JP5953038B2 - Apparatus and method for measuring focal length of microlens array - Google Patents

Description

  The present invention relates to an apparatus and method for measuring the focal length of a microlens array used in an exposure apparatus.

  Recently, an exposure apparatus that projects a mask pattern onto a substrate by a microlens array has been used (Patent Document 1). FIG. 9 is a schematic view showing an exposure apparatus using a microlens array. A mask 3 on which a pattern to be exposed on the substrate 1 is formed is disposed above the substrate 1 to be exposed with an appropriate length from the substrate 1. A microlens array 2 in which microlenses 2a are two-dimensionally arranged is disposed between the substrate 1 and the mask 3, and exposure light is irradiated onto the mask 3 from above the mask 3, and the mask 3 is projected onto the substrate 1 by the microlens array 2, and the pattern formed on the mask 3 is transferred to a resist or the like on the substrate surface as an erecting equal-magnification image by the microlens array 2. .

  FIG. 6 is a view showing a microlens array 2 used in the exposure apparatus, FIG. 7A is a schematic view showing a hexagonal field stop 12, and FIG. 7B is a schematic view showing a circular stop 11. As shown in FIG. 6, the microlens array 2 has, for example, a four-lens eight-lens configuration, and a structure in which four unit microlens arrays 2-1, 2-2, 2-3, 2-4 are stacked. Have The microlenses of each of the unit microlens arrays 2-1 to 2-4 are composed of an optical system expressed by two convex lenses. As a result, the exposure light once converges between the unit microlens array 2-2 and the unit microlens array 2-3, and further forms an image on the substrate below the unit microlens array 2-4. That is, an inverted equal magnification image of the mask 3 is formed between the unit micro lens array 2-2 and the unit micro lens array 2-3, and an erect equal magnification image of the mask 3 is formed on the substrate. Image. A polygonal field stop (for example, a hexagonal field stop 12) is disposed between the unit microlens array 2-2 and the unit microlens array 2-3, and the unit microlens array 2-3 and the unit microlens array 2- A circular diaphragm 11 is arranged between the four. The circular diaphragm 11 defines the NA (numerical aperture) of each microlens, and the hexagonal field diaphragm 12 narrows the field to a hexagonal shape near the imaging position. The hexagonal field stop 12 and the circular stop 11 are provided for each microlens. For each microlens, the light transmission area of the microlens is shaped into a circle by the circular stop 11 and exposure light is exposed on the substrate. The region is shaped into a hexagon by a hexagonal field stop 12. For example, as shown in FIG. 7, the hexagonal field stop 12 is formed as a hexagonal opening in the lens opening 10 of the microlens. Therefore, assuming that the scanning of the exposure light transmitted through the microlens array 2 by the hexagonal field stop 12 is stopped, one microlens surrounds the hexagonal shape shown in FIG. Irradiate only the affected area.

In the exposure apparatus using this microlens array, the substrate 1 and the mask 3 are fixed, and the microlens array 2 and the light source (not shown) move in the scanning direction S in synchronization with each other. The pattern of the mask 3 is scanned and exposed to, for example, a resist film on the surface of the substrate 1, or the microlens array 2 and the light source are fixed, and the substrate 1 and the mask 3 move in the scanning direction S in synchronization with each other. By doing so, the pattern of the mask 3 is scan-exposed on the resist film on the surface of the substrate 1.

  At this time, on the surface of the substrate 1, exposure light is instantaneously applied to the hexagonal portion of the hexagonal field stop 12 of each microlens as shown in FIG. As shown in FIG. 8, the microlenses are arranged side by side in a direction perpendicular to the scan direction S, and the microlens rows adjacent to the scan direction S are related to the microlens rows arranged in the direction perpendicular to the scan direction S. Are slightly shifted in the direction perpendicular to the scanning direction S. That is, the hexagonal field stop 12 of the microlens has a hexagonal shape, and is composed of a left triangle portion 12b, an intermediate rectangle portion 12a, and a right triangle portion 12c with respect to a direction perpendicular to the scanning direction S. ing. A plurality of microlens rows are arranged in the scan direction S so that the triangle portion 12b on the left side of the microlens row and the triangle portion 12c on the right side of the microlens row adjacent to the scan direction S overlap in the scan direction S. Has been. Therefore, the microlenses 2a are arranged on a straight line in the direction perpendicular to the scanning direction S and are slightly shifted in the scanning direction S. These microlens rows are arranged so as to form one group of three rows in the scanning direction S, and the fourth microlens row is arranged at the same position as the first microlens row. ing. That is, the first and fourth microlens rows have the same position in the direction perpendicular to the scanning direction S of the microlens 2a.

  When the microlens array 2 and the light source, the substrate 1 and the mask 3 move relative to each other in the scanning direction S, first, on the substrate 1, the microarrays in the first row are related to the direction perpendicular to the scanning direction S. The region that receives the right triangular portion 12c of the hexagonal field stop of the lens row is then passed through the left triangular portion 12b of the hexagonal field stop of the second microlens row, and the third microlens row. Then there is no passage through the opening. On the other hand, the area that receives the rectangular portion 12a of the hexagonal field stop of the first microlens array does not pass through the opening in the second and third microlens arrays. Further, the region that receives the left triangular portion 12b of the hexagonal field stop of the first microlens row does not pass through the opening in the second microlens row, and then the third microlens. Passes through the right triangle portion 12c of the hexagonal field stop of the row. In this way, during scanning, the area on the substrate 1 is subjected to the passage of the two triangular portions 12b and 12c of the hexagonal field stop 12 each time three micro lens rows pass or one The rectangular portion 12a is passed through. Since the opening areas of the triangular portions 12b and 12c are ½ of the opening area of the rectangular portion 12a, the light is exposed with a uniform amount of light in the scanning direction S every time three microlens rows pass. In the fourth microlens array, since the microlenses are arranged at the same position as the first microlens array in the direction perpendicular to the scanning direction S, the third microlens array is the same as the third array in one group. The exposure is repeated. Accordingly, as the microlens array 2, 3n (n is a natural number) microlens rows are provided in the scanning direction S, and the substrate 1 is scanned over the entire scan region by scanning the 3n microlens rows. , Receive uniform exposure with uniform light quantity. As a result, the microlens array 2 and the light source move relative to the substrate 1 and the mask 3 in the scanning direction S, so that the pattern formed on the mask 3 is exposed on the substrate 1. In this way, an erecting equal-magnification image of the mask pattern of the mask 3 is transferred to the substrate 1 by the microlens array 2.

JP 2010-79292 A

  When the microlens array configured as described above is used for high-definition exposure, it is necessary to grasp the focal length with high accuracy. The focal length of the manufactured microlens array may slightly deviate from the design value due to an error in the gap between the unit microlens arrays at the time of manufacturing the microlens array. Therefore, it is preferable to determine the focus state based on the contrast of the real image when the mask pattern is formed using the manufactured microlens array.

  As shown in FIG. 5, in the focus inspection, the illumination light is irradiated from the transmitted illumination light source 22 toward the upper mask 30, and an image of the mask pattern formed on the upper surface 30 a of the mask 30 is displayed on the CCD camera by the micro lens array 2. 20 is incident. Then, the camera 20 observes the image of the mask pattern of the mask 30 and determines the focus state of the microlens array 2 by looking at the contrast of this real image.

  However, although the focus state of the microlens array 2 in the mask 30 can be detected conventionally, the focal position 32 between the camera 20 and the microlens array 2 is unknown, and the focal length f of the microlens array 2 itself. Could not be measured.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a microlens array focal length measurement apparatus and method capable of measuring the focal length of a microlens array.

The microlens array focal length measurement apparatus according to the present invention is a microlens formed by laminating a plurality of unit microlens arrays each having a plurality of microlenses arranged two-dimensionally in the thickness direction. In the array focal length measurement device,
A camera that detects the image;
A focusing screen whose position relative to the camera is fixed such that the focal position of the camera and the focusing screen pattern surface of the lower surface coincide with each other with respect to the optical axis of the camera;
A light source that emits transmitted illumination light toward the camera;
A mask disposed between the light source and the focusing screen and provided with a mask pattern surface on the upper surface;
A laser displacement meter for measuring a distance between the focusing screen pattern surface of the focusing screen and the mask pattern surface of the mask;
Have
A microlens array is disposed between the focusing screen and the mask, and the mask pattern image incident on the camera via the microlens array is focused on the detection surface of the camera. The position of the mask with respect to the optical axis is adjusted, and the laser displacement meter measures a distance between the focusing screen pattern surface and the mask pattern surface.

In addition, the method for measuring the focal length of a microlens array according to the present invention is configured by laminating a plurality of unit microlens arrays in which the plurality of microlenses are two-dimensionally arranged in the thickness direction. In the method for measuring the focal length of a microlens array,
A step of placing a focusing screen on an optical axis of a camera for detecting an image, and fixing the camera and the focusing screen by aligning a focal position of the camera with a focusing screen pattern surface on a lower surface of the focusing screen; When,
On the optical axis of the camera, in order from the focusing screen, a microlens array, a mask, and a transmitted illumination light source are disposed, and the transmitted illumination light is irradiated from the transmitted illumination light source toward the camera;
The mask pattern formed on the mask pattern surface on the upper surface of the mask is detected by the camera, and the position of the mask with respect to the optical axis of the camera is adjusted so that the mask pattern is in focus on the detection surface of the camera. Adjusting, and
Measuring the distance between the focusing screen pattern surface and the mask pattern surface with a laser displacement meter after the camera detects a focused image of the mask pattern;
It is characterized by having.

  In the present invention, the transmitted illumination light causes the mask pattern image of the mask to enter the camera via the microlens array, but the focal position on the optical axis of the camera coincides with the focusing screen pattern surface of the focusing screen. Therefore, when the camera confirms that the detection image of the focusing screen pattern and the detection image of the mask pattern are in focus, the focal position of the microlens array is the focusing screen pattern surface on the camera side, and the mask side Since it is a mask pattern surface, if the distance between this focusing screen pattern surface and the mask pattern surface is measured with a measuring member or the like, it becomes the distance between the focal points of the microlens array, and the microlens is highly accurate. The interfocal distance of the array can be measured.

It is a schematic diagram which shows the focal distance measuring apparatus of the micro lens array which concerns on embodiment of this invention. It is a figure which similarly shows the operation | movement. It is a figure which similarly shows the next process of the operation | movement. It is a figure which similarly shows the next process of the operation | movement. It is a figure which shows the state which focuses with a micro lens array. It is sectional drawing which shows the unit micro lens array which comprises a micro lens array. It is a top view which shows a hexagonal field stop and a circular stop. It is a schematic diagram which shows arrangement | positioning of a micro lens. It is a schematic diagram which shows the exposure apparatus which uses a micro lens array.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 shows a focal length measuring apparatus for a microlens array according to an embodiment of the present invention. The microlens array 2 of the present embodiment has a structure shown in FIGS. 6 to 8 and forms an exposure pattern of a mask as an erecting equal-magnification image on a substrate. The microlens array 2 is installed in the focal length measuring device of the present invention after manufacturing.

In this focal length measuring device, a transmission illumination light source 22 is disposed below with its light irradiation direction facing upward, and a CCD camera 20 is disposed above with its light detection direction facing downward. The optical axis of the camera 20 and the optical axis of the transmitted illumination light source 22 are coincident and both face the vertical direction. A focusing screen 31 is disposed below the camera 20 with its surface horizontal, and the focusing screen 31 and the camera 20 are integrally fixed to each other by a holder 21. . The holder 21 holds both the focus plate 31 and the camera 20 so that the distance between them can be adjusted. After the distance adjustment, the holder 21 and the camera 20 can be fixed. The camera 20 and the focusing screen 31 fixed by the holder 21 are driven in the vertical direction by an appropriate driving device (not shown), and the camera 20 and the focusing screen 31 are moved up and down by the driving device. Can be adjusted. The lower surface of the focusing screen 31 is a focusing screen pattern surface 31a on which a focusing screen pattern is formed.

  A mask 30 is installed above the transmitted illumination light source 22 with its surface horizontal. The upper surface of the mask 30 is a mask pattern surface 30a on which a mask pattern is formed. A microlens array 2 whose focal length is to be measured is disposed between the mask 30 and the focusing screen 31. In addition, a pair of laser displacement meters 23 and 24 having a laser beam path on the side of the microlens array 2 are installed below the mask 30. The laser displacement meters 23 and 24 allow the mask pattern surface 30a and the focusing screen to be located. The distance to the pattern surface 31a can be measured.

  Next, the operation of the focal length measuring apparatus configured as described above will be described. First, as shown in FIG. 2A, the focusing screen 31 is held by the holder 21, and the holder 21 is supported so as to be movable up and down with respect to the camera 20. As shown in FIG. 2B, two focusing screen patterns 40 are formed on the focusing screen pattern surface 31a on the lower surface of the focusing screen 31, and the focusing screen pattern 40 is photographed by the camera 20. The holder 21 is fixed to the camera 20 in a state where the contrast of the image of the focusing screen pattern 40 can be clearly seen by the camera 20 by moving the holder 21 in the vertical direction relative to the camera 20. Thereby, the focal position of the transmitted illumination light on the camera side incident on the camera 20 coincides with the focusing screen pattern surface 31a, and the focusing screen pattern becomes a focal point. It should be noted that the camera 20 and the focusing screen 31 only need to move relatively up and down, and it goes without saying that either of them may be moved.

Next, as shown in FIG. 3A, the mask 30 is irradiated with illumination light from the transmission illumination light source 22, and an image of the mask pattern provided on the mask pattern surface 30a is passed through the microlens array 2 to the focusing screen. An image is formed on 31 focusing screen pattern surfaces. At this time, the mask pattern 41 shown in FIG. 3B is formed on the mask pattern surface 30a, and the camera 20 is positioned at the center of the pair of focusing screen patterns 40 as shown in FIG. 3B. An image in which the mask pattern 41 exists is observed. Since the camera 20, the holder 21, and the focusing screen 31 are fixed integrally, the camera 20 and the focusing screen 31 are moved up and down integrally to form an image of the mask pattern 41 on the mask pattern surface 30a. , by the microlens array 2, so as to form an image at the focusing screen pattern surface 31a of the focusing plate 31, adjusts the position of the camera 20 and the focusing plate 31. As a result, the patterns 40 and 41 shown in FIG. 3B are all in focus, and the in-focus position of the camera 20 is on the focusing screen pattern surface 31a on which the pattern 40 is provided on the optical axis of the camera 20. Similarly, an image of the pattern 41 formed by forming the pattern 41 with the microlens array 2 becomes a focal point on the focusing screen pattern surface 31a, and the two are in focus.

  Therefore, as shown in FIG. 4, when the distance between the mask pattern surface 30a and the focusing screen pattern surface 31a is measured by the laser displacement meters 23 and 24, the focal length f of the microlens array 2 is obtained. Thus, according to the present embodiment, the focal length f of the microlens array 2 can be easily and easily obtained. In this case, for example, the focal length f is 10 mm, and the distance between the microlens array 2 and the focusing screen pattern surface 31a of the focusing screen 31 and the distance between the mask pattern surface 30a of the mask 30 are any. Is about 0.7 mm. Such a small focal length f can also be measured with high accuracy in this embodiment.

  According to the present invention, since the focal length of the microlens array can be measured with high accuracy in the inspection process after manufacturing, the present invention contributes to high performance of the microlens array.

1: Substrate 2: Microlens array 2a: Microlenses 2-1, 2-2, 2-3, 2-4: Unit microlens array 3: Mask 10: Aperture 10a: Light shielding film 11: Circular aperture 12: Hexagon Field stop 20: (CCD) Camera 21: Holder 22: Transmitted illumination light source 23, 24: Laser displacement meter 30: Mask 30a: Mask pattern surface 31: Focus plate 31a: Focus plate pattern surface 40, 41: Pattern

Claims (2)

In a focal length measurement device for a microlens array formed by laminating a plurality of unit microlens arrays configured by two-dimensionally arranging a plurality of microlenses in the thickness direction,
A camera that detects the image;
A focusing screen whose position relative to the camera is fixed such that the focal position of the camera and the focusing screen pattern surface of the lower surface coincide with each other with respect to the optical axis of the camera;
A light source that emits transmitted illumination light toward the camera;
A mask disposed between the light source and the focusing screen and provided with a mask pattern surface on the upper surface;
A laser displacement meter for measuring a distance between the focusing screen pattern surface of the focusing screen and the mask pattern surface of the mask;
Have
A microlens array is disposed between the focusing screen and the mask, and the mask pattern image incident on the camera via the microlens array is focused on the detection surface of the camera. The microlens array focal length measuring device, wherein the position of the mask with respect to the optical axis is adjusted, and the laser displacement meter measures the distance between the focusing screen pattern surface and the mask pattern surface. In a method for measuring a focal length of a microlens array configured by laminating a plurality of unit microlens arrays configured by two-dimensionally arranging a plurality of microlenses in the thickness direction,
A step of placing a focusing screen on an optical axis of a camera for detecting an image, and fixing the camera and the focusing screen by aligning a focal position of the camera with a focusing screen pattern surface on a lower surface of the focusing screen; When,
On the optical axis of the camera, in order from the focusing screen, a microlens array, a mask, and a transmitted illumination light source are disposed, and the transmitted illumination light is irradiated from the transmitted illumination light source toward the camera;
The mask pattern formed on the mask pattern surface on the upper surface of the mask is detected by the camera, and the position of the mask with respect to the optical axis of the camera is adjusted so that the mask pattern is in focus on the detection surface of the camera. Adjusting, and
Measuring the distance between the focusing screen pattern surface and the mask pattern surface with a laser displacement meter after the camera detects a focused image of the mask pattern;
A method for measuring a focal length of a microlens array, comprising:

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