JP7581692B2 - Blazed diffraction grating and method for manufacturing the same - Google Patents

Description

The present invention relates to a blazed diffraction grating, which is a wavelength separation/selection element used in spectroscopes, splitters, etc., and a method for manufacturing a blazed diffraction grating.

There are various types of diffraction gratings, but a diffraction grating with a sawtooth cross-sectional shape of the grooves is called a blazed diffraction grating, and is often used in visible and ultraviolet spectroscopes because it exhibits high diffraction efficiency for light of specific wavelengths in the ultraviolet to visible light range (see Patent Document 1).

Methods for manufacturing blazed diffraction gratings include the ion beam etching method, in which an ion beam is irradiated at a specified angle onto a pattern mask formed by holographic exposure using the interference of two laser beams to cut the substrate, and the mechanical cutting method, in which grooves are machined one by one using a ruling engine. Holographic exposure has very little stray light due to periodic errors, so holographic exposure is often used to create diffraction gratings that require low stray light.

1 is a diagram illustrating a method for manufacturing a blazed diffraction grating by ion beam etching. In the ion beam etching method, a photoresist is first applied to the surface of a flat substrate 1 made of quartz, glass, or the like to form a photoresist layer 2 (FIG. 1(a)).
Then, the photoresist layer 2 is exposed and developed to produce interference fringes due to two-beam interference, forming a parallel-line resist pattern 3 as shown in Fig. 1(b) (holographic exposure). Next, using the resist pattern 3 as a mask, etching is performed with an ion beam from obliquely above so that the desired blaze angle θB is formed on the substrate 1, forming grating grooves 4 with a sawtooth cross section on the substrate 1 (Figs. 1(c) to (e)). Thereafter, as shown in Fig. 1(f), a metal film 5 such as aluminum or gold is coated on the surface of the grating grooves 4 to complete the blazed diffraction grating.

In the above-mentioned etching process, ion beam etching is usually performed using an etching gas whose etching rate for the substrate 1 is faster than that for the resist pattern 3, i.e., whose selectivity (= etching rate for the substrate material (e.g., glass)/etching rate for the photoresist) is greater than 1.

A master blazed diffraction grating is manufactured through this process. A release agent layer is formed on the grating surface of this master diffraction grating, and a metal thin film is formed on top of that. A glass substrate is then attached onto this metal thin film via an adhesive, and after the adhesive has hardened, the glass substrate is peeled off from the master diffraction grating. As a result, the metal thin film with the grating grooves is transferred upside down to the glass substrate, and a replica diffraction grating is obtained. This replica diffraction grating is used as a matrix to manufacture a blazed diffraction grating as a product (see Patent Document 1).

JP 2009-92687 A

Spectrophotometers using such blazed diffraction gratings have traditionally been developed primarily for measuring the absorption of liquid samples, but in recent years, there has been a rapid increase in applications for measuring the reflection and absorption of solids, such as semiconductors, thin films, glass materials, and absorbents. These applications require high-precision, high-energy (vacuum ultraviolet region) spectrometers, and the performance of these instruments is highly dependent on the performance of the diffraction grating, so there was a demand for blazed diffraction gratings that could achieve high diffraction efficiency in the vacuum ultraviolet and deep ultraviolet regions.

Thus, in order to obtain high diffraction efficiency in the vacuum ultraviolet region (120 to 200 nm) and deep ultraviolet region (200 to 300 nm), it is necessary to shorten the grating spacing and form a diffraction grating pattern with a shallow blaze angle θB (for example, a height of 100 nm or less) on the substrate.
Furthermore, in order to produce peak wavelengths in increments of several tens of nm (for example, 120 nm, 160 nm), it is necessary to control the height of the diffraction grating pattern with an accuracy of about several nm.
However, in conventional manufacturing methods such as that described in Patent Document 1, an ideal sinusoidal resist pattern is formed on a substrate by holographic exposure, and then an ion beam is irradiated from above at a target angle to form a diffraction grating pattern. This requires precise understanding and control of the incidence angle α and spread angle of the ion beam, and it is difficult to achieve such precision due to the performance of the etching apparatus.
Furthermore, in order to manufacture a blazed diffraction grating with a small blaze angle θB, it is necessary to increase the incident angle α of the ion beam. In this case, however, the step surface 12 between one blaze surface 11 and the adjacent blaze surface 11 is deeply etched, resulting in a rounded apex angle β, making it difficult to obtain high diffraction efficiency.

The present invention was made in consideration of the above circumstances, and aims to provide a blazed diffraction grating that has a diffraction grating pattern with a blaze height formed with higher accuracy than existing ones, and can obtain high diffraction efficiency in the vacuum ultraviolet and deep ultraviolet regions.

The blazed diffraction grating of the first aspect of the present invention comprises a substrate having a sawtooth cross-sectional shape and in which blazed surfaces and step surfaces are repeatedly arranged alternately in one direction, a reflective film formed to cover the surfaces of the blazed surfaces and step surfaces, and a coating film formed to cover the surface of the reflective film, and is configured so that the sum of the film thicknesses of the reflective film and the coating film is maximum at the tops of the blazed surfaces and step surfaces and minimum at the bottoms.

The method for manufacturing a blazed diffraction grating according to the second aspect of the present invention includes the steps of preparing a substrate having a sawtooth cross-sectional shape and in which blazed surfaces and step surfaces are arranged alternately and repeatedly in one direction, forming a reflective film to cover the surfaces of the blazed surfaces and step surfaces, and forming a coating film to cover the surfaces of the reflective film, and in the steps of forming these films, the coating film is formed so that the thickness of the coating film is maximum at the tops of the blazed surfaces and step surfaces and minimum at the bottoms.

The present invention makes it possible to realize a blazed diffraction grating that has a diffraction grating pattern with a blaze height formed with greater precision than existing ones, and that can achieve high diffraction efficiency in the vacuum ultraviolet and deep ultraviolet regions.

FIG. 1 is a diagram illustrating a conventional method for manufacturing a blazed diffraction grating. FIG. 2 is a diagram illustrating the configuration of a blazed diffraction grating according to a first embodiment of the present invention. FIG. 3 is a diagram showing a schematic configuration of a vacuum chamber used for manufacturing the blazed diffraction grating according to the first embodiment of the present invention. FIG. 4 is a diagram showing the results of measuring the cross-sectional shape of the blazed diffraction grating according to the first embodiment of the present invention. FIG. 5 is a diagram showing the results of measuring the cross-sectional shape of a blazed diffraction grating according to a second embodiment of the present invention.

The blazed diffraction grating and the method for manufacturing the blazed diffraction grating of the present invention will be described in detail below based on the preferred embodiment (example) shown in the attached drawings.

(First embodiment)
Fig. 2 is a diagram illustrating the configuration of a blazed diffraction grating 20 according to a first embodiment of the present invention, in which Fig. 2(a) is a plan view of the blazed surface viewed in the vertical direction, and Fig. 2(b) is an enlarged cross-sectional view taken along line A-A in Fig. 2(a). As shown in Fig. 2, the blazed diffraction grating 20 of this embodiment includes a substrate 22, a reflective film 24, and a coating film 26.

The base material 22 is a basic replica diffraction grating formed by a conventional ion beam etching method or the like, and a basic diffraction grating 22a is formed from resin on a rectangular plate-shaped glass base material. The basic diffraction grating 22a is configured by repeating basic blaze surfaces 22b and basic step surfaces 22c alternately in one direction so that the cross-sectional shape is sawtooth-shaped. In this embodiment, a grating with 1600 grooves, blaze height (h1): 40 nm, and blaze wavelength: 120 nm is used.

The reflective film 24 is a thin metal film formed to cover the base diffraction grating 22a, and in this embodiment is an 80 nm thick aluminum (Al) film. The reflective film 24 is formed on the base blaze surface 22b and the base step surface 22c using a method such as vacuum deposition or sputtering (details will be described later).

The coating film 26 is a thin film formed to cover the reflective film 24 by using a vacuum deposition method, a sputtering method, or the like, and in this embodiment, it is a magnesium fluoride (MgF2) film that prevents the surface of the reflective film 24 from being oxidized. By forming the coating film 26, a diffraction grating 26a consisting of a blaze surface 26b and a step surface 26c is formed on the coating film 26. Note that the thickness of the coating film 26 in this embodiment is not uniform, but changes monotonically in one direction on the basic blaze surface 22b, and the thickness (t2 in FIG. 2B) at the top (convex part of the unevenness) of the basic diffraction grating 22a is thicker than the thickness (t1 in FIG. 2B) at the bottom (concave part of the unevenness) of the basic diffraction grating 22a. As a result, the grooves of the coating film 26 formed on the coating film 26 are deeper than the grooves of the basic diffraction grating 22a.
In other words, the blazed diffraction grating 20 of this embodiment is configured so that the sum of the film thicknesses of the reflective film 24 and the coating film 26 is maximum at the tops of the blazed surfaces 26b and the step surfaces 26c and minimum at the bottoms.
In addition, it is preferable that the thickness of the coating film 26 satisfies the following conditional formula (1), where the film thickness at the top is t2 and the film thickness at the bottom is t1 . In this embodiment, the blaze height (h2) is 60 nm.
t2-t1 ≦ 80nm...(1)

In this way, when the reflective film 24 and the coating film 26 are formed on the base diffraction grating 22a of the substrate 22, the inclination of the blaze surface 26b and the step surface 26c becomes steeper than the inclination of the base blaze surface 22b and the base step surface 22c. Therefore, the angle β2 (vertex angle) between the blaze surface 26b and the step surface 26c becomes smaller (i.e., acute angle) than the angle β1 between the base blaze surface 22b and the base step surface 22c. Therefore, the blaze angle θB2 of the blazed diffraction grating 20 becomes larger than the blaze angle θB1 of the base diffraction grating 22a, and as a result, the blaze wavelength becomes 180 nm (i.e., shifted to the long wavelength side).
In addition, the diffraction efficiency is increased because the apex angle of the blaze is acute (details will be described later). In this specification, the relative diffraction efficiency refers to a value that indicates the efficiency of the blazed diffraction grating 20 alone excluding the reflectance of the coating material (i.e., the coating film 26), and is a value indicated by "absolute diffraction efficiency/reflectance of the coating material".

(Method of Manufacturing Blazed Diffraction Grating 20)
Next, a method for manufacturing the blazed diffraction grating 20 of this embodiment will be described in detail.

(1) Preparation of Substrate 22 In manufacturing the blazed diffraction grating 20, first, a substrate 22 (basic replica diffraction grating) is prepared, which is formed by a conventional ion beam etching method or the like.

(2) Mounting of the Substrate 22 Next, the substrate 22 is mounted in the vacuum chamber 100 .
Fig. 3 is a diagram showing a schematic configuration of a vacuum chamber 100 used for manufacturing the blazed diffraction grating 20 of this embodiment. As shown in Fig. 3, the vacuum chamber 100 is composed of a chamber body 101 and a vacuum pump 102, and the chamber body 101 is provided with a dome body 110, an aluminum boat 120, a magnesium fluoride boat 130, a shutter 140 for the aluminum boat 120, and a shutter 150 for the magnesium fluoride boat 130.
The dome body 110 is a rotating body that rotates horizontally and has a dome shape with a radius of 300 mm, and the upper end (connection part) of the dome body 110 is disposed approximately 500 mm above the deposition source (shutters 140, 150). The surface of the dome body 110 serves as a mounting surface on which the substrate 22 is placed, and the substrate 22 is attached at a position approximately 45 mm below the upper end (connection part) of the dome body 110 with the blaze direction facing the inside of the dome body 110.

(3) Preparation of Vacuum Chamber 100 Next, materials are placed in the aluminum boat 120 and the magnesium fluoride boat 130, respectively, and the vacuum pump 102 is started to evacuate the inside of the chamber body 101.

(4) Formation of Reflective Film 24 Next, after it is confirmed that the inside of the chamber body 101 has reached a film-forming vacuum degree, aluminum and magnesium fluoride are melted in with the shutters 140 and 150 closed. Then, after it is confirmed again that the inside of the chamber body 101 has reached a film-forming vacuum degree, the dome body 110 is rotated at 20 rpm to start vaporizing aluminum, and after confirming a predetermined deposition rate (for example, a predetermined value of 10 nm/sec or more), the shutter 140 is opened.
Then, when the desired film thickness (for example, about 80 nm) is confirmed with the film thickness meter, the shutter 140 is closed. Note that the reflective film 24 does not necessarily have to have a uniform film thickness, but it is preferable that the film thickness is approximately uniform.

(5) Formation of Coating Film 26 Next, vaporization of magnesium fluoride is started, and after a predetermined deposition rate (for example, a predetermined value of 2 nm/sec or more) is confirmed, the shutter 150 is opened.
Then, when the desired film thickness (for example, 20 nm) is confirmed with the film thickness meter, the shutter 150 is closed.

(6) Removal of the Finished Product The chamber body 101 is opened to the atmosphere, and the finished product on which the coating film 26 is formed is removed from the chamber body 101, thereby obtaining the blazed diffraction grating 20 of this embodiment.

4A shows the results of measuring the cross-sectional shape of the substrate 22 before the formation of the reflective film 24 and the coating film 26 (i.e., the cross-sectional shapes of the basic blaze surface 22b and the basic step surface 22c), and FIG. 4B shows the results of measuring the cross-sectional shape of the blazed diffraction grating 20 after the formation of the reflective film 24 and the coating film 26 (i.e., the cross-sectional shapes of the blaze surface 26b and the step surface 26c). In FIG. 4A and FIG. 4B, the solid lines show the measurement results when a sample of the blazed diffraction grating 20 of this embodiment is measured from left to right, and the dashed lines show the measurement results when a sample of the blazed diffraction grating 20 of this embodiment is measured from right to left.
4(a) and (b), the blazed diffraction grating 20 of this embodiment has a blaze height that is 20 nm higher and an acute apex angle, resulting in a higher diffraction efficiency (maximum relative diffraction efficiency: 55%) than a diffraction grating with the same blaze height.

The above is a description of this embodiment, but the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the technical concept of the present invention.

For example, in this embodiment, a blazed diffraction grating 20 with a blaze height (h2): 60 nm and a blaze wavelength: 180 nm was obtained using a substrate 22 with a blaze height (h1): 40 nm and a blaze wavelength: 120 nm, but by changing the deposition conditions of the coating film 26, diffraction gratings 26a with various blaze heights (h2) can be formed, and blazed diffraction gratings 20 with different blaze wavelengths (e.g., 120 to 300 nm) can be manufactured. This makes it possible to obtain blazed diffraction gratings 20 with different blaze wavelengths without having to fabricate (prepare) a master diffraction grating according to the blaze height (h2) as in the conventional method.

In addition, in this embodiment, the thickness of the reflective film 24 is 80 nm, but this is not limited to this configuration, and the thickness can be set in the range of 40 to 80 nm.

(Second Example)
5 is a diagram for explaining the cross-sectional shape of the blazed diffraction grating 20 manufactured by changing the film formation conditions of the coating film 26. FIG. 5(a) is a result of measuring the cross-sectional shape of the substrate 22 before the formation of the reflective film 24 and the coating film 26 of the second embodiment (i.e., the cross-sectional shapes of the basic blaze surface 22b and the basic step surface 22c), and FIG. 5(b) is a result of measuring the cross-sectional shape of the blazed diffraction grating 20 after the formation of the reflective film 24 and the coating film 26 of the second embodiment (i.e., the cross-sectional shapes of the blaze surface 26b and the step surface 26c). In FIG. 5(a) and FIG. 5(b), the solid lines are the measurement results when the sample of the blazed diffraction grating 20 of this embodiment is measured from left to right, and the dashed lines are the measurement results when the sample of the blazed diffraction grating 20 of this embodiment is measured from right to left.

The blazed diffraction grating 20 of this embodiment differs from the blazed diffraction grating 20 of the first embodiment in that a substrate 22 having 1200 grooves, a blaze height (h1) of 45 nm, and a blaze wavelength of 140 nm is used, and the blaze height (h2) is 90 nm and the blaze wavelength is 220 nm. The manufacturing method of the blazed diffraction grating 20 of this embodiment is the same as that of the first embodiment.
5(a) and (b), the blazed diffraction grating 20 of this embodiment has a blaze height 40 nm higher and an acute apex angle, and thus a higher diffraction efficiency (maximum relative diffraction efficiency: 70%) was obtained than a diffraction grating with the same blaze height.

[Aspects]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

(Item 1) A blazed diffraction grating (20) according to one embodiment comprises:
A substrate (22) having a sawtooth cross-sectional shape, in which blazed surfaces (22b) and stepped surfaces (22c) are alternately and repeatedly arranged in one direction;
a reflective film (24) formed so as to cover the surfaces of the blazed surface (22b) and the stepped surface (22c);
A coating film (26) formed so as to cover the surface of the reflective film (24);
Equipped with
The sum of the film thicknesses of the reflective film (24) and the coating film (26) is configured to be maximum at the tops of the blazed surface (22b) and the step surface (22c) and minimum at the bottoms.

According to the blazed diffraction grating described in paragraph 1, the apex angle of the blaze is acute, so that a higher diffraction efficiency can be obtained compared to conventional blazed diffraction gratings. In addition, the coating film (26) forms new blazed surfaces and step surfaces different from the blazed surface (22b) and step surface (22c), so that a blazed diffraction grating with any blazed wavelength can be obtained.

(2) The blazed diffraction grating (20) according to (1),
The coating film (26) is configured to satisfy the following conditional formula (1), where the film thickness at the top is t2 and the film thickness at the bottom is t1 .
t2-t1 ≦ 80nm...(1)

According to the blazed diffraction grating described in paragraph 2, by appropriately selecting t1 and t2 that satisfy conditional formula (1), high diffraction efficiency can be obtained at specific wavelengths in the vacuum ultraviolet and deep ultraviolet regions.

(Item 3) A blazed diffraction grating (20) according to item 1 or 2,
The coating film (26) is configured so that the film thickness on the blazed surface (22b) monotonically increases from the bottom to the top.

The blazed diffraction grating described in paragraph 3 reduces light loss, thereby improving diffraction efficiency.

(4) A blazed diffraction grating (20) according to any one of (1) to (3),
The coating film (26) is a vapor-deposited film of a fluoride.

The blazed diffraction grating described in paragraph 4 can be manufactured easily and inexpensively.

(5) A blazed diffraction grating (20) according to claim 4,
The fluoride is magnesium fluoride.

The blazed diffraction grating described in paragraph 5 can be manufactured easily and inexpensively.

(Item 6) A blazed diffraction grating (20) according to any one of items 1 to 5,
The reflective film has a substantially constant thickness.

The blazed diffraction grating described in paragraph 6 provides a constant diffraction efficiency.

(Item 7) The blazed diffraction grating (20) according to item 6,
The reflective film has a thickness of 40 to 80 nm.

The blazed diffraction grating described in paragraph 7 provides a constant diffraction efficiency.

(Item 8) A blazed diffraction grating (20) according to any one of items 1 to 7,
The reflective film is a vapor-deposited aluminum film.

The blazed diffraction grating described in paragraph 8 can be manufactured easily and inexpensively.

(Item 9) A blazed diffraction grating (20) according to any one of items 1 to 8,
The blaze wavelength is 120 to 300 nm.

The blazed diffraction grating described in paragraph 9 can provide high diffraction efficiency in the vacuum ultraviolet and deep ultraviolet regions.

(Item 10) A method for manufacturing a blazed diffraction grating (20) according to one embodiment includes the steps of:
A step of preparing a substrate (22) having a sawtooth cross-sectional shape and in which blazed surfaces (22b) and stepped surfaces (22c) are alternately and repeatedly arranged in one direction;
forming a reflective film (24) so as to cover the surfaces of the blazed surface (22b) and the stepped surface (22c);
forming a coating film (26) so as to cover a surface of the reflective film (24);
Including,
In the step of forming the coating film (26), the coating film (26) is formed so that the thickness of the coating film (26) is maximum at the tops of the blaze surface (22b) and the step surface (22c) and is minimum at the bottoms.

According to the method for manufacturing a blazed diffraction grating described in paragraph 10, the apex angle of the blaze is acute, so that a blazed diffraction grating with higher diffraction efficiency can be obtained compared to conventional blazed diffraction gratings. In addition, the coating film (26) forms new blazed surfaces and step surfaces different from the blazed surface (22b) and step surface (22c), so that a blazed diffraction grating with any blazed wavelength can be obtained.

(Item 11) A method for manufacturing a blazed diffraction grating (20) according to item 10, comprising:
The coating film (26) is configured to satisfy the following conditional formula (1), where the film thickness at the top is t2 and the film thickness at the bottom is t1 .
t2-t1 ≦ 80nm...(1)

The manufacturing method of the blazed diffraction grating described in paragraph 11 makes it possible to obtain a blazed diffraction grating with high diffraction efficiency in the vacuum ultraviolet and deep ultraviolet regions.

(Item 12) A method for manufacturing a blazed diffraction grating (20) according to item 10 or 11,
In the step of forming the coating film (26), the coating film (26) is formed so that the film thickness of the coating film (26) on the blazed surface (22b) monotonically increases from the bottom to the top.

The manufacturing method of the blazed diffraction grating described in paragraph 12 makes it possible to obtain a blazed diffraction grating with reduced light loss and high diffraction efficiency.

(Item 13) A method for manufacturing a blazed diffraction grating (20) according to any one of items 10 to 12, comprising:
The coating film (26) is a vapor-deposited film of a fluoride.

The method for manufacturing a blazed diffraction grating described in paragraph 13 makes it possible to easily and inexpensively obtain a blazed diffraction grating.

(Item 14) A method for manufacturing a blazed diffraction grating (20) according to item 13, comprising:
The fluoride is magnesium fluoride.

The method for manufacturing a blazed diffraction grating described in paragraph 14 makes it possible to easily and inexpensively obtain a blazed diffraction grating.

(Item 15) A method for manufacturing a blazed diffraction grating (20) according to any one of items 10 to 14, comprising:
In the step of forming the coating film, the coating film is formed at a rate of 2 nm/sec or more.

The manufacturing method for a blazed diffraction grating described in paragraph 15 makes it possible to form a coating film with a stable thickness, resulting in a blazed diffraction grating with constant diffraction efficiency.

(Item 16) A method for manufacturing a blazed diffraction grating (20) according to any one of items 10 to 15, comprising:
In the step of forming the reflective film (24), the reflective film (24) is formed so that the film thickness is approximately constant.

The method for manufacturing a blazed diffraction grating described in paragraph 16 makes it possible to obtain a blazed diffraction grating with a constant diffraction efficiency.

(Item 17) A method for manufacturing a blazed diffraction grating (20) according to item 16, comprising:
The reflective film has a thickness of 40 to 80 nm.

The manufacturing method of a blazed diffraction grating described in paragraph 17 makes it possible to obtain a blazed diffraction grating with a constant diffraction efficiency.

(Item 18) A method for manufacturing a blazed diffraction grating (20) according to any one of items 10 to 17, comprising the steps of:
The reflective film is a vapor-deposited aluminum film.

The method for manufacturing a blazed diffraction grating described in paragraph 18 makes it possible to easily and inexpensively obtain a blazed diffraction grating.

(Item 19) A method for manufacturing a blazed diffraction grating (20) according to any one of items 10 to 18, comprising the steps of:
In the step of forming the reflective film, the reflective film is formed at a rate of 10 nm/sec or more.

The manufacturing method for a blazed diffraction grating described in paragraph 19 makes it possible to form a reflective film with a stable thickness, resulting in a blazed diffraction grating with constant diffraction efficiency.

(Item 20) A method for manufacturing a blazed diffraction grating (20) according to any one of items 10 to 19, comprising:
The blaze wavelength is 120 to 300 nm.

The manufacturing method of the blazed diffraction grating described in paragraph 20 makes it possible to obtain a blazed diffraction grating with high diffraction efficiency in the vacuum ultraviolet and deep ultraviolet regions.

(Item 21) A method for manufacturing a blazed diffraction grating (20) according to any one of items 10 to 20, comprising:
After preparing the base material, the method further includes attaching the substrate to a surface of the dome body;
In the step of forming the reflective film and the step of forming the coat film, the reflective film and the coat film are formed in a state in which the dome body is rotated around the central axis at a predetermined number of rotations.

According to the method for manufacturing a blazed diffraction grating described in paragraph 21, a coating film with a stable thickness can be formed by utilizing centrifugal force, and a blazed diffraction grating with constant diffraction efficiency can be obtained.

1: Substrate 2: Photoresist layer 3: Resist pattern 4: Grating groove 5: Metal film 11: Blazed surface 12: Step surface 20: Blazed diffraction grating 22: Base material 22a: Basic diffraction grating 22b: Basic blazed surface 22c: Basic step surface 24: Reflection film 26: Coating film 26a: Diffraction grating 26b: Blazed surface 26c: Step surface 100: Vacuum chamber 101: Chamber body 102: Vacuum pump 110: Dome body 120: Aluminum boat 130: Magnesium fluoride boat 140: Shutter 150: Shutter

Claims (21)

A substrate having a sawtooth cross-sectional shape, in which blazed surfaces and stepped surfaces are repeatedly arranged alternately in one direction;
a reflective film formed so as to cover the surfaces of the blaze surface and the step surface;
a coating film formed so as to cover a surface of the reflective film;
Equipped with
A blazed diffraction grating, wherein by changing the thickness of the coating film, a total thickness of the reflective film and the coating film between the tops of the blazed surfaces and the step surfaces of the substrate and the coating film is maximized, and a total thickness of the film between the bottoms of the blazed surfaces and the step surfaces of the substrate and the coating film is minimized. 2. The blazed diffraction grating according to claim 1, wherein the following conditional expression (1) is satisfied, where t2 is a thickness of the coating film between the top portions and t1 is a thickness of the coating film between the bottom portions:

t2-t1 ≦ 80nm...(1)
The blazed diffraction grating according to claim 1 or 2, wherein the thickness of the coating film on the blazed surface increases monotonically from the bottom to the top. The blazed diffraction grating according to any one of claims 1 to 3, wherein the coating film is a vapor deposition film of a fluoride. The blazed diffraction grating of claim 4, wherein the fluoride is magnesium fluoride. A blazed diffraction grating according to any one of claims 1 to 5, wherein the thickness of the reflective film is substantially constant. The blazed diffraction grating according to claim 6, wherein the thickness of the reflective film is 40 to 80 nm. The blazed diffraction grating according to any one of claims 1 to 7, wherein the reflective film is an aluminum vapor deposition film. A blazed diffraction grating according to any one of claims 1 to 8, having a blaze wavelength of 120 to 300 nm. A step of preparing a substrate having a sawtooth cross-sectional shape, in which blazed surfaces and stepped surfaces are repeatedly arranged alternately in one direction;
forming a reflective film so as to cover the surfaces of the blazed surface and the step surface;
forming a coating film so as to cover a surface of the reflective film;
Including,
A method for manufacturing a blazed diffraction grating, wherein the step of forming the coating film includes changing a thickness of the coating film to form the coating film so that a sum of film thicknesses of the reflective film and the coating film between the tops of the blazed surface and the step surface of the substrate and the coating film is maximized, and a sum of film thicknesses between the bottoms of the blazed surface and the step surface of the substrate and the coating film is minimized. 11. The method for manufacturing a blazed diffraction grating according to claim 10, wherein the following conditional formula (1) is satisfied, when a thickness of the coating film between the top portions is t2 and a thickness of the coating film between the bottom portions is t1:

t2-t1 ≦ 80nm...(1)
The method for manufacturing a blazed diffraction grating according to claim 10 or 11, wherein the step of forming the coating film forms the coating film so that the film thickness of the coating film on the blazed surface increases monotonically from the bottom to the top. The method for manufacturing a blazed diffraction grating according to any one of claims 10 to 12, wherein the coating film is a vapor deposition film of a fluoride. The method for manufacturing a blazed diffraction grating according to claim 13, wherein the fluoride is magnesium fluoride. The method for manufacturing a blazed diffraction grating according to any one of claims 10 to 14, wherein the step of forming the coating film forms the coating film at a rate of 2 nm/sec or more. The method for manufacturing a blazed diffraction grating according to any one of claims 10 to 15, wherein the step of forming the reflective film forms the reflective film so that the film thickness is approximately constant. The method for manufacturing a blazed diffraction grating according to claim 16, wherein the thickness of the reflective film is 40 to 80 nm. The method for manufacturing a blazed diffraction grating according to any one of claims 10 to 17, wherein the reflective film is an aluminum vapor deposition film. The method for manufacturing a blazed diffraction grating according to any one of claims 10 to 18, wherein the step of forming the reflective film forms the reflective film at a rate of 10 nm/sec or more. A method for manufacturing a blazed diffraction grating according to any one of claims 10 to 19, wherein the blaze wavelength is 120 to 300 nm. After providing the substrate, the method further includes attaching the substrate to a surface of the dome body;
21. The method for manufacturing a blazed diffraction grating according to claim 10, wherein the step of forming the reflective film and the step of forming the coating film form the reflective film and the coating film while rotating the dome body at a predetermined number of rotations around a central axis.

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