JP2010049137A - Dimmer filter and film forming method and film forming device of dimmer filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably provide a dimmer filter superior in reflection characteristic without irregularities by forming a gradation region layer in which film thickness gradually decreases when forming a film layer corresponding to optical characteristics on a transparent substrate. <P>SOLUTION: The dimmer filter comprises: the substrate; and a gradation layer constituted of a metal film layer formed in a laminated layer state by sputtering a different substance on the substrate and a dielectric film layer. The metal film layer and the dielectric film layer have gradient angles to the substrate. The gradient angle of the dielectric film layer is smaller than the gradient angle to the substrate of the metal film layer and substantially uniform film thickness is formed in a metal film layer forming region. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a neutral density filter that adjusts the amount of light of an imaging device such as a camera, a film formation method thereof, and a film formation apparatus, and more particularly, a gradation film formation method and film formation in which the light reduction characteristics of the light reduction filter are continuously and gradually reduced. Relates to the device.

In general, this type of neutral density filter is widely used in an imaging light quantity diaphragm device. In this neutral density filter, a thin film having excellent light absorption characteristics is formed on a resin substrate. This neutral density filter is formed with a thin film with a uniform single concentration as a whole, when it is divided into several regions with different concentrations, and with a gradation thin film whose concentration distribution changes continuously. The case of forming a film is known.

In recent years, as the resolution of an imaging apparatus increases, image quality degradation such as image blur due to the influence of diffracted light tends to be noticeable when the amount of light is reduced under bright subject conditions. Thus, for example, as disclosed in Patent Document 1, it is proposed to attach a neutral density filter to an aperture blade that adjusts the amount of light to suppress a diffraction phenomenon that occurs at the time of a small aperture. There has been proposed a gradation filter in which the density (light transmittance) continuously decreases gradually toward the aperture diameter when the neutral density filter is below a certain aperture value. By using such a filter, for example, when a diaphragm blade is narrowed down, image defects due to light interference are prevented from occurring.

Conventionally, in such a neutral density filter, as disclosed in Patent Document 1, for example, a thin film having high light absorption is formed on a transparent or translucent substrate. The thin film has an equal density region where the film thickness is equal and the light attenuation rate is uniform, and a gradation region where the film thickness decreases linearly. Further, Patent Document 2 discloses that several layers of a light-absorbing metal film and a dielectric film are laminated in a laminated manner. A film-forming structure is known in which light is attenuated by a metal film and light transmission is adjusted by a dielectric film to prevent reflection at the same time.

The metal film layer is made of niobium, chromel, titanium or the like, and the dielectric film layer is made of an oxide such as silicon or aluminum, nitride, fluoride or the like. The uppermost layer of the film layer is covered with a hard and water-repellent film layer such as magnesium fluoride. These film layers are configured such that the film thickness gradually decreases linearly in the gradation region. Although it is configured to attenuate light with such a film structure and adjust the light transmission amount, there is a problem that a sufficient antireflection effect cannot be obtained if the film gradient of the dielectric film is large.

On the other hand, as a method for forming such a gradation region layer, it is widely used that the gradation region layer is formed by a vacuum evaporation apparatus. For example, the above-mentioned Patent Document 2 discloses that a gradation region layer is formed with a vapor deposition film.

Patent Document 2 proposes a film forming method in which a substrate is mounted on a vacuum evaporation apparatus, and an evaporation component is heated and evaporated while rotating the stage to form a film on the substrate. It is disclosed that a mask plate having a mask opening is provided between the evaporation source and the substrate, and an equi-concentration region is formed on the substrate facing the mask opening, and a gradation region is formed in the periphery thereof.

And the production | generation mechanism which forms a gradation area | region layer using the vacuum evaporation apparatus of the patent document 2 is shown to FIG. 1A and FIG. 1B. In this method, a large number of substrates 50 are mounted on the deposition stage 51 in a radial manner as shown in FIG. 1A. A mask 53 having a film formation opening 52 is arranged at a position spaced from the stage, and the stage 51 and the mask 53 are equipped in the apparatus so as to rotate about the same axis X. Therefore, the vapor deposition source 54 is disposed at a position Y that is offset from the rotation axis X by a predetermined amount. In this state, the stage 51 is rotated to evaporate film forming components from the vapor deposition source. Then, a part of the film forming component emitted from the vapor deposition source adheres to the substrate from the mask opening 52 and the other is blocked by the mask 53.

When the stage 51 and the mask 53 are rotated with such a structure, a geometrical relationship as shown in FIG. That is, when the vapor deposition source 54 is expressed as a point evaporation source with respect to the substrate 50 mounted on the stage 51, the vapor deposition source 54 rotates in an arc locus inclined at a predetermined angle θ as shown in FIG. 2A. The inclination angle θ coincides with the angle θ of the substrate 50 mounted on the dome-shaped stage 51. Therefore, the vapor deposition component is projected from the opening of the mask 53 to the substrate 50 from the evaporation source 54 along an arc locus inclined at an angle θ. Therefore, a film layer in which the film thickness d gradually changes from d1 to d2 as shown in FIG. 2B is formed on the substrate. With this film layer, the transmitted light amount has a high transmittance in the dark portion (d1) and the light transmittance in the light portion (d2).

In other words, when generating a conventional gradation area layer, a mask plate is provided between the substrate and the target in the vapor deposition tank, and the film forming components are evaporated from a position inclined by a predetermined angle α with respect to the mask opening. Forming. Therefore, although not disclosed in Patent Document 2, the distance L1 between the target and the mask plate is set to be sufficiently larger than the distance d between the mask plate and the substrate, and the vapor deposition component projected from the target is like parallel rays. It is controlled to draw a straight line. As a result, the geometrically formed film thickness changes linearly as shown in FIG. 2B.
JP-A-5-281593 JP 2005-345746 A

As described above, conventionally, the gradation filter is formed into a film by a vapor deposition apparatus as described in Patent Document 2 described above. However, this method has a problem that when a plurality of filter materials are generated at the same time, the film thickness differs for each material and the yield is extremely bad. That is, when a filter having a predetermined attenuation rate is mass-produced, individual attenuation characteristics are different, and there is a defect that optical characteristics vary.

This non-uniform film thickness has the disadvantage that the filter created by the method of the above-mentioned Patent Document 2 when the ideal film thickness is expressed by a broken line in FIG. 6A causes variations in optical characteristics as shown by the chain line in FIG. is there. As described above, in the gradation filter film forming method using the conventional vapor deposition apparatus, there are known problems that a large variation in optical characteristics of individual materials occurs when a plurality of substrates are produced simultaneously, and that the gradation region layer does not attenuate linearly. Yes. Therefore, it is said that the production requires advanced experience and know-how such as vacuum state management in the tank, vapor deposition condition management of vapor deposition components, and float condition management of vapor deposition components in the tank.

Moreover, it seems that the reason for the variation in optical characteristics for each material in the film forming method disclosed in Patent Document 2 is as follows. First, the substrate 50 shown in FIGS. 1A and 1B is mounted on a dome-shaped stage 51 in a state where the angles θ are different from each other. The mask plates 53 corresponding to the respective substrates 50 are arranged at the same angle θ. The evaporation source 54 is arranged at a position offset from the rotation center by a predetermined angle α with respect to the stage on which the substrate 50 and the mask plate 53 are mounted.

Accordingly, the vapor deposition components scattered from the vapor deposition source 54 pass through the mask plate 53 at different angles to form a film on the substrate. Therefore, film layers having different widths are formed on the substrate 50a, the substrate 50b, and the substrate 50c. At the same time, in the stage 51 rotating around the rotation axis X, the components 50a, 50b, and 50c have different illustrated distances L1, L2, and L3 from the evaporation source 54. Accordingly, the film thicknesses formed on both the substrates are naturally different, and this is analyzed as the cause of the variation in the optical characteristics for each material.

Next, the reason why the film layer is not linearly attenuated in the film forming method disclosed in Patent Document 2 is considered to be as follows. In the film forming method of this document, as shown in FIG. 1, gradation region layers are formed before and after the direction in which the substrate 50 and the mask plate 53 rotate. For this reason, the vapor deposition component emitted from the evaporation source 54 adheres to the gradation area layer while rotating on the substrate 50. In such film formation, the atmosphere in the chamber changes as the substrate 50 rotates. Due to this change, the deposited film thickness becomes unstable, and the film thickness as geometrically formed cannot be obtained. At the same time, in the film forming method in which the vapor deposition material is heated and vapor deposited in the vapor deposition tank of the same document, the film thickness of the film formation material is large and the particle size of the vapor deposition component is large. It is analyzed that the cause is very different. At the same time, for example, when silicon dioxide is used as the vapor deposition component, the component deposited from the vapor deposition source 54 is generated in an unstable state such as “SiO ₂ ” or “SiO” or an intermediate oxide thereof. Such an oxide shift is randomly generated by the film forming means, so that it is considered that a stable film layer cannot be formed.

In view of this, the present inventor paid attention to the generation of a gradation filter by using a known reactive sputtering apparatus (for example, Japanese Patent Application Laid-Open No. 11-279757). At the same time, the inventors have devised to provide a film forming method capable of suppressing the deterioration of the antireflection effect due to the change in the film thickness of the gradation filter.

In the present invention, when forming a film layer according to optical characteristics on a transparent substrate, a gradation region layer whose film thickness gradually decreases can be formed on a plurality of substrates at the same time without variation. It is possible to gradually reduce the thickness of the region layer linearly, and at the same time, to provide a neutral density filter film forming method, a manufacturing apparatus, and a neutral density filter using the same. It is a difficult issue.

Another object of the present invention is to improve the characteristics of a neutral density filter capable of obtaining a sufficient antireflection effect over the entire gradation region layer.

To achieve the above object, the present invention employs the following configuration.

First, the neutral density filter of the present invention is formed by forming a gradation layer composed of a substrate, a metal film layer formed by stacking different materials on the substrate and a dielectric film layer, and the metal film. Both the dielectric layer and the dielectric film layer have a gradient angle with respect to the substrate, and the gradient angle of the dielectric film layer is smaller than the gradient angle of the metal film layer with the substrate, and the metal film layer is formed. It is characterized in that a substantially uniform film thickness is formed in the region.

Next, in the neutral density filter film forming method of the present invention, at least first and second targets made of different substances are sputtered in the film forming chamber to form a predetermined film forming gap with respect to the substrate. A method of forming a neutral density filter comprising forming a metal film layer made of the first target material and a dielectric film layer made of the second target material on the substrate through an opening, (1) The substrate is mounted on a cylindrical rotating drum disposed in the film forming chamber, and (2) a predetermined plate is formed between the substrate and the mask plate having the mask opening on the rotating drum. (3) The first target is a plate-like material and is substantially parallel to the substrate surface, and the sputter region central part of the first target is rotated with the central part of the mask opening. Do (4) the second target is a plate-like material that is substantially parallel to the substrate surface and is located at the center of the sputter region of the second target. The part is disposed at a position facing the substrate at a position appropriately displaced in a direction perpendicular to the rotation direction of the rotary drum with respect to the normal line connecting the center of the mask opening and the rotation center of the rotary drum, and the rotary drum By applying a sputtering voltage to the first and second targets while rotating the substrate, the substrate is generated in the film formation gap from the mask opening of the mask plate in a direction orthogonal to the rotation direction of the rotating drum. Due to the diffusion of the sputtered particles, the metal film layer whose film thickness gradually decreases and the gradation layer which is composed of a dielectric film layer whose film thickness is almost uniform within the metal film layer forming region are formed. It is characterized in Rukoto.

The substrate and the mask plate are disposed on a peripheral side surface of the rotating drum, and the film formation gap is formed by a spacer member disposed between the substrate and the mask plate, and a mask opening formed in the mask plate is formed. At least one of the upper and lower end edges is arranged on a straight line that coincides with the rotation direction of the rotary drum, and a sputter region central portion of the first target is arranged substantially at the center of the mask opening, and the sputter of the second target is arranged. An area center portion is disposed at a position displaced by a predetermined distance in a direction orthogonal to the rotation direction of the rotary drum with respect to the approximate center of the mask opening, and the film edge of the gradation layer of the dielectric film layer is the metal film It is characterized in that it is formed at a position separated from the edge of the mask opening with respect to the film edge of the gradation layer.

Next, an apparatus for manufacturing a neutral density filter according to the present invention is an apparatus for manufacturing a neutral density filter in which a dielectric film layer and a metal film layer are formed on a substrate in the form of a laminate. A cylindrical rotating drum disposed in the chamber, a plurality of substrates mounted on the rotating drum, and a metal disposed at a distance from the substrate in a first area divided in the film forming chamber. A first target made of a material, a second target made of a dielectric material disposed at a distance from the substrate in a second area partitioned in the film forming chamber, and in the film forming chamber A reactive gas supply source disposed in the divided third area; and a sputtering operating gas supply source disposed in the first area and the second area, wherein the substrate is formed in the film formation chamber. A cylindrical rotating drum placed inside And a mask plate having the mask opening is disposed on the rotating drum so as to form a predetermined film-forming gap between the rotary plate and the first target is a plate-like material and substantially the same as the substrate surface. Parallel to each other and the sputter region central portion of the first target is disposed at a position facing the substrate on a normal line connecting the central portion of the mask opening and the rotation center of the rotary drum, and the second target is plate-shaped The material is substantially parallel to the substrate surface, and the sputter region central portion of the second target is perpendicular to the rotation direction of the rotary drum with respect to the normal line connecting the central portion of the mask opening and the rotation center of the rotary drum. By placing a sputtering voltage on the first and second targets while rotating the rotating drum, being arranged at a position facing the substrate at a position appropriately displaced in the direction, The substrate has a metal film layer whose thickness is gradually reduced by diffusion of sputtered particles generated in the film forming gap from the mask opening of the mask plate in a direction perpendicular to the rotation direction of the rotating drum, Is characterized in that a gradation layer comprising a substantially uniform dielectric film layer is formed in the metal film layer forming region.

As described above, according to the present invention, the sputter region central portion of the first target is disposed at a position facing the substrate on the normal line connecting the central portion of the mask opening and the rotation center of the rotary drum, while the sputter of the second target. Sputtering of each target is carried out in a state where the central part of the region is arranged at a position facing the substrate at a position appropriately displaced in a direction perpendicular to the rotation direction of the rotary drum with respect to the normal line connecting the central part of the mask opening and the rotation center of the rotary drum. Thus, the following effects can be obtained because the film is formed.

The substrate and the mask plate mounted on the rotating drum always maintain the same geometric positional relationship with respect to the target when the film is formed by rotating the rotating drum. Therefore, since the positional relationship between the factors for forming the film is stable, even if a plurality of substrates are arranged on the rotating drum, a substantially uniform film layer is formed, and there is no variation in the film layers of each substrate.

Since the gradation region layer whose film thickness gradually decreases linearly is formed by sputtered particles diffusing from the mask opening having a film forming gap with the substrate, this particle diffusion is from the opening edge of the mask opening to the periphery. Decreases gradually. Therefore, the sputtered particles of the present invention are extremely fine compared to the vapor deposition components in the conventional vacuum vapor deposition method, and therefore, when diffusing from the mask opening to the periphery, it is attenuated in the same manner as the light diffusion, and the normal direction of the mask opening is formed on the substrate. A film having a uniform thickness is generated, and a film (gradation region layer) having a thickness that gradually decreases in proportion to the diffusion angle is formed around the film.

By forming this gradation area layer with sputtered particles diffusing around the upper and lower edges perpendicular to the rotation direction of the mask opening, the influence of the rotation of the rotating drum can be suppressed, so that the film is more stable (no variation) Thickness attenuation is obtained.

In particular, according to the present invention, each of the first and second targets is formed in a plate shape so as to be substantially parallel to the substrate surface, and the sputter region central portion of the first target is formed between the mask opening central portion and the rotating drum. The rotational direction of the rotating drum is relative to the normal line where the sputter region central portion of the second target connects the mask opening central portion and the rotating center of the rotating drum at a position facing the substrate on the normal line connecting the rotating center. The thickness of the metal film layer that forms the gradation region layer and the dielectric film layer that are gradually decreased linearly is arranged for each film layer by disposing it at a position that is appropriately displaced in a direction orthogonal to the substrate. In particular, since the film thickness of the dielectric film layer can be formed almost uniformly in the metal film layer region, the following effects can be obtained.

When a light attenuating film is formed of a metal film rich in light absorption and a dielectric film, for example, the metal film is formed in a concentration gradient in which the light absorption characteristics change linearly, It is possible to generate a gentle density gradient that does not impair the antireflection effect of light. In particular, this film gradient places the center of the first target approximately at the center of the mask opening and places the center of the second target at a non-target position displaced by a predetermined distance from the center of the first target before film formation. Can be done easily.

When the light-reducing film is composed of a metal film rich in light absorption characteristics and a dielectric film that prevents light transmission and light reflection, the metal film has a linear concentration gradient and the light-reducing film reflects By forming a gentle density gradient that does not prevent prevention, it is possible to provide a neutral density filter excellent in light attenuation characteristics and antireflection characteristics, and the manufacturing cost can be reduced.

The present invention will be described in detail below based on the preferred embodiments shown in the drawings. FIG. 3A and FIG. 3B are conceptual diagrams for causing vapor deposition components to fly from the target. FIGS. 4A and 4B show the positional relationship between the substrate mounted on the rotating drum and the target. It is a model figure which shows a conceptual structure.

First, the method of forming the neutral density filter will be described. The neutral density filter 43 shown in FIG. 8 is light-absorbing on the substrate (deposition base substrate) 10 as shown in FIG. The light reduction film 20 is formed. The light-reducing film 20 is formed into an equal density region 20a having a uniform thickness and a uniform light transmittance, and a gradation region 20b in which the film thickness is gradually reduced. The illustrated one is formed in a laminated form from a metal film layer 21 rich in light absorption and a dielectric film layer 22 that suppresses light transmission and reflection. The metal film layer 21 and the dielectric film layer 22 are formed in a plurality of layers in a stacked manner, and the illustrated one is laminated in the order of a substrate, a metal film layer, a dielectric film layer, a metal film layer, and a dielectric film layer. In addition, an AR coating layer (Anti Reflation Coating) 23 is formed. These film forming materials will be described later.

The neutral density filter 43 formed as described above is formed as follows.
(1) The metal film layer 21 and the dielectric film layer 22 are formed by reactive sputtering. As shown in FIG. 3A, the substrate 10 is mounted on the stage 31 in the chamber 30, and the target 32 is disposed so as to face the substrate 10. The vapor deposition stage 31 is composed of a cylindrical rotary drum so as to rotate relative to the target 32. Then, the target 32 is placed on the cathode electrode 35 and a sputtering voltage is applied to the stage 31. This sputtering voltage is supplied from, for example, a high frequency power source. Therefore, an operating gas is introduced into the chamber 30 that is substantially in a vacuum state. Then, the working gas becomes a reactive gas state in the chamber, and the electrons or ions move at high speed and collide with the target 32. Due to this collision, the sputtered particles SP fly from the target 32 and adhere to the substrate 10.

(2) The metal film layer 21 is composed of a light-absorbing metal material target (second target), and the dielectric film layer 22 is a dielectric material (Si, Al, etc.) target (first target). Consists of. When the first and first targets 21 and 22 are deposited, the deposition pressure P of the operating gas (Ar gas, Ne gas) that is normally sputtered is varied, or the power of the sputtering power source supplied to the target This embodiment is characterized in that the first and first targets 21 and 22 are disposed so as to face asymmetric positions with respect to the film formation surface of the substrate 10 in this embodiment. The adjustment of the sputtering conditions will be described later. Under such conditions, the dielectric film layer 22 is formed by sputtering the dielectric material with an operating gas to form a film of sputtered particles SP on the substrate. A film is formed with a compound formed by irradiating a reactive gas on the substrate. That is, a film is formed on the substrate with particles of silicon, aluminum alloy, etc., and then irradiated with a reactive gas such as oxygen gas, nitrogen gas, fluorine gas. As a result, an oxide film, a nitride film, and a fluoride film are generated.

(3) Therefore, when the substrate 10 is mounted on a rotating drum (stage; hereinafter the same) 31 in the chamber 30 and the target 32 is mounted on the cathode electrode, the target 32 is configured as a planar evaporation source with a plate-like material. In addition, the plate-like material is arranged substantially in parallel with the surface of the substrate 10. As shown in FIG. 3A, the substrate 10 mounted on the circumference of the rotary drum 31 and the target 32 are arranged in parallel with a distance L (flight distance) from this substrate. Thereby, the planar vapor deposition source and the substrate 10 are maintained in a uniform distance relationship in the XX direction shown in FIG. 3B.

Next, a mask plate 34 having a mask opening 33 is disposed between the target 32 and the substrate 10. The mask plate 34 is preferably attached to the rotating drum 31 as a set with the substrate 10. A predetermined film-forming gap d is formed between the mask plate 34 and the substrate 10 as shown in FIG. 3B.

In particular, the substrate 10 and the mask plate 34 are arranged such that at least one of the upper and lower edges 33a and 33b of the mask opening 33 perpendicular to the rotation direction (YY) of the rotary drum 31 coincides with the YY direction. . The illustrated upper edge 33 a and lower edge 33 b are formed in parallel with each other, and the mask plate 34 is mounted on the rotating drum 31 so that the upper and lower edges 33 a and 33 b coincide with the rotation direction of the rotating drum 31.

With such a configuration, the rotating drum 31 is rotated at a predetermined speed, a high frequency voltage is applied between the substrate 10 and the target 32, and simultaneously, an operating gas is introduced into the chamber. As a result, a film is formed on the substrate. As shown in FIG. 3B, the film formation state at this time is a gradation due to diffusion of sputtered particles SP in the film formation gap d at the upper edge 33a and the lower edge 33b of the mask opening 33 in the rotation axis direction YY of the rotary drum 31. Region 20b is generated. In addition, an equi-concentration film layer 20a is generated at the center of the opening. Explaining this film formation state, diffusion of the sputtered particles SP occurs from the periphery of the mask opening 33 toward the outer periphery. It is known that the diffusion of the sputtered particles SP causes a diffusion phenomenon similar to light in atomic or molecular fine particles. It has been investigated that this diffusion attenuates with a cosine function with respect to the diffusion angle θ.

Accordingly, the film thickness formed on the outer peripheral portion of the mask opening 33 generated on the substrate 10 becomes a cosine curve shown in FIG. 6A, and the film thickness along the linear component indicated by Lx in FIG. 6B is generated. The present invention is characterized in that such film formation is formed in the XX direction shown in FIG. 4A orthogonal to the rotation direction of the substrate 10 rotating with respect to the target 32. Accordingly, it is possible to form the gradation region 20b in which the film thickness is linearly attenuated without being affected by the rotation of the rotating drum 31.

Explaining the configuration of the mask plate 34, the substrate 10 is mounted on the rotary drum 31 as shown in FIG. 3B. Although the specific configuration is not shown, it is attached to the rotating drum 31 via a mounting jig. At this time, a frame-like spacer member 34S is provided between the substrate 10 and the mask plate 34 is attached to the spacer member 34S. The mask plate 34 is provided with a mask opening 33 corresponding to the film formation area, and at least one of the upper edge 33a and the lower edge 33b of the opening 33 is a line that coincides with the rotation direction (Y-Y direction) of the rotary drum 31. It is attached to the rotating drum 31 so as to have a minute. A film formation gap d is formed between the spacer member 34S and the substrate 10. In this case, the film formation gap d (interval between the substrate and the mask plate) is obtained by the following equation for the desired (design value) film formation width Δx shown in FIG. 6B. [D = k × ΔX / tan θ], the correction value k and the diffusion angle θ are obtained as experimental values from the atmosphere in the chamber.

As shown by the solid line in FIG. 6A, the gradation region layer formed as described above has a film thickness approximately approximate to the ideal film thickness (broken line in the figure). On the other hand, in the film forming method by vacuum vapor deposition described in Patent Document 5 described above, the film thickness is as shown by a chain line in FIG. As is clear from this, in the film forming method of the present invention, the film thickness gradually decreases linearly, and the concentration gradient and light transmittance are also linearly attenuated.

Specific embodiments of the film forming method of the present invention described above will be described.

The above-described substrate 10 is made of transparent glass or a synthetic resin plate. In the case of a synthetic resin, for example, polyethylene terephthalate, polyethylene naphthalate, norbornene resin or the like is used. As the other substrate material, a suitable material is selected according to the use environment.

The aforementioned dielectric film is made of oxide, nitride, or fluoride such as silicon or aluminum. For this reason, the target 32 uses a plate member of Si or Al.

The metal film described above uses a metal oxide rich in light absorption such as chromel, niobium, and titanium.

As the above-mentioned coating layer 23, a hard or water-repellent material such as magnesium fluoride is used. In this case, magnesium oxide is used as the target 32.

The sputtering apparatus shown in FIG. 7 will be described. The apparatus shown in FIG. 7 includes an outer casing 30a that forms a chamber 30, a cylindrical rotary drum 31 that is rotatably housed in the chamber 30, and a sputter that is disposed at a distance from the rotary drum 31. It is comprised with the electrode 35. FIG.

The inside of the chamber 30 is formed in a vacuum. The chamber 30 is divided into a plurality of areas 36 a to 36 d by a shielding plate 37. The illustrated one is a first area 36a for sputtering a second target 32a for forming the metal film layer 21 (hereinafter referred to as “metal target”), and a second target 32b for forming the dielectric film layer 22 (hereinafter referred to as “metal target”). Irradiation with active gas, second area 36b for sputtering (dielectric target), third area 36c for sputtering second target 32c (hereinafter referred to as “coat layer target”) for forming coating layer 23, and irradiation with active gas The fourth area 36d is divided. A pair of sputter electrodes 35a and 35b are built in the first, second and third areas 36a to 36c, respectively.

As shown in FIG. 3C, the metal target 32a and the dielectric target 32b are formed at the opposite positions 32-1 with respect to the film formation surface of the metal target 32a as shown in FIG. The opposite positions 32-2 and 32-3 with respect to the film formation surface of the dielectric target 32b with respect to the film formation reference line (the two-dot chain line in the drawing) at which the central portion is formed are mutually the film formation reference line (the two dots in the drawing). Displaced by a displacement amount e in the opposite direction to the chain line) and arranged opposite to the film formation surface. The displacement amount e is adjusted and set in advance according to the width of the film formation width Δx described above.

In addition, as shown in FIG. 4B, in the case where a single plate material is used for each of the metal target 32a and the dielectric target 32b, in order to take the relationship between the facing positions 32-1, 32-2, and 32-3, It can implement by covering with the opening plate 32c which formed the opening part in the opposing positions 32-1, 32-2, and 32-3.

In addition, as shown in FIG. 4C, when using a number of plate materials corresponding to each substrate 10 for the metal target 32a and the dielectric target 32b, the relationship between the facing positions 32-1, 32-2, and 32-3 is as follows. Therefore, it can be carried out by arranging the sputter electrodes 35a and 35b so as to be in the facing positions 32-1, 32-2 and 32-3.

The pair of sputter electrodes 35a and 35b are connected to a high-frequency AC power source, and one is a cathode and the other is an anode. Each sputter electrode 35a, 35b is connected to a power supply coil 35c, and is configured such that a high frequency power of 100 KHz to 40 MHz is applied. A bias voltage is applied to the rotating drum 31 on which the substrate 10 is mounted. A target 32 is mounted on each of the sputter electrodes 35a and 35b in the first, second and third areas 36a to 36c. The target 32 is made of a plate material and constitutes a planar vapor deposition source. An operating gas such as argon or neon is introduced into the first, second and third areas 36a to 36c via a controller 38. 38 g shown is an argon gas supply cylinder. The active gas is supplied from the supply cylinder 38g to the fourth area 36d via the controller 38.

A reactive gas generation chamber 39 is provided in the fourth area 36d, and is configured to convert the gas from the supply cylinder 38g into a reactive gas and irradiate it into the fourth area 36d. In such an apparatus configuration, the rotating drum 31 is rotated at a predetermined speed, the metal target 32a in the first area 36a is sputtered to deposit a metal film (for example, Nb) on the substrate 10, and then the derivative target in the second area 36b. A dielectric film (for example, Si) is deposited on the substrate 10 by sputtering 32b. Next, the substrate is irradiated with an active gas (for example, O ₂ ) in the fourth area 36d. Then, the dielectric film on the substrate is oxidized to generate an oxide (eg, SiO ₂ ) film.

Thus, after laminating the metal film layer 21 and the dielectric film layer 22 in a plurality of layers, the coat layer target 32c in the third area 36c is sputtered to adhere the AR coat layer 23 to the uppermost layer.

As described above, according to the present invention, when the neutral density filter 43 is formed, the substrate 10 and the mask plate 34 are mounted on the rotary drum 31, and the sputtered particles of the film component are applied from the planar evaporation source parallel to the substrate 10. Fly to form a film. At this time, a film-forming gap d having a predetermined interval is formed between the mask plate 34 and the substrate 10. Accordingly, the substrate 10 corresponding to the mask opening 33 of the mask plate 34 has the equiconcentration film layer 20a, and the gradation region 20b in which the film thickness gradually decreases linearly around the upper edge 33a and the lower edge 33b of the mask opening 33. It is formed.

Therefore, the present invention is characterized in that the metal film layer 21 and the dielectric film layer 22 are formed as follows. This will be described with reference to FIG. 5A to FIG. 5C and FIG. 5D to FIG. 5G. In FIG. As shown in FIG. 5A, when the first metal film layer 21 is formed on the substrate 10, the film forming pressure of the working gas is set to a predetermined pressure P1. At this time, the film formation gap d is set so that the film width Δx of the gradation area becomes zero as shown in the figure.

Next, when the dielectric film layer 22 is formed on the first metal film layer 21 shown in FIG. 5B, the film formation pressure P2 of the working gas supplied to the second area 36b when the target 32b is sputtered. Is set to a value larger than P1. Then, the dielectric film 22 is formed on the edge of the film with a gentle concentration gradient having a thickness of Δh shown in the figure. This is because the diffusion angle θ2 (θ2> θ1) of the sputtered particles diffusing from the edge 33a of the mask opening 33 is larger than the previous angle θ1.

Next, when the second metal film layer 21 is formed on the first metal film layer 21 and the second dielectric film layer 22 shown in FIG. 5C, it is the same as the first film formation (FIG. 5A). Film forming conditions (film forming pressure P1, diffusion angle θ1). As a result, a film having a linear concentration gradient is obtained as in the first film layer.

Next, when a dielectric film is formed on the first metal film, the second dielectric film, and the third metal film shown in FIG. 5D, the above-described second film formation conditions are set. As a result, a film thickness of Δh is formed at the film edge with a gentle concentration gradient as in the second film formation.

As described above, after the film is formed in a plurality of stages, the coating layer 23 is formed on the surface layer. The coating layer 23 is coated with a material that is relatively hard and rich in water repellency, and is formed so that the internal dielectric film layer and metal film layer do not deteriorate over time. In this case, the film forming conditions are set as gentle as possible with a film thickness gradient as in the case of the dielectric film described above. For example, the film forming pressure P3 is set to (P3 ≧ P2).

FIG. 5F shows the film layer structure of the final product film formed as described above. The uniform film layer is configured such that the dielectric film layer and the metal film layer each have a predetermined thickness, and the film thickness gradually decreases linearly in the gradation region. At this time, the gradient of the dielectric film layer is formed at a gentle angle with respect to the gradient of the metal film layer 21. As shown in FIG. 5G, the film edge is formed such that the metal film layer is “zero” and the dielectric film layer is “Δh”.

As shown in FIG. 8, the light amount adjusting device E according to the present invention arranges one or a plurality of light amount adjusting blades 42 in an openable and closable manner in a base plate 40 and an optical path opening 41 formed in the base plate 40. The amount of light passing through the optical path opening 41 is adjusted by the light amount adjusting blade 42. The illustrated one is configured to adjust the amount of light with a pair of blades 42a and 42b, and each blade is formed with constrictions 42x and 42y so as to adjust the amount of light in a small aperture state. Therefore, a neutral density filter 43 is attached to the narrowed portion 42x of the one blade 42a. The neutral density filter 43 is formed by cutting the single concentration film layer 20a and the gradation region 20b formed on the substrate 10 described above. The light amount adjustment blade 42a is attached so that the light transmittance increases toward the center of the optical path.

FIG. 1A is a model diagram of a conventional film forming method of a neutral density filter and is an explanatory diagram of an apparatus configuration.
FIG. 1B is an explanatory diagram of an arrangement configuration of a substrate and a mask plate of the same apparatus configuration.
2A is a model diagram of a film forming method of the conventional neutral density filter shown in FIG.
FIG. 2B is an enlarged explanatory view of a state where a film is formed on the substrate in the model diagram.
FIG. 3A is a conceptual explanatory diagram of a film forming method according to the present invention, and is a model diagram in which vapor deposition components are ejected from a target when viewed from above the apparatus.
FIG. 3B is an explanatory diagram of the concept, and is a model diagram in which a vapor deposition component is caused to fly from a target when viewed from the side of the apparatus.
FIG. 3C is an explanatory diagram for explaining a target arrangement and a film formation state.
FIG. 3D shows a target arrangement relationship corresponding to FIG. 3C.
FIG. 4A shows the positional relationship between the substrate and the target when the rotary drum is viewed obliquely from above.
FIG. 4B shows the positional relationship between the substrate and the target when viewed from the same lateral side surface.
FIG. 4C shows the positional relationship between the substrate and the target when viewed from the same lateral side surface as that in FIG. 4B.
FIG. 5A is a method for forming a neutral density filter according to the present invention, and is an explanatory view of film formation of the first layer.
FIG. 5B is an explanatory diagram of film formation of the second layer.
FIG. 5C is an explanatory diagram of film formation of the third layer.
FIG. 5D is an explanatory diagram of film formation of the fourth layer.
FIG. 5E is an explanatory diagram of film formation of the coating layer.
FIG. 5F is a sectional view of a film layer of the neutral density filter.
FIG. 5G is an enlarged cross-sectional view of the gradation region layer.
FIG. 6A is a schematic diagram showing the relationship between the film thickness of the neutral density filter and the diffusion distance according to the present invention.
FIG. 6B is a relationship diagram between the density of the neutral density filter and the film formation position.
FIG. 7 is a top view of the sputtering apparatus.
FIG. 8 is a perspective view showing the arrangement of the light amount adjusting device.

Explanation of symbols

d Deposition gap 10 Substrate (deposition base material)
20 Thin film layer 20a Equivalent concentration film layer 20b Gradation film layer 21 Metal film layer (second target)
22 Dielectric film layer (first target)
23 coating layer 31 stage (rotating drum)
32 target 32a second target (metal target)
32b Second target (derivative target)
32c Second target (coat layer target)
33 Mask opening 34 Mask plate 43 ND filter

Claims (6)

Sputtering at least first and second targets made of different substances in a film forming chamber to form a predetermined film forming gap with respect to the substrate, and the first target is placed on the substrate through a mask opening. A method of forming a neutral density filter comprising: forming a metal film layer made of a material and a dielectric film layer made of the second target material in a stacked manner;
(1) The substrate is mounted on a cylindrical rotating drum disposed in the film forming chamber,
(2) A mask plate having the mask opening is disposed on the rotating drum so as to form a predetermined film formation gap between the substrate and the substrate.
(3) The first target is a plate-like material and is substantially parallel to the substrate surface, and the center part of the sputter region of the first target is on the normal line connecting the central part of the mask opening and the rotation center of the rotary drum. Arranged at a position facing the substrate,
(4) The second target is a plate-like material and is substantially parallel to the substrate surface, and the sputter region central portion of the second target connects the mask opening central portion and the rotation center of the rotary drum. Is disposed at a position facing the substrate at a position appropriately displaced in a direction perpendicular to the rotation direction of the rotating drum,
By applying a sputtering voltage to the first and second targets while rotating the rotating drum, the deposition gap extends from the mask opening of the mask plate to the substrate in a direction perpendicular to the rotating direction of the rotating drum. The diffusion of sputtered particles generated in the metal film layer gradually reduces the film thickness, and the gradation layer is formed of a dielectric film layer having a substantially uniform film thickness in the metal film layer formation region. A film forming method for a neutral density filter. The substrate and the mask plate are disposed on a peripheral side surface of the rotating drum,
The film forming gap is formed by a spacer member disposed between the substrate and the mask plate,
At least one of upper and lower edges of the mask opening formed in the mask plate is disposed on a straight line that matches the rotation direction of the rotating drum,
The sputter region central portion of the first target is disposed at substantially the center of the mask opening,
The gradation layer film of the dielectric film layer is arranged such that the center part of the sputter region of the second target is displaced by a predetermined distance in the direction orthogonal to the rotation direction of the rotary drum with respect to the approximate center of the mask opening. 2. The method of forming a neutral density filter according to claim 1, wherein the edge is formed at a position spaced from the edge of the mask opening with respect to the film edge of the gradation layer of the metal film layer. A substrate and a gradation layer composed of a metal film layer and a dielectric film layer formed by sputtering different substances on the substrate to form a gradation layer, and the metal film layer and the dielectric film layer are both The dielectric film layer has a gradient angle with respect to the substrate, and the gradient angle of the dielectric film layer is smaller than the gradient angle of the metal film layer with the substrate, and the film thickness is substantially uniform in the metal film layer formation region. A neutral density filter. A diaphragm blade that is arranged in the imaging optical path and adjusts the imaging light amount;
A neutral density filter attached to the diaphragm blade, and
An imaging light amount diaphragm device, wherein the neutral density filter has the configuration according to claim 3. An apparatus for manufacturing a neutral density filter for forming a dielectric film layer and a metal film layer on a substrate in a laminated form,
A deposition chamber;
A cylindrical rotating drum disposed in the film forming chamber;
A plurality of substrates mounted on the rotating drum;
A first target made of a metal material disposed at a distance from the substrate in a first area divided in the film forming chamber;
A second target made of a dielectric material disposed at a distance from the substrate in a second area divided in the deposition chamber;
A reactive gas supply source disposed in a third area divided in the film forming chamber;
An operating gas supply source for sputtering disposed in the first area and the second area;
With
The substrate is mounted on a cylindrical rotating drum disposed in the film forming chamber,
A mask plate having the mask opening is disposed on the rotating drum so as to form a predetermined film forming gap between the substrate and the substrate.
The first target is a plate-like material that is substantially parallel to the surface of the substrate, and the center region of the sputter region of the first target is on the substrate on a normal line connecting the center of the mask opening and the rotation center of the rotary drum. It is placed at the opposite position,
The second target is a plate-like material, is substantially parallel to the substrate surface, and the sputter region center portion of the second target is in relation to the normal line connecting the center portion of the mask opening and the rotation center of the rotary drum. Arranged at a position facing the substrate at a position appropriately displaced in a direction perpendicular to the rotation direction of the rotating drum,
By applying a sputtering voltage to the first and second targets while rotating the rotating drum, the deposition gap extends from the mask opening of the mask plate to the substrate in a direction perpendicular to the rotating direction of the rotating drum. Forming the gradation layer consisting of the metal film layer whose thickness is gradually reduced by the diffusion of sputtered particles and the dielectric film layer whose film thickness is almost uniform in the metal film layer formation region. An apparatus for manufacturing a neutral density filter. The substrate and the mask plate are disposed on a peripheral side surface of the rotating drum,
The film forming gap is formed by a spacer member disposed between the substrate and the mask plate,
At least one of upper and lower edges of the mask opening formed in the mask plate is disposed on a straight line that matches the rotation direction of the rotating drum,
The sputter region central portion of the first target is disposed at substantially the center of the mask opening,
The gradation layer film of the dielectric film layer is arranged such that the center part of the sputter region of the second target is displaced by a predetermined distance in the direction orthogonal to the rotation direction of the rotary drum with respect to the approximate center of the mask opening. 6. The apparatus for manufacturing a neutral density filter according to claim 5, wherein the edge is formed at a position spaced from the edge of the mask opening with respect to the film edge of the gradation layer of the metal film layer.