JP2013160702A - Measuring device, measuring method and manufacturing method of object to be measured - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring device capable of measuring a surface shape of an object to be measured in an actual use environment with high accuracy and low cost.SOLUTION: A measuring device 1 for measuring a surface shape of an object 120 to be measured, using interference of light includes: a probe 103 for irradiating a surface of the object 120 to be measured with light 119, and scanning the surface of the object 120 to be measured in a non-contact manner; a detection part 110 for detecting light 122 from the surface of the object 120 to be measured through the probe 103; a storage part 118 which has a partition wall 118a for separating the object 120 to be measured and the probe 103, and stores the object 120 to be measured; an environment control part 150 for controlling an environment inside the storage part 118; and a calculation part 141 for obtaining the surface shape of the object 120 to be measured, using a detection result of the detection part 110 and information about the partition wall 118a.

Description

  The present invention relates to a measuring apparatus and a measuring method for measuring the surface shape of an object to be measured.

  In recent years, the development of ground telescopes with a primary mirror diameter of 30 m or more has been progressing for the purpose of deep space exploration such as the formation of the universe and the exploration of extrasolar planets. Since it is difficult to manufacture a primary mirror having a diameter of more than 30 m as a single mirror, the primary mirror is usually configured by combining segmented segment mirrors. The surface shape of the segment mirror has a great influence on the optical performance, but it is difficult to measure the segment mirror with high accuracy because the measuring device is enlarged.

  Therefore, the surface shape of the segment mirror is measured by scanning a non-contact probe that uses light interference with respect to the segment mirror that is the object to be measured. Patent Document 1 discloses a method of applying a correction amount according to the angle of the surface to be measured when the light beam is moved along the surface to be measured and the angle of the surface to be measured is measured using the position detection element. It is disclosed. Further, Patent Document 2 discloses a method of measuring the surface shape of a measurement target surface by double-pass laser interference with a non-contact probe and measuring the distance between a reference mirror and the measurement target surface by double-pass laser interference.

Japanese Unexamined Patent Publication No. 01-295109 JP 2009-145095 A

  However, since a large astronomical telescope is often installed near the top of a mountain having an altitude of 4000 m or more, for example, mirror measurement under an actual operating temperature environment may be required. In this case, in order to prevent condensation and freezing of the parts and units of the measuring device and to reduce the temperature control cost, the actual measuring temperature should be set at least around the surface to be measured instead of setting the entire measuring device to the actual operating temperature. It is preferable to set to. At this time, it is necessary to measure the surface shape of the object to be measured by housing the mirror as the object to be measured in the chamber controlled to a desired temperature. In addition, in order to measure the surface shape of an object to be measured, such as a mirror, used under vacuum in outer space with high accuracy, the object to be measured is accommodated in a vacuum-controlled chamber under atmospheric pressure control. It is necessary to measure the surface shape.

  However, since the measurement object is accommodated in the chamber, the surface shape cannot be measured by directly irradiating the measurement surface with light. Therefore, the surface shape of the measurement object cannot be measured with high accuracy.

  Therefore, the present invention provides a measuring apparatus and a measuring method capable of measuring the surface shape of an object to be measured under an actual use environment with high accuracy and low cost. Moreover, the manufacturing method of the to-be-measured object which processes a to-be-measured object based on the measurement result of the surface shape of the to-be-measured object measured using such a measuring device is provided.

  A measuring device according to one aspect of the present invention is a measuring device that measures the surface shape of an object to be measured using light interference, and irradiates the surface of the object to be measured with light, and the surface of the object to be measured A probe that scans in a non-contact manner, a detection unit that detects light from the surface of the measurement object via the probe, a partition that separates the measurement object and the probe, and the measurement object A storage unit, an environment control unit that controls an environment inside the storage unit, a detection result of the detection unit, and a calculation unit that obtains a surface shape of the object to be measured using information about the partition; Have

  A measuring method according to another aspect of the present invention is a measuring method for measuring the surface shape of an object to be measured using light interference, in a state in which the original device is accommodated in the accommodating portion and the original device in the accommodating portion. The surface shape of the original device is measured both in a state of being taken out from the probe, and based on the measurement result of the surface shape of the original device, a probe that scans the surface of the object to be measured in a non-contact manner and the object to be measured A partition information acquisition step for obtaining information about the partition walls of the storage unit disposed between the measurement object, the surface shape of the measurement target in a state in which the measurement target is stored in the storage unit, and the surface of the measurement target Based on the measurement surface information acquisition step for obtaining information on the measurement object based on the measurement result of the shape, and the results obtained in the partition wall information acquisition step and the measurement surface information acquisition step, And a surface shape calculation step for obtaining a surface shape.

  According to another aspect of the present invention, there is provided a method for manufacturing an object to be measured based on a measurement result of a surface shape of the object to be measured which is measured using the measuring device.

  Other objects and features of the present invention are illustrated in the following examples.

  ADVANTAGE OF THE INVENTION According to this invention, the measuring device and measuring method which can measure the surface shape of the to-be-measured object in an actual use environment with high precision and low cost can be provided. Moreover, the manufacturing method of the to-be-measured object which processes a to-be-measured object can be provided based on the measurement result of the surface shape of the to-be-measured object measured using such a measuring device.

1 is a configuration diagram of a measuring device in Example 1. FIG. In Example 1, it is a figure which shows the overlap area | region of the beam which is test light, and the beam which is reference light. 3 is a flowchart illustrating a measurement method according to the first embodiment. It is a principal part enlarged view of the measuring device at the time of the original | special-device measurement in Example 1. FIG. It is a figure which shows the relationship between the to-be-measured surface information matrix in Example 1, and the distance of a probe and a to-be-measured surface. It is a block diagram of the measuring device in Example 2. FIG. 10 is a flowchart illustrating a measurement method according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant description is omitted.

  First, with reference to FIG. 1 thru | or FIG. 5, the measuring apparatus in Example 1 of this invention is demonstrated. FIG. 1 is a configuration diagram of a measurement apparatus 1 (non-contact type three-dimensional measurement apparatus) in the present embodiment, and shows a state of aspheric measurement in a double-pass heterodyne interference method using a corner cube. The measuring device 1 is a measuring device that measures the surface shape of an object to be measured using light interference. The sag amount of the aspherical surface of the object to be measured is, for example, on the order of microns or more.

  In order to measure the surface shape of a workpiece 120 (measurement object) such as a mirror, the measuring device 1 is a probe (interferometer) that scans the measurement workpiece 120 in a non-contact manner while irradiating light on the surface of the measurement object. Probe). In addition, the measuring apparatus 1 accurately measures the surface shape of the workpiece 120 to be measured placed in various environments, and the chamber 118 (accommodating portion) that houses the workpiece 120 to be measured, and the environment inside the chamber 118. An environment control unit 150 for controlling When the workpiece 120 is used in an environment (for example, near the top of a mountain) lower than room temperature (for example, near the top of a mountain), the measurement of the surface shape of the workpiece 120 is controlled to that temperature. Preferably it is done. In such a case, by providing a temperature control unit that controls the temperature inside the chamber 118 as the environment control unit 150, the surface shape of the workpiece 120 to be measured under the actual use temperature environment can be measured more accurately. Is possible. Further, when the workpiece 120 is used in an environment (for example, space) of an atmospheric pressure (for example, vacuum) lower than the atmospheric pressure, the measurement of the surface shape of the workpiece 120 is controlled to the atmospheric pressure. It is preferable to carry out with. In such a case, by providing a pressure control unit that controls the pressure inside the chamber 118 as the environment control unit 150, it is possible to more accurately measure the surface shape of the workpiece 120 to be measured under the actual operating pressure. It becomes possible. The chamber 118 includes a partition wall 118a that separates the workpiece 120 and a probe stage 103 (probe) described later. The partition wall 118a is made of a member that transmits light, such as glass, at least in a portion through which a beam described later passes. When a partition wall (environmental control partition wall) is disposed on the optical path, it is necessary to consider the influence of light transmitted through the partition wall.

  A beam 102 emitted from the laser head 101 is substantially parallel to the X axis and is incident on a polarization beam splitter 104 disposed on the probe stage 103. The probe stage 103 has a drive system (not shown), is controlled by a stage control unit 142 described later, and mainly moves in the XY plane. Further, in FIG. 1, a probe is constituted by each element provided in the probe stage 103. The probe of the present embodiment is a heterodyne interferometer probe using heterodyne interference. The heterodyne interferometer probe is a double-pass heterodyne interferometer probe using a corner cube.

  An optical fiber or a plurality of reflecting mirrors may be provided between the laser head 101 and the polarizing beam splitter 104. The beam 102 has two types of S-polarized light and P-polarized light that are orthogonal to each other. The polarization beam splitter 104 reflects S-polarized light and transmits P-polarized light. That is, in the polarization beam splitter 104, the S-polarized light of the beam 102 is reflected to become a beam 105 substantially parallel to the Z axis and travels toward the λ / 4 plate 106. On the other hand, the P-polarized light of the beam 102 is transmitted, becomes a beam 107 substantially parallel to the X axis, and travels toward the corner cube 108. The beam 107 is reflected by the corner cube 108 in the same direction as the incident direction, and becomes a beam 109. Since the polarization state of the beam 109 remains P-polarized light, the beam 109 passes through the polarization beam splitter 104 again and enters the beam receiving unit 110. The beam 109 is treated as reference light.

  On the other hand, the beam 105 is transmitted through the λ / 4 plate 106, and the beam 111 in a circular polarization state is reflected by the Z reference mirror 112 to become a beam 113. The beam 113 passes through the λ / 4 plate 106 again, and becomes a beam 114 that is P-polarized light orthogonal to S-polarized light. Since the beam 114 is P-polarized light, it passes through the polarization beam splitter 104 and becomes a beam 115. The beam 115 is transmitted through the λ / 4 plate 116, and the beam 117 in a circular polarization state is transmitted through the partition wall 118 a of the chamber 118 to become a beam 119. In FIG. 1, for the sake of simplicity, the partition wall 118a of the chamber 118 is depicted as being disposed in parallel with the XY plane, but in reality, the partition wall 118a is bent due to its own weight. For this reason, the beam 119 is substantially parallel to the Z axis, but the beam 117 and the beam 119 are shifted from each other in the XY plane. Details of this will be described later.

  The beam 119 is reflected by the measurement surface 121 (surface) of the workpiece 120 (measurement object) mounted on the tilt stage 404 (tilt mechanism) to become a beam 122. The workpiece 120 to be measured is held on the tilt stage 404 with multipoint support of, for example, three or more points. Here, if the measurement target surface 121 is inclined by θ [rad] with respect to the XY plane, the beam 122 is inclined by 2θ [rad] with respect to the Z axis. The inclination direction of the partition wall 118 a of the chamber 118 and the inclination direction of the measurement target surface 121 change according to the measurement position of the workpiece 120 to be measured. The beam 122 passes through the partition wall 118 a of the chamber 118 and becomes a beam 123. Again, for the sake of simplicity, the partition wall 118a of the chamber 118 is drawn parallel to the XY plane, but in reality, the partition wall 118a is bent due to its own weight. For this reason, the beam 123 is substantially parallel to the beam 122, but is shifted in a plane perpendicular to the beam 122.

  Subsequently, the beam 123 passes through the λ / 4 plate 116 and becomes a beam 124 that is S-polarized light orthogonal to P-polarized light. Since the beam 124 is S-polarized light, it is reflected by the polarization beam splitter 104 to become a beam 125. Since the λ / 4 plate 116 is thinner and smaller in width than the partition wall 118a of the chamber 118, the self-weight deformation of the λ / 4 plate 116 can be ignored, and the λ / 4 plate 116 has an XY plane. You may think that it is substantially parallel. For this reason, the beam 123 and the beam 124 exist on substantially the same straight line. The beam 125 is reflected by the corner cube 108 in the same direction as the incident direction, and becomes a beam 126. Since the polarization state of the beam 126 remains S-polarized light, it is reflected again by the polarization beam splitter 104 and becomes a beam 127. The beam 127 and the beam 124 are substantially parallel.

  The beam 127 is transmitted again through the λ / 4 plate 116, and the beam 128 in the circular polarization state is transmitted through the partition wall 118 to become a beam 129. Again, for the sake of simplicity, the partition wall 118a of the chamber 118 is drawn parallel to the XY plane, but in reality, the partition wall 118a of the chamber 118 is bent due to its own weight. For this reason, the beam 129 is substantially parallel to the beam 128 but is shifted in a plane perpendicular to the beam 129. Here, the angle of the beam 129 with respect to the Z axis substantially coincides with the angle of the beam 122 with respect to the Z axis, and this angle is 2θ [rad]. The beam 129 is reflected by the measurement target surface 121 to become the beam 130, but the angle of the beam 129 with respect to the Z axis substantially coincides with the angle of the beam 122 with respect to the Z axis, so that the beam 130 is substantially parallel to the Z axis.

  The beam 130 passes through the partition wall 118 a of the chamber 118 and becomes a beam 131. Again, for the sake of simplicity, the partition wall 118a of the chamber 118 is drawn parallel to the XY plane, but in reality, the partition wall 118a of the chamber 118 is bent due to its own weight. For this reason, the beam 131 is substantially parallel to the beam 130 but is shifted in a plane perpendicular to the beam 129. Subsequently, the beam 131 passes through the λ / 4 plate 116 and becomes a beam 132 that is P-polarized light orthogonal to S-polarized light. Since the beam 132 is P-polarized light, it passes through the polarization beam splitter 104 and becomes a beam 133.

  Next, the beam 133 is transmitted through the λ / 4 plate 106, and the beam 134 in a circular polarization state is reflected by the Z reference mirror 112 to become a beam 135. The beam 135 again passes through the λ / 4 plate 106 to become a beam 136 that is S-polarized light that is orthogonal to P-polarized light. Since the beam 136 is S-polarized light, it is reflected by the polarization beam splitter 104 to become the beam 137, and the beam 137 enters the beam receiving unit 110 (detection unit). The beam 137 is treated as test light. In this way, the beam receiving unit 110 detects light (test light) from the surface of the workpiece 120 to be measured via the probe stage 103 (probe).

  In FIG. 1, the beam 137 as the test light and the beam 109 as the reference light are drawn so as not to exist on the same straight line. However, in reality, the beam 137 and the beam 109 are beams having a predetermined spread. It is. For this reason, as shown in FIG. 2, there is an overlapping region 201 in which a part of each beam overlaps. FIG. 2 shows the shapes of the beam 137 and the beam 109 in the beam receiving unit 110. In the present embodiment, the overlapping area 201 may be measured using a CCD or the like, and the angle (local angle) of the measurement target surface 121 described later may be calculated. Moreover, the angle with respect to the X axis, for example, of the beam 137 as the test light can be measured using an autocollimator or the like, and the local angle of the measurement surface 121 described later can be calculated.

  The beam 137 and the beam 109 incident on the beam receiving unit 110 are transmitted to the phase / distance information conversion unit 139 through the optical fiber 138. The phase / distance information conversion unit 139 uses the heterodyne interference phenomenon in the overlapping region 201 to measure the phase shift between the beam 137 as the test light and the beam 109 as the reference light, and uses the phase information as distance information. Convert and output. The distance information output from the phase / distance information conversion unit 139 is sent to the PC 141 (calculation unit). The PC 141 includes a stage control unit 142 that drives the probe stage 103 and an error correction unit 140.

  The stage control unit 142 drives the probe stage 103 so as to perform a raster or vector scan so as to cover all desired measurement regions of the measurement target surface 121. The position and inclination of the probe stage 103 with respect to the Z reference mirror 112, the X reference mirror and the Y reference mirror (not shown) are measured using an interferometer or the like and stored in the PC 141 as position information and inclination information of the probe stage 103. . The position information and tilt information of the probe stage 103 are used for calculating the XY coordinate position of the measurement target surface 121. Note that, as a configuration different from the measurement apparatus 1 of FIG. 1, the workpiece 120 to be measured may be driven instead of driving the probe stage 103. In this case, the stage control unit 142 drives a stage (not shown) on which the workpiece 120 or the tilt stage 404 is mounted. As in the case of driving the probe stage 103, the position and inclination of the workpiece 120 to be measured are measured using an interferometer or the like, and stored in the PC 141 as position information and inclination information of the workpiece 120 to be measured.

  The error correction unit 140 is a calculation unit that obtains the surface shape of the workpiece 120 to be measured using the detection result of the beam receiving unit 110 (detection unit) and information about the partition wall 118a of the chamber 118. That is, the error correction unit 140 corrects an error caused by the partition wall 118a of the chamber 118 between the probe stage 103 (probe) and the workpiece 120 to be measured, and obtains the measurement target surface 121 (surface shape data). The error caused by the partition wall 118a (information about the partition wall) is, for example, an error caused by the shape or refractive index distribution of the partition wall 118a. The error correction unit 140 corrects an error caused by the partition wall 118 a and an error caused by the inclination of the measurement target surface 121, and obtains surface shape data of the measurement target surface 121. The error correction unit 140 has a memory that holds a plurality of two-dimensional distance information output from the phase / distance information conversion unit 139. An error caused by the inclination of the measurement target surface 121 is calculated using partial differential information of a plurality of measurement data stored in the memory. Further, an error caused by the inclination of the measurement target surface 121 may be calculated using design value information of the measurement target surface 121 stored in advance in a memory. Details of the correction by the error correction unit 140 will be described later.

  1 uses a double-pass heterodyne interferometer probe using a corner cube as a probe, but the present embodiment is not limited to this. For example, a homodyne interferometer probe using homodyne interference may be used. In this configuration, a Twiman Green type probe using the Z reference mirror 112 as a reference surface or a Fizeau type probe using a transmission type reference surface is employed.

  In this embodiment, a single-pass heterodyne interferometer probe may be used as the probe. In this case, since the surface to be measured 121 is reflected only once, it is effective when the reflectance of the surface to be measured 121 is small. Also, in FIG. 1, many beams are represented as being parallel to the X-axis or Z-axis, but these are simply drawn, and in fact, all the beams have a slight tilt error. Have

  Next, with reference to FIG. 3, the measuring method in a present Example is demonstrated. FIG. 3 is a flowchart showing the measurement method, and each step is executed by the error correction unit 140 (calculation unit) of the measurement apparatus 1. In steps S301 to S303, the surface shape of the original device is measured using the original device with reference to the Z reference mirror 112, which is the reference surface, and information on the partition wall 118a is acquired based on the measurement result. Here, the information regarding the partition wall 118a includes an error caused by the shape of the partition wall 118a and the refractive index distribution. Steps S301 to S303 are defined as a partition wall information acquisition step. Hereinafter, each step will be described in detail.

  First, in step S301, the surface shape (original surface) of the original device is measured using the original device instead of the workpiece 120 to be measured. At this time, the surface shape of the master is measured without using the chamber 118, that is, without arranging the partition wall 118a of the chamber 118 between the probe and the master. The measurement result obtained in this way is defined as a matrix A. The matrix A is a data array that is equally spaced in the X-axis direction and the Y-axis direction, and is obtained by interpolating a plurality of measurement data that are not equally spaced. Interpolation is performed using various interpolation techniques such as polynomial interpolation and cubic interpolation. Since the data interval is determined in consideration of the required spatial frequency of the measurement data, there is no lack of necessary spatial frequency band information. Hereinafter, with respect to all the matrices in the present embodiment, it is assumed that the data arrays are equally spaced in the X-axis direction and the Y-axis direction and satisfy the necessary spatial frequency band information. In addition, all matrixes include a significant data point that reflects the surface shape and a non-significant data point (Not a Number) that does not reflect the surface shape.

  In this embodiment, the original surface is a flat surface. The original surface has been absolute calibrated in advance by, for example, a three-sheet alignment method using an interferometer or a shear method, and this is defined as a matrix C. Further, a matrix obtained by subtracting the matrix C that is calibration information of the original surface from the matrix A that is the measurement result of the original surface is defined as a matrix A ′. That is, the row example A ′ is expressed as the following formula (1).

A ′ = A−C (1)
The matrix A ′ mainly includes surface shape error information of the Z reference mirror 112. In addition, error information by the polarization beam splitter 104, the λ / 4 plate 106, and the corner cube 108 is also included.

  The error of the matrix A resulting from the position and tilt errors of the probe stage 103 is so small that it can be ignored because the probe measures the surface shape of the original device with the Z reference mirror 112 as a reference. Alternatively, the error of the matrix A resulting from the position and tilt errors of the probe stage 103 may be corrected. Hereinafter, in all the measurement results of the present embodiment, it is assumed that errors in the position and tilt of the probe stage 103 are small enough to be ignored or appropriately corrected.

  Next, in step S302, the surface shape (original surface) of the original device is measured using the chamber 118, that is, with the partition wall 118a of the chamber 118 disposed between the probe and the original device, as in step S301. . The measurement result obtained in this way is defined as a matrix B. As in step S301, a matrix obtained by subtracting the matrix C, which is the configuration information of the original surface, from the matrix B, which is the measurement result of the original surface, is defined as a matrix B '. That is, the matrix B ′ is expressed as the following formula (2).

B ′ = B−C (2)
The matrix B ′ mainly includes the surface shape error information of the Z reference mirror 112, the shape of the partition wall 118a, and an error (information about the partition wall) caused by the refractive index distribution. The surface of the original device (original device surface) used in step S302 is a flat surface as in step S301.

  FIG. 4 is an enlarged view of a main part of the measuring apparatus 1 at the time of measurement by the master 403, and shows an optical path in the vicinity of the partition wall 118a. As described above, the partition wall 118a is bent due to its own weight, and in this case, the partition wall 118a is inclined in the XZ plane. Further, the master 403 itself is held at three or more points so that its own weight does not affect the master surface 402, and the thickness of the master 403 is sufficiently thick. The optical path of the beam 401 is bent by an error caused by the shape of the partition wall 118a and the refractive index distribution, is reflected by the original surface 402 in a state where the optical path length is changed, and returns to the probe through the same optical path as that of the incident. When the workpiece 120 is measured instead of the original device 403 later, the partition wall 118a is similarly held in the same environment.

In FIG. 4, the original device 403 is mounted on a tilt stage 404 that inclines the original device surface 402 (surface to be measured). Using the tilt stage 404, the master surface 402 is tilted a plurality of times in the X-axis direction and the Y-axis direction, and the surface shape data of the master surface 402 is acquired each time. That is, the surface shape (original surface 402) of the original device 403 is measured at a plurality of different angles. These measurement results can be used as correction information for the partition wall 118 a according to the local angle of the measurement target surface 121 when measuring the actual measurement target surface 121. Since the matrix B in the equation (2) can be represented as B (θ _x , θ _y ) as a four-dimensional array, the equation (2) is represented as the following equation (3).

B ′ (θ _x , θ _y ) = B (θ _x , θ _y ) −C (3)
When the original surface 402 is a spherical surface, it is preferable to use an original device in which the curvature radius of the original surface 402 is a curvature radius close to the approximate curvature radius of the surface 121 to be measured. When a spherical surface is used as the original surface 402, the matrix B ′ is a two-dimensional matrix, and the local surface of the measured surface 121 when measuring the actual measured surface 121 is the same as when the original surface 402 is a plane. It can be used as correction information for the partition wall 118a according to the angle. In addition, the number of surface shape measurement data on the original surface can be reduced as compared with the case where a flat original device is used. However, if a spherical original device is used, it is difficult to guarantee the radius of curvature for a predetermined environment (for example, a temperature environment around 2 ° C.), and a configuration that guarantees the absolute value of the radius of curvature around 2 ° C. may be required. is there.

Subsequently, in step S303, a partition wall information matrix D (θ _x , θ _y ) is obtained. The partition wall information matrix D (θ _x , θ _y ) is expressed as the following equation (4).

D (θ _x , θ _y ) = B ′ (θ _x , θ _y ) −A ′ (4)
The partition wall information matrix D (θ _x , θ _y ) includes information on how much the optical path length of the beam changes due to the local shape error of the partition wall 118a and the local refractive index distribution in each pixel. . The shape error of the partition wall 118a includes a deflection due to the weight of the partition wall 118a. The partition wall information matrix D (θ _x , θ _y ) is a four-dimensional array. Each data point can be interpolated using various interpolation techniques such as polynomial interpolation and cubic interpolation. As a result, the partition information corresponding to the local angle of the actual measured surface 121 can be picked up from the interpolation of the partition information matrix D (θ _x , θ _y ) that is a four-dimensional array. A partition information matrix corresponding to the local angle is defined as D ′.

  When the original surface is a spherical surface, a bulkhead information matrix D ′ is used directly without using a four-dimensional array because the original surface has a radius of curvature close to the approximate radius of curvature of the surface 121 to be measured. Can be defined. However, as described above, when a spherical surface is used as the original surface, it is difficult to guarantee the radius of curvature for a predetermined environment (for example, a temperature environment around 2 ° C.).

  As described above, in the partition wall information acquisition step, the surface shape of the master 403 is measured both in the state where the master 403 is accommodated in the chamber 118 and in the state where the master 403 is taken out from the chamber 118. Based on the measurement result of the surface shape of the prototype 403, an error caused by the partition wall 118a of the chamber 118 arranged between the probe and the workpiece 120 to be measured is calculated.

  Next, in steps S <b> 304 and S <b> 305, the surface shape of the workpiece 120 to be measured is measured with the workpiece 120 to be stored in the chamber 118. Then, based on the measurement result of the surface shape of the workpiece 120 to be measured, an error (information on the workpiece) caused by the inclination of the workpiece 120 is obtained. That is, using the workpiece 120 to be measured instead of the master 403, the surface shape of the measurement surface 121 is measured with the Z reference mirror 112 as a reference surface as a reference, and an error caused by the inclination of the measurement surface 121 is calculated. To do. Steps S304 and S305 are defined as a measurement surface information acquisition process. Hereinafter, each step will be described in detail.

  In step S <b> 304, the surface shape of the measurement target surface 121 is measured in a state where the measurement target workpiece 120 is accommodated in the chamber 118. Light is irradiated on the surface of the workpiece 120 to be measured, and the light from the surface of the workpiece to be measured is detected by the beam receiving unit 110 via the probe stage 103. An error due to the partition wall is included in the surface shape of the workpiece 120 to be measured obtained from the detection result of the beam receiving unit. The measurement result obtained at this time is defined as a matrix E. Further, a matrix obtained by subtracting the matrix C, which is calibration information of the original surface 402, from the matrix E is defined as E '. The matrix E ′ is expressed as the following Expression (5).

E ′ = E−C (5)
The matrix E ′ mainly includes an error caused by the shape and refractive index distribution of the partition wall 118 a and an error caused by the inclination of the measurement target surface 121. By subtracting the matrix D ′ from the matrix E ′ represented by Expression (5), a matrix F including only an error caused by the inclination of the measurement target surface 121 can be obtained. The matrix F is expressed as the following equation (6).

F = E′−D ′ (6)
Subsequently, in step S305, a measured surface information matrix (θ _x , θ _y ) regarding the measured surface 121 is obtained. These are obtained by partial differentiation of the matrix F and are expressed as the following Expression (7).

The measured surface information matrix (θ _x , θ _y ) is a local inclination at each pixel of the measured surface 121. However, since each pixel on the measurement target surface 121 performs measurement using two separate beams, it is difficult in terms of configuration to measure a spatial frequency equal to or less than the interval between the two beams. For example, in the configuration shown in FIG. 1, the beam 119 and the beam 129 are separated from each other by a predetermined interval in the X-axis direction. For this reason, it is necessary to set this interval so as to satisfy a desired spatial frequency specification. In the present embodiment, the measured surface information matrix (θ _x , θ _y ) is calculated by partial differentiation of the matrix F, but is calculated using design value information of the measured surface 121 stored in advance in the memory. Also good.

  Next, in step 306, the surface shape of the workpiece 120 to be measured is calculated based on the results obtained in the partition wall information acquisition step (steps S301 to S303) and the measurement surface information acquisition step (steps S304 and S305). Step S306 is defined as a surface shape calculation step.

Here, with reference to FIG. 5, a method for obtaining the distance (distance in the Z-axis direction) between the probe and the measured surface 121 using the measured surface information matrix (θ _x , θ _y ) will be described. FIG. 5 is a diagram showing the relationship between the measured surface information matrix (θ _x , θ _y ) and the distance between the probe and the measured surface. In FIG. 5, L ₁ indicates a distance matrix between the λ / 4 plate 116 that is the lower surface of the probe and the measurement target surface 121. L ₂ represents a beam reflected by the measurement target surface 121 and indicates a distance matrix between the λ / 4 plate 116 and the measurement target surface 121 in an inclined state. X is the distance matrix of the X component of the distance matrix L _2, Y denotes a distance matrix of the Y component of the distance matrix L _2. θ _x represents an angle matrix in the YZ plane of the distance matrix L ₂ , and θ _y represents an angle matrix in the YZ plane of the distance matrix L ₂ . FIG. 5 shows only a part of the measurement target surface 121. Using the distance matrices L ₁ , L ₂ , X, and Y, the following equation (8) is established.

L ₁ ² + X ² + Y ² = L ₂ ² (8)
Here, the matrix F is defined as the following formula (9).

F = L ₁ + L ₂ (9)
At this time, the equation (8) is expressed as the following equation (10).

L ₁ ² + X ² + Y ² = (F−L ₁ ) ² (10)
Here, the distance matrices X and Y are given by the following formula (11), respectively.

X = L ₁ tan θ _y
Y = L ₁ tan θ _x (11)
Therefore, when Expression (11) is applied to Expression (10) and Expression (10) is expanded, the following Expression (12) is established.

L ₁ ² (tan ² θ _y + tan ² θ _x ) + 2FL ₁ −F ² = 0 (12)
When the quadratic equation related to the distance matrix L ₁ represented by the equation (12) is solved, the distance matrix L ₁ is represented as the following equation (13).

Here, it is assumed that the measured surface information matrix (θ _x , θ _y ) is not zero. The case where the measured surface information matrix (θ _x , θ _y ) is zero will be described later.

As described above, by using the matrix F including only errors caused by the inclination of the measurement target surface 121 and the measurement target surface information matrix (θ _x , θ _y ), the λ / 4 plate 116 which is the lower surface of the probe and the measurement target. You can determine the distance matrix _{L 1} between the surface 121. Distance matrix by excluding L ₁ of the piston section, it is possible to calculate the final surface shape of the measurement surface 121 to be obtained.

  Next, with reference to FIG. 6 and FIG. 7, the measuring apparatus in Example 2 of this invention is demonstrated. FIG. 6 is a configuration diagram of the measurement apparatus 2 (non-contact type three-dimensional measurement apparatus) in the present embodiment, and shows a state of planar measurement in the double-pass heterodyne interference method using a corner cube. Here, the sag amount of the plane that is the surface to be measured is, for example, in the order of 10 nm to 100 nm in absolute value.

  The measuring apparatus 2 of the present embodiment is different from the measured work 120 having the aspheric measured surface 121 in that the measuring apparatus 801 having the flat measured surface 802 is measured. However, the other basic configuration of the measuring device 2 is the same as that of the measuring device 1. In this embodiment, the reflected beam reflected by the measurement surface 802 follows the optical path substantially the same as the incident beam in the vicinity of the partition wall 118a. For example, the beam 119 and the beam 122, the beam 129 and the beam 130, the beam 109 and the beam 137 have substantially the same optical path.

Next, with reference to FIG. 7, the measurement method in a present Example is demonstrated. FIG. 7 is a flowchart showing the measurement method. The measurement method shown in FIG. 7 does not require measurement of the original surface 402 from a plurality of angles, and does not require calculation of the measured surface information matrix (θ _x , θ _y ). Different from the measurement method (Example 1).

After calculating the matrix A ′ in step S301, the process proceeds to step S702. When using the planar master 503 and using the workpiece 801 to be measured, the optical paths in the partition wall 118a are substantially the same. For this reason, it is not necessary to acquire correction information of the partition wall 118a according to a plurality of angles using the tilt stage 404. When the matrix B ′ represented by the above equation (2) is represented as B _f ′ in this embodiment, a two-dimensional matrix represented by the following equation (14) is obtained.

B _f ′ = B−C (14)
Subsequently, in step S703, the partition wall information matrix D ′ corresponding to the angle (local angle) of the measurement target surface 802 is not necessary, and only the partition wall information matrix D _f expressed by the following equation (15) is the next step S704. Is required.

D _f = B _f '-A' (15)
Using the equation (15), the above equation (6) is changed to the following equation (16).

F = E′−D _f ′ (16)
Subsequently, in step S705, the measured surface information matrix (θ _x , θ _y ) in the measured surface information acquisition step can be approximated to zero. Therefore, the above equation (12) is expressed as the following equation (17), can be obtained distance matrix L _1.

F = 2L ₁ (17)
By excluding the piston section of the distance matrices L _1, it is possible to calculate the final surface shape of the measurement surface 802 to be obtained.

  In the measurement apparatus 2 of the present embodiment, a double-pass heterodyne interferometer probe using a corner cube is used as a probe. However, when the measurement surface is a substantially flat surface, a reference plane may be used instead of the corner cube. Good. In such a configuration, the beam 119 and the beam 130, and the beam 122 and the beam 129 substantially coincide with each other, and the beam 102, the beam 109, and the beam 137 are separated. Similarly to the first embodiment, the probe may be a homodyne interferometer probe using homodyne interference. In such a configuration, a Twiman Green type probe using the Z reference mirror 112 as a reference surface or a Fizeau type probe using a transmission type reference surface is used. In the measurement apparatus 2 of the present embodiment, a single path heterodyne interferometer probe may be used as the probe. In this case, since the surface to be measured 802 reflects only once, it is effective when the reflectance of the surface to be measured 802 is small.

  According to each of the above embodiments, it is possible to provide a measuring apparatus and a measuring method capable of measuring the surface shape of the measurement object in an actual use environment with high accuracy and low cost. Moreover, the manufacturing method of the to-be-measured object which processes a to-be-measured object can be provided based on the measurement result of the surface shape of the to-be-measured object measured using such a measuring device.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1, 2 Measuring device 103 Probe stage 118 Chamber 120 Work piece 140 Error correction unit 150 Environmental control unit

Claims (12)

A measuring device that measures the surface shape of an object to be measured using light interference,
A probe that irradiates the surface of the object to be measured with light and scans the surface of the object to be measured in a non-contact manner;
A detector that detects light from the surface of the object to be measured via the probe;
A partition that separates the object to be measured and the probe, and an accommodating portion for accommodating the object to be measured;
An environment control unit for controlling the internal environment of the housing unit;
A measurement apparatus comprising: a calculation unit that obtains a surface shape of the object to be measured using a detection result of the detection unit and information on the partition wall.   The measuring apparatus according to claim 1, wherein the information related to the partition wall is an error generated when light passes through the partition wall between the object to be measured and the probe.   The measuring apparatus according to claim 1, wherein the calculation unit corrects an error caused by a shape of the partition wall or a refractive index distribution.   The measuring apparatus according to claim 1, wherein the environment control unit is a temperature control unit that controls a temperature inside the housing unit.   The measuring apparatus according to claim 1, wherein the environment control unit is a barometric pressure control unit that controls a barometric pressure inside the housing unit.   The measuring apparatus according to claim 1, wherein the partition wall is made of a member that transmits light.   The measurement apparatus according to claim 1, wherein the probe is a heterodyne interferometer probe using heterodyne interference.   The measurement apparatus according to claim 7, wherein the heterodyne interferometer probe is a double-pass heterodyne interferometer probe using a corner cube. A measurement method for measuring the surface shape of an object to be measured using light interference,
The surface shape of the original device is measured both in a state where the original device is accommodated in the accommodating portion and in a state where the original device is taken out from the accommodating portion, and the measurement target is based on the measurement result of the surface shape of the original device. A partition information acquisition step for obtaining information on the partition of the storage unit disposed between the probe to scan the surface of the object in a non-contact manner and the object to be measured;
Measurement surface information acquisition for measuring the surface shape of the measurement object in a state where the measurement object is accommodated in the accommodating portion and obtaining information on the measurement object based on the measurement result of the surface shape of the measurement object Process,
A surface shape calculation step for obtaining a surface shape of the object to be measured based on results obtained in the partition wall information acquisition step and the measurement surface information acquisition step.   The measurement method according to claim 9, wherein the measurement method is performed in a state in which a temperature or an atmospheric pressure inside the housing portion is controlled.   The measurement method according to claim 9 or 10, wherein the partition information acquisition step uses a result obtained by measuring the surface shape of the original device at a plurality of different angles.   A method for manufacturing an object to be measured, wherein the object to be measured is processed based on a measurement result of a surface shape of the object to be measured, which is measured using the measuring device according to any one of claims 1 to 8.