JP2007187623A - Method and apparatus for measuring three-dimensional shape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of shortening the measuring time by reducing the time required for initial adjustments by an automatic-focusing constitution as much as possible. <P>SOLUTION: White light is made incident onto a beam splitter 5 via an object lens 4 and branched to a reference optical path on the side of a reflecting mirror 6 and a measuring optical path on the side of an object to be measured. An optical path length changing means 8 changes the optical path length of the measuring optical path, and a camera 10 images interference light. By determining an optical path length in which interferences occur on the basis of image data, the shape of the object to be measured is measured in an three-dimensional shape measuring apparatus. Measuring light from a light source 12 for light projection is introduced to the same optical path as the optical path of the white light by a mirror 25, and the camera 10 images the measuring light returned from the object to be measured via the object lens 4. A Z-axis control means 20 moves a head 11 on the basis of output of the camera 10 in such a way that the distance between the object lens 4 and the object to be measured is located at the focal distance of the object lens 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a three-dimensional shape measuring apparatus that three-dimensionally measures the shape of an object to be measured using an interference phenomenon caused by broadband light (for example, white light) including a plurality of spectrums (hereinafter, described with wavelengths). In particular, one of the broadband light is incident on a reference optical path having a reference mirror at the far end, and the other of the broadband light is incident on a measurement optical path having an object to be measured at the far end, and each return light from the reference mirror and the object to be measured. In the interferometer (interferometer) that causes interference by the optical path length of either the reference optical path or the measurement optical path by changing the predetermined range, the shape of the object to be measured is determined based on the optical path length generated by the interference fringes. This is a shape measuring device that measures, and adjusts the initial position of the object to be measured or the reference mirror so that the change range of the optical path length becomes effective when irradiating the object to be measured with the objective lens through the measurement optical path by the objective lens. It relates to the technology that can.

  In general, the objective lens is used for irradiating the object to be measured. And before a to-be-measured object is set and it measures, the distance between the objective lens and to-be-measured object is adjusted so that it may correspond to the focal distance of an objective lens, for example. When the focal length is mechanically adjusted, until now, the focal position has often been confirmed by visual observation or image processing with an imaging lens + camera or the like.

  In the field of three-dimensional shape measurement using the interference section, there is a technique of Patent Document 1 as a technique using an objective lens. Although there is a description dealing with an autofocus device in the detailed description of Patent Document 1, this autofocus device is not intended for autofocusing of an objective lens, and measures substrate height and warpage. In other words, the relative position information obtained by interference measurement is used to correct the influence of unevenness due to substrate warpage using the measurement results obtained by the autofocus device, and the absolute value of the distance from the substrate to the bump apex is calculated. Yes. Therefore, the configuration diagram attached to Patent Document 1 and the description thereof do not move in the direction parallel to the optical axis based on the measurement result of the autofocus device. That is, a technique for adjusting the distance between the objective lens and the object to be measured and the focal length is not disclosed.

  The focus detection circuit is also arranged in the drawing for explaining the prior art of Patent Document 2, but this is probably due to the optical path length from the observation plane to the reference plane and the optical path length from the observation plane to the measurement target plane. The position where the difference becomes zero is detected, and there is no explanation about adjusting the focal length.

JP 2000-310518 A JP 2000-2221013 A

  When using an interferometer to change the optical path length of the interferometer to measure a very small displacement of the surface of the object to be measured, the distance between the objective lens on the interferometer side and the object to be measured is set to an appropriate position. Otherwise, there is a possibility that a predetermined range of the optical path length to be changed in order to make the interference fringe appear (so-called dynamic range for making the interference fringe appear) cannot be secured.

  In other words, interference fringes occur when the reference optical path and the measurement optical path coincide with each other, so that it is necessary to fix the other optical path length and change the one optical path length to detect the coincidence. Therefore, for example, if one of the optical path lengths is set as the optical path length of the measurement optical path (or the reference optical path may be used), the optical path length before changing the optical path length of the measurement optical path is obtained when the predetermined range is changed. It must be in a position that is expected to coincide with the reference light path. Hereinafter, this position is referred to as “target position”, and the distance from the fixed specific means to this position is referred to as “target distance”. For example, this specific means can be an objective lens. Furthermore, the focal length of the objective lens can be set as a target distance.

  Since this target distance is related to the position of the object to be measured, position adjustment is required every time the object to be measured is changed. Therefore, adjustment of the target distance, for example, adjustment of the distance between the objective lens and the object to be measured is important and is performed carefully. For example, when the optical path length is changed by 500 points at intervals of several tens of nm, the change range is several tens of μm. Therefore, if the distance between the objective lens and the object to be measured matches the target distance (focal length) at the initial position before changing the optical path length, a dynamic range of several tens of μm can be used as it is. If the distance between the object and the object to be measured deviates from the target distance (focal length), the distance corresponding to the deviation may affect the dynamic range and become narrower. If the change in the displacement of the surface of the object to be measured is large, or if the object to be measured is plate-shaped and warped, the dynamic range may be reduced by that amount (that is, the effective range for changing the optical path length). Becomes narrower). In the worst case, interference fringes may not appear even if the optical path length is changed. In that case, it is necessary to reset the position of the object to be measured and to widen the range of change of the optical path length.

  Therefore, if the focal length was dealt with by visual adjustment or complex image processing at the initial stage of measurement, it took too much time to adjust, and it was not possible to cope with the magnitude of the displacement of the object to be measured and the warp of the object to be measured. There was a problem such as.

  An object of the present invention is to secure an effective optical path length change range (dynamic range) by automatically adjusting the position of the object to be measured to the target position (focal position of the objective lens), for example. The purpose is to provide a technique capable of shortening the initial adjustment time as much as possible and speeding up the measurement time.

  To achieve an effective optical path length change range, which is the above objective, when the optical path length is changed by the change range, the optical path length of the measurement optical path and the optical path length of the reference optical path may coincide. As described above, the setting position of the object to be measured can be automatically adjusted at the initial stage before the shape measurement. For example, when the object to be measured is replaced for measurement, depending on the “position of the object to be measured in the direction of the measurement optical path” at that time, the optical path length of the reference optical path is changed at the initial time before the change of the optical path length. The optical path length of the measurement optical path may change. Therefore, even when the object to be measured is replaced, an adjustment for keeping the “optical path length of the initial measurement optical path relative to the optical path length of the reference optical path” constant (its position or distance is the “target position (target distance)”). It is. The “target position (target distance)” is a position (distance) at which an effective optical path length variable range (dynamic range) can be secured. If the optical system that branches into the reference optical path and the measurement optical path is fixedly disposed on the head, for example, and the optical path length of the reference optical path is fixed, the distance between the head and the object to be measured can be adjusted to the target distance. Yes. If an objective lens is disposed on the head, the distance between the objective lens and the object to be measured may be adjusted to match a target distance (for example, the focal length of the objective lens). All of the above items have the same technical significance.

To achieve the above object, the invention described in claim 1 includes a broadband light source (1) for outputting broadband light having a broadband spectrum, a reference optical path for irradiating the reference mirror with the broadband light, and a device under test. An optical path forming unit (5) for branching into a measurement optical path to irradiate a desired measurement range, and combining and outputting the reflected light from the reference mirror and the object to be measured, the broadband light source, and the optical path forming unit, An objective lens (4) that is provided between or in the measurement optical path and irradiates the measurement range of the surface of the object to be measured with the broadband light, and the reference optical path or the measurement optical path An optical path length varying means (8) for changing one of the optical path lengths over a predetermined range, and an imaging means for imaging the output of the optical path forming unit corresponding to the measurement range according to the change of the optical path length ( 10), and the imaging means In the three-dimensional shape measuring apparatus for measuring the shape on the basis of the interference fringe obtained from the output,
A position detector (16) for irradiating the object to be measured with position detection light in the initial stage of measuring the shape and detecting the distance between the head and the object to be measured based on the reflected light from the object to be measured. When,
The reference optical path or the measurement so that the interference fringes are obtained when the optical path length is changed over the predetermined range based on the distance between the head and the object to be measured output from the position detection unit. And means (20, 22) for adjusting the initial optical path length of the optical path.

According to a second aspect of the present invention, the optical path length of the illumination path in the invention of the first aspect is fixed, and the optical path length of the measurement optical path is changed when the optical path length is changed over the predetermined range in advance. The distance between the head and the object to be measured, which can change beyond the fixed length, is set in advance as a target distance,
The means for adjusting the initial optical path length of the measurement optical path is a position information extraction means (22) for obtaining a distance difference between the distance between the head and the object to be measured and the target distance output from the position detector. When,
Z-axis control means (20) for relatively changing the distance between the head and the object to be measured so that the distance difference obtained by the position information extraction means is eliminated.

  According to a third aspect of the present invention, in the second aspect of the present invention, the distance between the head and the object to be measured is a distance between the objective lens and the object to be measured, and the target distance is the object. The configuration is the focal length of the lens.

  According to a fourth aspect of the present invention, in the invention according to the first, second, or third aspect, the position detection unit is mounted on the head and emits the light for position detection. And an optical path introducing means (25) for introducing the position detecting light into the same optical path as the broadband light source, and the optical path introducing means is incident on the object to be measured via the objective lens and the optical path forming section. The position detecting light is further configured to include the imaging means (10) for imaging that the light for position detection is reflected from the object to be measured at a predetermined angle and returns through the optical path forming unit and the objective lens. The distance between the head and the object to be measured is detected.

  According to a fifth aspect of the present invention, in the invention according to the first, second, or third aspect, the position detection unit includes a light projecting light source (12) that emits the position detection light and the position detection light. Light path introducing means (25) for introducing the light into the same optical path as the broadband light source, and for detecting the position which is incident on the object to be measured and returned by the optical path introducing means via the objective lens and the optical path forming section. And a light receiving means (14) for detecting the position detection light separated by the optical path separating means. It was set as the structure which detects the distance with an object.

  According to a sixth aspect of the present invention, in the first, second, or third aspect of the present invention, the position detection unit is mounted on the head, and is an optical path separate from the optical path of the broadband light source. The position detection light is directly irradiated, and the measurement light reflected from the measurement object at the predetermined angle is directly received to detect the position of the measurement object.

The invention according to claim 7 is the XY moving means (21) for moving the object to be measured in a direction orthogonal to the optical axis direction of the objective lens in the invention according to any one of claims 1 to 5. With
The position information detection means detects a change in the distance between the head and the object under measurement based on an output from the position detection unit during movement by the XY movement means,
The optical path length varying unit is configured to change the optical path length by changing the range in which the optical path length is changed to a range including the variation of the distance.

The invention according to claim 8 receives the broadband light from the broadband light source (1) and branches it into a reference optical path for irradiating the reference mirror and a measurement optical path for irradiating a desired measurement range of the object to be measured. An optical path forming unit (5) for combining and outputting the reflected light from the mirror and the object to be measured, and broadband light between the broadband light source and the optical path forming unit or toward the object to be measured in the measuring optical path In the three-dimensional shape measuring method by the three-dimensional shape measuring apparatus that includes the objective lens (4) that collects the light and the head mounted thereon and measures the shape based on the output of the optical path forming unit,
Before measuring the shape by the broadband light,
The position detection unit directly or indirectly irradiates the object to be measured with position detection light, receives the reflected light reflected from the object to be measured, and detects the distance between the head and the object to be measured. A position detection stage to perform,
A position information extraction step for obtaining a distance difference between the distance between the head and the object to be measured detected in the position detection step and a preset target distance;
An optical axis direction moving stage for changing a relative distance between the objective lens and the object to be measured so that a distance difference obtained in the position information extracting stage becomes zero;
After the relative distance is set, an optical path length variable step of changing an optical path length of either the reference optical path or the measurement optical path;
An imaging step of imaging the output of the optical path forming unit over the measurement range according to the change in the optical path length;
Detecting an optical path length at which interference fringes appear at each point of the measurement range obtained from the output of the imaging means; and
And a measurement step of measuring the shape of the object to be measured based on the optical path length detected corresponding to each point in the measurement range.

  According to the invention described in each of the claims except for the eighth aspect, the position of the object to be measured is detected, and control is performed so that the target position (the focal position of the objective lens) matches the position of the object to be measured. Therefore, the focal length is automatically adjusted quickly. Therefore, measurement can be performed quickly and an effective dynamic range can be secured.

  According to the eighth aspect of the present invention, since the variation of the position of the measured object when the measured object is moved can be detected and reflected in the change range of the optical path length, the sled is measured on the measured object. Even if there is, etc., an effective dynamic range can be secured.

  According to the fourth aspect of the present invention, since the imaging means can be used for both interference fringe detection and focal length adjustment, the configuration becomes simple.

  According to the fifth aspect of the present invention, since the position detection unit for measuring the distance between the objective lens and the object to be measured is independent of the optical path forming unit, the configuration of the optical system can be simplified.

  An embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a functional configuration of the first embodiment. An imaging unit (camera 10) is used to capture the interference fringes generated by the optical path forming unit and the distance between the objective lens 4 and the object 7 to be measured. An example in which both the position detection unit 16 to be measured is used is shown. FIG. 2 is a diagram showing a functional configuration of the second embodiment. Apart from the imaging means (camera 10) for imaging the interference fringes generated by the beam splitter 5 (corresponding to the optical path forming unit described in the claims), FIG. An example in which a light receiving sensor 14 for measuring the distance between the objective lens 4 and the object 7 to be measured is provided. FIG. 3 is a diagram showing a functional configuration of the third embodiment. The beam splitter 5 that causes interference and the position detector 16 that measures the distance between the objective lens 4 and the object 7 to be measured are independently provided. An example is shown. FIG. 4 is a diagram for explaining shape measurement based on interference fringes. FIG. 5 is a flowchart for explaining the operation of the present invention. FIG. 6 is a diagram for explaining the influence on the focal length adjustment when the measurement object 7 is warped.

“First Embodiment”
Hereinafter, based on FIG. 1, when generating interference fringes and acquiring three-dimensional shape data, and when adjusting the position of the DUT 7 in the Z-axis direction (optical path length changing direction) at the initial measurement stage The case will be explained separately. In the following description, the plane perpendicular to the paper surface of FIG. 1 is the XY plane, the horizontal direction is the X-axis direction, and the vertical direction of the paper surface of FIG. 1 is the Z-axis direction. At that time, the Z-axis direction is the measurement optical path direction, and is also the optical path length changing direction. Since the optical path length of the measurement optical path is changed with time and interference fringes are obtained, the Z-axis direction is also the time axis direction in which the interference fringes appear. Hereinafter, these terms may be used properly according to the explanation.

[Configuration of optical system and processing system for generating interference fringes]
The configuration of the optical system will be described with reference to FIG. When generating the interference fringes, the light projecting laser 12 used for adjusting the position of the object 7 to be measured is not used, so that the laser light (measurement light) is blocked from entering the mirror 25. Hereinafter, description will be given in this state.

  The light source 1 is a light source that emits broadband light having a large number of spectrum components (wavelength components) over a wide band and low coherency. Here, for example, a white light source is used. The collimator lens 2 narrows the white light (broadband light) from the light source 1 and sends it to the beam splitter 3. The beam splitter 5 converts the direction of white light and sends it to the objective lens 4. The objective lens 4 converts the narrowed white light into parallel light and sends it to the beam splitter 5 (optical path forming unit). The beam splitter 5 branches the white light received from the objective lens 4 in two directions, and one of them is sent to the device under test 7 as parallel light (the light path from the beam splitter 5 to the device under test 7 is taken as a measurement light path). The other is sent as reference light to the reference mirror 6 as parallel light (the optical path from the beam splitter 5 to the reference mirror 6 is taken as the reference optical path). The objective lens 4 may be arranged not between the beam splitter 5 but between the beam splitter 5 and the object 7 to be measured. In this case, the same objective lens 4 is also inserted in the reference optical path. In either case, the measurement object 7 and the reference mirror 6 are irradiated with parallel light.

  In this example, the distance between the beam splitter 5 and the reference mirror 6 is fixed, that is, the optical path length of the reference optical path is fixed. The light source 1, the collimator lens 2, the beam splitter 3, the beam splitter 5, and the objective lens 4 are mounted on the head 11, and their dimensional relationships are fixed. Furthermore, a reference mirror 6, a camera 10 and an imaging lens 9 are also mounted on the head 11.

  The bundle of white light that has passed through the measurement optical path is sized to irradiate a desired measurement range (a surface that spreads in the XY plane direction) on the surface of the DUT 7. If the objective lens 4 is moved in the measurement optical path direction (Z-axis direction), the range can also be changed.

  The DUT 7 is mounted on the piezo 8, and the piezo 8 is mounted on the XY stage 21 (XY moving means). The XY stage 21 is for conveying the object 7 to be measured at the start of measurement and setting it to the initial position irradiated by the measurement optical path. Direction) and a Y direction (a direction perpendicular to the paper surface of FIG. 1). The piezo 8 is composed of a piezoelectric element, and in accordance with an instruction from the optical path length control means 18, the measured object 7 is moved stepwise or continuously with respect to the XY plane in the Z-axis direction (up and down direction on the paper surface of FIG. 1). The optical path length of the measurement optical path is variably controlled by being displaced (moved) to. When changing in stages, a fixed distance is changed in steps at regular intervals. However, changing this step by step is the same as changing it substantially continuously. When changing continuously, change at a constant speed.

  Therefore, if the position of the beam splitter 5 is fixed, the piezo 8 is means for changing the optical path length of the measurement optical path (optical path length variable means) under the control of the optical path length control means 18. Here, the description will be made by fixing the optical path length of the reference optical path and changing the optical path length of the measurement optical path. However, in order to generate interference fringes described later, the piezo 8 is attached to the reference mirror 6 and the measurement optical path is fixed. The optical path length of the reference path can be changed.

  Each white light reflected from the reference mirror 6 and the object to be measured 7 (hereinafter sometimes referred to as “return white light”) is combined (combined) by the beam splitter 5 and further collected by the objective lens 4. The light is passed through the beam splitter 3, converted into parallel light by the imaging lens 9, and input to the camera 10. At this time, in response to an instruction from the optical path length control means 18, the camera 10 returns white light according to the distance by which the piezo 8 changes the optical path length of the measurement optical path, and interference fringes due to the return white light are imaged. The The captured interference fringes are stored in the memory 17.

  In response to the change in the optical path length (Z-axis direction) of the measurement optical path, the camera 10 is generated by the light reflected from the desired measurement range irradiated by the white light passing through the measurement optical path and the light from the reference optical path. Shoot interference fringes. Therefore, each point that can be photographed at each point in the desired measurement range (each measurement position in the XY direction), in other words, an image pickup device in which the camera 10 is arranged (corresponding to a pixel, hereinafter may be referred to as “pixel”). Take an image of the irradiation spot.

  The memory 17 generates a timing signal at a constant time interval according to the length of the change that the optical path length control means 18 instructs the piezo 8 to change the optical path length. Data (becomes luminance data indicating the luminance of the return white light) is captured and stored for each measurement position (each pixel) in the measurement range. For example, if the optical path length is changed continuously in a linear manner in time, or if a timing signal at a certain time interval is received and changed at a step of that certain time interval (timing interval), The timing signal of that step is stored as a Z-axis address. These timing advance directions (that is, the Z-axis address direction) represent the Z-axis direction. At that time, the imaging data is stored almost simultaneously for each measurement position in the measurement range on the surface of each object to be measured 7. The imaging data at each measurement position in the measurement range of the DUT 7 corresponds to the pixel position. Then, if the imaging data is extracted from the memory 17 in the order of the Z-axis addresses and reproduced, the interference fringe data as shown in FIG. 5 can be obtained.

  FIG. 5 shows a measurement example of interference fringes at two points (Xm, Yp) and (Xs, Ys), for example, as representative of the measurement position in the measurement range. 5 is a case where the optical path length of the reference optical path and the optical path length of the measurement optical path are the same. The wavelength of the interference fringes is formed by combining the wavelengths that are elements of substantially white light (broadband light), and is approximately ½ of the wavelength at the center of those bands. Further, the spread of the interference fringes in FIG. 5 in the optical path length direction depends on the degree of coherency of the white light. The lower the coherency, the narrower the spread.

  The signal processing means 19 reads out the imaging data at the measurement position (Xm, Yp) from the memory 17 in the order of the Z-axis address as shown in FIG. 5, for example, and detects the peak value as the position of the interference pattern of white light. The optical path length Z1 at the position (hereinafter referred to as “specific optical path length”) is obtained (see FIG. 5). Then, the interference fringes are similarly measured at the reference measurement position (Xs, Ys), and the optical path length Zs (specific optical path length) indicating the peak value at that time is obtained. The difference Zs-Z1 is the height of the measurement position (Xm, YP) with respect to the reference measurement position (Xs, Ys). Therefore, if the same calculation process is performed for each measurement position (pixel position) from the memory 17, the height (distance in the Z-axis direction) of the entire surface of the device under test 7 can be measured. The imaging data stored in the memory 17 is sampled and stored at regular time intervals in response to the timing signal (FIG. 5 is a schematic representation continuously connecting them. ) So it becomes discrete. If this time interval is fine enough to be ignored with respect to the width of each of the interference fringes in FIG. 5, the signal processing means 19 obtains the maximum points of the imaged data (luminance data). The peak value of the envelope to be obtained may be obtained by calculation. The signal processing means 19 may be obtained by discrete processing as described in JP-A-9-318329. The repetitive waveform of interference fringes as shown in FIG. 5 can be restored if there is sampling data of 3 points in one period.

[Configuration of optical system and processing system for adjusting the initial position of the DUT 7 in the Z-axis direction]
Since the adjustment of the initial position of the DUT 7 in the Z-axis direction (optical path length changing direction) is performed as a pre-stage of measurement of interference fringes, white light from the light source 1 is incident on the beam splitter 3 in the following description. However, the description will be made ignoring the incidence of white light.

  As described above, in the initial stage before measurement for measuring interference fringes (initial stage before changing the optical path length), the target position at which the change range of the optical path length is effective for the position of the DUT 7 in the Z-axis direction. It is necessary to adjust to. In FIG. 1, the optical path length of the initial measurement optical path is adjusted and set to the target distance so as to cross the optical path length of the reference optical path in the change range when the optical path length of the measurement optical path is changed by the optical path length control means 18. It is necessary to keep. The distance to be adjusted is the distance between the head 11 and the DUT 7 at the initial point before changing the optical path length. This is a broad meaning, and may be the distance between the beam splitter 5 and the object 7 to be measured that are in a fixed positional relationship with the XY stage 21 or the distance between the object 7 to be measured and the objective lens 4. In the following description, “distance between the measured object 7 and the objective lens 4” may be described as “adjustment target distance”, and the focal length of the objective lens 4 may be described as “target distance”.

  The light projecting laser 12, the light projecting collimator lens 13, the mirror 25, and the camera 10 constitute a position detection unit 16 that measures the distance between the objective lens 4 and the object 7 to be measured. These are fixed together with the light source 1 and beam splitters 3 and 5 to a head 11 having a mechanism movable in the Z-axis direction. The camera 10 is also used for shape measurement by interference fringes with white light.

  As described above, in the initial stage before measurement for measuring the interference fringes, adjustment is performed so that the distance between the DUT 7 and the objective lens 4 is adjusted to the target distance (for example, the focal length of the objective lens 4). In this case, it is assumed that the piezo 8 has an initial start position (position in the optical path length changing direction), for example, a change range (also a variable range) set to zero by the optical path length control means 18. In this state, the laser light from the light projecting laser 12 is collimated by the light projecting collimator lens 13 and is separated from the optical axis of the objective lens 25 by the mirror 25 (light path introducing means) (FIG. 1). Is incident on the right side of the optical axis) and projected onto the object to be measured 7 by the beam splitter 5 at a predetermined angle. The laser beam reflected from the object to be measured 7 (hereinafter sometimes referred to as “return laser beam”) is the position where the laser beam is incident on the optical axis of the objective lens 4 via the beam splitter 5. The light is incident on the opposite position (on the left side of the optical axis in FIG. 1). The return laser light is imaged by the camera 10 through the objective lens 4, the beam splitter 3, and the imaging lens 9. The objective lens 4 will be described in the case where it is arranged on the camera 10 from the beam splitter 5 as shown in FIG. 1, but the objective lens 4 is located on the measurement optical path side, that is, between the beam splitter 5 and the object to be measured 7. Also good.

  The reason why the incident laser light and the return laser light are targeted with respect to the optical axis of the objective lens 4 is to detect the distance between the objective lens 4 and the object 7 to be measured by so-called triangulation. . Therefore, the variation in the distance between the objective lens 4 and the object 7 to be measured is the distance in the direction of the angle at which the laser light is reflected by the object 7 to be measured, that is, the distance in the X-axis direction (the lateral direction of the paper surface) Appears as

Therefore, the camera 10 is, for example, an image pickup device (for example, a CCD in pixel units) arranged at a predetermined interval in the direction in which the laser beam is reflected by the object 7 to be measured, in the direction of the spread of the angle, that is, in the X-axis direction (the lateral direction of the paper). Element, or CMOS type element), for example, b _n , b _(n−1) ... B ₁ , b _0, b ₋₁ ... B _{− (n−1)} , b _−n element array, and when the element b ₀ is detected, the position is adjusted so that the distance between the objective lens 4 and the object to be measured 7 is equal to the focal length. B _n , b _(n−1) ... B ₁ , b ₋₁ ... B _{− (n−1)} , b It is necessary to perform pricing in advance by performing calibration in association with the position of each element of _−n . These calibrated values are stored in advance by the position information extraction means 22.

The memory 17 receives and stores data obtained by the camera 10 returning and imaging the laser beam. The data at that time is data from an element (pixel) that has received the return laser beam, and is data indicating the element (for example, element b _k ). The interference fringes are stored in a different area from the data for imaging.

The position information extraction unit 22 reads out data captured by the camera 10 from the memory 17. For example, if the data is _obtained by imaging the return laser beam by the element b _k , b _k −b ₀ (k is positive). Or b ₀ -b _k (when k is negative), the relative position with respect to the target distance (the distance between the objective lens 4 and the object 7 to be measured and the target distance, for example, the focal length). Detect and output the deviation. b _k and b ₀ use calibrated values.

The Z-axis control means 20 receives the output of the position information extraction means 22, moves the head 11 in the Z-axis direction, and sets the distance between the objective lens 4 and the measured object 7 and the target distance (focal length). Control the amount of deviation to zero. For example, the head 11 is controlled so as to perform negative feedback by an amount corresponding to b _k -b ₀ or b ₀ -b _k . However, it is desirable that the amount of deviation is zero, but generally there is a problem such as noise, and if the amount of deviation is within a predetermined threshold range, it is OK. The position information extraction unit 22 and the Z-axis control unit 20 adjust the initial optical path length (position) by adjusting the position of the head 11.

The head 11 has a mechanism that moves in the Z-axis direction by a motor or the like. The head 11 is converted by the Z-axis control means 20 into a drive amount corresponding to, for example, a distance of b _k -b ₀ or b ₀ -b _k and controlled. Is done.

  As described above, the initial position of the DUT 7 is automatically set at the initial stage before the start of the shape measurement, that is, at the initial time before the optical path length is changed by the shape measurement. Therefore, by changing the optical path length during the subsequent shape measurement, the optical path length of the reference optical path can always be matched with the change of the optical path length of the measuring optical path. That is, a dynamic range can be secured.

[A series of operations of the embodiment]
The operation flow of the first embodiment will be described with reference to FIG. In other embodiments described later, the operation flow is substantially the same.

Step S1: When a start instruction is issued from the user interface 24, the measurement control means 23 sets the device under test 7, and the optical path length control means 18 sets the control amount for the piezo 8 to an initial value (for example, zero). .
Steps S2 and 3: The laser light from the light projecting laser 12 is incident on the object to be measured 7 via the mirror 25, the objective lens 4 and the beam splitter 5. Then, the return laser beam is imaged by the camera 10, and the imaging position (for example, b _k ) is stored in the memory 17. The position information extraction unit 22 obtains a deviation amount b _k −b ₀ or b ₀ −b _k between the distance between the objective lens 4 and the object 7 to be measured and the target distance (focal length), and the Z-axis control unit 20. However, the head 11 is subjected to negative feedback control so that the amount of deviation becomes zero. That is, control is performed so that the distance between the objective lens 4 and the object 7 to be measured matches the target distance (S2). The Z-axis control means 20 determines whether or not the amount of deviation is within a predetermined range (for example, when the amount of deviation is a noise level) (S2). Is moved to the target distance (S3). When the amount of deviation falls below the predetermined range (S2-YES), the control amount that controlled the head 11 is held. And it hold | maintains until the measurement of the interference fringe by white light is completed. Until the measurement is completed, the laser beam from the light projecting laser 12 is blocked from entering the mirror 25.

Step S4: When the distance between the objective lens 4 and the object 7 to be measured matches the target distance (focal length), interference fringe measurement using white light from the light source 1 is performed. First, the return white light when the change of the piezo 8 is zero, that is, the change optical path length is zero, is captured by the camera 10 and stored in the memory 17. Similarly, if the optical path length is changed by a predetermined length at a timing T ranging from 0 to n in the cycle T, the optical path length (Lk) is changed and set for each timing k (n ≧ k ≧ 0). Then, this is repeatedly executed up to the optical path length Ln, and the imaging data is stored in the memory 17 in order for each pixel (for each measurement position in the measurement range).
Step S5: The signal processing means 19 reads each imaging data in each measurement range from the memory 17, and obtains a specific optical path length at a point where the peak of the interference fringe appears. The three-dimensional shape of the object to be measured 7 can be obtained by obtaining the specific optical path length at all positions in the desired measurement range. For example, the signal processing unit 19 obtains a relative shape by obtaining a difference between the specific optical path length of the reference measurement position (Xs, Ys) and the specific optical path length Zm, p of the other measurement position Xm, Yp). be able to. This shape can be displayed on the display device.

Step S6: Next, when measuring another object to be measured 7 of the same type, the process jumps to Step 8, and if the measurement is finished, the shape value is output (displayed) in Step 7 and the process is ended.

Step 8: When measuring the next object 7 to be measured, the measurement control means 23 moves the object 7 previously measured by moving the XY stage 21 and transports the next object 7 to be measured. Set the position. At that time, it is set again so that the laser light from the light projecting laser 12 enters the mirror 25. Since the object to be measured 7 is transported in the X direction or the Y direction on the surface of the object 7 to be measured, the object 7 and the objective lens 4 previously measured during the movement are also moved. Measure the distance between and memorize the change of the distance. The variation of the distance becomes a warp of the measurement object 7 (including the displacement of the surface of the measurement object 7).
Step 9: The range in which the optical path length control unit 1 can change the optical path length when measuring the next object to be measured 7 is set as a new changed range to which the variation of the distance measured while moving the XY stage 21 is added. . Actually, when the next object to be measured 7 is measured from step S1, in step S4, the measurement is performed in a wide new change range including the above-mentioned distance variation from the previous time. Therefore, the fluctuation can be absorbed in the change range, so that the dynamic range is ensured.

  For example, FIG. 6 shows an example in which a change in distance between points A and B, that is, a change Δe due to warpage or the like is measured while the DUT 7 is moving. Assuming that the optical path length change range at point A, that is, the dynamic range is D1 and the interference fringes can be measured, the magnitude Δe of the fluctuation (warp or the like) does not affect the optical path length change range D1. However, for example, at the point B, it is necessary to set the optical path length change range D2 = D1 + Δe according to the measured variation. By doing so, a substantial dynamic range D1 can be secured. If this process is not performed, the dynamic range of point B is D1-Δe, which becomes narrow.

  It should be noted that the position information extraction unit 22 is configured to, for example, the distance between the objective lens 4 and the object to be measured 7 and the target distance at the measurement position A point (Xa, Ya) and B point (Xb, Yb) in FIG. The amount of deviation from (focal length) is stored as Δe (a) and Δe (b), respectively, and the magnitude of warpage at that point can be known from the difference between them. That is, the operator can be informed of the size of the warp of the DUT 7.

[Second Embodiment]
In the second embodiment, the configuration operation when generating interference fringes and acquiring three-dimensional shape data is the same as that in the first embodiment, and the position of the DUT 7 in the initial measurement is adjusted in the Z-axis direction. In this regard, the configuration is different from that of the first embodiment. The difference will be described below.

  A second embodiment will be described with reference to FIG. In FIG. 2, the difference from the first embodiment is that the return laser light that is incident on the object to be measured 7 from the light projecting laser 12 via the objective lens 4 and is returned is imaged by the camera 10 in FIG. However, in FIG. 2, the light is separated and changed from the optical path of the white light by the mirror 26 (optical path separating means), condensed by the light receiving imaging lens 15, and received by the light receiving sensor 14. . In other words, the light receiving sensor 14 replaces the camera 10. The light receiving sensor 14 is a displacement sensor (for example, PSD) that outputs a signal corresponding to the light receiving position on the surface of the light receiving sensor 14. That is, when the distance between the objective lens 4 and the object 7 to be measured changes, the light receiving position of the light receiving sensor 14 changes, and a signal in response to the change can be obtained (so-called position information, the camera 10 The position information extracting unit 22 and the Z-axis control unit 20 control the head 11 to control the objective lens 4 and the object to be measured. 7 can be adjusted to a target distance (focal length of the objective lens 4).

[Third Embodiment]
In the third embodiment, the configuration operation in generating interference fringes and acquiring three-dimensional shape data is the same as that in the first embodiment, and the position of the DUT 7 in the initial measurement is adjusted in the Z-axis direction. In this regard, the configuration is different from the first and second embodiments. The difference will be described below.

  A third embodiment will be described with reference to FIG. The position detection unit 16 in FIG. 3 includes a light projecting laser 12, a light projecting collimator lens 13, a light receiving sensor 14, and an objective lens (not shown) for condensing the laser light on the object 7 to be measured. May be the same as the objective lens 4). The distance (displacement) measurement operation is the same as in FIG. In other words, the operation is the same as when the beam splitter 5 of FIG. 2 is not provided. However, since it is in an independent position without passing through the objective lens 4, the distance between the objective lens 4 and the object 7 to be measured at the measurement position where the interference fringe is to be measured cannot be measured directly. The distance is adjusted to the target distance (focal distance). For example, as shown in FIG. 3, the target position (focal length) is adjusted at an end portion or the like that deviates from the center of the measurement position of the DUT 7. In this case, if there is a distance difference between the position and the end of the measurement range where the shape is to be measured, the distance difference is measured in advance and offset to the optical path length change range of the optical path length control means 18. We can cope by putting. If the offset adjustment is performed with one measured object 7, even if the measured object 7 is replaced with another measured object 7, it can be handled in the same manner, so that the offset adjustment is unnecessary.

  In the above configuration, the processing control unit 100, the position information detection unit 22, and the Z-axis control unit 22 can be configured by a memory in which the operation flow is programmed and a CPU that executes the memory.

It is a figure which shows the function structure of 1st Embodiment, and the position which measures the position of the to-be-measured object 7 and the imaging means (camera 10) image the interference fringe produced | generated from the beam splitter 5 (optical path formation part) An example in which both detection units 16 are used will be shown. It is a figure which shows the function structure of 2nd Embodiment, and the light receiving sensor 14 for measuring the position of the to-be-measured object 7 was provided separately from the imaging means (camera 10) which images the interference fringe which the interference part produced | generated. An example is shown. It is a figure which shows the function structure of 3rd Embodiment, and shows the example which provided the interference part 11 and the position detection part 16 which measures the distance of the objective lens 4 and the to-be-measured object 7 independently. It is a flowchart explaining operation | movement of this invention. It is a figure for demonstrating shape measurement based on an interference fringe. It is a figure for demonstrating the influence on the focal distance adjustment at the time of matching with the to-be-measured object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Collimator lens 3 Beam splitter 4 Objective lens 5 Beam splitter 6 Reference mirror 7 Measured object 8 Piezo 9 Imaging lens 10 Camera 11 Head 12 Light projection laser 13 Light projection collimator lens 15 Light receiving imaging lens 16 Position Detection unit 17 Memory 18 Optical path length control means 19 Signal processing means 20 Z-axis control means 21 XY stage 22 Position information extraction means 23 Measurement control means 24 User interface 25 Mirror 26 Mirror

Claims (8)

A broadband light source (1) for outputting broadband light having a broadband spectrum, and a reference optical path for irradiating the broadband light to a reference mirror and a measurement optical path for irradiating a desired measurement range of the object to be measured. And an optical path forming section (5) for combining and outputting the reflected light from the object to be measured, and provided between or in the measurement optical path between the broadband light source and the optical path forming section, An objective lens (4) for irradiating the measurement range of the surface of the object to be measured;
An optical path length varying means (8) for changing the optical path length of either the reference optical path or the measurement optical path over a predetermined range, and the optical path forming unit corresponding to the measurement range according to the change of the optical path length. An image pickup means (10) for picking up an output, and a three-dimensional shape measuring apparatus for measuring a shape based on interference fringes obtained from the output of the image pickup means;
A position detector (16) for irradiating the object to be measured with position detection light in the initial stage of measuring the shape and detecting the distance between the head and the object to be measured based on the reflected light from the object to be measured. When,
The reference optical path or the measurement so that the interference fringes are obtained when the optical path length is changed over the predetermined range based on the distance between the head and the object to be measured output from the position detection unit. And a means (20, 22) for adjusting the initial optical path length of any one of the optical paths. When the optical path length of the reference optical path is set to a fixed length and the optical path length is varied in advance over the predetermined range, the distance between the head and the object to be measured can be changed so that the optical path length of the measurement optical path exceeds the fixed length. It is set as a target distance in advance,
The means for adjusting the initial optical path length of the measurement optical path includes position information extraction means (22) for obtaining a distance difference between the distance between the head and the object to be measured and the target distance output from the position detection unit. ,
The Z-axis control means (20) for relatively changing the distance between the head and the object to be measured so as to eliminate the distance difference obtained by the position information extraction means. The three-dimensional shape measuring apparatus according to 1.   The tertiary according to claim 2, wherein the distance between the head and the object to be measured is a distance between the objective lens and the object to be measured, and the target distance is a focal length of the objective lens. Original shape measuring device.   The position detection unit is mounted on the head, and projects a light source (12) for irradiating the position detection light, and an optical path introduction unit (12) for introducing the position detection light into the same optical path as the broadband light. 25) and the position detection light incident on the object to be measured via the objective lens and the optical path forming unit by the optical path introducing means is further reflected from the object to be measured at a predetermined angle to form the optical path. And an imaging means (10) for imaging the return through the objective lens and the objective lens, and detecting a distance between the head and the object to be measured. Or the three-dimensional shape measuring apparatus of 3.   The position detection unit includes: a light projecting light source (12) that emits the position detection light; an optical path introducing means (25) that introduces the position detection light into the same optical path as the broadband light source; and the optical path. An optical path separating means (26) for extracting the position detecting light incident on the object to be measured through the objective lens and the optical path forming section by the introducing means and returning to the optical path different from the broadband light source; and the optical path The light receiving means (14) for detecting the light for position detection separated by the separating means, and detecting the distance between the head and the object to be measured. Three-dimensional shape measuring device.   The position detection unit is mounted on the head and is irradiated with light for position detection directly on the object to be measured by an optical path different from the optical path of the broadband light source, and reflected from the object to be measured at the predetermined angle. The three-dimensional shape measuring apparatus according to claim 1, wherein the position detecting light is directly received to detect the position of the object to be measured. XY movement means (21) for moving the object to be measured in a direction orthogonal to the optical axis direction of the objective lens,
The position information detection means detects a change in the distance between the head and the object under measurement based on an output from the position detection unit during movement by the XY movement means,
6. The tertiary according to claim 1, wherein the optical path length changing unit changes the optical path length by changing a range in which the optical path length is changed to a range including the variation of the distance. Original shape measuring device. Receiving broadband light from the broadband light source (1), it is branched into a reference optical path for irradiating the reference mirror and a measurement optical path for irradiating a desired measurement range of the object to be measured, and reflection from the reference mirror and the object to be measured. An optical path forming unit (5) for combining and outputting light, and the objective lens (4) for condensing the broadband light toward the object to be measured between the broadband light source and the optical path forming unit or in the measurement optical path. And a three-dimensional shape measuring method using a three-dimensional shape measuring device that measures the shape based on the output of the optical path forming unit,
Before measuring the shape by the broadband light,
The position detection unit directly or indirectly irradiates the object to be measured with position detection light, receives the reflected light reflected from the object to be measured, and detects the distance between the head and the object to be measured. A position detection stage to perform,
A position information extraction step for obtaining a distance difference between the distance between the head and the object to be measured detected in the position detection step and a preset target distance;
An optical axis direction moving stage for changing a relative distance between the objective lens and the object to be measured so that a distance difference obtained in the position information extracting stage becomes zero;
After the relative distance is set, an optical path length variable step for changing an optical path length of either the reference optical path or the measurement optical path;
An imaging step of imaging the output of the optical path forming unit over the measurement range according to the change in the optical path length;
Detecting an optical path length at which interference fringes appear at each point of the measurement range obtained from the output of the imaging means; and
A shape measuring method comprising: a measuring step of measuring the shape of the object to be measured based on an optical path length detected corresponding to each point of the measurement range.

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