Method for manufacturing optical filters

Abstract

To more easily manufacture an optical filter having a thin film on a substrate that has a continuous film thickness gradient in a specific direction of the substrate. [Solution] A first aspect of the method for manufacturing an optical filter according to the present invention involves arranging a flat target material on a negative electrode facing a positive electrode in a chamber, arranging a flat substrate at a predetermined position in the chamber such that the angle between a straight line connecting one end of the substrate and the furthest end of the target material from the substrate and one main surface of the substrate is 90° or more and 180° or less, the angle between a straight line connecting the one end of the substrate and the closest end of the target material from the substrate and the main surface is 90° or more and 180° or less, and the angle between the surface of the target material and the main surface is 60° or more, introducing an inert gas into the chamber, and using the plasma of the inert gas generated by applying a predetermined voltage between the positive electrode and the negative electrode, particles of the target material are attached to the main surface of the substrate.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical filter.

Background Art

[0002] There is an optical filter in which an optical thin film (hereinafter simply referred to as a thin film) formed on a substrate has a continuous film thickness gradient in a specific direction of the substrate. Such an optical filter is also called a linear variable filter, and when the position where light is incident is changed along the specific direction, the transmission spectrum of the incident light changes continuously.

[0003] Such an optical filter is manufactured, for example, by repeating a step of forming a thin film having a predetermined thickness on the substrate after arranging a plurality of strip-shaped masks on the substrate in the longitudinal direction of the substrate and a step of peeling off one mask from the end on the substrate. In addition, Patent Document 1 describes that a mask plate and a correction plate are arranged between an evaporation source of a film-forming material and a substrate to form a thin film layer having a desired film thickness gradient regardless of the film-forming material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The step of forming a thin film so as to form a continuous film thickness gradient in a specific direction of the substrate requires a large number of man-hours and takes a lot of time and cost for manufacturing. That is, the problem to be solved by the present invention is to manufacture an optical filter provided with a thin film having a continuous film thickness gradient in a specific direction of the substrate more simply.

Means for Solving the Problems

[0006] A first aspect of the method for manufacturing an optical filter according to the present invention, which was developed to solve the above problems, is: A flat target material is placed on the negative electrode opposite the positive electrode within the chamber. A flat substrate is positioned in a predetermined location within the chamber such that the angle between the straight line connecting one end of the substrate and the furthest end of the target material from the substrate and one of the main surfaces of the substrate is 90° or more and 180° or less, the angle between the straight line connecting the one end of the substrate and the closest end of the target material from the substrate and the main surface is 90° or more and 180° or less, and the angle between the surface of the target material and the main surface is 60° or more. The method involves introducing an inert gas into the chamber and applying a predetermined voltage between the positive electrode and the negative electrode to generate a plasma of the inert gas, which is then used to attach the particles of the target material to the main surface of the substrate.

[0007] Furthermore, a second aspect of the method for manufacturing an optical filter according to the present invention, which was developed to solve the above problems, is: A flat target material is placed on the negative electrode opposite the positive electrode within the chamber. A flat substrate is placed in a predetermined position within the chamber such that the target material is positioned on one of the main surfaces of the substrate, the portion of the target material projected onto the plane from a direction perpendicular to the plane containing the main surface does not overlap with the main surface, and the angle between the surface of the target material and the main surface is 60° or more. The method involves introducing an inert gas into the chamber and applying a predetermined voltage between the positive electrode and the negative electrode to generate a plasma of the inert gas, which is then used to attach the particles of the target material to the main surface of the substrate. [Effects of the Invention]

[0008] In the method for manufacturing an optical filter according to the present invention, a predetermined voltage is applied between opposing positive and negative electrodes in a chamber, causing the inert gas in the chamber to become plasma. This plasma collides with a target material, causing particles of the target material to be ejected. These ejected target material particles adhere to the surface of a substrate. As the target material particles travel through the plasma atmosphere, the amount of target material particles adhering to each point on the substrate decreases as the distance from the target material increases. In a first aspect of the method for manufacturing an optical filter according to the present invention, the substrate and target material are arranged such that the angle between a straight line connecting one end of the substrate and the furthest end of the target material from the substrate and one main surface of the substrate is 90° or more and 180° or less, the angle between a straight line connecting the one end of the substrate and the closest end of the target material from the substrate and the main surface of the target material is 90° or more and 180° or less, and the angle between the surface of the target material and the main surface is 60° or more. As a result, the amount of target material particles adhering to one main surface of the substrate decreases as the distance from the target material increases. This allows for the manufacture of an optical filter in which the film thickness decreases in the direction away from the target material. Furthermore, in a second embodiment of the method for manufacturing an optical filter according to the present invention, the substrate and the target material are arranged such that the target material is located on one main surface side of the substrate, the portion of the target material projected onto the plane containing the main surface from a direction perpendicular to the plane does not overlap with the main surface, and the angle between the surface of the target material and the main surface is 60° or more. As a result, the feet of the perpendiculars drawn from each point of the target material to the plane containing the main surface of the substrate are all located on the extension of the main surface, and the amount of target material particles adhering to one main surface of the substrate decreases as the distance from the target material increases. This results in the production of an optical filter in which the film thickness decreases in the direction away from the target material.

[0009] Therefore, according to the method for manufacturing an optical filter of the present invention, an optical filter comprising a thin film having a continuous film thickness gradient in a specific direction of the substrate can be manufactured more easily. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a schematic configuration of a sputtering apparatus according to an embodiment. [Figure 2] Figure 1 is a schematic diagram showing the positional relationship between the substrate and the target material when viewed from the front of the page. [Figure 3] This diagram shows various positional relationships between the substrate and the target material when the substrate is rotated around one end. [Figure 4] This figure shows the arrangement of the substrate and target material inside the sputtering apparatus in the embodiment. [Figure 5] This is a photograph showing the arrangement of the substrate and target material inside the sputtering apparatus in the example. [Figure 6] This screen shows the structure of the multilayer film deposited on the substrate in the example. [Figure 7] This is a photograph of the optical filter fabricated in the example. [Figure 8] This figure shows the transmittance for each wavelength at each point on the optical filter fabricated in the example. [Modes for carrying out the invention]

[0011] An exemplary embodiment of the method for manufacturing an optical filter according to the present invention will be described with reference to the drawings. Figure 1 is a diagram showing the schematic configuration of a sputtering apparatus according to this embodiment. The sputtering apparatus 1 comprises a chamber 10 having a gas inlet and an exhaust port, a positive electrode 11 and a negative electrode 12 facing each other within the chamber 10, and a voltage source 13 for applying a predetermined voltage to the positive electrode 11 and the negative electrode 12. The positive electrode 11 is provided with a first mounting member for attaching a substrate 20, and the negative electrode 12 is provided with a second mounting member for attaching a target material 30 (neither is shown). Furthermore, an inert gas source is attached to the gas inlet, and a vacuum pump (such as a rotary pump or a turbomolecular pump) is attached to the exhaust port (neither is shown).

[0012] In this embodiment, the positive electrode 11 is located at the top of the chamber 10, and the negative electrode 12 is located at the bottom. Both the lower surface of the positive electrode 11 and the upper surface of the negative electrode 12 are flat surfaces, and the positive electrode 11 and the negative electrode 12 are positioned so that both surfaces are parallel. The flat target material 30 is positioned so that its entire surface is in contact with the upper surface of the negative electrode 12. On the other hand, the flat substrate 20 is positioned at a predetermined location and in a predetermined orientation on the positive electrode 11.

[0013] The orientation of the substrate 20 will be explained with reference to Figure 2. Figure 2 is a schematic diagram showing the positional relationship between the substrate 20 and the target material 30 when Figure 1 is viewed from the front of the paper. The lower and upper ends of the substrate 20 are denoted as A and B, respectively, and the right and left ends of the target material 30 are denoted as P and Q, respectively. Points P and Q are the farthest and closest endpoints from the substrate 20, respectively. In this embodiment, the substrate 20 is positioned such that the angle between the straight line AP and the main surface of the substrate 20 on the film-forming side (hereinafter referred to as the main surface AB) is between 90° and 180°, the angle between the straight line AQ and the main surface AB is between 90° and 180°, and the angle between the surface of the target material 30 and the main surface AB is 60° or more. When the substrate 20 is positioned in this orientation relative to the target material 30, the distance from any point on the target material 30 to each point on the substrate 20 is smallest at point A and largest at point B. In other words, from any point on the target material 30, the distance to the main surface AB of the substrate 20 increases monotonically and continuously from point A to point B. Note that setting the angle between the surface of the target material 30 and the main surface AB to 60° or more is not a necessary condition for the distance to the main surface AB of the substrate 20 to increase monotonically and continuously from point A to point B, from any point on the target material 30, but it is required to increase the film thickness gradient on the substrate 20, as will be described later.

[0014] The operation of the sputtering apparatus 1 is the same as that of a known sputtering apparatus. That is, after placing the substrate 20 and the target material 30 in the chamber 10, the inside of the chamber 10 is evacuated, and an inert gas such as argon (Ar) is introduced. Then, a predetermined voltage (DC voltage, pulsed DC voltage, AC voltage, high-frequency voltage, microwave voltage, etc.) is applied between the positive electrode 11 and the negative electrode 12 to plasmaize the inert gas in the chamber 10. In the plasma, the inert gas is positively charged and continuously collides with the target material 30 disposed on the negative electrode 12. When the cations of the inert gas collide with the target material 30, particles of the target material 30 fly out, and the particles move in the plasma atmosphere and adhere to the surface of the substrate 20. Thereby, a thin film is formed on the surface of the substrate 20.

[0015] Since the particles of the target material 30 move in the plasma atmosphere, their mean free path takes a finite value. That is, the farther the position from the target material 30, the fewer particles can reach. In the present embodiment, as already described, from any position on the target material 30, the distance to each point on the main surface AB of the substrate 20 monotonically and continuously increases from point A to point B. Therefore, on the main surface AB, the amount of particles of the target material 30 adhering monotonically and continuously decreases from point A to point B. That is, a thin film having a monotonous and continuous film thickness gradient from point A to point B is formed on the main surface AB.

[0016] FIG. 3 is a diagram showing various positional relationships between the substrate 20 and the target material 30 when the substrate 20 is rotated about point A. Regions (1) and (5) are regions sandwiched between the straight line AP and a straight line passing through point A perpendicular to the straight line AQ (hereinafter referred to as the straight line L1). Regions (2) and (6) are regions sandwiched between the straight line L1 and a straight line passing through point A perpendicular to the straight line AP (hereinafter referred to as the straight line L2). Regions (3) and (7) are regions sandwiched between the straight line L2 and the straight line AQ. Regions (4) and (8) are regions sandwiched between the straight line AQ and the straight line AP.

[0017] Consider the positional relationship between the main surface of the substrate 20 and the target material 30 when a substrate 20 exists in each of regions (1) to (8). When perpendiculars are drawn from points P and Q, which are at both ends of the target material 30, to the line AB passing through points A and B, which are at both ends of the main surface of the substrate 20, the intersection points of these perpendiculars and line AB are the positions where the distance between points P and Q and each point on line AB is minimized. When a substrate exists in regions (3), (4), and (5), the intersection points of the perpendiculars from points P and Q and line AB lie on the extension of line segment AB (main surface AB) on the point A side (in other words, the portion of the target material 30 projected onto the plane containing the main surface AB from a direction perpendicular to that plane does not overlap with the main surface AB, but lies on the extension of the main surface AB). Therefore, when the substrate 20 is in region (3) or (5), the target material 30 is on the main surface AB side (i.e., one of the main surfaces) with respect to the substrate 20, and the distance between points P and Q and each point on the main surface AB increases monotonically from point A to point B, so a thin film with a monotonic and continuous film thickness gradient is deposited on the main surface AB. When the substrate 20 is in region (4), the target material 30 is present on both the main surface AB side and the opposite side of the main surface AB with respect to the substrate 20, so a thin film with a monotonic and continuous film thickness gradient is deposited not only on the main surface AB but also on the main surface opposite to the main surface AB.

[0018] In contrast, if the intersection points of the perpendiculars from points P and Q lie on the extension of line segment AB towards point A and point B, respectively, the distance between point P and each point on the main surface AB increases monotonically from point A to point B, while the distance between point Q and each point on the main surface AB increases monotonically from point B to point A. Therefore, a thin film with a monotonic and continuous film thickness gradient is not necessarily formed on the main surface AB. Also, if at least one of the intersection points of the perpendiculars from points P and Q lies on line segment AB, the distance between point P or point Q and each point on the main surface AB does not increase monotonically from either point A or point B to the other. Therefore, a thin film with a monotonic and continuous film thickness gradient is not necessarily formed on the main surface AB. Consequently, when the substrate 20 is in region (1), (2), (6), (7), or (8), a thin film with a monotonic and continuous film thickness gradient is not necessarily formed on the main surface AB.

[0019] The above can be rephrased as follows: If the main surface AB is in region (1) (let's call it main surface AB1), then the angle between the line AP and the main surface AB1 is 90° or less, and the angle between the line AQ and the main surface AB1 is also 90° or less. Therefore, perpendiculars can be drawn from points P and Q to positions other than points A and B, and the positions obtained by dropping perpendiculars from points P and Q are the positions that are the shortest distances from points P and Q, respectively. In this case, it is not necessarily the case that a thin film with a monotonically continuous film thickness gradient from A to point B1 is deposited on the main surface AB1.

[0020] Assuming that the principal surface AB is in region (2) (let's call it principal surface AB2), the angle between the line AP and principal surface AB2 is 90° or less, and the angle between the line AQ and principal surface AB2 is between 90° and 180°. Therefore, the distance from point Q to each point on principal surface AB2 increases monotonically and continuously from point A to point B2. On the other hand, a perpendicular can be drawn from point P to a position other than point A, and this position is the position with the shortest distance from point P. Thus, it is not guaranteed that a thin film with a monotonically and continuously increasing film thickness gradient from A to point B2 will be deposited on principal surface AB2.

[0021] Assuming that the main surface AB is in region (3) (let's call it main surface AB3), the angle between the line AP and the main surface AB3 is between 90° and 180°, and the angle between the line AQ and the main surface AB3 is also between 90° and 180°. Therefore, the distance from point P and the distance from point Q to each point on the main surface AB3 increase monotonically and continuously from point A to point B3. Consequently, a thin film with a monotonically and continuously increasing film thickness gradient from A to point B3 is formed on the main surface AB3. This embodiment corresponds to the case where the substrate 20 is in region (3).

[0022] Assuming that the main surface AB is in region (4) (let's call it main surface AB4), the angle between the line AP and main surface AB4 is between 90° and 180°. On the other hand, the angle between the line AQ and main surface AB4 is between 180° and 270°. In other words, the angle between the line AQ and the main surface on the opposite side of main surface AB4 is between 90° and 180°. Therefore, the distance from point P to each point on main surface AB4 increases monotonically and continuously from point A to point B4, while particles originating from point Q adhere to the main surface opposite to main surface AB4 on which the film is deposited. That is, in region (4), thin films are deposited on both main surfaces of the substrate.

[0023] The above explains how thin films are deposited in each of regions (1) to (4), and the same considerations apply to regions (5) to (8). That is, in region (5), the angle between the straight line AP and the main surface AB5 is between 90° and 180°, and the angle between the straight line AQ and the main surface AB5 is also between 90° and 180°. Therefore, similar to region (3), a thin film with a monotonic and continuous film thickness gradient from A to point B5 is deposited on the main surface AB5. The case where the substrate 20 is in region (5) also corresponds to this embodiment. On the other hand, in region (6), the angle between the line AP and the main surface AB6 is 90° or less, and the angle between the line AQ and the main surface AB6 is between 90° and 180°. Therefore, similar to region (2), a thin film with a monotonic and continuous film thickness gradient from A to point B6 is not necessarily formed on the main surface AB6. Similarly, in region (7), the angle between the line AP and the main surface AB7 is 90° or less, and the angle between the line AQ and the main surface AB7 is also 90° or less. Therefore, similar to region (1), a thin film with a monotonic and continuous film thickness gradient from A to point B7 is not necessarily formed on the main surface AB7. Furthermore, in region (8), the angle between the line AP and the main surface AB8 is 90° or less, and the angle between the line AQ and the main surface AB8 is also 90° or less. In addition, particles emerging from point Q adhere to the main surface opposite to the main surface AB8 on which the film is formed. Therefore, in region (8), thin films are not necessarily deposited on both main surfaces of the substrate 20, nor are thin films with a monotonic and continuous film thickness gradient from point A to point B8 deposited on both main surfaces.

[0024] The film thickness gradient of the thin film deposited on the substrate 20 changes depending on the distance between the substrate 20 and the target material 30 and the angle of the substrate 20 relative to the target material 30. The distance between the substrate 20 and the target material 30 can be, for example, the distance between the surface of the target material 30 and a plane passing through the center of the substrate 20 and parallel to the surface of the target material 30, the distance between the surface of the substrate 20 and a plane passing through the center of the target material 30 and parallel to the surface of the substrate 20, or the distance between the center of the substrate 20 and the center of the target material 30. The smaller the angle (0° to 90°) between the main surface AB of the substrate 20 and the target material 30, the smaller the difference in the number of target material 30 particles that can be reached at each position on the main surface AB, and the smaller the film thickness gradient. Also, if the distance between the substrate 20 and the target material 30 is too large, the difference in the number of target material 30 particles that can be reached at each position on the main surface AB becomes relatively small, and the film thickness gradient becomes small. Therefore, in this embodiment, in order to deposit a thin film with a large film thickness gradient on the substrate 20, the angle between the substrate 20 and the target material 30 is set to 60° or more. In addition to this condition, it is preferable that the distance between the surface of the target material 30 and a plane passing through the center of the substrate 20 and parallel to the surface of the target material 30 be 100 mm or less, or that the distance between the surface of the substrate 20 and a plane passing through the center of the target material 30 and parallel to the surface of the substrate 20 be 100 mm or less. [Examples]

[0025] An embodiment of the method for manufacturing an optical filter according to the present invention will be described with reference to the drawings. Figure 4 is a diagram showing the arrangement of the substrate and target material in the sputtering apparatus in the embodiment. Figure 5 is a photograph of the arrangement of the substrate and target material in the sputtering apparatus in the embodiment. In this embodiment, two types of disc-shaped target material with a diameter of 101.6 mm (reference numerals 30a and 30b in Figure 4) were prepared. Specifically, tantalum pentoxide (Ta2O5, referred to as 30a) was prepared as the film deposition material for the high refractive index layer, and silicon dioxide (SiO2, referred to as 30b) was prepared as the film deposition material for the low refractive index layer. The substrate 20 is a rectangular flat plate measuring 60 mm × 45 mm × 1.1 mm made of Tempax float (registered trademark, manufactured by Schott). The sputtering apparatus 1 is a Canon Anelva EB1000. The positive electrode 11 is configured to rotate around axis C so that the high refractive index layer and the low refractive index layer can be alternately deposited on the surface of the substrate 20. The centers of the target materials 30a and 30b are at a distance R from axis C. T The substrates are positioned 110 mm apart, with a 45 mm (= W) side of the substrate 20 perpendicular to the target materials 30a and 30b, and the surface to be film-deposited is at a distance R from axis C. S They are positioned at a distance of 37.15 mm. In this embodiment, the direction parallel to the 45 mm long side positioned perpendicular to the target materials 30a and 30b is defined as the specific direction D of the substrate 20. A monitor 14 for monitoring the deposition of a thin film on the surface of the substrate 20 is located near the substrate 20 at a distance R from axis C. M They are positioned 55 mm apart. According to the configuration of the sputtering apparatus 1, the distance H between the surface of the target materials 30a and 30b and the positive electrode 11 is 115 mm, and the distance TS between the surface of the target materials 30a and 30b and the center of the substrate is 90.5 mm.

[0026] Figure 6 shows a screen illustrating the structure of the multilayer film deposited on the substrate in the embodiment. To deposit the multilayer film shown in Figure 6, the sputtering apparatus 1 was operated in the following manner. Note that the film thickness values ​​shown in the figure are the film thickness at the monitoring position. The expected film thickness on the substrate is approximately 0.49 times the original thickness for each layer at the top edge of the substrate and approximately 0.24 times the original thickness at the bottom edge. Substrate temperature: Unheated (room temperature setting) Power: 300W (can be adjusted from 100W to 500W) Inert gas type and pressure: Argon, 0.2 Pa Reactive gas: oxygen

[0027] Figure 7 is a photograph of the optical filter fabricated in the example. The wavelength of the reflected light changes monotonically and continuously along the specific direction D, indicating that the thickness of the multilayer film changes monotonically and continuously. Figure 8 shows the transmittance for each wavelength at various points on the optical filter fabricated in the example. Comparing the transmission spectra at positions ±2.5 mm, ±7.5 mm, and ±17.5 mm along the specific direction D, with the center of the substrate set as 0, the transmission wavelength range changes monotonically and continuously along the specific direction D, which also indicates that the thickness of the multilayer film changes monotonically and continuously.

[0028] [Differentiation] The method for manufacturing an optical filter according to the present invention is not limited to the embodiments and examples, but includes various modifications. For example, in the embodiments, the substrate 20 is placed on the positive electrode 11, but this is not essential, and it may be placed on the wall of the chamber 10 or the like. Also, the inert gas is not limited to argon, and any gas may be used.

[0029] [Aspect] It will be obvious to those skilled in the art that the exemplary embodiments described above are specific examples of the following embodiments.

[0030] (Section 1) A method for manufacturing an optical filter according to one aspect of the present invention is: A flat target material is placed on the negative electrode opposite the positive electrode within the chamber. A flat substrate is positioned in a predetermined location within the chamber such that the angle between the straight line connecting one end of the substrate and the furthest end of the target material from the substrate and one main surface of the substrate is 90° or more and 180° or less, the angle between the straight line connecting that end of the substrate and the closest end of the target material from the substrate and the main surface is 90° or more and 180° or less, and the angle between the surface of the target material and the main surface is 60° or more. The method involves introducing an inert gas into the chamber and applying a predetermined voltage between the positive electrode and the negative electrode to generate a plasma of the inert gas, which is then used to attach the particles of the target material to the main surface of the substrate.

[0031] (Section 4) A method for manufacturing an optical filter according to one aspect of the present invention is: A flat target material is placed on the negative electrode opposite the positive electrode within the chamber. A flat substrate is placed in a predetermined position within the chamber such that the target material is positioned on one of the main surfaces of the substrate, the portion of the target material projected onto the plane from a direction perpendicular to the plane containing the main surface does not overlap with the main surface, and the angle between the surface of the target material and the main surface is 60° or more. The method involves introducing an inert gas into the chamber and applying a predetermined voltage between the positive electrode and the negative electrode to generate a plasma of the inert gas, which is then used to attach the particles of the target material to the main surface of the substrate.

[0032] In the method for manufacturing an optical filter according to paragraph 1, a predetermined voltage is applied between a positive electrode and a negative electrode facing each other in a chamber, causing the inert gas in the chamber to become plasma. When this plasma collides with a target material, particles of the target material are ejected. These ejected target material particles adhere to the surface of the substrate. At this time, since the target material particles travel through the plasma atmosphere, the amount of target material particles adhering to each point on the substrate decreases as the position moves away from the target material. In the present invention, the substrate and the target material are arranged such that the angle between a straight line connecting one end of the substrate and the furthest end of the target material from the substrate and one main surface of the substrate is 90° or more and 180° or less, the angle between a straight line connecting that end of the substrate and the closest end of the target material from the substrate and the main surface is 90° or more and 180° or less, and the angle between the surface of the target material and the main surface is 60° or more. Therefore, the amount of target material particles adhering to one main surface of the substrate decreases as the position moves away from the target material. This creates an optical filter in which the film thickness decreases in the direction away from the target material. Therefore, according to the manufacturing method of the optical filter described in paragraph 1, an optical filter having a thin film with a continuous film thickness gradient in a specific direction of the substrate can be manufactured more easily. Furthermore, in the manufacturing method of the optical filter described in paragraph 4, the substrate and the target material are arranged such that the target material is located on one main surface side of the substrate, the portion of the target material projected onto the plane containing the main surface from a direction perpendicular to the plane containing the main surface does not overlap with the main surface, and the angle between the surface of the target material and the main surface is 60° or more. As a result, the feet of the perpendiculars drawn from each point of the target material to the plane containing the main surface of the substrate are all located on the extension of the main surface, and the amount of target material particles adhering to one main surface of the substrate decreases as the distance from the target material increases. This creates an optical filter in which the film thickness decreases in the direction away from the target material. Therefore, according to the manufacturing method of the optical filter described in paragraph 4, an optical filter having a thin film with a continuous film thickness gradient in a specific direction of the substrate can be manufactured more easily.

[0033] (Article 2) The method for manufacturing an optical filter according to Article 2 is the method for manufacturing an optical filter according to Article 1, wherein the distance between the surface of the target material and a plane passing through the center of the substrate and parallel to the surface of the target material is 100 mm or less.

[0034] (Article 3) The method for manufacturing an optical filter according to Article 3 is the method for manufacturing an optical filter according to Article 1, wherein the distance between the surface of the substrate and a plane passing through the center of the target material and parallel to the surface of the substrate is 100 mm or less.

[0035] According to the manufacturing method of optical filters described in paragraphs 2 and 3, the film thickness gradient of the thin film deposited on the substrate becomes larger. [Explanation of Symbols]

[0036] 1…Sputtering device 10... Chamber 11...Positive electrode 12...Negative electrode 13…Voltage source 14…Monitor 20... Circuit board 30, 30a, 30b… Target material

Claims

1. A flat target material is placed on the negative electrode opposite the positive electrode within the chamber. A flat substrate is positioned in a predetermined location within the chamber such that the angle between the straight line connecting one end of the substrate and the furthest end of the target material from the substrate and one main surface of the substrate is 90° or more and 180° or less, the angle between the straight line connecting that end of the substrate and the closest end of the target material from the substrate and the main surface is 90° or more and 180° or less, and the angle between the surface of the target material and the main surface is 60° or more. By introducing an inert gas into the chamber and applying a predetermined voltage between the positive and negative electrodes, the plasma generated from the inert gas is used to adhere the particles of the target material to the main surface of the substrate. A method for manufacturing optical filters.

2. The method for manufacturing an optical filter according to claim 1, wherein the distance between the surface of the target material and a plane passing through the center of the substrate and parallel to the surface of the target material is 100 mm or less.

3. The method for manufacturing an optical filter according to claim 1, wherein the distance between the surface of the substrate and a plane passing through the center of the target material and parallel to the surface of the substrate is 100 mm or less.

4. A flat target material is placed on the negative electrode opposite the positive electrode within the chamber. A flat substrate is positioned in a predetermined location within the chamber such that the target material is located on one main surface side of the substrate, the portion of the target material projected onto the plane containing the main surface from a direction perpendicular to the plane does not overlap with the main surface, and the angle between the surface of the target material and the main surface is 60° or more. An inert gas is introduced into the chamber, and a predetermined voltage is applied between the positive electrode and the negative electrode to generate a plasma of the inert gas, which is then used to attach the particles of the target material to the main surface of the substrate. A method for manufacturing optical filters.

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