WO2009084319A1 - Optical filter, method for production of the same, and optical device equipped with the same - Google Patents

Abstract

The object is to provide: an optical filter which has a simple structure, which can be produced at low cost, and which has narrow lot-to-lot variations in its optical properties; a method for producing the optical filter; and an optical device. Disclosed is an optical filter (P) comprising a base material (S) and a multi-layered film (M) which can absorb light and which is formed on the surface of the base material (S), wherein the multi-layered film (M) comprises a dielectric film (F) which is composed of two or more films laminated on each other and an absorption film (A) which is formed in at least one space selected from spaces formed between the two or more films constituting the dielectric film (F) and which can absorb light. The dielectric film (F) comprises at least two films laminated on each other, wherein the at least two films are independently selected from a first film (F1) which comprises an oxide, nitride or oxynitride of a metal element (X) and a second film (F2) which comprises an oxide, nitride or oxynitride of a metal element (Y) or an oxide, nitride or oxynitride of an alloy of the metal element (X) and the metal element (Y). The absorption film (A) contains one or both of the metal element (X) and the metal element (Y).

Description

OPTICAL FILTER, MANUFACTURING METHOD THEREOF, AND OPTICAL DEVICE HAVING THE OPTICAL FILTER

The present invention relates to an optical filter, a method for manufacturing the same, and an optical apparatus including the optical filter, and more particularly, an optical filter having a multilayer film in which a dielectric film having a property of transmitting light and an absorption film for absorbing light are laminated. The present invention also relates to a method for manufacturing the same and an optical apparatus including the optical filter.

Optical filters are used for optical devices such as cameras, telescopes, projectors, etc. to transmit the target light. The optical filter is an optical element having a property of transmitting only light having a specific property (for example, a specific wavelength range) and not transmitting other light, and for example, a deflection filter and a color correction filter are known.

One of the optical filters is an absorption type ND (Neutral Density) filter that attenuates transmitted light having a wavelength in the visible region. An ND filter (also referred to as a neutral density filter) is an optical filter having a property of reducing the amount of light transmitted through the filter, and has a property of exhibiting a substantially uniform transmittance over the entire visible range. The ND filter is used for the purpose of reducing the incident light to the lens so as to achieve proper exposure when it is mounted on the front surface of the lens of the camera, for example, when the brightness of the subject is high in outdoor photography or the like.

Conventionally, ND filters have been manufactured by depositing a material made of three or more kinds of metals or metal compounds on a substrate (see, for example, Patent Documents 1 to 4).
The ND filter of Patent Document 1 has a structure in which a dielectric film and a light absorption film are laminated, and two kinds of materials, SiO ₂ and Al ₂ O ₃ , are used as the dielectric film, and the light absorption film Metal Ti and its oxide Ti _x O _y are used.
The ND filter of Patent Document 2 has a structure in which an absorption film, an antireflection layer, and an outermost layer are laminated. Ti _x O _y as an absorption film, Al ₂ O ₃ as an antireflection layer, and MgF as an outermost layer. ₂ is used.
The ND filter of Patent Document 3 has a structure in which a metal film and an Nb film are laminated via a dielectric film, and an Al alloy (Al + Ti) is used as the metal film, and SiO ₂ and Nb films are used as the dielectric film. Nb is used.
The ND filter of Patent Document 4 has a structure in which an absorption multilayer film is formed on the surface of a film substrate and a multilayer antireflection film is formed on the back surface, and SiO ₂ is used as a material for a dielectric layer constituting the absorption multilayer film. Ni-based alloy is used as the material of the metal film layer, SiO ₂ is used as the material of the dielectric layer constituting the multilayer antireflection film, and Ta ₂ O ₅ is used as the material of the metal film layer.

Japanese Patent Laying-Open No. 2005-326687 (Claim 3, paragraphs 0007, 0011, FIG. 1, etc.) JP 2004-212462 (Claims 1 to 3, paragraphs 0011 to 0016, FIG. 14 and others) JP 2003-207608 A ( Claims 1, 3, 7, paragraphs 0020 to 0027, FIG. 1 and others) JP 2006-178395 A (Claims 1 to 3, paragraphs 0020 to 0022, FIG. 2, etc.)

However, in the conventional ND filter, since the metal element constituting the dielectric film is different from the metal element forming the absorption film, at least three kinds of metals are required as raw materials.
For this reason, when manufacturing an ND filter by sputtering etc., for example, in the conventional ND filter, it is necessary to use at least 3 types of target materials, and the cost of the raw material required for manufacturing the ND filter increases. In addition, since the life of the target differs depending on the type of target material, manufacturing management becomes more difficult as more types of targets are used, resulting in higher management costs for product manufacturing and variations in product optical characteristics from lot to lot. May occur, which may lead to a decrease in product accuracy.

An object of the present invention is to provide an optical filter that has a simple structure, is inexpensive to manufacture, and has little variation in optical characteristics from lot to lot, and a method for manufacturing the same.
Another object of the present invention is to provide an optical device that has a low product manufacturing cost and a small variation in accuracy from product to product.

According to the optical filter of the present invention, the above-described problem is an optical filter in which a multilayer film that absorbs light is formed on the surface of a substrate, and the multilayer film includes a dielectric film in which a plurality of films are stacked, And an absorption film having a property of absorbing light, which is formed in at least one place between the plurality of films constituting the dielectric film, and the dielectric film includes an oxide of a first metal element, A first film composed of nitride or oxynitride, and an oxide, nitride or oxynitride of a second metal element different from the first metal element, or the first metal element and the A second film composed of an oxide, a nitride or an oxynitride of an alloy composed of a second metal element, and a structure in which two or more kinds of films are laminated; By containing one or both of the first metal element and the second metal element It is determined.

As described above, since the metal element constituting the dielectric film and the metal element constituting the absorption film are common, the number of types of metal elements constituting the multilayer film is small, and it is constituted by three or more conventional metal elements. The structure of the multilayer film is simpler than that of the optical filter. Further, since the metal elements contained in the dielectric film and the absorption film are the same, the raw materials for forming the dielectric film and the absorption film can be shared.

In this case, the absorption film is composed of a metal composed of one or both of the first metal element and the second metal element, or an incomplete oxide, incomplete nitride, or incomplete oxynitride of the metal. It is preferred that

The metal element is a metal selected from the group consisting of carbon, magnesium, aluminum, silicon, chromium, manganese, iron, cobalt, nickel, zinc, germanium, zirconium, niobium, molybdenum, indium, tin, tantalum, and tungsten. An element is preferable.

Furthermore, the base material is preferably formed of one or more materials selected from the group consisting of glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, and olefin polymer.

According to the method for manufacturing an optical filter of the present invention, the above object is a method for manufacturing an optical filter according to any one of the above, wherein the substrate is formed by sputtering the first target made of the first metal element. Forming a first film by forming a thin film of the first metal element on the surface of the substrate and performing a plasma treatment with oxygen, nitrogen, or a mixed gas of oxygen and nitrogen on the thin film. And sputtering the second target composed of the second metal element or the first target and the second target to form the second metal element or the first target on the surface of the first film. A second film is formed by forming a thin film of an alloy comprising a metal element and the second metal element, and subjecting the thin film to plasma treatment with oxygen, nitrogen, or a mixed gas of oxygen and nitrogen. A dielectric film forming process for forming the dielectric film by repeating the first film forming process and the second film forming process, and the first target and the first film forming process. Sputtering one or both of the two targets to form a thin film on the surface of the dielectric film, and performing plasma treatment with oxygen, nitrogen, or an oxygen / nitrogen mixed gas on the thin film as necessary, This is solved by providing an absorption film forming step of forming the absorption film.

Thus, since the metal element constituting the dielectric film and the metal element constituting the absorption film are common, the number of types of metal elements constituting the multilayer film is small, and the structure of the multilayer film is simplified. Further, since the metal elements contained in the dielectric film and the absorption film are the same, the raw materials for forming the dielectric film and the absorption film can be shared.

In addition, according to the method for manufacturing an optical filter of the present invention, the above-described problem is a method for manufacturing an optical filter according to any one of the above, wherein at least one film formation process region provided at a position spaced apart from each other, and Using a vacuum vessel provided with a reaction process region inside, the substrate is transported into the film formation process region, and a first target made of the first metal element is sputtered onto the surface of the substrate. A thin film of a metal element is formed, the substrate on which the thin film is formed is transported into the reaction process region, and the thin film is plasma-treated with oxygen, nitrogen, or an oxygen / nitrogen mixed gas in the reaction process region. Performing the step of forming the first film, transporting the base material into the film forming process region, and the second target made of the second metal element or the Sputtering one target and the second target to form a thin film of the second metal element or an alloy composed of the first metal element and the second metal element on the surface of the first film, A step of forming the second film by transporting the substrate on which the thin film is formed into the reaction process region, and subjecting the thin film to plasma treatment with oxygen, nitrogen, or a mixed gas of oxygen and nitrogen. A dielectric film forming step of forming the dielectric film by repeating the first film forming step and the second film forming step, and the base material in the film forming process region. A thin film is formed on a surface of the dielectric film by sputtering one or both of the first target and the second target, and the base material on which the thin film is formed is placed in the reaction process region. Transport and required Wherein by performing oxygen plasma treatment with a nitrogen or oxygen-nitrogen mixed gas to the thin film, it is solved by providing an absorption layer formation step of forming the absorbing layer in accordance with the.

As described above, since the target raw material necessary for manufacturing the optical filter is the same as the metal element constituting the dielectric film and the metal element constituting the absorption film, it is composed of three or more kinds of conventional metal elements. The structure of the multilayer film is simplified as compared with the case of manufacturing an optical filter.
Further, since the film formation process region where sputtering is performed and the reaction process region where plasma treatment is performed are separated from each other, the reactive gas in the reaction process region is unlikely to come into contact with the target in the film formation process region. Thereby, abnormal discharge of the target due to the reaction between the target and the reactive gas is unlikely to occur. For this reason, there is no need to increase the temperature of the substrate during film formation, and film formation can be performed at a low temperature and with a high film formation rate. Accordingly, it is possible to efficiently form a film even on a resin base material that is easily deformed at a high temperature.

The above-described problem can be solved by providing the optical filter according to any one of the above according to the optical apparatus of the present invention.

As described above, the optical device of the present invention has an optical filter with a simple multilayer film structure that can be manufactured at low cost and has little variation in accuracy for each product lot. There is also little variation from product to product.

According to the optical filter and the manufacturing method thereof of the present invention, since the metal element constituting the dielectric film and the metal element constituting the absorption film are common, the number of types of metal elements constituting the multilayer film is small, and the multilayer The structure of the film is simplified. Further, since the metal elements contained in the dielectric film and the absorption film are the same, the raw materials for forming the dielectric film and the absorption film can be shared.
Therefore, the types of raw materials for forming the multilayer film are reduced, and manufacturing management at the time of film formation is easy, so that the cost required for manufacturing the optical filter can be reduced. Furthermore, since the structure of the multilayer film is simple, there is little variation in the product accuracy for each production lot, and a high-precision optical filter can be provided.

In addition, according to the optical apparatus of the present invention, the optical filter having a simple multilayer film structure is provided as described above, so that the production cost of the product is low, and variation in accuracy among lots can be reduced. .

It is the schematic diagram which showed the cross-sectional shape of the optical filter. It is explanatory drawing which shows the state which looked at the inside of the thin film forming apparatus from the upper side. 3 is a graph showing the transmittance and reflectance of the optical filter of Example 1. FIG. 6 is a graph showing the transmittance of the optical filter of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thin film formation apparatus 11 Vacuum container 11A Thin film formation chamber 11B Load lock chamber 11C Door 12 Partition wall 13 Rotary drum 14 Partition wall 15 Vacuum pump 18 Drum rotating shaft 19 Partition wall 20 Sputtering means 20A Film formation process area 21a Magnetron sputter electrode 21b Magnetron Sputtering electrode 22a Target 22b Target 23 AC power supply 24 Transformer 30 Sputtering gas supply means 31 Sputtering gas cylinder 32 Mass flow controller 40 Sputtering means 40A Film forming process region 41a Magnetron sputtering electrode 41b Magnetron sputtering electrode 42a Target 42b Target 43 AC power supply 44 Transformer 50 Sputtering gas Supply means 51 Sputtering gas cylinder 52 Mass flow Troller 60 Plasma generating means 60A Reaction process area 61 Case body 62 Dielectric plate 63 Antenna 64 High frequency power supply 65 Matching box 70 Reactive gas supply means 71 Reactive gas cylinder 72 Mass flow controller 73 Inactive gas cylinder 74 Mass flow controller P Optical filter S Base material M multilayer film F dielectric film F1 first film F2 second film A absorption film

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be noted that the members, arrangements, and the like described below are examples embodying the present invention and do not limit the present invention, and it goes without saying that various modifications can be made in accordance with the spirit of the present invention.

FIG. 1 is a schematic view showing a cross-sectional shape of an optical filter, and FIG. 2 is an explanatory view showing the state of the thin film forming apparatus as viewed from above. In FIG. 1, in order to facilitate understanding of the invention, the thickness of the thin film is drawn thicker than the actual thickness.

Specific examples of the optical filter of the present invention include a long wavelength cut filter, a short wavelength cut filter, a band pass filter, and an ND filter. In the following examples, the present invention will be described with reference to an ND filter which is an example of an optical filter.

As shown in FIG. 1, the optical filter P of the present invention includes a base material S and a multilayer film M formed on the surface of the base material S. The multilayer film M includes a dielectric film F having a structure in which a plurality of films are stacked, and an absorption film A formed between the plurality of films constituting the dielectric film F.

The base material S is a member that is formed of a light-transmitting material and serves as a substrate on which the dielectric film F and the absorption film A are attached. In the present embodiment, a disk-shaped substrate S is used as the substrate S, but the shape of the substrate S is not limited to this, and as long as a thin film can be formed on the surface, for example, a lens shape, a cylindrical shape, Other shapes such as an annular shape may be used.

Examples of the material of the substrate S include a material selected from the group consisting of glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, and olefin polymer. Moreover, in order to improve the intensity | strength of the base material S, you may mix glass fiber, carbon fiber, or these mixed fibers in these materials. As specific examples of the olefin polymer, a cycloolefin polymer having excellent transparency, low birefringence, high heat resistance and the like is preferable. Specifically, “ZEONEX” (registered trademark), “ZEONOR” (Registered trademark, both manufactured by Nippon Zeon Co., Ltd.) are preferred.

The dielectric film F is a film having a property of transmitting incident light. The dielectric film F of the present invention has a configuration in which a plurality of films are stacked.
The dielectric film F of the present embodiment is composed of a first film F1 and a second film F2 formed of different materials. The first film F1 is made of an oxide, nitride, or oxynitride of the metal element X (first metal element).

The second film F2 is made of an oxide, nitride, or oxynitride of a metal element Y (second metal element) different from the metal element X. Alternatively, the second film F2 may be made of an oxide, nitride, or oxynitride of an alloy composed of the metal element X and the metal element Y.
In the embodiment shown in the figure, the dielectric film F has a structure composed of only two types of films. However, the dielectric film F of the present invention is formed of only the two types of films described above. However, the film may be formed of three or more kinds of films. For example, as the third film F3, a film using a metal element Z different from the metal elements X and Y as a raw material may be used.

The absorption film A is a film having a property of absorbing a part of incident light. Since the optical filter P of the present embodiment is an ND filter, the absorption film A is formed of a material having a substantially uniform spectral transmittance in the visible region (400 to 700 nm). In this case, the average transmittance of the absorbing film A is generally in the range of 0.01 to 90.0.

The absorption film A is formed of a material containing one or both of the metal element X and the metal element Y. More specifically, examples of the absorption film A include a metal composed of one of the metal element X and the metal element Y, or an alloy composed of these two kinds of metal elements X and Y. Or as the absorption film A, you may be comprised with the incomplete oxide of the metal or alloy mentioned above, incomplete nitride, or incomplete oxynitride.

Specific examples of the metal elements X and Y include carbon (C), magnesium (Mg), aluminum (Al), silicon (Si), chromium (Cr), manganese (Mn), iron (Fe), and cobalt (Co). , Nickel (Ni), zinc (Zn), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), tin (Sn), tantalum (Ta), tungsten (W) An element selected from the group consisting of

The dielectric film F and the absorption film A are designed by selecting a metal element corresponding to the characteristics required for the optical filter P from these metal elements. Specifically, the optical constants of metal element X, metal element Y, and alloy X + Y itself, and incomplete oxide, complete oxide, incomplete nitride, complete nitride, incomplete oxynitride of these metals and alloys Based on the optical constants of the complete oxynitride, a material that matches the optical characteristics required for the dielectric film F and the absorption film A is selected. Then, using the selected material, the multilayer film M is formed by laminating the dielectric film F and the absorption film A on the surface of the substrate S by a film formation technique such as sputtering.

(Optical filter P manufacturing equipment)
Next, an apparatus for manufacturing the optical filter P will be described. The optical filter P of the present invention is preferably manufactured using a thin film forming apparatus in which a film forming process region and a reaction process region described below are separated.

In this thin film forming apparatus, since the film formation process region for sputtering and the reaction process region for processing with a reactive gas are separated, a reactive gas such as nitrogen gas or oxygen gas is present in the film formation process region. It is not introduced. For this reason, the metal on the surface of the target does not react with the reactive gas, and abnormal discharge of the target that occurs when a high-frequency voltage is applied can be suppressed. Conventionally, the temperature of the base material S is increased in order to perform film formation while suppressing abnormal discharge. However, in this thin film forming apparatus, it is not necessary to increase the temperature of the base material S. Film formation can be performed while maintaining a high rate.

In this embodiment, a thin film forming apparatus that performs magnetron sputtering, which is an example of sputtering, is used as the thin film forming apparatus. However, the thin film forming apparatus of the present invention is not limited to such a magnetron sputtering, and uses a magnetron discharge. It is also possible to use another known thin film forming apparatus that performs sputtering such as bipolar sputtering.

In the thin film forming apparatus of the present embodiment, a sputtering process for depositing a thin film thinner than the target film thickness on the surface of the substrate S, and plasma for converting the composition of the thin film by performing a treatment such as oxidation on the thin film An intermediate thin film is formed on the surface of the substrate S by the treatment step, and the final thin film having a desired film thickness is obtained by laminating a plurality of intermediate thin films by repeating this sputtering treatment and plasma treatment a plurality of times. Is formed.

Specifically, the step of forming an intermediate thin film having an average film thickness of about 0.01 to 1.5 nm after composition conversion on the surface of the substrate S by sputtering treatment and plasma treatment is performed each time the rotary drum rotates. By repeating, a final thin film having a target film thickness of several nm to several hundred nm is formed.

Hereinafter, the thin film forming apparatus will be described.
As shown in FIG. 2, the thin film forming apparatus 1 of this embodiment includes a vacuum vessel 11, a rotating drum 13, a sputtering means 20 (first sputtering means), and a sputtering gas supply means 30 (first sputtering gas supply means). ), Sputtering means 40 (second sputtering means), sputtering gas supply means 50 (second sputtering gas supply means), plasma generation means 60, and reactive gas supply means 70 are the main components. .
In the figure, the sputtering means 20, the sputtering means 40, and the plasma generation means 60 are indicated by broken lines, and the sputtering gas supply means 30, the sputtering gas supply means 50, and the reactive gas supply means 70 are indicated by alternate long and short dash lines.

The vacuum vessel 11 is a hollow body made of stainless steel, which is usually used in a known thin film forming apparatus, and has a substantially rectangular parallelepiped shape. The inside of the vacuum vessel 11 is divided into a thin film forming chamber 11A and a load lock chamber 11B by an openable / closable door 11C.

The rotary drum 13 is a cylindrical member for holding the base material S, and has a function as a substrate holding means. The rotating drum 13 is provided with a drum rotating shaft 18 that is coaxially connected to an output shaft of a motor (not shown).

On the inner wall of the vacuum vessel 11, partition walls 12, 14 and 19 are erected toward the rotary drum 13. The partition walls 12, 14, and 19 of the present embodiment are all the same stainless steel members as the vacuum vessel 11. These partition walls 12, 14, 19 are each composed of a flat plate member arranged one by one on the top, bottom, left, and right, and project vertically from the inner wall surface of the vacuum vessel 11 toward the rotary drum 13. The outer peripheral surface of 13 is surrounded from four sides.

On the side wall of the vacuum vessel 11, projecting wall surfaces having a convex cross section projecting outward at two locations facing each other across the drum rotating shaft 18 are formed. Sputtering means 20 and sputtering means are respectively formed on the projecting wall surfaces. 40 is provided. The film forming process area 20 </ b> A is formed in an area surrounded by the inner wall surface of the vacuum vessel 11, the partition wall 12, the outer peripheral surface of the rotary drum 13, and the sputtering means 20. The film formation process area 40 </ b> A is formed in an area surrounded by the inner wall surface of the vacuum vessel 11, the partition wall 14, the outer peripheral surface of the rotary drum 13, and the sputtering means 40. In these film forming process regions 20A and 40A, a sputtering process for attaching a film raw material to the surface of the substrate S is performed.

Further, a projecting wall surface having a convex cross section projecting outward is also formed on the side wall of the vacuum vessel 11 which is separated from both the film forming process region 20A and the film forming process region 40A by about 90 ° about the drum rotation shaft 18. The plasma generating means 60 is provided on the protruding wall surface. The reaction process region 60 </ b> A is formed in a region surrounded by the inner wall surface of the vacuum vessel 11, the partition wall 19, the outer peripheral surface of the rotary drum 13, and the plasma generating means 60. In the reaction process region 60A, the plasma processing is performed on the film raw material adhering to the surface of the substrate S.

(Deposition process area 20A)
Hereinafter, the film forming process region 20A will be described.
Sputtering means 20 is installed in the film forming process region 20A. The sputtering means 20 includes a pair of magnetron sputter electrodes 21a and 21b, targets 22a and 22b held by the magnetron sputter electrodes 21a and 21b, an AC power source 23 that supplies power to the magnetron sputter electrodes 21a and 21b, and a magnetron. And a transformer 24 as power control means for adjusting the amount of power supplied to the sputter electrodes 21a and 21b.

The wall surface of the vacuum vessel 11 protrudes outward, and magnetron sputter electrodes 21a and 21b are disposed on the inner wall of the protruding portion so as to penetrate the side wall. The magnetron sputter electrodes 21a and 21b are fixed to the vacuum vessel 11 at the ground potential via an insulating member (not shown).

The magnetron sputter electrodes 21a and 21b have a structure in which a plurality of magnets are arranged in a predetermined direction. The magnetron sputter electrodes 21a and 21b are connected to an AC power source 23 via a transformer 24, and are configured so that an alternating electric field of 1 to 100 kHz can be applied to both electrodes.

The targets 22a and 22b are formed by forming a film raw material into a flat plate shape, and are detachably held by the magnetron sputtering electrodes 21a and 21b so as to face the side surfaces of the rotating drum 13 as described later. The materials of the targets 22a and 22b are appropriately selected according to the optical characteristics required for the dielectric film F and the absorption film A.

A sputtering gas supply means 30 for supplying a sputtering gas such as argon is provided outside the film forming process region 20A. The sputtering gas supply means 30 includes a sputtering gas cylinder 31 as a sputtering gas storage means and a mass flow controller 32 as a sputtering gas flow rate adjusting means for adjusting the flow rate of the sputtering gas as main components. Examples of the sputtering gas include inert gases such as argon and helium.

The mass flow controller 32 is a device that adjusts the gas flow rate. The sputtering gas from the sputtering gas cylinder 31 is introduced into the film forming process region 20A with the flow rate adjusted by the mass flow controller 32.

When the sputtering gas is supplied from the sputtering gas supply means 30 to the film forming process region 20A, the periphery of the targets 22a and 22b becomes an inert gas atmosphere. In this state, when an alternating electrode is applied from the AC power source 23 to the magnetron sputtering electrodes 21a and 21b, a part of the sputtering gas around the targets 22a and 22b emits electrons and is ionized.

Since a magnetic field is generated on the surfaces of the targets 22a and 22b by the magnets arranged on the magnetron sputter electrodes 21a and 21b, the electrons circulate in a magnetic field generated near the surfaces of the targets 22a and 22b while drawing a toroidal curve. To do. A strong plasma is generated along the electron trajectory, and ions of the sputtering gas are accelerated toward the plasma and collide with the targets 22a and 22b, whereby atoms and particles ( targets 22a and 22b on the surfaces of the targets 22a and 22b). When silicon is silicon, silicon atoms and silicon particles) are knocked out. These atoms and particles are film raw material that is a raw material for the thin film, and adhere to the surface of the substrate S to form a thin film.

(Deposition process area 40A)
Hereinafter, the film forming process area 40A will be described.
Sputtering means 40 is installed in the film forming process area 40A. As with the sputtering means 20, the sputtering means 40 supplies power to the pair of magnetron sputtering electrodes 41a and 41b, the targets 42a and 42b held by the magnetron sputtering electrodes 41a and 41b, and the magnetron sputtering electrodes 41a and 41b, respectively. AC power supply 43 that performs the above and a transformer 44 that serves as a power control means for adjusting the amount of power supplied to the magnetron sputtering electrodes 41a and 41b. Since the magnetron sputter electrodes 41a and 41b, the AC power supply 43, and the transformer 44 are the same as the magnetron sputter electrodes 21a and 21b, the AC power supply 23, and the transformer 24, respectively, detailed description thereof is omitted.

The targets 42a and 42b are formed of a metal element material different from the targets 22a and 22b. The metal elements of the targets 22a and 22b and the targets 42a and 42b are appropriately selected according to the characteristics required for the dielectric film F and the absorption film A of the optical filter P to be manufactured. For example, when the first film F1 of the dielectric film F is silicon oxide (SiO ₂ ), the second film F2 is niobium pentoxide (Nb ₂ O ₅ ), and the absorption film A is metal niobium (metal Nb), Metallic silicon (Si) is used for the targets 22a and 22b, and metallic niobium (Nb) is used for the targets 42a and 42b.

A sputtering gas supply means 50 for supplying a sputtering gas such as argon is provided outside the film forming process region 40A. The sputtering gas supply means 50 includes a sputtering gas cylinder 51 as a sputtering gas storage means and a mass flow controller 52 as a sputtering gas flow rate adjusting means for adjusting the flow rate of the sputtering gas as main components. The sputtering gas cylinder 51 and the mass flow controller 52 have the same configuration as the sputtering gas cylinder 31 and the mass flow controller 32, respectively, and thus detailed description thereof is omitted.

(Reaction process area 60A)
Subsequently, the reaction process region 60A will be described. As described above, in the reaction process region 60A, the film raw material adhered to the surface of the substrate S in the film formation process region 20A is subjected to plasma treatment to form a complete reaction product or an incomplete reaction product of the film raw material.

The plasma generating means 60 is provided facing the reaction process region 60A. The plasma generating means 60 of this embodiment includes a case body 61, a dielectric plate 62, an antenna 63, a high frequency power supply 64, and a matching box 65.

The case body 61 is a plate member made of stainless steel fixed so as to close the opening formed in the wall surface of the vacuum vessel 11. By fixing the case body 61 to the wall surface of the vacuum vessel 11, the plasma generating means 60 is attached to the wall surface of the vacuum vessel 11.

The dielectric plate 62 is a plate-like dielectric member fixed to the case body 61. The dielectric plate 62 of this embodiment is made of quartz, but may be made of a ceramic material such as Al ₂ O ₃ . By fixing the dielectric plate 62 to the case body 61, an antenna accommodating chamber is formed in a region surrounded by the case body 61 and the dielectric plate 62.

The dielectric plate 62 is installed toward the reaction process region 60A. At this time, the antenna accommodation chamber is separated from the inside of the vacuum vessel 11. In other words, the antenna accommodating chamber and the inside of the vacuum vessel 11 form an independent space in a state of being partitioned by the dielectric plate 62. Further, the antenna housing chamber and the outside of the vacuum vessel 11 form an independent space in a state of being partitioned by the case body 61.
The antenna accommodating chamber communicates with the vacuum pump 15 through a pipe, and the inside of the antenna accommodating chamber can be evacuated by being evacuated by the vacuum pump 15 to be in a vacuum state.

The antenna 63 is supplied with electric power from the high-frequency power supply 64 to generate an induction electric field in the reaction process region 60A and generate plasma in the reaction process region 60A. In the present embodiment, an AC voltage having a frequency of 1 to 27 MHz is applied from the high frequency power source 64 to the antenna 63 to generate reactive gas plasma in the reaction process region 60A.

The antenna 63 is connected to a high frequency power supply 64 through a matching box 65 that accommodates a matching circuit. A variable capacitor (not shown) is provided in the matching box 65 so that the power supplied from the high frequency power supply 64 to the antenna 63 can be changed.

Reactive gas supply means 70 is provided outside the reaction process region 60A. The reactive gas supply means 70 includes a reactive gas cylinder 71 that stores the reactive gas, a mass flow controller 72 that adjusts the flow rate of the reactive gas supplied from the reactive gas cylinder 71, and an inert gas cylinder that stores the inert gas. 73 and a mass flow controller 74 for adjusting the flow rate of the inert gas supplied from the inert gas cylinder 73 as main components.

The reactive gas cylinder 71 and the inert gas cylinder 73 can employ the same apparatus as the sputtering gas cylinder 31 in the film forming process region 20A. The mass flow controller 72 and the mass flow controller 74 can employ the same apparatus as the mass flow controller 32 in the film forming process region 20A.

When power is supplied from the high frequency power supply 64 to the antenna 63 in a state where the reactive gas or the inert gas is introduced from the reactive gas cylinder 71 into the reaction process region 60A through the pipe, the antenna 63 in the reaction process region 60A is faced. Plasma is generated in the region. As a result, the film raw material formed on the surface of the substrate S is plasma-treated with the reactive gas.

In the thin film forming apparatus 1 of the present embodiment, the film forming process region 20A for supplying the film raw material by sputtering and the reaction process region 60A for reacting the film raw material and the reactive gas in the vacuum container 11 are thus provided. Since it is formed in a separated state at a separated position, there is a disadvantage that abnormal discharge occurs due to the reaction between the targets 22a and 22b and the reactive gas as in the case of using a conventional general reactive sputtering apparatus. Hard to occur. Therefore, the reaction between the film raw material and the reactive gas can be promoted by increasing the supply amount of the reactive gas in the reaction process region 60A or increasing the plasma generation density.

Therefore, there is no need to improve the reactivity by increasing the temperature of the substrate S as in the prior art, and it is possible to perform the reaction sufficiently at a low temperature. Thereby, for example, it becomes possible to sufficiently react even with the base material S formed from a plastic resin having low heat resistance, and the optical filter P with good film quality can be manufactured.

(Method for manufacturing optical filter P)
Next, the case where the multilayer film M in which the dielectric film F and the absorption film A are formed on the resin base material S is formed using the thin film forming apparatus 1 will be described. In the following example, silicon oxide (SiO ₂ ) is formed as the first film F 1 of the dielectric film F, niobium pentoxide (Nb ₂ O ₅ ) is formed as the second film F 2, and metal niobium as the absorption film A (Metal Nb) is formed.

First, the base material S is set on the rotary drum 13 and accommodated in the vacuum container 11. Then, with the inside of the vacuum vessel 11 sealed, the inside of the vacuum vessel 11 is brought to a high vacuum state of about 10 ⁻¹ to 10 ⁻⁵ Pa using the vacuum pump 15. Metallic silicon is used as the material for the targets 22a and 22b, and metallic niobium is used as the material for the targets 42a and 42b.

Subsequently, a dielectric film F is formed on the surface of the substrate S. First, the rotating drum 13 is rotated to move the substrate S into the film forming process region 20A (substrate transporting step), and the targets 22a and 22b are sputtered in the film forming process region 20A to form metal silicon on the surface of the substrate S. A thin film is formed (sputtering step). Next, the rotating drum 13 is rotated to transport the substrate S to the reaction process region 60A (substrate transporting process). Prior to this transfer, a reactive gas is introduced into the reaction process region 60A in advance. Then, a reactive gas plasma is generated inside the reaction process region 60A to react with the metal of the thin film, thereby converting the metal silicon into silicon oxide (plasma treatment step).
Then, the first drum F1 is formed by rotating the rotating drum 13 and repeating the above-described sputtering step and plasma treatment step a plurality of times, and continuing the film formation until a predetermined film thickness is obtained (the first film F1). Film formation step).

Next, the second film F2 is formed on the surface of the first film F1. First, the substrate S is transported into the film forming process region 40A, and the targets 42a and 42b are sputtered to form a thin film made of metallic niobium on the surface of the first film F1 (sputtering step). The substrate S is transported to the reaction process region 60A by the rotation of the rotary drum 13. A reactive gas plasma is generated inside the reaction process region 60A to react with the metal of the thin film to convert the metal niobium into niobium pentoxide (plasma processing step).
Then, by rotating the rotating drum 13, the above-described sputtering process and plasma treatment process are repeated a plurality of times, and the second film F2 is formed by continuing the film formation until a predetermined film thickness is obtained (second film). Film formation step).
Further, the first film formation process and the second film formation process described above are repeated until a desired number of films are obtained, thereby forming a part of the dielectric film F (dielectric film formation process).

Next, an absorption film A is formed on the surface of the dielectric film F. First, the base material S is transported into the film forming process region 40A, and the targets 42a and 42b are sputtered to form a thin film made of metal niobium on the surface of the dielectric film F (sputtering step). Then, the rotating drum 13 is rotated and the above-described sputtering process is repeated a plurality of times, and the film formation is continued until a predetermined film thickness is obtained, thereby forming the absorption film A (absorption film formation process).

Further, the dielectric film forming process is repeated again on the base material S on which the absorption film A is formed, and the dielectric film F is formed on the surface of the absorption film A. Thereby, the multilayer film M having the desired optical characteristics is finally formed. After the film formation is completed, the rotation of the rotating drum 13 and the gas supply are stopped, and the rotating drum 13 is transferred to the load lock chamber 11B. Thereafter, the load lock chamber 11 </ b> B is opened to the atmosphere, and the substrate S is removed from the rotating drum 13.

As described above, the thin film forming apparatus 1 according to the present embodiment includes the film forming process region 20A and the film forming process region 40A to which film raw material materials made of different materials are attached. Even if different metal materials are laminated, it is not necessary to release the vacuum state of the vacuum vessel 11 and replace the target. For this reason, it is possible to shorten the tact time required for manufacturing the optical filter P.

In the above-described example, the reactive gas and unreacted metallic niobium are formed as the absorbing film A. However, when an incomplete reaction product of metallic niobium and reactive gas is used as the absorbing film A, a sputtering process is performed. The subsequent substrate S is transported to the reaction process region 60A, and plasma treatment with reactive gas is performed on the metal niobium (plasma treatment step).

In the above example, only niobium is used as the metal element constituting the second film F2. However, an alloy composed of two kinds of metal elements may be used as the raw material of the second film F2. In this case, a thin film of an alloy made of two kinds of metal elements can be formed on the surface of the substrate S by sputtering the targets 22a and 22b and the targets 42a and 42b made of different materials.

Next, an example in which the optical filter P was actually manufactured will be described. In any of the examples, the optical filter P was formed using the thin film forming apparatus 1 shown in FIG. The optical filter P was formed under various conditions shown in each example, and the transmittance at 400 to 700 nm was measured.

(Example 1: ND filter)
An optical filter P (ND filter) was prepared using silicon and niobium metals as materials for the dielectric film F and the absorption film A, respectively, so that the transmittance was about 12%. Such an ND filter is required to have a characteristic in which the transmission intensity in the visible range (400 to 700 nm) is equally attenuated, and is used for “squeezing” of a camera, for example.
The film forming conditions are as follows.
<Film formation conditions>
Dielectric film F (first film F1) .. silicon oxide (SiO ₂ )
Dielectric film F (second film F2) ..Niobium pentoxide (Nb ₂ O ₅ )
Absorption film A (2nd layer, 5th layer) .. Metal niobium (metal Nb)
Targets 22a, 22b ... Metallic silicon targets 42a, 42b ... Metal niobium power (metallic silicon) ... 4.4W / cm < ² >
Power (metal niobium) 2.7 W / cm ²
Supply gas ( deposition process area 20A, 40A). Argon gas Supply gas (reaction process area 60A) Oxygen gas pressure 0.35Pa

FIG. 3 shows the results of measuring the transmittance and reflectance of the ND filter of Example 1. As shown in this figure, the ND filter of Example 1 was found to exhibit a substantially flat transmittance characteristic of about 12% within the visible wavelength range of 400 to 700.

(Example 2: ND Green filter)
An optical filter P (ND Green filter) that transmits light around a green wavelength range was prepared using a material made of silicon and niobium metal in the same manner as in Example 1. Such an ND Green filter is used, for example, for “dark green” illumination for a display memory in a microscope or for correcting RGB color tone in a projector using a color wheel.
The film forming conditions are as follows.
<Film formation conditions>
Dielectric film F (first film F1) .. silicon oxide (SiO ₂ )
Dielectric film F (second film F2) ..Niobium pentoxide (Nb ₂ O ₅ )
Absorption film A (13th layer) ・ ・ Metal niobium (metal Nb)
Targets 22a, 22b ... Metallic silicon targets 42a, 42b ... Metal niobium power (metallic silicon) ... 4.4W / cm < ² >
Power (metal niobium) 2.7 W / cm ²
Supply gas ( deposition process area 20A, 40A) ... Argon gas Supply gas (reaction process area 60A) ... Oxygen gas pressure ... 0.35Pa

In FIG. 4, the result of having measured the transmittance | permeability of the ND Green filter of Example 2 is shown. As shown in this figure, the ND Green filter of Example 2 exhibits a substantially flat transmittance characteristic of about 15% within the wavelength range of 480 to 580 in the visible region, and almost zero transmittance in other wavelength ranges. I found out that
As described above, from the results of Examples 1 and 2, it was found that the optical filter P having desired optical characteristics can be manufactured even when the multilayer film M is formed using two kinds of metal elements as raw materials. .

Claims (7)

1. An optical filter in which a multilayer film that absorbs light is formed on the surface of a substrate,
   The multilayer film includes a dielectric film in which a plurality of films are stacked, and an absorption film having a property of absorbing light, which is formed in at least one position between the plurality of films constituting the dielectric film. ,
   The dielectric film is
   A first film composed of an oxide, nitride or oxynitride of a first metal element;
   An oxide, nitride or oxynitride of a second metal element different from the first metal element, or an oxide, nitride or acid of an alloy comprising the first metal element and the second metal element A second film composed of nitride, and a structure in which two or more kinds of films are laminated,
   The absorption film is
   An optical filter comprising one or both of the first metal element and the second metal element.
2. The absorption film is made of a metal composed of one or both of the first metal element and the second metal element, or an incomplete oxide, incomplete nitride or incomplete oxynitride of the metal. The optical filter according to claim 1.
3. The metal element is a metal element selected from the group consisting of carbon, magnesium, aluminum, silicon, chromium, manganese, iron, cobalt, nickel, zinc, germanium, zirconium, niobium, molybdenum, indium, tin, tantalum, and tungsten. The optical filter according to claim 1, wherein the optical filter is provided.
4. 4. The substrate according to claim 1, wherein the substrate is made of one or more materials selected from the group consisting of glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, and olefin polymer. The optical filter according to item.
5. A method for producing an optical filter according to any one of claims 1 to 4,
   Sputtering a first target made of the first metal element to form a thin film of the first metal element on the surface of the substrate;
   A first film forming step of forming the first film by performing plasma treatment with oxygen, nitrogen, or an oxygen / nitrogen mixed gas on the thin film;
   Sputtering the second target composed of the second metal element or the first target and the second target to form the second metal element or the first metal element on the surface of the first film Forming a thin film of an alloy comprising the second metal element;
   Performing a second film formation step of forming the second film by performing a plasma treatment with oxygen, nitrogen, or a mixed gas of oxygen and nitrogen on the thin film,
   A dielectric film forming step of forming the dielectric film by repeating the first film forming step and the second film forming step;
   Sputtering one or both of the first target and the second target to form a thin film on the surface of the dielectric film,
   An absorption film forming step of forming the absorption film by performing plasma treatment with oxygen, nitrogen or oxygen / nitrogen mixed gas on the thin film as necessary, and a method for producing an optical filter, comprising: .
6. A method for producing an optical filter according to any one of claims 1 to 4,
   Using a vacuum vessel provided with a deposition process region and a reaction process region provided at least one at a position spaced apart from each other,
   Transporting the substrate into the deposition process area;
   Sputtering a first target made of the first metal element to form a thin film of the metal element on the surface of the substrate,
   Transporting the substrate on which the thin film is formed into the reaction process region;
   Forming the first film by subjecting the thin film to plasma treatment with oxygen, nitrogen, or a mixed gas of oxygen and nitrogen in the reaction process region;
   Transporting the substrate into the deposition process area;
   Sputtering the second target composed of the second metal element or the first target and the second target to form the second metal element or the first metal element on the surface of the first film Forming a thin film of an alloy comprising the second metal element;
   Transporting the substrate on which the thin film is formed into the reaction process region;
   Performing a plasma treatment with oxygen, nitrogen or oxygen / nitrogen mixed gas on the thin film, and performing the step of forming the second film,
   A dielectric film forming step of forming the dielectric film by repeating the first film forming step and the second film forming step;
   Transporting the substrate into the deposition process area;
   Sputtering one or both of the first target and the second target to form a thin film on the surface of the dielectric film,
   Transporting the substrate on which the thin film is formed into the reaction process region;
   An absorption film forming step of forming the absorption film by performing plasma treatment with oxygen, nitrogen or oxygen / nitrogen mixed gas on the thin film as necessary, and a method for producing an optical filter, comprising: .
7. An optical apparatus comprising the optical filter according to any one of claims 1 to 4.

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