JP2012018156A - Surface shape measurement apparatus and surface shape measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface shape measurement apparatus and a surface shape measurement method capable of more accurately measuring the surface shape of a measured object in nm order in a relatively short time.SOLUTION: The surface shape measurement apparatus SA of the present invention deals with three or more measuring points of a measured object Ob per one measurement spot MP. For example, the surface shape measurement apparatus SA executes the steps of: dividing a measuring light ML generated in a measuring light generation unit 1A into three measuring lights in a measuring unit 2A in order to irradiate each of three measuring points P1 to P3 with the measuring light ML; irradiating each of the three measuring points P1 to P3 of the measured object Ob with the divided measuring light ML1 to ML3; making a pair of reflected lights RL1, RL2 to interfere with each other as well as making a pair of reflected lights RL2, RL3 to interfere with each other so as to use a common reflected light RL2, where RL1 to RL3 are reflected lights of the measuring lights ML1 to ML3; and obtaining the surface shape of the measured object Ob based on a first interfering light IL1 and a second interfering light IL2 obtained by the above light interference.

Description

  The present invention relates to a surface shape measuring apparatus and a surface shape measuring method for measuring the surface shape of a measurement object that is a change in the height direction.

  Conventionally, for this type of measurement method, for example, a method using an atomic force microscope (AFM), a method using an interferometer, a method using a laser displacement meter, and a method using an optical cutting method are known. Yes.

  This AFM method is disclosed in, for example, Non-Patent Document 1, and a probe attached to the tip of a cantilever is traced by contacting the surface of the measurement object, or the probe is traced to the measurement object. The surface shape of the object to be measured is obtained by tracing the surface of the cantilever at a constant interval and measuring the vertical displacement of the cantilever at that time.

  In addition, this interferometer method is disclosed in, for example, Patent Document 1 and Non-Patent Document 2, and the light emitted from the light source is divided into, for example, two lights by a dividing unit, and each passes through separate optical paths. Later, these two lights are overlapped again by the multiplexing means, the interference fringes generated by the optical path difference are detected by the detecting means, and this is analyzed by the analyzing means, thereby obtaining the surface shape of the measurement object. . As a method using such an interferometer, a method using a Fizeau interferometer, a Michelson interferometer, an oblique incidence interferometer, or the like is known.

  In addition, this method using a laser displacement meter is disclosed in Non-Patent Document 3, for example. Light is applied to a measurement object by a light emitting element, and the reflected light is detected by an optical position detecting element (SPD). Since the detection position of the reflected light detected by the optical position detection element is also displaced according to the vertical displacement of the object, the surface shape of the measurement object is analyzed by analyzing the detection position of the reflected light by the analysis means. Is what you want.

  Further, the method by this light cutting method is disclosed in Non-Patent Document 4, for example, a fan-shaped sheet light emitted from a light source is irradiated onto a measurement object, and the sheet light is photographed by photographing means. The surface shape of the measurement object is obtained by analyzing the bright line caused by the sheet light in the obtained image by the analyzing means.

  The AFM method can measure basically any surface within a measurement range of 100 μm or less, but it takes time to measure. In this respect, the method using the interferometer, the method using the laser displacement meter, and the method using the optical cutting method can be measured in a few ms and can be measured in a relatively short time. However, the method using the laser displacement meter has a measurement range of about 1 to 10 μm, and the method using the optical cutting method has a measurement range of several μm or more, and these measurement ranges are relatively large, nm Not suitable for surface shape measurement on the order.

  In this respect, the method using the interferometer can measure in a few ms, can be measured in a relatively short time, and from the principle, the measurement range is about the length of the wavelength, that is, a range of several hundred nm, Can be measured.

JP 2007-232667 A

SII Nanotechnology, Inc., “Atomic Force Microscope (AFM / Contact Mode AFM)”, [online], May 6, 2010 search, Internet, <http: // www. siint. com / products / spm / tec_mode / b_2_afm. htm> Fujinon Corporation, “Laser Interferometer Usage Guide”, [online], February 19, 2010 search, Internet, <http: // www. fujinon. co. jp / jp / products / laser / kisotisiki2. htm> Keyence Corporation “displacement sensor / displacement meter”, [online], May 6, 2010 search, Internet, <http: // www. sensor. co. jp / henni / jiten / laser02. htm> Optware Corporation, “High-speed optical cutting method profile measurement system”, [online], search on February 19, 2010, Internet, <http: // www. optware. co. jp / densen. pdf>

  However, the method using the interferometer, including the method using the AFM and the method using the laser displacement meter, measures the distance between the sensing unit and the measurement object at one point, and in the surface direction of the measurement object. By scanning, the surface shape (uneven shape) of the measurement object, which is a change in the height direction (thickness direction), is measured. For this reason, vibrations such as vibration due to up and down movement on the stage on which the measurement object is placed, vibration due to holding fluctuations in the sensing unit, and vibration of the measurement object itself are included in the measurement result, and the measurement result must be accurately measured. Is difficult. Patent Document 1 proposes an optical heterodyne interference measurement method and a measurement apparatus for the purpose of improving inspection accuracy, but the distance between the measurement optical system and the inspection table is completely constant. Therefore, the optical heterodyne interference measurement method and measurement apparatus disclosed in Patent Document 1 do not solve the above-mentioned problems.

  The present invention is an invention made in view of the above-described circumstances, and its purpose is a surface capable of measuring the surface shape of a measurement object with higher accuracy in the order of nm in a relatively short time. To provide a shape measuring device and a surface shape measuring method.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, the surface shape measuring apparatus according to one aspect of the present invention is radiated from the light source unit that emits light and the light source unit to irradiate the measurement light to three or more measurement points on the measurement object. A light splitting unit that divides the measured light into three or more measurement lights, and the plurality of measurement points in the measurement object that are irradiated with the plurality of measurement lights divided by the light splitting unit, respectively. A plurality of optical interference units that optically interfere with a pair of reflected light in the plurality of reflected lights respectively reflected at the points, and a surface shape of the measurement object based on the plurality of interference lights output from the plurality of optical interference units And at least one set of the light interference units in the plurality of light interference units cause the light interference using reflected light common to each other. In the surface shape measurement method according to another aspect of the present invention, the light emitted from the light source unit is irradiated with three or more light beams so as to irradiate measurement light to three or more measurement points on the measurement object. A light splitting step that divides the light into a plurality of measurement lights, and a plurality of light beams that are reflected at the plurality of measurement points by irradiating the plurality of measurement lights divided in the light splitting step to the plurality of measurement points in the measurement object, respectively. A plurality of light interference steps for causing light interference between a pair of reflected light in the reflected light, and a detection step for determining the surface shape of the measurement object based on the plurality of interference lights obtained in the plurality of light interference steps The at least one set of light interference steps in the plurality of light interference steps is characterized in that the light interference is performed using reflected light common to each other.

  Since the surface shape measuring apparatus and the surface shape measuring method having such a configuration are methods using an optical interferometer, the surface shape of the measurement object can be measured in a relatively short time and in the order of nm. In the surface shape measuring apparatus and the surface shape measuring method configured as described above, the reflected light that is common to the plurality of reflected lights reflected from the three or more measuring points on the measurement object is shared. Therefore, interference light having phase information representing gradient information on the surface of the measurement object can be obtained. For this reason, for example, the influence of vibrations such as vibration caused by vertical movement on the stage on which the measurement object is placed, vibration caused by holding fluctuations in the measurement optical system, and vibration of the measurement object itself on the measurement result is canceled and substantially eliminated. be able to. Therefore, the surface shape measuring apparatus and the surface shape measuring method having such a configuration can measure the surface shape of the measurement object with higher accuracy in the order of nm in a relatively short time.

  According to another aspect, in the above-described surface shape measurement apparatus, the light source unit, the light splitting unit, and the light interference unit constitute an optical homodyne interferometer, and the detection unit is the reflected light common to each other. A phase difference detection unit that detects a phase difference between the phases of the plurality of interference lights based on a plurality of interference lights output from the plurality of optical interference units that are caused to interfere with each other using the phase difference detection unit; and And a calculation unit that calculates a surface shape of the measurement object based on the detected phase difference.

  Since the surface shape measuring apparatus having such a configuration includes the optical homodyne interferometer, the surface shape measuring apparatus can be manufactured more simply.

  In another aspect, in the above-described surface shape measuring apparatus, the light splitting unit includes a light branching unit that splits light emitted from the light source unit into three, and the set of light interference units includes: A first optical interference unit that optically interferes with reflected light in the first light divided by the optical branching unit and reflected light in the second light divided by the optical branching unit, and the optical branching unit And a second optical interference unit that optically interferes with the reflected light of the second light and the reflected light of the third light divided by the optical branching unit.

  Since the surface shape measuring device having such a configuration divides the light emitted from the light source unit into three by one light branching unit, the surface shape measuring device can be manufactured more simply.

  According to another aspect, in the above-described surface shape measuring apparatus, the one set of optical interference units is an optical waveguide type optical element in which optical waveguides having different refractive indexes are formed on a base material.

  In the surface shape measuring apparatus having such a configuration, the optical waveguide type optical element constitutes the one set of optical interference units, so that the fluctuation of the air can be removed and the fluctuation of the temperature can be reduced. It can be obtained stably. In addition, since the surface shape measuring apparatus having such a configuration constitutes the one set of optical interference units with optical waveguide optical elements, when the one set of optical interference units is configured by combining a plurality of optical elements. In comparison, the optical path can be manufactured more strictly, and the optical path adjustment after assembly is not necessary, and the size can be reduced.

  According to another aspect, in the above-described surface shape measuring apparatus, the light splitting portion of the light splitting portion is a diffraction grating. According to another aspect, in the above-described surface shape measuring apparatus, the light branching section of the light splitting section is an optical waveguide type optical branching device.

  In the surface shape measuring apparatus having such a configuration, the optical branching unit of the light splitting unit is configured by a diffraction grating or an optical waveguide type optical splitter. Therefore, the light splitting unit of the light splitting unit is combined with a plurality of optical elements. Compared to the configuration, the optical path can be manufactured more strictly, the optical path adjustment after assembly is unnecessary, and the size can be reduced.

  In another aspect, in the above-described surface shape measuring apparatus, the light source unit, the light splitting unit, and the optical interference unit constitute an optical heterodyne interferometer, and the detection unit is the reflected light common to each other. A plurality of interfering lights output from the plurality of optical interfering parts caused to interfere with each other using a phase detector, and detecting a phase difference between the phases of the plurality of interfering lights, and detecting by the detecting part And a calculation unit that calculates the surface shape of the measurement object based on the phase difference.

  Since the surface shape measuring apparatus having such a configuration includes the optical heterodyne interferometer, the surface shape of the measurement object can be measured with higher accuracy.

  According to another aspect, in the above-described surface shape measuring apparatus, the first light branching unit that divides the light emitted from the light source unit into two and the two light beams divided by the first light branching unit An optical modulator that modulates the frequency to a different frequency, and the optical divider includes a second optical branching unit that further divides one of the two lights modulated by the optical modulator into two, The set of optical interference units includes a first optical interference unit that causes optical heterodyne interference between the reflected light of the other light modulated by the light modulating unit and the reflected light of the one light divided by the second branching unit. A second optical interference unit that causes optical heterodyne interference between the reflected light of the other light modulated by the light modulation unit and the reflected light of the other light divided by the second branching unit, The detector is output from the first and second optical interference units. The first and the second interference light respectively phase detection is, and detecting a phase difference between the phase of the first and second interference light.

  In such a configuration, an optical heterodyne interferometer type surface shape measuring device having three measuring points at one measuring point is provided.

  According to another aspect, in the surface shape measuring apparatus described above, the first reference light that causes optical heterodyne interference between the other light modulated by the light modulation unit and the one light divided by the second branching unit. An interference unit; and a second reference light interference unit that causes optical heterodyne interference between the other light modulated by the light modulation unit and the other light divided by the second branching unit, and detecting the detection unit A phase detector for detecting the first and second reference interference lights output from the first and second reference light interference sections, and using a phase difference between the phases of the first and second reference interference lights as a correction value; Detecting and correcting the phase difference between the phases of the first and second interference light with the correction value, and the calculation unit of the detection unit performs the measurement based on the phase difference detected and corrected by the detection unit. To calculate the surface shape of the object. And butterflies.

  Phase fluctuations that occur while the light emitted from the light source unit is guided to the surface of the measurement object greatly influences the measurement result. In the surface shape measuring apparatus having such a configuration, interference light that does not act on the surface of the measurement target is obtained by the first and second reference light interference units, and the measurement target is corrected using the obtained interference light. Is calculated. For this reason, the surface shape measuring apparatus having such a configuration can eliminate the influence of the phase fluctuation on the measurement result, and can measure the surface shape of the measurement object with higher accuracy.

  According to another aspect, in the above-described surface shape measuring apparatus, the one set of optical interference units is an optical waveguide type optical element in which optical waveguides having different refractive indexes are formed on a base material. .

  In the surface shape measuring apparatus having such a configuration, the optical waveguide type optical element constitutes the one set of optical interference units, so that the fluctuation of the air can be removed and the fluctuation of the temperature can be reduced. It can be obtained stably. In addition, since the surface shape measuring apparatus having such a configuration constitutes the one set of optical interference units with optical waveguide optical elements, when the one set of optical interference units is configured by combining a plurality of optical elements. In comparison, the optical path can be manufactured more strictly, and the optical path adjustment after assembly is not necessary, and the size can be reduced.

  According to another aspect, the surface shape measuring device includes three or more light guides that guide each measurement light divided by the light splitting unit and irradiate the plurality of measurement points, respectively. The light source unit, the light splitting unit, the light guide unit, and the detection unit are configured to form an optical heterodyne interferometer, the light source unit emits light whose frequency changes periodically, The set of light guides for obtaining each reflected light that causes light interference in the set of light interference units obtains the reflected light that is common to each other in the set of light interference units. Measured at a measurement point at which reflected light other than the reflected light common to each other is obtained in the specific light guide unit that irradiates the measurement light to the measurement point and the set of light interference units of the set of light guide units The optical path difference between at least two other light guides that emit light is a predetermined optical path difference. Each of the plurality of interference lights output from the plurality of optical interference units caused to interfere with each other using the reflected light common to each other, and the plurality of interferences It has a detection part which detects the phase difference between each phase in light, and a calculating part which calculates the surface shape of the measurement object based on the phase difference detected by the detection part. A surface shape measurement method according to another aspect of the present invention is a method of measuring the surface shape of a measurement object using optical heterodyne interferometry, and includes a plurality of three or more measurements on the measurement object. A light splitting step of dividing light periodically radiated from the light source unit into three or more measurement light beams to irradiate the measurement light to the points, and the plurality of the split light beams divided in the light splitting step Each of the plurality of light guide / irradiation steps for simultaneously irradiating the plurality of measurement points on the measurement object with the measurement light, respectively, and a plurality of light reflected at the plurality of measurement points. A plurality of light interference steps of causing a pair of reflected light in the reflected light to interfere with each other, and a detection step of obtaining a surface shape of the measurement object based on a plurality of interference lights obtained in the plurality of light interference steps, Multiple lights At least one set of light interference steps in the negotiation step is a set of light guide / irradiation for obtaining each reflected light that causes the light interference using the reflected light common to each other and interferes in the set of light interference steps. The process includes a specific light guide / irradiation step of irradiating measurement light to a measurement point at which reflected light common to each other in the set of light interference steps of the set of light guide / irradiation steps is obtained, And at least two other light guide / irradiation steps for irradiating measurement light to a measurement point where reflected light other than the reflected light common to each other in the one set of light interference steps of the set of light guide / irradiation steps is obtained. The measurement light is respectively guided so that the optical path difference between them becomes a predetermined optical path difference.

  Since the surface shape measuring apparatus and the surface shape measuring method having such a configuration are methods using an optical interferometer using the optical heterodyne method, the surface shape of the measurement object can be measured in a relatively short time in the order of nm. Can be measured. In the surface shape measuring apparatus and the surface shape measuring method configured as described above, the reflected light that is common to the plurality of reflected lights reflected from the three or more measuring points on the measurement object is shared. Therefore, interference light having phase information representing gradient information on the surface of the measurement object can be obtained. For this reason, for example, the influence of vibrations such as vibration caused by vertical movement on the stage on which the measurement object is placed, vibration caused by holding fluctuations in the measurement optical system, and vibration of the measurement object itself on the measurement result is canceled and substantially eliminated. be able to. Therefore, the surface shape measuring apparatus and the surface shape measuring method having such a configuration can measure the surface shape of the measurement object with higher accuracy in the order of nm in a relatively short time.

  In addition, the light whose frequency changes periodically is divided into a plurality of measurement lights, and an optical path difference is provided between these measurement lights to irradiate a plurality of measurement points. In addition, since the so-called self-delay type optical heterodyne interference system that causes the reflected lights to interfere with each other is used, it is possible to reduce the size of the light source and improve the degree of freedom in selecting the light source. That is, in a normal optical heterodyne interference method (a method in which light having a constant frequency is divided into two measurement lights and one measurement light is frequency-modulated to provide a slight frequency difference between the two measurement lights), as a light source, for example In addition, since a laser oscillator and an optical modulation element having a very stable oscillation frequency such as a gas laser must be used, the degree of freedom in selecting a light source is small and downsizing is difficult. In the type of optical heterodyne interference method, for example, a semiconductor laser or the like can be used, so that it is possible to reduce the size of the light source and improve the life of the light source.

  The predetermined optical path difference is specifically determined by the pair of reflections in order to cause optical interference between the reflected light obtained from the specific light guide unit and the reflected light obtained from the other light guide unit. This is based on the difference in frequency provided between the light and the corresponding measurement light. Thereby, the information regarding the surface shape of the measurement object can be suitably extracted from the beat generated by causing the reflected lights to interfere with each other.

  Further, in another aspect, three or more measurement points are arranged in a line on the surface of the measurement object, and in the above-described surface shape measurement apparatus, the plurality of light interference units are respectively arranged at the measurement points arranged in the line. A pair of reflected light in a plurality of reflected lights is optically interfered, and in each light guide unit, the other end side of the row from the light guide unit that irradiates the measurement light to a measurement point located at one end of the row The optical path length is sequentially increased by the predetermined optical path difference toward the light guide portion that irradiates the measurement light to the measurement point located at the position. Note that the rows where measurement points are arranged are not limited to rows arranged along a straight line, but may be rows arranged along a curve or the like.

  In the surface shape measuring apparatus having such a configuration, since the gradient between the measurement points arranged in the row direction can be measured at a time, the surface shape along the direction in which the measurement points are arranged can be measured at a time. . As a result, it is possible to shorten the measurement time of the surface shape of the measurement object.

  Further, in another aspect, three or more measurement points are arranged in a line on the surface of the measurement object, and in the above-described surface shape measurement apparatus, the plurality of light interference units are respectively arranged at the measurement points arranged in the line. A pair of reflected light in a plurality of reflected lights is optically interfered, and in each light guide unit, the other end side of the row from the light guide unit that irradiates the measurement light to a measurement point located at one end of the row The optical path lengths of the odd-numbered or even-numbered light guides are the same toward the light guides that irradiate the measurement light to the measurement points located at the positions.

  In the surface shape measuring apparatus having such a configuration, it is possible to change the frequency difference between the light beams causing heterodyne interference in the direction in which the measurement points are arranged on the measurement object. For example, when all of the optical path lengths of the odd-numbered light guides are the same, if the optical path lengths of the even-numbered light guide parts are all the same, the light guide parts that irradiate the measurement light to the measurement points adjacent to each other The optical path differences can be all made the same, so that the frequency difference between the measurement lights applied to the measurement points adjacent to each other is constant. On the other hand, if only the optical path length of a specific even-numbered light guide section is different from the optical path length of the other even-numbered light guide sections other than this, this specific even-numbered light guide section transmits measurement light. The frequency difference between the measurement lights irradiated to the measurement point to be irradiated and the adjacent measurement point can be set to a value different from the frequency difference between the measurement lights irradiated to other adjacent measurement points.

  Moreover, in the above-described surface shape measuring device according to another aspect, the other light guides are all light guide parts other than the specific light guide part in the set of light guide parts. And

  In the surface shape measuring apparatus having such a configuration, each measurement that is irradiated with the measurement light from the measurement point and the other light guide unit is based on the measurement point that is irradiated with the measurement light from the specific light guide unit. The slope between points can be measured at once. Thus, for example, if the measurement light from the other light guide unit is irradiated so as to surround the measurement point irradiated with the measurement light from the specific light guide unit, the measurement at the center is performed. The gradient between the point and each of the measurement points surrounding the point can be measured at a time, whereby the surface shape in a predetermined range in the surface direction of the measurement object can be measured at a time.

  In another aspect, in the above-described surface shape measuring apparatus, the light splitting unit and the plurality of light guiding units are optical waveguide optical elements in which optical waveguides having different refractive indexes are formed on a base material. It is characterized by.

  In the surface shape measuring apparatus having such a configuration, the one set of optical interference units is constituted by a so-called optical waveguide type optical element in which an optical waveguide member is disposed on a common base material. Fluctuations can be reduced, and interference light can be obtained more stably. In addition, the measurement result of the surface shape is less susceptible to noise due to vibration or the like than when the divided measurement light is guided by a plurality of optical fibers.

 In addition, since the surface shape measuring apparatus having such a configuration constitutes the one set of optical interference units with optical waveguide optical elements, when the one set of optical interference units is configured by combining a plurality of optical elements. In comparison, the optical path can be manufactured more strictly, and the optical path adjustment after assembly is not necessary, and the size can be reduced.

  According to another aspect, in the above-described surface shape measurement apparatus, the reference light branching unit that branches a part of the light emitted from the light source unit upstream of the light splitting unit as reference light, and the one set A reference light mixing unit that mixes each of the interference light output from the optical interference unit and the reference light, and the detection unit phase-shifts the plurality of reference light mixed signals output from the reference light mixing unit. It has a detection part which detects and detects the phase difference between each phase, and a calculating part which calculates the surface shape of the measurement object based on the phase difference detected by the detection part.

  The light emitted from the light source unit includes a change in output intensity caused by periodically changing the frequency, and this change in output intensity greatly affects the measurement result. In the surface shape measuring apparatus having such a configuration, a change in output intensity included in the light emitted from the light source is detected by mixing the interference light and the reference light by the reference light mixing unit, and this is used to correct the interference light. However, the surface shape of the measurement object is calculated. For this reason, the surface shape measuring apparatus having such a configuration can eliminate the influence of the output intensity change on the measurement result, and can measure the surface shape of the measurement object with higher accuracy.

  The surface shape measuring apparatus and the surface shape measuring method according to the present invention can measure the surface shape of a measurement object with higher accuracy in the order of nm in a relatively short time.

It is a figure which shows the structure of the surface shape measuring apparatus in 1st Embodiment. It is a figure which shows the structure of the measurement part in the surface shape measuring apparatus shown in FIG. It is a figure which shows the other structure of the measurement part in the surface shape measuring apparatus shown in FIG. It is a figure which shows the structure of the surface shape measuring apparatus in 2nd Embodiment. It is a figure which shows the structure of the measurement light production | generation part in the surface shape measuring apparatus shown in FIG. It is a figure which shows the structure of the measurement part in the surface shape measuring apparatus shown in FIG. It is a figure for demonstrating the aspect of the several measurement point in one measurement location. It is a figure which shows the structure of the surface shape measuring apparatus in 3rd Embodiment. It is a figure which shows the structure of the measurement part in the surface shape measuring apparatus shown in FIG. (A) shows the time change of the injection current to the light source, and (B) shows the time change of the oscillation frequency of the light source with respect to the injection current of FIG. It is a figure for demonstrating the frequency difference of two light which interferes in self-delay type | mold optical heterodyne interference. It is a figure which shows the other structure of the measurement part in the surface shape measuring apparatus shown in FIG. It is a figure which shows the structure of the surface shape measuring apparatus in 4th Embodiment. It is a figure which shows the structure of the measurement part in the surface shape measuring apparatus shown in FIG.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. Further, in this specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

  The surface shape measuring apparatus according to the embodiment includes a light source unit that emits light and three pieces of light emitted from the light source unit so as to irradiate measurement light to three or more measurement points on the measurement object. The light dividing unit that divides the light into the plurality of measurement lights, and the plurality of measurement lights divided by the light division unit are irradiated to the plurality of measurement points in the measurement object, respectively, and reflected by the plurality of measurement points, respectively. A plurality of optical interference units that cause optical interference between a pair of reflected lights in the plurality of reflected lights, and a detection unit that obtains the surface shape of the measurement object based on the plurality of interference lights output from the plurality of optical interference units; And at least one set of the light interference portions in the plurality of light interference portions is configured to cause the light interference using reflected light common to each other. And the surface shape measuring method mounted in this surface shape measuring apparatus is the method of irradiating three or more light radiated | emitted from the light source part in order to irradiate the measurement light to each of the three or more measuring points in the measurement object. A light splitting step that divides the light into a plurality of measurement lights, and a plurality of light beams that are reflected at the plurality of measurement points by irradiating the plurality of measurement lights divided in the light splitting step to the plurality of measurement points in the measurement object, respectively. A plurality of light interference steps for causing light interference between a pair of reflected light in the reflected light, and a detection step for determining the surface shape of the measurement object based on the plurality of interference lights obtained in the plurality of light interference steps The at least one set of light interference steps in the plurality of light interference steps is to cause the light interference using reflected light common to each other. Hereinafter, such a surface shape measuring apparatus and the method will be described more specifically.

(First embodiment)
In the surface shape measuring apparatus according to the first embodiment, the light source part, the light splitting part, and the light interference part constitute an optical homodyne interferometer.

  FIG. 1 is a diagram illustrating a configuration of a surface shape measuring apparatus according to the first embodiment. FIG. 2 is a diagram showing a configuration of a measuring unit in the surface shape measuring apparatus shown in FIG. FIG. 3 is a diagram showing another configuration of the measuring unit in the surface shape measuring apparatus shown in FIG.

  The surface shape measuring device SA of the first embodiment is a device that measures a surface shape that is a change in the height direction (thickness direction) of the measurement object Ob. For example, as shown in FIG. Unit 1A, measurement unit 2A, phase difference detection unit 3A, stage (mounting table) 4, calculation control unit 5, input unit 6 and output unit 7 are configured to be measured by stage 4 The surface of the measurement object Ob is scanned by moving the object Ob in the horizontal direction, and the surface shape of the measurement object Ob over a predetermined range is measured.

  The measurement light generator 1A is a device that generates predetermined coherent light and generates measurement light ML for measuring the surface shape of the measurement object Ob by the optical homodyne interferometry. The measurement light ML is single wavelength light having a predetermined wavelength λ (frequency f) set in advance, and is polarized light having a predetermined polarization plane set in advance. For example, as shown in FIG. 1, the measurement light generation unit 1A includes a light source unit 1Aa, an optical isolator 1Ab, a polarizer 1Ac, and an output terminal 1Ad.

  The light source unit 1Aa is a device that emits light L, and includes, for example, a single wavelength laser. This single wavelength laser is a device that generates a single wavelength laser beam L having a predetermined wavelength λ0 (frequency f0) set in advance, and various laser devices can be used. For example, with a predetermined optical power, A helium neon laser apparatus (He-Ne laser apparatus) that can output laser light L having a wavelength of about 632.8 nm. The single wavelength laser is preferably a frequency stabilized laser device equipped with a wavelength locker or the like. The optical isolator 1Ab is an optical component that transmits light only in one direction from its input terminal to its output terminal. In the optical isolator 1Ab, in order to stabilize the laser oscillation of the single wavelength laser in the light source unit 1Aa, the reflected light (returned light) generated at the connection part of each optical component (optical element) in the surface shape measuring device SA This prevents the light from entering a single wavelength laser. The polarizer 1Ac is an optical component (optical element) that extracts and emits linearly polarized light having a predetermined polarization plane from incident light, and is, for example, a polarization filter. The output terminal 1Ad is a terminal for emitting light from the optical component. On the other hand, an input terminal 2Aa (2Ba), which will be described later, is a terminal for making light incident on the optical component. For the connection between the parts, for example, a light guide means composed of individual optical components (optical elements) such as a mirror and a lens may be used. In the present embodiment, the connection between the parts will be described later. As described above, since optical fibers such as a polarization maintaining optical fiber, a single mode optical fiber, and a multimode optical fiber are used, connectors for connecting the optical fibers are used for these input terminals and output terminals.

  In the measurement light generation unit 1A having such a configuration, the laser light L emitted from the single wavelength laser of the light source unit 1Aa is incident on the polarizer 1Ac via the optical isolator 1Ab and has a predetermined polarization plane ( The measurement light ML (s-polarized laser light or p-polarized laser light) is emitted from the output terminal 1Ad. The measurement light ML is incident on the measurement unit 2A.

  In this embodiment, the measurement light generating unit 1A and the measurement unit 2A are connected to each other by a polarization maintaining optical fiber that guides light while maintaining its polarization plane, or single mode light that guides light in a single mode. An optical fiber such as a fiber is used. The polarization maintaining optical fiber is, for example, a PANDA fiber or an elliptical core optical fiber. The measurement light ML emitted from the output terminal 1Ad of the measurement light generation unit 1A is guided by this optical fiber and enters the measurement unit 2A.

  The measurement unit 2A is a device that receives the measurement light ML from the measurement light generation unit 1A and obtains an optical signal including information on the surface shape of the measurement object Ob by optical homodyne interferometry using the measurement light ML. Such a measurement unit 2A can measure three or more measurement points P (P1, P2, P3,...) In the measurement object Ob in the measurement by irradiating the measurement light ML once with respect to one measurement point MP. , Pn) is irradiated with the measurement light ML (ML1, ML2, ML3,..., MLn), respectively, and the measurement light ML from the measurement light generation unit 1A is irradiated with three or more measurement lights ML1, ML2, ML3. ,..., MLn, and a plurality of measurement points P1, P2, and a plurality of measurement lights ML1, ML2, ML3,. A plurality of reflected lights RL (RL1, RL2, RL3,..., RLn) respectively irradiated on the plurality of measurement points P1, P2, P3,. Pair of reflections in And a plurality of light interference section for optically interfere with RL, at least one pair of optical interference portions in the plurality of light interference section is configured to optical interference using a common reflected light RL from each other.

  More specifically, as shown in FIG. 2, for example, the measurement unit 2A includes an input terminal 2Aa, an input-side waveguide 2Ab, a diffraction grating 2Ac, an objective lens 2Ad, a half mirror 2Ae, and a condenser lens 2Af. And an output side waveguide 2Ag and an output terminal 2Ah. The input side waveguide 2Ab and the output side waveguide 2Ag are provided by forming optical waveguides having different refractive indexes on the base material 2Ai. ing.

  The base material 2Ai is a plate-like member (substrate) formed from a material having a predetermined refractive index, and the input terminal 2Aa and the output terminal 2Ah are arranged at predetermined positions on the outer peripheral surface. In the example shown in FIG. 2, the base material 2Ai has a substantially rectangular parallelepiped shape, and the input terminal 2Aa and the output terminal 2Ah are disposed on the upper surface thereof. The optical fiber extending from the measurement light generator 1A is connected to the input terminal 2Aa.

  The base material 2Ai has an input side waveguide 2Ab extending from the position where the input terminal 2Aa in the base material 2Ai is disposed only slightly (for example, 0.3%) than the predetermined refractive index in the base material 2Ai. To about 3%). The input-side waveguide 2Ab guides the measurement light ML from the measurement light generation unit 1A that is incident from one end (incident end) via the input terminal 2Aa, and the other end (exit end). ) Is provided with a diffraction grating 2Ac. In the example shown in FIG. 2, the input-side waveguide 2Ab is directed from the position where the input terminal 2Aa is disposed on the upper surface of the base material 2Ai to the lower surface along one side surface of the base material 2Ai, and is approximately at a predetermined position. It is a substantially L-shape that bends about 90 degrees by an arc and extends along the lower surface.

  The diffraction grating 2Ac is an optical component that diffracts incident light, and an objective lens 2Ad and a half mirror 2Ae are arranged in this order on the exit side. In this embodiment, the diffraction grating 2Ac is a transmission type diffraction grating that transmits incident light when the incident light enters the grating and emits the diffracted light. The half mirror 2Ae is an optical component that divides incident light into two lights in terms of optical power and emits them respectively. One of the distributed lights passes through the half mirror 2Ae and is emitted in the same direction. The other distributed light is reflected by the half mirror 2Ae and emitted in a direction perpendicular to the direction (a direction perpendicular to the direction).

  These input-side waveguide 2Ab, diffraction grating 2Ac, and objective lens 2Ad are arranged so that their optical axes coincide with each other, and half mirror 2Ae has a mirror surface that intersects this optical axis at an angle of 45 degrees. It is arranged.

  In the input terminal 2Aa, the input-side waveguide 2Ab, the diffraction grating 2Ac, the objective lens 2Ad, and the half mirror 2Ae configured as described above, the measurement light ML from the measurement light generation unit 1A is input from the optical fiber via the input terminal 2Aa. The light enters the side waveguide 2Ab. The measurement light ML incident on the input side waveguide 2Ab propagates in the input side waveguide 2Ab, is guided by the input side waveguide 2Ab, and enters the diffraction grating 2Ac. The measurement light incident on the diffraction grating 2Ac is diffracted by the diffraction grating 2Ac, divided into a plurality of diffracted lights (measurement light ML), and incident on the objective lens 2Ad. In the present embodiment, in measurement by one irradiation of the measurement light ML to one measurement point MP, in order to irradiate the measurement light ML to each of the three measurement points P (P1, P2, P3) on the measurement object Ob, Of these plural diffracted lights, three diffracted lights are used as the measurement light ML (ML1, ML2, ML3). Since the three diffracted lights ML1, ML2, and ML3 used in this way are relatively stronger and symmetrical in terms of optical power, for example, 0th-order diffracted light, + 1st-order diffracted light, and −1st-order diffracted light are used. It is done. The three measurement lights ML1, ML2, and ML3 incident on the objective lens 2Ad receive the lens action, enter the half mirror 2Ae, are reflected by the half mirror 2Ae, and the optical path is bent 90 degrees and emitted. Here, the objective lens 2Ad is configured to have a lens action such that the three measurement lights ML1, ML2, and ML3 emitted by the half mirror 2Ae having the optical path bent by 90 degrees are parallel light.

  Then, the three parallel measurement lights ML1, ML2, and ML3 emitted from the half mirror 2Ae are emitted from the measurement unit 2A, and three measurement points P1, P2, and a single measurement point MP on the surface of the measurement object Ob. Each P3 is irradiated and reflected. Three reflected lights (regular reflection components of reflected light) RL (RL1, RL2, RL3) reflected at three measurement points P1, P2, and P3 on the surface of the measurement object Ob are incident on the measurement unit 2A. , And enters the condenser lens 2Af through the half mirror 2Ae.

  The condenser lens 2Af has an optical axis orthogonal to the optical axis of the input-side waveguide 2Ab, diffraction grating 2Ac, and objective lens, and −45 degrees (135 degrees, with reference to the mirror surface) of the mirror surface of the half mirror 2Ae. They are arranged to intersect at an angle of (when the counterclockwise direction is the positive direction). The condensing lens 2Af includes a number of lenses corresponding to the number of reflected lights RL (RL1, RL2, RL3) in order to give a lens action to each of the three reflected lights RL1, RL2, and RL3. On the exit side, the output-side waveguide 2Ag is formed by making it slightly larger (for example, about 0.3 to 3%) than the predetermined refractive index of the substrate 2Ai.

  The output-side waveguide 2Ag guides each reflected light RL (RL1, RL2, RL3 in the example shown in FIG. 2) incident from the condenser lens 2Af, and a pair of reflected lights RL in the plurality of reflected lights RL. Are guided to guide a plurality of interference lights IL. Here, in the present embodiment, at least one set of interference lights IL among the plurality of interference lights IL is generated by causing optical interference using the reflected light RL common to each other. More specifically, the output-side waveguide 2Ag is generally formed along the other side surface of the base 2Ai, and the three lenses corresponding to the three reflected lights RL1, RL2, and RL3 in the condensing lens 2Af. Waveguide sections 2Ag-1, 2Ag-2, 2Ag-3 extending from the exit side of the first waveguide section, a branch section 2Ag-4 that branches the central waveguide section 2Ag-2 into two, and a branch section 2Ag-4 The other waveguide portion branched at the branch portion 2Ag-4 and the waveguide portion 2Ag-3. A joining portion 2Ag-6 that joins, a waveguide portion 2Ag-7 that extends from the joining portion 2Ag-5 to the output terminal 2Ah, a waveguide portion 2Ag-8 that extends from the joining portion 2Ag-6 to the output terminal 2Ah, and It is configured with.

  In the half mirror 2Ae, the condensing lens 2Af, the output-side waveguide 2Ag, and the output terminal 2Ah having such a configuration, in the example illustrated in FIG. 2, the reflection is performed at three measurement points P1, P2, and P3 on the surface of the measurement object Ob. The three reflected lights (regular reflection components of the reflected light) RL (RL1, RL2, RL3) are incident on the measurement unit 2A and are incident on the respective lenses of the condenser lens 2Af via the half mirror 2Ae. The respective lenses of the condensing lens 2Af cause the respective reflected lights RL1, RL2, and RL3 to enter the three waveguide portions 2Ag-1, 2Ag-2, and 2Ag-3 in the waveguide portion 2Ag, respectively. That is, the respective lenses of the condenser lens 2Af are for waveguide coupling with respect to the three waveguide portions 2Ag-1, 2Ag-2, 2Ag-3 in the output side waveguide 2Ag. The reflected light RL2 incident on the central waveguide section 2Ag-2 propagates through the waveguide section 2Ag-2, is guided by the waveguide section 2Ag-2, and is distributed by the branch section 2Ag-4. One reflected light RL2 (RL2-1) distributed by the branching section 2Ag-4 is guided to the joining section 2Ag-5, and the other reflected light RL2 (RL2-2) is sent to the joining section 2Ag-6. Light is guided. Further, the reflected light RL1 incident on the waveguide portion 2Ag-1 propagates through the waveguide portion 2Ag-1, is guided by the waveguide portion 2Ag-1, and is guided to the junction 2Ag-5. The reflected light RL3 incident on the waveguide section 2Ag-3 propagates through the waveguide section 2Ag-3, is guided by the waveguide section 2Ag-3, and is guided to the joining section 2Ag-6. In the merging unit 2Ag-5, the reflected light RL2 and the reflected light RL1 guided as described above are combined and subjected to optical homodyne interference to generate the first interference light IL1 (= RL1 + RL2). The first interference light IL1 is guided from the junction 2Ag-5 to the waveguide 2Ag-7, propagates through the waveguide 2Ag-7, is guided by the waveguide 2Ag-7, and is output to the output terminal 2Ah. Is incident on. Then, at the junction 2Ag-6, the reflected light RL2 and the reflected light RL3 guided as described above are combined and subjected to optical homodyne interference to generate the second interference light IL2 (= RL2 + RL3). The second interference light IL2 is guided from the merging portion 2Ag-6 to the waveguide portion 2Ag-8, propagates through the waveguide portion 2Ag-8, is guided by the waveguide portion 2Ag-8, and is output to the output terminal 2Ah. Is incident on. The first and second interference lights IL1 and IL2 are optical signals including information on the surface shape of the measurement object Ob. The first and second interference lights IL1 and IL2 are incident on the phase detection unit 3A from the measurement unit 2A via the output terminal 2Ah.

  Further, in place of the measurement unit 2A, the measurement light ML from the measurement light generation unit 1A is incident, and an apparatus for obtaining an optical signal including information on the surface shape of the measurement object Ob by optical homodyne interferometry using the measurement light ML. A certain measurement unit 2B may be used.

  More specifically, as shown in FIG. 3, for example, the measurement unit 2B includes an input terminal 2Ba, an input side waveguide 2Bb, an objective lens 2Bc, a half mirror 2Ae, a condensing lens 2Be, and an output side guide. The input side waveguide 2Bb and the output side waveguide 2Bf are provided by forming optical waveguides having different refractive indexes on the substrate 2Bh.

  The base material 2Bh is the same as the base material 2Ai, and is a substantially rectangular parallelepiped plate-like member (substrate) formed from a material having a predetermined refractive index, and each predetermined position on the outer peripheral surface, for example, the upper surface thereof Are provided with an input terminal 2Ba and an output terminal 2Ag. The optical fiber extending from the measurement light generator 1A is connected to the input terminal 2Ba.

  The base material 2Bh has an input-side waveguide 2Bb extending from the position where the input terminal 2Ba in the base material 2Bh is disposed only slightly (for example, 0.3%) than the predetermined refractive index in the base material 2Bh. To about 3%). The input-side waveguide 2Bh guides the measurement light ML from the measurement light generation unit 1A that is incident from one end thereof via the input terminal 2Ba, and includes a plurality of measurement points P at one measurement point MP. In order to irradiate each with the measurement light ML, the measurement light ML from the measurement light generator 1A is branched into a plurality of measurement lights ML, and a condensing lens 2Bc is disposed at the other end. . More specifically, in the example illustrated in FIG. 3, the input-side waveguide 2Bb is directed from the position where the input terminal 2Ba is disposed on the upper surface of the base material 2Bh to the lower surface along one side surface of the base material 2Bh. The waveguide portion 2Bb-1 has a shape extending approximately 90 degrees by a substantially arc at a predetermined position, a branch portion 2Bb-2 that branches the waveguide portion 2Bb-1 into three, and a branch portion 2Bb-2 Are provided with three waveguide portions 2Bb-3, 2Bb-4, and 2Bb-5 branched at 1. These three waveguide portions 2Bb-3, 2Bb-4, and 2Bb-5 are arranged so that their optical axes are parallel to each other at the exit end, and from the branch portion 2Bb-2 along the lower surface to the condenser lens 2Bc. It is the shape extended so that it may reach. The waveguide portion 2Bb-3 and the waveguide portion 2Bb-5 branched to both sides at the branch portion 2Bb-2 are in the extending direction of the waveguide portion 2Bb-3 and the waveguide portion 2Bb-5 (surface of the base material 2Bh). When viewed in a plan view from a direction perpendicular to the direction (normal direction of the surface of the base material 2Bh), it is formed so as to have line symmetry with the central waveguide portion 2Bb-4 as the axis of symmetry. And the optical distance (optical path length) from the branch part 2Bb-2 to the condensing lens 2Bc is equal to each other in the waveguide parts 2Bb-3 to 2Bb-5. As described above, the optical path redundant portion CV1 is bent (bent) in a direction orthogonal to the extending direction of the waveguide portion 2Bb-3 and the waveguide portion 2Bb-5 in the plane of the base 2Bh.

  The objective lens 2Bc is configured to include a number of lenses corresponding to the number of the plurality of measurement lights ML in order to give a lens action to each of the plurality of measurement lights ML guided and branched by the input-side waveguide 2Bb. A half mirror 2Bd is disposed on the emission side. In the example shown in FIG. 3, the objective lens 2Bc is branched by the branching section 2Bb-2 of the input-side waveguide 2Bb, and each of the measurement lights ML1 and ML2 emitted from the three waveguide sections 2Bb-3 to 2Bb-5. , RL3 is provided with three lenses so as to give a lens action. Each lens of the objective lens 2Bc condenses each measurement light ML emitted from the input-side waveguide 2Bb, and enters each condensing measurement light ML into the half mirror 2Bd.

  The half mirror 2Bd is the same as the herb mirror 2Ae. One of the distributed light passes through the half mirror 2Bd and is emitted in the same direction, and the other distributed light is reflected by the half mirror 2Bd and perpendicular to the direction. In the right direction (orthogonal direction).

  The input side waveguide 2Bb and the objective lens 2Bc are arranged so that their optical axes coincide with each other. That is, each optical axis of each of the waveguide portions 2Bb-3 to 2Bb-5 in the input side waveguide 2Bb is in agreement with each optical axis of each lens in the objective lens 2Bc. The half mirror 2Bd is disposed such that the mirror surface intersects the optical axis at an angle of 45 degrees.

  In the input terminal 2Ba, the input side waveguide 2Bb, the objective lens 2Bc, and the half mirror 2Bd having such a configuration, the measurement light ML from the measurement light generating unit 1A is input from the optical fiber through the input terminal 2Ba to the input side waveguide 2Bb. Is incident on. The measurement light ML incident on the input side waveguide 2Bb propagates in the input side waveguide 2Bb, is guided by the input side waveguide 2Ab, is divided into a plurality of parts, and is incident on the objective lens 2Bc. More specifically, the measurement light ML incident on the input-side waveguide 2Bb is guided by the waveguide section 2Bb-1, and is divided into a plurality by the branch section 2Bb-2, and in the example shown in FIG. In the measurement by one irradiation of the measurement light ML to the measurement location MP, the measurement light ML is branched into three to irradiate each of the three measurement points P (P1, P2, P3) on the measurement object Ob. Each measurement light branched into three is guided by each of the waveguide portions 2Bb-3 to 2Bb-5, and is incident on the respective lenses of the objective lens 2Bc. Here, as described above, the waveguide portion 2Bb-3 and the waveguide portion 2Bb-5 located on both sides are symmetrical with respect to each other with respect to the waveguide portion 2Bb-4 located at the center. The central waveguide portion 2Bb-4 has an optical path redundant portion CVI, and each of these waveguide portions 2Bb-3 to 2Bb-5 has the same optical path length. Therefore, these waveguide portions 2Bb-3 to 2Bb- The three measurement beams ML1, ML2, and ML3 that have propagated through the beam 5 are incident on the respective lenses of the objective lens 2Bc with the same phase. The three measurement lights ML1, ML2, and ML3 incident on the objective lens 2Bc are condensed by receiving the lens action, become parallel light to each other, enter the half mirror 2Bd, and are reflected by the half mirror 2Bd. It is bent and ejected.

  Then, the three parallel measurement lights ML1, ML2, and ML3 emitted from the half mirror 2Bd are emitted from the measurement unit 2B, and three measurement points P1, P2, and a single measurement point MP on the surface of the measurement object Ob. Each P3 is irradiated and reflected. Three reflected lights (regular reflection components of reflected light) RL (RL1, RL2, RL3) reflected at three measurement points P1, P2, P3 on the surface of the measurement object Ob are incident on the measurement unit 2B. , And enters the condenser lens 2Be via the half mirror 2Bd.

  The condensing lens 2Be is configured similarly to the condensing lens 2Af, and the output-side waveguide 2Bf is configured similarly to the output-side waveguide 2Ag.

  Therefore, in the example shown in FIG. 3, the half mirror 2Bd, the condensing lens 2Be, the output-side waveguide 2Bf, and the output terminal 2Bg configured as described above are provided at three measurement points P1, P2, and P3 on the surface of the measurement object Ob. Each of the three reflected lights (regular reflection components of the reflected light) RL (RL1, RL2, RL3) reflected is incident on the measuring unit 2B, and is incident on each of the lenses of the condenser lens 2Be via the half mirror 2Bd. The The respective lenses of the condenser lens 2Be are for waveguide coupling, and the reflected lights RL1, RL2, and RL3 are respectively transferred to the three waveguide portions 2Bf-1, 2Bf-2, and 2Bf-3 in the waveguide portion 2Bf. Make it incident. The reflected light RL2 incident on the central waveguide section 2Bf-2 propagates through the waveguide section 2Bf-2, is guided by the waveguide section 2Bf-2, and is distributed by the branch section 2Bf-4. One reflected light RL2 (RL2-1) distributed by the branching section 2Bf-4 is guided to the joining section 2Bf-5, and the other reflected light RL2 (RL2-2) is sent to the joining section 2Bf-6. Light is guided. Further, the reflected light RL1 incident on the waveguide section 2Bf-1 propagates through the waveguide section 2Bf-1, is guided by the waveguide section 2Bf-1, and is guided to the junction section 2Bf-5. The reflected light RL3 incident on the waveguide section 2Bf-3 propagates through the waveguide section 2Bf-3, is guided by the waveguide section 2Bf-3, and is guided to the junction section 2Bf-6. In the merging unit 2Bf-5, the reflected light RL2 and the reflected light RL1 guided as described above are combined and subjected to optical homodyne interference to generate the first interference light IL1 (= RL1 + RL2). The first interference light IL1 is guided from the merging portion 2Bf-5 to the waveguide portion 2Bf-7, propagates through the waveguide portion 2Bf-7, is guided by the waveguide portion 2Bf-7, and is output to the output terminal 2Bg. Is incident on. Then, in the junction 2Bf-6, the reflected light RL2 and the reflected light RL3 guided as described above are combined and subjected to optical homodyne interference to generate the second interference light IL2 (= RL2 + RL3). The second interference light IL2 is guided from the merging portion 2Bf-6 to the waveguide portion 2Bf-8, propagates through the waveguide portion 2Bf-8, is guided by the waveguide portion 2Bf-8, and is output to the output terminal 2Bg. Is incident on. The first and second interference lights IL1 and IL2 are optical signals including information on the surface shape of the measurement object Ob. The first and second interference lights IL1 and IL2 are incident on the phase detection unit 3A from the measurement unit 2B via the output terminal 2Bg.

  Returning to FIG. 1, in the present embodiment, the measurement unit 2A (2B) and the phase difference detection unit 3A may be single mode optical fibers, but the viewpoint of superiority in optical axis adjustment and the amount of propagating light. Are connected by a multimode optical fiber having a plurality of propagation modes. That is, in the present embodiment, the plurality of interference lights IL emitted from the measurement unit 2A (2B), and in the examples shown in FIGS. 2 and 3, the first and second interference lights IL1 and IL2 are guided by the multimode optical fiber. Light is incident on the phase difference detector 3A.

  The phase difference detection unit 3A is a plurality of interference lights IL emitted from the measurement unit 2A (2B), and is based on a set of interference lights IL obtained by optical homodyne interference using the reflected light RL common to each other. Thus, the phase difference ΔΦ between the plurality of interference lights IL in these sets is detected. Then, the phase difference detection unit 3A outputs the detected phase difference ΔΦ to the calculation control unit 5. More specifically, as shown in FIG. 1, the phase difference detection unit 3A includes a photoelectric conversion unit 3Aa (3Aa1, 3Aa2) and a phase difference detector 3Ab.

  The photoelectric conversion unit 3Aa includes, for example, a photoelectric conversion element that converts an electric signal having a signal level corresponding to the amount of incident light, such as a photodiode, and outputs the electric signal. The photoelectric conversion unit 3Aa is prepared according to the number of interference lights IL obtained by the measurement unit 2A (2B), and receives a plurality of interference lights IL from the measurement unit 2A (2B), and according to the respective light quantities. Each electric signal having the same signal level is output as each interference signal Sig. In the present embodiment, since the interference light IL is two, two photoelectric conversion units 3Aa1 and 3Aa2 are prepared. Each of the photoelectric conversion units 3Aa1 and 3Aa2 transmits two first and second interference lights IL1 and IL2 emitted from the output terminal 2Ah (2Bg) of the measurement unit 2A (2B) to the multimode optical fiber and the unillustrated Light is received through each input terminal, and first and second interference signals Sig1 and Sig2 are output to the phase difference detector 3Ab in accordance with the respective light amounts of the interference lights IL1 and IL2.

  The phase difference detector 3Ab receives a plurality of interference signals Sig from the photoelectric conversion unit 3Aa, and a plurality of interference signals IL with respect to a set of interference lights IL obtained by optical homodyne interference using the common reflected light RL. This is a device for detecting the phase difference ΔΦ between Sig. In the example illustrated in FIG. 1, the phase difference detector 3Ab receives the first and second interference signals Sig1 and Sig2 from the photoelectric conversion units 3Aa1 and 3Aa2, and between the first interference signal Sig1 and the second interference signal Sig2. The phase difference ΔΦ at is detected. Then, the phase difference detector 3Ab outputs the detected phase difference ΔΦ to the arithmetic control unit 5.

  The stage 4 is a device that moves the measurement object Ob in a horizontal direction orthogonal to the thickness direction (height direction) of the measurement object Ob according to the control of the arithmetic control unit 5. The stage 4 may be an XY stage that can move the measurement object Ob in the so-called X-axis direction and Y-axis direction, and the stage 4 can rotate and move the measurement object Ob. It may be a rotary stage that can also move in the radial direction in the rotation. The measurement object Ob may be an arbitrary member having a surface, for example, a metal material such as an aluminum plate material, an iron material, and a steel material, a semiconductor wafer, or the like. The XY stage is suitable for measurement of, for example, a rectangular plate member, and the rotary stage is suitable for, for example, a circular plate member.

  The arithmetic control unit 5 is a circuit that controls each part of the surface shape measuring device SA according to the function. For example, a control program or a measurement object for controlling each part of the surface shape measuring device SA according to the function. Stores various predetermined programs such as a calculation program for obtaining the surface shape of Ob based on the output of the phase difference detection unit 3A, and various predetermined data such as data necessary for execution of the predetermined program. A ROM (Read Only Memory) that is a non-volatile storage element, an EEPROM (Electrically Erasable Programmable Read Only Memory) that is a rewritable non-volatile storage element, a predetermined calculation process by reading and executing the predetermined program, CPU (Central Processing Unit) that performs control processing, so-called C that stores data generated during execution of the predetermined program U of working memory and comprising RAM (Random Access Memory), and constituted by a microcomputer or the like provided with these peripheral circuits. The arithmetic control unit 5 functionally includes a shape calculation unit 51, a stage control unit 52, and a light source control unit 53.

  In order to scan the surface of the measurement object Ob, the stage control unit 52 measures a plurality of measurement points MP (at least three measurement points Pn for one measurement point MP) on the measurement object Ob. The operation of the stage 4 is controlled so that the measurement object Ob moves in the horizontal direction perpendicular to the thickness direction. Here, the horizontal movement of the measurement object Ob is obtained because the surface shape of the measurement object Ob is obtained by sequentially connecting the measurement results of the measurement points MP, as will be described later. The stage controller 52 is arranged so that at least one measurement point P overlaps the measurement point P at the measurement location MPtemp and the measurement point P at the measurement location MPnext measured next to the one measurement location MPtemp by scanning. The operation of stage 4 is controlled. For example, the stage control unit 52 causes the stage 4 so that the measurement point P3 at one measurement point MPtemp and the measurement point P1 at the measurement point MPnext measured after the one measurement point MPtemp by scanning overlap each other. To control the operation. The light source control unit 53 controls the operation of the light source unit 1A.

  The shape calculation unit 51 obtains the surface shape of the measurement object Ob based on the phase difference ΔΦ detected by the phase difference detection unit 3A for the plurality of interference lights IL generated by the measurement unit 2A (2B). . The interference light IL includes information on the difference in the height direction (thickness direction) between the two measurement points P. That is, if there is a difference in the height direction between the two measurement points P, the distance (optical path length) between the measurement unit 2A (2B) and the measurement object Ob will be different, and each measurement light of the same phase When the light propagates through the optical paths having different distances and interferes with each other again, the interference light IL includes the measurement light according to the difference in distance between the optical paths (2 × (difference in the height direction)). A component related to the phase difference is included. Therefore, the interference signal Sig obtained by photoelectrically converting the interference light IL includes information on the difference in the height direction (thickness direction) between the two measurement points P. Therefore, each interference signal Sig corresponding to each set of interference light obtained by optical homodyne interference using the reflected light RL that is common to each other is a measurement point P corresponding to the reflected light RL that is common to each other, and This includes gradient information at each measurement point corresponding to each reflected light RL subjected to optical homodyne interference. In the example shown in FIG. 1, the first interference light IL1 includes information on the height difference H1 between the measurement point P1 and the measurement point P2, and the second interference light IL2 is measured at the measurement point P2 and the measurement point P3. Information on the difference H2 in the height direction. The first and second interference signals Sig1 and Sig2 corresponding to the first and second interference lights IL1 and IL2 obtained by the optical homodyne interference using the reflected light RL2 common to each other are common to each other. The measurement point P2 corresponding to the reflected light RL2 and the gradient information at each of the measurement points P1 and P3 corresponding to the reflected lights RL1 and RL3 subjected to optical homodyne interference are included. Thus, in this embodiment, the gradient information is obtained for each of the three measurement points P1, P2, and P3 at one measurement location MP. Therefore, more specifically, the shape calculation unit 51 calculates the gradient Gr at the measurement point MP (three measurement points P1, P2, and P3 in the example shown in FIG. 1) as Gr = (ΔΦ × (λ / 2). ) / (2π)) / (distance between two measurement points P). And the shape calculation part 51 calculates | requires the surface shape of the measuring object Ob by connecting sequentially each gradient Gr of each measurement location MPn obtained by scanning according to a scanning order.

  The input unit 6 is a device for inputting data such as a command for instructing measurement start and attribute information of the measurement object Ob, for example, an operation panel or a keyboard provided with a plurality of input switches. . The output unit 7 is a device for outputting commands, data, measurement results, and the like received by the input unit 6. For example, a display device such as a CRT display, an LCD (liquid crystal display), an organic EL display, a plasma display, or a printer And the like. These input unit 6 and output unit 7 are connected to the arithmetic control unit 5.

  Next, the operation of the surface shape measuring apparatus SA in the present embodiment will be described. In the following description, for the sake of convenience of explanation, a case where there are three measurement points Pn at each measurement location MP will be described by taking the case shown in FIG. 1 as an example.

  When a power switch (not shown) is turned on, the surface shape measuring device SA is activated, and necessary parts are initialized by the arithmetic control unit 5. Then, for example, when a measurement object Ob of a plate-like body such as a semiconductor wafer is placed on the stage 4 and receives a command for instructing measurement start from the input unit 6, the arithmetic control unit 5 reads the surface shape of the measurement object Ob. Start measuring.

  First, the light source control unit 53 of the arithmetic control unit 5 drives the measurement light generation unit 1A to cause the single wavelength laser light source 1Aa to emit predetermined laser light. By the emission of a predetermined laser beam from the single wavelength laser light source 1Aa, the measurement light ML is emitted from the output terminal 1Ad of the measurement light generator 1A by the action of the optical system described above.

  Subsequently, the measurement light ML emitted from the output terminal 1Ad of the measurement light generation unit 1A propagates through the optical fiber and enters the measurement unit 2A (2B). In the measurement unit 2A (2B), the first and second interference lights IL1 and IL2 are generated from the incident measurement light ML by the action of the optical system described above, and emitted from the output terminal 2Ah (2Bg). Subsequently, the first and second interference lights IL1 and IL2 emitted from the output terminal 2Ah (2Bg) of the measurement unit 2A (2B) propagate through the multimode optical fiber and enter the phase difference detection unit 3A. The In the phase difference detection unit 3A, the first and second interference lights are obtained based on the first and second interference lights IL1 and IL2 for the set obtained by the optical homodyne interference using the reflected light RL2 common to each other. A phase difference ΔΦ between IL1 and IL2 is detected.

  And while this measurement part 2A (2B) and phase difference detection part 3A are performing such operation | movement, the stage control part 52 of the calculation control part 5 controls the measurement object Ob by controlling the stage 4. Is moved in the horizontal direction perpendicular to the height direction. For example, the stage control unit 52 of the arithmetic control unit 5 arranges a plurality of measurement points Pn at the measurement location MP along the movement direction, and the interval between two measurement points Pn−1 and Pn adjacent to each other along the movement direction. And the measurement point P3 at one measurement point MPtemp and the measurement point P1 at the measurement point MPnext measured next to the one measurement point MPtemp by scanning (moving), as described above. The stage 4 is moved so that it overlaps.

  Subsequently, when each phase difference ΔΦm of each measurement point MPm is acquired, the shape calculation unit 51 of the calculation control unit 5 obtains the gradient Grm at each measurement point MPm as described above, and each of these according to the scanning order. The surface shape of the measurement object Ob is obtained by connecting the gradient Grm at the measurement location MPm.

  Subsequently, the arithmetic control unit 5 outputs the obtained surface shape of the measurement object Ob to the output unit 7, and the output unit 7 displays the surface shape of the measurement object Ob.

  By operating in this way, the surface shape measuring device SA and the surface shape measuring method mounted on the surface shape measuring device SA according to this embodiment is a method using an optical homodyne interferometer. The surface shape of the object Ob can be measured. In the surface shape measuring device SA and the surface shape measuring method having such a configuration, three or more measurement points P on the measurement object Ob, three measurement points at one measurement point MP in the example shown in FIG. When the three reflected lights RL1, RL2, and RL3 reflected by P1, P2, and P3 are subjected to optical homodyne interference, the reflected light RL2 that is common to each other is used for optical interference. First and second interference lights IL1 and IL2 having phase information representing gradient information are obtained. For this reason, for example, the effects of vibrations such as vibration due to vertical movement on the stage 4 on which the measurement object Ob is placed, vibration due to holding fluctuations in the measurement optical system, and vibration of the measurement object Ob itself on the measurement result are offset. It can be almost erased. Therefore, the surface shape measuring device SA and the surface shape measuring method having such a configuration can measure the surface shape of the measuring object Ob with higher accuracy in the order of nm in a relatively short time.

  Further, in the above-described surface shape measurement apparatus SA in the present embodiment, the measurement light generation unit 1A and the measurement unit 2A (2B) constitute an optical homodyne interferometer and cause optical homodyne interference using the reflected light RL2 common to each other. A phase difference detector 3A for detecting a phase difference ΔΦ between the first and second interference lights IL1 and IL2 based on the first and second interference lights IL1 and IL2 obtained in this way, and a phase difference detector 3A And an arithmetic control unit 5 that calculates the surface shape of the measurement object Ob based on the phase difference ΔΦ between the first and second interference lights IL1 and IL2 output from. For this reason, since the surface shape measuring device SA of this embodiment includes the optical homodyne interferometer, the surface shape measuring device SA can be manufactured more simply.

  Further, in the surface shape measuring apparatus SA in the above-described embodiment, the measurement unit 2A (2B) uses the measurement light ML emitted from the light source unit 1A, for example, one light branching unit of the diffraction grating 2Ac or the branching unit 2Bb-2. The reflected light RL1 in the divided first measurement light ML1 and the reflected light RL2 in the divided second measurement light ML2 are subjected to optical homodyne interference, and the divided second measurement is performed. The reflected light RL2 in the light ML2 and the divided reflected light RL3 in the third measurement light ML3 are subjected to optical homodyne interference. For this reason, the surface shape measuring apparatus SA of the present embodiment as described above divides the light emitted from the light source unit 1A into three by one light branching means in the measuring unit 2A (2B), so that the surface can be more simply The shape measuring device SA can be manufactured. In such a surface shape measuring apparatus SA of this embodiment, the light branching means is composed of a diffraction grating 2Ac or an optical branching part 2Bb-2 which is an optical waveguide type optical branching device. Compared with the case where the optical parts (optical elements) are combined, the optical path can be manufactured more strictly, the optical path adjustment after assembly is unnecessary, and the size can be reduced. For this reason, the surface shape measuring apparatus SA in the present embodiment can be portable.

  In the surface shape measuring apparatus SA in the above-described embodiment, the measurement unit 2A (2B) includes an optical waveguide type optical element in which optical waveguides having different refractive indexes are formed on the base material 2Ai (2Bh). For this reason, since the surface shape measuring apparatus SA of this embodiment includes the optical waveguide type optical element and constitutes the measuring unit 2A (2B), air fluctuations can be removed and temperature fluctuations can be reduced. Interference light IL can be obtained more stably. In addition, since the surface shape measuring apparatus SA of this embodiment includes the optical waveguide type optical element and constitutes the measurement unit 2A (2B), when the plurality of optical components (optical elements) are combined. In comparison, the optical path can be manufactured more strictly, and the optical path adjustment after assembly is not necessary, and the size can be reduced. For this reason, also from this point, the surface shape measuring device SA in the present embodiment can be portable.

  Next, another embodiment will be described.

(Second Embodiment)
The surface shape measurement apparatus SA in the first embodiment is an apparatus that generates interference light IL by optical homodyne interference and measures the surface shape of the measurement object Ob based on the interference light IL. The surface shape measuring device SB is a device that generates interference light IL by optical heterodyne interference and measures the surface shape of the measurement object Ob based on the interference light IL.

  FIG. 4 is a diagram illustrating a configuration of a surface shape measuring apparatus according to the second embodiment. FIG. 5 is a diagram illustrating a configuration of a measurement light generation unit in the surface shape measurement apparatus illustrated in FIG. 4. FIG. 6 is a diagram illustrating a configuration of a measurement unit in the surface shape measurement apparatus illustrated in FIG. 4.

  The surface shape measuring device SB of the second embodiment is a device that measures a surface shape that is a change in the height direction (thickness direction) of the measurement object Ob. For example, as shown in FIG. Unit 1B, measurement unit 2C, phase detection unit 3B, stage (mounting table) 4, calculation control unit 5, input unit 6 and output unit 7, and is configured to be measured by stage 4 The surface of the measurement object Ob is scanned by moving Ob in the horizontal direction, and the surface shape of the measurement object Ob over a predetermined range is measured.

  The measurement light generation unit 1B is a device that generates measurement light ML that is predetermined coherent light and measures the surface shape of the measurement object Ob by the optical heterodyne interferometry. The measurement light ML is single wavelength light having a predetermined wavelength λ (frequency f) set in advance, and is polarized light having a predetermined polarization plane set in advance. The measurement light ML includes two first and second measurement lights MLf1 and MLf2 having different wavelengths (frequencies) from each other in order to measure the measurement object Ob from both sides by optical heterodyne interferometry. For example, as shown in FIG. 5, the measurement light generation unit 1B includes a light source unit 1Ba, an optical isolator 1Bb, an optical branching unit 1Bc, polarizers 1Bd and 1Bg, and optical wavelength shifters 1Be, 1Bh, 2 It comprises output terminals 1Bf and 1Bi.

  The light source unit 1Ba is a device that emits light L, and includes, for example, a single wavelength laser similar to the light source unit 1Aa of the first embodiment. The optical isolator 1Bb is an optical component similar to the optical isolator 1Ab of the first embodiment. The optical branching section 1Bc is an optical component that divides incident light into two lights in terms of optical power and emits them respectively. For example, a micro-optical element type optical branching coupler such as a half mirror (semi-transparent mirror) or a molten fiber An optical fiber type optical branch coupler, an optical waveguide type optical branch coupler, or the like can be used. In this embodiment, a half mirror is used for the optical branching section 1Bc. The polarizers 1Bd and 1Bg are optical components similar to the polarizer 1Ac of the first embodiment. The optical wavelength shifters 1Be and 1Bh are optical components that generate light having a wavelength (frequency) different from the wavelength (frequency) of the incident light by shifting the wavelength of the incident light (changing the frequency of the incident light). An acoustooptic modulator that shifts the wavelength of incident light by utilizing the acoustooptic effect is used. The output terminals 1Bf and 1Bi are terminals for emitting light from the optical component. For example, the output terminals 1Bf and 1Bi are connectors for connecting optical fibers similar to the output terminal 1Ad of the first embodiment.

  With respect to one light branched by the optical branching unit 1Bc, the light source unit 1Ba, the optical isolator 1Bb, the optical branching unit 1Bc, the polarizer 1Bd, the wavelength shifter 1Be, and the output terminal 1Bf have the optical axes aligned with each other, The light source 1Ba, the optical isolator 1Bb, the optical branching unit 1Bc, the polarizer 1Bg, the wavelength shifter 1Bh, and the output terminal 1Bi are arranged in this order according to the propagation direction and the other light branched by the optical branching unit 1Bc. Are arranged in this order according to the propagation direction of light with their optical axes aligned with each other.

  In such a measurement light generation unit 1B, the laser light L emitted from the single wavelength laser of the light source unit 1Ba enters the optical branching unit 1Bc via the optical isolator 1Bb, and the first and second laser beams L1, L2 It is distributed to two. The first laser light L1 is incident on the polarizer 1Bd, becomes laser light having a predetermined polarization plane (s-polarized laser light or p-polarized laser light), and is incident on the wavelength shifter 1Be. The wavelength (frequency) of the laser light having the predetermined polarization plane is shifted (changed) by the optical wavelength shifter 1Be, and is measured light MLf1 having the predetermined frequency f1 and emitted from the output terminal 1Be. The measurement light MLf1 is incident on the measurement unit 2C. On the other hand, the second laser light L is incident on the polarizer 1Bg, becomes laser light having a predetermined polarization plane (s-polarized laser light or p-polarized laser light), and enters the wavelength shifter 1Bh. The wavelength (frequency) of the laser light having the predetermined polarization plane is shifted (changed) by the optical wavelength shifter 1Bh, and is measured light MLf2 having a predetermined frequency f2 (≠ f1) and emitted from the output terminal 1Bi. The The measurement light MLf2 is incident on the measurement unit 2C. The frequency difference Δf between the frequency f1 of the measurement light MLf1 and the frequency f2 of the measurement light MLf2 after the frequency change (after the wavelength shift) is not particularly limited, but is, for example, several tens of kHz from the viewpoint of interference by optical heterodyne interferometry It is a value of about several MHz.

  In the present embodiment, each of the laser beam having a predetermined polarization plane generated from the first laser beam L1 and the laser beam having a predetermined polarization plane generated from the second laser beam L2 is converted into a wavelength shifter 1Be. Each wavelength is shifted by 1Bh, but in order to cause interference by optical heterodyne, it is sufficient that there is a predetermined frequency difference Δf between the frequency f1 of the measurement light MLf1 and the frequency f2 of the measurement light MLf2. The generation unit 1B may be configured to shift the wavelength of only one of the laser beams.

  An optical fiber is used for the connection between the measurement light generation unit 1B and the measurement unit 2C, similarly to the connection between the measurement light generation unit 1A and the measurement unit 2A in the first embodiment. The measurement lights MLf1 and MLf2 emitted from the output terminals 1Bf and 1Bi of the measurement light generation unit 1B are respectively guided by two optical fibers and enter the measurement unit 2C.

  The measurement unit 2C receives each measurement light ML (MLf1, MLf2) from the measurement light generation unit 1B, and includes information on the surface shape of the measurement object Ob by optical heterodyne interferometry using the measurement light MLf1 and MLf2. An apparatus for obtaining an optical signal. Such a measurement unit 2C is configured to measure a plurality of measurement points P (P1, P2, P2, P2, P2) in the measurement object Ob in the measurement by one irradiation of the measurement light ML (MLf1, MLf2) to one measurement point MP. P3,..., Pn) are irradiated with the measurement light ML (ML1, ML2, ML3,..., MLn), respectively, and the measurement light ML from the measurement light generation unit 1B is irradiated with three or more measurement lights. ML1, ML2, ML3,..., MLn, and a plurality of measurement lights ML1, ML2, ML3,. A plurality of reflected lights RL1, RL2, RL3,... Irradiating the points P1, P2, P3,..., Pn and reflected at the plurality of measurement points P1, P2, P3,. , RLn) And a plurality of optical interference units that cause optical interference between the pair of reflected lights RL, and at least one set of the optical interference units in the plurality of optical interference units is configured to cause optical interference using the common reflected light RL. Has been.

  Here, in the present embodiment, since the optical interference is optical heterodyne interference, the pair of reflected lights RL is light obtained by reflecting two measurement lights MLf1 and MLf2 having different frequencies from each other on the surface of the measurement object Ob. Furthermore, in the present embodiment, reflected light RL that is common to each other is used in the set. Therefore, if the reflected light RL common to each other is the light reflected by the measurement light MLf1 on the surface of the measurement object Ob, the reflected light RL that interferes with the measurement light ML is reflected by the measurement light MLf2 on the surface of the measurement object Ob. Light. For this reason, the light dividing unit divides the measurement light MLf2 into a plurality of measurement lights MLf2, not the measurement light MLf1 for obtaining the reflected light RL common to each other. Further, if the reflected light RL that is common to each other is the light reflected by the measurement light MLf2 on the surface of the measurement object Ob, the reflected light RL that interferes with the optical heterodyne is reflected by the measurement light MLf1 on the surface of the measurement object Ob. Light. For this reason, the light splitting unit splits the measurement light MLf1 into a plurality of measurement lights MLf1, not the measurement light MLf2 for obtaining the reflected light RL common to each other.

  More specifically, for example, as shown in FIG. 6, the measurement unit 2C includes an optical branching unit 2Ca, an input terminal 2Cb, an input-side waveguide 2Cc, an objective lens 2Cd, a half mirror 2Cf, and a condenser lens. 2Cg, 2Cj, an output side waveguide 2Ch, an output terminal 2Ci, a reference side waveguide 2Ck, and a reference output terminal 2Cl, and these input side waveguide 2Cc, output side waveguide 2Ch, and reference side The waveguide 2Ck is provided by forming optical waveguides having different refractive indexes on the substrate 2Cm.

  The optical branching unit 2Ca is configured to measure a plurality of measurement points P (P1, P2, P3, three or more) in the measurement object Ob in the measurement by irradiating one measurement light ML (MLf1, MLf2) to one measurement point MP. .., Pn) are irradiated with the measurement light ML (ML1, ML2, ML3,..., MLn), respectively, and the measurement light ML from the measurement light generation unit 1B is irradiated with three or more measurement lights ML1, ML2, ML3,..., MLn. In this embodiment, as described above, since the optical interference is optical heterodyne interference, the optical branching unit 2Ca uses the measurement light MLf2 (or measurement light MLf1) for obtaining the reflected light RL common to each other. Instead, the measurement light MLf1 (or measurement light MLf2) is distributed to a plurality of measurement lights MLf1. The optical branching portion 2Ca may be provided on the base material 2Cm by forming an optical waveguide. However, in this embodiment, an individual optical element, for example, an optical fiber type optical branching coupler of a molten fiber is used. Yes. In the example illustrated in FIG. 6, the optical branching unit 2Ca includes an optical fiber branching unit 2Ca-1 that is provided at an exit end portion of the optical fiber that guides the measurement light MLf1 and that divides the optical fiber into two by a molten fiber. The two optical fibers 2Ca-2 and 2Ca-3a branched by the optical fiber branching portion 2Ca-1 and the optical fiber 2Ca-4 provided at the exit end portion of the optical fiber that guides the measurement light MLf1 are provided. In these optical fibers 2Ca-2 to 2Ca-4, the optical fiber 2Ca-4 that guides the measurement light MLf2 for obtaining the reflected light RL common to each other is located in the center, and guides the measurement light MLf1. The two optical fibers 2Ca-2 and 2Ca-3 are connected to the input terminal 2Cb so as to be positioned on both sides of the optical fiber 2Ca-4. The optical fiber branching portion 2Ca-1 and the optical fibers 2Ca-2, 2Ca-3 are, for example, optical fiber type optical branching couplers connected to the exit end portion of the optical fiber that guides the measurement light MLf2. Alternatively, for example, the exit end portion of the optical fiber that guides the measurement light MLf2 may be processed into an optical fiber type optical branching coupler. The optical fiber 2Ca-4 may be, for example, an optical fiber connected to an emission end portion of the optical fiber that guides the measurement light MLf2, and may be, for example, an emission in the optical fiber that guides the measurement light MLf2. The end part itself may be sufficient.

  The base material 2Cm is a plate-like member (substrate) formed of a material having a predetermined refractive index, and an input terminal 2Cb, an output terminal 2Ci, and a reference output terminal 2Cl are disposed at predetermined positions on the outer peripheral surface. ing. In the example shown in FIG. 6, the base material 2Cm has a substantially rectangular parallelepiped shape, and an input terminal 2Cb, an output terminal 2Ci, and a reference output terminal 2Cl are disposed on the upper surface thereof. As described above, the optical fibers 2Ca-2 to 2Ca-4 in the optical branching section 2Ca are connected to the input terminal 2Cb, respectively.

  The base material 2Cm has an input-side waveguide 2Cc extending from the position where the input terminal 2Cb of the base material 2Cm is disposed only slightly (for example, 0.3 mm) than the predetermined refractive index of the base material 2Cm. To about 3%). The input-side waveguide 2Cc guides the measurement light ML (MLf1, MLf2) incident from one end thereof via the input terminal 2Cb and from the measurement light generation unit 1B. The objective lens 2Cd is disposed. In the example shown in FIG. 6, the input-side waveguide 2 </ b> Cc faces from the position where the input terminal 2 </ b> Cb is disposed on the upper surface of the base material 2 </ b> Cm to the lower surface along one side surface of the base material 2 </ b> Cm, and is substantially at a predetermined position. It is a substantially L-shape that bends about 90 degrees by an arc and extends along the lower surface. The input-side waveguide 2Cc has a number corresponding to the number of measurement lights MLf1 and MLf2 emitted from the optical branching section 2Ca. In the example shown in FIG. 6, the measurement light MLf1 guided by the optical fiber 2Ca-2 of the optical branching unit 2Ca, the measurement light MLf2 guided by the optical fiber 2Ca-4 of the optical branching unit 2Ca, and the optical branching in the order of arrangement. Since the measurement light MLf1 is guided by the optical fiber 2Ca-3 of the section 2Ca, the input-side waveguide 2Cc includes three waveguide sections 2Cc-1 to 2Cc-3. . The optical fiber 2Ca-2 of the optical branching part 2Ca is connected to the waveguide part 2Cc-1 via the input terminal 2Cb, and the optical fiber 2Ca-4 of the optical branching part 2Ca is connected to the waveguide part 2Cc via the input terminal 2Cb. -2 and the optical fiber 2Ca-3 of the optical branching section 2Ca is connected to the waveguide section 2Cc-3 via the input terminal 2Cb. The three waveguide portions 2Cc-1 to 2Cc-3 in the input-side waveguide 2Cc are not parallel at the portion bent by about 90 degrees, but are generally arranged in parallel with each other. These three waveguide portions 2Cc-1 to 2Cc-3 have the same optical distance (optical path length) from the incident end connected to the input terminal 2Cb to the exit end connected to the objective lens 2Cd. As shown, the waveguide portion 2Cc-1 and the waveguide portion 2Cc-2 located on the inner side in the portion bent at about 90 degrees are in the plane of the base 2Cm with respect to the extending direction of the input-side waveguide 2Cc. Optical path redundant portions CV2-1 and CV2-2 that are curved (bent) in a direction orthogonal to each other are provided. And the optical path redundant part CV2-1 provided in the innermost waveguide part 2Cc-1 has an optical distance (optical path length) longer than the optical path redundant part CV-1 provided in the central waveguide part 2Cc-2. .

  The objective lens 2Cd includes a plurality of lenses corresponding to the number of the plurality of measurement lights MLf1 and MLf2 so as to give a lens action to each of the plurality of measurement lights MLf1 and MLf2 guided by the input-side waveguide 2Cc. The half mirror 2Cf is disposed on the emission side. In the example illustrated in FIG. 6, the objective lens 2Cd is to apply a lens action to each of the measurement lights MLf1, MLf2, and MLf1 emitted from the three waveguide portions 2Cc-1 to 2Cc-3 in the input-side waveguide 2Cc. It is configured with three lenses. Each lens of the objective lens 2Cd collects the measurement lights MLf1, MLf2, and MLf12 emitted from the three waveguide portions 2Cc-1 to 2Cc-3 in the input-side waveguide 2Cc, and collects each of the collected measurement lights. MLf1, MLf2, and MLf1 are made incident on the half mirror 2Cf.

  The half mirror 2Cf is an optical component that divides incident light into two lights in terms of optical power and emits them respectively. One of the distributed lights passes through the half mirror 2Cf and is emitted in the same direction. The other distributed light is reflected by the half mirror 2Cf and emitted in a direction perpendicular to the direction (a direction perpendicular to the direction).

  The input-side waveguide 2Cc and the objective lens 2Cd are arranged so that their optical axes coincide with each other, and the half mirror 2Cf is arranged so that the mirror surface intersects the optical axis at an angle of 45 degrees. Yes.

  In the optical branching unit 2Ca, the input terminal 2Cb, the input-side waveguide 2Cc, the objective lens 2Cd, and the half mirror 2Cf having such a configuration, the measurement light ML (MLf1, MLf2) from the measurement light generation unit 1B is transmitted from the optical branching unit 2Ca. One measurement light MLf1 is distributed by the optical fiber branching section 2Ca-1, and three waveguides in the input-side waveguide 2Cc from the three optical fibers 2Ca-2 to 2Ca-4 in the optical branching section 2Ca through the input terminal 2Cb. It is incident on each of the parts 2Cc-1 to 2Cc-3. The measurement light ML1 (MLf1), ML2 (MLf2), and ML3 (MLf1) incident on the respective waveguide portions 2Cc-1 to 2Cc-3 in the input-side waveguide 2Cc are converted into the respective waveguide portions 2Cc-1 to 2Cc−. 3 are respectively guided through the waveguide portions 2Cc-1 to 2Cc-3 and are incident on the respective lenses of the objective lens 2Cd. The three measurement lights ML1, ML2, and ML3 incident on the objective lens 2Cd are subjected to the lens action and are incident on the half mirror 2Cf. In the half mirror 2Cf, these three measurement lights ML1, ML2, and ML3 are distributed into two, and this one distributed light passes through the half mirror 2Cf and exits in the same direction, and the other distributed light Is reflected by the half mirror 2Cf, and its optical path is bent 90 degrees and emitted. Here, in the objective lens 2Cd, the three measurement lights ML1, ML2, and ML3 that have passed through the half mirror 2Cf and exited in the same direction become parallel lights that are parallel to each other, and the optical path is bent 90 degrees by the half mirror 2Cf. The three measurement lights ML1, ML2, and ML3 that are emitted are configured to have a lens action so as to become parallel lights that are parallel to each other.

  Three parallel measurement lights ML1, ML2, and ML3 that have passed through the half mirror 2Cf and exited in the same direction are incident on the condenser lens 2Cj.

  Then, the three parallel measurement lights ML1, ML2, and ML3 reflected by the half mirror 2Cf and emitted from the half mirror 2Cf are emitted from the measurement unit 2C, and are measured at one measurement point MP on the surface of the measurement object Ob. The points P1, P2, and P3 are respectively irradiated and reflected. Three reflected lights (regular reflection components of reflected light) RL (RL1, RL2, RL3) reflected at three measurement points P1, P2, and P3 on the surface of the measurement object Ob are incident on the measurement unit 2C. , And enters the condenser lens 2Cg through the half mirror 2Cf. The reflected light RL1 is light reflected from the measurement light MLf1 at the measurement point P1, and has a frequency f1. The reflected light RL2 is light reflected from the measurement light MLf2 at the measurement point P2, and has a frequency f2. The reflected light RL3 is the light reflected by the measurement light MLf1 at the measurement point P3, and has a frequency f1.

  The condensing lens 2Cg is the same as the condensing lens 2Af and the condensing lens 2Be in the first embodiment, and its optical axis is orthogonal to the optical axes of the input-side waveguide 2Cc and the objective lens Cd, and The mirror surface of the half mirror 2Cf is disposed so as to intersect at an angle of −45 degrees (135 degrees). The condenser lens 2Cg has the number of reflected lights RL (RL1, RL2, RL3) so as to give a lens action to each of the plurality of reflected lights RL (three reflected lights RL1, RL2, RL3 in the example shown in FIG. 6). A corresponding number of lenses (three lenses in this example) are provided, and on the exit side, the output-side waveguide 2Ch is slightly less than the predetermined refractive index of the base material 2Cm (for example, 0. 0. It is formed by increasing it to about 3 to 3%.

  The output-side waveguide 2Ch is the same as the output-side waveguide 2Ag and the output-side waveguide 2Bf in the first embodiment, and each reflected light RL (RL1, in the example shown in FIG. 6) that is incident from the condenser lens 2Cg. RL2 and RL3) are guided, the pair of reflected lights RL in the plurality of reflected lights RL are caused to interfere with each other, and the plurality of interference lights IL are guided. Here, in the present embodiment, at least one set of interference lights IL among the plurality of interference lights IL is generated by causing optical interference using the reflected light RL common to each other. More specifically, the output-side waveguide 2Ch is the same as the output-side waveguide 2Ag and the output-side waveguide 2Bf in the first embodiment, and the three waveguide portions 2Ch-1, 2Ch-2, 2Ch-3. And a branch part 2Ch-4, a junction part 2Ch-5, 2Ch-6, a waveguide part 2Ch-7, and a waveguide part 2Ch-8.

  In the half mirror 2Cf, the condensing lens 2Cg, the output-side waveguide 2Ch, and the output terminal 2Ci having such a configuration, in the example illustrated in FIG. 6, the reflection is performed at three measurement points P1, P2, and P3 on the surface of the measurement object Ob. The three reflected lights (regular reflection components of the reflected light) RL (RL1, RL2, RL3) are incident on the measurement unit 2C and are incident on the respective lenses of the condenser lens 2Cg via the half mirror 2Cf. The lenses of the condenser lens 2Cg cause the reflected lights RL1, RL2, and RL3 to enter the three waveguide portions 2Ch-1, 2Ch-2, and 2Ch-3 in the waveguide portion 2Ch, respectively. That is, the respective lenses of the condenser lens 2Cg are for waveguide coupling with respect to the three waveguide portions 2Ch-1, 2Ch-2, 2Ch-3 in the output-side waveguide 2Ch. The reflected light RL2 incident on the central waveguide section 2Ch-2 propagates through the waveguide section 2Ch-2, is guided by the waveguide section 2Ch-2, and is distributed by the branch section 2Ch-4. One reflected light RL2 (RL2-1) distributed by the branching section 2Ch-4 is guided to the joining section 2Ch-5, and the other reflected light RL2 (RL2-2) is sent to the joining section 2Ch-6. Light is guided. Further, the reflected light RL1 incident on the waveguide portion 2Ch-1 propagates through the waveguide portion 2Ch-1, is guided by the waveguide portion 2Ch-1, and is guided to the junction portion 2Ch-5. The reflected light RL3 incident on the waveguide section 2Ch-3 propagates through the waveguide section 2Ch-3, is guided by the waveguide section 2Ch-3, and is guided to the junction section 2Ch-6. In the merging section 2Ch-5, the reflected light RL2 (frequency f2) guided as described above and the reflected light RL1 (frequency f1) are combined, and optical heterodyne interference is performed, so that the first interference light IL1 (= RL1 + RL2). Is generated. The first interference light IL1 is guided from the merging portion 2Ch-5 to the waveguide portion 2Ch-7, propagates through the waveguide portion 2Ch-7, is guided by the waveguide portion 2Ch-7, and is output to the output terminal 2Ci. Is incident on. Then, in the junction 2Ch-6, the reflected light RL2 (frequency f2) and the reflected light RL3 (frequency f1) guided as described above are combined and subjected to optical heterodyne interference to generate the second interference light IL2 (= RL2 + RL3) is generated. The second interference light IL2 is guided from the merging portion 2Ch-6 to the waveguide portion 2Ch-8, propagates through the waveguide portion 2Ch-8, is guided by the waveguide portion 2Ch-8, and is output to the output terminal 2Ci. Is incident on. The first and second interference lights IL1 and IL2 are optical signals including information on the surface shape of the measurement object Ob. The first and second interference lights IL1 and IL2 are incident on the phase detection unit 3B from the measurement unit 2C via the output terminal 2Ci.

  The condenser lens 2Cj is disposed so that its optical axis coincides with the optical axes of the input-side waveguide 2Cc and the objective lens Cd. The condensing lens 2Cj has a plurality of measurement lights ML (in the example shown in FIG. 6, three measurement lights ML1, ML2, and ML3) that pass through the half mirror 2Cf as they are to provide a lens action to each of the measurement lights ML (ML1, ML, RL2, RL3) corresponding to the number of lenses (three lenses in this example), and on the exit side, the reference-side waveguide 2Ck is higher than the predetermined refractive index of the substrate 2Cm. It is formed by increasing it to a very small amount (for example, about 0.3 to 3%). The three measurement beams ML1, ML2, and ML3 that have passed through the half mirror 2Cf as they are are referred to as reference beams MLref1, MLref2, and MLref3.

  The reference-side waveguide 2Ck guides each reference light MLref (MLref1, MLref2, MLref3 in the example shown in FIG. 6) incident from the condenser lens 2Cj, and corresponds to the plurality of interference lights IL. The pair of reference lights MLref in the plurality of reference lights MLref are caused to interfere with each other to guide the plurality of reference interference lights ILref. Here, in the present embodiment, at least one set of the interference lights IL among the plurality of interference lights IL is generated by causing optical interference using the reflected light RL that is common to each other. In addition, at least one set of the reference interference light ILref among the plurality of reference interference lights ILref is generated by causing optical interference using the common reference light RLref. More specifically, the reference-side waveguide 2Ck extends substantially along the lower surface of the base material 2Cm, is bent approximately 90 degrees by a substantially arc at a predetermined position, and extends substantially along the other side surface to the upper surface. Three waveguide sections 2Ck-1, 2Ck-2, 2Ck-3, which are L-shaped and extend from the exit side of the three lenses corresponding to the three reference lights MLref1, MLref2, and MLref3 in the condenser lens 2Cj, respectively. , A branching part 2Ck-4 that branches the central waveguide part 2Ck-2 into two, and a joining part 2Ck that joins the one waveguide part branched by the branching part 2Ck-4 and the waveguide part 2Ck-1 −5, the other waveguide section branched at the branch section 2Ck-4, and the merge section 2Ck-6 that merges the waveguide section 2Ck-3, and the merge section 2Ck-5 extends to the reference output terminal 2Cl. Waveguide part 2C -7, and a extending from the confluence portion 2CK-6 and a waveguide portion 2CK-8 which leads to an output terminal 2Cl.

  In the half mirror 2Cf, the condensing lens 2Cj, the reference-side waveguide 2Ck, and the reference output terminal 2Cl configured as described above, a plurality of reference lights MLref (MLref1, MLref2, and MLref3 in the example illustrated in FIG. 6) that have passed through the half mirror 2Cf as they are. , And enters the respective lenses of the condenser lens 2Cj. In the example shown in FIG. 6, each of the condensing lenses 2Cj enters each of the reference lights MLref1, MLref2, and MLref3 into the three waveguide sections 2Ck-1, 2Ck-2, and 2Ck-3 in the waveguide section 2Ck. Let That is, each lens of the condensing lens 2Cj is for waveguide coupling with respect to the three waveguide portions 2Ck-1, 2Ck-2, and 2Ck-3 in the reference-side waveguide 2Ck. The reference light MLref2 incident on the central waveguide section 2Ck-2 propagates through the waveguide section 2Ck-2, is guided by the waveguide section 2Ck-2, and is distributed by the branch section 2Ck-4. One reference light MLref2 (MLref2-1) distributed by the branching unit 2Ck-4 is guided to the joining unit 2Ck-5, and the other reference light MLref2 (MLref2-2) is sent to the joining unit 2Ck-6. Light is guided. The reference light MLref1 incident on the waveguide section 2Ck-1 propagates in the waveguide section 2Ck-1, is guided by the waveguide section 2Ck-1, and is guided to the junction section 2Ck-5. The reference light MLref3 incident on the waveguide section 2Ck-3 propagates in the waveguide section 2Ck-3, is guided by the waveguide section 2Ck-3, and is guided to the junction section 2Ck-6. In the merging unit 2Ck-5, the reference light MLref2 (frequency f2) guided as described above and the reference light MLref1 (frequency f1) are combined and subjected to optical heterodyne interference to generate the first reference interference light ILref1 (= MLref1 + MLref2). ) Is generated. The first reference interference light ILref1 is guided from the junction 2Ck-5 to the waveguide 2Ck-7, propagates through the waveguide 2Ck-7, is guided by the waveguide 2Ck-7, and is a reference output. Incident on the terminal 2Cl. In the merging unit 2Ck-6, the reference light MLref2 (frequency f2) guided as described above and the reference light MLref3 (frequency f1) are combined and subjected to optical heterodyne interference to generate the second reference interference light ILref2 ( = MLref2 + MLref3) is generated. The second reference interference light ILref2 is guided from the merging portion 2Ck-6 to the waveguide portion 2Ck-8, propagates through the waveguide portion 2Ck-8, is guided by the waveguide portion 2Ck-8, and is output as a reference. Incident on the terminal 2Cl. These first and second reference interference lights ILref1 and ILref2 are optical signals for correcting the first and second interference lights IL1 and IL2 in order to remove noise from the first and second interference lights IL1 and IL2. It is. The first and second reference interference lights ILref1 and ILref2 are incident on the phase detection unit 3B from the measurement unit 2C via the reference output terminal 2Cl.

  Returning to FIG. 4, as in the first embodiment, the measurement unit 2 </ b> C and the phase detection unit 3 </ b> B may be single mode optical fibers, but from the viewpoint of optical axis adjustment and superiority in the amount of propagating light. Connected by multimode optical fiber. That is, in the present embodiment, a plurality of interference lights IL emitted from the measurement unit 2C and a plurality of reference interference lights ILref corresponding thereto, in the examples shown in FIGS. 4 and 6, the first and second interference lights IL1, IL2 In addition, the first and second reference interference lights ILref1 and ILref2 are guided by the multimode optical fiber and enter the phase detector 3B.

  The phase detection unit 3B performs phase detection on the plurality of interference lights IL and the plurality of reference interference lights ILref emitted from the measurement unit 2C, uses the plurality of reference interference lights ILref to remove noise, and reflects reflected light that is common to each other. A phase difference ΔΦ between a pair of interference lights obtained by optical heterodyne interference using RL is detected. Then, the phase detector 3B outputs the detected phase difference ΔΦ to the arithmetic control unit 5. More specifically, as shown in FIG. 4, the phase detection unit 3B includes an interference light photoelectric conversion unit 3Ba (3Ba1, 3Ba2), a reference interference light photoelectric conversion unit 3Bb (3Bb1, 3Bb2), It comprises a phase detector 3Bc for interference light, a phase detector 3Bd for reference interference light, and a correction unit 3Be.

  The photoelectric conversion units 3Ba and 3Bb are configured to include photoelectric conversion elements such as photodiodes that convert an electric signal having a signal level corresponding to the amount of incident light and output the electric signal. The photoelectric conversion unit 3Ba is prepared according to the number of interference lights IL obtained by the measurement unit 2C, and receives each of the plurality of interference lights IL from the measurement unit 2C, and each electric signal having a signal level corresponding to each light quantity. A signal is output as each interference signal Sig. In the present embodiment, since the interference light IL is two, two photoelectric conversion units 3Ba1 and 3Ba2 are prepared. Each of the photoelectric conversion units 3Ba1 and 3Ba2 transmits the two first and second interference lights IL1 and IL2 emitted from the output terminal 2Ci of the measurement unit 2C through the multimode optical fibers and the input terminals (not shown). The first and second interference signals Sig1 and Sig2 are output to the phase detector 3Bc according to the respective light amounts of the interference lights IL1 and IL2, respectively. Similarly, the photoelectric conversion unit 3Bb is prepared according to the number of reference interference lights ILref obtained by the measurement unit 2C, receives a plurality of reference interference lights ILref from the measurement unit 2C, and responds to each light quantity. Each electric signal at the signal level is output as each reference interference signal Ref. In the present embodiment, since the reference interference light ILref is two, two photoelectric conversion units 3Bb1 and 3Bb2 are prepared. Each of the photoelectric conversion units 3Bb1 and 3Bb2 receives two first and second reference interference lights ILref1 and ILref2 emitted from the reference output terminal 2Cl of the measurement unit 2C as multimode optical fibers and input terminals (not shown). The first and second reference interference signals Ref1 and Ref2 are output to the phase detector 3Bd according to the respective light amounts of the reference interference lights ILref1 and ILref2, respectively.

  The phase detector 3Bc receives a plurality of interference signals Sig from the photoelectric conversion unit 3Ba and relates to a set of interference lights IL obtained by optical heterodyne interference using the reflected light RL common to each other. It is a device for detecting the phase difference ΔΦs between the two. In the example shown in FIG. 4, the phase detector 3Bc receives the first and second interference signals Sig1 and Sig2 from the photoelectric conversion units 3Ba1 and 3Ba2, and the phase detector 3Bc is between the first interference signal Sig1 and the second interference signal Sig2. The phase difference ΔΦs is detected. Then, the phase detector 3Bc outputs the detected phase difference ΔΦs to the correction unit 3Be.

  The phase detector 3Bd receives a plurality of reference interference signals Ref from the photoelectric conversion unit 3Bb and relates to a plurality of reference interference lights ILref obtained by optical heterodyne interference using the common reference light MLref. This is a device for detecting a phase difference ΔΦr between reference interference signals Ref. The common reference light MLref is the reference light MLref corresponding to the measurement light ML used to obtain the common reflected light RL. In the example shown in FIG. 4, the phase detector 3Bd receives the first and second reference interference signals Ref1 and Ref2 from the photoelectric conversion units 3Bb1 and 3Bb2, and the first reference interference signal Ref1 and the second reference interference signal Ref2 The phase difference ΔΦr is detected. Then, the phase detector 3Bd outputs the detected phase difference ΔΦr to the correction unit 3Be.

  The correction unit 3Be includes a plurality of correction light sources corresponding to the set of interference lights in order to remove noise in the phase difference ΔΦs between the sets of interference lights obtained by performing optical heterodyne interference using the common reflected light RL. By using the phase difference ΔΦr between the reference interference lights, the phase difference ΔΦs in the set of interference lights is corrected. For example, the correction unit 3Be obtains the correction by obtaining a difference between a phase difference ΔΦs between the sets of interference light and a phase difference ΔΦr between a plurality of reference interference lights corresponding to the sets of interference light. I do.

  The stage 4, the calculation control unit 5, the input unit 6 and the output unit 7 are the same as the stage 4, the calculation control unit 5, the input unit 6 and the output unit 7 in the surface shape measuring apparatus SA of the first embodiment, respectively. Since there is, explanation is omitted.

  Next, the operation of the surface shape measuring apparatus SB in this embodiment will be described. In the following description, for the sake of convenience of explanation, a case where there are three measurement points Pn at each measurement point MP will be described by taking the case shown in FIG. 4 as an example.

  When a power switch (not shown) is turned on, the surface shape measuring device SB is activated and necessary parts are initialized by the arithmetic control unit 5. Then, for example, when a measurement object Ob of a plate-like body such as a semiconductor wafer is placed on the stage 4 and receives a command for instructing measurement start from the input unit 6, the arithmetic control unit 5 reads the surface shape of the measurement object Ob. Start measuring.

  First, the light source control unit 53 of the calculation control unit 5 drives the measurement light generation unit 1B to cause the single wavelength laser light source 1Ba to emit predetermined laser light. The measurement light MLf1 and MLf2 are emitted from the output terminals 1Bf and 1Bi of the measurement light generation unit 1B by the action of the optical system described above by the emission of the predetermined laser light from the single wavelength laser light source 1Aa.

  Subsequently, the measurement lights MLf1 and MLf2 respectively emitted from the output terminals 1Bf and 1Bi of the measurement light generation unit 1B propagate through the optical fibers and enter the measurement unit 2C. In the measurement unit 2C, the first and second interference lights IL1 and IL2 and the first and second reference interference lights ILref1 and ILref2 are generated from the incident measurement lights MLf1 and MLf2 by the action of the optical system described above. The first and second interference lights IL1 and IL2 are emitted from the output terminal 2Ci, and the first and second reference interference lights ILref1 and ILref2 are emitted from the output terminal 2Cl. Subsequently, the first and second interference lights IL1 and IL2 emitted from the output terminal 2Ci of the measurement unit 2C propagate through the multimode optical fiber and enter the phase detection unit 3B. Then, the first and second reference interference lights ILref1 and ILref2 emitted from the output terminal 2Cl of the measurement unit 2C propagate through the multimode optical fiber and enter the phase detection unit 3B. In the phase detection unit 3B, the first and second interferences are obtained by phase detection of the first and second interference lights IL1 and IL2 for a set obtained by optical heterodyne interference using the reflected light RL2 common to each other. The phase difference ΔΦs between the lights IL1 and IL2 is detected, and the phase difference ΔΦr between the first and second reference interference lights ILref1 and ILref2 is detected by the phase detection of the first and second reference interference lights ILref1 and ILref2. Is detected. The phase detector 3B obtains the difference between the phase difference ΔΦs and the phase difference ΔΦr. For example, the phase detector 3B subtracts the phase difference ΔΦr from the phase difference ΔΦs.

  When the measurement unit 2C and the phase detection unit 3B perform such an operation, the stage control unit 52 of the calculation control unit 5 controls the stage 4 so that the measurement object Ob is adjusted to its height. Move in the horizontal direction perpendicular to the direction. For example, the stage control unit 52 of the arithmetic control unit 5 arranges a plurality of measurement points Pn at the measurement location MP along the movement direction, and the interval between two measurement points Pn−1 and Pn adjacent to each other along the movement direction. And the measurement point P3 at one measurement point MPtemp and the measurement point P1 at the measurement point MPnext measured next to the one measurement point MPtemp by scanning (moving), as described above. The stage 4 is moved so that it overlaps.

  Subsequently, when each phase difference ΔΦm of each measurement point MPm is acquired, the shape calculation unit 51 of the calculation control unit 5 obtains the gradient Grm at each measurement point MPm as described above, and each of these according to the scanning order. The surface shape of the measurement object Ob is obtained by connecting the gradient Grm at the measurement location MPm.

  Subsequently, the arithmetic control unit 5 outputs the obtained surface shape of the measurement object Ob to the output unit 7, and the output unit 7 displays the surface shape of the measurement object Ob.

  By operating in this way, the surface shape measuring apparatus SB and the surface shape measuring method mounted on the surface shape measuring device SB according to the present embodiment is a method using an optical heterodyne interferometer. The surface shape of the object Ob can be measured. In the surface shape measuring device SB and the surface shape measuring method having such a configuration, three or more measurement points P on the measurement object Ob, three measurement points at one measurement point MP in the example shown in FIG. When the three reflected lights RL1, RL2, and RL3 reflected by P1, P2, and P3 are subjected to optical heterodyne interference, the reflected light RL2 that is common to each other is used to cause optical interference. First and second interference lights IL1 and IL2 having phase information representing gradient information are obtained. For this reason, for example, the effects of vibrations such as vibration due to vertical movement on the stage 4 on which the measurement object Ob is placed, vibration due to holding fluctuations in the measurement optical system, and vibration of the measurement object Ob itself on the measurement result are offset. It can be almost erased. Therefore, the surface shape measuring apparatus SB and the surface shape measuring method having such a configuration can measure the surface shape of the measuring object Ob with higher accuracy in the order of nm in a relatively short time.

  Moreover, in the surface shape measuring apparatus SB in the above-described embodiment, the measurement light generation unit 1B and the measurement unit 2C constitute an optical heterodyne interferometer, and are obtained by causing optical heterodyne interference using the reflected light RL2 common to each other. Phase detection unit 3B for detecting the phase difference ΔΦs between the first and second interference light beams IL1 and IL2 and the phase detection unit 3B, respectively. And a calculation control unit 5 that calculates the surface shape of the measurement object Ob based on the phase difference ΔΦs between the first and second interference lights IL1 and IL2. For this reason, since the surface shape measuring apparatus SB of this embodiment includes the optical heterodyne interferometer, the surface shape of the measurement object can be measured with higher accuracy.

  In the surface shape measurement apparatus SB in the above-described embodiment, the measurement unit 2C further generates the first and second reference interference lights ILref1 and ILref2 corresponding to the first and second interference lights IL1 and IL2. The phase detector 3B further detects the phase of the first and second reference interference lights ILref1 and ILref2, and detects the phase difference ΔΦr between the first and second reference interference lights ILref1 and ILref2 as a correction value. The phase difference ΔΦs between the phases of the first and second interference lights IL1 and IL2 is corrected with the correction value ΔΦr. Then, the shape calculation unit 51 of the arithmetic control unit 5 obtains the surface shape of the measurement object Ob based on the phase difference (| ΔΦs−ΔΦr |) detected and corrected by the phase detection unit 3B. The phase fluctuation that occurs while the light L emitted from the light source unit 1Ba is guided to the surface of the measurement object Ob greatly affects the measurement result. The surface shape measurement device SB of this embodiment like this The influence of the phase fluctuation on the measurement result can be eliminated, and the surface shape of the measurement object can be measured with higher accuracy.

  Moreover, in the surface shape measuring apparatus SB in the above-described embodiment, the measurement unit 2C includes an optical waveguide type optical element in which optical waveguides having different refractive indexes are formed on the base material 2Cm. For this reason, since the surface shape measuring apparatus SB of this embodiment includes the optical waveguide type optical element and constitutes the measuring unit 2C, it is possible to remove air fluctuation and reduce temperature fluctuation. Interfering light can be obtained more stably. In addition, the surface shape measuring apparatus SB of this embodiment can manufacture an optical path more strictly than the case where a plurality of optical elements are combined, and no optical path adjustment after assembly is required. In addition, downsizing is possible. For this reason, the surface shape measuring apparatus SA in the present embodiment can be portable.

  FIG. 7 is a diagram for explaining an aspect of a plurality of measurement points at one measurement location. FIG. 7A is a diagram for explaining the first mode, FIG. 7B is a diagram for explaining the second mode, and FIG. It is a figure for demonstrating a 3rd aspect.

  In the first and second embodiments described above, the case where there are three measurement points at one measurement point MP has been described. However, the number of measurement points at one measurement point MP is three or more. As long as there is any number, for example, as shown in FIGS. 7A and 7B, there may be five, and for example, as shown in FIG. 7C, nine. It may be.

  In the first mode shown in FIG. 7A, in one measurement point MP, five measurement points P1 to P5 are arranged in a straight line, and such five measurement points P1 to P5 are, for example, diffraction gratings. It can be realized by using. In such a case, for example, reflected light RL1 and RL2 of the measurement points P1 and P2 that are positioned adjacent to each other with the measurement points P1, P2, and P3 as a set and reflection of the measurement points P2, P3 that are positioned adjacent to each other. A pair of the light beams RL2 and RL3 and a set of measurement points P3, P4, and P5, the reflected light beams RL3 and RL4 of the measurement points P3 and P4 that are positioned adjacent to each other and the measurement points P4 and P5 that are positioned adjacent to each other. Optical interference is performed with the reflected lights RL4 and RL5 as a pair. In this way, the reflected light of the measurement point P located at the center is set as a common reflected light, and optical interference occurs between the common reflected light and the reflected light of the measurement point P located on one side adjacent to the measurement point P. In addition, optical interference occurs between the common reflected light and the reflected light of the measurement point P located on the other side adjacent to the measurement point P.

  In the second mode shown in FIG. 7B, in one measurement point MP, the five measurement points P1 to P5 are arranged in a + shape around the measurement point P3 (measurement points P1, P3, which are arranged in a straight line). The measurement points P2, P3, and P4 arranged in a line with P5 are arranged orthogonally), and such five measurement points P1 to P5 are, for example, two diffraction gratings arranged in order with their diffraction directions orthogonal to each other. This can be realized by using. In such a case, for example, the reflection points RL1 and RL3 of the measurement points P1 and P3 that are positioned adjacent to each other as a set of the measurement points P1, P3, and P5 and the reflections of the measurement points P3 and P5 that are positioned adjacent to each other. A pair of light beams RL3 and RL5 and a set of measurement points P2, P3, and P4, and reflected light beams RL2 and RL3 of measurement points P2 and P3 that are positioned adjacent to each other and measurement points P3 and P4 that are positioned adjacent to each other. Optical interference is performed in the same manner as described above with the reflected lights RL3 and RL5 as a pair.

  In the third mode shown in FIG. 7C, in one measurement point MP, nine measurement points P1 to P9 are arranged in a two-dimensional array around the measurement point P5 (measurement points P1 to P3 arranged in a straight line). The measurement points P7 to P9 arranged in a straight line and the measurement points P7 to P9 arranged in a line are arranged in order, and the nine measurement points P1 to P9 are arranged in order with their diffraction directions orthogonal to each other, for example. This can be realized by using two diffraction gratings. In such a case, for example, the reflected light beams RL1 and RL2 of the measurement points P1 and P2 that are positioned adjacent to each other with the measurement points P1 to P3 as a set and the reflected light RL2 of the measurement points P2 and P3 that are positioned adjacent to each other. , RL3 as a pair, and the measurement points P4 to P6 as a set, the reflected lights RL4 and RL5 of the measurement points P4 and P5 that are positioned adjacent to each other and the reflected lights RL5 of the measurement points P5 and P6 that are positioned adjacent to each other. A pair of RL6 and a set of measurement points P7 to P9, the reflected lights RL7 and RL8 of the measurement points P7 and P8 that are positioned adjacent to each other and the reflected lights RL8 and RL9 of the measurement points P8 and P9 that are positioned adjacent to each other. Are paired, and the measurement points P2, P5, and P8 are set as a set, and the reflected lights RL2 and RL5 of the measurement points P2 and P5 that are adjacent to each other are positioned and The same manner as described above the optical interference as a pair is carried out measuring point P5 adjacent to the have, P8 of the reflected light RL5, RL8 respectively.

(Third embodiment)
The surface shape measurement apparatus SB in the second embodiment is an apparatus that generates interference light IL by optical heterodyne interference and measures the surface shape of the measurement object Ob based on the interference light IL. The third embodiment The surface shape measuring device SC in FIG. 1 is a device that generates interference light IL by so-called self-delay optical heterodyne interference and measures the surface shape of the measurement object Ob based on the interference light IL. That is, in the surface shape measuring apparatus SB in the second embodiment, the laser light L emitted from the light source 1Ba is distributed into the first laser light L1 and the second laser light L2, and one of the laser lights (second laser light). By shifting the wavelength (frequency) of L2), a frequency difference Δf is generated between the first laser beam L1 and the second laser beam L2 to cause optical interference, whereas the surface shape measuring device in the third embodiment In the SC, the laser light Ls whose frequency emitted from the light source unit 1Ca is periodically shifted (modulated) is distributed to a plurality of laser lights Ls1, Ls2, Ls3,..., Lsn, and these distributed laser lights Ls1, Ls2 are distributed. , Ls3,..., Lsn are guided by waveguide portions having different optical path lengths, thereby causing a predetermined frequency difference Δfs between the laser beams Ls to cause optical interference.

  FIG. 8 is a diagram showing the configuration of the surface shape measuring apparatus SC in the third embodiment. FIG. 9 is a diagram showing a configuration of the measurement unit 2D in the surface shape measurement apparatus SC shown in FIG.

  The surface shape measuring device SC of the third embodiment is a device that measures a surface shape that is a change in the height direction (thickness direction) of the measurement object Ob. For example, as shown in FIG. Unit 1C, measurement unit 2D, phase detection unit 3C, stage (mounting table) 4, calculation control unit 5, input unit 6 and output unit 7, and is configured to be measured by stage 4 The surface of the measurement object Ob is scanned by moving Ob in the horizontal direction, and the surface shape of the measurement object Ob over a predetermined range is measured.

  The measurement light generation unit 1C is a device that generates measurement light ML that is predetermined coherent light and measures the surface shape of the measurement object Ob by the optical heterodyne interferometry. The measurement light ML is light (see FIG. 10B) whose frequency is periodically shifted, and is polarized light having a predetermined polarization plane set in advance. For example, as shown in FIG. 8, the measurement light generation unit 1C includes a light source unit 1Ca, an optical isolator 1Cb, a polarizer 1Cc, and an output terminal 1Cd.

  The light source unit 1Ca is a device that emits light Ls, and includes, for example, a semiconductor laser. In this semiconductor laser, the oscillation frequency slightly depends on the injection current, and has a linearity in the local portion. A power source for injection current (not shown) is connected to the light source unit 1Ca. In the light source unit 1Ca of the present embodiment, the oscillation frequency is modulated such that the time change of the oscillation frequency becomes a saw blade in the graph by controlling the power supply for the injection current (FIG. 10A and FIG. B)). At this time, a region (modulation amplitude Δi [A]) in which the oscillation frequency is linearly dependent on the injection current in the semiconductor laser is used, and the change rate of the oscillation frequency with respect to the injection current of the semiconductor laser in this region is β [Hz / A]. And the modulation frequency is fm [Hz]. The optical isolator 1Cb is an optical component similar to the optical isolator 1Ab of the first embodiment. The polarizer 1Cc is an optical component similar to the polarizer 1Ac of the first embodiment. The output terminal 1Cd is a terminal for emitting light from the optical component. For example, the output terminal 1Cd is a connector for connecting an optical fiber similar to the output terminal 1Ad of the first embodiment.

  The light source unit 1Ca, the optical isolator 1Cb, the polarizer 1Cc, and the output terminal 1Cd are arranged in this order according to the propagation direction of light with their optical axes aligned with each other.

  In such a measurement light generation unit 1C, the frequency is periodically shifted from the semiconductor laser of the light source unit 1Ca (the time change of the oscillation frequency becomes a saw blade in the graph (see FIG. 10B)). The laser light Ls is incident on the polarizer 1Cc via the optical isolator 1Cb and becomes measurement light MLs of laser light (s-polarized laser light or p-polarized laser light) having a predetermined polarization plane, and is output terminal 1Cd. Is injected from. The measurement light MLs is incident on the measurement unit 2D.

  An optical fiber is used for the connection between the measurement light generation unit 1C and the measurement unit 2D, similarly to the connection between the measurement light generation unit 1A and the measurement unit 2A in the first embodiment.

  The measurement unit 2D is an apparatus that receives the measurement light MLs from the measurement light generation unit 1C and obtains an optical signal including information on the surface shape of the measurement object Ob by self-delay optical heterodyne interferometry using the measurement light MLs. is there. Such a measurement unit 2D has three or more measurement objects on the surface of the measurement object Ob in the measurement by irradiation of one measurement light MLs (MLs1, MLs2, MLs3,..., MLsn) with respect to one measurement point MP. Measurement light from the measurement light generator 1C to irradiate the measurement light ML (MLs1, MLs2, MLs3,..., MLsn) to the plurality of measurement points P (P1, P2, P3,..., Pn), respectively. A light splitting unit that divides MLs into three or more measurement lights MLs1, MLs2, MLs3,..., MLsn, and a plurality of measurement lights MLs1, MLs2, MLs3,. Three or more light guides that respectively guide the MLsn and irradiate a plurality of measurement points P1, P2, P3,..., Pn on the measurement object Ob with measurement light, and a measurement object A pair of reflected light RLs in a plurality of reflected lights RLs (RLs1, RLs2, RLs3,..., RLsn) reflected at a plurality of measurement points P1, P2, P3,. A plurality of optical interference units, and at least one set of the optical interference units in the plurality of optical interference units is configured to cause optical interference using the reflected light RLs common to each other. Further, one set of light guides for obtaining each reflected light RLs to be interfered in the one set of light interference units is common to the one set of light interference units among the one set of light guide units. Reflections other than the reflected light RLs common to each other in the specific light guide unit that irradiates the measurement light MLs to the measurement point P where the reflected light RLs is obtained and the one set of light interference units of the one set of light guide units Each of the optical path lengths Δd between at least two other light guides that irradiate the measurement light MLs to the measurement point P where the light RLs is obtained has an optical path length that becomes a predetermined optical path difference.

  More specifically, for example, as shown in FIG. 9, the measurement unit 2D includes an input terminal 2Da, an input-side waveguide 2Db, an objective lens 2Dc, a half mirror 2Dd, a condensing lens 2De, and an output-side waveguide. 2Df and an output terminal 2Dg, and these input-side waveguide 2Db and output-side waveguide 2Df are provided by forming an optical waveguide having a refractive index different from that of the substrate 2Dh on the substrate 2Dh. Yes.

  The base material 2Dh is a plate-like member (substrate) formed from a material having a predetermined refractive index, and the input terminal 2Da and the output terminal 2Dg are arranged at predetermined positions on the outer peripheral surface. In the example shown in FIG. 9, the base material 2Dh has a substantially rectangular parallelepiped shape, and the input terminal 2Da and the output terminal 2Dg are disposed on the upper surface thereof. As described above, the optical fiber extending from the measurement light generator 1C is connected to the input terminal 2Da.

  The base material 2Dh has an input-side waveguide 2Db extending from the position where the input terminal 2Da in the base material 2Dh is disposed only slightly (for example, 0.3 mm) than the predetermined refractive index in the base material 2Dh. It is formed by increasing (about 3%). The input side waveguide 2Db branches the measurement light MLs from the measurement light generation unit 1C incident from one end thereof via the input terminal 2Da and guides it to the objective lens 2Dc disposed at the other end. .

  Specifically, the input-side waveguide 2Db includes optical branching portions 2Db-1, 2Db-2 and waveguide portions 2Db-3, 2Db-4, 2Db-5.

  The optical branching units 2Db-1 and 2Db-2 receive the measurement light MLs from the measurement light generation unit 1C that has entered the input-side waveguide 2Db via the input terminal 2Da into a plurality of measurement light MLs (in the example shown in FIG. 9). , MLs1, MLs2, and MLs3), and the distributed plurality of measurement lights MLs1, MLs2, and MLs3 are respectively incident on the plurality of waveguide portions 2Db-3, 2Db-4, and 2Db-5. In the example illustrated in FIG. 9, the two light branching units 2Db-1 and 2Db-2 branch the measurement light MLs into three measurement lights MLs1, MLs2, and MLs3, and the three measurement lights MLs1, MLs2, and MLs3 are respectively 3 It is made to enter into two waveguide part 2Db-3, 2Db-4, and 2Db-5. Each of the waveguide sections 2Db-3, 2Db-4, and 2Db-5 cooperates with the input-side waveguide section 2Db on the upstream side of each of the optical branch sections 2Db-1 and 2Db-2. 2Db-13, 2Db-14, 2Db-15. Each of the input-side waveguide portions 2Db-13, 2Db-14, and 2Db-15 has a predetermined optical path difference Δd between the pair of input-side waveguide portions that irradiate the measurement light MLs to the adjacent measurement points Pn and Pn + 1. Each has an optical path length. In each of the input-side waveguide portions 2Db-13, 2Db-14, and 2Db-15 of the present embodiment, the measurement is located at one end of the measurement points P1, P2, P3,..., Pn arranged in a line on the surface of the measurement object Ob. The optical path length from the input-side waveguide section 2Db-13 that guides the measurement light MLs1 toward the point P1 toward the input-side waveguide section that irradiates the measurement light MLs to the measurement point Pn that is positioned on the other end side of the row. Are getting longer. As described above, since the optical path lengths of the plurality of input-side waveguide portions are sequentially increased, the gradient between the measurement points Pn and Pn + 1 aligned in the column direction can be measured at a time. It is possible to measure the surface shape of the measuring object Ob along the direction in which the points P1, P2, P3,. In the example shown in FIG. 9, the method of the input side waveguide section 2Db-14 that guides the measurement light MLs2 is longer than the input side waveguide section 2Db-13 that guides the measurement light MLs1, and the optical path length is longer by Δd. The method of the input side waveguide section 2Db-15 that guides the measurement light MLs3 is configured so that the optical path length is longer by Δd than the input side waveguide section 2Db-14 that guides the light MLs2. That is, the incident-side waveguide portions 2Db-13 and 2Db-14 that guide the measurement lights MLs1 and MLs2 irradiated to the adjacent measurement points P1 and P2 are the incident-side waveguide portions 2Db-13 and 2Db-14. The incident-side waveguide section 2Db-14 that guides the measurement lights MLs2 and MLs3 irradiated to the measurement points P2 and P3 that are adjacent to each other and have optical path lengths such that the optical path difference between them is a predetermined optical path difference Δd. 2Db-15 has an optical path length at which the optical path difference between the incident-side waveguide sections 2Db-14 and 2Db-15 becomes the predetermined optical path difference Δd. Specifically, each of the input-side waveguide portions 2Db-13, 2Db-14, and 2Db-15 is disposed along a common surface (paper surface in FIG. 9) in the base material 2Dh. The input-side waveguide 2Db-14 has an optical path length longer by Δd than the input-side waveguide 2Db-13 by forming the optical path redundant portion DV-1 extending so as to curve along the common plane. Thus, the input side waveguide 2Db-15 is formed by forming the optical path redundant portion DV-2 extending so as to be curved more greatly than the optical path redundant portion DV-1 along the common plane. The optical path length is longer than Δ-14 by Δd.

  The optical path difference between the input side waveguide sections 2Db-13 and 2Db-14 and between the input side waveguide sections 2Db-14 and 2Db-15 is reflected by the adjacent measurement points P1, P2 or P2, P3. Frequency provided between the pair of reflected light RLs1, RLs2 or RLs2, RLs3 and the corresponding measurement light MLs1, MLs2, or MLs2, MLs3 to cause the light RLs1, RLs2 or RLs2, RLs3 to interfere with each other in the output-side waveguide 2Df This is based on the difference Δfs. Specifically, the optical path difference Δd is defined by the following equation (1).

Δfs = α · (Δd / C) = β · Δi · fm · (Δd / C) [Hz] (1)

Here, C is the traveling speed of the measuring light ML, Δi in a region where the semiconductor laser is linearly dependent is modulation amplitude (see FIG. 10A), and β is a change in oscillation frequency with respect to the injection current Δi of the semiconductor laser. (See FIG. 10B), α is the rate of change of the measured optical frequency per time,
α = β · Δi · fm [Hz / sec] (2)
It is a value that satisfies Further, the frequency difference Δfs of the measurement light MLs is set to a value that is easy to handle by calculation in the phase detection unit 3C and the calculation control unit 5 described later.

  By providing such an optical path difference Δd between the pair of input side waveguide portions 2Db-13, 2Db-14, or 2Db-14, 2Db-15, each incident side waveguide portion 2Db-13, 2Db-14. 2Db-15 guided measurement light MLs1, MLs2, or between MLs2 and MLs3, a slight frequency difference Δfs is generated (for example, see FIG. 11), and reflected by the measurement point MP of the measurement object Ob. The reflected light RLs1 and RLs2 or the RLs2 and RLs3 that have been reflected can be subjected to light heterodyne interference (self-delayed light heterodyne interference).

  Each of the input-side waveguide portions 2Db-13, 2Db-14, 2Db-15 is directed to the measurement light MLs1 toward the measurement point P1 positioned at one end of the measurement points P1, P2, P3,. A structure in which the optical path length is sequentially increased from the input-side waveguide portion 2Db-13 that guides the measurement light toward the input-side waveguide portion that guides the measurement light MLs toward the measurement point Pn that is located on the other end side of the row. It is not limited to. For example, each input-side waveguide section is based on the optical path length of the specific input-side waveguide section and the optical path lengths of the other input-side waveguide sections other than this. The optical path difference may be the frequency difference Δfs described above. In the example shown in FIG. 12, the measurement unit 2E includes three input-side waveguide portions 2Eb-13, 2Eb-14, and 2Eb-15, and the second (center) input-side waveguide portion (specific input-side waveguide) is provided. By providing the optical path redundant part EV in the waveguide part 2Eb-14, a pair of input side waveguide parts 2Eb-13, 2Eb-14, or 2Eb for guiding the measurement light MLs toward the adjacent measurement points Pn and Pn + 1 A predetermined optical path difference Δd is generated between −14 and 2Eb−15. With this configuration, the optical path difference Δd between the input-side waveguide portions 2Eb-13 and 2Eb-14 that irradiate the measurement light MLs1 and MLs2 to the measurement point P1 and the measurement point P2, and the measurement point P2 and the measurement point The optical path difference Δd between the input-side waveguide portions 2Eb-14 and 2Eb-15 that irradiate the measurement light MLs2 and MLs3 to P3 can be easily and reliably matched, and thereby the surface shape of the measurement object Ob Can be measured with higher accuracy.

  In addition, each input-side waveguide section measures from a light guide section that guides measurement light toward a measurement point located at one end of the measurement points arranged in a row toward a measurement point located at the other end of the row. The optical path lengths of the odd-numbered (or even-numbered) input-side waveguides may be the same toward the input-side waveguide that guides light. In the example shown in FIG. 7 (A), the input side waveguide portion that guides the measurement lights MLs1, MLs2, and MLs3 irradiated to the measurement points P1, P2, and P3 is set as one set, and the measurement points P3, P4, and P5 are irradiated. The input-side waveguide section that guides the measurement light MLs3, MLs4, and MLs5 to be measured is another set. Then, the optical path length of the input side waveguide part (specific input side waveguide part) that guides the measurement light MLs2 of the set of input side waveguide parts, and the input side guide that guides the measurement lights MLs1 and MLs3. The optical path difference with the optical path length of the waveguide section (other input side waveguide section) is set to the above-described optical path difference Δd, and the measurement light MLs4 of the other set of input side waveguide sections is guided. The optical path length between the optical path length of the input-side waveguide section that emits light (specific input-side waveguide section) and the optical path length of the input-side waveguide section that guides the measurement light MLs3 and MLs5 (other input-side waveguide sections) You may comprise so that a difference may become said optical path difference (DELTA) d, respectively.

  In this case, the number of the measurement points P is further increased, and the optical path lengths of the input-side waveguide portions that guide the measurement light MLs (2n + 1) irradiated to the odd-numbered measurement points P (2n + 1) are all set to the same first optical path length. For example, the optical path length of the input-side waveguide section that guides the measurement light MLs (2 (n + 1)) irradiated to the even-numbered measurement points P (2 (n + 1)) excluding the specific even-numbered measurement point P6 is If the second optical path length is different from the first optical path length, and only the optical path length of the input-side waveguide portion that irradiates the measurement light MLs6 to the measurement point P6 is the third optical path length different from the first optical path length and the second optical path length, Optical path difference between the input-side waveguide part that guides the measurement light MLs6 irradiated to the measurement point P6 and the input-side waveguide part that guides the measurement light MLs5 and MLs7 irradiated to the adjacent measurement points P5 and P7 Measurement to irradiate Δd1 to other adjacent measurement points Pn and Pn + 1 MLSN, may be different values for each of the optical path difference Δd2 between the input waveguide portion for guiding the MLSN + 1. That is, in the surface shape measuring apparatus having such a configuration, it is possible to change the frequency difference between the light beams that cause light heterodyne interference in the direction in which the measurement points P of the measurement object Ob are arranged.

  Further, in the example shown in FIG. 7B, a set of input side waveguide portions that guide the measurement lights MLs1, MLs2, MLs3, MLs4, and MLs5 irradiated to the measurement points P1, P2, P3, P4, and P5 are set as one set. , The optical path length of the input side waveguide section (specific input side waveguide section) that guides the measurement light MLs3, and the input side waveguide section (other input side) that guides the measurement lights MLs1, MLs2, MLs4, and MLs5 You may comprise so that the optical path difference with the optical path length of a waveguide part) may become said optical path difference (DELTA) d, respectively. In this way, the measurement lights MLs1, MLs2, MLs4, and MLs5 from the other input-side waveguide parts so as to surround the measurement point P3 irradiated with the measurement light MLs3 from the specific input-side waveguide part. , The gradient between the central measurement point P3 and each of the measurement points P1, P2, P4, P5 surrounding the measurement point P3 can be measured at a time. It is possible to measure a surface shape in a predetermined range in the surface direction of Ob at a time.

  The objective lens 2Dc has a number of lenses corresponding to the number of the plurality of measurement lights MLs1, MLs2, and MLs3 so as to give a lens action to each of the plurality of measurement lights MLs1, MLs2, and MLs3 guided by the input-side waveguide 2Db. The half mirror 2Dd is disposed on the exit side. In the example shown in FIG. 9, the objective lens 2Dc is intended to give a lens action to each of the measurement lights MLs1, MLs2, and MLs3 emitted from the three waveguide portions 2Db-3 to 2Db-5 in the input-side waveguide 2Db. It is configured with three lenses. Each lens of the objective lens 2Dc collects the measurement lights MLs1, MLs2, and MLs3 emitted from the three waveguide portions 2Db-3 to 2Db-5 in the input-side waveguide 2Db, and collects the measurement lights. MLs1, MLs2, and MLs3 are made incident on the half mirror 2Dd.

  The half mirror 2Dd is an optical component that divides incident light into two lights in terms of optical power and emits them respectively. One of the distributed lights passes through the half mirror 2Dd and is emitted in the same direction. The other distributed light is reflected by the half mirror 2Dd and emitted in a direction perpendicular to the direction (a direction perpendicular to the direction).

  The input-side waveguide 2Db and the objective lens 2Dc are arranged so that their optical axes coincide with each other, and the half mirror 2Dd is arranged so that the mirror surface intersects the optical axis at an angle of 45 degrees. Yes.

  In the input terminal 2Da, the input side waveguide 2Db, the objective lens 2Dc, and the half mirror 2Dd configured as described above, the measurement light MLs from the measurement light generation unit 1C is incident on the input side waveguide 2Db via the input terminal 2Da. One measurement light MLs3 distributed in the optical branching section 2Db-1 propagates in the waveguide section 2Db-5, is guided by the waveguide section 2Db-5, and enters the corresponding lens of the objective lens 2Dc. The The other measurement light MLs distributed by the optical branching unit 2Db-1 is distributed by the optical branching unit 2Db-2, and the one measurement light MLs2 propagates in the waveguide unit 2Db-4, and the waveguide The light is guided by the portion 2Db-4 and is incident on the corresponding lens of the objective lens 2Dc. The other measurement light MLs1 distributed by the optical branching section 2Db-2 propagates through the waveguide section 2Db-3, is guided by the waveguide section 2Db-3, and is applied to the corresponding lens of the objective lens 2Dc. Incident.

  At this time, since the optical path lengths of the waveguide portions 2Db-3 to 2Db-5 are different from each other, there is a predetermined frequency difference Δfs between the measurement lights MLs1 and MLs2 or MLs2 and MLs3 incident on the objective lens 2Dc. Has occurred.

  Three parallel measurement lights MLs1, MLs2, and MLs3 that have passed through the half mirror 2Dd and exited in the same direction are incident on the condenser lens 2De.

  Then, the three parallel measurement lights MLs1, MLs2, and MLs3 reflected by the half mirror 2Dd and emitted from the half mirror 2Dd are emitted from the measurement unit 2D, and are measured at one measurement location MP on the surface of the measurement object Ob. The points P1, P2, and P3 are respectively irradiated and reflected. Three reflected lights (regular reflection components of reflected light) RLs (RLs1, RLs2, RLs3) reflected at three measurement points P1, P2, and P3 on the surface of the measurement object Ob are incident on the measurement unit 2D. , And enters the condenser lens 2De via the half mirror 2Dd. The reflected light RLs1 is light reflected by the measurement light MLs1 at the measurement point P1. The reflected light RLs2 is light reflected by the measurement light MLs2 at the measurement point P2. The reflected light RLs3 is light that is reflected by the measurement light MLs3 at the measurement point P3.

  The condensing lens 2De is the same as the condensing lens 2Af and the condensing lens 2Be in the first embodiment, and its optical axis is orthogonal to the optical axes of the input-side waveguide 2Db and the objective lens 2Dc, and The mirror surface of the half mirror 2Dd is arranged so as to intersect at an angle of −45 degrees (135 degrees). The condenser lens 2De has the number of reflected lights RLs (RLs1, RLs2, RLs3) so as to give a lens action to each of the plurality of reflected lights RLs (three reflected lights RLs1, RLs2, RLs3 in the example shown in FIG. 9). A corresponding number of lenses (three lenses in this example) are provided, and on the exit side, the output-side waveguide 2Df is slightly smaller than the predetermined refractive index of the base material 2Dh (for example, 0. 0). It is formed by enlarging (about 3 to 3%).

  The output-side waveguide 2Df is the same as the output-side waveguide 2Ag and the output-side waveguide 2Bf in the first embodiment, and each reflected light RLs incident from the condenser lens 2De (RLs1, RLs2, RLs3) are guided respectively, a pair of reflected lights RLs in the plurality of reflected lights RLs are caused to interfere with each other, and a plurality of interference lights ILs are guided. Here, in the present embodiment, at least one set of the interference light ILs among the plurality of interference lights ILs is generated by causing optical interference using the common reflected light RLs. More specifically, the output-side waveguide 2Df is the same as the output-side waveguide 2Ag and the output-side waveguide 2Bf in the first embodiment, and the three waveguide portions 2Df-1, 2Df-2, 2Df-3. And one branch portion 2Df-4, two junction portions 2Df-5, 2Df-6, and two waveguide portions 2Df-7, 2Df-8.

  In the example shown in FIG. 9, the half mirror 2Dd, the condensing lens 2De, the output side waveguide 2Df, and the output terminal 2Dg having such a configuration are reflected at three measurement points P1, P2, and P3 on the surface of the measurement object Ob, respectively. The three reflected lights (regular reflection components of the reflected light) RLs (RLs1, RLs2, RLs3) are incident on the measurement unit 2D and are incident on the respective lenses of the condenser lens 2De via the half mirror 2Dd. The respective lenses of the condenser lens 2De cause the reflected lights RLs1, RLs2, and RLs3 to enter the three waveguide portions 2Df-1, 2Df-2, and 2Df-3 in the output-side waveguide 2Df, respectively. That is, each lens of the condenser lens 2De is for waveguide coupling with respect to the three waveguide portions 2Df-1, 2Df-2, and 2Df-3 in the output-side waveguide 2Df. The reflected light RLs2 incident on the central waveguide section 2Df-2 propagates through the waveguide section 2Df-2, is guided by the waveguide section 2Df-2, and is distributed by the branch section 2Df-4. One reflected light RLs2 (RLs2-1) distributed by the branching section 2Df-4 is guided to the joining section 2Df-5, and the other reflected light RLs2 (RLs2-2) is sent to the joining section 2Df-6. Light is guided. Further, the reflected light RLs1 incident on the waveguide section 2Df-1 propagates through the waveguide section 2Df-1, is guided by the waveguide section 2Df-1, and is guided to the junction section 2Df-5. The reflected light RLs3 incident on the waveguide section 2Df-3 propagates through the waveguide section 2Df-3, is guided by the waveguide section 2Df-3, and is guided to the junction section 2Df-6. In the merging unit 2Df-5, the reflected light RLs2 and the reflected light RL1 guided as described above are combined, and optical heterodyne interference is performed to generate the first interference light ILs1 (= RLs1 + RLs2). The first interference light ILs1 is guided from the merging portion 2Df-5 to the waveguide portion 2Df-7, propagates through the waveguide portion 2Df-7, is guided by the waveguide portion 2Df-7, and is output to the output terminal 2Dg. Is incident on. Then, in the junction 2Df-6, the reflected light RLs2 and the reflected light RLs3 guided as described above are combined and optical heterodyne interference is performed to generate the second interference light ILs2 (= RLs2 + RLs3). The second interference light ILs2 is guided from the merging portion 2Df-6 to the waveguide portion 2Df-8, propagates through the waveguide portion 2Df-8, is guided by the waveguide portion 2Df-8, and is output to the output terminal 2Dg. Is incident on. The first and second interference lights ILs1 and ILs2 are optical signals including information on the surface shape of the measurement object Ob. The first and second interference lights ILs1 and ILs2 are incident on the phase detection unit 3C from the measurement unit 2D via the output terminal 2Dg.

  Returning to FIG. 8, as in the first embodiment, the measurement unit 2D and the phase detection unit 3C may be single-mode optical fibers, but from the viewpoint of superiority in optical axis adjustment and the amount of propagating light. Connected by multimode optical fiber. That is, in the present embodiment, the plurality of interference lights ILs emitted from the measurement unit 2D, and in the examples illustrated in FIGS. 8 and 9, the first and second interference lights ILs1 and ILs2 are guided by the multimode optical fiber, The light enters the phase detector 3C.

  The phase detection unit 3C performs phase detection on the plurality of interference lights ILs emitted from the measurement unit 2D, and phase difference ΔΦ between a set of interference lights obtained by optical heterodyne interference using the reflected light RLs common to each other. Is detected. Then, the phase detection unit 3C outputs the detected phase difference ΔΦ to the calculation control unit 5. More specifically, as shown in FIG. 8, the phase detector 3C includes a photoelectric conversion unit 3Ca (3Ca1, 3Ca2) for interference light and a phase detector 3Cb for interference signal. .

  The photoelectric conversion unit 3Ca includes, for example, a photoelectric conversion element that converts an electric signal having a signal level corresponding to the amount of incident light and outputs the electric signal, such as a photodiode. The photoelectric conversion unit 3Ca is prepared according to the number of the interference light ILs obtained by the measurement unit 2D, receives each of the plurality of interference light ILs from the measurement unit 2D, and each electric signal having a signal level corresponding to each light amount. A signal is output as each interference signal Sig. In the present embodiment, since the interference light ILs is two, two photoelectric conversion units 3Ca1 and 3Ca2 are prepared. Each of the photoelectric conversion units 3Ca1 and 3Ca2 receives two first and second interference lights ILs1 and ILs2 emitted from the output terminal 2Dg of the measurement unit 2D via each multimode optical fiber and each input terminal (not shown). The first and second interference signals Sig1 and Sig2 are respectively output to the phase detector 3Cb in accordance with the respective light amounts of the interference lights ILs1 and ILs2.

  The phase detector 3Cb receives a plurality of interference signals Sig from the photoelectric conversion unit 3Ca and relates to a set of interference lights ILs obtained by optical heterodyne interference using the reflected light RLs common to each other. It is a device for detecting the phase difference ΔΦs between the two. In the example illustrated in FIG. 8, the phase detector 3Cb receives the first and second interference signals Sig1 and Sig2 from the photoelectric conversion units 3Ca1 and 3Ca2, and is between the first interference signal Sig1 and the second interference signal Sig2. The phase difference ΔΦs is detected. Then, the phase detector 3Cb outputs the detected phase difference ΔΦs to the calculation unit control unit 5.

  The stage 4, the calculation control unit 5, the input unit 6 and the output unit 7 are the same as the stage 4, the calculation control unit 5, the input unit 6 and the output unit 7 in the surface shape measuring apparatus SA of the first embodiment, respectively. Since there is, explanation is omitted.

  Next, the operation of the surface shape measuring apparatus SC in the present embodiment will be described. In the following description, for the sake of convenience of explanation, a case where there are three measurement points Pn at each measurement location MP will be described by taking the case shown in FIG. 8 as an example.

  When a power switch (not shown) is turned on, the surface shape measuring device SC is activated and necessary parts are initialized by the arithmetic control unit 5. Then, for example, when a measurement object Ob of a plate-like body such as a semiconductor wafer is placed on the stage 4 and receives a command for instructing measurement start from the input unit 6, the arithmetic control unit 5 reads the surface shape of the measurement object Ob. Start measuring.

  At this time, the light source control unit 53 of the arithmetic control unit 5 drives the measurement light generation unit 1C to cause the semiconductor laser light source 1Ca to emit laser light whose frequency is periodically shifted. By the emission of a predetermined laser beam from the semiconductor laser light source 1Ca, the measurement light MLs is emitted from the output terminal 1Cd of the measurement light generation unit 1C by the action of the optical system described above.

  Subsequently, the measurement light MLs emitted from the output terminal 1Cd of the measurement light generation unit 1C propagates through the optical fiber and enters the measurement unit 2D. In the measurement unit 2D, in the input-side waveguide 2Db, the incident measurement light MLs is branched into a plurality of measurement lights MLs1, MLs2, and MLs3 by the optical branching units 2Db-1 and 2Db-2, and each of the branched measurements. Lights MLs1, MLs2, and MLs3 are propagated through waveguide portions 2Db-3, 2Db-4, and 2Db-5 having different optical path lengths, respectively, and are propagated to the objective lens 2Dc by the waveguide portions 2Db-3, 2Db-4, and 2Db-5. Incident light is applied to each of the measurement points P1, P2, and P3. The first and second interference lights ILs1 and ILs2 are generated from the measurement lights MLs1, MLs2, and MLs3 by the above-described operation of the optical system, and the first and second interference lights ILs1 and ILs2 are emitted from the output terminal 2Dg. . Subsequently, the first and second interference lights ILs1 and ILs2 emitted from the output terminal 2Dg of the measurement unit 2D propagate through the multimode optical fiber and enter the phase detection unit 3C. In this phase detection unit 3C, the first and second interference lights ILs1 and ILs2 are detected by the phase detection of the first and second interference lights ILs1 and ILs2 with respect to the set obtained by the self-delay optical heterodyne interference using the reflected light RLs2 common to each other. A phase difference ΔΦs between the second interference lights ILs1 and ILs2 is detected.

  When the measurement unit 2D and the phase detection unit 3C perform such an operation, the stage control unit 52 of the calculation control unit 5 controls the stage 4 to adjust the height of the measurement object Ob. Move in the horizontal direction perpendicular to the direction. For example, the stage control unit 52 of the arithmetic control unit 5 includes a plurality of measurement points Pn at the measurement location MP arranged in a line along the movement direction, and two measurement points Pn−1 and Pn adjacent to each other along the movement direction. , And as described above, the measurement point P3 at one measurement location MPtemp and the measurement point P1 at the measurement location MPnext measured next to this one measurement location MPtemp by scanning (moving). The stage 4 is moved so that and overlap.

  Subsequently, when each phase difference ΔΦm of each measurement point MPm is acquired, the shape calculation unit 51 of the calculation control unit 5 obtains the gradient Grm at each measurement point MPm as described above, and each of these according to the scanning order. The surface shape of the measurement object Ob is obtained by connecting the gradient Grm at the measurement location MPm.

  Subsequently, the arithmetic control unit 5 outputs the obtained surface shape of the measurement object Ob to the output unit 7, and the output unit 7 displays the surface shape of the measurement object Ob.

  By operating in this way, the surface shape measuring apparatus SC and the surface shape measuring method mounted on the surface shape measuring device SC according to the present embodiment are methods using an optical interferometer using the optical heterodyne method. The surface shape of the measurement object Ob can be measured in the order of nm. In the surface shape measuring apparatus SC and the surface shape measuring method having such a configuration, a plurality of reflected lights RLs1 reflected at three or more measurement points P1, P2, P3,. When RLs2 and RLs3 are optically interfered with each other, there is a case where optical interference is performed using the reflected light RLs2 common to each other, so that interference light having phase information representing gradient information on the surface of the measurement object Ob can be obtained. For this reason, for example, the influence of vibrations such as vibration due to vertical movement on the stage 4 on which the measurement object Ob is placed, vibration due to holding fluctuations in the measurement optical system, and vibration of the measurement object itself on the measurement result is substantially canceled out. Can be erased. Therefore, the surface shape measuring apparatus SC and the surface shape measuring method having such a configuration can measure the surface shape of the measurement object Ob with higher accuracy in the order of nm in a relatively short time.

  In addition, the measurement light MLs whose frequency changes periodically is divided into a plurality of measurement lights MLs1, MLs2, MLs3,..., MLsn, and an optical path difference Δd is provided between the measurement lights MLs to provide a plurality of measurement points P1, P2, P3. ,..., Pn is used to generate a frequency difference Δfs between the measurement lights MLs at the time of irradiation, and so-called self-delay type optical heterodyne interference method is used in which the reflected lights RLs interfere with each other. It is possible to reduce the size of the light source unit 1Ca and improve the degree of freedom in selecting the light source unit 1Ca. That is, a normal optical heterodyne interference system as in the second embodiment (light having a constant frequency is divided into two measurement lights, and one measurement light is frequency-modulated to provide a slight frequency difference between the two measurement lights. Method), for example, a laser oscillator having a very stable oscillation frequency, such as a gas laser, and a light modulation element must be used as the light source. Therefore, the degree of freedom in selecting the light source is small and downsizing is difficult. In the so-called self-delayed optical heterodyne interference system as in the invention, for example, a semiconductor laser or the like can be used, so that the light source unit 1Ca can be reduced in size, stability, and light source lifetime can be improved. It becomes.

(Fourth embodiment)
Similar to the surface shape measuring device SC in the third embodiment, the surface shape measuring device SD in the fourth embodiment generates the interference light IL by self-delay type optical heterodyne interference, and the measurement object is based on the interference light IL. Although this is a device that measures the surface shape of Ob, it is a device that further improves measurement accuracy by mixing a part of the measurement light MLs emitted from the light source as interference light with interference light.

  FIG. 13 is a diagram showing a configuration of a surface shape measuring apparatus SD in the fourth embodiment. FIG. 14 is a diagram showing a configuration of a measurement unit 2D in the surface shape measurement apparatus SD shown in FIG.

  The surface shape measuring device SD of the fourth embodiment is a device that measures a surface shape that is a change in the height direction (thickness direction) of the measurement object Ob. For example, as shown in FIG. Unit 1D, measurement unit 2F, phase detection unit 3D, stage (mounting table) 4, calculation control unit 5, input unit 6 and output unit 7, and is configured to be measured by stage 4 The surface of the measurement object Ob is scanned by moving Ob in the horizontal direction, and the surface shape of the measurement object Ob over a predetermined range is measured.

  Similar to the measurement light generation unit 1C of the third embodiment, the measurement light generation unit 1D includes a light source unit 1Da, an optical isolator 1Db, a polarizer 1Dc, and an output terminal 1Dd. The light source unit 1Da is a component that emits light whose frequency is periodically shifted, similar to the light source unit 1Ca of the third embodiment. The optical isolator 1Db is an optical component similar to the optical isolator 1Cb of the third embodiment. The polarizer 1Dc is an optical component similar to the polarizer 1Cc of the third embodiment. The output terminal 1Dd is a connector for connecting an optical fiber, similar to the output terminal 1Cd of the third embodiment.

  An optical fiber is used for the connection between the measurement light generation unit 1D and the measurement unit 2F, as in the connection between the measurement light generation unit 1C and the measurement unit 2D in the third embodiment. A reference light branching section Cref is provided on the upstream side of the connection portion of the optical fiber with the measuring section 2F. The reference light branching unit Cref branches a part of the measurement light MLs1 incident on the measurement unit 2F by the optical fiber as the reference light, and enters the phase detection unit 3D through the multimode optical fiber. A fused fiber optical fiber type optical branching coupler is used for the reference light branching section Cref of the present embodiment. In the example shown in FIG. 14, the reference light branching section Cref is provided with an optical fiber branching section Cref-1 that divides the optical fiber into two by a molten fiber at the exit end portion of the optical fiber that guides the measurement light MLs. Two optical fibers Cref-2 and Cref-3 are connected to the optical fiber branching section Cref-1. The other end of the one optical fiber Cref-2 is connected to the measurement unit 2F, and the other end of the other optical fiber Cref-3 is connected to the phase detection unit 3D. The optical fiber branching section Cref-1 may be, for example, an optical fiber type optical branching coupler connected to the exit end portion of the optical fiber that guides the measurement light MLs. The exit end portion of the optical fiber to be guided may be processed into an optical fiber type optical branching coupler.

  The measurement unit 2F is an optical component similar to the measurement unit 2D of the third embodiment. In the example shown in FIG. 14, the measurement unit 2F includes an input terminal 2Fa, an input side waveguide 2Fb, an objective lens 2Fc, a half mirror 2Fd, a condensing lens 2Fe, an output side waveguide 2Ff, and an output terminal 2Fg. The input side waveguide 2Fb and the output side waveguide 2Ff are provided by forming an optical waveguide having a refractive index different from that of the base material 2Fh on the base material 2Fh.

  The input-side waveguide 2Fb includes input-side waveguide portions 2Fb-13, 2Fb-14, which are optical waveguides similar to the input-side waveguide portions 2Db-13, 2Db-14, and 2Db-15 of the third embodiment. 2Fb-15 is configured. Further, each of the input-side waveguide sections 2Fb-13, 2Fb-14, and 2Fb-15 is similar to each of the waveguide sections in the same manner as the input-side waveguide sections 2Db-13, 2Db-14, and 2Db-15 of the third embodiment. 2Fb-3, 2Fb-4, 2Fb-5, and a portion of the input side waveguide 2Fb on the upstream side of each of the waveguide portions 2Fb-3, 2Fb-4, and 2Fb-5.

  The output-side waveguide 2Ff is the same as the output-side waveguide 2Df in the third embodiment, and each reflected light RLs incident from the condenser lens 2Fe (RLs1, RLs2, and RLs3 in the example shown in FIG. 14). Are guided, the pair of reflected lights RLs in the plurality of reflected lights RLs are caused to interfere with each other, and the plurality of interference lights ILs are guided. Here, in the present embodiment, at least one set of the interference light ILs among the plurality of interference lights ILs is generated by causing optical interference using the common reflected light RLs. More specifically, the output-side waveguide 2Ff is the same as the output-side waveguide 2Df in the third embodiment, and includes three waveguide portions 2Ff-1, 2Ff-2, 2Ff-3, and one branch portion. 2Ff-4, two merging portions 2Ff-5, 2Ff-6, and two waveguide portions 2Ff-7, 2Ff-8.

  The phase detection unit 3D performs phase detection while correcting the plurality of interference lights ILs emitted from the measurement unit 2F using the reference light MLsref, and a set obtained by performing optical heterodyne interference using the common reflected light RLs. The phase difference ΔΦ between the interference lights is detected. Then, the phase detection unit 3D outputs the detected phase difference ΔΦ to the calculation control unit 5. More specifically, as shown in FIG. 13, the phase detection unit 3D includes an interference light photoelectric conversion unit 3Da (3Da1, 3Da2), a reference light photoelectric conversion unit 3Da3, an interference signal, and a reference signal. And a mixing unit 3Db (3Db1, 3Db2) for mixing (mixing) and a phase detector 3Dc for the interference signal after mixing.

  Similar to the photoelectric conversion unit 3Ca of the third embodiment, the photoelectric conversion unit 3Da includes a photoelectric conversion element that converts an electric signal having a signal level corresponding to the amount of incident light and outputs the electric signal. . Specifically, the photoelectric conversion unit 3Da3 receives the reference light MLsref branched from the measurement light MLs guided from the measurement light generation unit 1D to the measurement unit 2F, and outputs an electric signal having a signal level corresponding to the light amount. This is output as the reference signal Ref3. Further, each of the photoelectric conversion units 3Da1 and 3Da2 receives two first and second interference lights ILs1 and ILs2 emitted from the output terminal 2Fg of the measurement unit 2F as multi-mode optical fibers and respective input terminals (not shown). The first and second interference signals Sig1 and Sig2 are output to the phase detector 3Dc according to the light amounts of the interference lights ILs1 and ILs2, respectively.

  The mixing unit 3Db (3Db1, 3Db2) mixes the reference signal Ref3 and the interference signals Sig1 and Sig2. Specifically, the mixing unit 3Db1 mixes (divides) the first interference signal Sig1 and the reference signal Ref3, and outputs the mixed first interference signal Sig1. Further, the mixing unit 3Db2 mixes (divides) the second interference signal Sig2 and the reference signal Ref3, and outputs the mixed second interference signal Sig2.

  The phase detector 3Dc receives a plurality of interference signals Sig from the photoelectric conversion unit 3Da and a plurality of interference signals Sig mixed with the reference signal, and uses the reflected light RLs common to the optical heterodyne interference. This is a device for detecting a phase difference ΔΦs between a plurality of interference signals Sig with respect to the set of interference light ILs obtained by the above. In the example shown in FIG. 13, the phase detector 3Dc receives the first and second interference signals Sig1 and Sig2 after the reference signals are mixed by the mixing units 3Db1 and 3Db2, and the first interference signal Sig1 and the first interference signal Sig1 The phase difference ΔΦs between the two interference signals Sig2 is detected. Then, the phase detector 3Dc outputs the detected phase difference ΔΦs to the calculation unit control unit 5.

  The stage 4, the calculation control unit 5, the input unit 6 and the output unit 7 are the same as the stage 4, the calculation control unit 5, the input unit 6 and the output unit 7 in the surface shape measuring apparatus SA of the first embodiment, respectively. Since there is, explanation is omitted.

  Next, operation | movement of the surface shape measuring apparatus SD in this embodiment is demonstrated. In the following description, for the sake of convenience of explanation, a case where there are three measurement points Pn at each measurement point MP will be described by taking the case shown in FIG. 13 as an example.

  When a power switch (not shown) is turned on, the surface shape measuring device SD is activated and necessary parts are initialized by the arithmetic control unit 5. Then, for example, when a measurement object Ob of a plate-like body such as a semiconductor wafer is placed on the stage 4 and receives a command for instructing measurement start from the input unit 6, the arithmetic control unit 5 reads the surface shape of the measurement object Ob. Start measuring.

  At this time, the light source control unit 53 of the arithmetic control unit 5 drives the measurement light generation unit 1D to cause the semiconductor laser light source 1Da to emit laser light whose frequency is periodically shifted. By the emission of a predetermined laser beam from the semiconductor laser light source 1Da, the measurement light MLs is emitted from the output terminal 1Dd of the measurement light generator 1D by the action of the optical system described above.

  Subsequently, the measurement light MLs emitted from the output terminal 1Dd of the measurement light generation unit 1D propagates through the optical fiber and enters the measurement unit 2D. At this time, a part of the measurement light MLs is branched by the reference light branching unit Cref as the reference light MLsref and is incident on the phase detection unit 3D. In the measurement unit 2F, as in the third embodiment, the incident measurement light MLs is branched into a plurality of measurement lights MLs1, MLs2, and MLs3, and irradiated to the measurement points P1, P2, and P3. Subsequently, the measurement unit 2F generates the first and second interference lights ILs1 and ILs2 from the respective measurement lights MLs1, MLs2, and MLs3 by the action of the optical system described above, and the first and second interference lights ILs1 and ILs2 are generated. Injected from the output terminal 2Fg. The first and second interference lights ILs1 and ILs2 emitted from the output terminal 2Fg of the measurement unit 2F propagate through the multimode optical fiber and enter the phase detection unit 3D.

  In the phase detection unit 3D, the reference signal Ref3 is mixed in the mixing unit 3Db with respect to the sets obtained by the self-delay optical heterodyne interference using the reflected light RLs2 common to each other. The phase difference ΔΦs between the first and second interference lights ILs1 and ILs2 is detected by phase detection of the two interference lights ILs1 and ILs2.

  Then, when the measurement unit 2F and the phase detection unit 3D perform such an operation, the stage control unit 52 of the calculation control unit 5 controls the stage 4 so that the measurement object Ob is adjusted to its height. Move in the horizontal direction perpendicular to the direction.

  Subsequently, when each phase difference ΔΦm of each measurement point MPm is acquired, the shape calculation unit 51 of the calculation control unit 5 obtains the gradient Grm at each measurement point MPm as described above, and each of these according to the scanning order. The surface shape of the measurement object Ob is obtained by connecting the gradient Grm at the measurement location MPm.

  Subsequently, the arithmetic control unit 5 outputs the obtained surface shape of the measurement object Ob to the output unit 7, and the output unit 7 displays the surface shape of the measurement object Ob.

  By operating in this way, in the surface shape measuring apparatus SD and the surface shape measuring method mounted thereon in the present embodiment, as in the third embodiment, it is a relatively short time, in the order of nm, and with higher accuracy. The surface shape of the measurement object Ob can be measured. Further, since the surface shape measuring device SD and the surface shape measuring method having such a configuration use the self-delay type optical heterodyne interference method, as in the third embodiment, the light source unit 1Da can be reduced in size, stability, It is possible to improve the flexibility of selection of the light source unit 1Da while improving the life of the light source.

  Furthermore, in the surface shape measuring apparatus SD and the surface shape measuring method having such a configuration, the reference light MLsref is mixed with the interference light ILs, so that the light source unit 1Da included in the measurement light MLs emitted by the measurement light generation unit 1D is mixed. A change in the output intensity can be detected, and the influence of the change in the output intensity on the measurement result can be eliminated by calculating the surface shape of the measurement object Ob while correcting the interference light ILs using this. . As a result, the surface shape measuring apparatus SD having such a configuration can measure the surface shape of the measurement object Ob with higher accuracy than a surface shape measuring apparatus that does not use the reference light MLsref.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

SA, SB Surface shape measuring apparatus 1A, 1B Measuring light generating unit 2A, 2B, 2C Measuring unit 3A Phase difference detecting unit 3B Phase detecting unit 4 Stage 5 Operation control unit 51 Shape calculating unit

Claims (19)

A light source that emits light;
A light splitting unit that divides the light emitted from the light source unit into three or more measurement lights so as to irradiate the measurement light to three or more measurement points in the measurement object, respectively;
The plurality of measurement lights divided by the light dividing unit are irradiated onto the plurality of measurement points on the measurement object, respectively, and a pair of reflected lights in the plurality of reflected lights respectively reflected at the plurality of measurement points are subjected to optical interference. A plurality of optical interference units to be
A detection unit for obtaining a surface shape of the measurement object based on a plurality of interference lights output from the plurality of light interference units,
The surface shape measuring apparatus according to claim 1, wherein at least one set of the light interference units in the plurality of light interference units causes the light interference using reflected light common to each other. The light source unit, the light splitting unit, and the optical interference unit constitute an optical homodyne interferometer,
The detection unit is configured to detect a phase difference between phases in the plurality of interference lights based on a plurality of interference lights output from the plurality of light interference units that have caused the light interference using the reflected light common to each other. The surface shape measuring apparatus according to claim 1, further comprising: a phase difference detection unit; and a calculation unit that calculates a surface shape of the measurement object based on the phase difference detected by the phase difference detection unit. . The light splitting unit includes a light branching unit that divides light emitted from the light source unit into three parts,
The set of optical interference units is a first optical interference unit that optically interferes with the reflected light in the first light divided by the optical branching unit and the reflected light in the second light divided by the optical branching unit. And a second optical interference unit that optically interferes with the reflected light of the second light divided by the optical branching unit and the reflected light of the third light divided by the optical branching unit. The surface shape measuring apparatus according to claim 2. The surface shape measuring apparatus according to claim 3, wherein the one set of optical interference units is an optical waveguide type optical element in which optical waveguides having different refractive indexes are formed on a base material. The surface shape measuring device according to claim 3 or 4, wherein the light splitting portion of the light splitting portion is a diffraction grating. The surface shape measuring device according to claim 3 or 4, wherein the light branching unit of the light splitting unit is an optical waveguide type optical branching unit. The light source unit, the light splitting unit, and the optical interference unit constitute an optical heterodyne interferometer,
The detection unit performs phase detection on each of the plurality of interference lights output from the plurality of optical interference units caused to interfere with each other using the reflected light common to each other, and calculates a phase difference between the phases of the plurality of interference lights. The surface shape measuring apparatus according to claim 1, further comprising: a detection unit that detects the signal and a calculation unit that calculates a surface shape of the measurement object based on the phase difference detected by the detection unit. A first light branching unit that divides light emitted from the light source unit into two parts;
An optical modulation unit that modulates the frequencies of the two lights separated by the first optical branching unit into different frequencies;
The light splitting unit includes a second light branching unit that further divides one of the two lights modulated by the light modulating unit into two,
The one set of optical interference units is a first optical interference unit that causes optical heterodyne interference between reflected light in the other light modulated by the light modulation unit and reflected light in the one light divided by the second branching unit. And a second light interference unit that causes optical heterodyne interference between the reflected light in the other light modulated by the light modulation unit and the reflected light in the other light divided by the second branching unit,
The detection unit of the detection unit detects the phase difference between the phases of the first and second interference lights by detecting the phase of the first and second interference lights output from the first and second optical interference units, respectively. The surface shape measuring device according to claim 7. A first reference light interference unit that causes optical heterodyne interference between the other light modulated by the light modulation unit and the one light divided by the second branching unit;
A second reference light interference unit that causes optical heterodyne interference between the other light modulated by the light modulation unit and the other light divided by the second branching unit,
The detection unit of the detection unit performs phase detection on the first and second reference interference lights output from the first and second reference light interference units, respectively, and detects the position between the phases of the first and second reference interference lights. Detecting a phase difference as a correction value, correcting a phase difference between the phases of the first and second interference lights with the correction value,
The surface shape measurement apparatus according to claim 8, wherein the calculation unit of the detection unit calculates a surface shape of the measurement object based on the phase difference detected and corrected by the detection unit. The surface shape measuring apparatus according to claim 8 or 9, wherein the one set of optical interference units is an optical waveguide type optical element in which optical waveguides having different refractive indexes are formed on a base material. Comprising three or more light guides for guiding each measurement light divided by the light splitting part and irradiating each of the plurality of measurement points,
The light source unit, the light splitting unit, the light guide unit, and the detection unit are to form an optical heterodyne interferometer.
The light source unit emits light whose frequency changes periodically,
The set of light guides for obtaining each reflected light to be optically interfered in the set of light interference units has reflected light common to each other in the set of light interference units of the set of light guide units. A specific light guide unit for irradiating measurement light to the measurement point to be obtained, and a measurement point at which reflected light other than the reflected light common to each other in the set of light interference units of the set of light guide units is obtained. Each of the optical path lengths between the at least two other light guides that irradiate the measurement light has a predetermined optical path difference,
The detection unit performs phase detection on each of a plurality of interference lights output from the plurality of optical interference units caused to interfere with each other using the reflected light common to each other, and calculates a phase difference between the phases of the plurality of interference lights. The surface shape measuring apparatus according to claim 1, further comprising: a detection unit that detects the signal and a calculation unit that calculates a surface shape of the measurement object based on the phase difference detected by the detection unit. The predetermined optical path difference is between the measurement light corresponding to the pair of reflected light in order to cause optical interference between the reflected light obtained from the specific light guide and the reflected light obtained from the other light guide. The surface shape measuring device according to claim 11, wherein the surface shape measuring device is based on a difference in frequency provided to the surface. Three or more measurement points are arranged in a line on the surface of the measurement object,
The plurality of light interference units optically interfere a pair of reflected light in a plurality of reflected light respectively reflected at each measurement point arranged in a row,
In each of the light guides, from the light guide unit that irradiates the measurement light to the measurement point located at one end of the row, the light guide unit that irradiates the measurement light to the measurement point located at the other end of the row. The surface shape measuring device according to claim 11, wherein the optical path length is increased in order by the predetermined optical path difference. Three or more measurement points are arranged in a line on the surface of the measurement object,
The plurality of light interference units optically interfere a pair of reflected light in a plurality of reflected light respectively reflected at each measurement point arranged in a row,
In each of the light guides, from the light guide unit that irradiates the measurement light to the measurement point located at one end of the row, the light guide unit that irradiates the measurement light to the measurement point located at the other end of the row. The surface shape measuring device according to claim 11 or 12, wherein the optical path lengths of the odd-numbered or even-numbered light guides are the same. The surface shape measuring device according to claim 11 or 12, wherein the other light guides are all light guides other than a specific light guide in the set of light guides. 16. The optical waveguide type optical element according to claim 11, wherein the light dividing unit and the plurality of light guiding units are optical waveguide type optical elements in which optical waveguides having different refractive indexes are formed on a base material. Surface shape measuring device. A reference light branching section for branching a part of the light emitted from the light source section upstream of the light splitting section as reference light;
A reference light mixing unit that mixes each of the interference light output from the set of light interference units and the reference light, respectively.
The detection unit detects a phase difference between each phase by detecting a plurality of reference light mixing signals output from the reference light mixing unit; and
The surface shape measuring apparatus according to claim 11, further comprising: a calculation unit that calculates a surface shape of the measurement object based on the phase difference detected by the detection unit. . A light splitting step for dividing the light emitted from the light source unit into three or more measurement lights in order to irradiate the measurement light to three or more measurement points in the measurement object;
The plurality of measurement lights divided in the light splitting step are irradiated on the plurality of measurement points on the measurement object, respectively, and a pair of reflected lights in the plurality of reflected lights respectively reflected at the plurality of measurement points are subjected to optical interference. A plurality of optical interference processes,
A detection step for obtaining a surface shape of the measurement object based on a plurality of interference lights obtained in the plurality of light interference steps,
The surface shape measuring method characterized in that at least one set of the light interference steps in the plurality of light interference steps causes the light interference using reflected light common to each other. A method of measuring the surface shape of a measurement object using optical heterodyne interferometry,
A light splitting step of dividing light periodically radiated from the light source unit into three or more measurement light beams to irradiate measurement light to three or more measurement points on the measurement object, respectively; ,
Three or more light guide / irradiation steps each guiding the plurality of measurement lights divided in the light splitting step and simultaneously irradiating the plurality of measurement points on the measurement object with the measurement lights, respectively;
A plurality of light interference steps of causing a pair of reflected light in the plurality of reflected light reflected respectively at the plurality of measurement points to interfere with each other;
A detection step of obtaining a surface shape of the measurement object based on a plurality of interference lights obtained in the plurality of light interference steps,
At least one set of the light interference steps in the plurality of light interference steps causes the light interference using reflected light common to each other,
A set of light guide / irradiation steps for obtaining each reflected light to be optically interfered in the set of light interference steps is common to the one set of light interference steps in the set of light guide / irradiation steps. Other than the common reflected light in the specific light guide / irradiation step of irradiating the measurement light to the measurement point where the reflected light is obtained and the set of light interference steps in the set of light guide / irradiation steps The measurement light is respectively guided so that the optical path difference between at least two other light guide / irradiation processes for irradiating the measurement light to the measurement point where the reflected light is obtained becomes a predetermined optical path difference. Surface shape measuring device.

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