JP2018081064A - Pattern height inspection device and method for inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device which can inspect relatively easily and rapidly the heights of various different types of patterns including a circuit pattern on a substrate, in a predetermined region or the entire region of the substrate.SOLUTION: An inspection device 100 includes: a stage 1 on which a substrate 2 is to be mounted; a light source 5 for irradiating the surface of the substrate on the stage with light; a camera 9 above the stage, the camera having a light receiving surface inclined to the surface of the stage and receiving light reflected from the surface of the substrate on the stage through a lens 12; and an operation device 11 for acquiring image information from each of a plurality of line sensors in the camera where reflected light enters, while moving the stage or the camera, and obtaining the height of a pattern using the distance in a direction vertical to the surface of the stage of at least one of the line sensors which successfully obtained image information in which the line width of the pattern on the substrate can be seen clearly.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pattern height inspection apparatus and inspection method, and more specifically to an inspection apparatus and inspection method for optically inspecting the height of a pattern formed on a substrate.

  When inspecting the height (thickness) of various patterns such as a circuit (wiring) formed on the surface of a semiconductor wafer such as silicon or a printed wiring board, a film thickness meter (level difference meter) for each pattern to be inspected Therefore, it is necessary to measure the height. However, as the number of patterns to be inspected increases, it takes a lot of time to individually measure the heights of all patterns. In particular, as the size of the substrate becomes larger and the pattern on the substrate becomes finer and densified, the measurement requires an enormous amount of time. Therefore, it is required to inspect the height of a plurality of patterns on the substrate at a higher speed and over a wide range.

  One of inspections using light performed in the manufacturing process of semiconductors, liquid crystals, etc. is a macro inspection. Macro inspection means that the surface condition (flatness, unevenness, pattern shape, presence / absence of defects, etc.) of the film provided on the substrate can be visually grasped at once in a wide range including the entire substrate. It is an effective inspection.

  Japanese Laid-Open Patent Publication No. 2011-122935 discloses an inspection method capable of measuring the height of the film edge on the wafer surface. In the inspection method, an image of the boundary portion 11a between the planar portion 11 and the upper bevel portion 12 in the wafer 10 is picked up with the autofocus unit 32 performing the focusing operation and without performing the focusing operation. Then, the height position of the boundary portion 11a with respect to a predetermined reference point in the case where the focusing operation is performed and the case where the focusing operation is not performed is detected from the image data in the vicinity of the end portion of the wafer 10, and the entire circumference of the wafer 10 is detected. By obtaining the height position of the boundary portion 11a, the warpage of the wafer 10 is obtained from the height variation of the boundary portion 11a.

JP 2011-122935 JP

In the inspection method of Patent Document 1, the height of the circuit pattern is not inspected over the entire wafer, and the state where the focusing operation is not performed is set by changing the height of the stage on which the wafer is placed. .
SUMMARY OF THE INVENTION An object of the present invention is to provide an inspection apparatus capable of inspecting the height of various patterns including circuit patterns formed on a substrate over a predetermined region or the whole of the substrate, and an inspection method thereof, relatively easily and at high speed. Is to provide.

  The present invention provides an inspection apparatus for inspecting the height of a pattern on a substrate. The inspection apparatus includes: (a) a stage on which a substrate is placed; (b) a light source that irradiates light on the surface of the substrate on the stage; and (c) light reception that is positioned above the stage and is inclined with respect to the surface of the stage. A camera having a surface and receiving reflected light from the surface of the substrate on the stage via a lens; and (d) each of a plurality of line sensors in the camera on which the reflected light is incident while moving the stage or the camera. Operation for obtaining image information and obtaining the height of the pattern using the distance in the vertical direction with respect to the surface of the stage of at least one line sensor from which the image information in which the line width of the pattern on the substrate is clearly visible was obtained An apparatus.

  The present invention provides a method for inspecting the height of a pattern on a substrate. The method includes (a) irradiating light onto the surface of the substrate on the stage, and (b) receiving reflected light with a camera through a lens while moving the surface including the pattern on the substrate. The camera is located above the stage and has a light receiving surface inclined with respect to the surface of the stage; and (c) acquires image information from each of the plurality of line sensors in the camera on which the reflected light is incident, Determining the height of the pattern using the distance in the vertical direction with respect to the surface of the stage of the stage of at least one line sensor from which image information in which the line width of the pattern on the substrate is clearly visible is obtained.

  According to the inspection apparatus and the inspection method of the present invention, it is possible to inspect the height of the pattern on the substrate or its variation at a macroscopic high speed over a predetermined region or the whole of the substrate with a relatively simple configuration.

It is a figure which shows the inspection apparatus of one Embodiment of this invention. It is an image figure (sectional view) which shows the positional relationship of the image sensor (line sensor) in the camera of one Embodiment of this invention, and a stage. It is an image figure (sectional drawing) for demonstrating the inspection method of this invention. It is a graph (relationship between height and pattern width) for demonstrating the inspection method of this invention. It is a graph (relationship between standard deviation of height and a luminance value) for explaining the inspection method of the present invention. It is a figure which shows the flow of the inspection method of one Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the following description, a case where a circuit board is used as a substrate will be described. However, it goes without saying that the present invention can also be applied to a case where another substrate having a pattern formed on the surface is used in the same manner as the circuit board. . In addition, the pattern said by this specification means the pattern which has predetermined length and width | variety, has a level | step difference (unevenness | corrugation) in cross-sectional shape, and consists of a material which can reflect light, for example, conductor (metal etc.) ) And a wiring (circuit) pattern made of a semiconductor, and an optical waveguide pattern made of a semiconductor or a dielectric.

  In FIG. 1, a circuit board 2 is placed on a circular stage 1. The stage 1 can be moved in the direction of rotation (θ), horizontal (X, Y) or vertical (Z) by the linear motor 3 under the control of the stage controller 4. The light source 5 is moved along the arc-shaped rail 6 by the stepping motor 7 under the control of the controller 8. The light source 5 can be set at a predetermined angle with respect to the surface of the stage 1. The predetermined angle can be arbitrarily set according to the measurement state. The brightness of the light source 5 is adjusted by a power source 10 for the light source.

  Similarly to the light source 5, the camera 9 is moved along the arc-shaped rail 6 by the stepping motor 7 under the control of the controller 8. A predetermined optical system 12 for guiding reflected light from the surface of the circuit board to a light receiving element in the camera 9 is provided at the front of the camera 9. The optical system 12 may be between the circuit board 2 and the camera 9 and may be integrated with the camera 9. As the light receiving element, a sensor in which an imaging element (pixel) is arranged in two dimensions (X, Y) called an area sensor or an image sensor can be used. In other words, the light receiving element can include a configuration in which a plurality of one-dimensional line sensors are arranged.

  The optical system 12 can include a lens or the like. The lens can be a high resolution lens with a narrow depth of field (DOF) which means the in-focus range. For example, a double-sided telecentric lens that is a lens for a line sensor can be used. The working distance (WD) is set corresponding to the resolution (resolution) of the image sensor necessary for detecting the size (height, width) of the pattern to be inspected. For example, when a pattern having a height of 500 μm is inspected, a resolution (resolution) of about 50 μm is sufficient, and the WD in that case can be about 960 mm, for example. The reflected light received by the lens is condensed on each image sensor of the image sensor.

  The output signal of the camera 9 enters the image processing means 11. The image processing unit 11 controls the power supply 10 for the stage controller 4, the controller 8, the camera 9, and the light source 5. The image processing means 11 is a predetermined processor such as a processor that performs arithmetic processing, a memory that stores image information, a display unit that displays inspection results (images, numerical values), and a signal input / output unit. The device can be included under the operation of software. In FIG. 1, only one light source 5 and one camera 9 are shown, but two or more may be arranged according to the size and shape of the circuit board 2. The above is the outline of FIG. Next, each configuration in FIG. 1 will be further described.

  The stage 1 can have any shape other than a circle. The stage 1 desirably has a surface that is as flat as possible. The stage 1 desirably has a structure in which reflected light from other than the surface of the circuit board 2 is hardly generated. The stage 1 is configured so that the circuit board 2 can be fixed so that the position of the circuit board 2 does not change when the stage moves while the circuit board 2 is placed. For example, the stage 1 includes jigs / mechanisms (projections, expansion / contraction portions, clip portions, chucks, etc.) provided on the surface that can restrain the outer periphery 3 and 4 of the circuit board 2 from the outside to the inside. be able to.

  As the light source 5, any light source that can irradiate light in a spot shape or a line shape can be used. The light source 5 can include, for example, a light emitting source such as a halogen bulb or LED and an optical system (lens, diffusion plate, etc.) for obtaining a diffusion effect thereon. When a line light source is used as the light source 5, for example, a plurality of light emitting elements are arranged in a line at a predetermined pitch on a long substrate. The light emitting element can be basically arbitrarily selected from not only semiconductor elements such as currently available light emitting diodes (LEDs) and laser diodes (LD) but also light emitting elements newly appearing in the future.

  The light source 5 is set at a predetermined distance from the surface of the stage 1. The light source 5 is set at a predetermined angle with respect to the surface of the stage 1. The predetermined angle can be arbitrarily set according to the measurement state or the like. The predetermined angle is, for example, in the range of 20 degrees to 80 degrees, and preferably in the range of 30 degrees to 70 degrees.

  FIG. 2 is an image diagram (sectional view) showing the positional relationship between the image sensor (line sensor) 90 in the camera, the stage 1 and the substrate 2 thereon. The image sensor 90 includes a plurality of line sensors 1 to n. The plurality of line sensors 1 to n extend to the back side of the paper surface (front surface) in FIG. 2 to form a two-dimensional image sensor (area sensor) having a rectangular or square plane (XY plane) as a whole. Yes. The camera 9 incorporating the image sensor 90 is disposed on the arc-shaped rail 6 so that the image sensor 90 is positioned in a direction inclined by a predetermined angle θ with respect to a plane parallel to the surface of the stage 1.

  As a result, each of the line sensors 1 to n is in a state in which the distance (height) H in the vertical direction with respect to the surface of the stage 1 is different from H1, H2, H3,. In other words, a plurality of line sensors having different distances H from the surface of the stage 1 are arranged above the substrate 2. The difference ΔH in the distance H between two adjacent line sensors changes depending on the pitch P (interval) between the line sensors of the two-dimensional image sensor to be used. That is, the difference ΔH of the distance H can be obtained by ΔH = P * sin θ. For example, the difference ΔH of the distance H between the 10th and 15th line sensors can be obtained as (15-10) * P * sin θ.

  The principle of the pattern height inspection method of the present invention will be described with reference to the cross-sectional image of FIG. FIG. 3 shows a case where the pattern 20 having the protrusion B with the height h is inspected using the tilted image sensor 90 described with reference to FIG. In (a), a state in which reflected light (broken arrows) from the surface of the pattern 20 enters each of the line sensors 1 to n in the image sensor 90 is shown. FIG. 5B is a similar image diagram when the image sensor 90 moves leftward or when the stage on which the substrate including the pattern 20 is moved moves rightward. While the image sensor 90 or the pattern 20 (stage) is moving, n images in the area including the pattern 20, that is, one image information (total n images) is obtained from each of the line sensors 1 to n.

  In the obtained n images, the sharpness of the pattern 20 in each image differs due to the difference in the distance (height) H in the vertical direction of the line sensors 1 to n described above. That is, when the focus state of the camera with respect to the pattern 20 (incident light quantity at each line sensor) changes, there is a difference in the sharpness in the region including the pattern 20 in each image. For example, when a clear image focused by the line sensor 3 or 4 is obtained, the images from the other line sensors are blurred images with low defocus clarity. In the present invention, the height h of the pattern is obtained based on a plurality of pieces of image information including patterns obtained from the line sensors 1 to n having different vertical heights (positions).

  FIG. 4 is a diagram for explaining an inspection (measurement) method for obtaining the pattern height h of the present invention. In the figure, the horizontal axis represents the position (height) of each line sensor, and the vertical axis represents the pattern width on the image obtained by each line sensor. The position (height) of each line sensor on the horizontal axis corresponds to, for example, the position (height) of n line sensors 1 to n in the image sensor 90 of FIG. A graph M1 in the figure shows a pattern width on an image obtained from each line sensor when a pattern having a known line width w1 and height h1 is measured.

  In the graph M1, it means that the image of the line sensor at the position (height) of the narrowest (minimum value) P0 pattern displays the pattern most clearly. That is, it means that the camera is focused on the pattern in the line sensor at the position (height) of P0. Note that the graph M1 can be measured simultaneously with the measurement of the graph M2 shown below, or the data can be obtained by measuring in advance. That is, it may be obtained in advance as calibration curve data.

  A graph M2 shows the pattern width on the image obtained from each line sensor when a pattern having the same known line width w1 and an unknown height h is measured. In the graph M2, this means that the image of the line sensor at the position (height) of the narrowest (minimum value) Pn pattern displays the pattern most clearly. That is, it means that the camera is in focus with respect to the pattern in the line sensor at the position (height) of Pn. However, the pattern width on the obtained image tends to be wider (blurred) than in the measurement of the graph M1. This is because the focus state on the pattern surface is slightly deviated from the case of M1.

  The position (height) of the image sensor that is in focus is different between P0 and Pn because there is a difference (difference) in the height of the pattern. That is, in the state of FIG. 4, the difference (HP0−HPn) in the position (height) of the image sensor is equal to the difference Δh = (h−h1) between the known height h1 and the unknown height h of the pattern. Become. Therefore, the unknown height h of the pattern can be obtained as h = h1 + Δh.

  In FIG. 4, the pattern height h is obtained while observing the pattern width on the actually obtained image, but as another method, the standard deviation (or variance) of the luminance value obtained from the output of each line sensor. The height h of the pattern can be obtained while observing. FIG. 5 is a diagram showing the relationship between the standard deviation of the luminance value and the position (height) of each line sensor. A graph M3 in the figure shows a standard deviation of luminance values obtained from each line sensor when a pattern having a known line width w1 and height h2 is measured. That is, it corresponds to a calibration curve graph. In the graph M3, it means that the output signal (the amount of received light) of the line sensor at the position (height) at which the standard deviation of the luminance value is the largest (maximum value) P1 is the largest. That is, it means that the camera is focused on the pattern in the line sensor at the position (height) of P1.

  A graph M4 shows the standard deviation of the luminance value obtained from each line sensor when the pattern having the same known line width w1 and the unknown height h is measured. In the graph M4, it means that the output signal (light reception amount) of the line sensor at the position (height) at which the standard deviation of the luminance value is the largest (maximum value) Pm is the largest. That is, it means that the camera is focused on the pattern in the line sensor at the position (height) of Pm. The reason why the standard deviation of the in-focus luminance values differs between P1 and Pm is that there is a difference (difference) in the height of the pattern. That is, in the state of FIG. 5, the difference (HP1-HPm) in the position (height) of the image sensor is equal to the difference Δh = (h−h2) between the known height h2 and the unknown height h of the pattern. Become. Therefore, the unknown height h of the pattern can be obtained as h = h2 + Δh.

  Next, a pattern height inspection flow according to an embodiment of the present invention will be described with reference to FIG. FIG. 6 is a diagram showing a pattern height inspection flow according to an embodiment of the present invention. The flow of FIG. 6 is executed by the inspection apparatus 100 of the embodiment of FIG.

  In step S11, a substrate is set on the stage 1. As already described, the circuit board 2 having a circuit pattern or the like formed on the surface can be included. Hereinafter, the case of the circuit board 2 will be described. At that time, as already described above, the circuit board 2 is moved by the jig / mechanism provided on the surface of the stage 1 so that the position of the circuit board 2 does not move when the stage moves. 2 is fixed to the surface of the stage 1. In step S <b> 12, light is irradiated from the light source 5 to the inspection area on the surface of the circuit board 2. As the inspection area, a predetermined area including a predetermined pattern on a predetermined substrate or the entire circuit board is selected.

  In step S <b> 13, the camera 9 receives reflected light from the surface of the circuit board 2 through the optical system 12 (including a lens) at a predetermined distance from the surface of the circuit board 2. In step S14, it is determined whether or not there is an uninspected area. If Yes, the stage 1 or the camera 9 is moved to move (change) the inspected area. Thereafter, light irradiation to the circuit board in step S12 and reflected light reception in step 13 are performed. The same flow is repeated until there are no uninspected areas including other patterns, and then the height h of at least one pattern is calculated from the obtained image information from each of the line sensors 1 to n. The calculation method is as described with reference to FIGS. The obtained height information of the plurality of patterns is displayed on the screen of the display device included in the image processing unit 11 as a numerical value corresponding to each pattern or a macro image (map) including the height distribution of the inspection area of the circuit board 2. ) Is displayed.

  A substrate including a pattern having a height h = 15.891 μm measured by a film thickness meter is measured using the inspection apparatus 100 of FIG. 1, and the line width of the pattern and the height of the line sensor as shown in FIG. 4 are measured. When the relationship was obtained and the height of the pattern was calculated from the height difference Δh, the height h = 14.669 μm could be obtained.

  Similarly, using the inspection apparatus 100 of FIG. 1, a substrate including a pattern with a height h = 0.0514 mm measured by a film thickness meter is measured, and the standard deviation of the luminance value and the line sensor as shown in FIG. When the height relationship was obtained and the height of the pattern was calculated from the height difference Δh, the height h = 0.0651 mm could be obtained.

  The embodiment of the present invention has been described with reference to FIGS. However, the present invention is not limited to these embodiments. The present invention can be implemented in variously modified, modified, and modified embodiments based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

1 Stage 2 Board (circuit board, etc.)
3 linear motor 4 stage controller 5 light source 6 rail 7 stepping motor 8 controller 9 camera 10 power source for light source 11 image processing means (computer)
12 Optical system (lenses, etc.)
20 patterns 90 image sensor (area sensor)
100 inspection equipment

Claims (7)

An inspection device for inspecting the height of a pattern on a substrate,
A stage on which a substrate is placed;
A light source for irradiating the surface of the substrate on the stage with light;
A camera located above the stage, having a light receiving surface inclined with respect to the surface of the stage, and receiving reflected light from the surface of the substrate on the stage via a lens;
Image information was obtained from each of the plurality of line sensors in the camera on which the reflected light was incident while moving the stage or the camera, and image information in which the line width of the pattern on the substrate was clearly visible was obtained. An inspection device comprising: an arithmetic device for obtaining a height of the pattern using a distance in a vertical direction of at least one line sensor with respect to a surface of the stage.   The image information in which the line width of the pattern on the substrate is clearly visible includes image information obtained in a state where the camera is focused on the pattern in the at least one line sensor. The inspection device described.   The arithmetic unit is configured to obtain a distance (H1) in the vertical direction and a height (h) of a line sensor that obtains image information in which a line width of a pattern having a known height (h1) on the substrate is clearly visible. The height of the pattern whose height is not known from the difference (ΔH = H1−H2) from the distance (H2) in the vertical direction of the line sensor that obtained the image information in which the line width of the pattern with the unknown is clear. 3. The inspection apparatus according to claim 1, wherein h = h1 + ΔH) is obtained.   The inspection apparatus according to claim 1, wherein the plurality of line sensors includes a plurality of line sensors included in an image sensor in the camera.   The inspection device according to claim 1, wherein the lens includes a telecentric lens. A method for inspecting the height of a pattern on a substrate,
Irradiating the surface of the substrate on the stage with light;
Receiving reflected light with a camera through a lens while moving a surface including a pattern on the substrate, wherein the camera is positioned above the stage and tilted with respect to the surface of the stage A step having a surface;
Image information is acquired from each of the plurality of line sensors in the camera on which the reflected light is incident, and image information in which the line width of the pattern on the substrate is clearly visible is obtained. Determining the height of the pattern using a distance in a vertical direction relative to the surface.   The step of obtaining the height of the pattern includes a distance (H1) in the vertical direction of the line sensor that obtains image information in which the line width of the pattern having a known height (h1) on the substrate is clearly visible, The height is not known from the difference (ΔH = H1−H2) from the distance (H2) in the vertical direction of the line sensor that obtained the image information in which the line width of the pattern whose height (h) is not known is clearly visible. 7. The method according to claim 6, comprising the step of determining the height of the pattern (h = h1 + ΔH).

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