JP2021117190A - measuring device - Google Patents

Abstract

To provide a measuring device, with which it is possible to contactlessly measure the surface roughness, contour shape, etc., of a component provided in the inside of a vacuum container while maintaining the vacuum state of the vacuum container.SOLUTION: When measuring the surface in an X-axis direction of an upper electrode 12, etc. (measurement object) provided in the inside of a vacuum container 10 and having a surface parallel to the XY plane, a holding shaft 40 is inserted into the vacuum container 10 via an opening 10A formed to the vacuum container 10 and a prism mirror 44 held at the tip of the holding shaft 40 is arranged at a desired position inside of the vacuum container 10. Thus, it is possible to irradiate the surface of the measurement object with measurement light even when the internal space of the vacuum container 10 is narrow. Furthermore, as the holding shaft 40 has airtightness between the opening 10A provided to the vacuum container 10 and itself maintained by airtight means and is capable of moving in the direction of an axis X, measurement light can be entered to the surface of the measurement object while maintaining the vacuum state of the vacuum container 10.SELECTED DRAWING: Figure 1

Description

The present invention relates to a measuring device, and more particularly to a technique for measuring surface roughness, contour shape, etc. of components provided inside a vacuum vessel.

Plasma etching equipment, plasma CVD (plasma-enhanced chemical vapor deposition) equipment, sputtering equipment, etc. for semiconductor manufacturing equipment supply gas for processing workpieces into a vacuum vessel and turn it into plasma in the vacuum vessel. Etching the work or forming a thin film on the work. Therefore, with the operating time of the device, the performance of the device changes due to the consumption of the components in the vacuum vessel and the film formation (also called Depot membrane).

Conventionally, in order to prevent changes in the performance of this type of equipment, abnormality monitoring is performed with various monitoring equipment installed in the equipment, and inspection workpieces are periodically processed according to the number of workpieces processed and operating time. However, we have not directly confirmed changes in performance (for example, wear of component parts, depot film, etc.).

On the other hand, a shape measuring device for measuring the three-dimensional shape of the surface of an object to be measured is described in, for example, Patent Document 1.

The shape measuring device described in Patent Document 1 uses a light source that emits low coherence light such as white light, and the low coherence light emitted from the light source is divided into measurement light and reference light by a beam splitter and divided. The measurement light is incident on the object to be measured, and the reference light is incident on the reference mirror.

The return light of the measurement light reflected on the surface of the measurement object and the return light of the reference light reflected by the reference mirror are combined by the beam splitter and interfere with each other. The interference light between the measurement light and the reference light is detected by the light detection means, the position of the reference mirror when the intensity of the interference light is maximized is detected, and the third order of the surface of the measurement object irradiated with the measurement light. Measure the original shape.

Japanese Unexamined Patent Publication No. 2014-98572

When measuring the three-dimensional shape of the surface of a component provided inside the vacuum vessel by the shape measuring device described in Patent Document 1, it is necessary to open the vacuum vessel. The vacuum container has a problem that once the container is opened, a large downtime occurs in order to return to the original vacuum state again.

Further, even if the vacuum vessel is opened, there are many obstacles in maintaining the process performance in the vacuum vessel, and the three-dimensional shape of the surface of the component is directly measured by the shape measuring device described in Patent Document 1. It is difficult. In this case, it is necessary to take out the component to be measured from the vacuum container, which complicates the work.

The present invention has been made in view of such circumstances, and measures the surface roughness, contour shape, etc. of components provided inside the vacuum vessel in a non-contact manner while maintaining the vacuum state of the vacuum vessel. It is an object of the present invention to provide a measuring device capable of performing.

In order to achieve the above object, in the invention according to the first aspect, a component component provided inside a vacuum vessel and having a surface parallel to the XY plane of the XYZ coordinate system is set as a measurement target, and the surface of the measurement target is set as a measurement target. A non-contact measuring device that emits low coherence light, an optical dividing means that divides the low coherence light emitted from the light source into measurement light and reference light, and measurement light from the optical dividing means. When the emission direction of the light is the X-axis direction, a bending optical member that bends the measured light in a direction orthogonal to the X-axis direction at a position in the X-axis direction separated by the first distance from the optical dividing means, and a bending optical member at the tip. Maintains airtightness between the bending optical member holding shaft, which is held by the portion and the bending optical member is arranged inside the vacuum container through the opening formed in the vacuum container, and the opening and the bending optical member holding shaft. An airtight means for making the bending optical member holding shaft movable in the X-axis direction, a reference light reflector for reflecting reference light emitted from the light dividing means, and at least the light dividing means, the bending optical member holding shaft and the reference. A moving stage that moves the stage equipped with the light reflector in the X-axis direction, a first position detecting means that detects the moving position of the stage, and a reference light reflector that moves the reference light reflector with respect to the stage to obtain the optical path length of the reference light. The reference light path length changing means to be changed, the second position detecting means for detecting the position of the reference light reflector, the measurement light reflected by the measurement object, and the reference light reflected by the reference light reflector are combined into one. The position of the reference light reflector when the intensity of the interference light detected by the light interference means, the light interference means for interfering with each other, the light interference means for receiving the interference light between the measurement light and the reference light, and the interference light detected by the light detection means is maximized is detected. X-axis direction of the surface of the object to be measured based on the third position detecting means, the moving position of the stage detected by the first position detecting means, and the position of the reference light reflector detected by the third position detecting means. A measuring means for measuring the surface of the object to be measured at the position of is provided.

According to the first aspect of the present invention, when measuring the surface in the X-axis direction of a component (measurement object) having a surface parallel to the XY plane and provided inside the vacuum container, it is formed in the vacuum container. The bending optics member holding shaft is inserted into the vacuum vessel through the opening, and the bending optics member held at the tip of the bending optics member holding shaft is arranged at a desired position inside the vacuum vessel. When the emission direction of the measurement light from the optical dividing means (the axial direction of the bending optical member holding axis) is the X-axis direction, the bending optical member bends the measurement light in a direction orthogonal to the X-axis direction. The surface of the object to be measured having a parallel surface can be irradiated with the measurement light. As a result, the surface of the object to be measured can be irradiated with the measurement light even if the internal space of the vacuum container is narrow.

Further, since the bending optical member holding shaft is maintained airtight with the opening provided in the vacuum container by the airtight means and can be moved in the X-axis direction, the vacuum state of the vacuum container is maintained. However, the measurement light can be incident on the surface of the object to be measured.

The moving stage moves the stage on which at least the optical dividing means, the bending optical member holding shaft, and the reference light reflector are mounted in the X-axis direction, so that the measurement light can be measured at a desired position on the surface of the object to be measured in the X-axis direction. Can be irradiated.

The reference optical path length changing means moves the reference light reflector with respect to the stage to change the optical path length of the reference light, and the light detecting means detects the interference light between the measurement light and the reference light while changing the optical path length. do. Then, the measuring means measures the surface of the object to be measured based on the position of the reference light reflector detected by the third position detecting means (the position of the reference light reflector when the intensity of the interference light is maximized). do. The position of the surface of the object to be measured in the X-axis direction is specified by the moving position of the stage detected by the first position detecting means.

The invention according to the second aspect is a measuring device provided inside a vacuum vessel and measuring a component having a surface parallel to the XY plane of the XYZ coordinate system as a measurement object and measuring the surface of the measurement object in a non-contact manner. There are a light source that emits low coherence light, an optical dividing means that divides the low coherence light emitted from the light source into measurement light and reference light, and the emission direction of the measurement light from the light dividing means is the X-axis direction. Then, the bending optical member that bends the measurement light in the direction orthogonal to the X-axis direction at the position in the X-axis direction separated from the optical dividing means by the first distance, and the bending optical member are held at the tip portion and placed in the vacuum vessel. The bending optical member holding shaft for arranging the bending optical member inside the vacuum vessel through the formed opening, and the bending optical member holding shaft for maintaining the airtightness between the opening and the bending optical member holding shaft. A stage equipped with an airtight means that makes it movable in the X-axis direction, a reference light reflector that reflects reference light emitted from the light dividing means, and at least a light dividing means, a bending optical member holding shaft, and a reference light reflector. A moving stage that moves in the X-axis direction, a first position detecting means that detects the moving position of the stage, a measuring device main body that is installed on the stage and includes at least an optical dividing means and a reference light reflector, or a bending optical member holding A precision moving stage that mounts a shaft and slightly moves the measuring device main body or bending optical member holding shaft in the X-axis direction, and a second position detection that detects the moving position of the measuring device main body or bending optical member holding shaft by the precision moving stage. Means, optical interference means for interfering with the measurement light reflected by the measurement object and reference light reflected by the reference light reflector, and light detection means for receiving the interference light between the measurement light and the reference light. A third position detecting means for detecting the position of the measuring device main body or the bending optical member holding shaft when the intensity of the interference light detected by the light detecting means is maximized, and a stage detected by the first position detecting means. Measurement to measure the surface of the object to be measured at the position in the X-axis direction of the surface of the object to be measured based on the moving position of the Means and.

While the invention according to the first aspect includes a reference optical path length changing means for moving the reference light reflector with respect to the stage to change the optical path length of the reference light, the invention according to the second aspect is referred to. The difference is that the optical path length of the measurement light is changed by providing a precision moving stage instead of the optical path length changing means and slightly moving the measuring device main body or the bending optical member holding axis with respect to the stage in the X-axis direction.

In the measuring device according to the third aspect of the present invention, the photodetecting means is an image pickup device having an image pickup surface formed by arranging light receiving elements in a matrix, and the interference light incident on the image pickup surface is the interference light of the image pickup surface. It has a cross section corresponding to the size, the third position detecting means detects the position of the reference light reflector when the intensity of the interference light is maximized for each light receiving element, and the measuring means detects for each light receiving element. It is preferable to measure the surface of the object to be measured based on the position of the reference light reflector.

In the measuring device according to the fourth aspect of the present invention, the photodetecting means is an imaging element having an imaging surface formed by arranging light receiving elements in a matrix, and interference light incident on the imaging surface is transmitted to the imaging surface. The second position detecting means has a cross section of a corresponding size, and the second position detecting means detects the position of the measuring device main body or the bending optical member holding shaft when the intensity of the interference light is maximized for each light receiving element, and the measuring means is It is preferable to measure the surface of the object to be measured based on the position of the measuring device main body or the bending optical member holding shaft detected for each light receiving element.

In the measuring device according to the fifth aspect of the present invention, the airtight means is preferably a feedthrough bellows rod, an O-ring, a magnetic fluid, or a magnet ring.

In the measuring device according to the sixth aspect of the present invention, it is preferable that the measuring means measures at least one of the surface roughness and the contour shape of the object to be measured.

In the measuring device according to the seventh aspect of the present invention, the first distance is preferably a distance longer than the length of the surface of the object to be measured in the X-axis direction.

In the measuring device according to the eighth aspect of the present invention, stage control in which the stage is moved in the X-axis direction and the measurement light is incident on the surface of the measurement object from one end to the other end in the X-axis direction of the surface of the measurement object. It is preferable that the measuring means further includes a portion and measures the entire surface of the surface of the object to be measured in the X-axis direction.

In the measuring device according to the ninth aspect of the present invention, the moving stage has at least a stage equipped with an optical dividing means, a bending optical member holding axis, and a reference light reflector in the X-axis direction and the Y-axis direction of the XYZ coordinate system, respectively. It is an XY stage to be moved, the stage control unit moves the stage in the X-axis direction and the Y-axis direction, respectively, and the measurement light is incident on the entire surface of the measurement object, and the measurement means is the surface of the measurement object. It is preferable to measure the entire area.

In the measuring device according to the tenth aspect of the present invention, it is preferable that the measuring light emitted from the optical dividing means passes through the opening and is incident on the bending optical member.

The measuring device according to the eleventh aspect of the present invention may further include a rotating means for rotating the bending optical member holding shaft around the optical axis of the measurement light emitted from the optical dividing means toward the bending optical member. preferable. This makes it possible to measure the surface of another measurement object facing the measurement object with the bending optical member holding shaft interposed therebetween.

In the measuring device according to the twelfth aspect of the present invention, it is preferable that the measuring light emitted from the light dividing means passes through the window portion made of the first transparent member provided in the vacuum vessel and is incident on the bending optical member. .. Some vacuum containers originally have a window portion made of a first transparent member, and the measurement light can be incident on the inside of the vacuum vessel by using this window portion.

In the measuring device according to the thirteenth aspect of the present invention, it is preferable to include a second transparent member which is arranged between the light dividing means and the reference light reflector and has the same refractive index and thickness as the first transparent member.

According to the present invention, it is possible to measure the surface roughness, contour shape, etc. of the components provided inside the vacuum vessel in a non-contact manner while maintaining the vacuum state of the vacuum vessel.

FIG. 1 is a configuration diagram of a main part showing an outline of a first embodiment of the measuring device according to the present invention. FIG. 2 is a configuration diagram showing a second embodiment of the measuring device according to the present invention. FIG. 3 is a diagram showing a main part of a measuring device main body incorporating a white interference optical system and the like of the measuring device shown in FIG. FIG. 4 is a diagram mainly showing an embodiment of the moving stage shown in FIG. FIG. 5 is a diagram used to explain the white interference conditions of the white interference optical system of the measuring device shown in FIG. 6A and 6B are views used for explaining the measurement principle of a measuring device having a white interference optical system, FIG. 6A is a schematic view of the white interference optical system, and FIG. 6B is an image sensor. 6 (C) is a perspective view showing an image pickup surface of the image sensor, and FIG. 6C is a diagram showing an example of interference light received by each pixel of the image pickup element. FIG. 7 is a block diagram of a main part of the measuring device shown in FIG. FIG. 8 is a configuration diagram of a main part showing a modified example of the measuring device shown in FIG. 2 and the like. FIG. 9 is a main block diagram showing a modified example of the measuring device including the moving stage shown in FIG. FIG. 10 is a diagram showing a modified example of the white interference optical system of the measuring device shown in FIG. FIG. 11 is a diagram showing another embodiment of the moving stage.

Hereinafter, preferred embodiments of the measuring device according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment of Measuring Device]
FIG. 1 is a configuration diagram of a main part showing an outline of a first embodiment of the measuring device according to the present invention.

The measuring device 100-1 of the first embodiment shown in FIG. 1 is applied to the plasma CVD device 1-2.

The plasma CVD apparatus 1-1 includes a vacuum vessel 10, an upper electrode 12, a lower electrode 14 that also serves as an electrostatic chuck, and vertical drive units 16 and 18 that drive the upper electrode 12 and the lower electrode 14 in the vertical direction, respectively. It includes focus rings 20 and 22 and a high-frequency power supply 30. Although not shown in FIG. 1, the plasma CVD apparatus 1-1 is an exhaust means for evacuating the vacuum vessel 10 and a thin film when a thin film is formed on a work (for example, a silicon wafer). It is provided with a gas supply means and the like for supplying a raw material gas, a diluting gas, and the like into the vacuum vessel 10.

The work (not shown) is fixed on the lower electrode 14 by an electrostatic chuck. The upper electrode 12 is provided with a large number of gas ejection holes, and the gas supply means is a raw material gas in the processing space between the upper electrode 12 and the lower electrode 14 in a shower shape from the numerous gas ejection holes of the upper electrode 12. Etc. are supplied.

The upper electrode 12 is connected to the ground, the lower electrode 14 is connected to the ground via the high frequency power supply 30, and the high frequency power supply 30 transfers electric power for generating high frequency gas between the upper electrode 12 and the lower electrode 14. It is applied to turn the raw material gas (diluted gas if necessary) into plasma. The plasma-generated raw material gas is deposited on the work placed on the lower electrode 14 to form a thin film.

The focus rings 20 and 22 are for equalizing the plasma in the processing space between the upper electrode 12 and the lower electrode 14. The vertical drive units 16 and 18 adjust the distance between the upper electrode 12 and the lower electrode 14, and raise and lower the lower electrode 14 in the vertical direction (vertical direction) for loading / unloading the work.

A depot film adheres to the components (for example, upper electrode 12, lower electrode 14, focus ring 20, 22) of the plasma CVD apparatus 1-1 provided inside the vacuum vessel 10 according to the operating time of the apparatus. ..

In FIG. 1, 12A and 14A are depot films attached to the upper electrode 12 and the lower electrode 14, respectively. The depot film is a film that is thickly deposited on a part other than the work when the device is operated for a long period of time.

When the depot film 12A is deposited on the components (for example, the upper electrode 12) of the plasma CVD apparatus 1-1, the depot film 12A closes a part of many gas ejection holes of the upper electrode 12 and is discharged from the gas ejection holes. The raw material gas becomes non-uniform in the plane, and the performance of the plasma CVD apparatus 1-1 changes (decreases).

Here, the performance of the apparatus refers to the processing speed of the work, the in-plane uniformity, the change in the physical characteristics of the material, the decrease in yield due to the generation of particles, and the like.

The measuring device 100-1 is a device for directly confirming the change in the performance of the plasma CVD device 1-1, and is provided inside the vacuum container 10 while maintaining the vacuum state of the vacuum container 10. It measures the surface roughness and contour shape of parts in a non-contact manner.

That is, the measuring device 100-1 has a white interference optical system that uses low coherence light such as white light, and uses the principle of white interference to make a non-contact three-dimensional surface of the work (measurement object). In FIG. 1, a part of the measuring device 100-1 (the part where the measurement light is emitted) is shown. The details of the measuring device having the white interference optical system will be described later.

First, the components (upper electrode 12 and lower electrode 14 in this example) provided inside the vacuum vessel 10 are used as measurement objects, and the surface of the measurement object is a surface parallel to the XY plane of the XYZ coordinate system. Shall have.

That is, the upper electrode 12 and the lower electrode 14 each have a surface parallel to the XY plane of the XYZ coordinate system. Further, the upper electrode 12 and the lower electrode 14 are separated from each other in the Z-axis direction, thereby forming a processing space between the electrodes.

The emitting portion of the measurement light of the measuring device 100-1 includes a holding shaft (bending optical member holding shaft) 40, an airtight member (airtight means) 42, and a prism mirror (bending optical member) 44.

The holding shaft 40 is composed of a long cylinder through which the measurement light passes, and holds the objective lens 43 and the prism mirror 44 at the tip thereof.

The low coherence light (hereinafter referred to as "white light") emitted from a light source (not shown) is divided into measurement light and reference light by a beam splitter (optical division means) constituting the white interference optical system of the measurement device 100-1. Will be done.

Assuming that the measurement light emitted from the beam splitter is in the X-axis direction, the measurement light emitted from the beam splitter in the X-axis direction passes through the inside of the holding shaft 40 and enters the prism mirror 44 via the objective lens 43. do.

The objective lens 43 has a function of condensing the measurement light incident from the beam splitter, and determines the magnification of the surface roughness / contour measurement, the working distance, the field of view, and the like. The prism mirror 44 functions as a bending optical member that bends the measurement light incident from the beam splitter in a direction orthogonal to the X-axis direction, and bends the measurement light by 90 ° to incident the measurement light on the surface of the upper electrode 12. ..

The airtight member 42 maintains the airtightness between the opening 10A provided on the side surface of the vacuum vessel 10 and the holding shaft 40. Further, the airtight member 42 is airtight between the opening 10A and the holding shaft 40 even when the holding shaft 40 moves in the X-axis direction and when the holding shaft 40 rotates about the optical axis of the measurement light. To hold.

The holding shaft 40 and the airtight member 42 can be configured by, for example, a linear acting feedthrough bellows rod. In this case, the rod of the feedthrough bellows rod has a hollow tubular shape. Further, it is preferable that the feedthrough bellows rod is a rotary feedthrough and includes a rotating means (not shown) for rotating the rotary feedthrough around the optical axis of the measurement light.

Further, the airtight member 42 may be composed of an O-ring, a magnetic fluid, a magnet ring, or the like.

According to the above-mentioned measuring device 100-1, by moving the holding shaft 40 in the X-axis direction, the measurement light can be incident on an arbitrary surface of the upper electrode 12 in the X-axis direction, and the X of the upper electrode 12 can be incidented. The three-dimensional shape of the surface can be measured over the surface in the axial direction without contact and while maintaining the vacuum state of the vacuum vessel 10. In addition, the surface roughness, contour shape, and the like of the upper electrode 12 can be calculated from the measured three-dimensional shape.

Further, by rotating the holding shaft 40 by 180 °, the surface of the lower electrode 14 facing the upper electrode 12 can also be measured. The measuring device 100-1 can also measure the surfaces of the focus rings 20 and 22.

When the plasma CVD apparatus 1-1 is operated, the holding shaft 40 is retracted from the processing space of the vacuum vessel 10, but a lid is provided at the tip of the holding shaft 40 (in front of the prism mirror 44) to provide the holding shaft 40. It is preferable that the opening 10A of the vacuum vessel 10 is closed with the lid during the evacuation period.

[Second Embodiment of Measuring Device]
FIG. 2 is a configuration diagram showing a second embodiment of the measuring device according to the present invention.

The measuring device 100-2 of the second embodiment shown in FIG. 2 is applied to the plasma CVD device 1-2.

The plasma CVD apparatus 1-2 has substantially the same configuration as the plasma CVD apparatus 1-1 shown in FIG. In the plasma CVD apparatus 1-2 shown in FIG. 2, the same reference numerals are given to the parts common to the plasma CVD apparatus 1-1 shown in FIG. 1, and detailed description thereof will be omitted.

The plasma CVD apparatus 1-2 shown in FIG. 2 differs from the plasma CVD apparatus 1-1 shown in FIG. 1 in that a window portion 32 mainly made of a partition glass (first transparent member) is provided.

The window portion 32 is used as a window portion for transmitting the measurement light emitted from the beam splitter and causing it to enter the inside of the vacuum vessel 10. Further, as the window portion 32, one provided for photographing or visually observing the inside of the vacuum container 10 can be used.

The measuring device 100-2 shown in FIG. 2 includes a measuring device main body 50 having a built-in white interference optical system and the like, a holding shaft (bending optical member holding shaft) 46A, a bellows 46B functioning as an airtight means, and a moving stage 60-. It is composed of 1 and 1.

The bellows 46B functions as an airtight means for maintaining the airtightness between the opening 10A of the vacuum vessel 10 and the holding shaft 46A and making the holding shaft 46A movable in the X-axis direction. The holding shaft 46A and the bellows 46B form a feedthrough bellows rod 46.

A prism mirror 44 is arranged at the tip of the holding shaft 46A, and the measurement light emitted from the measuring device main body 50 in the X-axis direction passes through the window portion 32 and is incident on the prism mirror 44. Is bent in a direction orthogonal to the X-axis direction (in this example, the Z-axis direction). That is, the prism mirror 44 bends the measurement light in the X-axis direction emitted from the measuring device main body 50 in the Z-axis direction and causes it to enter the surface of the upper electrode 12.

The moving stage 60-1 is an X stage that moves the stage on which the measuring device main body 50 and the holding shaft 46A are mounted in the X-axis direction, and includes a stage driving unit including a motor 62A and the like for moving the stage.

FIG. 3 is a diagram showing a main part of the measuring device main body 50 incorporating the white interference optical system and the like of the measuring device 100-2 shown in FIG.

The white interference optical system of this example includes a beam splitter (light splitting means) 52, a prism mirror 54, and a reference mirror (reference light reflector) 56.

White light emitted from the light source is incident on the measuring device main body 50 via the input unit 51A. The incident white light is magnified and parallelized by the telecentric lens arranged in the lens barrel 51B, and is emitted through the objective lens.

The white light emitted from the objective lens is incident on the beam splitter 52, where it is split into measurement light traveling in the X-axis direction and reference light traveling in the Z-axis direction.

The measurement light in the X-axis direction emitted from the beam splitter 52 passes through the window portion 32 provided in the vacuum vessel 10 and enters the prism mirror 44, and is bent in the Z-axis direction by the prism mirror 44 to be bent in the Z-axis direction to the upper electrode 12. (See FIG. 2).

On the other hand, the reference light emitted from the beam splitter 52 in the Z-axis direction is bent in the X-axis direction by the prism mirror 54 and enters the reference mirror 56.

The return light of the measurement light reflected on the surface of the upper electrode 12 enters the beam splitter 52 via the prism mirror 44 and the window 32, and the return light of the reference light reflected by the reference mirror 56 passes through the prism mirror 54. It enters the beam splitter 52 via the beam splitter 52.

The beam splitter 52 also functions as an optical interference means for interfering the return light of the measurement light reflected on the surface of the upper electrode 12 and the return light of the reference light reflected by the reference mirror 56 together. The interference light between the measurement light and the reference light is incident on the light receiving surface of the image pickup element (light detection means) arranged at the rear end 51C of the lens barrel 51B via the objective lens and the telecentric lens in the lens barrel 51B. Then, it is converted into an electric signal according to the intensity of the interference light.

In addition, parallel interference light having a cross section of a size corresponding to the image pickup surface is incident on the light receiving surface (imaging surface) of the image pickup element by a telecentric lens, and the image pickup element captures the interference light as two-dimensional interference fringes. can do.

FIG. 4 is a diagram mainly showing an embodiment of the moving stage 60-1 shown in FIG.

The moving stage 60-1 shown in FIG. 4 is composed of a stage (table) 61 and a stage driving unit 62 having a motor 62A and a ball screw 62B.

A measuring device main body 50 and a holding shaft 46A (see FIG. 2) are mounted on the stage 61, and a nut 61A screwed with the ball screw 62B is provided.

The drive shaft of the motor 62A is connected to the ball screw 62B, and the stage drive unit 62 transmits a linear driving force to the stage 61 via the ball screw 62B and the nut 61A by rotating the motor 62A forward or reverse. , The stage 61 is moved in the X-axis direction.

The moving stage 60-1 is provided with a guide rail that guides the stage 61 so as to be movable in the X-axis direction, and detects the moving position (moving position in the X-axis direction) of the stage 61, which is not shown. A one-position detector (first position detection means) is provided. The first position detector can be composed of, for example, a scale head provided on the stage 61 and a linear scale provided on the guide rail side of the stage 61, and the scale head moves on the linear scale as the stage 61 moves. By reading the position information, the moving position of the stage 61 is detected.

Returning to FIG. 3, the measuring device main body 50 is provided with a piezo element 57 for moving the reference mirror 56 in the X-axis direction. The piezo element 57 moves the reference mirror 56 in the X-axis direction with respect to the stage 61 of the moving stage 60-1 (independent of the movement of the stage 61 in the X-axis direction) to change the optical path length of the reference light. It functions as a means for changing the reference optical path length.

The second position detector (second position detecting means) 58 detects the position (displacement amount from the reference position) of the reference mirror 56 in the X-axis direction. The amount of displacement detected by the second position detector 58 corresponds to the shape of the surface of the upper electrode 12 at the measurement position (the amount of unevenness of the surface of the upper electrode 12 with respect to the reference surface) as described later.

The reference optical path length changing means is not limited to the piezo element 57, and the reference mirror 56 may be moved by a motor or the like, and may be any one that changes the position of the reference mirror 56.

FIG. 5 is a diagram used to explain the white interference conditions of the white interference optical system of the measuring device 100-2 shown in FIG.

As shown in FIG. 1, the distance (first distance) in the X-axis direction from the beam splitter 52, which is the optical path of the measurement light, to the prism mirror 44 is X1, and the distance from the prism mirror 44 to the surface (reference plane) of the measurement object. The distance in the Z-axis direction is Z1, while the distance in the Z-axis direction from the beam splitter 52, which is the optical path of the reference light, to the prism mirror 54 is Z2, and the distance in the X-axis direction from the prism mirror 54 to the reference mirror 56 is X2. Then, the following equation,
[Number 1]
X1 + Z1 = X2 + Z2
When the above conditions are satisfied, the intensity of the interference light detected by the image sensor 80 becomes maximum.

When the white interference condition shown in the equation [Equation 1] is satisfied, the intensity of the interference light between the measurement light reflected on the surface of the measurement object located at the distance Z1 from the prism mirror 44 and the reference light reflected by the reference mirror 56 is Become the maximum.

The distance X1 is preferably a distance longer than the length of the surface of the object to be measured in the X-axis direction. This is because the measurement light is incident on the surface of the measurement object from one end to the other end in the X-axis direction of the surface of the measurement object. When the upper electrode 12 and the focus ring 20 shown in FIG. 2 are the objects to be measured, the distance X1 is set to be longer than the outer diameter of the focus ring 20.

Further, the reference mirror 56 is scanned in the X-axis direction in order to search for the position where the intensity of the interference light is maximized, and the distance X2 is the position at the center of the scanning range in the X-axis direction of the reference mirror 56 (hereinafter referred to as “the reference mirror 56”). This is the distance in the X-axis direction between the prism mirror 54 and the reference mirror 56 when the reference mirror 56 is located at the “reference position”).

<Measurement principle>
Next, the measurement principle for measuring the surface shape of the object to be measured will be described.

FIG. 6 is a diagram used to explain the measurement principle of the measuring device having the white interference optical system.

FIG. 6A is a schematic view of the white interference optical system.

As shown in FIG. 6A, the light source 70 composed of a white light emitting diode or the like emits white light in the X-axis direction. The white light emitted from the light source 70 is reflected by the beam splitter 72 in the Z-axis direction and is incident on the objective lens group 76.

The objective lens group 76 is composed of an objective lens 74, a reference mirror 56', and a beam splitter (half mirror) 52', and is movable in the Z-axis direction. The reference mirror 56'and the beam splitter 52'play the same roles as the reference mirror 56 and the beam splitter 52 shown in FIG.

The white light collected by the objective lens 74 is split into a measurement light and a reference light by the beam splitter 52', and the measurement light transmitted through the beam splitter 52'is incident on the surface of the measurement object 78, and the beam splitter 52 The reference light reflected by'is incident on the reference mirror 56'.

The return light of the measurement light reflected on the surface of the object to be measured 78 and the return light of the reference light reflected by the reference mirror 56'are combined by the beam splitter 52', and are objectively used as interference light between the measurement light and the reference light. It is incident on the light receiving surface of the image pickup element 80 via the lens 74 and the beam splitter 72.

FIG. 6B is a perspective view showing a light receiving surface (imaging surface) of the image sensor 80.

The image pickup device 80 is a CCD (Charge Coupled Device) type or CMOS (Complementary Metal-Oxide Semiconductor) type image sensor, and has an image pickup surface formed by arranging light receiving elements (pixels) in a matrix.

When the interference light (interference fringe) is photographed by the image sensor 80 while scanning the objective lens group 76 in the Z-axis direction, the interference fringe changes according to the distance between the measurement object 78 and the objective lens group 76. .. When the image sensor 80 is a color image sensor, the hue actually changes.

Therefore, by reading the position of the objective lens group 76 when the brightness (intensity of interference light) detected by each pixel of the image sensor 80 is maximum for each pixel, the surface of the object to be measured 78 is in the Z-axis direction. The height can be measured.

FIG. 6C is a diagram showing an example of interference light received by each pixel of the image sensor 80.

Now, the distance between the measurement object 78 and the objective lens group 76 is the position in the Z-axis direction of the objective lens group 76 in the case shown in FIG. 6A as a reference position (Z = 0), and the measurement object is measured. Assuming that the position of the reference plane of 78 is zero, the amplitude of the interference wave (interferogram) is objective as shown in FIG. 6 (C) in the portion where the surface of the object to be measured 78 is higher or lower than the reference plane. The position of the lens group 76 is maximized at a position shifted in the positive or negative direction from the reference position.

Therefore, by scanning the objective lens group 76 and detecting the position of the objective lens group 76 in the Z-axis direction when the brightness is maximum for each pixel of the image sensor 80, the position of the objective lens group 76 in the Z-axis direction is detected with respect to the reference surface of the surface of the measurement object 78. The height (concavo-convex shape) can be measured.

Further, since the image sensor 80 can capture the interference light as two-dimensional interference fringes, it is possible to measure the three-dimensional shape of the surface of the measurement object 78 having a constant field of view in which the measurement light is incident.

FIG. 7 is a block diagram of a main part of the measuring device 100-2 shown in FIG.

In FIG. 7, the moving stage 60-1 shown in FIG. 4 drives the motor 62A of the stage driving unit 62 by a drive command applied from the stage control unit 63 to move the stage 61 in the X-axis direction.

The stage control unit 63 preferably controls the moving position of the stage 61 so that the measurement light is incident on the surface of the measurement object from one end to the other end in the X-axis direction of the surface of the measurement object. Further, the three-dimensional shape of the surface of the measurement object 78 having a constant field of view can be measured without moving the stage 61. Therefore, when measuring the three-dimensional shape of the object to be measured over the entire length in the X-axis direction of the object to be measured, the stage 61 is intermittently moved at a predetermined pitch so that a part of the field of view overlaps, and the moving position. It is preferable to measure the three-dimensional shape every time.

The moving position of the stage 61 in the X-axis direction is detected by the first position detector (first position detecting means) 64. The position detection signal indicating the position of the stage 61 detected by the first position detector 64 is output to the surface measuring unit (measuring means) 92.

The reference mirror 56 is driven by the piezo element 57 in the X-axis direction within a constant scanning range centered on the reference position. As a result, the optical path length of the reference light changes within a certain scanning range.

The moving position of the reference mirror 56 in the X-axis direction is detected by the second position detector 58. The position detection signal indicating the position of the reference mirror 56 in the X-axis direction detected by the second position detector 58 is output to the third position detector (third position detecting means) 90.

An image signal indicating interference fringes (a signal indicating the intensity of interference light for each pixel) captured by the image sensor 80 is added to the other inputs of the third position detector 90, and the third position detector 90 Detects (extracts) a position detection signal indicating the moving position of the reference mirror 56 in the X-axis direction when the brightness (intensity of interference light) is maximized for each pixel of the image sensor 80, and detects the detected position. The signal is output to the surface measuring unit 92.

The surface measuring unit 92 is based on a position detection signal indicating the moving position of the stage 61 detected by the first position detector 64 and a position detecting signal indicating the position of the reference mirror 56 detected by the third position detector 90. Then, the surface of the object to be measured is measured at a position in the X-axis direction of the surface of the object to be measured.

That is, the surface measuring unit 92 is the position in the X-axis direction of the reference mirror 56 detected by the third position detector 90 (the reference mirror 56 detected for each pixel of the image pickup element 80 when the brightness becomes maximum). Based on the position in the X-axis direction), the amount of displacement of the surface of the object to be measured with respect to the height of the reference plane is obtained.

Now, assuming that the height of the reference surface of the surface of the object to be measured is Z = 0, the surface measuring unit 92 obtains the displacement amount ΔZ. The displacement amount ΔZ corresponds to the amount of movement of the reference mirror 56 from the reference position. Further, the surface measuring unit 92 obtains the displacement amount ΔZ for each pixel of the image pickup device 80. As a result, the surface measuring unit 92 can measure the three-dimensional shape of the surface of the object to be measured in the visual field (irradiation region of the measurement light) set by the objective lens or the like.

Further, the field of view set by the objective lens or the like can be moved in the X-axis direction by the moving stage 60-1.

Therefore, when the visual field is moved from one end to the other end of the surface of the object to be measured in the X-axis direction by the moving stage 60-1, the surface measuring unit 92 measures the entire surface of the surface of the object to be measured in the X-axis direction. be able to.

Further, when the surface measuring unit 92 measures the three-dimensional shape of the surface of the object to be measured, the surface roughness, the contour shape and the like can be further measured from the measurement result.

FIG. 8 is a configuration diagram of a main part showing a modified example of the measuring device shown in FIG. 2 and the like. In FIG. 8, the parts common to the moving stage 60-1 shown in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the moving stage 60-2 of the measuring device shown in FIG. 8, the precision moving stage 59 is mainly installed on the stage 61, and the measuring device main body 50 is mounted on the precision moving stage 59. Different from stage 60-1.

That is, the precision moving stage 59 is equipped with a measuring device main body 50 including at least a beam splitter 52 and a reference mirror 56, and the precision moving stage 59 minutely moves the measuring device main body 50 in the X-axis direction. The holding shaft 40 for holding the prism mirror 44 is mounted on the stage 61.

Therefore, the precision moving stage 59 functions as a measuring optical path length changing means for changing the optical path length of the measuring light by moving the measuring device main body 50 in the X-axis direction.

The second position detector 58'(FIG. 9) detects the position (displacement amount from the reference position) of the measuring device main body 50 with respect to the stage 61 in the X-axis direction.

FIG. 9 is a main block diagram showing a modified example of the measuring device including the moving stage 60-2 shown in FIG. In FIG. 9, the same reference numerals are given to the parts common to the measuring device shown in FIG. 7, and detailed description thereof will be omitted.

The measuring device shown in FIG. 9 differs from the measuring device shown in FIG. 7 in that the position of the measuring device main body 50 moved by the precision moving stage 59 is detected by the second position detector 58'.

That is, the measuring device shown in FIG. 7 has a reference optical path length changing means for finely moving the reference mirror 56 by the piezo element 57 and changing the optical path length of the reference light with respect to the optical path length of the measurement light. In the measuring device shown in FIG. 9, the measuring device main body 50 (at least the beam splitter 52 and the reference mirror 56) is slightly moved by the precision moving stage 59, and the optical path length of the measurement light is changed with respect to the optical path length of the reference light. It has a means for changing the optical path length.

Instead of changing the optical path length of the reference light, the white interference condition of the white interference optical system can be changed by changing the optical path length of the measurement light.

The position detection signal indicating the position of the measuring device main body 50 in the X-axis direction detected by the second position detector 58'is output to the third position detector 90.

An image signal indicating interference fringes taken by the image sensor 80 is added to the other inputs of the third position detector 90, and the third position detector 90 has a brightness for each pixel of the image sensor 80. A position detection signal indicating a moving position of the measuring device main body 50 in the X-axis direction at the maximum is detected (extracted), and the detected position detection signal is output to the surface measuring unit 92.

Since the method of measuring the three-dimensional shape of the surface of the object to be measured by the surface measuring unit 92 is the same as that of the measuring device shown in FIG. 7, the description thereof will be omitted.

In the modified example of the measuring device shown in FIG. 8, the measuring device main body 50 is mounted on the precision moving stage 59, and the measuring device main body 50 is slightly moved with respect to the stage 61, but the present invention is not limited to this. The holding shaft 46A for holding the prism mirror 44 may be mounted on the precision moving stage 59, and the precision moving stage 59 may be slightly moved with respect to the stage 61 so that the optical path length of the measurement light can be changed. Further, when the holding shaft 46A is mounted on the precision moving stage 59, it goes without saying that the second position detector 58'detects the moving position of the holding shaft 46A with respect to the stage 61.

FIG. 10 is a diagram showing a modified example of the white interference optical system of the measuring device shown in FIG.

A modification of the white interference optical system shown in FIG. 10 is a modification of the white interference optical system shown in FIG. 3 in that an adjusting glass (second transparent member) 55 is provided between the prism mirror 54 and the reference mirror 56. Different from the system.

The adjusting glass 55 has the same refractive index and plate thickness as the partition glass (first optical member) provided in the window portion 32 of the vacuum vessel 10.

As a result, since the measurement light and the reference light pass through the same optical member (partition glass, adjustment glass), the same measurement result as when the partition glass does not exist can be obtained.

<Other embodiments of the moving stage>
FIG. 11 is a diagram mainly showing another embodiment of the moving stage.

The moving stage 60-3 shown in FIG. 11 is an XY stage that moves the stage 61 on which the measuring device main body 50 and the like are mounted in the X-axis direction and the Y-axis direction.

The moving stage 60-3 is an XY stage that further moves the X stage configured in the same manner as the moving stage 60-1 shown in FIG. 4 in the Y-axis direction.

The moving stage 60-3 further moves the X stage, which moves the stage 61 in the X-axis direction, in the Y-axis direction by the stage drive unit 65 having the motor 65A and the ball screw 65B.

In FIG. 11, 64-1 is a first position detector that detects the position of the stage 61 in the X-axis direction, and 64-2 is a first position detector that detects the position of the stage 61 in the Y-axis direction. It is a vessel 64-2. These first position detectors 64-1 and 64-2 are composed of a scale head and a linear scale that move relative to each other, and scale as the stage 61 moves in the X-axis direction and / or the Y-axis direction. By reading the position information of the linear scale with the head, the moving position of the stage 61 in the X-axis direction and / or the Y-axis direction is detected.

According to the moving stage 60-3 having the above configuration, the stage 61 can be moved to an arbitrary position in the XY plane, whereby the visual field (irradiation region of the measurement light) corresponding to the position of the prism mirror 44 is also moved to the XY plane. It can be moved to any position within.

In FIG. 11, 78A shows a measurement area on the surface of the object to be measured. The measurement area 78A is preferably set so as to include the entire surface of the object to be measured. According to this, the measurement light can be incident on the entire surface of the object to be measured, and the surface roughness, the contour shape, etc. of the entire surface of the object to be measured can be measured.

When the moving stage 60-3 shown in FIG. 11 is used, the window portion for transmitting the measurement light needs to be long in the Y-axis direction corresponding to the amount of movement of the stage 61 in the Y-axis direction. Similarly, the opening between the holding shaft holding the prism mirror 44 and the vacuum vessel 10 and the airtight means thereof also need to be long in the Y-axis direction.

[others]
In the present embodiment, the measuring device applied to the vacuum vessel of the plasma CVD apparatus has been described, but the measuring apparatus according to the present invention is not limited to this, and can be applied to, for example, the vacuum vessel of the plasma etching apparatus. It can be applied to any vacuum container as long as the performance of the device changes as the components in the vacuum container wear out or a film is formed with the operating time of the device.

The object to be measured in the vacuum vessel is not limited to the upper electrode, the lower electrode, and the focus ring, but is a component provided inside the vacuum vessel and having a surface for measuring surface roughness and the like at least. All you need is.

Further, the moving stage moves the stage in the X-axis direction, or the X-axis direction and the Y-axis direction with respect to a component having a surface parallel to the XY plane of the XYZ coordinate system, but the axial direction and the stage of the XYZ coordinate system. It does not have to completely match the moving direction of, for example, it is sufficient that the maximum interference light can be obtained when the reference mirror (reference light reflector) is scanned in a certain scanning range.

Furthermore, the measuring device is not limited to measuring the entire surface of the object to be measured in the X-axis direction or the surface of the object to be measured in the X-axis direction and the Y-axis direction without gaps, and may also measure discretely. good.

Further, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

1-1, 1-2 Plasma CVD device 10 Vacuum vessel 10A Aperture 12 Upper electrode 12A Depot film 14 Lower electrode 16, 18 Vertical drive unit 20, 22 Focus ring 30 High frequency power supply 32 Window 40 Holding shaft 42 Airtight member 43, 74 Objective lens 44 Prism mirror 46 Feed-through bellows rod 46A Holding shaft 46B Bellows 50 Measuring device body 51A Input unit 51B Lens lens barrel 51C Rear end 52, 52', 72 Beam splitter 54 Prism mirror 55 Adjusting glass 56, 56' Reference mirror 57 Piezo element 58, 58'Second position detector 59 Precision moving stage 60-1, 60-2 Moving stage 61 Stage 61A Nut 62, 65 Stage drive unit 62A, 65A Motor 62B, 65B Ball screw 63 Stage control unit 64, 64-1, 64-2 1st position detector 70 Light source 76 Objective lens group 78 Measurement target 78A Measurement area 80 Imaging element 90 3rd position detector 92 Surface measurement unit 100-1, 100-2 Measuring device

Claims (13)

A measuring device provided inside a vacuum vessel and having a surface parallel to the XY plane of the XYZ coordinate system as a measurement object, and measuring the surface of the measurement object in a non-contact manner.
A light source that emits low coherence light and
An optical dividing means for dividing the low coherence light emitted from the light source into measurement light and reference light, and
Assuming that the emission direction of the measurement light from the optical dividing means is the X-axis direction, the measurement light is directed in a direction orthogonal to the X-axis direction at a position in the X-axis direction separated from the optical dividing means by a first distance. Bending optical member to bend and
A bending optical member holding shaft that holds the bending optical member at the tip portion and arranges the bending optical member inside the vacuum container through an opening formed in the vacuum container.
An airtight means for maintaining airtightness between the opening and the bending optical member holding shaft and allowing the bending optical member holding shaft to move in the X-axis direction.
A reference light reflector that reflects the reference light emitted from the light dividing means, and
A moving stage for moving at least the light dividing means, the bending optical member holding shaft, and the stage on which the reference light reflector is mounted in the X-axis direction.
The first position detecting means for detecting the moving position of the stage and
A reference optical path length changing means for moving the reference light reflector with respect to the stage to change the optical path length of the reference light, and
A second position detecting means for detecting the position of the reference light reflector, and
An optical interference means that causes the measurement light reflected by the measurement object and the reference light reflected by the reference light reflector to interfere with each other.
A photodetecting means that receives interference light between the measurement light and the reference light,
A third position detecting means for detecting the position of the reference light reflector when the intensity of the interfering light detected by the light detecting means is maximized, and
Based on the moving position of the stage detected by the first position detecting means and the position of the reference light reflector detected by the third position detecting means, in the X-axis direction of the surface of the object to be measured. A measuring means for measuring the surface of the object to be measured at a position,
A measuring device equipped with. A measuring device provided inside a vacuum vessel and having a surface parallel to the XY plane of the XYZ coordinate system as a measurement object, and measuring the surface of the measurement object in a non-contact manner.
A light source that emits low coherence light and
An optical dividing means for dividing the low coherence light emitted from the light source into measurement light and reference light, and
Assuming that the emission direction of the measurement light from the optical dividing means is the X-axis direction, the measurement light is directed in a direction orthogonal to the X-axis direction at a position in the X-axis direction separated from the optical dividing means by a first distance. Bending optical member to bend and
A bending optical member holding shaft that holds the bending optical member at the tip portion and arranges the bending optical member inside the vacuum container through an opening formed in the vacuum container.
An airtight means for maintaining airtightness between the opening and the bending optical member holding shaft and allowing the bending optical member holding shaft to move in the X-axis direction.
A reference light reflector that reflects the reference light emitted from the light dividing means, and
A moving stage for moving at least the light dividing means, the bending optical member holding shaft, and the stage on which the reference light reflector is mounted in the X-axis direction.
The first position detecting means for detecting the moving position of the stage and
A measuring device main body or the bending optical member holding shaft, which is installed on the stage and includes at least the light dividing means and the reference light reflector, is mounted, and the measuring device main body or the bending optical member holding shaft is mounted on the X axis. A precision movement stage that moves minutely in the direction,
A second position detecting means for detecting the moving position of the measuring device main body or the bending optical member holding shaft by the precision moving stage, and
An optical interference means that causes the measurement light reflected by the measurement object and the reference light reflected by the reference light reflector to interfere with each other.
A photodetecting means that receives interference light between the measurement light and the reference light,
A third position detecting means for detecting the position of the measuring device main body or the bending optical member holding shaft when the intensity of the interference light detected by the photodetecting means is maximized.
The surface of the object to be measured based on the moving position of the stage detected by the first position detecting means and the position of the measuring device main body or the bending optical member holding shaft detected by the third position detecting means. A measuring means for measuring the surface of the object to be measured at the position in the X-axis direction of the above.
A measuring device equipped with. The light detection means is an image pickup device having an image pickup surface formed by arranging light receiving elements in a matrix.
The interference light incident on the imaging surface has a cross section having a size corresponding to the imaging surface.
The third position detecting means detects the position of the reference light reflector when the intensity of the interference light is maximized for each light receiving element.
The measuring means measures the surface of the object to be measured based on the position of the reference light reflector detected for each light receiving element.
The measuring device according to claim 1. The light detection means is an image pickup device having an image pickup surface formed by arranging light receiving elements in a matrix.
The interference light incident on the imaging surface has a cross section having a size corresponding to the imaging surface.
The second position detecting means detects the position of the measuring device main body or the bending optical member holding shaft when the intensity of the interference light is maximized for each light receiving element.
The measuring means measures the surface of the object to be measured based on the position of the measuring device main body or the bending optical member holding shaft detected for each light receiving element.
The measuring device according to claim 2. The airtight means is a feedthrough bellows rod, an O-ring, a ferrofluid, or a magnet ring.
The measuring device according to any one of claims 1 to 4. The measuring device according to any one of claims 1 to 5, wherein the measuring means measures at least one of the surface roughness and the contour shape of the object to be measured. The first distance is a distance longer than the length of the surface of the measurement object in the X-axis direction.
The measuring device according to any one of claims 1 to 6. A stage control unit for moving the stage in the X-axis direction and causing the measurement light to enter the surface of the measurement object from one end to the other end in the X-axis direction of the surface of the measurement object is further provided.
The measuring means measures the entire surface of the object to be measured in the X-axis direction.
The measuring device according to claim 7. The moving stage is an XY stage that moves at least a stage equipped with the light dividing means, the bending optical member holding shaft, and the reference light reflector in the X-axis direction and the Y-axis direction of the XYZ coordinate system, respectively.
The stage control unit moves the stage in the X-axis direction and the Y-axis direction, respectively, and causes the measurement light to be incident on the entire surface of the measurement object.
The measuring means measures the entire surface of the object to be measured.
The measuring device according to claim 8. The measurement light emitted from the light dividing means passes through the opening and is incident on the bending optical member.
The measuring device according to any one of claims 1 to 9. A rotating means for rotating the bending optical member holding shaft about the optical axis of the measurement light emitted from the optical dividing means toward the bending optical member is further provided.
The measuring device according to claim 10. The measurement light emitted from the light dividing means passes through a window portion made of a first transparent member provided in the vacuum container and is incident on the bending optical member.
The measuring device according to any one of claims 1 to 9. A second transparent member arranged between the light dividing means and the reference light reflector and having the same refractive index and thickness as the first transparent member is provided.
The measuring device according to claim 12.

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