JP2017009581A - Shape measurement device and coating device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape measurement device that can easily align a focus of an interferometer with surfaces of objects.SOLUTION: A control device 6 of a shape measurement device is configured to control a piezo stage 5 and an imaging device 4; photograph respective images at a plurality of positions h as moving an interferometer 3 in an optical axis direction; obtain a degree of separation R by a discrimination analysis method about a luminance histogram of a pixel of each image; arrange the piezo stage 5 at a position hf corresponding to the image in which the degree of separation R becomes a maximum value Rmax of a plurality of images; and thereby arrange a focus P1 of the interferometer 3 on a surface of an object 7. Accordingly, the focus P1 of the interferometer 3 can be easily aligned with the surface of the object 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shape measuring device and a coating device equipped with the same, and more particularly to a shape measuring device that measures the surface shape of an object using an interferometer. More specifically, the present invention relates to a shape measuring device that measures the surface shape of metals, resins, processed products thereof, and the like, and measures the surface shape of substrates such as semiconductor devices, electronic circuits, and flat panel displays.

  Japanese Patent Laid-Open No. 2004-228561 shoots images at a plurality of positions while moving a CCD camera relative to an object using a Z table, and differentiates luminance values of a plurality of pixels included in each image (hereinafter referred to as image differentiation). An autofocus device is disclosed in which the CCD camera is focused on an object by calculating the value of the CCD camera at a position corresponding to an image having a maximum differential value.

JP 2000-56210 A

  The differential value of the image becomes a large value at a place where the light and dark pattern changes suddenly, such as a boundary between the object and the background. In an image taken in focus, the boundary between the object and the background becomes clearer and the differential value of the image becomes larger than in an image taken in out of focus. Therefore, the CCD camera can be focused on the object by arranging the CCD camera at a position where the differential value of the image is maximized.

  By the way, in a shape measuring apparatus that measures the surface shape of an object using an interferometer, the measurement is usually started after the interferometer is focused on the reference surface of the object. As the reference plane of the target object, a plane part such as the upper end surface of the target object or the apex part of the spherical surface is often selected. In such a reference plane, the shape and the light / dark pattern change gradually, the light / dark change of the interference fringe also becomes gentle, and the differential value of the interference fringe image is small. Therefore, as in Patent Document 1, it is difficult to focus the interferometer on the reference plane using only the differential value of the interference fringe image. Further, in the conventional technique (Patent Document 1), a target pattern is necessary for focusing, and if there is no target, a problem may occur in the focusing operation.

  Therefore, a main object of the present invention is to provide a shape measuring device capable of easily focusing an interferometer on the surface of an object.

  The shape measuring apparatus according to the present invention is a shape measuring apparatus for measuring the surface shape of an object, and separates white light emitted from an illuminating device into first and second light beams, and targets the first light beam. Irradiate the surface of the object and irradiate the reference surface with the second light beam, and combine the reflected light from the surface of the object and the reflected light from the reference surface to generate interference fringes corresponding to the surface shape of the object Interferometer, an observation optical system for observing the interference fringe, an imaging device for photographing an image of the interference fringe via the observation optical system, and a first object for relatively moving the object and the interferometer in the optical axis direction. The apparatus includes a positioning device, and a control device that controls the imaging device and the first positioning device, and executes a first autofocus operation for focusing the interferometer on the surface of the object. In the first autofocus operation, the control device photographs each image at a plurality of relative positions while relatively moving the object and the interferometer in the optical axis direction, and a plurality of pixels included in the image for each image. The degree of separation by the discriminant analysis method is obtained for the luminance distribution diagram of FIG. 5, and the object and the interferometer are arranged at a relative position corresponding to the image having the maximum degree of separation among the plurality of images.

  In the shape measuring apparatus according to the present invention, for each image, the degree of separation by the discriminant analysis method is obtained for the luminance distribution diagram of the plurality of pixels included in the image, and the image having the maximum degree of separation among the plurality of images is supported. The interferometer is focused on the surface of the object by placing the object and the interferometer at relative positions. Therefore, the interferometer can be easily focused on the surface of the object. In addition, since the focus of the interferometer can be easily and reliably focused on the surface of the object, there is no problem in the work performed after the focus adjustment, and the work efficiency can be improved. Furthermore, the total work time including the process of the present invention can be shortened, and the manufacturing cost of the product can be reduced.

It is a block diagram which shows the structure of the shape measuring apparatus by Embodiment 1 of this invention. It is a figure which shows the structure of the shape measuring apparatus shown in FIG. 1 in detail. It is a figure which shows the structure and operation | movement of a mirrow type interferometer shown in FIG. FIG. 4 is a luminance histogram of an interference fringe image generated by the mirrow interferometer shown in FIG. 3. FIG. It is a figure which shows the relationship between the position of the piezo stage shown in FIG. 1, and the separation degree of an image. It is a figure which illustrates the autofocus operation | movement of the shape measuring apparatus shown in FIGS. It is a block diagram which shows the structure of the shape measuring apparatus by Embodiment 2 of this invention. It is a figure which illustrates the automatic focus operation | movement of the shape measuring apparatus shown in FIG. It is a perspective view which shows the whole structure of the coating device with which the shape measuring apparatus according to this Embodiment is mounted. It is a perspective view which shows the principal part of an observation optical system and an ink application | coating mechanism. It is the figure which looked at the principal part from the A direction of FIG. FIG. 3 is a first diagram for explaining an ink application operation. FIG. 6 is a second diagram for explaining the ink application operation. FIG. 3 is a third diagram for explaining an ink application operation. FIG. 4 is a fourth diagram for explaining the ink application operation. It is FIG. 5 for demonstrating ink application | coating operation | movement. It is a figure for demonstrating the film thickness inspection method. It is a flowchart for demonstrating a film thickness test | inspection process.

[Embodiment 1]
FIG. 1 is a block diagram showing a configuration of a shape measuring apparatus according to Embodiment 1 of the present invention. In FIG. 1, the shape measuring apparatus includes a head unit 10 including an illuminating device 1, an observation optical system 2, a millo interferometer 3, an imaging device 4, and a piezo stage (first positioning device) 5. And a control device 6. The illumination device 1 outputs white light. The observation optical system 2 reflects white light output from the illuminating device 1 and applies the reflected white light to the mirrow interferometer 3, and is used for observing interference fringes generated by the mirrow interferometer 3.

  The mirrow interferometer 3 separates the white light incident from the illumination device 1 via the observation optical system 2 into first and second light beams, irradiates the surface of the object 7 with the first light beam, and the first light beam. 2 is irradiated onto the reference surface, and interference fringes are generated by causing the reflected light from the surface of the object 7 to interfere with the reflected light from the reference surface. The imaging device 4 is controlled by the control device 6 and captures an image of interference fringes generated by the Milo interferometer 3 via the observation optical system 2. Each image photographed by the imaging device 4 is stored in the control device 6. The piezo stage 5 is controlled by the control device 6 and moves the mirrow interferometer 3 relative to the object 7 in the optical axis direction (vertical direction).

  The control device 6 controls the entire shape measuring device. In particular, the control device 6 controls the image pickup device 4 and the piezo stage 5 and takes images at a plurality of positions while moving the mirrow interferometer 3 relative to the object 7 in the optical axis direction. Based on this image, an auto-focus operation (first auto-focus operation) for focusing the mirror-type interferometer 3 on the surface of the object 7 is executed. The autofocus operation will be described in detail later.

  2 is a diagram showing the configuration of the shape measuring apparatus shown in FIG. 1 in more detail, and FIG. 3 is a diagram showing the configuration and operation of the mirrow interferometer 3. 2 and 3, the illumination device 1 is disposed on the side surface of the observation optical system 2 and includes a white light source 11 and a filter 12. The optical axis A1 of the illumination device 1 (that is, the optical axis of the white light source 11) is arranged in the horizontal direction and is orthogonal to the optical axis A2 of the observation optical system 2. The white light source 11 emits white light. The filter 12 is disposed between the white light source 11 and the observation optical system 2 and allows white light having a predetermined center wavelength λ0 and a wavelength range Δλ among white light emitted from the white light source 11 to pass therethrough.

  The observation optical system 2 includes a condenser lens 21, a half mirror 22, and an imaging lens 23. The optical axis A2 of the observation optical system 2 (that is, the optical axis of the imaging lens 23) is arranged in the vertical direction. The condenser lens 21 is disposed between the filter 12 and the half mirror 22, and converts the white light emitted from the white light source 11 and passed through the filter 12 into parallel light.

  The half mirror 22 is disposed at the intersection of the two optical axes A1 and A2, and is disposed at an angle of 45 degrees with respect to each of the two optical axes A1 and A2. The Millo interferometer 3 is disposed below the half mirror 22, and the imaging lens 23 and the imaging device 4 are disposed above the half mirror 22. The half mirror 22 reflects the white light incident from the illumination device 1 via the condenser lens 21 downward, and allows the light from the mirrow interferometer 3 (that is, an image of interference fringes) to pass upward. The imaging lens 23 forms an image of the light from the Milo interferometer 3 on the optical sensor of the imaging device 4.

  The mirrow interferometer 3 is provided at the lower end of the observation optical system 2 via the piezo stage 5 and includes an objective lens 31, a reflecting mirror 32, and a semi-transparent mirror 33. The optical axis A3 of the Millo interferometer 3 (that is, the optical axis of the objective lens 31) coincides with the optical axis A2 of the observation optical system 2. The piezo stage 5 moves the mirro interferometer 3 in the direction of the optical axis A3. 2 and 3, the object 7 is a substrate, the optical axis A3 is arranged perpendicular to the surface of the substrate, and the focal point P1 (that is, the focal point of the objective lens 31) of the mirro interferometer 3 is arranged on the surface of the substrate. The state is shown.

  The reflecting mirror 32 is fixed to the center of the lower surface of the objective lens 31 with its reflecting surface (reference surface) facing downward. The semi-transparent mirror 33 is disposed at an intermediate position between the reflecting surface of the reflecting mirror 32 and the focal point P1. Each of the reflecting mirror 32 and the semi-transparent mirror 33 is orthogonal to the optical axis A3.

  As shown in FIG. 3, the white light L0 emitted from the illumination device 1 and incident on the mirro interferometer 3 through the observation optical system 2 is refracted by the objective lens 31 and travels toward the focal point P1. Part of the white light L0 passes through one end portion of the semi-transparent mirror 33 to become the first light beam L1, and the remaining part of the white light L0 is reflected by one end portion of the semi-transparent mirror 33 and becomes the second light beam L2. Become. That is, the white light L0 is separated into the first and second light beams L1 and L2 by the half mirror 33.

  The first light beam L1 is reflected by the surface of the object 7 to become the first reflected light L1r and travels toward the other end of the semi-transparent mirror 33. The second light beam L2 is reflected by the reflecting surface of the reflecting mirror 32 to become second reflected light L2r, and travels toward the other end of the semi-transparent mirror 33. The first and second reflected lights L1r and L2r merge at the other end of the semi-transparent mirror 33 and interfere with each other to become interference light L3.

  When the phase difference between the two reflected lights L1r and L2r is 0 degree, the amplitude of the interference light L3 is maximized, and the brightness of the interference light L3 is maximized. When the phase difference between the two reflected lights L1r and L2r is 180 degrees, the amplitude of the interference light L3 is minimized, and the brightness of the interference light L3 is minimized. The mirrow interferometer 3 is designed so that the difference in optical path length between the reflected lights L1r and L2r becomes zero when the first light beam L1 is reflected at the focal point P1.

  Therefore, when the focal point P1 of the mirrow interferometer 3 coincides with the surface of the object 7 (that is, when the focal point is in focus), the phase difference and the optical path length difference between the reflected light L1r and L2r are both 0, and the interference light L3 Becomes the brightest, and the interference light L3 becomes darker as the distance between the focal point P1 and the surface of the object 7 increases. Interference fringes corresponding to the surface shape of the object 7 appear on the semi-transparent mirror 33. The surface shape of the object 7 can be measured based on the interference fringes.

  In order to obtain a clear interference fringe, it is necessary to make the focal point P1 of the mirrow interferometer 3 coincide with the surface of the object 7. Hereinafter, an automatic focusing operation for matching the focal point P1 of the Milo type interferometer 3 with the surface of the object 7 will be described.

  During the autofocus operation, the control device 6 controls the imaging device 4 and the piezo stage 5 to photograph a plurality of images at a plurality of positions while moving the mirrow interferometer 3 in the direction of the optical axis A3. A luminance histogram of each of a plurality of images is created, a separation value R obtained by a discriminant analysis method is obtained for each luminance histogram, and a mirrow interferometer 3 is disposed at a position where the separation value R is maximum.

  FIG. 4 is a luminance histogram of an interference fringe image. The image includes a plurality of pixels arranged in a plurality of rows and a plurality of columns. Each pixel displays the luminance at any one of a plurality of levels (for example, 256 levels). The horizontal axis of FIG. 4 indicates the luminance at a plurality of levels, and the vertical axis indicates the number of pixels displaying each luminance. When the focal point P1 of the mirro interferometer 3 is brought closer to the surface of the object 7, the luminance histogram shows bimodality as shown in FIG.

In the discriminant analysis method, the luminance histogram of an image is separated into two classes CL1 and CL2 by the luminance threshold value Lth. Class CL1 is a group of pixels whose luminance is smaller than luminance threshold Lth. Class CL2 is a group of pixels whose luminance is greater than luminance threshold Lth. The luminance threshold Lth is set so that the intra-class variance σ _W ² is minimized and the inter-class variance σ _B ² is maximized, and the ratio σ between the inter-class variance σ _B ² and the intra-class variance σ _W ² _B ² / σ _W ² is the separation degree R.

The intra-class variance σ _W ² is the degree of spread of the histogram within the class, and the inter-class variance σ _B ² is the degree of spread between the two classes CL1 and CL2. The intra-class variance σ _W ² and the inter-class variance σ _B ² are respectively expressed by equations (1) and (2).

σ _W ² = (n ₁ × σ ₁ ² + n ₂ × σ ₂ ² ) / (n ₁ + n ₂ ) (1)
σ _B ² = [n ₁ (μ ₁ −μ ₀ ) ² + n ₂ (μ ₂ −μ ₀ ) ² ] / (n ₁ + n ₂ ) (2)
However, σ ₁ ² and σ ₂ ² are the variances of the luminance in the classes CL1 and CL2, respectively, μ ₀ is the average value of the luminance of all the pixels, and μ ₁ and μ ₂ are the luminances in the classes CL1 and CL2, respectively. N ₁ and n ₂ are the numbers of pixels in the classes CL1 and CL2, respectively.

  FIG. 5 is a diagram illustrating the relationship between the position h of the piezo stage 5 and the degree of separation R. In FIG. 5, a plurality of images are photographed while changing the position h of the piezo stage 5 (the coordinate in the height direction of the movable part of the piezo stage 5) from 0 μm to 20 μm, and a luminance histogram of each image is generated. The case where the degree of separation R of the histogram is obtained is shown. In FIG. 5, the degree of separation R increases from 0 when h≈7.5 μm, reaches a maximum value (about 0.105) when h≈9.2 μm, then decreases, and h When it reached ≈10.7 μm, it became zero. By disposing the piezo stage 5 at the position (h≈9.2 μm) when the separation degree R reaches the maximum value (about 0.105), the focal point P1 of the mirrow interferometer 3 is placed on the surface of the object 7. I was able to match.

  Next, the autofocus operation in this shape measuring apparatus will be specifically described. The control device 6 controls the imaging device 4 and the piezo stage 5 during the autofocus operation, and takes images at a plurality of positions h while moving the mirrow interferometer 3 in the direction of the optical axis A3 at a constant speed V1. To do. If the image capture period of the imaging device 4 is T1 (seconds) and the center wavelength of the white light output from the illumination device 1 is λ0 (μm), the Miro interferometer during the capture period T1 (seconds). The moving speed V1 of the Milo type interferometer 3 is set so that 3 moves by λ0 / 8 (μm). The direction in which the mirrow interferometer 3 first moves is any one of the direction in which the mirrow interferometer 3 approaches the object 7 and the direction in which the mirrow interferometer 3 moves away.

  While the mirrow interferometer 3 is moved at a constant speed V1 by the piezo stage 5, the control device 6 captures an image from the imaging device 4 at a predetermined cycle T1 (seconds). The control device 6 calculates the image separation degree R every time the image capture is completed, and obtains the position hf of the piezo stage 5 when the image having the maximum separation degree R is taken. Finally, the control device 6 sets the position h of the piezo stage 5 to the position hf when the image having the maximum degree of separation R is taken, and ends the autofocus operation.

  More specifically, when the driving speed of the piezo stage 5 reaches a constant speed V1, the control device 6 starts calculating the image separation degree R while capturing images from the imaging device 4 at intervals of T1 (seconds). The separation degree R is stored in a memory unit (not shown) in association with the position h of the piezo stage 5 at the time of capture.

  After storing the separation degree R and the position h of a plurality of sets (for example, three sets), as shown in FIGS. 6A and 6B, the horizontal axis shows the position h and the vertical axis shows the separation degree R. Write an approximate straight line connecting multiple points. In FIG. 6A, the piezo stage 5 is movable from the position h1 to the position h2, and the piezo stage 5 is moved in the direction from h2 to h1.

  For example, as shown in FIG. 6A, when the degree of separation R decreases with respect to the moving direction of the position h of the piezo stage 5, the piezo stage 5 is temporarily stopped and then shown in FIG. As shown, the piezo stage 5 is moved in the opposite direction, and an image is captured at a predetermined cycle T1 (seconds) while moving the piezo stage 5 until the position h reaches h2. From the beginning, when the degree of separation R increases with respect to the moving direction of the position h of the piezo stage 5, an image is captured at a predetermined cycle T1 (seconds) while moving the piezo stage 5 until the position h becomes h1. .

  The image separation degree R is obtained while capturing the image, and the position h of the piezo stage 5 corresponding to the image with the separation degree R having the maximum value Rmax is obtained. That is, after storing a plurality of sets (for example, eight sets) of separation degrees R and positions h, a maximum value Rmax of the plurality of separation values R is obtained. Next, the absolute value ΔRs = | Rmax−Rs | of the difference between the maximum value Rmax and the first set of separation values Rs and the absolute value ΔRe = | Rmax of the difference between the maximum value Rmax and the separation value Re of the last set -Re | is obtained, and when ΔRs and ΔRe are both larger than a predetermined threshold value Rth, the position hf of the piezo stage 5 corresponding to the image having the separation degree R of the maximum value Rmax is obtained, and the piezo is located at the position hf. The stage 5 is moved. At this time, the position of the focal point P <b> 1 of the millo interferometer 3 coincides with the surface of the object 7.

  If at least one of ΔRs and ΔRe is smaller than the threshold value Rth, the search is continued until the piezo stage position reaches h1 or h2. If Rmax in which ΔRs and ΔRe are both greater than the predetermined threshold value Rth cannot be detected even when h1 or h2 is reached, the piezo stage 5 is returned to the search start position, and the piezo stage position is h1 or The search is continued until h2 is reached. When Rmax in which both ΔRs and ΔRe are larger than the predetermined threshold value Rth cannot be detected between h1 and h2, the autofocus operation is terminated as a failure.

  More specifically, in FIG. 6 (a), image capture is started from the position N = 1, and after capturing the image at the position N = 3, an approximate straight line connecting the three points is obtained and moved in the moving direction. On the other hand, it was determined that the slope of the approximate line was negative, and the search was started in the opposite direction as shown in FIG. In the search in the opposite direction, the image acquisition is started from the position of M = 1, the image is acquired from the position of M = 8, the peak determination is started, and the separation degree R at the position of M = 5 is the maximum value Rmax. It is determined that ΔRs and ΔRe are both larger than the threshold value Rth, the piezo stage 5 is disposed at the position hf corresponding to M = 5, and the focal point P1 of the Milo interferometer 3 is set to the object 7. Matched to the surface.

  As described above, in the first embodiment, the piezo stage 5 and the imaging device 4 are controlled, and images are taken at a plurality of positions h while moving the mirrow interferometer 3 in the optical axis direction. By obtaining the separation degree R by the discriminant analysis method with respect to the luminance histogram of the pixel, and arranging the position h of the piezo stage 5 at the position hf corresponding to the image where the separation degree R of the plurality of images has the maximum value Rmax, The focal point P1 of the millo interferometer 3 is arranged on the surface of the object 7. Therefore, the focal point P1 of the Milo interferometer 3 can be easily adjusted to the surface of the object 7, and the working efficiency can be improved.

  In the first embodiment, the object 7 is fixed and the mirrow interferometer 3 is moved by the piezo stage 5. However, the present invention is not limited to this, and the object 7 and the mirrow interferometer 3 are relatively moved. As long as it is moved to, it may be moved by any method. For example, the mirrow interferometer 3 may be fixed and the object 7 may be moved, or both the mirrow interferometer 3 and the object 7 may be moved in opposite directions.

  In the first embodiment, the case of using the Milo type interferometer 3 has been described. However, the present invention is not limited to this, and other types of interferometers may be used. For example, a Michelson interferometer or a linique interferometer may be used.

[Embodiment 2]
FIG. 7 is a diagram showing the configuration of the shape measuring apparatus according to the second embodiment of the present invention, and is compared with FIG. Referring to FIG. 7, this shape measuring apparatus is different from the shape measuring apparatus of FIG. 1 in that a Z stage (second positioning device) 40 is added. The illumination device 1, the observation optical system 2, the Millo interferometer 3, the imaging device 4, and the piezo stage 5 constitute one optical unit, and this optical unit is mounted on the Z stage 40. The Z stage 40 is controlled by the control device 6 and moves the optical unit in the height direction.

  The stroke of the Z stage 40 is larger than the stroke of the piezo stage 5. In the first embodiment, a plurality of images are photographed while moving the mirrow interferometer 3 only by the piezo stage 5 and focused based on the separation degree R of the plurality of photographed images (first autofocus operation) However, in the second embodiment, before the first autofocus operation is performed, a plurality of images are captured while the Miro interferometer 3 is moved by the Z stage 40, and the differential values of the plurality of images captured. The focal position is roughly adjusted based on D (second automatic focusing operation). This is effective when focus cannot be achieved within the stroke of the piezo stage 5.

  Next, the second autofocus operation in this shape measuring apparatus will be specifically described. During the second autofocus operation, the control device 6 controls the imaging device 4 and the Z stage 40, and moves the mirrow interferometer 3 in the direction of the optical axis A3 at a constant speed V2 at each of a plurality of positions H. Take a picture. The moving speed V2 of the Z stage 40 is larger than the moving speed V1 of the piezo stage 5. The direction in which the mirrow interferometer 3 first moves is any one of the direction in which the mirrow interferometer 3 approaches the object 7 and the direction in which the mirrow interferometer 3 moves away.

  While the mirrow interferometer 3 is moved at a constant speed V2 by the Z stage 40, the control device 6 captures an image from the imaging device 4 at a predetermined period T2 (seconds). The control device 6 calculates the differential value D of the image every time the image capture is completed, and the position Hf of the Z stage 40 (movable part of the Z stage 40) when the image having the maximum differential value D is taken. For the height direction). Finally, the control device 6 sets the position H of the Z stage 40 to the position Hf when the image having the maximum differential value D is taken, and ends the second autofocus operation. The differential value D of the image is expressed by equations (3), (4), and (5).

  Here, F represents the captured image, (x, y) represents the pixel position of the image F, dx represents the horizontal differential value, and dy represents the vertical differential value.

  More specifically, when the driving speed of the Z stage 40 reaches the constant speed V2, the control device 6 starts calculating the differential value D of the image while capturing the image from the imaging device 4 at intervals of T2 (seconds), and The differential value D is stored in a memory unit (not shown) in association with the position H of the Z stage 40 at the time of capture.

  After storing a plurality of sets (for example, three sets) of differential values D and positions H, as shown in FIGS. 8A and 8B, the horizontal axis indicates the position H and the vertical axis indicates the differential value D. Write an approximate straight line connecting multiple points. FIG. 8A shows a state in which the Z stage 40 is movable from the position H1 to the position H2, and the Z stage 40 is moved in the direction from H2 to H1.

  For example, as shown in FIG. 8A, when the differential value D is decreasing with respect to the moving direction of the position H of the Z stage 40, the Z stage 40 is temporarily stopped and then shown in FIG. 8B. As shown, the Z stage 40 is moved in the opposite direction, and an image is captured at a predetermined cycle T2 (seconds) while moving the Z stage 40 until the position H reaches H2. When the differential value D increases from the beginning with respect to the movement direction of the position H of the Z stage 40, an image is captured at a predetermined cycle T2 (seconds) while moving the Z stage 40 until the position H becomes H1. .

  The differential value D of the image is obtained while capturing the image, and the position Hf of the Z stage 40 corresponding to the image where the differential value D becomes the maximum value Dmax is obtained. That is, after storing a plurality of sets (for example, 8 sets) of differential values D and positions H, a maximum value Dmax of the plurality of differential values D is obtained. Next, the absolute value ΔDs = | Dmax−Ds | of the difference between the maximum value Dmax and the first set of differential values Ds, and the absolute value ΔDe = | Dmax of the difference between the maximum value Dmax and the last set of differential values De -De | is obtained, and when both ΔDs and ΔDe are larger than a predetermined threshold value Dth, the position Hf of the Z stage 40 corresponding to the image where the differential value D becomes the maximum value Dmax is obtained. The stage 40 is moved. At this time, the position of the focal point P <b> 1 of the Milo type interferometer 3 substantially coincides with the surface of the object 7.

  If at least one of ΔDs and ΔDe is smaller than the threshold value Dth, the search is continued until the piezo stage position reaches H1 or H2. If Dmax in which both ΔDs and ΔDe are larger than the predetermined threshold value Dth cannot be detected even when H1 or H2 is reached, the piezo stage 5 is returned to the search start position, and the piezo stage position is H1 or The search continues until H2 is reached. If Dmax in which both ΔDs and ΔDe are larger than the predetermined threshold value Dth cannot be detected between H1 and H2, the autofocus operation is terminated as a failure.

  Thereafter, the Z stage 40 is fixed at the position Hf corresponding to the image where the differential value D becomes the maximum value Dmax, and the focus of the Milo type interferometer 3 by the method described in the first embodiment (first autofocus operation). P1 is precisely matched with the surface of the object 7.

  More specifically, in FIG. 8A, the image capture is started from the position N = 1, the image is captured at the position N = 3, an approximate straight line connecting the three points is obtained, and the moving direction is determined. On the other hand, it was determined that the slope of the approximate line was negative, and the search was started in the opposite direction as shown in FIG. In the search in the opposite direction, the image acquisition is started from the position of M = 1, the image is acquired from the position of M = 8, the peak determination is started, and the differential value D at the position of M = 5 is the maximum value Dmax. It is determined that ΔDs and ΔDe are both larger than the threshold value Dth, the Z stage 40 is disposed at the position Hf corresponding to M = 5, and the focal point P1 of the Milo type interferometer 3 is set to the object 7. Was roughly matched to the surface.

  As described above, in the second embodiment, before the focusing is performed by the method of the first embodiment (first automatic focusing operation), the Z stage 40 and the imaging device 4 are controlled, and the Milo interferometer 3 is operated. Each image is photographed at a plurality of positions H while moving in the optical axis direction, a differential value D of each image is obtained, and Z is located at a position Hf corresponding to an image having the maximum differential value D among the plurality of images. By disposing the stage 40, the focal point P1 of the Milo type interferometer 3 is approximately matched with the surface of the object 7. Therefore, even when the focal point P1 cannot be adjusted only by the piezo stage 5, the focal point P1 of the mirrow interferometer 3 can be easily adjusted to the surface of the object 7, and the working efficiency can be improved.

  In the second embodiment, the object 7 is fixed and the Miro interferometer 3 is moved by the Z stage 40. However, the present invention is not limited to this, and the object 7 and the Miro interferometer 3 are relatively moved. As long as it is moved to, it may be moved by any method. For example, the mirrow interferometer 3 may be fixed and the object 7 may be moved, or both the mirrow interferometer 3 and the object 7 may be moved in opposite directions.

  In the second embodiment, the case where the millo type interferometer 3 is used has been described. However, the present invention is not limited to this, and other types of interferometers may be used. For example, a Michelson interferometer or a linique interferometer may be used.

[Configuration of coating device]
Finally, an outline of a coating apparatus will be described as an example of an apparatus to which the shape measuring apparatus according to the present embodiment is applied.

  FIG. 9 is a perspective view showing the overall configuration of coating apparatus 100 provided with the shape measuring apparatus according to the present embodiment. The coating apparatus 100 is configured to be able to apply a transparent ink (liquid material) over a plurality of layers on the main surface of the substrate 9. Referring to FIG. 9, a coating apparatus 100 includes a coating head unit that includes an observation optical system 2, a CCD camera 4, a cutting laser device 8, an ink coating mechanism 50, and an ink curing light source 20, and the coating head. Z stage 40 for moving the portion in the vertical direction (Z-axis direction) with respect to substrate 9 to be coated, X stage 42 for mounting Z stage 40 and moving in the X-axis direction, and Y for mounting substrate 9 An Y stage 44 that moves in the axial direction, a control computer 70 that controls the operation of the entire apparatus, a monitor 74 that displays an image taken by the CCD camera 4, and a command from the operator to the control computer 70 And an operation panel 72 for inputting.

  The observation optical system 2 includes a light source for illumination (the illumination device 1 in FIG. 1), and observes the surface state of the substrate 9 and the state of ink applied by the ink application mechanism 50. An image observed by the observation optical system 2 is converted into an electrical signal by the CCD camera 4 and displayed on the monitor 74. The cutting laser device 8 removes unnecessary portions on the substrate 9 by irradiating them with laser light via the observation optical system 2.

The ink application mechanism 50 applies ink onto the main surface of the substrate 9. The ink curing light source 20 includes, for example, a CO ₂ laser, and cures the ink applied by the ink application mechanism 50 by irradiating the laser beam.

  This apparatus configuration is an example. For example, the Z stage 40 on which the observation optical system 2 and the like are mounted is mounted on the X stage, the X stage is mounted on the Y stage, and the Z stage 40 can be moved in the XY directions. A configuration called a gantry system may be used, and any configuration may be used as long as the Z stage 40 on which the observation optical system 2 and the like are mounted can be moved relative to the target substrate 9 in the XY directions.

  Next, an example of the ink application mechanism 50 using a plurality of application needles will be described. FIG. 10 is a perspective view showing the main parts of the observation optical system 2 and the ink application mechanism 50. Referring to FIG. 10, this coating apparatus 100 includes a movable plate 15, a plurality (for example, five) objective lenses 19 having different magnifications, and a plurality (for example, five) for applying inks made of different materials. And a coating unit 17.

  The movable plate 15 is provided so as to be movable in the X-axis direction and the Y-axis direction between the lower end of the observation barrel 2a of the observation optical system 2 and the substrate 9. Further, for example, five through holes 15 a are formed in the movable plate 15.

  The objective lens 19 is fixed to the lower surface of the movable plate 15 so as to correspond to the through holes 15a at predetermined intervals in the Y-axis direction. Each of the five coating units 17 is disposed adjacent to the five objective lenses 19. By moving the movable plate 15, a desired coating unit 17 can be disposed above the target substrate 9.

  FIGS. 11A to 11C are views showing the main part from the direction A in FIG. 10 and showing the ink application operation. The application unit 17 includes an application needle 170 and an ink tank 172. First, as shown in FIG. 11A, the application needle 170 of the desired application unit 17 is positioned above the target substrate 9. At this time, the tip of the application needle 170 is immersed in the ink in the ink tank 172.

  Next, as shown in FIG. 11B, the application needle 170 is lowered and the tip of the application needle 170 protrudes from the bottom hole of the ink tank 172. At this time, ink adheres to the tip of the application needle 170. Next, as shown in FIG. 11C, the application needle 170 and the ink tank 172 are lowered to bring the tip of the application needle 170 into contact with the substrate 9, and ink is applied to the substrate 9. Thereafter, the state returns to the state of FIG.

  The ink application mechanism using a plurality of application needles is not described in detail because various other techniques are known. For example, it is shown in Patent Document 1. The application apparatus 100 can apply a desired ink of a plurality of inks by using a mechanism as shown in FIG. 10 as the ink application mechanism 50, for example, and can also apply a desired application of a plurality of application needles. The ink can be applied using a diameter application needle.

  Head unit 10 (FIG. 1) of the shape measuring apparatus according to the present embodiment is provided in observation optical system 2 of coating apparatus 100, for example. The control computer 70 controls the ink application mechanism 50 to perform the ink application operation, and then moves the Z stage 40 to position the head unit 10 at a predetermined position above the surface of the ink application part. Further, the control computer 70 takes an image of the interference light by the CCD camera 4 while moving the Z stage 40 relative to the substrate 9. The control computer 70 detects the Z stage position where the interference light intensity reaches a peak for each pixel, and calculates the film thickness of the ink application part or the height of the uneven part using the detected Z stage position.

[Description of ink application operation]
Next, details of the ink application operation performed by the application apparatus 100 will be described with reference to FIGS.

  The coating apparatus 100 moves the mirro interferometer 3 relative to the object using the Z stage 40, automatically detects the focus by the method shown in the first embodiment, and determines the detected focus position. Ink application operation is performed as a reference.

  Interference fringes generated by the Milo interferometer 3 appear when the surface to be detected is focused. Therefore, it is effective for focusing when a smooth surface having no irregularities such as a glass surface, a metal thin film, or a chromium film is used as a reference surface in the height direction of the coating operation. When the coating apparatus 100 is used in an electronic component mounting process or the like, a smooth surface such as a metal thin film may be selected as a reference surface in the height direction of the coating operation.

  Further, as shown in FIG. 5, since the peak width of the peak waveform of the separation degree is as small as several μm, the peak clearly appears, so that the focal position can be detected with high accuracy.

  Here, as shown in FIG. 12, an example of the operation in the case where the area AR on the surface of the metal thin film 91 on the substrate 9 is used as a reference plane in the height direction and ink is applied to the application part 92 will be described. Note that the metal thin film 91 and the coating portion 92 have the same height.

  An offset amount between the application unit 92 and the tip of the application needle 170 is obtained in advance and stored in the control computer 70 of the application apparatus 100. The offset amount is obtained as follows.

  As shown in FIG. 13, the control computer 70 focuses on the area AR set on the surface of the metal thin film 91 that is the reference plane by the method shown in the first embodiment. Specifically, a luminance histogram is obtained for the pixels in the area AR, the degree of separation R is calculated based on the luminance histogram, and the autofocus operation is executed.

  Next, the control computer 70 moves the movable plate 15 of the ink application mechanism 50 of the application apparatus 100 in the X-axis direction or the Y-axis direction in FIG. 10 and moves the application needle 170 above the application unit 92. Thereafter, as shown in FIG. 14, the control computer 70 lowers the Z stage 40 by Δz, then controls the ink application mechanism 50 to execute the application operation described in FIG. Return to the original position.

  The monitor 74 of the coating apparatus 100 is checked, and if ink is not applied to the coating unit 92, Δz is changed and the above procedure is executed again. This operation is repeated until ink is applied to the application section 92, and Δz when the ink is applied for the first time is stored in the control computer 70.

  In the actual coating operation, the method shown in the first embodiment is used to focus on the surface of the metal thin film 91 which is the reference surface, and then the movable plate 15 of the ink coating mechanism 50 of the coating apparatus 100 is moved to the X in FIG. Moving in the axial direction or the Y-axis direction, the application needle 170 is moved above the application unit 92. Thereafter, after the Z stage 40 is lowered by Δz, the ink application mechanism 50 is controlled to perform the application operation, and the movable plate 15 is returned to the original position.

  In the above description, the metal thin film 91 and the coating part 92 are described as having the same height. However, when the coating part 92 is higher than the metal thin film 91 as shown in FIG. The Z stage 40 is moved by the subtraction (Δz−Δd). In addition, as shown in FIG. 16, when the coating portion 92 is lower than the metal thin film 91, the Z stage 40 is moved by (Δz + Δd) where the step Δd is added to Δz. Here, the direction in which the Z stage 40 descends is positive.

[Description of film thickness inspection method]
After the ink is applied to the application part 92 by the above method, the film thickness of the applied ink is inspected. As a method for measuring the film thickness, for example, the surface shape can be measured using a method described in JP-A-2015-007564. As shown in FIG. 17, a step Δt between the metal thin film 91 and the apex portion of the applied ink 94 is obtained.

  When the obtained step Δt is smaller than the lower limit value TL stored in the control computer 70 of the coating apparatus 100 in advance, ink is applied again. At this time, if the thickness of the applied ink is Δt, the ink is applied with the offset amount of the Z stage 40 being (Δz−Δt). This operation is repeated until the ink film thickness Δt exceeds the lower limit TL. However, the number of times of application i is counted, and when i exceeds the maximum number N specified in advance, the application operation is interrupted.

  When the application operation is interrupted, the operator checks the state of the application unit 92 on the monitor 74 and determines whether or not the application has been executed correctly.

  FIG. 18 is a flowchart for explaining the film thickness inspection process executed by the control computer 70.

  Referring to FIG. 18, when execution of the coating operation is started, control computer 70 is predetermined in step (hereinafter, step is abbreviated as S) S100 as metal thin film 91 in FIG. The focus is adjusted with respect to the reference plane (FIG. 13). Based on the focal length to the reference surface at this time and the offset in the height direction between the objective lens 19 and the application needle 170 set in advance, the control computer 70 moves from the reference surface to the tip of the application needle 170. The height Δz is calculated.

  Thereafter, the control computer 70 moves the X stage 42 and the Y stage 44 so that the application needle 170 moves above the application unit 92.

  Next, in S110, the control computer 70 initializes a counter i indicating the number of times of application to i = 1 and advances the process to S120. In S120, the control computer 70 determines whether or not the counter i is equal to or less than a predetermined maximum number N.

  If counter i is equal to or less than the maximum number N (i ≦ N) (YES in S120), the process proceeds to S130, and control computer 70 lowers Z stage 40 by Δz and applies to application unit 92. Then, ink is applied (FIG. 14).

  Thereafter, the control computer 70 raises the Z stage 40 by Δz and returns it to the initial position, and further positions the objective lens 19 above the application portion 92. Then, in S140, the control computer 70 takes an image of interference light with the CCD camera 4 while moving the Z stage 40 relative to the substrate 9 in the height direction, and the interference light intensity reaches a peak. From the position of the Z stage 40, the height (film thickness) Δt from the reference surface of the apex portion of the applied ink is measured (FIG. 17).

  In S150, the control computer 70 determines whether or not the measured film thickness Δt of the ink portion is equal to or greater than a predetermined lower limit value TL (Δt ≧ TL).

  If the film thickness Δt is less than the lower limit value TL (NO in S150), the application amount is not sufficient. Therefore, the control computer 70 increments the counter i in S160, returns the process to S120, and applies again. Perform the action. At this time, the descending amount of the application needle 170 is corrected to (Δz−Δt).

  In the process of repeatedly executing the above-described coating operation, if the counter i exceeds the predetermined maximum number N (i> N) (NO in S120), the control computer 70 interrupts the coating operation. .

  Further, when the film thickness Δt of the ink portion is equal to or greater than the lower limit value TL (YES in S150), the control computer 70 ends the coating operation assuming that the coating is completed.

  As described above, the height of the applied ink can be accurately and efficiently measured by controlling the coating apparatus 100 according to the above process using the shape measuring apparatus according to the present embodiment. So work efficiency can be improved. In addition, by first performing the application operation after focusing on the reference surface, the positional relationship between the application needle and the application part is stabilized, so that the amount of ink adhering to the application part can be stabilized. .

  Furthermore, by measuring the film thickness after coating and repeatedly performing the coating operation until the film thickness exceeds a predetermined amount, product defects due to insufficient coating amount can be reduced. Moreover, since the trouble of repairing defective products can be omitted, the manufacturing tact can be improved.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Illumination device, 2 Observation optical system, 2a Observation barrel, 3 Milo type interferometer, 4 Imaging device, 5 Piezo stage, 6 Control apparatus, 7 Object, 8 Cutting laser apparatus, 9 Substrate, 10 Head part, 11 White light source, 12 filter, 15 movable plate, 15a through hole, 17 coating unit, 19, 31 objective lens, 20 light source for ink curing, 21 condenser lens, 22 half mirror, 23 imaging lens, 32 reflecting mirror, 33 half Mirror, 40 Z stage, 42 X stage, 44 Y stage, 50 ink application mechanism, 70 control computer, 72 operation panel, 74 monitor, 91 metal thin film, 92 application part, 94 ink, 100 application device, 170 application needle, 172 ink tank, A1-A3 optical axis.

Claims (9)

A shape measuring device for measuring the surface shape of an object,
The white light emitted from the illumination device is separated into first and second light fluxes, the surface of the object is irradiated with the first light flux, the reference light is irradiated with the second light flux, and the object An interferometer that synthesizes the reflected light from the surface of the light and the reflected light from the reference surface to generate an interference fringe corresponding to the surface shape of the object;
An observation optical system for observing the interference fringes;
An imaging device that captures an image of the interference fringes via the observation optical system;
A first positioning device that relatively moves the object and the interferometer in an optical axis direction;
A control device that controls the imaging device and the first positioning device, and performs a first auto-focusing operation for focusing the interferometer on the surface of the object;
In the first autofocus operation, the control device captures images at a plurality of relative positions while relatively moving the object and the interferometer in the optical axis direction, and each image is included in the image. A shape obtained by obtaining a degree of separation by a discriminant analysis method for a luminance distribution diagram of a plurality of pixels and arranging the object and the interferometer at a relative position corresponding to an image having the maximum degree of separation among a plurality of images measuring device.   In the discriminant analysis method, the luminance distribution diagrams of the plurality of pixels are separated into two classes by the luminance threshold value, and the luminance threshold value has the smallest intra-class variance and the largest inter-class variance. The shape measuring apparatus according to claim 1, wherein a ratio between the inter-class variance and the intra-class variance is set as the degree of separation. The interferometer is
An objective lens provided facing the surface of the object;
A semi-transparent mirror provided between the objective lens and the surface of the object;
A mirror type interferometer including a reflecting mirror having the reference surface provided at the center of the objective lens facing the semi-transparent mirror,
White light emitted from the illumination device is refracted by the objective lens, is incident on the semi-transparent mirror, and is separated into the first light beam that has passed through the semi-transparent mirror and the second light beam that has been reflected by the semi-transparent mirror. And
The surface of the object is irradiated with the first light beam and the second light beam is irradiated on the reference surface, and the reflected light from the surface of the object and the reflected light from the reference surface are half of the light. The interference light is synthesized by a mirror, and the interference fringes are generated by the interference light.
The shape measuring apparatus according to claim 1, wherein an optical axis and a focal point of the Millo interferometer are an optical axis and a focal point of the objective lens, respectively. And a second positioning device for moving the interferometer relative to the object in the optical axis direction.
The stroke of the second positioning device is larger than the stroke of the first positioning device;
The controller is
Before performing the first autofocus operation, execute a second autofocus operation for controlling the imaging device and the second positioning device to roughly adjust the focus position of the interferometer,
In the second auto-focus operation, each image is captured at a plurality of relative positions while the object and the interferometer are relatively moved in the optical axis direction, and a plurality of pixels included in the image are captured for each image. The differential value of brightness | luminance is calculated | required, The said target object and the said interferometer are arrange | positioned in the relative position corresponding to the image from which the said differential value becomes the maximum among several images. The shape measuring device described in 1. The first positioning device is fixed to the observation optical system and moves the interferometer,
At least the first positioning device, the observation optical system, and the interferometer constitute one optical unit,
The shape measuring apparatus according to claim 4, wherein the second positioning device moves the optical unit. An application device for applying a liquid material to the surface of an object,
An application unit that has an application needle and applies a liquid material attached to the tip of the application needle to the surface of the object;
The white light emitted from the illumination device is separated into first and second light fluxes, the surface of the object is irradiated with the first light flux, the reference light is irradiated with the second light flux, and the object An interferometer that synthesizes the reflected light from the surface and the reflected light from the reference surface to generate an interference fringe corresponding to the surface shape of the object, and an observation optical system for observing the interference fringe, A head unit configured to include an imaging device that captures an image of the interference fringes via the observation optical system, and a first positioning device that relatively moves the object and the interferometer in the optical axis direction;
A second positioning device that relatively moves the head unit and the object in a direction perpendicular to the optical axis direction to position the head unit at a desired position above the surface of the object;
A control device that controls the imaging device and the first and second positioning devices, and performs a first autofocus operation for focusing the interferometer on the surface of the object;
In the first autofocus operation, the control device captures a plurality of images at a plurality of relative positions while relatively moving the object and the interferometer in the optical axis direction, and each image is displayed on the image. A degree of separation is obtained by a discriminant analysis method for a luminance distribution diagram of a plurality of pixels included, and the object and the interferometer are arranged at a relative position corresponding to an image having the maximum degree of separation among the plurality of images. Application equipment.   The said control apparatus apply | coats the said liquid material to the surface of the said object with the said applicator needle, after focusing on the reference plane set on the said object in the said 1st autofocus operation | movement. The coating apparatus as described in.   The controller, after applying the liquid material, obtains a step between the reference surface and the apex of the applied liquid material, and repeats the application operation until the obtained step exceeds a preset lower limit value. Item 8. The coating apparatus according to Item 7. The stroke of the second positioning device is larger than the stroke of the first positioning device,
The controller is
Before performing the first autofocus operation, execute a second autofocus operation for controlling the imaging device and the second positioning device to roughly adjust the focus position of the interferometer,
In the second auto-focus operation, each image is captured at a plurality of relative positions while the object and the interferometer are relatively moved in the optical axis direction, and a plurality of pixels included in the image are captured for each image. The differential value of brightness | luminance is calculated | required and the said target object and the said interferometer are arrange | positioned in the relative position corresponding to the image from which the said differential value becomes the maximum among several images. The coating apparatus as described in.

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