WO2013150585A1

WO2013150585A1 - Edge detecting apparatus

Info

Publication number: WO2013150585A1
Application number: PCT/JP2012/058930
Authority: WO
Inventors: 琢也野口; 河野　裕之; 仲嶋　一; 恵美子倉田; 隆湯澤; 隆史平位
Original assignee: 三菱電機株式会社
Priority date: 2012-04-02
Filing date: 2012-04-02
Publication date: 2013-10-10
Also published as: JPWO2013150585A1

Abstract

This edge detecting apparatus is provided with: a projection system (110), which radiates an optical beam to a subject to be measured; a light receiving system (120), which has a light detector (8) that detects light radiated from the projection system and reflected by the subject to be measured; a first drive apparatus (130), which relatively moves the subject to be measured and the projection system; an edge calculating unit (140), which obtains an edge position on the basis of reflection light quantity characteristics obtained from the light detector; an edge determining unit (150), which detects an abnormal edge on the basis of the edge position obtained by means of the edge calculating unit; and an edge detecting unit (160), which detects a final edge on the basis of the edge obtained from an edge determining unit (190). Among edge positions measured at a plurality of areas in the direction orthogonal to the scanning direction, an edge at the outermost end portion is detected, and reflection light quantity characteristics wherein the absolute value of a difference between the edge at the outermost end portion and each of the edge positions is larger than a difference threshold value obtained by means of the edge determining unit are excluded.

Description

Edge detection device

The present invention relates to an edge detection device that includes a light emitting unit for emitting light and a light receiving unit for receiving reflected light from a measured object, and detects an edge position of the measured object based on the reflected light. .

A wire electric discharge machine that processes a workpiece by electric discharge between a thin wire (wire) and the workpiece is generally a discharge phenomenon between a wire for processing the workpiece and the wire and the workpiece. And a stage drive device for processing the workpiece into a desired shape, so that the workpiece is immersed in a processing fluid such as water or oil to generate a discharge phenomenon. The shape of the workpiece is processed by moving it.

This type of wire electric discharge machine measures the shape of the workpiece during machining, feeds back the measured workpiece dimensions, performs additional machining on the workpiece, and drives the final shape. ing. Conventionally, a contact-type probe is used for measuring the shape of a workpiece, and the dimensions between the processed cross sections are measured by applying the probe to a plurality of processed cross sections. However, in order to perform such a shape measurement, it is necessary to remove the working liquid once and remove the workpiece from the wire electric discharge machine, and there is a problem that it takes time to drive to the final shape. . In order to solve such problems, for example, non-contact sensors as shown in Patent Document 1 to Patent Document 3 have been developed.

For example, Patent Document 1 discloses a method for detecting an edge in a workpiece such as a substrate. In this method, a camera is placed on the upper part of the work, while the work is irradiated with light from, for example, 90 degrees, and the obtained captured image is obtained from the average peak intensity of the one-dimensional profile by image processing. It is configured to detect the edge of.

Further, for example, Patent Document 2 discloses a method for discriminating the edge of a circuit pattern. In this method, a camera is placed above the circuit pattern, the circuit pattern is illuminated by an illuminating device, and the difference in the average value of the density levels of image data obtained by the camera or the difference in the average value is obtained. A threshold value is set for the data portion, and a data portion equal to or higher than the threshold value is recognized as an edge.

Further, for example, Patent Document 3 discloses a method for specifying the position of an alignment mark. In this method, the light quantity signal reflected from the alignment mark is acquired, and the position of the alignment mark is determined from the peak value of the differential waveform obtained by differentiating this light quantity signal, the integral value within a range of the differential waveform, and the height difference of the differential value. Is configured to do.

JP 2000-304510 A JP 2000-31245 A JP 2005-175041 A

However, the following points can be cited as common problems in Patent Documents 1 to 3 described above.
That is, the object to be measured processed by the wire electric discharge machine extends in the Y direction on a plane orthogonal to the paper surface in FIG. Minute irregularities having a period of several μm and a height of several μm are generated in the cross section 6b. Furthermore, the surface 6c of the object to be measured is not a perfect mirror surface and has minute irregularities of about several μm. Therefore, when the edge of the object to be measured is scanned with a small beam spot having a diameter of about several μm, the measurement is performed according to the measurement position in the Y direction in FIG. There is a problem that the characteristics change greatly.

Furthermore, for example, in the case of cutting or the like, a protrusion called “burr” occurs on the edge to be detected, but “burr” does not occur in the processing by the wire electric discharge machine. However, in the measured object 6 processed by the wire electric discharge machine as a phenomenon peculiar to the wire electric discharge machine, the edge to be detected is a part of the original edge line 01 as shown in FIG. May be the edge line 02 lacking inside the DUT 6.

In the conventional edge detection apparatus in Patent Document 1, even if the edge of a smooth edge or a smooth edge is rough, the spread of the luminance distribution changes, but the peak position is detected stably. Is possible. However, with respect to the edge missing portion which is a phenomenon peculiar to the wire electric discharge machine as shown in FIG. 23, the edge detecting device of Patent Document 1 also detects the edge missing portion as an edge. Therefore, when the lines A, B, and C in FIG. 23 are averaged in order to reduce the influence of minute irregularities on the side surface and surface of the object to be measured, the true edge is lined under the influence of the edge missing portion. There was a problem of erroneous detection as 02. Furthermore, in the cross section of the measurement object 6 processed by the wire electric discharge machine, the case where the edge of the measurement object 6 is vertical as shown in FIG. 24a and the case where the edge is gentle as shown in FIG. 24b are mixed. ing. In such a case, since the edge detection apparatus of Patent Document 1 illuminates the object to be measured from the side, the edge cannot be detected when the edge as shown in FIG. 24a is vertical. Further, for the gently changing edge as shown in FIG. 24b, the edge O2 is detected, and an edge different from the original edge O1 is detected.

Moreover, in the conventional edge detection apparatus of patent document 2, it becomes possible to exclude a noise component with a small light quantity change by the structure mentioned above. Further, even the conventional edge detection device of Patent Document 3 can detect the position of the alignment mark from the above-described configuration.
However, the devices of Patent Document 2 and Patent Document 3 still have a problem of erroneous recognition of edge lines.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an edge detection device capable of detecting the edge of a measurement object more accurately than in the past. To do.

In order to achieve the above object, the present invention is configured as follows.
That is, an edge detection apparatus according to one aspect of the present invention includes a light source for emitting light to a measurement object, a light receiving element for receiving reflected light from the measurement object, and a position of the measurement object. A first driving device for moving the lens in the X-axis and Y-axis directions orthogonal to each other, an edge calculating unit for calculating an edge from the output from the light receiving element and the first driving device movement amount, and the edge calculation In an edge detection device comprising an edge determination unit for detecting an abnormal edge from the calculation result obtained by the unit, and an edge detection unit for calculating a final edge from the result of the edge determination unit, The reflected light quantity characteristic {I obtained when measuring the M points along the Y axis direction, where I is the reflected light quantity characteristic obtained from the object to be measured when the first driving device is moved in the X-axis direction {I _1, ··· I , ..., characterized by averaging by the following equation I _M}.
I = {I ₁ + I ₂ +... + Im +... + I _M } / M

The edge detection apparatus may be configured as follows.
In other words, an edge detection apparatus according to an embodiment of the present invention includes a light source for emitting light, a light source for emitting light to an object to be measured, and light reflected from the object to be measured. An edge is calculated from a light receiving element, a first driving device for moving the position of the object to be measured in the X-axis and Y-axis directions orthogonal to each other, an output from the light receiving element, and a moving amount of the first driving device. An edge calculation unit, an edge determination unit for detecting an abnormal edge from the calculation result obtained by the edge calculation unit, and an edge detection for calculating a final edge from the result of the edge determination unit In an edge detection device comprising a unit, M points are measured along the Y-axis direction, where I is the reflected light quantity characteristic obtained from the object to be measured when the first driving device is moved in the X-axis direction. Obtained when Shako amount characteristic _{{I 1, ··· Im, ···} , I M} edge from the intersection of the, and the reflected light amount characteristics determined by the intensity threshold an edge position from the peak intensity of the reflected light characteristic at each point position _{{x 1, ··· xm, ···} , x M} calculated and outermost edges of the object to be measured from each edge positions _{{x 1, ··· xm, ···} , x M} Detecting the edge of the portion, and excluding the reflected light quantity characteristic in which the absolute value of the difference value between the obtained edge of the outermost edge portion and each edge position is larger than the difference threshold value preset in the edge determination portion Features.

The edge detection apparatus may be configured as follows.
That is, an edge detection apparatus according to an embodiment of the present invention includes a light source for emitting light to a measurement object, a light receiving element for receiving reflected light from the measurement object, A first driving device for moving the position in the X-axis and Y-axis directions orthogonal to each other; an edge calculating unit for calculating an edge from the output from the light receiving element and the amount of movement of the first driving device; and the edge In an edge detection device comprising an edge determination unit for detecting an abnormal edge from a calculation result obtained by the calculation unit, and an edge detection unit for calculating a final edge from the result of the edge determination unit The reflected light quantity characteristic obtained when measuring the M points along the Y axis direction, where I is the reflected light quantity characteristic obtained from the object to be measured when the first driving device is moved in the X axis direction. _{I 1, ·· Im, · · ·, from _{I M},}

differential waveform

_{D 1 obtained by performing a differentiation operation, ··· Dm, ···, edges at each point from the position of the derivative peak value of _{D M}} position _{{x 1, ··· xm, ···} , x M} calculated and outermost edges of the object to be measured from each edge positions _{{x 1, ··· xm, ···} , x M} Detecting the edge of the portion, and excluding the reflected light quantity characteristic in which the absolute value of the difference value between the obtained edge of the outermost edge portion and each edge position is larger than the difference threshold value preset in the edge determination portion Features.

The edge detection apparatus may be configured as follows.
That is, an edge detection apparatus according to an embodiment of the present invention includes a light source for emitting light to a measurement object, a light receiving element for receiving reflected light from the measurement object, A first driving device for moving the position in the X-axis and Y-axis directions orthogonal to each other; an edge calculating unit for calculating an edge from the output from the light receiving element and the amount of movement of the first driving device; and the edge In an edge detection device comprising an edge determination unit for detecting an abnormal edge from a calculation result obtained by the calculation unit, and an edge detection unit for calculating a final edge from the result of the edge determination unit The reflected light quantity characteristic obtained when measuring the M points along the Y axis direction, where I is the reflected light quantity characteristic obtained from the object to be measured when the first driving device is moved in the X axis direction. _{I 1, ·· Im, · · ·, differential waveform _{D 1 of _{I M}, ··· Dm, ···} , derivative peak value at each point from the _{_{D M} {A 1, ···}} Am, ···, A _M } is calculated, and a reflected light amount characteristic smaller than a differential threshold preset in the edge determination unit is excluded.

The edge detection apparatus may be configured as follows.
That is, an edge detection apparatus according to an embodiment of the present invention includes a light source for emitting light to a measurement object, a light receiving element for receiving reflected light from the measurement object, A first driving device for moving the position in the X-axis and Y-axis directions orthogonal to each other; an edge calculating unit for calculating an edge from the output from the light receiving element and the amount of movement of the first driving device; and the edge In an edge detection device comprising an edge determination unit for detecting an abnormal edge from a calculation result obtained by the calculation unit, and an edge detection unit for calculating a final edge from the result of the edge determination unit The reflected light quantity characteristic obtained when measuring the M points along the Y axis direction, where I is the reflected light quantity characteristic obtained from the object to be measured when the first driving device is moved in the X axis direction. _{I 1, ·· Small im, · · ·, the peak intensity _{P 1 at each point from the _{I M}, ··· Pm, ···} , calculates the _{P M},} than a preset strength threshold value to the edge determination unit The reflected light quantity characteristic is excluded.

According to the edge detection device of one aspect of the present invention, the reflected light quantity characteristic obtained from the object to be measured when the first driving device is moved in the X-axis direction is I, and M locations along the Y-axis direction. Since the reflected light quantity characteristics {I ₁ ,... Im,..., I _M } obtained when the points are measured are averaged, the edge shape of the object to be measured is determined depending on the measurement location. It is possible to reduce measurement errors that occur when the surface state is slightly changed.

Further, according to the edge detecting device in an aspect of the present invention, the reflected light quantity characteristic _{{I 1, ··· Im, ···} , I M} edge positions at each point from _{x 1, · · · xm, .., X _M } is calculated, the edge position of the outermost edge portion of the object to be measured is calculated from the edge positions, and the absolute value of the difference between the edge position of the outermost edge portion and the edge position at each point is calculated. When the value is equal to or greater than a preset threshold value, it is configured to be regarded as an abnormal edge and excluded, so that data is excluded when a part of the edge of the object to be measured is missing. Therefore, the original edge position can be detected more accurately.

Further, according to the edge detecting device in an aspect of the present invention, the reflected light quantity characteristic _{{I 1, ··· Im, ···} , I M} differential waveform _{D 1 obtained by differentiating the, · · · Dm, · · ..., D _M }, the differential peak value {A ₁ ,... Am,..., A _M } is calculated, and abnormal when the differential peak value at each point is less than or equal to a preset differential threshold value. Since the configuration is such that data is excluded by considering it as a sharp edge, the original edge position can be detected more accurately even when the edge of the object to be measured is gentle.

Further, according to the edge detecting device in an aspect of the present invention, the reflected light quantity characteristic _{{I 1, ··· Im, ···} , I M} from the peak intensity _{{P 1, ··· Pm, ···} , P _M } is calculated, and when the peak intensity at each point is equal to or less than a preset intensity threshold, the data is excluded by considering it as an abnormal edge. It is possible to detect the original edge position with higher accuracy.

It is a perspective view which shows the structure of the edge detection apparatus in Embodiment 1 of this invention. FIG. 2 is a relationship diagram between an object to be measured and a focused spot with respect to the edge detection apparatus shown in FIG. 1. FIG. 2 is a relationship diagram between an object to be measured and a focused spot with respect to the edge detection apparatus shown in FIG. 1. FIG. 2 is a relationship diagram between an object to be measured and a focused spot with respect to the edge detection apparatus shown in FIG. 1. It is a figure which shows the reflected light quantity characteristic obtained in the edge detection apparatus shown in FIG. It is a figure which shows the reflected light quantity characteristic which averaged the reflected light quantity characteristic obtained in the edge detection apparatus shown in FIG. It is a figure which shows the reflected light quantity characteristic when the line of several places on a to-be-measured object is scanned in the edge detection apparatus shown in FIG. It is a figure which shows what averaged the reflected light quantity characteristic obtained in the edge detection apparatus shown in FIG. It is a flowchart explaining the edge calculation operation | movement in the edge detection apparatus shown in FIG. In the edge detection apparatus shown in FIG. 1, it is a figure which shows the state to which a to-be-measured object inclines with respect to the moving direction of a 1st drive device. It is a figure for demonstrating the edge position obtained in the state shown in FIG. It is a perspective view which shows the structure of the edge detection apparatus in Embodiment 2 of this invention. It is a figure which shows the differential waveform obtained in the edge detection apparatus shown in FIG. It is a flowchart explaining the edge detection operation | movement in the edge detection apparatus shown in FIG. It is a perspective view which shows the structure of the edge detection apparatus in Embodiment 3 of this invention. It is a figure which shows the reflected light quantity characteristic obtained in the edge detection apparatus shown in FIG. It is a figure which shows the differential waveform obtained in the edge detection apparatus shown in FIG. It is a flowchart explaining the edge detection operation | movement in the edge detection apparatus shown in FIG. It is a perspective view which shows the structure of the edge detection apparatus in Embodiment 4 of this invention. It is a figure which shows typically the unevenness | corrugation in the surface of a to-be-measured object. It is a figure which shows typically the unevenness | corrugation in the surface of a to-be-measured object. It is a figure which shows the reflected light quantity characteristic obtained when the unevenness | corrugation in the surface of a to-be-measured object is scanned. It is a flowchart explaining the edge detection operation | movement in the edge detection apparatus shown in FIG. It is a top view of a to-be-measured object. It is a top view which shows the state which has a chip | tip in the edge part of a to-be-measured object. It is a side view which shows the edge part of a to-be-measured object. It is a side view which shows the edge part of a to-be-measured object. It is a figure which shows the structure of the edge detection apparatus in Embodiment 5 of this invention. It is a figure which shows the structure of the light projection system shown in FIG. It is a figure which shows the structure of the light-receiving system shown in FIG. It is a figure which shows the shape change of the condensing spot on a 4-part dividing photodiode at the time of edge detection. It is a figure which shows the shape change of the condensing spot on a 4-part dividing photodiode at the time of edge detection. It is a figure which shows the shape change of the condensing spot on a 4-part dividing photodiode at the time of edge detection. It is a schematic diagram of the cross section of the edge part in the measurement object which is a mirror surface. It is a figure which shows the light received signal in the 4-part dividing photodiode of the edge part shown to FIG. 29a. It is a figure which shows the difference signal of the light received signal shown in FIG. 29b. It is a figure which shows the light reception signal in a 4-part dividing photodiode at the time of defocusing the light beam irradiated to the edge part shown to FIG. 29a. It is a figure which shows the difference signal of the light received signal shown in FIG. 29d. It is a figure for demonstrating the positional relationship of the condensing beam of a light projection system, and a to-be-measured object in the focus adjustment of a light projection system. FIG. 31 is a graph for explaining a change in amplitude intensity of a received light signal in each positional relationship shown in FIG. 30. FIG. It is a schematic diagram of the cross section of the edge part in the to-be-measured object of the metal which is a rough surface. It is a figure which shows the light reception signal in the 4-part dividing photodiode of the edge part shown to FIG. It is a figure which shows the difference signal of the received light signal shown to FIG. It is a figure which shows the light reception signal in a 4-part dividing photodiode at the time of defocusing the light beam irradiated to the edge part shown to FIG. It is a figure which shows the difference signal of the light received signal shown to FIG. It is a figure which shows the structure of the edge detection apparatus in Embodiment 6 of this invention, and is a block diagram at the time of the focus adjustment of a light projection system. It is a figure which shows the structure of the edge detection apparatus in Embodiment 6 of this invention, and is a block diagram at the time of edge detection. It is a figure which shows the light reception signal in the 4-part dividing photodiode of the edge part obtained with the edge detection apparatus in Embodiment 6. FIG. It is a figure which shows the difference signal of the received light signal shown to FIG. 34a. It is a figure which shows the condensing spot in the focus state in a 4-part dividing photodiode. It is a figure which shows the condensing spot in the defocusing state in a 4-part dividing photodiode. It is a figure which shows the structure of the edge detection apparatus in Embodiment 7 of this invention. It is a figure which shows the structure of the edge detection apparatus in Embodiment 8 of this invention. It is a figure which shows the structure of the edge detection apparatus in Embodiment 9 of this invention. It is a figure which shows the state scanned with the light beam of a big spot size in the edge detection apparatus shown in FIG. It is a figure which shows the signal strength obtained from a photodetector with the defocused light beam shown in FIG. It is a graph which shows the error amount of an edge position at the time of detecting an edge position with the light beam of a small spot size. It is a graph which shows the error amount of an edge position at the time of detecting an edge position with the light beam of a big spot size. It is a schematic diagram which scans the light beam of a small spot size in the position of several Y direction. It is a schematic diagram which scans the light beam of a small spot size in the position of several Y direction.

An edge detection apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In each figure, the same or similar components are denoted by the same reference numerals.

Embodiment 1 FIG.
The configuration of the edge detection apparatus 101 according to the first embodiment is shown in FIG.
The edge detection apparatus 101 is an apparatus that detects an edge of a rough surface of a metal object 6 having a rough scattering surface, that is, a rough surface, by using reflected light of a laser beam irradiated on the rough surface. Here, the edge means a boundary between steps having a height difference on the metal surface. The edge detection apparatus 101 can be used for measuring the shape of a workpiece in electric discharge machining, cutting, grinding, or the like. The object to be measured 6 of the edge detection apparatus 101 is not limited to a metal measurement object having a rough surface. Of course, the edge detection apparatus 101 is a mirror-like object to be measured that is not a rough scattering surface. It is applicable to.

Such an edge detection device 101 has, as its basic configuration, a light projecting system 110, a light receiving system 120, a first drive device 130, an edge calculation unit 140, an edge determination unit 150, and an edge detection unit 160. Is provided. Here, the edge calculation unit 140, the edge determination unit 150, and the edge detection unit 160 correspond to a configuration example of an “edge position acquisition unit”.
Below, the component part of the edge detection apparatus 101 is demonstrated sequentially.

The light projecting system 110 is a component that collects and irradiates light on the object 6 to be measured, and includes a light source 1, a first lens 3, an objective lens 5, and a beam splitter 4. For example, a semiconductor laser or the like is used as the light source 1. The first lens 3 and the objective lens 5 are lenses for condensing the light from the light source 1, and are installed in the lens barrel 2 to condense the light from the light source 1 onto the object to be measured 6. The beam splitter 4 transmits the light beam from the light source 1 to the objective lens 5 and reflects the reflected light from the object to be measured 6 to the light receiving system 120.

In FIG. 1, the light source 1, the first lens 3, the objective lens 5, and the beam splitter 4 form a linear optical path, but the optical path shape is not limited to this.

The light receiving system 120 is a light detection part for receiving the reflected light from the measured object 6 of the light condensed on the measured object 6 by the light projecting system 110. And 8. The second lens 7 is a lens for condensing the reflected light from the beam splitter 4 on the photodetector 8. As the photodetector 8, for example, a photodiode or the like is used.
In addition, the light receiving system 120 is also installed in the lens barrel 2, and the arrangement of the optical components and the number of lenses are not particularly limited to the configuration shown in the drawing as long as they perform the functions described above.

The first driving device 130 is an XY stage that mounts the DUT 6 and can move in the X-axis direction and the Y-axis direction orthogonal to each other on a plane. In the present embodiment, the object to be measured 6 is moved by the first driving device 130 with respect to the fixed light projecting system 110 and light receiving system 120. However, the light projecting system 110, the light receiving system 120, and the object to be measured are moved. Any structure that can move relative to the object 6 may be used. Further, in the present embodiment, it is possible to move only in the XY directions orthogonal to each other in the plane, but a configuration in which a Z-stage is added to move in the direction orthogonal to the XY plane may be adopted.

The edge calculation unit 140 is electrically connected to the photodetector 8 and the first driving device 130, and the edge calculation unit 140 detects the edge of the DUT 6 based on the light amount signal from the photodetector 8 and the position information from the first driving device 140. It is a means for obtaining the position. The edge determination unit 150 is a determination unit that is electrically connected to the edge calculation unit 140 and determines an abnormal edge position from the edge position obtained from the edge calculation unit 140. The edge detection unit 160 is an edge detection unit that is electrically connected to the edge determination unit 150 and detects a final edge position from information from the edge calculation unit 140 and the edge determination unit 150.

The edge calculation unit 140, the edge determination unit 150, and the edge detection unit 160 are actually realized using a computer, and the edge calculation unit 140, the edge determination unit 150, and the edge detection unit 160 have their respective functions. And software such as a CPU (Central Processing Unit) and a memory for executing the software. In practice, the computer preferably corresponds to a microcomputer incorporated in the edge detection apparatus 101, but a stand-alone personal computer can also be used.
Such configurations in the edge calculation unit, the edge determination unit, and the edge detection unit are the same in the embodiments described later.

In the edge detection apparatus 101 according to the first embodiment having the above-described configuration, an operation for obtaining the edge position of the DUT 6 by the edge calculation unit 140 will be described below.
Here, as for the edge of the object 6 to be measured, it is considered that the edge 6b extends along the vertical direction (Z direction) as shown in FIG. Edge detection on line A in FIG. 22 showing a top view of the DUT 6 will be described.

The light emitted from the light source 1 of the light projecting system 110 passes through the first lens 3, the beam splitter 4, and the objective lens 5 to form a condensing spot 10 (FIG. 2a). As shown in FIG. 2a, when the object to be measured 6 does not exist at the position where the condensing spot 10 is formed, the reflected light does not exist, so the photodetector 8 detects nothing. When the first driving device 130 on which the device under test 6 is mounted is moved in the X direction and the device under test 6 reaches the position where the light condensing spot 10 is formed as shown in FIG. Of these, only the portion 11 irradiated on the DUT 6 is reflected to the light receiving system 120. The light reflected by the DUT 6 passes through the objective lens 5, is reflected by the beam splitter 4, and is collected on the photodetector 8 by the second lens 7. Therefore, the amount of reflected light can be detected by the photodetector 8. At this time, the amount of reflected light detected by the photodetector 8 reflects the size of the portion 11 irradiated on the object 6 to be measured.

Further, by moving the first driving device 130 in the X direction, as shown in FIG. 2 c, the condensed spot 10 completely irradiates the object to be measured 6, and the reflected light amount detected by the photodetector 8 is , Larger than in the case of FIG. Here, when the surface 6c of the DUT 6 is a mirror surface, even if the first driving device 130 is further moved in the X direction from the state of FIG. It becomes. On the other hand, the surface 6c (measurement surface) of the workpiece 6 to be processed by the wire electric discharge machine is not a perfect mirror surface but a rough surface, so that the first driving device 130 is further moved in the X direction from the state of FIG. When moved, the amount of light received by the photodetector 8 fluctuates. Therefore, in the end, the edge calculation unit 140 acquires a waveform like the reflected light amount characteristic 12 shown in FIG. 3 based on the received light amount obtained from the photodetector 8 and the amount of movement of the stage obtained from the first driving device 130. To do.

Further, the edge calculation unit 140 detects the peak intensity 13 from the reflected light quantity characteristic 12, and obtains the intersection 15 between the intensity threshold 14 obtained from the peak intensity 13 and the reflected light quantity characteristic 12 as the edge position OA. Here, the intensity threshold 14 is, for example, 50% of the peak intensity 13, but is not limited to this and can be arbitrarily set.

In the above description, as described above, the surface 6c of the object 6 to be processed by the wire electric discharge machine is a rough surface, and in the above description, the edge 6b of the object 6 is vertical. The edge 6b of the measured object 6 to be processed has a slightly gentle shape. For this reason, for example, when the surface 6c of the DUT 6 is scanned with the focused spot 10 along the line A in the X direction in FIG. 22, the reflected light quantity characteristic 12 obtained by the edge calculator 140 is a solid line in FIG. As shown. Further, the reflected light quantity characteristics 12 when measured at different positions in the Y direction as in the lines B and C in FIG. 22 are shown in FIG. 4 due to slight differences in the surface 6c and side surfaces of the object 6 to be measured. As shown by the broken line, the peak intensity and the peak position are slightly different from those shown by the solid line. For this reason, an error occurs at the position of the intersection 15 between the intensity threshold 14 obtained from the peak intensity 13 and the reflected light amount characteristic 12, and an error also occurs at the detected edge position.

Therefore, when the M spots in the Y direction are scanned in the X direction by the condensing spot 10, the reflected light quantity characteristics 12a, the reflected light quantity characteristics 12b, the reflected light quantity are reflected in each of the M places, for example, as shown in FIG. Characteristics 12c,... Are obtained.
Here, when the mth reflected light quantity characteristic 12 is Im (x), I (x) obtained by averaging the reflected light quantity characteristics 12 is obtained as represented by the following formula (1), and the edge of the object 6 to be measured is obtained. By calculating the edge position of 6b, the measurement error of the edge position can be reduced.

I (x) = {I ₁ (x) +... + Im (x) +... + I _M (x)} / M (1)

In addition, each edge position xm of the measurement object 6 corresponding to each reflected light quantity characteristic 12 obtained in each line scanning the surface 6c of the measurement object 6 in the X direction with the focused spot 10 is measured, and the following As shown in Expression (2), each edge position xm may be averaged to obtain the final edge position x.

x = {x ₁ + ... + xm + ... + x _M } / M (2)

Next, consider a case where a part of the edge 6b of the device under test 6 is missing as shown in FIG.
As already described, the measured object 6 processed by the wire electric discharge machine may have a part of the edge 6b of the measured object 6 chipped inward as shown in FIG. This is a phenomenon peculiar to the measured object 6 processed by the wire electric discharge machine.
Here, it is assumed that the edge 6b of the device under test 6 is vertical as shown in FIG. 24a, and the surface 6c of the device under test 6 is a rough surface. In this case, for the lines A to C (FIG. 23) scanned by the condensed spot 10 in the X direction, the edge calculation unit 140 obtains the reflected light amount characteristic 12c from the reflected light amount characteristic 12a as shown in FIG. The edge positions OA, OB, and OC are detected. As shown in FIG. 5, the edge position OA and the edge position OC in the line A and the line C coincide with the edge O1 in FIG. 23, but the edge position OB in the line B is affected by the lack of the edge 6b. Compared to the edge positions OA and OC, the reflected light amount characteristic 12b is also shifted backward compared to the reflected

light amount characteristics

12a and 12c.

Here, it is assumed that the reflected light quantity characteristics 12a to 12c obtained by the edge calculation unit 140 are averaged according to the above-described equation (1) by scanning the lines A to C. The averaged reflected light amount characteristic 12d is as shown in FIG. The peak intensity 13 is detected from the reflected light quantity characteristic 12d, and the intensity threshold value 14 is determined from the peak intensity 13 in the same manner as the edge position is detected from the reflected light quantity characteristics 12a to 12c of the lines A to C described above. The edge position O2 is calculated from the intersection of the intensity threshold 14 and the reflected light quantity characteristic 12d.

However, the edge 6b of the object 6 to be actually detected is an edge O1 different from O2, and if the reflected light quantity characteristics 12a to 12c are simply averaged as shown in FIG. When a part of the edge 6b of the measurement object 6 has a chip, the position of the true edge 6b of the object to be measured 6 is erroneously detected due to the influence of the edge chip.

That is, it is necessary to exclude characteristics such as line B, for example. For example, in cutting or the like, a protrusion called “burr” occurs on the edge to be detected, but no “burr” occurs in the measured object 6 processed by the wire electric discharge machine. However, since the edge 6b may be chipped toward the inside of the DUT 6 with respect to the edge 6b to be detected, it is necessary to detect and exclude only abnormal edges that are largely chipped inside.

In the following, the edge determination unit 150 and the edge detection unit 160 of the edge detection apparatus 101 according to the first embodiment detect and exclude only the abnormal edges that are largely missing on the inside, and detect the original edges. The operation will be described with reference to the flowchart of FIG.

Assume that M lines different in the Y direction perpendicular to the X direction are measured with the scanning direction of the DUT 6 by the focused spot 10 as the X direction.
First, in step 300, the edge calculation unit 140 causes the edge position {x1 of the object 6 to be measured in each line from the reflected light amount characteristic 12 {I1,... Im,. ,..., Xm,.
In the next step 310, the edge calculation unit 140 uses the edge position {x1,... Xm,..., XM} calculated in step 300 by the edge position minimum value xmin = Min (x1. xm,..., xM) are detected.
Next, the process proceeds to step 320, where the edge calculation unit 140 uses the edge position {x1,... Xm,..., XM} of each line and the difference bm = the minimum edge position value xmin calculated in step 310. xm−xmin is calculated and output to the edge determination unit 150.

In the next step 330, the edge determination unit 150 compares the threshold value xth preset in the edge determination unit 150 with the difference value bm calculated by the edge calculation unit 140 in step 320, and the difference value bm Exclude all edges that are greater than xth or greater than xth. Then, the edge determination unit 150 outputs the reflected light quantity characteristic 12 {... Im,...} Corresponding to the remaining difference value bm not excluded to the edge detection unit 160.

Next, the process proceeds to step 340, where the edge detection unit 160 calculates I (average) = average (..., Im,...) Obtained by averaging the remaining reflected light quantity characteristics 12. Then, the final edge position is calculated from the averaged I (average), and the edge calculation is completed.

With the configuration as described above, it is possible to reduce measurement errors due to slight fluctuations in the edge shape and surface state of the DUT 6. In the present embodiment, in particular, even when a part of the edge 6b of the object 6 processed by the wire electric discharge machine is missing in the inner direction of the object 6, such edge detection values are excluded. Therefore, it is possible to detect the original edge more accurately than in the prior art.

In the present embodiment, as described above, an example in which three locations of the DUT 6 are measured has been described, but the number of measurement points is not particularly limited as long as it is two or more locations.
In the present embodiment, the edge position is calculated based on the intensity threshold value 14 obtained from the peak intensity 13 of the reflected light amount characteristic 12 when the edge 6b is obtained. However, the absolute value of the reflected light amount is used as the intensity threshold value. It may be set to 14.

Further, in the first embodiment, as shown in FIG. 22, an example in which the edge 6b to be measured in the DUT 6 is parallel to the Y axis in the first driving device 130 has been shown, but it is shown in FIG. As described above, when the edge 6b to be measured in the device under test 6 is tilted with respect to the Y axis of the first drive device 130, that is, the device under test 6 is tilted with respect to the Y axis of the first drive device 130. Thus, even when mounted on the first drive device 130, the first embodiment can be applied. In this case, if M points are measured in the Y-axis direction assuming that the object to be measured 6 is scanned with the condensing spot 10 in the X direction of the first driving device 130, positions in the Y direction {y1,... Ym,. .., YM} and edge positions {x1,... Xm,..., XM} calculated at each point in the Y direction are plotted as shown in FIG. For the obtained points in the Y direction {y1,... Ym,..., YM} and edge positions {x1,. Thus, the approximate straight line 20 as shown in FIG. 9 can be calculated, and can be expressed by the following equation (3). Here, a and b are the slope and intercept of the approximate line 20.

X = a × Y + b (3)

As shown in FIG. 22, when the edge 6 b to be measured of the DUT 6 is parallel to the Y axis in the first driving device 130, the edge positions in the Y direction are averaged by the expressions (1) and (2). Although the converted value is a constant, as shown in FIG. 8, when the DUT 6 is mounted on the first driving device 130 with the Y axis tilted, the edge position xi with respect to a specific position yi in the Y direction. Is represented by the following formula (4).

x _i = a × y _i + b (4)

Further, the abnormal data due to the lack of the edge 6b of the DUT 6 is obtained by calculating the edge position xi ′ as the edge position calculated at the position yi in the Y direction, and xi as the ideal edge position obtained from the approximate straight line 20. Then, xi′−xi is calculated, and when the absolute value of the difference value is larger than a threshold value preset in the edge determination unit 150, the reflected light quantity characteristic 12 including the edge is removed. Just do it.

In the first embodiment described above, the Y-direction position {y1,... Ym,..., YM} and the edge position {x1,... Xm,. Although this example is shown, the present embodiment can be applied to the case of a curve instead of a straight line by design, and it is also possible to perform data processing by fitting measurement data of the curve.

Embodiment 2. FIG.
In the first embodiment described above, the method of detecting the edge 6b of the DUT 6 from the reflected light quantity characteristic 12 has been described. However, in the edge detection apparatus 102 in the second embodiment shown in FIG. A method of detecting the edge position from the calculated differential waveform is adopted.

The basic configuration of the edge detection apparatus 102 in the second embodiment is the same as the configuration of the edge detection apparatus 101 in the first embodiment described above, but the edge calculation unit 140, the edge determination unit 150, and the edge detection unit 160 are different. Instead, an edge calculation unit 142, an edge determination unit 152, and an edge detection unit 162 are provided. The edge calculation unit 142, the edge determination unit 152, and the edge detection unit 162 perform operations different from those of the edge calculation unit 140, the edge determination unit 150, and the edge detection unit 160 as described below.
The other components in the edge detection apparatus 102 in the second embodiment are the same as those in the first embodiment, and a description thereof is omitted here. Therefore, only operations of the edge calculation unit 142, the edge determination unit 152, and the edge detection unit 162 will be described below.

Also in the edge detection apparatus 102 in the second embodiment, for example, in the case of the first embodiment, when the measurement object 6 in which a part of the edge 6b of the measurement object 6 is missing is measured as shown in FIG. Similarly to the above, the reflected light quantity characteristics 12a to 12c shown in FIG. 5 are obtained.
In the edge detection apparatus 102 according to the second embodiment, the edge calculation unit 142 calculates the differential waveforms 16a to 16c of the reflected light quantity characteristics 12a to 12c as shown in FIG. 11, and the differential waveforms 16a to 16c obtained. Edge positions OA to OC are detected from the x coordinate of the peak value.

However, even when the differential waveforms 16a to 16c are used, as in the case of the first embodiment, and as shown in FIG. Compared to the edge positions OA and OC, the characteristic is shifted backward. Therefore, it is necessary to exclude such an abnormal edge also in the edge detection apparatus 102 in the second embodiment. Hereinafter, an operation of excluding abnormal edges by the edge determination unit 152 and the edge detection unit 162 and detecting an original edge will be described with reference to the flowchart of FIG.

Here, a case is considered in which the scan direction of the focused spot 10 with respect to the object to be measured 6 is the X direction, and M different scan lines in the Y direction orthogonal to the X direction are measured.
First, in step 400, the edge calculation unit 142 causes the reflected light quantity characteristics 12 {I1,... Im,..., IM} in each scan line to be differentiated waveforms 16 {D1,. } Is calculated.
In the next step 410, the edge calculation unit 142 calculates the edge positions {x1,... Xm,..., XM} of each scan line from the peak value of the differential waveform 16.
Next, in step 420, the edge computing unit 142 uses the edge position {x1, x2,... Xm} calculated in step 410 to determine the minimum edge position value xmin = Min (x1... Xm,. .., XM) is detected.
Next, in step 430, the edge calculation unit 142 determines the difference bm between the edge position {x1,... Xm,..., XM} of each scan line and the minimum value xmin of the edge position calculated in step 420. = Xm−xmin is calculated and output to the edge determination unit 152.

In the next step 440, the edge determination unit 152 compares the threshold value xth preset in the edge determination unit 152 with the difference value bm calculated in step 430, and the difference value bm is greater than xth or greater than or equal to xth. Exclude all edges. Then, the edge determination unit 152 outputs the reflected light amount characteristic 12 {... Im,...} Corresponding to the remaining edges that are not excluded to the edge detection unit 162.

Next, proceeding to step 450, the edge detection unit 162 calculates I (average) = average (... Im (...) Obtained by averaging the remaining reflected light quantity characteristics 12.
In the next step 460, the edge detector 162 calculates a differential waveform 16-2 obtained by differentially calculating the averaged reflected light amount characteristic 12-2.
In the next step 470, the edge detection unit 162 calculates the final edge position from the peak value of the differential waveform 16-2 and ends the edge calculation.

The edge detection device 102 in the second embodiment as described above can achieve the same effect as the edge detection device 101 in the first embodiment, and even when the edge 6b of the device under test 6 is missing. Thus, the original edge 6b can be detected more accurately than in the prior art.
In the second embodiment, an example in which three scan lines in the Y direction are measured has been described, but the number of measurement points is not particularly limited as long as it is two or more.

In the first embodiment and the second embodiment, the minimum value of the edge position is obtained from the edge position of each scan line. However, the moving direction of the first driving device 130 and the rise and fall of the reflected light amount characteristic 12 are described. Depending on the case, the maximum value may be obtained instead of the minimum value. In short, the outermost edge portion of the DUT 6 may be detected. Further, a reference value such as the second smallest value may be determined instead of the minimum value or the maximum value.

Also in the second embodiment, the data processing in the case where the edge 6b to be measured in the device under test 6 is inclined with respect to the Y-axis direction of the first drive device 130 as shown in FIG. It can be carried out in the same manner as described above.

Embodiment 3 FIG.
In the first embodiment and the second embodiment, the method of excluding an abnormal edge in which a part of the edge 6b of the object to be measured 6 is missing has been described. In this third embodiment, the object to be measured shown in FIG. As shown in the side view of the measurement object 6, an edge exclusion method in the case where the cross-sectional shape at the intersection of the edge 6b and the surface 6c is gentle (hereinafter simply referred to as “smooth edge”) will be described.

FIG. 13 shows the configuration of the edge detection apparatus 203 according to the third embodiment. The basic configuration of the edge detection device 203 is the same as the configuration of the

edge detection devices

101 and 102 of the first and second embodiments described above, but the edge calculation unit 142 and the edge determination unit described in the second embodiment. Instead of 152 and the edge detection unit 162, an edge calculation unit 143, an edge determination unit 153, and an edge detection unit 163 are provided. The edge calculation unit 143 generates the differential waveform 16 from the reflected light quantity characteristic 12 in the same manner as the edge calculation unit 142 in the second embodiment, but the edge determination unit 153 and the edge detection unit 163 are described below. Operations different from those of the edge determination unit 152 and the edge detection unit 162 are performed. Since the other components are the same as those in the first and second embodiments, the description thereof is omitted here, and the edge calculation unit 143, the edge determination unit 153, and the edge detection provided in the third embodiment are omitted. Only the operation of the unit 163 will be described.

First, problems in the case where the edge is gentle in the edge detection of the DUT 6 will be described.
When the edge 6b of the DUT 6 is gentle, the reflected light quantity characteristic 12 obtained by the edge calculation unit 143 is calculated from the peak intensity 13 with the output change gradually changing as shown by the solid line in FIG. O2 is detected as the edge position. On the other hand, when the edge 6b of the DUT 6 is vertical, the reflected light quantity characteristic 12 is as shown by a broken line in FIG. 14, and the edge position obtained from the peak intensity 13 is detected as O1. Therefore, when the edge is gentle with respect to the edge position, an error of Δx = O2−O1 occurs. Further, when an error is superimposed on the reflected light amount characteristic 12, the detected edge 6b has a larger error as the slope of the rising portion of the reflected light amount characteristic 12 becomes gentler.
For this reason, in order to reduce the edge position error due to the “smoothness” of the edge cross-sectional shape, that is, when the edge is gentle, the rising portion of the reflected light amount characteristic 12 is a gentle edge, that is, the differential waveform 16 as shown in FIG. It is necessary to provide a differential threshold 17 and to exclude edges having a small differential peak value below the differential threshold 17.

Next, the edge calculation unit 143, the edge determination unit 153, and the edge detection unit 163 included in the edge detection device 203 according to the third embodiment excludes the gently shaped edge as an abnormal edge, and the object to be measured The operation of detecting the original edge 6b in FIG. 6 will be described below with reference to the flowchart of FIG.

Here again, let us consider a case where the scanning direction of the focused spot 10 with respect to the object 6 to be measured is the X direction and different M scan lines in the Y direction perpendicular to the X direction are measured. In addition, the edge calculator 143 generates the differential waveform 16 from the reflected light amount characteristic 12 in the same manner as the edge calculator 142.

First, in step 500 in FIG. 16, the edge calculation unit 143 determines the differential waveform 16 {D1,1 from the reflected light quantity characteristics 12 {I1, ... Im, ..., IM} obtained by the scanning operation of each scan line. ... Dm,..., DM} are calculated, and the peak value {A1,... Am,. Output.

Next, in step 520, the edge determination unit 153 determines the differential threshold Ath preset in the edge determination unit 153 and the peak value {A1,... Am,. AM} and excludes all edges corresponding to values below the differentiation threshold Ath. Then, the edge determination unit 153 outputs the reflected light quantity characteristic 12 {... Im,...} Corresponding to the remaining edges that are not excluded to the edge detection unit 163.

In the next step 530, the edge detection unit 163 calculates I (average) = average (... Im (...) Obtained by averaging the reflected light quantity characteristics 12 corresponding to the remaining edges, In step 540, a differential waveform 16-3 obtained by differentiating the averaged reflected light amount characteristic 12-3 is calculated.

In the next step 550, the edge detection unit 163 calculates the final edge position from the peak value of the differential waveform 16-3, and ends the edge calculation.

As described above, according to the configuration of the edge detection device 203 in the third embodiment, the same effect as that of the edge detection device 101 in the first embodiment can be obtained, and the edge 6b in the object to be measured 6 can be obtained. Even in a gentle case, since such a gentle edge can be excluded, the original edge 6b of the DUT 6 can be detected with higher accuracy than in the prior art. .

In the third embodiment, the edge is calculated from the peak value of the differential waveform 16-3 in order to obtain the final edge position. However, the edge position is determined by the intensity threshold 14 obtained from the peak intensity 13 of the reflected light amount characteristic 12. May be calculated.

Embodiment 4 FIG.
In the first to third embodiments described above, the method of excluding abnormal edges such as when the edge 6b is missing or the edge cross section is gentle has been described. Here, however, the reflected light quantity characteristic 12 with low edge detection accuracy is excluded. A method will be described.

FIG. 17 shows the configuration of the edge detection device 104 of the fourth embodiment. The basic configuration of the edge detection device 104 is the same as the configuration of the edge detection devices 101 to 203 in the first to third embodiments described above, but the edge calculation unit 140, the edge determination unit 150, and Instead of the edge detection unit 160, an edge calculation unit 144, an edge determination unit 154, and an edge detection unit 164 are provided. The edge calculation unit 144, the edge determination unit 154, and the edge detection unit 164 perform different operations from the edge calculation unit 140, the edge determination unit 150, and the edge detection unit 160, as will be described below. The other components are the same as those in the first embodiment and the like are not described here, and the operations of the edge calculation unit 144, the edge determination unit 154, and the edge detection unit 164 provided in the fourth embodiment are omitted. Only will be described.

First, problems peculiar to the workpiece 6 processed by the wire electric discharge machine will be described.
In Embodiments 1 to 3, the surface 6c of the object 6 to be measured has been shown as a rough surface. However, the object 6 to be processed by the wire electric discharge machine has a rough surface 6c and the object to be measured. When the object 6 is observed from the upper surface, streaky irregularities 18 may be observed as shown in FIG. This is caused, for example, by the presence of the convex portion 18a or the concave portion 18b as shown in FIG. 19 which is a cross section taken along the line AA ′ of FIG. When the reflected light amount characteristic 12 in the vicinity of the slope of the convex portion 18a and the concave portion 18b of the device under test 6 is measured, the reflected light returning to the light receiving system 120 side is received at the flat portion 6d of the surface 6c of the device under test 6 shown in FIG. In many cases, the light is scattered at the convex portion 18a and the concave portion 18b, and the light returning to the light receiving system 120 is reduced. For this reason, as shown in FIG. 20, the reflected light quantity characteristic 12-4 having a large peak intensity 13 and the reflected light quantity characteristic 12-5 having a small peak intensity 13 coexist depending on the measurement position in the Y-axis direction. In the reflected light quantity characteristic 12-5 having a small peak intensity 13, the SN ratio, which is the ratio of the received light signal to the noise component, is deteriorated, so that the edge position detection accuracy is lowered.
Therefore, it is necessary to monitor the peak intensity 13 of the reflected light quantity characteristic 12, provide a peak intensity threshold 19 for the peak intensity 13, and exclude the reflected light quantity characteristic 12 having a peak intensity 13 smaller than the peak intensity threshold 19.

The edge calculation unit 144, the edge determination unit 154, and the edge detection unit 164 included in the fourth embodiment perform an operation of detecting the original edge 6b by excluding the edge whose edge position detection accuracy is low as described above. . Below, this operation | movement is demonstrated with reference to the flowchart of FIG.

Here again, a case is considered where the scan direction of the focused spot 10 with respect to the object to be measured 6 is the X direction, and M different scan lines in the Y direction orthogonal to the X direction are measured.
First, in step 600 in FIG. 21, the edge calculation unit 144 acquires the reflected light amount characteristics 12 {I1,... Im,..., IM} from the photodetector 8 by the scanning operation of each scan line. In the next step 610, the peak intensity 13 {P1,... Pm,..., PM} of the reflected light quantity characteristic 12 is obtained and output to the edge determination unit 154.

In the next step 620, the edge determination unit 154 includes the peak intensity threshold value 19Pth preset in the edge determination unit 154 and the peak intensity 13 {P1,... Pm,. , PM}. In this comparison operation, the edge determination unit 154 excludes all the reflected light amount characteristics 12 having a peak intensity equal to or less than the peak intensity threshold 19Pth, and uses the remaining reflected light amount characteristics 12 {... Im,. To 164.

In the next step 630, the edge detection unit 164 calculates I (average) = average (..., Im,...) Obtained by averaging the remaining reflected light quantity characteristics 12.

In the next step 640, the edge detection unit 164 obtains a final edge position based on the intensity threshold 14 obtained from the peak intensity 13 of the averaged reflected light quantity characteristic 12, and ends the edge calculation.

As described above, according to the configuration of the edge detection device 104 in the fourth embodiment, the same effect as that of the edge detection device 101 in the first embodiment can be obtained, and the peak intensity 13 is further low in noise resistance. Therefore, the original edge 6b can be detected with higher accuracy than in the prior art.

Further, as described above, in the present embodiment, when calculating the final edge position, the edge position is obtained based on the intensity threshold 14 obtained from the peak intensity 13 of the averaged reflected light quantity characteristic 12. The edge position may be calculated from the peak value of the differentiated waveform 16 by performing a differentiation operation of the characteristic 12.

In the first to fourth embodiments described above, examples of measurement in air have been shown, but measurement in oil or water is also applicable.
In the first to fourth embodiments, an example in which one photodiode is used for the light receiving element of the photodetector 8 provided in the light receiving system 120 has been described. However, the edge is formed by using two or four divided photodiodes. It may be configured to detect the position.
In the first to fourth embodiments, the first driving device 130 is moved only in the X direction. However, the first driving device 130 is naturally applicable to the case where the first driving device 130 is moved in the Y direction.
In addition, the methods shown in the first to fourth embodiments are effective even when executed independently, but are more effective when used in appropriate combinations.

Embodiment 5. FIG.
In the edge detection devices 101 to 104 according to the first to fourth embodiments described above, the focused spot 10 irradiated from the light projecting system 110 to the measured object 6 is focused on the measured object 6 in advance. It assumes a structure that does not change. On the other hand, the edge detection apparatus according to the fifth to eighth embodiments described below includes a laser beam focusing function from the light projecting system 110 to the object 6 to be measured.
The basic configuration of the edge detection devices according to the fifth to eighth embodiments described below is the same as the configuration of the edge detection devices 101 to 104 according to the first to fourth embodiments described above. Therefore, the same reference numerals are assigned to the same components.

FIG. 25 shows a schematic configuration of the edge detection apparatus 201 according to the fifth embodiment of the present invention. As in the edge detection devices 101 to 104 described in the first to fourth embodiments, the edge detection device 201 particularly detects edges on a rough surface of a metal object 6 having a rough scattering surface, that is, a rough surface. It is a device that detects using the reflected light of laser light irradiated on a rough surface, and can be used for measuring the shape of a workpiece in electric discharge machining, cutting, grinding, or the like. The object to be measured 6 of the edge detector 201 is not limited to a metal object having a rough surface. Of course, the edge detector 201 is a mirror-like object to be measured that is not a rough scattering surface. It is applicable to.

Such an edge detection device 201 includes a light projecting system 110, a light receiving system 120, and a first drive device 130 as basic components, similar to the edge detection devices 101 to 104 in the first to fourth embodiments. , A second driving device 240, a focus detection unit 250, and an edge detection unit 260. Each of these components will be sequentially described below.

The light projecting system 110 is a component that condenses and irradiates laser light onto the DUT 6 as shown in FIG. 26, as with the edge detection devices 101 to 104 in the first to fourth embodiments. Basically, the light source 1 and the optical system are provided. The optical system of the light projecting system 110 includes a first lens 3 and an objective lens 5. The light source 1 is composed of a semiconductor laser. The light source 1, the first lens 3, and the objective lens 5 are accommodated in the lens barrel 2 so as to form a linear optical path. The lens barrel 2 is connected to the second driving device 240.

As described above, in the present embodiment, the light source 1, the first lens 3, and the objective lens 5 form a linear optical path, but the optical path shape is not limited to this. A beam splitter 4 constituting the light receiving system 120 is installed between the first lens 3 and the objective lens 5. In the light projecting system 110, the beam splitter 4 is merely an object that transmits light and does not perform an optical action. In the fourth to eighth embodiments, the beam splitter 4 is included in the light receiving system 120. However, as in the first to fourth embodiments described above, the beam splitter 4 may be included in the light projecting system 110.

In such a light projecting system 110, the light 51 emitted from the light source 1 is collimated by the first lens 3, then condensed by the objective lens 5, and the light beam 51 a (see FIG. 26) to form a focused spot 52. Note that FIG. 25 shows a state where only half of the focused spot 52 is present on the measurement surface 6 a of the object 6 to be measured.

The second driving device 240 is a mechanism that enables the projection system 110 to move together with the lens barrel 2 in the direction of the optical axis of the objective lens 5, that is, the irradiation direction indicated by the arrow b in FIG. That is, the second driving device 240 enables the light projecting system 110 to focus on the measurement surface 6 a of the DUT 6. In the present embodiment, the second driving device 240 moves the light projecting system 110 in the direction of the arrow b with respect to the object to be measured 6, but is not limited to this configuration, and the light projecting system 110 and the object to be measured 6. As long as it moves in the direction of the arrow b.

As shown in FIG. 27, the light receiving system 120 is an optical part that receives the reflected light on the measurement surface 6a of the light beam 51a collected by the light projecting system 110 onto the measurement surface 6a of the object 6 to be measured. Are provided with a photodetector 8 and an optical system. As shown in FIG. 28a, the photodetector 8 is a photodiode in which one light receiving surface arranged at one light receiving position 8a is divided into a plurality of detection units. In this embodiment, the light receiving surface is divided into four equal parts. It is a photodiode. The optical system in the light receiving system 120 includes the objective lens 5, the beam splitter 4, and the second lens 7, which are arranged in this order along the progress of the reflected light. In the present embodiment, the light receiving system 120 shares the same lens as the objective lens 5 of the light projecting system 110 as an objective lens. The beam splitter 4 reflects the reflected light that has passed through the objective lens 5 and makes it incident on the second lens 7. The second lens 7 is a condensing lens and condenses the reflected light on the light receiving surface at the light receiving position 8 a of the photodetector 8. The second lens 7 and the photodetector 8 are installed in the lens barrel 9. As described above, the beam splitter 4 is installed in the lens barrel 2 of the light projecting system 110, and the lens barrel 9 of the light receiving system 120 and the lens barrel 2 of the light projecting system 110 are orthogonal to each other. It is connected.

In the optical system of the light receiving system 120, the light receiving position 8a of the four-divided photodiode that is the light detector 8 is adjusted so as to have an imaging relationship with the position where the light beam from the light projecting system 110 is focused. That is, when the measurement surface 6a of the object to be measured 6 is at the condensing position of the light beam 51a from the light projecting system 110, the reflected light is imaged at the light receiving position 8a of the photodetector 8.

As shown in FIG. 27, the light receiving system 120 configured in this way emits reflected light 54 from a region 53 in the measurement surface 6 a of the object 6 to be measured among the condensing spots 52 by the light projecting system 110. The light is collimated by the objective lens 5 which is also a condensing lens of the system 110, reflected by the beam splitter 4, condensed by the second lens 7 at the center of the light receiving surface at the light receiving position 8 a of the photodetector 8, and the condensed spot 55. Form.

The first driving device 130 is a device that has a stage on which the object to be measured 6 is placed and moves the stage, that is, the object to be measured 6 in the X and Y directions orthogonal to each other on a plane. Here, the X and Y directions are directions orthogonal to the irradiation direction indicated by the arrow b, which is the moving direction of the light projecting system 110 by the second driving device 240. In the present embodiment, the first driving device 130 moves the object 6 to be measured with respect to the fixed light projecting system 110, but is not limited to this configuration, and the light projecting system 110, the object 6 to be measured, and the like. Any device that relatively moves in the X and Y directions may be used.

The focus detection unit 250 is a part that is electrically connected to the light detector 8, the first driving device 130, and the second driving device 240, and detects the in-focus position of the light projecting system 110 with respect to the object to be measured 6. Details will be described in the following explanation of operation.

The edge detection unit 260 is a part that is electrically connected to the focus detection unit 250 and the first driving device 130 and detects the edge of the DUT 6. Details will be described in the following explanation of operation.

The focus detection unit 250 and the edge detection unit 260 are actually implemented using a computer, and include software corresponding to each function and hardware such as a CPU (Central Processing Unit) and a memory for executing the software. It is configured.

The operation of the edge detection apparatus 201 configured as described above will be described below. In the following description, an example is described in which edge detection is performed by moving the DUT 6 in the X direction by the first driving device 130, but the same applies to the movement in the Y direction.

First, the principle of edge detection in the edge detection apparatus 201 will be described.
For convenience of explanation, first, a case where the reflectance and scattered radiation angle characteristics of the light beam do not change due to the change of the irradiation position of the light beam on the upper surface of the object to be measured will be considered. Specifically, a mirror surface without scattering, or a surface having a rough surface structure on the upper surface of an object to be measured, such as paper, is equal to or less than the wavelength structure of light. In addition, in order to distinguish the to-be-measured object which has such a surface from the to-be-measured object 6, in the description location here, it describes as a non-rough surface measured object.

In such a state, when the non-rough surface measurement object sufficiently separated from the edge is irradiated with the condensing spot 52, the shape of the condensing spot 55 on the photodetector 8 (quadrant photodiode) is The shape of the condensing spot 52 is reflected. That is, if the condensing spot 52 is circular, the condensing spot 55 is also circular.

In order to detect the edge, the non-rough surface measurement object is moved by the first driving device 130 in the X direction, and the non-rough surface measurement is performed by the light beam 51a irradiated to the non-rough surface measurement object from the light projecting system 110. The object is scanned so that the light beam 51a passes through the edge of the non-rough surface measurement object.

The reflected light reflected from the non-rough surface measurement object by the condensing spot 52 of the light beam 51 a is transmitted through the objective lens 5, reflected by the beam splitter 4, collected by the second lens 7, and detected by the photodetector 8. Is incident on the light receiving surface. The shape of the focused spot 55 on the light receiving surface of the photodetector 8 changes according to the region where the focused spot 52 of the light beam 51a is reflected by the non-rough surface measurement object. This is shown in FIGS. 28a to 28c.

FIG. 28a shows a state where the focused spot 52 is on only a part of the non-rough surface measurement object, and FIG. 28b shows a state where exactly half of the focused spot 52 is on the non-rough surface measurement object. FIG. 28 c shows a state where most of the focused spot 52 is on the non-rough surface measurement object. Here, on the light receiving surface of the photodetector 8 divided into four, the light reception intensity of the sum of the region 11 and the region 82 is I (A), and the light reception intensity of the sum of the region 83 and the region 84 is I (A B).

Here, in the non-rough surface measurement object, received light intensity I (A) and I (B) when the condensing spot 52 scans the upper surface of the cross section shown in FIG. 29A is shown in FIG. 29B. Since the received light intensity I (A) and the received light intensity I (B) are signals separated in the X direction, as shown in FIG. 29c, this difference signal, I (A) -I (B), is shown in FIG. A peak appears corresponding to the edge position of the cross section shown in FIG. The positions in the X direction at which these peaks appear are defined as edge positions.

Here, if the focused spot 52 on the non-rough surface measurement object is defocused (not focused), the received light intensity of the focused spot 55 on the light receiving surface of the photodetector 8 is I ′ ( A) and I ′ (B) are shown in FIG. 29d. Note that the received light intensities I ′ (A) and I ′ (B) correspond to the above-described received light intensities I (A) and I (B). Further, FIG. 29e shows a difference signal between the received light intensity I '(A) and I' (B).

As is clear from FIG. 29e, when the condensing spot 55 on the light receiving surface of the photodetector 8 is defocused, that is, when the light projecting system 110 is defocused with respect to the non-rough surface measurement object, the light receiving intensity. I ′ (A) and received light intensity I ′ (B) almost overlap each other in the X direction, and even if these difference signals are taken, the peak becomes small and the edge detection accuracy decreases. Thus, the fact that the light condensing position of the light projecting system 110 and the light receiving position 8a of the photodetector 8 of the light receiving system 120 with respect to the non-rough surface measurement object (the same applies to the object 6 to be measured) is in an imaging relationship. Important for edge detection.

Next, the focus adjustment of the light receiving system 120, in other words, the edge detection operation of the DUT 6 will be described.
Although the non-rough surface measurement object has been described above as an example, the edge detection apparatus 201 can perform focus adjustment even when the measurement object upper surface is a rough metal. This will also be described below.
When the measurement surface 6a of the object 6 to be measured is at a position where the light condensing spot 52 is minimum with respect to the light projecting system 110, it is referred to as “the light projecting system is focus-adjusted”. Similarly, when the measurement surface 6a of the object to be measured 6 and the photodetector 8 are in an imaging relationship, they are referred to as “the light receiving system is focus-adjusted”. In the present embodiment, as described above, the position of the light receiving surface of the photodetector (four-division photodiode) 8 is adjusted so as to have an imaging relationship with the position where the light beam from the light projecting system 110 is focused. Therefore, when the light projecting system 110 is focus-adjusted, the light receiving system 120 is also focus-adjusted. In this way, the state in which the light projecting system 110 and the light receiving system 120 are both focused is referred to as “the light projecting / receiving system is focus-adjusted”.

FIG. 30 shows a measurement arrangement position of the measurement surface 6a when the measurement surface 6a of the DUT 6 is scanned with the light beam 51a from the light projecting system 110. That is, the distance in the direction of the arrow b between the objective lens 5 of the light projecting system 110 and the measurement surface 6a of the object 6 to be measured is shown in the drawing by the measurement surface 6a (a), (b), (c). The focus detection unit 250 is changed by the second driving device 240 so that the object to be measured 6 is moved by the first driving device 130. The measurement surface 6a arranged at each position is scanned. The position (c) corresponds to the in-focus position of the light projecting system 110, and the position (a) corresponds to the most out-of-focus (defocus) position.

Under such a setting, the metal whose measurement surface 6a is a rough surface is scanned, and the sum of all signals obtained from the four detection units of the photodetector 8 by the focus detection unit 250 is measured. By measuring with respect to the feed distance X of 6, each signal waveform corresponding to the positions (a) to (c) is obtained as shown in FIG. As can be seen from these signal waveforms, the diameter of the condensing spot 52 of the light projecting system 110 becomes smaller and the signal waveform of the photodetector 8 also becomes smaller as the focus is adjusted from the positions (a) to (b) and (c). Reflecting the rough structure of the metal, it has a large amplitude.

As described above, the focus detection unit 250 changes the distance between the objective lens 5 of the light projecting system 110 and the measurement surface 6a of the measurement object 6 in the direction of the arrow b while changing the measurement surface of the measurement object 6. By repeatedly scanning 6a with the light beam 51a and finding the distance in the direction of arrow b where the amplitude intensity in the output signal from the photodetector 8 is the largest, the focus adjustment of the light projecting system 110 can be performed. . That is, by adopting such a method, it is possible to adjust the focus of the light projecting system 110 even for a metal whose measurement surface 6a is rough.

Further, the signal amplitude in FIG. 31 depends on whether or not the light projecting system 110 is focus-adjusted, and does not depend on whether or not the light-receiving system 120 is focus-adjusted. However, as described above, since the edge detection apparatus 201 is set in advance to the state where “the light projecting / receiving system is focus-adjusted”, the focus adjustment of the light receiving system 120 is also performed at the same time. Therefore, by adopting the above-described method, it is possible to adjust the focus of the light receiving system 120 even for a metal having a rough measurement surface 6a.

Note that the position of the four-divided detection unit in the photodetector 8 is moved in the plane, adjusted so that the condensed beam 55 is on one detection unit, and focused using the amplitude intensity of the one signal. Detection may be performed.

FIGS. 32a to 32e show measurement examples of edges in the metal object 6 having a rough measurement surface 6a obtained as described above. This edge detection operation is executed by the edge detection unit 260.
FIG. 32B shows signals I (A) and I (B) when the measurement surface 6a of the DUT 6 having a cross section as shown in FIG. 32A is scanned in a state in which the light projecting / receiving system is focused. This difference signal I (A) -I (B) is shown in FIG. 32c. A position X that gives peaks at both ends in FIG. 32 c corresponds to the edge positions at both ends of the DUT 6. Based on this edge position, the dimension of the DUT 6 can be measured.

Note that the signals I (A) and I (B) when the light projecting system 110 is focused but the light receiving system 120 is defocused are shown in FIG. 32d, and FIG. 32e shows the difference signal I ( A) -I (B). As is apparent from FIGS. 32d and 32e, when measuring the edge of the metal object 6 having a rough measurement surface 6a, the signal I (A) and the signal I (A) can be obtained when the light receiving system 120 is in the defocused state. The difference from the signal I (B) becomes small, and edge measurement becomes difficult.

Embodiment 6 FIG.
In the fifth embodiment, as described above, the focusing operation of the light projecting system 110 is performed by the second driving device 240, that is, in the state where the condensing spot 52 on the measurement surface 6 a of the object to be measured 6 is minimum, the edge Scan for detection. In contrast, the edge detection apparatus 202 according to the sixth embodiment performs scanning by defocusing the focused spot 52 by intentionally changing the size of the focused spot 52 on the measurement surface 6a after focusing. As shown in FIGS. 33a and 33b, the edge detection device 202 further includes a defocus mechanism 270 for this purpose. The other configuration of the edge detection device 202 is the same as that of the edge detection device 201. Therefore, only the portion related to the defocus mechanism 270 will be described below.

By providing the defocus mechanism 270, the size of the condensing spot 52 in the projection system 110 on the measurement surface 6a is changed without changing the distance between the objective lens 5 of the projection system 110 and the object 6 to be measured. That is, it can be defocused. As one of the methods, the defocus mechanism 270 changes the interval between optical elements disposed between the light source 1 and the objective lens 5. In the sixth embodiment, the defocus mechanism 270 defocuses the focused spot 52 by changing the distance a between the light source 1 and the first lens 3. Here, when a = a0 is set, the condensing position of the light beam 51a from the light projecting system 110 and the light receiving position 8a of the light receiving surface of the photodetector (four-division photodiode) 8 are in an imaging relationship. It shall be adjusted as follows. Before measuring the object 6 to be measured, for example, at the stage of assembling the edge detection device 202, it is easy to find the distance a0 that satisfies the above conditions by means such as accurately measuring the distance between the lenses.

In order to adjust the focus of the light receiving system 120, first, the distance between the light source 1 and the first lens 3 is set to a = a0. Thereafter, the focus position of the light projecting system 110 with respect to the DUT 6 is adjusted by the procedure described in the fifth embodiment. FIG. 33a shows a device configuration diagram at that time. Since a = a0 and “the light projecting / receiving system is focus-adjusted”, the focus of the light receiving system 120 is also adjusted.

When the condensing spot 52 of the light projecting system 110 is not too small, the noise due to the metal rough surface is small, and there is no problem even if edge detection is performed in a state where the light projecting / receiving system is in focus adjustment. On the other hand, if the light condensing spot 52 of the light projecting system becomes too small, the noise due to the metal rough surface increases, and the edge detection accuracy deteriorates. In such a case, after adjusting the focus of the light projecting / receiving system, the distance between the light source 1 and the first lens 3 is intentionally shifted from a = a0 by the defocus mechanism 270, and the light receiving system 120 is in the focused state. In this state, only the light projecting system 110 is set to the defocused state. The layout of the edge detection device 102 at that time is shown in FIG. 33b. For example, by setting the distance a> a0, the size of the condensing spot 52 of the light projecting system 110 on the measurement surface 6a of the object 6 to be measured is enlarged.

In this way, by enlarging the size of the focused spot 52, the following effects can be obtained in addition to the effects described in the fifth embodiment.
That is, when the light projecting system 110 is in the in-focus position, as shown in FIG. 32b, a sharp peak is seen in the received light intensity, but the condensing spot 52 of the light projecting system 110 is enlarged by the defocus mechanism 270. Thus, a signal obtained by integrating the reflection signals at the respective points in the light irradiation region is detected by the photodetector 8. Therefore, the fluctuation of the reflected signal due to the difference in the position of the measurement surface 6a of the DUT 6 is reduced, and the received light intensity has a gentle peak as shown in FIG. 34a. The waveforms of the signals I (A) and I (B) are gentle, but the signals I (A) and I (B) are left and right separated in the moving direction of the DUT 6. As shown in FIG. 34b, the difference signal I (A) -I (B) has a large peak at the edge position. Thus, the defocus mechanism 270 can reduce noise due to the metal rough surface and improve edge detection accuracy.

Further, when the condensing spot 52 from the light projecting system 110 is increased, the condensing spot 55 on the light receiving surface of the photodetector 8 is increased as shown in FIG. There is also an effect that a decrease in the amount of light due to can be reduced. That is, as shown in FIGS. 35a and 35b, the quadrant photodiode usually has an insensitive region 85 that is not sensitive to light at the boundary between the detection units. Therefore, as shown in FIG. 35a, when the condensing spot 55 is small, the ratio of the insensitive area 85 to the condensing spot 55 is large. On the other hand, as shown in FIG. 35b, by defocusing the light projecting system 110 and increasing the condensing spot 55, the ratio of the insensitive area 85 to the condensing spot 55 is reduced, and the light receiving areas 81 to 84 receive light. The amount of light emitted increases. Therefore, an effect of preventing a decrease in light amount due to the insensitive area can be obtained.

Embodiment 7 FIG.
In the above-described sixth embodiment, as a method for enlarging the condensing spot 52 from the light projecting system 110, the defocus mechanism 270 is provided as described above, and a method for changing the element spacing of the optical system in the light projecting system 110 is adopted. It was.
On the other hand, as shown in FIG. 36, in the edge detection device 203 of the seventh embodiment, the aperture diameter is increased in order to enlarge the focused spot 52 while maintaining the focus state in the light projecting system 110 and the light receiving system 120. A diaphragm mechanism 290 is provided. The aperture mechanism 290 has an aperture that restricts the light flux in the optical path of the light projecting system 110, whereby the same effect as in the sixth embodiment can be obtained. That is, the condensing spot 52 from the light projecting system 110 is enlarged by the effect of diffraction caused by reducing the aperture.

The method of providing the aperture mechanism 290 has an advantage that the structural change is less than the method of changing the element spacing of the optical system in the light projecting system 110. Further, since the measurement surface 6a of the object to be measured 6 is at the condensing position of the light beam 51a, even if the height of the object to be measured 6 fluctuates during edge detection, the position variation of the condensing spot 52 is small. There are also advantages.

It should be noted that the installation location of the diaphragm mechanism 290 is not limited between the objective lens 5 and the DUT 6 in the seventh embodiment.

Embodiment 8 FIG.
In the eighth embodiment, as shown in FIG. 37, a description will be given of an edge detection device 204 that can be applied to an object to be measured 6 that is disposed in a machining fluid 31 in, for example, wire machining discharge.
The edge detection device 204 has a structure further provided with a liquid-proof structure 280 with respect to the edge detection devices 201 to 203 in the fifth to seventh embodiments described above. Note that FIG. 37 shows a configuration example in which the edge detection device 201 shown in FIG. 25 is further provided with a liquid-proof structure 280, for example. In addition, when the edge detection device adopts a configuration in which the light projection system 110 and the light reception system 120 do not share the objective lens 5, the light projection system 110 is disposed on the exit side of the objective lens 5, and the light reception system 120 is disposed on the objective lens 5. A configuration including a liquid-proof structure 280 on each incident side can be employed.

The liquid-proof structure 280 is attached to the objective lens 5 side with a liquid-proof specification with respect to the lens barrel 2 of the light projecting system 110. The liquid-proof structure 280 is provided between the objective lens 5 and the measured object 6, and the reflected light 54 incident on the light receiving system 120 from the measured object 6 and the light beam 51 a irradiated from the light projecting system 110 to the measured object 6. Has a window 281 made of a transparent material. In such a liquid-proof structure 280, for example, the window 281 is immersed in the processing liquid 31.

The first driving device 130 is disposed outside the machining liquid 31 and moves the DUT 6 in the X direction, for example, or moves the edge detection device 204 in the X direction, for example. Other configurations are the same as those in the edge detection apparatus 201 described above.
According to the edge detection device 204 configured as described above, the following effects can be further obtained in addition to the effects described in the fifth to seventh embodiments.

That is, according to the edge detection device 204, it is possible to detect an edge by immersing a so-called optical head portion that performs edge detection of the DUT 6 in the processing liquid 31. More specifically, in a structure that does not have the liquid-proof structure 280, it is necessary to perform measurement so that the optical head portion of the edge detection device does not touch the processing liquid 31, and the edge passes through the processing liquid 31 from above the processing liquid 31. Measurement will be performed. In this case, there is a problem that the signal fluctuates due to the fluctuation of the interface between the machining liquid 31 and air, and accurate edge measurement cannot be performed. On the other hand, in order to eliminate the fluctuation of the signal, once the machining liquid 31 is discharged and measurement is performed, it takes time to discharge the machining liquid 31, and the machining droplet remaining on the edge portion of the object 6 to be measured is used. However, the problem of deteriorating measurement accuracy arises. Thus, the edge detection device that does not have the liquid-proof structure 280 has a problem.

On the other hand, according to the edge detection apparatus 204 of the eighth embodiment, the above-described problems can be solved, and high-speed and accurate edge measurement can be performed.

Embodiment 9 FIG.
In the above-described fifth to eighth embodiments, the edge detection devices 201 to 204 have been described with respect to an apparatus having a laser beam focusing function from the light projecting system 110 to the object 6 to be measured. An edge detection device obtained by adding the focusing function in the edge detection device 201 of the fifth embodiment to the edge detection device 101 of the first embodiment described above will be described.

FIG. 38 shows the configuration of the edge detection device 301 according to the ninth embodiment. This edge detection device 301 is different from the edge detection device 101 in the first embodiment shown in FIG. The focus detection unit 250 is added. Here, the second drive device 240 and the focus detection unit 250 are the same as those described in the fifth embodiment. The photodetector 8 is the same as that in the edge detection apparatus 201 of the fifth embodiment. As shown in FIG. 28a, one light receiving surface arranged at one light receiving position 8a is used as a plurality of detection units. This is a divided photodiode, and here is a photodiode in which the light receiving surface is divided into four equal parts.
As described above, the configuration of the edge detection apparatus 301 is a combination of the configurations already described, and thus description thereof is omitted here. Therefore, the operation of the edge detection apparatus 301 according to the ninth embodiment will be described below.

In the edge detection apparatus 301, the measurement object 6 is measured according to the following steps.
Step 1: The focus position to the upper surface of the DUT 6 in the light beam emitted from the light projecting system 110 is calculated.
Step 2: A surface 6c of the object 6 to be measured in the X-axis direction orthogonal to the edge 6b at a plurality of positions in the Y-axis direction along the edge 6b of the object 6 to be measured by the focused light beam having a small spot size. Scan.
Step 3: From the plurality of data obtained from the photodetector 8 by the scan, abnormal data is removed, averaged, and the like, and the edge position of the DUT 6 is detected.

The focus operation in Step 1 above, that is, the operation in the second drive device 240 and the focus detection unit 250 provided in the edge detection device 301 of the ninth embodiment will be described in detail below. This focus operation is the same as the operation in the edge detection apparatus 201 in the fifth embodiment described above. Therefore, the drawings referred to below are the same as the drawings referred to in the fifth embodiment.

FIG. 30 shows a measurement arrangement position of the measurement surface 6a when the measurement surface 6a of the DUT 6 is scanned with the light beam 51a from the light projecting system 110. That is, the distance in the direction of the arrow b between the objective lens 5 of the light projecting system 110 and the measurement surface 6a of the object 6 to be measured is shown in the drawing by the measurement surface 6a (a), (b), (c). The focus detection unit 250 is changed by the second driving device 240 and the focus detection unit 250 moves the object 6 to be measured by the first driving device 130. The measurement surface 6a disposed at each position is scanned. The position (c) corresponds to the in-focus position of the light projecting system 110, and the position (a) corresponds to the most out-of-focus (defocus) position.

As described above, the focus detection unit 250 changes the distance between the objective lens 5 of the light projecting system 110 and the measurement surface 6a of the measurement object 6 in the direction of the arrow b while changing the measurement surface of the measurement object 6. By repeatedly scanning 6a with the light beam 51a and finding the distance in the direction of arrow b where the amplitude intensity in the output signal from the photodetector 8 is the largest, the focus adjustment of the light projecting system 110 can be performed. . That is, by adopting such a method, it is possible to adjust the focus of the light projecting system 110 even for a metal whose measurement surface 6a is rough. The Z-direction position Zf of the stage at the focus position calculated here is stored in the memory.

The above is the operation in step 1 above. Note that the operations in step 2 and step 3 are the same as those described in the first to fourth embodiments, and a description thereof will be omitted here.

Then, by adjusting the position of the stage in the Z direction to the position Zf obtained in step 1, the measurement surface 6a of the object 6 to be measured can be placed at the just focus position, and the spot size on the measurement surface 6a is reduced. In the edge detection apparatus 301 according to the ninth embodiment, the spot size of the light beam irradiated onto the measurement surface 6a by the light projecting system 110 is reduced, and then the measurement object 6 described in the first to fourth embodiments is used. Since the operation of excluding abnormal edges is performed, the edge detection device 301 according to the ninth embodiment can detect the edge position of the DUT 6 more accurately than in the past.

Embodiment 10 FIG.
In the edge detection apparatus 301 according to the ninth embodiment, there is a concern that the measurement time becomes long because the light beam is scanned a plurality of times at a plurality of positions along the edge 6b of the object 6 to be measured. Therefore, the edge detection apparatus according to the tenth embodiment can shorten the measurement time as compared with the edge detection apparatus 301 according to the ninth embodiment.
The configuration of the edge detection device 302 according to the tenth embodiment is the same as that of the edge detection device 301 according to the ninth embodiment described above, but the second drive device 240 and the focus detection unit 250 will be described below. The operation different from that in the ninth embodiment is performed.

The edge detection device 302 according to the tenth embodiment measures the DUT 6 in the following steps.
Step 1: The focus position to the upper surface of the DUT 6 in the light beam emitted from the light projecting system 110 is calculated.
Step 2: The second drive device 240 defocuses the light beam that the projection system 110 irradiates the measurement surface 6a of the object 6 to be measured.
Step 3: The edge position of the DUT 6 is obtained with the defocused light beam having a large spot size, and the edge position is set to X0.
Step 4: A focused light beam with a small spot size is used to scan only in the vicinity of the edge position X0 in the X-axis direction orthogonal to the edge at a plurality of positions in the Y-axis direction along the edge of the object 6 to be measured. I do.
Step 5: Abnormal data is removed, averaged, etc. from a plurality of data obtained from the photodetector 8 by the scan, and the edge position of the DUT 6 is detected.

According to the above operation, the edge detection device 302 according to the tenth embodiment narrows the width of scanning in the X-axis direction to the vicinity of the edge position X0 in step 4, so the edge detection device 301 according to the ninth embodiment. The measurement time can be shortened compared to.

Since Step 1 and Step 5 correspond to Step 1 and Step 2 described in the ninth embodiment, description thereof will be omitted, and hereinafter, Step 2 to Step 4 will be described below. ,explain in detail.

First, step 2 will be described.
The projection system 110 is moved by the second driving device 240 by the distance Za from the Z stage position Zf obtained in step 1 described above, and the light beam irradiated on the measurement surface 6a of the object 6 to be measured is defocused. By defocusing the light beam, the spot size of the light beam is enlarged. The amount of enlargement of the spot size with respect to the defocus amount depends on the F value (aperture value) of the light projecting system 110, but consider the case of F = 8, for example. The size of the focused spot at the focus position is evaluated with an air disk that is the diameter of the dark ring of the diffraction image. For a wavelength λ = 0.6 μm, the Airy disk diameter is

φAiry = 2 × 1.22 × λ × F
Therefore, φAiry = 12 μm.

On the other hand, when the spot size φdefocus at the defocus position is estimated geometrically,

φdefocus = Za ÷ F
It is. Assuming that the distance Za = 200 μm, φdefocus = 25 μm, and the spot size expands to about twice that during just focus. Further, when the distance Za = 400 μm, φdefocus = 50 μm.

Next, step 3 will be described.
As shown in FIG. 39, the DUT 6 is scanned in the X-axis direction with the large spot size light beam 350 defocused in the above step 2. In FIG. 39, the light beam 350 is shown to be scanned in the + X direction, but the light beam 350 is stationary, and the effect is the same even when the DUT 6 is scanned in the −X direction.

FIG. 40 shows a graph of the signal intensity obtained by the photodetector 8 with such a defocused light beam 350. Since the beam size of the light beam 350 is large, a smooth graph with little noise is obtained, but the gradient of the graph near the edge of the DUT 6 is small.
Further, by this scan, the edge position of the DUT 6 obtained from the edge calculation unit 140, the edge determination unit 150, and the edge detection unit 160 by the method described in the first to fourth embodiments is set to X0.

As already described, the side surface of the object to be measured 6 has irregularities with a height of several μm with a period of several μm due to machining traces caused by discharge pulses, and accordingly, at the boundary between the surface 6 c and the side surface of the object to be measured 6. A certain edge portion also fluctuates in the order of several μm. On the other hand, the surface 6c of the DUT 6 is not subjected to electric discharge machining, and the polished state before electric discharge machining remains. Therefore, as shown in FIG. 18 and FIG. 19, the surface 6 c of the object to be measured 6 has unevenness 18 on the order of several μm to several tens of μm. Because of these irregularities, spot irradiation with a light beam having a small beam size with a diameter of several μm may cause light rays to be reflected outside the objective lens 5, and the noise of the signal obtained by the photodetector 8 is large. Become.

When the beam size is increased in the Y direction, which is the direction of the edge of the DUT 6, the same result as a signal obtained when scanning at a plurality of different positions in the Y direction is simultaneously performed with a light beam having a small beam size can be obtained. it can. Therefore, noise of the signal obtained by the photodetector 8 can be reduced, and a smooth graph can be obtained as shown in FIG. In other words, a single scan using a light beam with a large spot size has a noise reduction effect equivalent to a process in which scans at different positions in the Y direction using a light beam with a small spot size are averaged.

On the other hand, when the beam size increases in the X direction, which is the scanning direction, the slope of the graph near the edge decreases. This is because if the noise component due to edge chipping or irregular reflection on the surface 6c of the object 6 to be measured is removed, the function C (x) of the received light intensity with respect to the scanning position x of the light beam is the intensity distribution function A ( This is because it is a convolution integral of x) and the reflected light intensity function B (x) by irradiation of the point light source. If the inclination of the graph is small, the accuracy of determining the edge position is deteriorated.

The edge position X0 obtained by beam scanning with a large spot size cannot be determined with an accuracy of, for example, 1 μm or less because the beam size is large in the X direction. Since the noise of the obtained signal is reduced, it does not deviate significantly from the true edge position Xt. This situation is schematically shown in FIG. 41 and FIG. FIG. 41 schematically shows the probability that the error amount appears with respect to the error amount of the edge position calculated by scanning the light beam with a small spot size once. FIG. 42 is a schematic diagram similar to the case where a light beam having a large spot size is scanned once.

Next, step 4 will be described.
FIG. 43 and FIG. 44 show schematic diagrams of scanning a light beam having a small spot size at a plurality of positions in the Y direction. When the edge position is completely unknown, it is necessary to scan with a large width in the X direction as shown in FIG. 43 in order to prevent the true edge position from deviating from the scan range. However, if the scan range in the X direction is large, the measurement takes time.

According to the findings of the applicant's experiment, in order to perform sufficient averaging to reduce the noise of the signal obtained by the photodetector 8, X positions at 50 different positions in the Y direction, for example, at intervals of 10 μm are used. Need to scan in the direction. When the edge position is unknown, it is necessary to set the scan width in the X direction to 100 μm, for example. Here, assuming that 100 μm is scanned in 10 seconds, for example, it takes 500 seconds to complete this measurement.

On the other hand, if scanning is performed only around the edge position X0 obtained in step 3, the true edge does not deviate from the scanning range even in a narrow scanning range as shown in FIG. For example, if the maximum error between the edge position X0 calculated in step 3 and the true edge position Xt is 5 μm, the scan range can be narrowed to 10 μm. In this case, the time required for the measurement can be shortened to 50 seconds, which is 1/10 of the above-described scan range of 100 μm.

As described above in detail, in the edge detection device 302 according to the tenth embodiment, after the focus position is first detected, the light beam is defocused on the object 6 to be measured, and the light beam having a large spot size is used. A rough edge position X0 is measured. Thereafter, the light beam is focused on the object 6 to be measured, and scanning is performed only in the vicinity of the edge position X0 with the light beam having a small spot size. By performing such an operation, the edge detection apparatus 302 according to the tenth embodiment has an effect that the measurement time can be further shortened in addition to the effects described in the ninth embodiment.

In the ninth and tenth embodiments described above, the photodetector 8 uses a photodiode in which one light receiving surface is divided into a plurality of detectors. However, the present invention is not limited to this, and one photo detector is used for each light receiving element. A diode may be used.

It is to be noted that, by appropriately combining arbitrary embodiments of the various embodiments described above, the effects possessed by them can be produced.
Although the present invention has been fully described in connection with preferred embodiments with reference to the accompanying drawings, various variations and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as being included therein, so long as they do not depart from the scope of the present invention according to the appended claims.

The present invention can be applied to an edge detection device that detects an edge position in an object to be measured based on reflected light.

1 light source, 4 beam splitter, 5 objective lens, 6 object to be measured, 8 light detector,
12 reflected light quantity characteristics, 16 differential waveform,
101 to 104 edge detection device, 110 light projecting system, 120 light receiving system,
130 first driving device, 140 edge calculation unit, 150 edge determination unit,
160 edge detector,
201-204 edge detection device, 240 second drive device,
250 focus detection unit, 260 edge detection unit, 270 defocus mechanism,
280 Liquid-proof mechanism, 281 window,
301, 302 Edge detection device.

Claims

An edge detection device (101 to 104, 201 to 204, 301, 302) for detecting an edge of a device under test (6),
A light projecting system (110) for irradiating the object to be measured with a light beam;
A light receiving system (120) that receives light emitted from the light projecting system and reflected by the object to be measured, and having a photodetector (8) that detects the reflected light;
A first driving device (130) for relatively moving the object to be measured and the light projecting system in the X direction and the Y direction orthogonal to each other;
An edge position acquisition unit (140, 150, 160) that obtains an edge position of an object to be measured from reflected light amount characteristics output from the photodetector and position information obtained from the first driving device;
The first driving device moves the measured object and the light projecting system along the other of the X direction and the Y direction with respect to a plurality of m positions of the measured object in either the X direction or the Y direction. And
The edge position acquisition unit acquires a change in the reflected light amount characteristic from the photodetector along with the movement, and obtains an edge position by averaging the acquired m reflected light amount characteristic changes.
An edge detection apparatus characterized by the above.
The edge position acquisition unit
Each edge position is obtained from the intensity threshold value (14) determined from the peak intensity (13) of the reflected light quantity characteristic obtained from the photodetector and the m reflected light quantity characteristics, and the measured object is measured from the edge positions. An edge calculation unit (140) that obtains an edge of the outermost edge and obtains a difference value between the obtained edge of the outermost edge and each edge position;
An edge determination unit (150) having a difference threshold value and excluding the reflected light amount characteristic corresponding to a value whose absolute value of the difference value obtained by the edge calculation unit is larger than the difference threshold value to exclude an abnormal edge position; ,
An edge detection unit (160) for averaging the remaining reflected light amount characteristics other than those excluded by the edge determination unit to obtain a true edge position;
The edge detection apparatus according to claim 1, comprising:
The edge position acquisition unit
Obtained the differential waveform of the reflected light amount characteristic obtained from the photodetector, obtained each edge position from the peak value of this differential waveform, obtained the edge of the outermost edge portion of the object to be measured from this edge position, obtained An edge calculation unit (142) for obtaining a difference value between the edge of the outermost edge and each edge position;
An edge determination unit (152) having a difference threshold and excluding an abnormal edge position by excluding a reflected light amount characteristic corresponding to a value obtained by an edge calculation unit that is greater than the difference threshold;
An edge detection unit (162) that averages the remaining reflected light amount characteristics other than those excluded by the edge determination unit and further obtains this differential waveform to obtain a true edge position;
The edge detection apparatus according to claim 1, comprising:
The edge position acquisition unit
An edge calculation unit (143) for obtaining a differential waveform of the reflected light amount characteristic obtained from the photodetector and obtaining a peak value of the differential waveform;
An edge determination unit (153) having a differential threshold and excluding an abnormal edge position by excluding a reflected light amount characteristic corresponding to a value equal to or less than the differential threshold obtained by an edge calculation unit;
An edge detection unit (163) that averages the remaining reflected light amount characteristics other than those excluded by the edge determination unit and further obtains the differential waveform to obtain the true edge position;
The edge detection apparatus according to claim 1, comprising:
The edge position acquisition unit
An edge calculation unit (144) for obtaining the peak intensity (13) of the reflected light amount characteristic obtained from the photodetector;
An edge determination unit (154) having a peak intensity threshold and excluding a reflected light amount characteristic corresponding to a value of the peak intensity obtained by the edge calculation unit equal to or less than the peak intensity threshold;
An edge detection unit (164) for averaging the remaining reflected light amount characteristics other than those excluded by the edge determination unit to obtain a true edge position;
The edge detection apparatus according to claim 1, comprising:
A second driving device that relatively moves the light projecting system and the object to be measured in a Z direction perpendicular to a plane defined by the X direction and the Y direction, which are moving directions of the first driving device; 240)
A position in the Z direction where the reflected light quantity characteristic obtained from the photodetector is maximized by being electrically connected to the photodetector and changing the distance between the object to be measured and the light projecting system by the second driving device. And a focus detection unit (250) for determining the focus position of the light projecting system with respect to the object to be measured,
The edge detection apparatus according to claim 1, wherein the edge position acquisition unit detects an edge of the measurement object at a focus position of the light beam with respect to the measurement object.
The second driving device relatively moves the light projecting system and the object to be measured so that the spot diameter of the light beam on the object to be measured is larger than the focused state,
In a state where the spot diameter of the light beam is larger than the focused state, the edge position acquisition unit performs edge measurement by scanning the object to be measured with the light beam in the other direction in the X direction and the Y direction. The rough edge position is obtained, and the obtained rough edge position is focused on the focus detection unit by the light beam in each of the X direction and the Y direction. The edge detection apparatus according to claim 6, wherein scanning is performed at the position, and the edge position is obtained using the obtained plurality of reflected light amount characteristics.