JP2008190883A - Measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device capable of utilizing a merit generated thereby even when using femtosecond laser light, preventing the constitution of an optical system from becoming complicated, and measuring highly accurately even fine irregularities on the surface of a specimen. <P>SOLUTION: This device is equipped with a reflection member (deflection element 21) having a reflection surface part (fine mirror 212) for reflecting measuring light from a light source (laser light source 11) to the specimen; a support mechanism 24 having a support part (pivot 243) for supporting the reflection member from the back side facing to the reflection surface part, and a rotation part for supporting rotatably the reflection member around a rotating shaft (a main scanning rotating shaft 40, a sub-scanning rotating shaft 50); a driving part (driving circuit 26) for driving rotatively the reflection surface part around the rotating shaft; and a light receiving part (photodetector 14) for receiving return light formed from reflection of the measuring light by the specimen. In the device, the reflection surface part near the rotating shaft is irradiated with the measuring light, and the shape of the specimen is measured based on information from the light receiving part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a measuring apparatus that measures the three-dimensional shape of a test object in a non-contact manner using, for example, femtosecond laser light.

  As a measuring device using femtosecond laser light, for example, the femtosecond laser light is divided into two parts, one laser light is used as a reference light, and the other laser light is enlarged by a magnifying optical system, and then irradiated with light. The phase of the reflected light (returned light) reflected from the test object is compared with the phase of the reference light, and the phase difference between the two is obtained. A measuring device for measuring a distance has been proposed (Non-Patent Document 1).

  The above measuring device uses the characteristics of femtosecond laser light, which is very excellent in wavelength stability and enables high-precision measurement. As laser light (irradiation light) irradiated to the test object Uses a beam with an enlarged beam diameter.

OPTRONICS (2005) No. 8P. 103-108

  When measuring the three-dimensional shape of the test object using the above measuring device, it is very difficult to accurately measure the fine unevenness of the test object surface because the beam diameter is enlarged. . In order to measure fine irregularities on the surface of the test object with high accuracy, it is conceivable to use, for example, a beam (irradiation light) with a reduced beam diameter. It is a part of an optical system that scans the surface of an object and guides reflected light (returned light) reflected from the surface of the test object to a measurement unit equipped with a phase meter and the like through the optical path of irradiation light. This optical system part is also a part of the reflection surface part that, in particular, scans the surface of the test object by shaking the irradiation light, while reflecting the return light returning from the surface of the test object and guiding it to the optical path of the irradiation light. .

  The reflection surface part is a part where the irradiation light going to the test object and the return light returning from the test object are repeatedly incident and reflected, and the reference light incident part and the return light reflection part are different due to the rotation of the reflection surface part ( If it is shifted, it may be difficult to measure with high accuracy.

  In addition, in order to scan the irradiation light in the vertical and horizontal directions on the surface of the test object, it is necessary to have at least two reflecting surface portions, and it is necessary to rotate each reflecting surface portion, which complicates the configuration of the optical system. The optical path error of the irradiation light that occurs each time reflection is repeated accumulates, and it may be difficult to measure with high accuracy.

  In this way, even if the measurement device is to be used for measuring the shape of the test object, due to the configuration of the optical system, even if femtosecond laser light is used, high-precision measurement that is a merit thereof is difficult. There is a fear.

  The present invention can take advantage of the femtosecond laser light even without using a complicated configuration of the optical system, can be measured with high precision even with fine irregularities on the surface of the test object, It aims at providing a measuring device.

  The measuring apparatus according to claim 1 of the present invention that achieves the above object includes a reflective member having a reflective surface portion that reflects measurement light from a light source to a test object, and a back surface side that faces the reflective surface portion of the reflective member. A support unit having a support unit that supports the reflection member so as to be rotatable about a rotation axis, a drive unit that rotationally drives the reflection surface unit about the rotation axis, and the measurement A light receiving unit that receives return light reflected by the test object, and irradiates the measurement light to the reflecting surface unit in the vicinity of the rotation axis, and based on information from the light receiving unit, It is characterized by measuring the shape of an object.

  The measuring device according to claim 2 of the present invention has a parabolic surface that is disposed between the reflecting member and the test object and reflects the measurement light from the reflecting member to the test object. The parabolic surface has a parabolic mirror located at a position of the reflective surface portion that reflects the measurement light.

  In the measuring device according to claim 3 of the present invention, the support mechanism has two rotating shafts, the two rotating shafts are orthogonal to each other, and the intersection of the two rotating shafts is orthogonal to the support portion. It is characterized by supporting.

  The measuring apparatus according to claim 4 of the present invention is characterized in that the support portion is a conical pivot, and the back surface side of the reflecting surface portion is rotatably supported by the apex of the pivot.

  In the measuring device according to claim 5 of the present invention, the support mechanism includes the support part, a first holding part arranged with a gap from the reflective surface part, and the first holding part. A second connecting portion disposed; a first connecting portion for connecting the reflective surface portion to the first holding portion so as to rotate about one of the two rotating shafts; Of the two rotating shafts, a second connecting portion that connects the first holding portion to the second holding portion so as to rotate around the other rotating shaft is provided.

  The measuring apparatus according to claim 6 of the present invention is characterized in that the driving unit includes two driving members that rotate the reflecting member and do not exert influence on each other.

  In the measurement device according to claim 7 of the present invention, one of the two drive members uses the Coulomb force, and the other drive member uses the Lorentz force to rotate the reflection member. It is characterized by doing.

  The measuring apparatus according to claim 8 of the present invention is characterized in that the measurement light is femtosecond laser light.

  According to the present invention, even if femtosecond laser light is used, its merit can be utilized, the configuration of the optical system is not complicated, and high-precision measurement is possible even with minute irregularities on the surface of the test object. It is.

  Hereinafter, an embodiment of a measuring apparatus of the present invention will be described with reference to FIGS.

  FIG. 1 is a functional block diagram showing an embodiment of the measuring apparatus of the present invention, FIG. 2 is a top view of the reflecting member and its supporting mechanism shown in FIG. 1 as seen from the direction in which probe light is incident, and FIG. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2, FIG. 5 is an explanatory view for explaining a state in which the probe light scans on the test object, and FIG. It is a block diagram of the drive circuit which drives the reflecting member shown.

  As shown in FIG. 1, the measurement apparatus of the present embodiment is equipped with a measurement unit 10, a scanning unit 20, and a calculation unit 30.

  The measuring unit 10 is a device that emits femtosecond laser light, compares the phase of the laser light with the phase of reflected light (returned light) from the test object T, and outputs the phase difference to the arithmetic unit 30.

  Specifically, the measurement unit 10 includes a laser light source 11 that emits femtosecond laser light, a beam splitter 12 that divides the laser light into reference light (reference light) and measurement light (probe light), and a photodetector 13. A photodetector 14 and a phase meter 15.

  The beam splitter 12 divides the laser light into reference light and probe light by reflecting a part of the laser light and transmitting the remaining part.

  The photodetector 13 receives the reference light reflected by the beam splitter 12 and converts it into an electrical signal. The probe light that has passed through the beam splitter 12 is irradiated onto the test object T via the scanning unit 20. The return light reflected from the test object T travels backward on the optical path of the probe light, enters the measurement unit 10 via the scanning unit 20, and is reflected by the beam splitter 12 toward the photodetector 14. The photodetector 14 receives this return light and converts it into an electrical signal.

  The phase meter 15 receives an electric signal (output) from the photo detector 13 and the photo detector 14 to obtain a phase difference (phase data) between the two (reference light and return light), and outputs the phase data to the arithmetic unit 30.

  The scanning unit 20 is an optical device that scans the probe light in a direction perpendicular to the traveling direction of the probe light (XY direction see FIG. 5).

  Specifically, the scanning unit 20 includes a deflecting element 21 as a reflecting member for scanning the surface of the test object T with the probe light, a support mechanism 24 that rotatably supports the deflecting element 21, and the support. A drive circuit 26 that drives the deflection element 21 rotatably supported by the mechanism 24 and a parabolic mirror 28 are provided.

  As shown in FIGS. 2 to 4, the deflection element 21 includes a micro mirror 212 having a reflective surface portion. The micro mirror 212 (reflecting surface portion) is a mirror that reflects the probe light from the laser light source 11 and irradiates the test object T via the parabolic mirror 28.

  The support mechanism 24 rotatably supports the micro mirror 212 (reflection surface portion) around the rotation shafts 40 and 50 of the two rotation shafts of the main scanning rotation shaft 40 and the sub-scanning rotation shaft 50 orthogonal to each other shown in FIG. As shown in FIGS. 3 and 4, a base 242 having a recess 241 at the center, a conical pivot 243 as a support provided on the bottom surface of the recess 241, and a recess 241 are closed. And a basic frame 244 disposed on the base 242.

  The base portion 242 uses, for example, a semiconductor material mainly composed of silicon, and is processed as shown in FIGS. 2 to 4 by a processing method such as photolithography, and an integrated circuit that is a component of the drive circuit 26 is formed. The An external magnetic field (see FIG. 4) by a permanent magnet (not shown) is applied to the base 242 from the perpendicular direction.

  The pivot 243 is a conical member that is provided at a position on the bottom surface of the recess 241 that is directly below the position of the intersection of the main scanning rotation shaft 40 and the sub-scanning rotation shaft 50 with the vertex P slightly rounded. The vertex P of the pivot 243 is in contact with the back surface of the micro mirror 212, and the micro mirror 212 is rotationally oscillated (oscillated) while being supported by the vertex P of the pivot 243.

  The basic frame 244 is a sub-scanning frame 245 as a first holding member arranged with a gap so as to surround the micromirror 212, and a second holding member arranged with a gap so as to surround the sub-scanning frame 245. Main scanning frame 246, a pair of main scanning hinges 247 as a first connecting portion, and a pair of sub scanning hinges 248 as a second connecting portion. These sub scanning frame 245, main scanning frame 246, The main scanning hinge 247 and the sub scanning hinge 248 are integrally formed.

  The basic frame 244 is formed integrally with the micromirror 212 via a pair of main scanning hinges 246. The basic frame 244 integrated with the micromirror 212 is formed of, for example, a metal (aluminum alloy) whose main component is aluminum having high light reflectivity, and has conductivity. The basic frame 244 is formed by punching a metal stay made of, for example, an aluminum alloy with a press, or by a processing method such as photolithography.

  The micro mirror 212 oscillates (oscillates) about the main scanning rotation shaft 40 that is a straight line connecting the pair of main scanning hinges 247.

  The main scanning rotation axis 40 passes through the vertex P of the pivot 243. Since the minute mirror 212 rotates and oscillates around the vertex P of the pivot 243, the rotation center of the minute mirror 212 remains at one point regardless of the rotation angle of the minute mirror 212. Therefore, when the probe light hits the rotation center of the micromirror 212 that is rotating and oscillating (directly above the apex P of the pivot), the reflected light falls within a stable cone range having the rotation center of the micromirror 212 as the apex. Will be reflected.

  The micromirror 212 has a thickness of about 100 μm, and one side of the reflection surface portion 211 that reflects the probe light has a size of about 2 mm square, which is about twice the beam diameter of the laser light, and has a light reflectance as described above. It is made of a metal (aluminum alloy) mainly composed of high aluminum.

  Since the mass of the micromirror 212 is very small, vibration due to rotational vibration (oscillation) hardly occurs, and vibration is hardly transmitted to the parabolic mirror 28 and the measurement unit 10. Therefore, the position (measurement points S1, S2, S3... See FIG. 5) where the probe light scans the object T does not deviate in the main scanning direction and the sub-scanning direction.

  The main scanning hinge 247 is a twistable hinge that rotatably connects the micro mirror 212 and the sub scanning frame 245.

  A pair of drive electrodes 261 is provided on the bottom surface of the recess 241 of the base 242 facing the micromirror 212. The drive electrode 261 is an electrode to which an alternating voltage is applied. When an alternating voltage is applied to the drive electrode 261, the main scanning hinge 247 is twisted by the Coulomb force acting between the drive electrode 261 and the micromirror 212, and the micromirror 212 is supported by the pivot 211 in the main state. Rotating and oscillating (swinging) about the scanning rotation axis 40 in the direction of arrow A1 (see FIG. 3).

  FIG. 3 shows a state in which the micromirror 212 is oscillating (oscillating). In the drawing, the broken line represents the position of the minute mirror 212 that is most greatly swung. If the micro mirror 212 rotates and vibrates in the direction of the arrow A1 while the probe light is incident on the micro mirror 212, the probe light is reflected by the reflecting surface portion 211 of the micro mirror 212 and is emitted while vibrating in the direction of the arrow A2. Head to the object mirror 28. When the micromirror 212 rotates and vibrates in the direction of the arrow A1, the probe light hitting (irradiating) the test object T moves on the test object T in the main scanning direction as shown in FIG.

  The sub-scanning frame 245 is a member that rotationally vibrates (swings) the micro mirror 212 around the sub-scanning rotation shaft 50 that is a straight line connecting the pair of sub-scanning hinges 248. The sub-scanning rotation axis 50 is orthogonal to the main-scanning rotation axis 40 and passes through the vertex P of the pivot 243 similarly to the main-scanning rotation axis 40.

  The sub-scanning hinge 248 is a twistable hinge that rotatably connects the sub-scanning frame 245 and the main scanning frame 246.

  A pair of drive coils 262 are provided at both ends of the sub-scanning frame 245 in the main scanning rotation axis 40 direction. The drive coil 262 is a coil to which an alternating current is applied. In FIG. 2, the wiring connecting the drive coil 262 and the drive circuit 26 (see FIG. 1) is omitted. When an alternating current is applied to the drive coil 262, the sub-scanning hinge 248 is twisted by the Lorentz force acting between the driving magnetic field generated by the driving coil 262 and the external magnetic field shown in FIG. Rotate and vibrate (swing) in the direction of arrow A3 about the sub-scanning rotation axis 50.

  When the sub-scanning frame 245 rotates and vibrates in the direction of the arrow A3, the micromirror 212 also vibrates and vibrates in the direction of the arrow A3. The direction of arrow A1 and the direction of arrow A3 are directions orthogonal to each other. FIG. 4 shows a state in which the minute mirror 212 is oscillating and rotated by the sub-scanning frame 245. In the drawing, the broken line represents the position of the minute mirror 212 that is most greatly swung.

  As described above, the Coulomb force and the Lorentz force that do not interact with each other (that do not affect each other) are used as the driving force in the main scanning direction and the driving force in the sub-scanning direction. The rotation angle of the mirror 212 and the rotation angle of the micro mirror 212 in the sub-scanning direction can be controlled independently of each other. Therefore, the rotation angle of the micro mirror 212 in the main scanning direction and the sub scanning direction is stabilized.

  When the sub-scanning frame 245 rotates and vibrates in the direction of arrow A3 while the probe light is incident on the micromirror 212, the probe light is reflected by the reflecting surface portion 211 of the micromirror 212 and vibrates in the direction of arrow A4. To the parabolic mirror 28. When the micromirror 212 rotates and vibrates in the direction of the arrow A3, the probe light hitting the test object T moves on the test object T in the sub-scanning direction as shown in FIG.

  As shown in FIG. 1, the parabolic mirror 28 is disposed on the optical path between the reflecting member 21 and the test object T, and reflects the probe light from the micromirror 212 to the test object T. The focal point of the parabolic reflecting surface is located at the reflecting surface portion 211 where the probe light is irradiated and reflected. Accordingly, the probe light is irradiated onto the test object T via the paraboloidal mirror 28, and the return light reflected by the test object T travels backward along the optical path of the probe light and is focused by the paraboloidal mirror 28. The light enters the incident / reflected portion of the reflecting surface portion 211, is reflected, and travels toward the measuring unit 10. That is, the return light does not deviate from the optical path of the probe light, travels backward along the optical path, enters the measurement unit 10, and is received by the photodetector 14 via the beam splitter 12.

  The pair of drive electrodes 261 and the pair of drive coils 262 described above are driven by a drive circuit 26 (see FIGS. 1 and 6). The drive circuit 26 is a circuit that drives a pair of drive electrodes 261 and a pair of drive coils 262 that rotationally drive the deflection element 21 so that the probe light on the object T performs main scanning and sub-scanning. .

  FIG. 6 is a circuit block diagram of the drive circuit 26. The oscillation circuit 263 is a circuit that outputs a signal with a fixed period to the main scanning circuit 256. The main scanning circuit 264 measures the test object T every time one period of the output signal of the oscillation circuit 263 passes. In this circuit, a sweep signal passing through points S1, S2, S3, S4... (Hereinafter, this signal is referred to as a main scanning signal) is output to a pair of voltage sources 266. The pair of voltage sources 266 outputs an alternating voltage obtained by amplifying the main scanning signal between the micromirror 212 and the pair of drive electrodes 261. When this alternating voltage is applied, the micromirror 212 oscillates at an angle (in the direction of arrow A1 in FIG. 3) at which the probe light scans the object T.

  Further, the main scanning circuit 256 outputs a horizontal synchronization signal corresponding to one main scanning cycle to the sub-scanning circuit 265. Each time the output signal of the main scanning circuit 264 passes one main scan, the sub-scanning circuit 265 detects the probe measurement points S1, S11. In this circuit, a sweep signal passing through S21... (Hereinafter, this signal is referred to as a sub-scan signal) is output to a pair of current sources 267. The pair of current sources 267 outputs an alternating current obtained by amplifying the sub scanning signal to the pair of drive coils 262. When this alternating current is applied, the pair of drive coils 262 oscillates at an angle (in the direction of arrow A3 in FIG. 4) at which the probe light is sub-scanned on the object T.

  The calculation unit 30 is a circuit that inputs the phase data from the measurement unit 10 and the synchronization pulse from the scanning unit 20 and calculates the distance from the scanning unit 20 to the measurement point for each measurement point. Output to an external CAD / CAM device. The arithmetic unit 30 is provided with an arithmetic circuit 31. The arithmetic circuit 31 obtains the position coordinate (X coordinate) in the main scanning direction and the position coordinate (Y coordinate) in the sub-scanning direction of each measurement point S1, S2, S3. The distance data of each measurement point represented by the phase data in the coordinate and the Y coordinate is made to correspond as the Z coordinate. Thereby, the shape of the test object T can be measured in a non-contact manner.

  According to the measuring apparatus of the present embodiment configured as described above, the deflecting element 21 can scan the probe light in the main scanning direction and the sub-scanning direction on the object T, and is equipped with a plurality of deflecting elements. The configuration of the optical system can be simplified, and the optical system is complicated, so that no optical path error is accumulated and high-precision measurement is possible.

  Further, the minute mirror 212 is supported by the pivot 243 so that the apex P of the pivot 243 abuts at the intersection of the main scanning rotation shaft 40 and the sub-scanning rotation shaft 50 on the back surface side. During the rotational movement around the rotary shaft 40 and the sub-scanning rotary shaft 50, the center of rotation always stays at one point regardless of the rotation angle. Therefore, when the probe light hits the rotation center of the micromirror 212 that is rotating and oscillating (directly above the apex P of the pivot 243), the reflected light has a stable cone range with the rotation center of the micromirror 212 as the apex. Therefore, highly accurate measurement is possible.

  In addition, since the paraboloidal mirror 28 has the focal point of the parabolic reflection surface set at a location on the reflection surface portion 211 of the micromirror 212, the return light from the test object T is always reflected by the micromirror 212. The light is incident on a predetermined location on the surface portion 211 and is reflected, and enters the measuring portion 10 without going off the optical path of the probe light, and is reliably received by the photodetector 14. And since the shape measurement of the to-be-tested object T is performed based on the information converted into the electrical signal by this photodetector 14, highly accurate measurement is attained.

  In addition, since the Coulomb force and the Lorentz force that do not interact with each other are used to rotationally drive the micromirror 212, the rotation angle of the micromirror 212 in each of the main scanning direction and the sub-scanning direction is independent. Therefore, the rotation angle of the micro mirror 212 is stabilized, and highly accurate measurement is possible.

  The measuring device of the present invention is not limited to the one shown in the above embodiment.

  For example, although the case where the micro mirror 212 is integrally formed on the basic frame 244 constituting the support mechanism 24 is shown, it may be formed separately and then connected to each other.

  Further, instead of forming the micro mirror 212 with a metal (aluminum alloy) whose main component is aluminum with high light reflectivity, the micro mirror 212 is formed with another metal, and an aluminum alloy is deposited on a portion to be a reflective surface portion of the micro mirror 212. May be.

  Moreover, although the case where femtosecond laser light was used as probe light was shown, you may use another laser light.

It is a functional block diagram which shows one Embodiment of the measuring device of this invention. FIG. 2 is a top view of the reflecting member and its support mechanism shown in FIG. 1 as seen from the direction in which probe light is incident. It is sectional drawing which follows the 3-3 line of FIG. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is explanatory drawing explaining the state which probe light scans on a test object. It is a block diagram of the drive circuit which drives the reflective member shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Measurement part 11 Laser light source 12 Beam splitters 13 and 14 Photo detector 15 Phase meter 20 Scanning part 21 Deflection element 24 Support mechanism 26 Drive circuit 30 Calculation part 31 Calculation circuit 40 Main scanning rotation axis 50 Sub-scanning rotation axis 212 Minute mirror (reflection surface part) )
245 Sub-scanning frame (first holding unit)
246 Main scanning frame (second holding unit)
247 Main scanning hinge (first connecting part)
248 Sub-scanning hinge (second connecting part)

Claims (8)

A reflective member having a reflective surface portion for reflecting measurement light from the light source to the test object;
A support mechanism having a support portion that supports the reflection member from the back surface side facing the reflection surface portion, and a rotation portion that rotatably supports the reflection member around a rotation axis;
A drive unit that rotationally drives the reflection surface unit around the rotation axis;
A light receiving portion for receiving the return light reflected by the test object by the measurement light,
A measuring apparatus that irradiates the measuring surface with the measurement light near the rotation axis and measures the shape of the test object based on information from the light receiving unit. The measuring device according to claim 1,
A parabolic surface is disposed between the reflecting member and the test object, and reflects the measurement light from the reflecting member to the test object, and a focal point of the parabolic surface reflects the measurement light. A measuring apparatus comprising a parabolic mirror located at a location of the reflecting surface portion that reflects. In the measuring device according to claim 1 or 2,
The support mechanism has two rotation axes, and the two rotation axes are orthogonal to each other;
The measuring device according to claim 1, wherein the support portion supports an intersection of the two rotation axes that are orthogonal to each other. In the measuring device according to claim 3,
The measuring device according to claim 1, wherein the support portion is a conical pivot, and the back surface side of the reflection surface portion is rotatably supported at the apex of the pivot. In the measuring device according to claim 3 or 4,
The support mechanism is
The support part;
A first holding part disposed with a gap from the reflective surface part;
A second holding portion disposed at a distance from the first holding portion;
A first connecting part for connecting the reflecting surface part to the first holding part so as to rotate around one of the two rotating axes;
A second connecting portion for connecting the first holding portion to the second holding portion so as to rotate around the other rotating shaft of the two rotating shafts;
A measuring device comprising: In the measuring device according to any one of claims 1 to 5,
The measurement device according to claim 1, wherein the drive unit includes two drive members that rotate the reflection surface unit and do not exert influence on each other. In the measuring device according to claim 6,
One of the two drive members, one drive member uses the Coulomb force, and the other drive member uses the Lorentz force to rotate the reflection surface portion. In the measuring device according to any one of claims 1 to 7,
The measuring device is a femtosecond laser beam.

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