for example.

  In FIG. 2, the illumination device 11 and the color CCD camera 13 are arranged with the mask M interposed therebetween, but the illumination device 11 and the color CCD camera 13 are arranged on the same side (front side) with respect to the mask M. May be.

  FIG. 3 is a diagram showing the positional relationship between the color CCD camera 13 and the mask M. As shown in FIG. In the present embodiment, the color CCD camera 13 is arranged so that the light receiving element arrangement direction 13a of the color CCD camera 13 is inclined with respect to one side (edge portion) Ma that is an edge position detection target of the mask M. Although details will be described later, the angle θ formed by the light receiving element arrangement direction 13a and the one side Ma is preferably 45 degrees.

  The illumination controller 15 controls the illumination device 11. Specifically, based on a command from the control device 20, an instruction to turn on and off the illumination device 11 in accordance with the imaging timing of the color CCD camera 13, an instruction to change or adjust the illumination light amount of the illumination device 11, and the like. Do.

  The camera controller 16 controls the color CCD camera 13. Specifically, an imaging time (shutter time), an imaging instruction, and the like are performed based on a command from the control device 20. When the color CCD camera 13 is equipped with an autofocus mechanism, focus adjustment is also performed.

  The control device 20 controls the illumination controller 15 and the camera controller 16 and detects and stores the edge position of the mask M from the image captured by the color CCD camera 13. The control device 20 includes a controller control unit 21, a position detection unit 22, and a position storage unit 23.

  The controller control unit 21 controls the illumination controller 15 and the camera controller 16. The position detection unit 22 detects the edge position of the mask M from the image captured by the color CCD camera 13 according to a position detection method described later. The position storage unit 23 is a storage medium (for example, a memory or a magnetic disk) that stores the edge position detected by the position detection unit 22.

  Next, a position detection method by the position detection device 10 will be described.

  First, the mask M is disposed between the illumination device 11 of the position detection device 10 and the color CCD camera 13. Next, blue light is irradiated from above the mask M to the vicinity of the edge portion Ma on the surface of the mask M. Specifically, the lighting controller 15 that has received a lighting instruction from the control device 20 turns on the lighting device 11.

  The color CCD camera 13 captures an image in the vicinity of the edge portion Ma of the mask M in a state where the illumination device 11 emits blue light. Specifically, the camera controller 16 that has received an imaging instruction from the control device 20 performs imaging with the color CCD camera 13.

  Here, in the present embodiment, the color CCD camera 13 is arranged so that the light receiving element arrangement direction 13a of the color CCD camera 13 is inclined with respect to one side Ma of the mask M. By arranging the color CCD camera 13 in this way, the sampling period Pa of the edge position Ma of the mask M can be shortened as shown in FIG. FIG. 4 is a diagram showing the sampling period Pa of the edge position Ma by the element (B element) 52 in which the blue filter is arranged. For comparison, FIG. 4 shows a conventional edge when the color CCD camera 30 is arranged so that the light receiving element arrangement direction 30a of the color CCD camera 30 is parallel to one side Mb of the mask M as shown in FIG. The sampling period Pb of the position Mb is also shown. The color CCD camera 13 is arranged obliquely so that the angle θ (see FIG. 3) formed by the light receiving element arrangement direction 13a and one side Ma is 45 degrees, so that the sampling cycle Pa of the edge position Ma is set to the conventional sampling cycle Pb. (√2) / 2 times as large as. When θ = 45 degrees, the sampling period Pa is the shortest.

  An image captured by the color CCD camera 13 is sent to the position detection unit 22 of the control device 20 via the camera controller 16. The position detection unit 22 obtains blue gray values at a plurality of points in the image, and sets a point at which the change rate of the obtained gray value is equal to or greater than a predetermined value as a detection point of the edge part. In FIG. 5, ◇ indicates a plurality of detection points corresponding to the edge portion of the mask M. In the present embodiment, since blue light is illuminated, the plurality of detection points are determined by the amount of light received by the light receiving element (52) in which the blue filter (62) is arranged. Here, a periodic error E occurs in the coordinates of the detection point corresponding to the edge portion of the mask M. This periodic error E is caused by a sampling period (Pa (see FIG. 4)) that depends on the Bayer array of the color filter, and the position detection unit 22 determines from the X and Y coordinates of the plurality of detection points. A regression line Lr is obtained using a known method, and the obtained regression line Lr is detected as an edge position of the mask M. By obtaining the regression line Lr in this way, that is, the X coordinates and Y of the plurality of detection points are obtained. By averaging the directions, the periodic error E is reduced, so that the edge value of the mask M can be obtained with high accuracy.The edge position of the mask M obtained by the position detection unit 22 is the position. It is stored in the storage unit 23.

  As described above, in the present embodiment, the color CCD camera 13 is arranged so that the light receiving element arrangement direction 13a of the color CCD camera 13 is inclined with respect to the one side Ma of the mask M, and the region including the one side Ma is arranged. In the state of illuminating the blue light, an image in the vicinity of one side Ma is picked up by the color CCD camera 13, the coordinates of a plurality of detection points corresponding to one side Ma in this image are obtained, and the regression line Lr is obtained from the coordinates of the plurality of detection points. And the regression line Lr is obtained as the edge position. By arranging the color CCD camera 13 obliquely with respect to one side Ma of the mask M, as compared with the case where both are arranged in parallel as shown in FIG. 7, the sampling period Pa by the light receiving element 52 in which the blue filter is arranged. Therefore, the periodic error E of the coordinates of a plurality of detection points corresponding to the edge portion in the captured image can be reduced. Further, the periodic error E can be reduced by obtaining the regression line Lr from the coordinates of the plurality of detection points. Therefore, the edge position of the mask M can be detected with high accuracy even when a blue or red light is illuminated using a color CCD camera in which a Bayer array color filter is arranged.

  Furthermore, after performing alignment based on the edge position detected with high accuracy in this way, the charged particle beam drawing is performed, whereby the drawing accuracy can be improved.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, although the electron beam is used in the above embodiment, the present invention is not limited to this, and the present invention can also be applied to cases where other charged particle beams such as an ion beam are used.

  In the above embodiment, the case where the mask M is illuminated with blue light has been described, but the present invention can also be applied to the case where red light is illuminated. In this case, the sampling period by the light receiving element in which the red filter is arranged is shortened. In addition, the coordinates of a plurality of detection points corresponding to the edge portion of the mask M in the image captured by the color CCD camera 13 are determined by the amount of light received by the light receiving element in which the red filter is arranged. Therefore, the same effect as the above embodiment can be obtained.

  Moreover, in the said embodiment, although the position detection apparatus 10 is applied to the electron beam drawing apparatus, it is applicable to various apparatuses other than an electron beam drawing apparatus.

M mask (sample)
R transfer robot 1 drawing room 2 robot room 4 alignment room 5 load lock room 7 mask insertion device 10 position detection device 11 illumination device 13 color CCD camera 13
DESCRIPTION OF SYMBOLS 15 Lighting controller 16 Camera controller 20 Control apparatus 21 Controller control part 22 Position detection part 23 Position preservation | save part

Claims (5)

An image in the vicinity of the edge portion of the sample is picked up using a color CCD camera having a plurality of light receiving elements in which a red filter, a blue filter, and a green filter are arranged according to the Bayer array, and the position of the edge portion is detected from the image. A position detection method,
The color CCD camera is arranged so that the light receiving element arrangement direction of the color CCD camera is inclined with respect to one side which is an edge position detection target of the sample, and the region including the edge portion is illuminated with blue light or red light. In this state, an image in the vicinity of the edge portion is captured by the color CCD camera, a plurality of coordinates corresponding to the edge portion in the image are obtained, a regression line is obtained from the plurality of coordinates, and the regression line is obtained as the edge. A position detection method characterized in that the position is a position of a part.   2. The position detection method according to claim 1, wherein the color CCD camera is arranged so that an angle formed by the light receiving element arrangement direction and one side of the sample is 45 degrees.   The blue or gray value at a plurality of points in the image is obtained when the blue light is illuminated, and a plurality of coordinates corresponding to the edge portion is obtained from a change rate of the gray value. Item 3. The position detection method according to Item 2.   The red or gray value at a plurality of points in the image is obtained when the red light is illuminated, and a plurality of coordinates corresponding to the edge portion are obtained from a change rate of the gray value. Item 3. The position detection method according to Item 2. The position detection method according to any one of claims 1 to 4, wherein the position of the edge portion of the sample is detected, alignment of the sample is executed based on the detected position, and then the sample is applied to the sample. A charged particle beam drawing method comprising irradiating a charged particle beam.

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