JP2004069585A - Method for measuring parallelism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure a parallelism between light-reflecting surfaces by calibrating the gradient information of each light-reflecting surface, based on calibration data from interference fringe image information of each gradient calibration surface by measuring the gradient calibration surface, using a second luminous flux having a larger coherence length, when the intererence fringes are measured by using a first luminous flux having a short coherenct length on each light-reflecting surface of a subject. <P>SOLUTION: A method for measuring the parallelism includes the steps of setting a stage 30 to a first position, obtaining first interference fringe image information of a light-reflecting surface 20a by a light from a light source 11 at a short coherent distance, and obtaining second interference fringe image information of a reflecting mirror 26 by the light from a light source 12 at a large coherence length. The method further includes the steps of setting the stage 30 to a second position, and obtaining third interference fringe image information of the light-reflecting surface 20b and fourth interference fringe image information of the mirror 26, similarly as above. The method also includes the steps of obtaining the slope information on the second and fourth information, and calibrating the difference in the slope information of the first and third information based on the above slope information of the second and fourth, and measuring parellel unevenness between the surfaces 20a and 20b. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a parallelism measuring method for measuring the parallelism between a plurality of light reflecting surfaces with high accuracy, for example, when a plurality of ultra-thin glass plates are arranged on a base at intervals. The present invention relates to a parallelism measuring method capable of measuring the parallelism between the light reflection planes when such planes exist.
[0002]
[Prior art]
For example, in a member in which an ultra-thin glass plate is arranged on the base at a minute interval, the parallelism between the front or back surface of the parallel plane glass and the base (including local parallelism, the following description In this case, there is a demand for measuring parallel unevenness with high accuracy.
[0003]
This type of measurement requires the elimination of interference fringe noise due to surfaces other than the surface to be inspected. Therefore, conventionally, an equal optical path length such as a Michelson type equipped with a light source capable of outputting a light beam with a short coherence distance has been used. It is known to use a type of interferometer device.
[0004]
An example of measurement by the Michelson-type interferometer device will be described. This member is set on a subject mounting stage such that the parallel flat glass is positioned above, and first, the surface of the parallel flat glass is set. Alternatively, the stage is moved up and down to the position where the interference fringes are observed by the back surface to obtain a first interference fringe image, and then the stage is moved up and down to the position where the interference fringes are observed by the base. Then, the second interference fringe image is obtained by moving, and thereafter, the parallel unevenness between the first interference fringe image and the second interference fringe image can be measured based on the difference between the respective pieces of inclination information.
[0005]
[Problems to be solved by the invention]
Since the object mounting stage as described above is mounted on the interferometer device, although it is configured with high precision so that its vertical movement is smooth and the posture of the object can be maintained, The test surface after the movement necessarily has a slight inclination with respect to the test surface before the movement. Therefore, as in the above-described example, when it is necessary to measure the parallel unevenness between the front or back surface of the parallel flat glass and the base with high accuracy, the test is performed along with the movement of the subject mounting stage. It has been difficult to obtain a measurement result that is satisfactory with accuracy due to a change in the surface inclination.
[0006]
The present invention has been made in view of the above circumstances, and uses an illuminating light that can prevent the occurrence of interference fringe noise from a surface other than the surface to be inspected, and uses an interferometer device to measure the parallelism between a plurality of light reflecting surfaces. When measuring with high precision, even if the posture of the subject is tilted with the moving operation of the subject mounting stage for moving the test surface to be measured to a desired position, the tilt can be calibrated with high precision. It is an object of the present invention to provide a parallelism measuring method.
[0007]
[Means for Solving the Problems]
The parallelism measuring method according to the present invention is a method of mounting a test object having a test surface including a plurality of light reflecting surfaces arranged in a vertical direction on a stage, and measuring the parallelism of the plurality of test surfaces with an interferometer device. In the method of measuring using
A first light beam that produces interference fringes whose contrast changes depending on the distance between the test surface and the reference surface of the interferometer device as illumination light of the interferometer device, and a distance between the test surface and the reference surface. Is configured so as to be switchable with a second light beam that produces interference fringes of a predetermined contrast without depending on
The stage is set at a first position where an interference fringe is generated by the first light beam for a first test surface selected from a plurality of the test surfaces, and in this state, the interference fringe is imaged. To obtain a first interference fringe image, and image an interference fringe obtained using the second light flux on a tilt calibration surface fixed so as to be substantially parallel to the plurality of test surfaces. To obtain a second interference fringe image,
Thereafter, the stage is moved in the vertical direction, and the stage is moved to a second position where interference fringes are generated by the first light beam with respect to a second test surface selected from the plurality of test surfaces. In this state, the interference fringes are imaged to obtain a third interference fringe image, and an interference fringe obtained by using the second light flux is imaged on the tilt calibration surface to obtain a fourth interference fringe image. Get a striped image,
Thereafter, based on the difference between the tilt information obtained from each of the second interference fringe image and the fourth interference fringe image, the image is obtained from each of the first interference fringe image and the third interference fringe image. The method is characterized in that the difference between the inclination information is calibrated and the parallelism between the first test surface and the second test surface is measured.
[0008]
Further, the first light beam may be light having a short coherence distance, and the second light beam may be light having a long coherence distance.
In this case, the interferometer device is an equal optical path length interferometer device such as a Michelson type.
[0009]
Further, the first light beam may be multi-wavelength mode light output from a wavelength variable laser light source, and the second light beam may be single wavelength mode light output from a wavelength variable laser light source.
In this case, the interferometer device is an unequal optical path length type interferometer device such as a Fizeau type.
[0010]
Further, the tilt calibration surface can be a mirror surface arranged on the stage.
[0011]
Here, the degree of parallelism represents the degree of parallelism between the two light reflecting surfaces, and is a general term for both the degree of overall parallelism and the degree of local parallelism (parallel unevenness).
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a parallelism measuring method according to an embodiment of the present invention will be described with reference to the drawings.
[0013]
<First embodiment>
FIG. 1 is a schematic diagram showing a configuration of an interferometer apparatus for performing the parallelism measuring method according to the first embodiment.
[0014]
As shown in the figure, the interferometer apparatus 100 is capable of vertically moving a subject 20 having a Michelson type (Twiman Green type) interferometer 10 and a plurality of light reflecting surfaces 20a to 20c and having two axes. It comprises a subject stage 30 which can be tiltably held, a computer 40 and a monitor 50, and a plurality of light reflecting surfaces 20a to 20c are respectively provided on the subject surface while the subject 20 is held on the subject stage 30. By performing the interference fringe measurement, it is possible to measure the parallel unevenness between the plurality of light reflecting surfaces with high accuracy.
[0015]
Note that the subject 20 in the present embodiment is, for example, a member in which a thin glass plate is disposed at a minute interval on a base, and the light reflecting surface 20a is an opaque surface, for example. The light reflecting surfaces 20b and 20c are light transmitting surfaces.
[0016]
The interferometer main body 10 includes a first light source 11 such as a halogen lamp having a short coherence distance, a second light source 12 such as a laser having a long coherence distance, and a light beam for selectively switching the two light sources 11 and 12. It comprises a switching mirror 13, a beam expander 14, a beam splitter 15, a reflective reference plate 16, a converging lens 17, an imaging lens 18, and an imaging device 19 such as a CCD camera.
[0017]
In the interferometer main body 10, the illumination light output from the first light source 11 or the second light source 12 is made incident on the light beam splitting surface 15a of the beam splitter 15, and the transmitted light beam and the reflected light beam are reflected on the light beam splitting surface 15a. Into two parts. Then, the transmitted light beam is made incident on the reference plate 16 and its reflected light is used as reference light, and the reflected light beam is made incident on the surface to be inspected and its reflected light is used as object light. The generated interference fringes are captured by the imaging device 19 and interference fringe image information is measured.
[0018]
Further, the reference plate 16 is supported by a PZT stage 25 via a plurality of piezo elements (not shown) connected to a PZT drive circuit (not shown). Then, in the interferometer apparatus 100, the reference plate 16 is moved in the optical axis direction by applying a predetermined voltage to the piezo element at a predetermined timing and driving the piezo element according to an instruction from the computer 40. The image data of the interference fringe that changes due to the movement is output from the CCD camera 19 to the computer 40.
[0019]
A reflection mirror 26, which is a point in the present embodiment, is held on the subject stage 30.
[0020]
Further, as described above, the output light from the first light source 11 having a short coherent distance and the output light from the second light source 12 having a long coherent distance are switched by the light beam switching mirror 13, When the light beam switching mirror 13 is arranged at the position shown in the figure, the output light from the second light source 12, on the other hand, moves from the position at which the light beam switching mirror 13 is shown to a predetermined retracted position (not shown; (The same), the output light from the first light source 11 is incident on the beam expander 14, respectively. The movement of the light beam switching mirror 13 may be performed manually, or may be automatically performed according to a program of the computer 40.
[0021]
Since the output light from the first light source 11 has a short coherence distance, the reference light from the reference plate 16 and the object light from the predetermined light reflecting surfaces 20a to 20c have exactly the same optical path length. That is, interference fringes are generated on the predetermined light reflecting surfaces 20a to 20c only at predetermined positions within the movement range of the subject stage 30. Therefore, when the interference fringes on the desired light reflecting surfaces 20a to 20c are generated by the movement of the subject stage 30 in the vertical direction (arrow A), interference from the other light reflecting surfaces 20a to 20c occurs. No fringes are generated, and the obtained interference fringe information is obtained by eliminating interference fringe noise, so that the desired light reflecting surfaces 20a to 20c can be well represented.
[0022]
On the other hand, since the output light from the second light source 12 has a long coherent distance, the reference light from the reference plate 16 and the object light from the predetermined light reflecting surfaces 20a to 20c do not have the same optical path length, and thus do not have the same optical path length. The interference fringes of the light reflecting surfaces 20a to 20c are generated, and it is possible to obtain desired interference fringe information on the light reflecting surfaces 20a to 20c in the entire range of the moving range of the subject stage 30. is there. Therefore, in the present embodiment, the output light from the second light source 12 is used to obtain interference fringe information for each position of the reflecting mirror 26 that moves by the same distance as the subject stage 30 that moves up and down. Used.
[0023]
Hereinafter, a measurement procedure of the parallelism measurement method according to the first embodiment using the interferometer apparatus 100 will be described.
[0024]
<1> First, the light beam switching mirror 13 is moved from the position shown in FIG. 1 to a predetermined retreat position and set, and output light from the first light source 11 having a short coherence distance is used as illumination light. The object stage 30 is moved up and down and around the two axes so that the output light from the first light source 11 forms an interference fringe on the first light reflecting surface 20a on the imaging device of the imaging device 19. Perform the tilting operation.
[0025]
<2> Interference fringes on the first light reflection surface 20a obtained by using the first light source 11 are imaged by the imaging device 19, and the obtained interference fringe image information (first interference fringe image information) Is stored in a memory (not shown) of the computer 40.
[0026]
<3> Next, while the object stage 30 is kept as it is, the light beam switching mirror 13 is moved to the position shown in FIG. 1, and the output light from the second light source 12 having a long coherence distance is used as illumination light. .
[0027]
<4> An interference fringe of the reflection mirror 26 obtained by using the second light source 12 is imaged by the imaging device 19, and the obtained interference fringe image information (second interference fringe image information) is Store in memory.
[0028]
<5> The light beam switching mirror 13 is moved from the position shown in FIG. 1 to a predetermined retreat position, and output light from the first light source 11 having a short coherence distance is used as illumination light. The object stage 30 is moved up and down and around the two axes so that the output light from the first light source 11 forms an interference fringe on the second light reflecting surface 20b on the imaging device of the imaging device 19. Perform the tilting operation.
[0029]
<6> Interference fringes on the second light reflection surface 20b obtained by using the first light source 11 are imaged by the imaging device 19, and the obtained interference fringe image information (third interference fringe image information) Is stored in the memory of the computer 40.
[0030]
<7> Next, while the object stage 30 is kept as it is, the light beam switching mirror 13 is moved to the position shown in FIG. 1, and the output light from the second light source 12 having a long coherence distance is used as illumination light. .
[0031]
<8> An interference fringe of the reflection mirror 26 obtained by using the second light source 12 is imaged by the imaging device 19, and the obtained interference fringe image information (fourth interference fringe image information) is Store in memory.
[0032]
<9> A difference between the tilt information extracted from each of the second interference fringe image information and the fourth interference fringe image information stored in the memory is determined, and based on the difference, the first interference fringe image is determined. The difference between the information and the inclination information extracted from each of the third interference fringe image information is calibrated.
[0033]
<10> If necessary, the above steps <5> to <8> are also performed on the third light reflecting surface 20c, and the fifth interference fringe image information on the third light reflecting surface 20c and the reflecting mirror at that time The sixth interference fringe image information of the light-reflection surface 26 is obtained, and the procedure <9> is performed to calibrate the parallel unevenness between the light reflection surface 20c and the light reflection surface 20a or the light reflection surface 20b.
[0034]
In the present embodiment, as described above, at the time of measuring each of the light reflecting surfaces 20a to 20c, the measurement of the reflection mirror 26 is also performed to obtain the inclination calibration data. The difference between the inclination information of the light reflecting surfaces 20a to 20c calibrated based on the above, that is, the measurement of the parallel unevenness between the light reflecting surfaces 20a to 20c can be made with high accuracy.
The parallel unevenness between the light reflecting surfaces 20b and 20c is the thickness unevenness of the glass plate in the above-described example.
[0035]
In the above-described embodiment, the output light from the first light source 11 is constituted by light having a short coherence distance, and the output light from the second light source 12 is constituted by light having a long coherence distance. The output light is switched between when measuring the light reflection surfaces 20a to 20c and when measuring the reflection mirror 26. However, as in the embodiment described below, the multi-wavelength mode light output from the wavelength-variable laser light source is changed. Used in place of the light having a short coherence distance, the light of the single wavelength mode output from the wavelength tunable laser light source is used in place of the light having a long coherence distance, and the light of the light reflection surface is multi-wavelength mode. The measurement may be performed, and the measurement of the reflection mirror may be performed using the light of the single wavelength mode. In this case, as will be described later, it becomes possible to use an interferometer device such as a Fizeau type having an unequal optical path length as the interferometer device.
[0036]
<Second embodiment>
Hereinafter, a parallelism measuring method according to the second embodiment will be described. First, a configuration of an interferometer apparatus for performing the parallelism measuring method will be described with reference to FIG.
[0037]
As shown in the figure, the interferometer apparatus 101 includes a Fizeau-type interferometer main body 110 for observing the surface shape of a test surface 117a of a transparent parallel flat glass plate (subject) 117 using interference fringes, a computer 120, It comprises a monitor 121, a power supply (LD power supply) 122 for a semiconductor laser light source (LD) 111, and a function generator 123 for generating a control signal for controlling an output current value from the power supply (LD power supply) 122.
[0038]
The interferometer body 101 transmits the coherent light from the semiconductor laser light source 111 to a collimator lens 112, a diverging lens 113, a beam splitter 114, a collimator lens 115, and a subject (parallel flat glass plate) 117 via a work space. And a reference plate 116 having a reference surface 116a, and an imaging lens 118 and a CCD imaging device 119 for imaging interference fringes obtained by optical interference.
[0039]
In this interferometer main body 110, a laser beam 140 from a semiconductor laser light source 111 is made incident on a reference surface 116a of a reference plate 116, and is divided into a transmitted light beam and a reflected light beam on the reference surface 116a. The incident light is incident on the test surface 117a of the flat glass plate 117, the reflected light is used as object light, and the reflected light on the reference surface 116a is used as reference light, and the interference light generated by the optical interference between these object light and the reference light is used as the collimator lens 115. , A beam splitter 114 and an image pickup lens 118 to guide the image to a CCD image pickup apparatus 119, which picks up an interference fringe.
[0040]
The captured interference fringes are analyzed by the computer 120, so that the surface shape of the test surface 117a can be measured. The captured interference fringes and the analyzed surface shape of the test surface 117a are displayed on the monitor 121.
[0041]
The parallel flat glass plate 117 as an object is held on an object stage 130 which holds the object vertically and tiltably around two axes.
Further, on the subject stage 130, a reflection mirror 126 that functions similarly to the reflection mirror 26 of the first embodiment is held.
[0042]
The reference plate 116 is supported by a reference plate support member (not shown) via a piezo element 124 connected to a PZT drive circuit (not shown). Then, in accordance with an instruction from the computer 120, a predetermined voltage is applied to the piezo element 124 to drive the piezo element 124, whereby the reference plate 116 is moved by a predetermined phase in the optical axis direction (the horizontal direction in the drawing). . The image data of the interference fringes changed by this movement is output to the computer 120, and fringe image analysis is performed on the plurality of image data.
[0043]
The semiconductor laser light source 111 is provided with a temperature control function. As described above, when the injection current is kept constant, a single-wavelength mode laser beam (for example, a single wavelength having a wavelength λ of about 650 nm) is oscillated. On the other hand, when the injection current is changed, the wavelength and light intensity of the output laser light changes, and the laser light becomes a multi-wavelength mode laser light.
[0044]
Further, the imaging device 119 uses a CCD in which one light accumulation period is 1/30 (second).
The control signal output from the function generator 123 is a rectangular wave (including a step-like rectangular wave) having a frequency of, for example, about 200 Hz, and reproduces image information captured by a CCD. The speed is set to such an extent that flicker does not occur.
[0045]
Further, the interferometer device 101 of the present embodiment is configured as follows in order to prevent occurrence of interference fringe noise.
That is, when outputting the laser light of the multi-wavelength mode, the semiconductor laser light source 111 of the single longitudinal mode is used, and is sufficiently shorter than one light accumulation period of the element (CCD of the CCD imaging device 119) that receives the interference fringes. The laser light 140 output from the light source 111 is periodically modulated to a plurality of wavelengths, and the interference light from the subject 117 is received by the element so that the interference light is integrated over the one light accumulation period. I have to.
[0046]
The semiconductor laser light source has a feature that the wavelength changes by changing the injection current, and the element that receives the interference fringes has a predetermined light accumulation period. In the mode, by scanning the wavelength at a speed sufficiently faster than the one light accumulation period, the same result as in the case of observing interference fringes using a light source that outputs light of multiple wavelengths simultaneously can be obtained. .
[0047]
Next, a case where the surface of the test surface 117a is measured by the light in the multi-wavelength mode will be conceptually described with reference to FIG. 3 showing a change in contrast of interference fringes. In the interferometer device 101 of the present embodiment, as shown in FIG. 3, when the distance to the optical axis changes, the interference fringe contrast changes periodically. In FIG. 3, interference fringes with good contrast are formed between the reference surface 116a and the subject surface 117a by setting the subject surface 117a (first light reflecting surface) to be in a “mountain” state. By setting the interference fringe contrast on the back surface 117b of the subject to 0, the interference fringe noise on the back surface 117b of the subject is eliminated.
[0048]
As described above, in the present embodiment, using light in the multi-wavelength mode corresponds to using light having a short coherence distance in the first embodiment, while using light in the single-wavelength mode is as described above. This corresponds to using light having a long coherence distance in the first embodiment.
[0049]
Hereinafter, a measurement procedure of the parallelism measurement method according to the second embodiment, which is performed using the above-described interferometer apparatus, will be described with reference to FIGS. Here, a case will be described in which parallel unevenness (thickness unevenness) between the test surface 117a as the first measurement surface and the subject back surface 117b as the second measurement surface is measured.
[0050]
<1> First, the function generator 123 is adjusted so that the light beam output from the semiconductor laser light source 111 is set to a predetermined multi-wavelength mode, and the laser light in the multi-wavelength mode is used as illumination light. The up-down movement operation and the tilt operation around the two axes of the subject stage 130 are performed by the laser light in the multi-wavelength mode on the imaging device of the imaging device 119 so that an interference fringe with good contrast is formed on the test surface 117a. (FIG. 4).
[0051]
<2> An interference fringe on the test surface 117a obtained by using the laser light in the multi-wavelength mode is imaged by the imaging device 119, and the obtained interference fringe image information (first interference fringe image information) is computer-generated. 120 in a memory (not shown).
[0052]
<3> Next, the function generator 123 is adjusted while the object stage 130 is kept as it is, so that the light beam output from the semiconductor laser light source 111 is switched to a predetermined single wavelength mode. Is used as illumination light.
[0053]
<4> An interference fringe (see FIG. 5) on the reflection mirror 126 obtained by using the laser light in the single wavelength mode is imaged by the imaging device 119, and the obtained interference fringe image information (second interference fringe image) Information) in the memory of the computer 120.
[0054]
<5> The function generator 123 is adjusted to switch the light beam output from the semiconductor laser light source 111 to a predetermined multi-wavelength mode, and the laser light in the multi-wavelength mode is used as illumination light. The subject stage 130 is vertically moved and tilted about two axes so that interference fringes on the subject back surface 117b are formed on the imaging device of the imaging device 119 by the multi-wavelength mode laser light. (FIG. 6).
[0055]
<6> An image of the interference fringe on the back surface 117b of the subject obtained by using the laser light in the multi-wavelength mode is captured by the imaging device 119, and the obtained interference fringe image information (third interference fringe image information) is processed by a computer. 120 in a memory (not shown).
[0056]
<7> Next, the function generator 123 is adjusted while keeping the object stage 130 as it is, and the light beam output from the semiconductor laser light source 111 is switched to a predetermined single wavelength mode. Is used as illumination light.
[0057]
<8> An interference fringe (see FIG. 7) on the reflection mirror 126 obtained by using the laser light in the single wavelength mode is imaged by the imaging device 119, and the obtained interference fringe image information (the fourth interference fringe image) Information) in the memory of the computer 120.
[0058]
<9> A difference between the tilt information extracted from each of the second interference fringe image information and the fourth interference fringe image information stored in the memory is determined, and based on the difference, the first interference fringe image is determined. The difference between the information and the inclination information extracted from each of the third interference fringe image information is calibrated.
[0059]
In the present embodiment, as described above, at the time of measuring the test surface 117a and the subject back surface 117b, the measurement is also performed on the reflection mirror 126 to obtain the tilt calibration data. The difference between the tilt information of the test surface 117a and the tilt information of the subject back surface 117b calibrated based on the data, that is, the measurement of the parallel unevenness (thickness unevenness) of the test surface 117a and the subject back surface 117b can be made highly accurate. it can.
[0060]
8 to 11 show the respective interference fringe image information obtained by the above-described respective measurement procedures. In each figure, the large interference fringes on the right are for the test surface 117a and the back surface 117b of the subject, and the interference fringes in the small circle on the left are for the reflection mirror 126.
[0061]
That is, in FIG. 8, the interference stage image information (corresponding to the first interference fringe image information) on the test surface 117a is obtained by using the multi-wavelength mode light as the illumination light and moving the object stage 130. FIG. 9 shows an example in which the object stage 130 is left as it is, and light of a single wavelength mode is used as illumination light, and interference fringe image information (a second interference fringe image information Response).
[0062]
FIG. 10 shows a case where light of a multi-wavelength mode is used as illumination light, and the object 130 is moved to obtain interference fringe image information (corresponding to third interference fringe image information) on the back surface 117b of the object. FIG. 11 shows that interference light image information (corresponding to the fourth interference fringe image information) of the reflection mirror 126 is used while the object stage 130 is intact and light of a single wavelength mode is used as illumination light. ).
[0063]
Note that the parallelism measuring method of the present invention is not limited to the above-described embodiment, and other various aspects can be changed. For example, the order of the light reflecting surfaces to be measured may be performed in any order, and the measurement can be performed in order from the light reflecting surface farther from the light source or from the light reflecting surface closer to the light source. .
[0064]
In addition, the light reflecting surface that can be measured is not limited to the above-described one. For example, as long as the light reflecting surface is arranged in a step-like manner, it can be measured even with an opaque light reflecting surface. .
[0065]
In addition, various modes can be considered as the order of calculation when calibrating the parallelism of the plurality of test surfaces, and as a result, the “second interference fringe image and the fourth And a state in which the difference between the tilt information obtained from each of the first and third interference fringe images is calibrated based on the difference between the tilt information obtained from each of the interference fringe images.
[0066]
Further, the interferometer device used for the measurement is not limited to the above embodiment, and various types of interferometer devices can be used.
[0067]
In addition, the parallelism measurement method of the present invention is applicable to various types of test objects, and needs to be set to a small size and high accuracy, for example, an optical member used in a semiconductor manufacturing process or the like. It is particularly useful for measuring a member having a plurality of light reflecting surfaces.
[0068]
【The invention's effect】
As described above, according to the parallelism measurement method of the present invention, as the illumination light of the interferometer device, an interference fringe whose contrast changes depending on the distance between the test surface and the reference surface of the interferometer device is generated. The first light beam and the second light beam that generates interference fringes having a predetermined contrast without depending on the distance between the test surface and the reference surface are configured to be switchable, and each light reflection on the test object is performed. When measuring the interference fringes of the surface using the first light beam, the second light beam is used to perform measurement on the tilt calibration surface fixed and arranged substantially parallel to the reflection mirror, Since the inclination calibration data is obtained from the interference fringe image information of each inclination calibration surface, the difference between the inclination information of each light reflection surface calibrated based on the calibration data, that is, the parallelism between each light reflection surface Measurement can be highly accurate
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an interferometer apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram of an interferometer apparatus according to a second embodiment of the present invention.
FIG. 3 is a view showing the operation of the interferometer apparatus shown in FIG. 2;
FIG. 4 is an explanatory diagram when an interference fringe image is obtained on a surface to be inspected using light in a multi-wavelength mode as illumination light using the interferometer apparatus shown in FIG. 2;
FIG. 5 shows a case where an interference fringe image is obtained on a reflection mirror surface using the interferometer apparatus shown in FIG. 2 and the object stage in the same state as the measurement in FIG. Illustration of
FIG. 6 is an explanatory diagram for obtaining an interference fringe image on the back surface of a subject by using the interferometer apparatus shown in FIG. 2 and using light in a multi-wavelength mode as illumination light.
FIG. 7 shows a case where an interference fringe image is obtained on a reflection mirror surface using the interferometer apparatus shown in FIG. Illustration of
FIG. 8 is a diagram showing an interference fringe image obtained on a surface to be measured by using the interferometer apparatus shown in FIG. 2 and using a multi-wavelength mode light as illumination light and moving a stage.
FIG. 9 shows an interference fringe image obtained on a reflection mirror surface using the interferometer apparatus shown in FIG. 2 and the object stage in the same state as in the measurement in FIG. 8, using single-wavelength mode light as illumination light. Figure showing
FIG. 10 is a diagram showing an interference fringe image obtained on the back surface of a subject by using the interferometer apparatus shown in FIG. 2 and using a light in a multi-wavelength mode as illumination light and moving a stage.
FIG. 11 shows an interference fringe image obtained on a reflection mirror surface using the interferometer apparatus shown in FIG. 2 and the object stage in the same state as in the measurement of FIG. 10, using single-wavelength mode light as illumination light. Figure showing
[Explanation of symbols]
10,110 Interferometer body
11 First light source
12 Second light source
13 Light beam switching mirror
14 Beam expander
15, 114 beam splitter
16, 116 Reference plate
16a, 116a Reference plane
17 Convergent lens
18, 118 Imaging lens
19, 119 Imaging device (CCD camera)
20 subjects
20a-c Light reflecting surface (test surface)
26, 126 Reflecting mirror
30, 130 Subject stage
40, 120 computers
50, 121 monitors
25 PZT stage
100, 101 interferometer device
111 Semiconductor laser light source (LD)
112,115 Collimator lens
113 Divergent lens
117 Parallel flat glass plate (subject)
117a Test surface
117b Back side of subject
122 Power supply (LD power supply)
123 Function Generator
124 piezo element

Claims (6)

A method of mounting a subject having a test surface composed of a plurality of light reflecting surfaces arranged in a vertical direction on a stage and measuring the parallelism of the plurality of test surfaces using an interferometer device,
A first light beam that produces interference fringes whose contrast changes depending on the distance between the test surface and the reference surface of the interferometer device as illumination light of the interferometer device, and a distance between the test surface and the reference surface. Is configured so as to be switchable with a second light beam that produces interference fringes of a predetermined contrast without depending on
The stage is set at a first position where an interference fringe is generated by the first light beam for a first test surface selected from a plurality of the test surfaces, and in this state, the interference fringe is imaged. To obtain a first interference fringe image, and image an interference fringe obtained using the second light flux on a tilt calibration surface fixed so as to be substantially parallel to the plurality of test surfaces. To obtain a second interference fringe image,
Thereafter, the stage is moved in the vertical direction, and the stage is moved to a second position where interference fringes are generated by the first light beam with respect to a second test surface selected from the plurality of test surfaces. In this state, the interference fringes are imaged to obtain a third interference fringe image, and an interference fringe obtained by using the second light flux is imaged on the tilt calibration surface to obtain a fourth interference fringe image. Get a striped image,
Thereafter, based on the difference between the tilt information obtained from each of the second interference fringe image and the fourth interference fringe image, the image is obtained from each of the first interference fringe image and the third interference fringe image. A method of measuring parallelism, comprising: calibrating a difference between pieces of inclination information and measuring a parallelism between the first test surface and the second test surface. 2. The parallelism measuring method according to claim 1, wherein the first light beam is made of light having a short coherence distance, and the second light beam is made of light having a long coherence distance. The said 1st light beam consists of the light of the multiple wavelength mode output from the wavelength variable laser light source, The said 2nd light beam consists of the light of the single wavelength mode output from the wavelength variable laser light source. 1. The method for measuring parallelism according to 1. The parallelism measuring method according to claim 1, wherein the tilt calibration surface is a mirror surface disposed on the stage. 5. The parallelism measuring method according to claim 1, wherein the interferometer is an equal optical path length interferometer such as a Michelson type. 5. The parallelism measuring method according to claim 1, wherein the interferometer device is an unequal optical path length type interferometer device such as a Fizeau type.

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