JP4968721B2 - Flatness measuring device calibration reference plate - Google Patents

Description

  The present invention relates to a flatness measuring device calibration reference for calibrating a measurement region when measuring the flatness of a substrate surface such as a glass substrate for a photomask blank used for manufacturing an electronic device by a flatness measuring device. Regarding plates.

  With recent rapid development of IT technology, further miniaturization is required for recent electronic devices, particularly color filters or TFT elements for semiconductor elements and liquid crystal monitors. One of the technologies that support such a fine processing technology is a lithography technology using a photomask called a transfer mask. In this lithography technique, a fine pattern is formed on a silicon wafer by exposing an electromagnetic wave or light wave of an exposure light source to a silicon wafer with a resist film through a photomask. This photomask usually forms a thin film pattern (mask pattern) to be a transfer pattern by patterning the thin film using a lithography technique on a mask blank in which a thin film such as a light-shielding film is formed on a translucent substrate. Manufactured.

  By the way, in order to achieve the miniaturization of the pattern of the electronic device, it is also extremely important to improve the quality of the mask blank that is an original for manufacturing the photomask. Conventionally, the main surface of the glass substrate for mask blank has been polished so as to have a predetermined mirror surface, and thus the main surface of the glass substrate has been finished so as to obtain good smoothness.

Further, when miniaturizing an electronic device pattern, it is necessary to shorten the wavelength of an exposure light source used in photolithography in addition to miniaturization of a mask pattern formed on a photomask. For example, as an exposure light source in manufacturing a semiconductor device, in recent years, the wavelength has been shortened from a KrF excimer laser (wavelength 248 nm) to an ArF excimer laser (wavelength 193 nm) and further to an F2 excimer laser (wavelength 157 nm). However, when the exposure light source wavelength is 200 nm or less, the depth of focus of the exposure apparatus becomes very small. For this reason, if the flatness of the main surface of the substrate is poor, the focus position may be shifted when the mask pattern of the exposure mask is transferred to the semiconductor substrate, which is a transfer target, and transfer accuracy may be reduced. Therefore, in order to achieve pattern miniaturization, it is desired that the smoothness of the main surface of the substrate is good and the flatness of the substrate is also good.
Therefore, conventionally, the flatness of the main surface of the substrate has also been measured and managed using, for example, a flatness measuring device using optical interference (see Patent Document 1).

JP-A-5-241322

  When measuring the flatness of the main surface of the substrate using, for example, a flatness measuring device using optical interference, specifically, reference planes at a plurality of measurement points in the main surface (calculated by the method of least squares). Height information from the focal plane) is obtained, a maximum value and a minimum value are obtained from the height information, and a difference between the maximum value and the minimum value, that is, flatness is calculated.

Considering the above-mentioned pattern miniaturization and shortening of the exposure light source wavelength, the flatness of the substrate is required to be about 0.2 to 0.4 μm. Therefore, the measurement of flatness requires a minimum measurement accuracy of about 0.01 to 0.02 μm. In order to measure the flatness with high accuracy, it is desirable to increase the number of measurement points for acquiring the height information as much as possible, and the measurement area for acquiring the height information is as much as possible on the entire main surface of the substrate. Is desirable.
However, in the case of an existing flatness measuring device using optical interference, the substrate surface drastically droops in the outer periphery of the substrate, that is, in the vicinity of the boundary between the main surface of the substrate and the end surface formed on the periphery of the main surface. Therefore, it is difficult to measure the height information with high accuracy. On the other hand, in recent years, when the substrate is vacuum chucked to an exposure apparatus that transfers the pattern to the semiconductor substrate simultaneously with the miniaturization of the mask pattern, depending on the surface shape and flatness of the region where the substrate abuts, Since the flatness of the substrate changes, it is required to guarantee the flatness in the region on the main surface including the range as close to the outer peripheral portion as possible. For example, in the case of a substrate having a size of 152 mm × 152 mm (6 inch square), it is usually required to ensure flatness in a region having a size of 146 mm (or 150 mm) × 146 mm (or 150 mm).

  When high-precision measurement is performed using a flatness measurement device that uses existing optical interference, data on the height information of the periphery of the substrate where the substrate surface is drastically cannot be acquired, and the same size substrate Even so, the actual measurement region where the data exists changes depending on the flatness shape of the surface. Therefore, when flatness measurement is performed using a flatness measuring device that uses existing optical interference, up to which area of the substrate data can be acquired, and where the actual measurement area is, particularly as described above, the substrate In order to guarantee the flatness up to the peripheral part, it is necessary to accurately grasp the actually measured region of the peripheral part of the substrate.

  However, when the existing flatness measuring device using optical interference is used, the measured substrate size and the measurement result (area where data exists) cannot be correlated 1: 1, and the flatness measuring device. The accuracy of the measurement area is insufficient, and it is difficult to immediately specify the actual measurement area where the data exists on the substrate from the measurement result. For this reason, conventionally, for the sake of convenience, the pixel size of data is determined based on the optical design value, and the measurement region of the flatness measuring device is calibrated. However, such a conventional method includes various errors due to the calibration based on the optical design value, and may be slightly different from the actual measurement. It is difficult to accurately grasp the actual measurement area.

  The present invention has been made to solve the above-described problems, and its purpose is to calibrate the measurement area when the flatness of the substrate surface is measured by the flatness measurement apparatus, and to accurately determine the actual measurement area of the flatness measurement apparatus. It is to provide a reference plate for flatness measuring device calibration that can be evaluated.

In order to solve the above-mentioned problems, the present invention has the following configuration.
(Configuration 1) Flatness measuring device calibration reference for acquiring height information from a reference surface on a substrate surface by a flatness measuring device and calibrating a measurement region when measuring the flatness of the substrate surface. A flat plate for measuring a flatness measuring device, characterized in that it has a boundary line on the plate that defines a predetermined region having a step from the surface of the plate.
(Structure 2) The flatness measuring apparatus calibration reference plate according to Structure 1, wherein the predetermined area is a square or circular area substantially centered on the center of the plate surface.
(Structure 3) The flatness measuring device calibration reference plate according to Structure 1 or 2, wherein a boundary line defining a plurality of regions is formed on the plate.
(Configuration 4) The flatness measuring apparatus calibration reference plate according to any one of Configurations 1 to 3, wherein the substrate is a glass substrate for a photomask blank.
(Structure 5) The flatness measuring apparatus calibration according to any one of Structures 1 to 4, wherein the flatness measuring apparatus calibration reference plate is formed by forming a metal thin film pattern on a glass substrate surface. This is a reference plate for use.
(Structure 6) The flatness measuring apparatus calibration reference plate according to any one of Structures 1 to 5, wherein the flatness measuring apparatus is a flatness measuring apparatus using light interference.

As in Configuration 1, the present invention acquires height information from a certain reference surface on a substrate surface by a flatness measuring device, and calibrates a measurement region when measuring the flatness of the substrate surface. The flatness measuring device calibration reference plate is characterized in that it has a boundary line defining a predetermined region having a step difference from the plate surface on the plate.
By measuring the flatness of the surface of the flatness measuring apparatus calibration reference plate (hereinafter simply referred to as “reference plate”) according to Configuration 1 using an existing flatness measuring apparatus, The size of the one pixel on the reference plate can be determined. Then, the flatness of the actual substrate surface is measured using the flatness measuring device, and the substrate is obtained from the measurement result (area where the actual measurement data exists) and the size of one pixel determined using the reference plate. The actual measurement area where the above data exists can be specifically determined. That is, when the flatness of the substrate surface is measured using an existing flatness measuring device using, for example, optical interference, the pixel size of the data is determined based on the actual measurement result of the reference plate of the present invention, Since the actual measurement area on the substrate can be specified, it is possible to accurately evaluate the actual measurement area in the peripheral portion of the substrate, by acquiring data up to which area on the substrate. This also makes it possible to guarantee flatness in a region including the periphery of the substrate.

  Further, as in Configuration 2, the predetermined region on the reference plate is preferably a square or circular region having the center of the plate surface as a center. As a result, the pixel size of the data can be determined easily and accurately based on the actual measurement result of the reference plate. In addition, it is easy to correspond to the substrate to be measured, and the reliability of the calibrated actual measurement region is high.

  Further, as in Configuration 3, it is preferable that the reference plate has a boundary line that defines a plurality of regions. For example, in the case of a flatness measuring device using optical interference, the magnification may be different between the central portion and the peripheral portion of the measurement result (that is, the size of one pixel is different), so a boundary line that defines a plurality of regions should be provided. Thus, the linearity of the magnification can be confirmed from the measurement result, and the measurement area can be calibrated with higher accuracy.

  Further, as described in Configuration 4, when the substrate is a glass substrate for a photomask blank, the reference plate of the present invention is suitable. This is because in the case of a glass substrate for a photomask blank, the flatness of the substrate surface greatly affects the pattern transfer accuracy, and thus the demand for flatness required for the substrate is severe.

  Moreover, as in the configuration 5, the reference plate of the present invention is formed by forming a metal thin film pattern on the surface of the glass substrate. Such a reference plate can be obtained by forming a metal thin film on a glass substrate and patterning the metal thin film using a photolithography method to form a predetermined metal thin film pattern. In this way, a reference plate with excellent pattern accuracy can be obtained, so that highly accurate calibration can be performed.

  Further, as described in Configuration 6, when the flatness measuring device is a flatness measuring device using light interference, the reference plate of the present invention is suitable. Flatness measuring devices using optical interference are often used for flatness measurement where high accuracy is required, such as glass substrates for photomask blanks, and the demand for flatness is severe for photomask blank substrates. The reference plate of the present invention is preferred.

  According to the present invention, it is possible to calibrate the measurement region when the flatness of the substrate surface is measured by the flatness measuring device, and to accurately evaluate the range of the actually measured region that can be actually measured by the flatness measuring device. The flatness measuring device calibration reference plate can be provided.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view of an embodiment of a reference plate according to the present invention.
According to FIG. 1, the reference plate 20 of the present embodiment has a plurality of boundary lines that define a predetermined area on a plate 1 (size 152 mm × 152 mm) made of, for example, a square glass plate. It will be. In other words, in the present embodiment, the plurality of boundary lines are, in order from the side close to the center of the plate 1, the boundary line 31 that defines a square region having a side length of 30 mm, and the length of the diameter. A boundary line 32b defining a circular area of 60 mm, a boundary line 32a defining a square area having a side length of 60 mm, a boundary line 33b defining a circular area having a diameter of 100 mm, A boundary line 33a defining a square area having a length of 100 mm, a boundary line 34b defining a circular area having a diameter of 130 mm, and a boundary line 34a defining a square area having a side length of 130 mm It is. The boundaries 31, 32 b, 32 a, 33 b, 33 a, 34 b, 34 a are formed so that their centers are all aligned with the center position (O) of the plate 1. Therefore, the circle drawn by the boundary line 32b is a square inscribed circle drawn by the boundary line 32a, and the circle drawn by the boundary line 33b is a square inscribed circle and border line drawn by the boundary line 33a. The circles defined by 34b are respectively square inscribed circles defined by the boundary line 34a.

  These boundary lines 31, 32b, 32a, 33b, 33a, 34b, and 34a are formed on the plate 1 by a metal thin film such as chromium (Cr). That is, these boundary lines have a level difference from the surface of the plate 1 by the thickness of the metal thin film. The step (film thickness of the metal thin film) with respect to the surface of the plate 1 is preferably in the range of 50 nm to 200 nm, for example.

Further, in the present embodiment, the region S1 outside the boundary line 31 and inside the boundary line 32b, and the region S2 outside the boundary line 32a and inside the boundary line 33b. A region S3 outside the boundary lines 34b and 33a and inside the boundary line 34a is integrally formed with each boundary line by the metal thin film.
Further, in the present embodiment, on the plate 1, the cross line L <b> 1 passing through the center position (O) of the plate 1 and the lines L <b> 21 to L <b> 24 on the extension line are provided so that the measurement center and inclination can be seen. The metal thin film is used.

In addition, each boundary line is formed with a certain width, for example, about 1 mm, but the line widths of the boundary lines 31, 32b, 32a, 33b, 34b, and 34a are included in the regions S1, S2, and S3, respectively. It is trying to be. Further, the boundary line 33a defining a 100 mm square region is formed with a line width of 1 mm, for example, inward from the 100 mm boundary. The cross line L1 and the lines L21 to L24 on the extension line are formed with a line width of 1 mm, for example, on the center line passing through the center position (O) of the plate 1 and the extension line.
Further, as shown in FIG. 1, the characters of 30 mm and 130 mm are formed by the pattern of the metal thin film, and the characters of 60 mm and 100 mm are formed by patterning the metal thin film in the regions S1 and S2, and the lower plate 1 (glass plate ) The surface is exposed.

The reference plate 20 of the present embodiment is configured as described above. Next, a method for performing calibration of the measurement region (determination of the actual measurement region) of the flatness measuring apparatus using the reference plate 20 will be described. .
First, with respect to the surface of the reference plate 20 of the present invention (the surface on which a pattern such as a boundary line is formed), a reference plane (focal plane calculated by the method of least squares) is used using a flatness measuring device using optical interference. ) To obtain the height information and store the measurement results in the computer.

FIG. 2 is a perspective view showing a three-dimensional measurement result of the flatness measuring device of the reference plate 20 of the present invention. In the figure, the acquired height information is represented in the height direction (T) of the drawing.
Then, the number of pixels of a square area of, for example, 100 mm is obtained on the center line in the measurement result shown in FIG. 2, and the size of the one pixel on the reference plate 20 is determined.

Next, using the flatness measuring apparatus, the reference surface 50 (for the main surface 101 of the glass substrate 100 for photomask blank having a size of 152 mm × 152 mm (see FIG. 3), for example, a flatness measurement target substrate. Height information (z direction) from the focal plane calculated by the method of least squares is acquired, and the measurement result is stored in a computer.
FIG. 4 is a plan view schematically showing a measurement result of the glass substrate 100 by the flatness measuring apparatus.
In the figure, the inside of the area indicated by Q is the area (Y) in which the actual measurement data (height information) exists (data can be acquired), and the outer side is the existence of the actual measurement data (height information). This is a region (N) that is not to be obtained (data could not be acquired).

  Then, based on the measurement result shown in FIG. 4 (region (Y) where actual measurement data exists) and the size of one pixel determined using the reference plate 20, the presence of data on the glass substrate 100 (data The actual measurement area (which has been acquired) can be specifically determined. As a result, on the main surface 101 of the glass substrate 100, the actual measurement area by the flatness measuring device is, for example, an area indicated by P or an area of a (mm) × b (mm) (see FIG. 3). I understand that.

As described above, by measuring the flatness of the surface of the reference plate (acquisition of the height information) by the flatness measuring device using the reference plate according to the present invention, one pixel of the reference pixel is obtained based on the measurement result. The size on the reference plate can be determined, the flatness measurement device is used to measure the flatness of the actual substrate surface, and the measurement result (the area where the actual measurement data exists) and the reference plate are used. From the size of one pixel determined in this way, the actual measurement region by the flatness measuring device can be specifically determined on the measured substrate surface. In other words, when measuring the flatness of a substrate surface such as a glass substrate for a photomask blank using an existing flatness measuring device using, for example, optical interference, the data is obtained based on the actual measurement result of the reference plate of the present invention. By determining the pixel size and calibrating the actual measurement area on the substrate, it is possible to acquire data up to which area on the substrate, and to accurately grasp the actual measurement area in the periphery of the substrate. It is also possible to do. This also makes it possible to guarantee flatness in a region including the periphery of the substrate.
Note that the actual measurement area indicated by P in FIG. 3 and the area where the actual measurement data indicated by Q in FIG. 4 exist are shown as clean rectangles (squares) as an example, but the actual substrate surface is mirror-polished. Depending on the later surface shape, the actual measurement area may not be a clean rectangle (or square).

  Further, like the reference plate 20 of the present embodiment, the predetermined area defined by the boundary line is a square or circular area having the center of the surface of the plate 1 as a substantially center (preferably the center). Is preferred. As a result, the pixel size of the data can be determined easily and accurately based on the actual measurement result of the reference plate. In addition, it is easy to correspond to the substrate to be measured, and the reliability of the calibrated actual measurement region is high.

Further, like the reference plate 20 of the present embodiment, it is preferable to have boundary lines that define a plurality of regions on the plate. For example, in the case of a flatness measuring device using optical interference, the magnification may be different between the central portion and the peripheral portion of the measurement result (that is, the size of one pixel is different), so a boundary line that defines a plurality of regions should be provided. Thus, the linearity of the magnification can be confirmed from the measurement result, and the measurement area can be calibrated with higher accuracy.
In addition, the size of the reference plate of the present invention, the number of regions in the case of providing boundary lines of a plurality of regions, the size of each region in that case, and the like are arbitrarily determined depending on the size of the substrate to be measured. There is no particular limitation in the present invention.

  The flatness measurement target substrate is not limited to the above-described glass substrate for photomask blank, but may be a substrate with a film (photomask blank) in which a thin film serving as a transfer pattern is formed on the glass substrate. In the case of a glass substrate for a photomask blank (or a photomask blank), the flatness of the substrate surface greatly affects the pattern transfer accuracy. Calibration of the measurement area of the flatness measuring device with a plate is preferred.

  In addition, flatness measuring apparatuses using optical interference are often used for flatness measurement that requires high accuracy, such as a glass substrate for photomask blanks, and flatness measurement is required for photomask blank substrates. Due to the stringency, the reference plate of the present invention is preferred. Note that the reference plate of the present invention is also suitable when the flatness of a substrate is measured using, for example, a stylus type flatness measuring device.

The reference plate 20 of the present invention may use a material other than a glass plate as the plate 1. However, when the glass plate is a glass plate, a photocatalyst is formed using a base material in which a metal thin film of an appropriate material is formed on the glass plate. By patterning the metal thin film by a lithography method, a reference plate having a high-precision pattern formed on the surface of the glass plate can be obtained. Therefore, it is suitable for evaluating a measurement area with high accuracy.
Here, as an example, a method for manufacturing the reference plate of the present invention by a photolithography method using the base material 10 shown in FIG. 5 will be described. The base material 10 shown in FIG. 5 is of a form having a metal thin film 2 such as an appropriate material such as chromium (Cr) on a glass plate (plate 1). The metal thin film 2 can be formed on a glass plate by using a film forming method such as a sputtering method or a CVD method. The thickness of the metal thin film 2 is determined in consideration of the point of patterning such as the boundary line with respect to the surface of the plate 1 after patterning.

FIGS. 6A and 6B are cross-sectional views sequentially showing the steps for producing the reference plate of the present invention using the substrate 10.
FIG. 5A shows a state in which a resist film 3 is formed on the metal thin film 2 of the substrate 10 shown in FIG.
Next, FIG. 4B shows a step of performing pattern exposure (pattern drawing) on the resist film 3 formed on the substrate 10. Pattern exposure is performed using an electron beam drawing apparatus or the like.
Next, FIG. 3C shows a process of developing the resist film 3 in accordance with the pattern exposure to form a resist pattern 3a.

Next, FIG. 4D shows a step of etching the metal thin film 2 along the resist pattern 3a. In the etching step, the exposed portion of the metal thin film 2 on which the resist pattern 3a is not formed is removed using the resist pattern 3a as a mask, thereby forming the metal thin film pattern 2a on the plate 1.
FIG. 4E shows the reference plate 20 of the present invention obtained by peeling and removing the remaining resist pattern 3a. Thus, a reference plate on which the metal thin film pattern 2a including patterns such as the plurality of boundary lines 31 to 34a, the regions S1 to S3, and the cross line L1 is formed with high pattern accuracy is completed.

  The above describes the reference plate in which a boundary line having a step from the surface of the plate 1 is formed by forming a pattern such as the boundary line on the plate 1 such as a glass plate with a metal thin film. A plate is not limited to this, For example, you may form a boundary line by giving the level | step difference of a glass surface to the glass plate surface. For such a reference plate, for example, the metal thin film pattern 2a in FIG. 6 (e) is used as a mask to perform glass etching on the exposed glass plate surface to a predetermined depth, and then the metal thin film pattern 2a is peeled off. Is obtained.

Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. In addition, a comparative example for the embodiment will also be described.
(Example)
The synthetic quartz glass substrate (approx. 152mm x approx. 152mm x approx. 6.5mm) is chamfered and ground, and the glass substrate that has been subjected to rough polishing is set in a double-side polishing machine, and the main surface of the substrate is precisely polished. Then, a glass substrate for photomask blank (152 mm × 152 mm × 6.5 mm) was prepared.

  Before measuring the flatness of the glass substrate thus obtained, the flatness of the surface of the reference plate of the present invention shown in FIG. 1 (the surface on which a pattern such as a boundary line is formed) was measured. This reference plate is formed by patterning a chromium film by a photolithography method using a base material in which a chromium (Cr) film is formed by sputtering on a synthetic quartz glass plate (size 152 mm × 152 mm) by sputtering (FIG. 1). The same pattern). With respect to the surface of this reference plate, height information from the reference surface (focal plane calculated by the method of least squares) is acquired using a flatness measuring device using optical interference, and the measurement result (the aforementioned FIG. 2). Saved on the computer. The number of pixels in a square area of 100 mm on the center line in the measurement result was obtained, and the size of the one pixel on the reference plate could be determined to be 0.794 mm. In addition, the pixel size was similarly obtained for the 30 mm square region and the 60 mm square region, and the linearity of the magnification at the central portion and the peripheral portion was confirmed. However, the result was the same as that in the 100 mm square region.

  And using the said flatness measuring apparatus, about the main surface of the above-mentioned glass substrate for photomask blanks, the height information from a reference plane (focal plane calculated by the least square method) is acquired, and the measurement result is obtained. Saved to computer. From the measurement result (area where actual measurement data exists, see FIG. 4 described above) and the size of one pixel determined using the reference plate, the data on the glass substrate exists (data was successfully acquired). The measurement area could be determined specifically. As a result, it was found that the actual measurement area by the flatness measuring device was an area of 148 mm × 148 mm on the main surface of the glass substrate, and in particular, the actual measurement area could also be grasped specifically at the periphery of the substrate. And the flatness of the said glass substrate main surface was as favorable as 0.4 micrometer. Thereby, the flatness in the region including the periphery of the substrate can be guaranteed.

  In addition, the surface roughness of the main surface of the said glass substrate was 0.2 nm by arithmetic mean surface roughness (Ra), and the shape of the said main surface was finished in convex shape. The surface roughness was measured using an atomic force microscope (AFM).

  Next, a chromium light shielding layer was formed on the glass substrate by performing reactive sputtering in an argon gas atmosphere using a chromium target as a sputtering target using an in-line sputtering apparatus. Subsequently, an antireflection layer was formed by performing reactive sputtering in a mixed gas atmosphere of argon and nitric oxide (Ar: 90% by volume, NO: 10% by volume). In this manner, a light-shielding film composed of a light-shielding layer having a total thickness of 70 nm and an antireflection layer was formed on the substrate to obtain a photomask blank.

Next, an electron beam resist film (CAR-FEP171 manufactured by Fuji Film Electronics Materials), which is a chemically amplified resist, was formed on the photomask blank using a spinner (rotary coating apparatus).
Next, a desired pattern was drawn on the resist film formed on the photomask blank using an electron beam drawing apparatus, and then developed with a predetermined developer to form a resist pattern. Next, the resist A light shielding film pattern was formed by performing dry etching of the light shielding film comprising the light shielding layer and the antireflection layer along the pattern. Here, a mixed gas of Cl ₂ and O ₂ (Cl ₂ : O ₂ = 4: 1) was used as the dry etching gas. The remaining resist pattern was peeled off to obtain a photomask.

  The obtained photomask had a small CD loss (CD error) (deviation of the measured line width with respect to the designed line width) of the pattern of the light shielding film, and the pattern accuracy of the light shielding film pattern was good. Furthermore, when this photomask was set on a mask stage having a vacuum chuck mechanism of an exposure apparatus and pattern transfer was performed on a resist film on a semiconductor substrate, the obtained circuit pattern had no defects and high-precision pattern transfer was performed. I was able to do it.

(Comparative example)
A glass substrate for photomask blank was prepared in the same manner as in the example. About the measurement area of 148 mm × 148 mm displayed on the flatness measuring apparatus on the main surface of the glass substrate for photomask blank without calibrating the measuring area of the flatness measuring apparatus using the reference plate of the present invention shown in FIG. The flatness was measured. As a result, the flatness of the main surface of the glass substrate was 0.35 μm.
Using this glass substrate, a photomask blank and a photomask are produced in the same manner as in Example 1, a photomask is set on a mask stage having a vacuum chuck mechanism of an exposure apparatus, and a pattern is transferred to a resist film on a semiconductor substrate. As a result, some semiconductor devices cannot perform pattern transfer as designed.
The cause of this was evaluated by using the reference plate of the present invention shown in FIG. 1 to evaluate the actual measurement area of the flatness measuring apparatus, and it was confirmed that only the measurement area of 145 mm × 145 mm was actually measured.
Thus, in this comparative example, the actual measurement area could be specified only in a smaller range than in the case of the example, but this means that the accuracy of the measurement area of the flatness measuring device is insufficient. Yes.
As in the above-described examples and comparative examples, the reference plate of the present invention calibrates the measurement region of the flatness measuring device and accurately evaluates the region actually measured by the flatness measuring device (actual measurement region). It is something that can be done.

  In the above-described embodiment, the case where the measurement area is calibrated using the reference plate of the present invention when the flatness measuring apparatus using optical interference is used has been described. Even when a needle-type flatness measuring device is used, the measurement region can be calibrated using the reference plate of the present invention.

It is a top view of one embodiment of the standard plate for flatness measuring device calibration concerning the present invention. It is a perspective view which shows the measurement result by the flatness measuring apparatus of the reference | standard plate for flatness measuring apparatus calibration which concerns on this invention in three dimensions. It is a perspective view for demonstrating the measurement area | region of the board | substrate which measures flatness with a flatness measuring apparatus. It is a top view which shows typically the measurement result of the board | substrate by a flatness measuring apparatus. It is sectional drawing of the base material used for preparation of the reference | standard plate for flatness measuring device calibration which concerns on this invention. It is sectional drawing which shows the preparation processes of the flatness measuring device calibration reference | standard plate which concerns on this invention.

Explanation of symbols

1 plate (glass plate)
2 Metal thin film 3 Resist film 10 Base material 20 Flatness measuring device calibration reference plate 31, 32a, 32b, 33a, 33b, 34a, 34b Boundary line 50 Reference plane 100 Substrate 101 Main surface of substrate

Claims (3)

For obtaining height information from a reference surface on a substrate surface by a flatness measurement device, calibrating a measurement region when measuring the flatness of the substrate surface, and evaluating an actual measurement region of the flatness measurement device A flatness measuring device calibration reference plate,
The substrate is a glass substrate for a photomask blank,
The said plate surface have a boundary demarcating the plurality of regions with a step on the plate,
The flatness measuring device calibration reference plate , wherein the plurality of regions are configured by a combination of a square region and a circular region that are substantially centered on the center of the plate surface . 2. The flatness measuring device calibration reference plate according to claim 1, wherein the flatness measuring device calibration reference plate is formed by forming a metal thin film pattern on a glass substrate surface. The flatness measurement device, flatness measuring device calibration reference plate according to claim 1 or 2, characterized in that a flatness measuring apparatus utilizing interference of light.

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