JP4829055B2 - Minute height measuring method and minute height measuring apparatus - Google Patents

Description

  The present invention relates to a minute height measuring method for measuring unevenness on an object to be measured, and more specifically, a minute height measuring method and minute height measurement capable of reducing the time required to measure the unevenness on an object to be measured. It concerns the device.

Conventional minute height measuring devices measure the height of protrusions, foreign objects, etc. on a substrate by scanning with the measuring needle in contact with the substrate surface, and the tip shape of the measuring needle is in the scanning direction. The shape has a flat straight portion perpendicular to each other, and a minute height can be measured by one scan (see, for example, Patent Document 1).
JP-A-10-68618

  However, in such a conventional minute height measuring apparatus, the measuring needle is scanned within a predetermined scanning range to measure a continuous height change on a certain straight line. Measurement time is required only for the scanning time of the measuring needle within the range, and the height of protrusions and foreign matter on the object to be measured cannot be measured in a short time.

  Accordingly, the present invention aims to provide a micro height measuring method and a micro height measuring apparatus capable of addressing such problems and reducing the time required to measure the unevenness on the object to be measured. To do.

In order to achieve the above object, a minute height measuring method according to a first invention includes a step of projecting thin line-shaped projection light onto a predetermined measurement position on an object to be measured by an objective lens, and the objective lens or the object to be measured. Imaging a plurality of images of the projection light on the object to be measured through the objective lens while changing the height of the object in the optical axis direction of the objective lens; and In the image, for each of a plurality of measurement areas divided and set in a direction intersecting with the length direction of the projection light, in the length direction of the projection light at a plurality of measurement points designated in advance in each measurement area The steps of calculating the magnitude of the luminance gradient in the intersecting direction and summing them in the measurement area to measure the contrast, and the height of the objective lens or object to be measured showing the maximum contrast for each measurement area Extract the amount of change , And performs determining a height profile along the projection light on the object to be measured based on the amount of change in the height-and.

With such a configuration, the objective lens projects a thin line-shaped projection light on a predetermined measurement position on the object to be measured, and changes the height of the object lens or the object to be measured in the direction of the optical axis of the object lens. A plurality of measurement areas obtained by capturing a plurality of images of the projection light on the object to be measured via the lens, and divided and set in a direction intersecting the length direction of the projection light in each of the captured projection light images Each time, the magnitude of the luminance gradient in the direction intersecting the length direction of the projection light at a plurality of measurement points specified in advance in each measurement area is calculated, and these are summed in the measurement area to contrast. The amount of change in the height of the objective lens or the object to be measured showing the maximum contrast for each measurement region is extracted, and the height along the projection light on the object to be measured is determined based on the amount of change in the height. Find the height distribution.

  The projection light on the object to be measured is light that has passed through the slit. Thereby, a thin line-shaped projection light is generated by the light passing through the slit on the object to be measured.

According to a second aspect of the present invention, there is provided a micro-height measuring apparatus, wherein a microscope capable of projecting a thin line-shaped projection light onto a predetermined measurement position on the object to be measured by an objective lens, and the height of the microscope or the object to be measured Displacement means for changing in the optical axis direction of the objective lens and an optically conjugate relationship with the imaging point of the objective lens, and a plurality of projection light beams on the object to be measured via the objective lens A plurality of image pickup means for picking up an image, and a plurality of divisional controls in the direction intersecting the length direction of the projection light in each image of the projection light picked up by the image pickup means while controlling the driving of the displacement means For each of the measurement areas, the magnitude of the brightness gradient in the direction intersecting the length direction of the projection light at each of the plurality of measurement points specified in advance in each measurement area is calculated and summed in the measurement area. and measuring the contrast, the measurement region for each Control means for extracting a height change amount of the microscope or the object to be measured showing the maximum contrast, and obtaining a height distribution along the projection light on the object to be measured based on the height change amount; , With.

With such a configuration, the projection light in the form of a thin line is projected at a predetermined measurement position on the object to be measured by the objective lens in the microscope, the drive of the displacement means is controlled by the control means, and the microscope or the object to be measured is controlled by the displacement means. A plurality of pieces of projection light on the object to be measured via the objective lens by the imaging means arranged in an optically conjugate relationship with the imaging point of the objective lens by changing the height in the optical axis direction of the objective lens For each of a plurality of measurement areas divided and set in a direction intersecting the length direction of the projection light in each image of the projection light imaged by the imaging means by the control means . The brightness gradient in the direction intersecting the length direction of the projection light at a plurality of measurement points specified in advance is calculated, and the sum is calculated in the measurement area to measure the contrast. Of the microscope or object under test showing the maximum contrast Extracting the amount of change, determine the height distribution along the projection light on the object to be measured based on the amount of change in the height-.

  Furthermore, the image of the projection light on the object to be measured is light that has passed through the slit. Thereby, a thin line-shaped projection light is generated by the light passing through the slit on the object to be measured.

According to the minute height measuring method according to claim 1, for each of a plurality of measurement areas divided and set in a direction intersecting with the length direction of the thin line-shaped projection light, a plurality of pre-designated values in each measurement area The brightness gradients in the direction intersecting the length direction of the projection light at the measurement points were calculated and summed in the measurement area to measure the contrast, and the maximum contrast was shown for each measurement area. Since the amount of change in the height of the objective lens or the object to be measured is extracted, the height distribution along the projection light on the object to be measured is obtained based on the amount of change in the height. The time required to measure the unevenness of the contact point is almost determined by the electrical processing time, and can be significantly shortened from the measurement time determined by the physical movement speed of the conventional contact needle. Further, the contrast can be appropriately calculated even when the position of the projection light is slightly shifted or the blur of the projection light becomes larger than expected. Therefore, the measurement of the minute height can be surely executed.

According to a third aspect of the present invention, there is provided the minute height measuring apparatus according to the present invention, for each of the plurality of measurement areas divided and set in the direction intersecting the length direction of the thin line-shaped projection light by the control means. The brightness gradient in the direction intersecting the length direction of the projection light at each of the plurality of measurement points is calculated and summed in the measurement area to measure the contrast, and the maximum contrast for each measurement area The amount of change in the height of the microscope or object to be measured is extracted, and the height distribution along the projection light on the object to be measured is obtained based on the amount of change in the height. The time required to measure the unevenness on the object is almost determined by the electrical processing time, and can be significantly shortened from the measurement time determined by the physical movement speed of the conventional contact needle. Further, the contrast can be appropriately calculated even when the position of the projection light is slightly shifted or the blur of the projection light becomes larger than expected. Therefore, the measurement of the minute height can be surely executed.

Furthermore, according to the invention which concerns on Claim 2 or 4 , a thin line-shaped projection light can be produced | generated easily. In particular, in the minute height measuring apparatus, the light passing through the slit of the slit plate is projected onto the object to be measured to generate the projection light, so that the optical configuration is simplified. Therefore, an inexpensive device can be provided.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing an embodiment of a minute height measuring apparatus according to the present invention. This minute height measuring apparatus measures unevenness on an object to be measured, and includes a microscope 1, a displacement means 2, an imaging means 3, and a control means 4. In the following description, the case of measuring the height of the protrusion on the object to be measured will be described.

  The microscope 1 has a function of allowing observation on the object 5 to be measured and projecting a thin line-shaped projection light 15 onto a predetermined measurement position on the object 5 to be measured, for example, a projection, The objective lens 6, the light source 7, the slit plate 8, and the imaging lens 9 are provided.

    The objective lens 6 collects light on the object to be measured 5. A light source 7 is provided above the objective lens 6. The light source 7 emits light including visible light. Here, for example, when ultraviolet light, infrared light, or light of a specific wavelength is used as light for height measurement, a filter that selectively transmits light of a predetermined wavelength is provided in front of the light emission direction so that it can be inserted and removed. It is done. Further, a slit plate 8 is provided between the objective lens 6 and the light source 7 at a position having a conjugate relationship with the image forming point of the objective lens 6. This slit plate 8 forms thin line-shaped projection light 15 (see FIG. 5), and a slit 10 for limiting the amount of light passing is formed in the center of an opaque member as shown in FIG. Yes. An imaging lens 9 is provided between the objective lens 6 and the slit plate 8. The imaging lens 9 constitutes an imaging optical system that forms an image of the slit 10 of the slit plate 8 on the object 5 together with the objective lens 6.

  Displacement means 2 is provided on the side of the microscope 1. This displacement means 2 changes the height of the microscope 1 in the direction of the optical axis of the objective lens 6 indicated by arrows A and B, and moves the microscope 1 up and down, for example, a drive unit 11 such as a pulse motor, and the microscope 1. And a guide portion 12 for guiding in the vertical direction. The lower end portion of the guide portion 12 is fixed to the base member 13.

  On the optical path branched from the objective lens 6 of the microscope 1 toward the slit plate 8 by the half mirror 14, the imaging means 3 is located at a position optically conjugate with the imaging point of the objective lens 6. Is provided. The image pickup means 3 picks up a plurality of images of the projection light 15 on the object to be measured 5 through the objective lens 6, for example from a CCD image pickup device 16 having a large number of pixels arranged in two dimensions. It has become. In FIG. 1, reference numeral 17 denotes an imaging lens that forms an image of the projection light 15 on the DUT 5 on the light receiving surface 16 a of the CCD image sensor 16.

Control means 4 is connected to the displacement means 2 and the imaging means 3. The control means 4 controls the driving of the displacement means 2 and changes in the height of the microscope 1 that shows the maximum contrast for each measurement region 18 ₁ to 18 _n (see FIG. 5B) (amount of increase). ) And a height distribution along the projection light 15 on the object to be measured 5 is obtained based on the amount of change in height (amount of increase), and the maximum value in the height distribution and a predetermined reference value The height of the protrusion is calculated from the difference. As shown in FIG. 3, a host computer (hereinafter referred to as “control PC”) 17, a control and processing unit 20, an A / D conversion unit 21, And a memory 22.

The control PC 19 is configured such that the number of divisions of the plurality of measurement regions 18 ₁ to 18 _n set by the operator being divided in the length direction by a line intersecting with the thin line-shaped projection light 15, or once for the microscope 1. Various parameters such as the increase amount of image data and the number of times of image data acquisition (number of captured images) can be input, and are output in association with each other from the control and processing unit 20 described later for each of the measurement regions 18 ₁ to 18 _n. The projected light 15 on the object to be measured 5 corresponding to each of the measurement regions 18 ₁ to 18 _n is an increase amount indicating the maximum contrast for each of the measurement regions 18 ₁ to 18 _n based on the data of the contrast and the amount of increase of the microscope 1. Is obtained as the height of the projected portion, and the height distribution along the projection light 15 on the object to be measured 5 is obtained based on the height, and the projection is determined from the difference between the maximum value in the height distribution and a predetermined reference value. High And calculates a, and causes a display section to display the results. When the number of divisions of the measurement areas 18 ₁ to 18 _n is set, the plurality of pixels 23 of the CCD image sensor 16 corresponding to the measurement areas 18 ₁ to 18 _n are measured with contrast measurement points (X _n0 , Y _n0). ) To (X _nk , Y _nm ) (see FIG. 6), and the address information of the pixel 23 is output to the control and processing unit 20. The coordinates of each measurement point are shown by setting the X axis as an axis parallel to the length direction of the projection light 15 and the Y axis as an axis perpendicular to the length direction of the projection light 15. Further, the width in the X-axis direction of the measurement regions 18 ₁ to 18 _n may be the entire width in the same direction of the CCD image pickup device 16, or a predetermined width set in the vicinity thereof including the projection light 15. May be.

The control and processing unit 20 measures the contrast for each of the plurality of measurement regions 18 ₁ to 18 _n that are divided and set in the direction intersecting the length direction of the projection light 15. a plurality of measurement points specified in advance in the _{n (X n0, Y n0)} ~ (X nk, Y nm) in the direction of brightness gradient perpendicular to the length direction of the projection light 15 for each size were calculated, respectively The luminance gradients at the respective measurement points (X _n0 , Y _n0 ) to (X _nk , Y _nm ) are summed within the measurement region 18 _n , so that the direction perpendicular to the length direction of the projection light 15 is obtained. The magnitude of the luminance gradient is obtained, and this is calculated as the contrast. Further, a command signal relating to the preset number of times of image data acquisition and the amount of increase of the microscope 1 per one time is sent to the displacing means 2, and the microscope 1 is raised by the amount of increase a predetermined number of times. Further, a conversion timing signal for activating the A / D conversion unit 21 is output to the A / D conversion unit 21 for a predetermined number of times of image acquisition at a predetermined timing. Furthermore, the contrast of each of the measurement areas 18 ₁ to 18 _n and the rising amount data of the microscope 1 input from the displacement means 2 are associated with each other and written in the memory 22. Then, and it outputs the all contrast and increased amount data of the microscope 1 associated with it for each measurement region 18 ₁ ~ 18 _n read out from the memory 22 to the control PC 19.

The A / D conversion unit 21 converts the analog signal input from the imaging unit 3 into digital data, and performs digital conversion at a predetermined timing based on the conversion timing signal input from the control and processing unit 20. It is like that. The memory 22 stores various parameters input by the control PC 19, and stores the measured contrast and the amount of increase data of the microscope 1 in association with each measurement region 18 ₁ to 18 _n. For example, a rewritable semiconductor memory.

Next, a minute height measuring method performed using the minute height measuring apparatus configured as described above will be described with reference to the flowchart of FIG.
First, in step S1, parameters such as the number of divisions of the measurement areas 18 ₁ to 18 _n , the amount of increase per microscope 1 and the number of times image data is acquired are input by the control PC 19 and initial settings are made. The

  In step S2, an illumination light source (not shown) is turned on, and, for example, while looking at an image taken by the imaging means 3 displayed on the display unit of the control PC 19, as shown in FIG. The projection light 15 is aligned with the projection 22 of the above.

  In step S3, height measurement is started by operating a measurement start switch (not shown), and the process proceeds to step S4. At this time, the illumination means is turned off.

  In step S4, a conversion timing signal is output from the control and processing unit 20 of the control unit 4 to the A / D conversion unit 21 to drive the A / D conversion unit 21 for a predetermined time, and the measurement target imaged by the imaging unit 3 is measured. The image of the projection light 15 on the object 5 is A / D converted to acquire the first image data. At this time, the number of times image data is acquired is counted.

In step S5, the contrast is measured for each of a plurality of preset measurement areas 18 ₁ to 18 _n as shown in FIG. 5B based on the acquired image data. Specifically, as shown in FIG. 6, for example , the length of the projection light 15 at each of a plurality of measurement points (X _n0 , Y _n0 ) to (X _nk , Y _nm ) designated in advance in the measurement region 18 _n . It is to calculate the magnitude of the direction of the brightness gradient perpendicular to the direction, and the sum surveying a fixed point _{(X n0, Y n0) ~} (X nk, Y nm) the magnitude of the luminance gradient in the above measurement region 18 in the _n To calculate the contrast. Then, the contrast calculated for each of the measurement regions 18 ₁ to 18 _n is stored in the memory 22 in association with the rising amount data of the microscope 1 (in this case, for example, zero). Note that the contrast calculation can be executed by, for example, the following calculation formula. Here, C is the contrast of each measurement region 18 ₁ to 18 _n , B is the luminance (detection output) detected by each pixel 23, n is the number of the measurement region 18 ₁ to 18 _n , and (X _n0 , Y _n0 ). ˜ (X _nk , Y _nm ) indicates the measurement range of the n-th measurement region 18 _n .

In step S6, the control and processing unit 20 determines whether or not the contrast measurement for all the measurement regions 18 ₁ to 18 _n has been completed. That is, the division number of the measurement areas 18 ₁ to 18 _n read from the memory 22 is compared with the number n of the current measurement area 18 _n to determine whether or not they match. In this case, when the two do not match and the measurement of contrast for all the measurement regions 18 ₁ to 18 _n has not been completed yet, the determination is “NO” and the process returns to step S5, and the second is based on the acquired image data. the measurement region 18 _second measurement of contrast for is executed. Thereafter, steps S5 and S6 are repeatedly executed until the contrast measurement for the _nth measurement region 18n is completed. Then, when the contrast measurement for all the measurement regions 18 ₁ to 18 _n is completed and the determination is “YES”, the process proceeds to step S7.

  In step S7, the control and processing unit 20 determines whether or not the number of acquisitions of the image data counted in step S4 has reached a predetermined number. That is, the number of acquisitions of the image data read from the memory 22 is compared with the number of acquisitions of the image data counted in step S4 to determine whether or not they match. In this case, when the number of times of image data acquisition has not yet reached the predetermined number, “NO” determination is made, and the process proceeds to step S8.

  In step S8, a command signal is sent from the control and processing unit 20 to the displacing means 2 based on the setting data of the amount of increase per time of the microscope 1 read from the memory 22, and the microscope 1 is sent by a predetermined amount, for example, FIG. Is raised in the direction of arrow A shown in FIG. Then, returning to step S4, steps S4 to S8 are executed again. Thereafter, in step S7, steps S4 to S8 are repeatedly executed until the predetermined number of image acquisition times reaches “YES”, and if “YES” is determined, the process proceeds to step S9.

In step S9, all the contrasts stored in the memory 22 in association with the ascent data of the microscope 1 are read out and sent to the control PC 19. The control PC 19 analyzes all the input contrasts, obtains the height of the microscope 1 from the amount of increase data indicating the maximum contrast for each of the measurement regions 18 ₁ to 18 _n , and determines the height of the microscope 1 as the measurement region 18. ₁ ~ 18 _n projected light 15 on the object to be measured 5 corresponding to is calculated as the height of the projected portion, obtains the height distribution along the projection light 15 on the object to be measured 5 on the basis of them.

In step S10, the difference between the maximum value in the height distribution and a predetermined reference value is calculated, and this is displayed on the display unit as the height of the projection 24 to be measured. Further, the height distribution of the measurement positions on the object to be measured 5 may be displayed in a graph corresponding to the measurement regions 18 ₁ to 18 _n . Furthermore, a printer may be connected to the control PC 19 to print out the height measurement result.

  In the above embodiment, the case where the height of the protrusion 24 on the object to be measured 5 is measured has been described. However, the present invention is not limited to this, and the height along the projection light 15 on the object to be measured 5. Unevenness on the surface of the DUT 5 can also be measured from the distribution. In this case, if a predetermined reference value is set in the height distribution, the unevenness with respect to the reference value can be measured. The reference value can be arbitrarily selected from, for example, an average value in a height distribution, a center of gravity, a mode value, a value to be fitted to a straight line, a minimum value, a maximum value, or a height at a specified position. .

  Moreover, although the case where an operator inputs and sets various parameters has been described in the above embodiment, the present invention is not limited to this, and predetermined values for various parameters may be automatically set.

  Furthermore, in the above-described embodiment, the case where the two-dimensional CCD image pickup device 16 is used as the image pickup means 3 has been described. However, the present invention is not limited to this, and a line CCD is disposed orthogonal to the projection light 15. It may be. In this case, if a one-dimensional image is acquired at a predetermined timing while scanning the line CCD in a direction parallel to the projection light 15, and the acquired plurality of one-dimensional images are respectively stored, the plurality of one-dimensional images are stored. To obtain a two-dimensional image. Therefore, if the same processing as described above is performed using this two-dimensional image, the minute height along the projection light 15 on the object to be measured 5 can be measured. The imaging device is not limited to the CCD, and may be a CMOS or another imaging device.

In the above description, the plurality of measurement points (X _n0 , Y _n0 ) to (X _nk , Y _nm ) designated in advance in the measurement regions 18 ₁ to 18 _n are orthogonal to the length direction of the projection light 15. calculating the magnitude of the direction of the brightness gradient, respective measurement point _{(X n0, Y n0) ~} (X nk, Y nm) projection light by the magnitude of the luminance gradient in summing in the measurement region 18 in the _n The case where the magnitude of the luminance gradient in the direction orthogonal to the length direction of 15 is obtained and this is used as the contrast has been described. However, the present invention is not limited to this, and the contrast is included in each of the measurement regions 18 ₁ to 18 _n . It may be measured by any method as long as it calculates the magnitude of the luminance gradient at a plurality of measurement points specified in advance and sums them up within the measurement area, and it is simply a bright part and a dark part. And the luminance difference. Alternatively, the contrast may be represented by the brightness value of the projected light to be imaged. In this case, the measurement of the minute height may be performed based on the luminance change of the projection light corresponding to each measurement region.

  In the above description, the case where the projection light 15 is obtained by projecting light that has passed through one slit 10 formed on the slit plate 8 has been described. However, the present invention is not limited to this, and the projection light 15 is not limited thereto. May be light that has passed through a plurality of slits 10, may have a pattern shape having a predetermined width, and may be generated by scanning a beam spot at high speed. .

  In the above description, the case where the slit plate 8 is disposed at a position conjugated with the imaging point of the objective lens 6 has been described. However, the present invention is not limited to this, and the slit plate 8 is placed on the object to be measured 5. The slit plate 8 may be disposed at any position as long as the thin line-shaped projection light 15 is obtained by the light passing through the slit 10.

It is a conceptual diagram which shows embodiment of the micro height measuring apparatus by this invention. It is a top view which shows one structural example of the slit plate used for the said micro height measuring apparatus. It is a block diagram which shows one structural example of the control means of the said micro height measurement apparatus. It is a flowchart explaining the minute height measuring method performed using the said minute height measuring apparatus. It is explanatory drawing shown about minute height measurement, (a) shows the state by which the projection light was projected with respect to protrusion, (b) has shown the several measurement area | region divided and set along the projection light. . It is explanatory drawing shown about the measurement of the contrast in the said measurement area | region.

Explanation of symbols

1 ... microscope 2 ... displacement means 3 ... imaging unit 4 ... control unit 5 ... DUT 6 ... objective lens 8 ... slit plate 10 ... slit 15 ... projected light 18 ₁ ~ 18 n _... measured region 23 ... pixel

Claims (4)

Projecting thin line-shaped projection light onto a predetermined measurement position on the object to be measured by the objective lens;
Capturing a plurality of images of the projection light on the object to be measured through the objective lens while changing the height of the object lens or the object to be measured in the optical axis direction of the objective lens;
For each of a plurality of measurement areas divided and set in a direction crossing the length direction of the projection light in each image of the captured projection light , a plurality of measurement points designated in advance in each measurement area Calculating the magnitude of the luminance gradient in the direction intersecting the length direction of the projection light, and summing them in the measurement region to measure the contrast;
The amount of change in the height of the objective lens or the object to be measured showing the maximum contrast for each measurement region is extracted, and the height along the projection light on the object to be measured based on the amount of change in the height Obtaining a distribution;
A method for measuring a minute height, characterized in that   2. The minute height measuring method according to claim 1, wherein the projection light on the object to be measured is light that has passed through a slit. A microscope capable of projecting thin line-shaped projection light onto a predetermined measurement position on the object to be measured by an objective lens;
Displacement means for changing the height of the microscope or the object to be measured in the optical axis direction of the objective lens,
An imaging means that is disposed in an optically conjugate relationship with the imaging point of the objective lens and that captures a plurality of images of projection light on the object to be measured via the objective lens;
Controlling the driving of the displacement means, and for each of a plurality of measurement areas divided and set in the direction intersecting the length direction of the projection light in each image of the projection light imaged by the imaging means , Calculate the magnitude of the luminance gradient in the direction intersecting the length direction of the projection light at a plurality of measurement points specified in advance in the measurement area, and sum the measurements in the measurement area to measure the contrast, The amount of change in the height of the microscope or the object to be measured showing the maximum contrast for each measurement region is extracted, and the height distribution along the projection light on the object to be measured is calculated based on the amount of change in the height. The required control means,
A minute height measuring device characterized by comprising: 4. The minute height measuring apparatus according to claim 3, wherein the projection light on the object to be measured is light that has passed through a slit.

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