JP2009001889A - Film deposition method for neutral density filter, neutral density filter using the same, and image pick-up light quantity diaphragm device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film deposition method with which, when a plurality of film layers corresponding to optical properties are formed on a transparent substrate, density gradients in a gradation region where film thickness is gradually decreased can be set per film layer. <P>SOLUTION: The neutral density film is obtained by sputtering a plurality of targets at least composed of first and second substances with different optical properties with a working gas so as to perform film deposition in a layered shape in order of the first substance and the second substance, and the neutral density film comprises: an equal density region wherein film thickness is almost equal; and a gradation region wherein film thickness is linearly gradually decreased. The gradation region is formed in such a manner that film thickness is gradually decreased by diffusion of sputtering particles produced within a prescribed film deposition gap formed between the substrate and each mask plate having a mask opening, and the gradation region is generated in such a manner that the density gradient of the first substance and the density gradient of the second substance are made different in accordance with a difference in the film deposition pressure of the working gas upon the sputtering of the target or a difference in the bias voltage applied to the substrate or the mass of the working gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light-reducing filter that adjusts the light amount of a photographing device such as a video camera or a digital still camera, a film forming method thereof, and a light amount reducing device. It relates to the improvement of gradation film formation.

  In general, this type of neutral density filter is widely used as an ND filter (Neutral Density Filter) in various imaging apparatuses. This ND filter forms a thin film having excellent light absorption characteristics on a resin or glass substrate. The ND filter is known to be formed as a single thin film having a uniform concentration as a whole, or as a gradation thin film whose density is continuously changed (gradual decrease).

  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. Therefore, for example, as disclosed in Patent Document 1, it has been proposed to attach an ND filter to an aperture blade that adjusts the amount of light to suppress a diffraction phenomenon that occurs at the time of small aperture. In the case of a single-density ND filter, diffraction occurs due to the small aperture formed by the end of the ND filter and the aperture shape, resulting in degradation of image quality. In order to prevent the deterioration, a gradation filter that gradually decreases toward the opening diameter side has been proposed.

  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 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.

  Therefore, the conventional metal film layer is formed of niobium (Nb), chromel (Cr—Ni), titanium (Ti), etc., and the dielectric film layer is an oxide such as silicon (Si), aluminum (Al), nitride, It is made of fluoride. The uppermost layer (surface 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, it is sufficient if the concentration gradient of the dielectric film (intermediate layer for suppressing light transmission and preventing reflection) is large There is a problem that an effective antireflection effect cannot be obtained.

Therefore, Patent Document 3 proposes a film structure in which the film thickness of a dielectric film (SiO ₂ or the like) for preventing light reflection is made uniform in a gradation region. Similarly, Patent Document 4 proposes a film structure in which the gradient gradient of the dielectric film is gentle with respect to the gradient gradient of the thickness of the metal film in the gradation region.

  On the other hand, as a method for forming such a gradation film layer, it has been proposed to prepare the film by microphotography (for example, Japanese Patent No. 2754518), but it is widely used to prepare it by a vacuum evaporation apparatus. For example, Patent Document 5 discloses that a gradation film layer is formed with a vapor deposition film.

  In Patent Document 5, a substrate (deposition base material) is mounted on a sample stage of a vacuum vapor deposition apparatus (physical vapor deposition method), and an evaporation component is heated and evaporated while the stage is rotated (revolved) to form a film on the substrate. A film forming method has been proposed. 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.

  In order to form a gradation film using a vacuum vapor deposition apparatus in Patent Document 5, the following measures are taken. The gradation film generation mechanism disclosed in Patent Document 5 is shown in FIG. In this film forming method, a large number of substrates 50 are mounted radially on a vapor deposition stage (vapor deposition umbrella) 51 as shown in FIG. Then, a mask 53 having a film formation opening 52 is disposed at a position separated from the stage, and the stage 51 and the mask 53 are equipped in the apparatus so as to rotate (revolve) 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 (revolved) 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 along an arc locus inclined at a predetermined angle θ as shown in the figure. 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. Accordingly, a film layer having a film thickness d gradually decreasing from d1 to d2 is formed on the substrate as shown in FIG. With this film layer, the transmitted light amount has a high transmittance in a portion with a high density (film thickness d1), and a low transmittance in a portion with a low density (film thickness d2).

In the case of generating a conventional gradation film, a mask plate is provided between the substrate and the target in the vapor deposition tank as described above, and is formed from a position inclined by a predetermined angle (α angle shown in FIG. 1) with respect to the mask opening. The film component (evaporated particles) is formed to evaporate. Therefore, although not disclosed in Patent Document 5, the distance between the target and the mask plate L1 in FIG. 1 is set sufficiently larger (longer) than the distance d between the mask plate and the substrate, and vapor deposition projected from the target. The component is controlled to draw a straight line like parallel rays. As a result, the geometrically formed film thickness changes linearly as shown in FIG.
Japanese Patent No. 2754518 (FIGS. 1 and 4) JP 2006-78564 A (FIG. 8) JP 2004-205777 A (FIG. 1) Japanese Patent Laying-Open No. 2005-326687 (FIG. 1) JP 2005-345746 A

  As described above, a neutral density filter having a gradation region formed so as to have a density that gradually decreases toward the center of the optical path when the amount of imaging light is attenuated in various imaging apparatuses is known. It is also known that the gradation region is formed by providing a mask plate between the substrate and the evaporation source using a vacuum deposition apparatus.

  Therefore, a film structure disclosed in the above-mentioned Patent Documents 3 and 4, that is, a film forming method for gradually decreasing the film thickness so that a plurality of film layers have different concentration gradients is disclosed in Patent Document 3, for example. As shown in the figure, the position of the mask plate with respect to the substrate (attached to the vapor deposition umbrella) is different between when the first layer (metal film) is formed and when the second layer (dielectric film) is formed. The film is formed.

  In such a film thickness adjustment, when a plurality of substrates as shown in FIG. 1 are mounted on the vapor deposition stage and simultaneously formed, it is extremely difficult to accurately adjust the relative positions of the mask plate and each substrate. As a result, the ideal film thickness as shown in FIG. 5 (b) (broken line in the figure) is obtained as shown by the chain line in FIG. The concentration gradient cannot be obtained.

  Therefore, the present inventor pays attention to generating a neutral density filter with a known reactive sputtering apparatus (for example, Japanese Patent Application Laid-Open No. 11-279757), and can adjust the concentration gradient by setting the sputtering conditions. Came up with a new film formation method.

The present invention provides a film forming method capable of setting, for each film layer, a concentration gradient in a gradation region where the film thickness gradually decreases when a plurality of film layers corresponding to optical characteristics are formed on a transparent substrate. Is the main issue.
Another object of the present invention is to provide a neutral density filter that has a dielectric film that prevents reflection of light and that does not reduce the antireflection effect in a gradation region.

To achieve the above object, the present invention employs the following configuration.
The light-reducing film is formed by laminating a plurality of targets made of at least first and second substances having different optical characteristics with an operating gas to form a laminated structure in the order of the first substance and the second substance. An equal density region having substantially the same thickness and a gradation region in which the film thickness gradually decreases linearly. The gradation area is generated so that the film thickness gradually decreases due to diffusion of sputtered particles generated in a predetermined film formation gap formed between the substrate and a mask plate having a mask opening. When the target is sputtered, the concentration gradient of the first substance and the concentration gradient of the second substance differ depending on the difference in the deposition pressure of the working gas, the difference in the sputtering voltage applied to the target, or the mass difference in the working gas. Generate as follows.

  The first material generates a metal film rich in light absorption, and the second material generates a dielectric film. The concentration gradient of the dielectric film is smaller than the concentration gradient of the metal film in the gradation region. Is set to be

  The dielectric film and the metal film are formed by (1) mounting the substrate on a cylindrical rotating drum disposed in a film forming chamber, and (2) using a plate-like material to make the target substantially the same as the surface of the substrate. (3) A mask plate having a mask opening is arranged on the rotating drum so as to form a predetermined film-forming gap between the substrate and the substrate, and the gradation area is a rotation of the rotating drum. The film is formed by diffusion of sputtered particles generated in the film forming gap from the mask opening of the mask plate on the upper and lower edges of the substrate orthogonal to the direction.

  A dielectric film and a metal film formed in a laminated manner on the substrate, and the dielectric film is formed by sputtering a target made of a dielectric substance with an operating gas, and then forming a reactive gas. The metal film is formed by sputtering a target made of a metal substance with an operating gas. The dielectric film and the metal film are gradation regions in which the film thickness gradually decreases due to diffusion of sputtered particles from the opening edge of the mask plate that forms a film forming gap between the target film and the substrate when sputtering the target. This gradation region has a concentration gradient of the dielectric film due to a difference in the deposition pressure of the working gas when sputtering the target, a difference in sputtering voltage applied to the target, or a mass difference in the working gas. It produces | generates so that the concentration gradient of the said metal film may differ.

  The concentration gradient of the dielectric film is set to be smaller than the concentration gradient of the metal film in the gradation region.

  An imaging light amount diaphragm device according to the present invention includes an aperture blade that adjusts an imaging light amount disposed in an imaging optical path, and a neutral density filter attached to the aperture blade, and the neutral density filter has the above configuration.

  In the present invention, when the first and second plurality of substances are sputtered with the working gas to form a film of sputtered particles on the substrate, the diffusion of sputtered particles generated in the film forming gap between the substrate and the mask opening As a result, a gradation region where the film pressure gradually decreases is formed. At this time, the concentration gradient in the gradation region is made different between the first material and the second material by adjusting the pressure of the working gas for sputtering the target or by adjusting the power supply amount of the sputtering power applied to the target. Therefore, the following effects are produced.

  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 concentration gradient can be easily achieved by increasing or decreasing the deposition pressure of the working gas introduced into the chamber, or by adjusting the amount of power supplied such as voltage and frequency applied to the target.

Therefore, in the case of forming a concentration gradient for each film layer by adjusting the shape of the mask plate or the position relative to the substrate in the conventional vacuum deposition apparatus, positional deviation of the mask plate, variation between multiple substrates, etc. occur. In comparison, the film thickness can be adjusted with extremely simple control of the deposition conditions.
In particular, the present invention sets the concentration gradient by adjusting the deposition pressure, the supply voltage, or the mass of the working gas. Therefore, the size of the deposition substrate or the deposition material differs in the same sputtering apparatus. Also, the film thickness in the gradation area can be easily adjusted to the optimum thickness.

  Furthermore, in the present invention, 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 is reduced to a linear concentration gradient. By forming the optical film in a gentle concentration gradient that does not interfere with antireflection, it is possible to provide a neutral density filter with excellent light attenuation characteristics and antireflection characteristics, and its manufacturing cost is notable. Has an effect.

  The present invention will be described in detail below based on the preferred embodiments shown in the drawings. 3 and 4 are model diagrams showing a conceptual configuration of a film forming method according to the present invention. FIG. 3 is a conceptual diagram for causing vapor deposition components to fly from the target. FIG. 4 is a diagram illustrating a substrate mounted on a rotating drum and a target. The arrangement relationship is shown.

  The film forming method of the neutral density filter according to the present invention will be described. The neutral density filter (ND filter) 43 of the present invention forms a light-absorbing neutral density film 20 on a substrate (deposition base material) 10 as shown in FIG. 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. A coating layer 23 is formed on the surface. These film forming materials will be described later.

The present invention is characterized in that the neutral density filter (ND 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, a substrate 10 (deposition base material; the same applies hereinafter) is mounted on a stage 31 in a chamber 30, and a target 32 is disposed so as to face the substrate 10. The vapor deposition stage 31 is constituted by a cylindrical rotary drum so as to rotate relative to the target 32. A target 32 is placed on the cathode electrode, and a sputtering voltage is applied between the stage 31 and the target 32. This sputtering voltage is supplied from, for example, a high frequency power source. Therefore, an operating gas (eg, argon gas) is introduced into the chamber 30 that is substantially in a vacuum state. Then, the working gas is in a plasma state in the chamber, and the electrons or ions move at high speed and collide with the target 32. Thereby, particles fly (sputtering phenomenon) from the target and adhere to the substrate 10.

  (2) In the present invention, the metal film layer 21 is composed of a metal material target (first target) rich in light absorption, and the dielectric film layer 22 is a dielectric material (Si, Al, etc.) target ( (Second target). The film forming pressure P of the operating gas (Ar gas, Ne gas) for sputtering the first and second targets 21 and 22 is varied, or the amount of power of the sputtering power source supplied to the target is varied. Yes. The adjustment of the sputtering conditions will be described later. Under such conditions, the dielectric film layer 22 forms a film of sputtered particles on the substrate by sputtering the dielectric material with an operating gas, A film is formed with the compound produced by irradiation with a reactive gas. That is, a film is formed on the substrate with particles of silicon, aluminum alloy or the like, and then irradiated with a reactive gas such as oxygen gas, nitrogen gas or fluorine gas. As a result, an oxide film, a nitride film, and a fluoride film are generated.

  (3) Accordingly, in the present invention, 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 a cathode electrode, the target 32 is planarly deposited with a plate-like material. It is characterized in that it is configured as a source and this plate-like material is arranged substantially parallel to the surface of the substrate 10. As shown in FIG. 3B, 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 direction of FIG. 3X-X.

  Next, the present invention is characterized in that 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 formation gap d is formed between the mask plate 34 and the substrate 10. The setting of the film forming gap d will be described later.

  In particular, at least one of the upper and lower edges 33a and 33b of the mask opening 33 perpendicular to the rotation direction of the rotary drum 31 (YY shown in FIG. 3B) is the substrate 10 and the mask plate 34 in the YY direction. To match. 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 FIGS. 3A and 3B, the film formation state at this time is such that the sputtered particles are placed in the film formation gap d on the upper edge 33a and the lower edge 33b of the mask opening 33 in the rotation axis direction YY of the drum. A gradation region 20b by diffusion 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 sputtered particles occurs from the peripheral edge (upper and lower edge and left and right edge) of the mask opening 33 in the outer peripheral direction. It is known that the diffusion of sputtered particles causes a diffusion phenomenon similar to that of light in atomic or molecular fine particles. It has been investigated that this diffusion attenuates with a cosine (cos θ) function with respect to the diffusion angle θ (cosine law).

  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. 7A, and the film thickness along the linear component indicated by Lx in FIG. Is generated. The present invention is characterized in that such film formation is formed in the direction of FIG. 4X-X 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.

  The configuration of the mask plate 34 will be described. The substrate 10 is mounted on the rotary drum 31 as shown in FIG. 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 coincides with the rotation direction (YY direction in the drawing) of the rotary drum 31. It is attached to the rotating drum 31 so as to have a line segment. 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 with respect to a desired (design value) film formation width Δx. [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. 5B, the gradation layer formed as described above had 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 2 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.
[Substrate material]
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 phthalate (PET), polyethylene naphthalate (PEN), norbornene resin or the like is used. As the other substrate material, a suitable material is selected according to the use environment.
[Dielectric material]
The aforementioned dielectric film (intermediate layer) is made of oxide, nitride, or fluoride such as silicon or aluminum. For this reason, the target 32 uses a plate-like member made of Si (silicon) or Al (aluminum).
[Metal substance]
As the metal film (attenuation layer), a metal oxide rich in light absorption such as chromel (nickel-chromium alloy), niobium (Nb) titanium (Ti), or the like is used.
[Coating layer]
As the above-mentioned coating layer 23, a hard or water-repellent material such as magnesium fluoride is used. In this case, MgO (magnesium oxide) is used as the target 32.

[Filter manufacturing equipment]
The sputtering apparatus shown in FIG. 8 will be described. The apparatus shown in FIG. 8 includes an outer casing 30a that forms a chamber 30, a cylindrical rotating drum 31 that is rotatably housed in the chamber 30, and a sputter that is disposed at a distance from the rotating drum 31. It is comprised with the electrode 35. FIG.

  The inside of the chamber 30 is formed in a vacuum, and therefore a vacuum pump (not shown) is provided. 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 first 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”). The second area 36b for sputtering the “dielectric target”, the third area 36c for sputtering the third target 32c for forming the coating layer 23 (hereinafter referred to as “coat layer target”), and the active gas irradiation. 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.

  The pair of sputter electrodes 35a and 35b are connected to a high-frequency AC power supply, 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. An active gas (oxygen gas, nitrogen gas, fluorine gas, etc.) is supplied to the fourth area 36d from a supply cylinder 38g via a controller 38.

A reactive gas generation chamber 39 is provided in the fourth area 36d, and is configured so that the gas from the supply cylinder 38g is turned into plasma and irradiated 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.

  After the metal film layer 21 and the dielectric film layer 22 are laminated in a plurality of layers as described above, the coating layer target 32c in the third area 36c is sputtered to attach the coating layer 23 to the uppermost layer.

  As described above, in the present invention, when the neutral density filter (ND filter) 43 is formed, the substrate 10 and the mask plate 34 are mounted on the rotary drum 31, and the planar vapor deposition source (described above) is parallel to the substrate 10. A film component is sputtered from each target) 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.

  As described above, when the gradation region 20b is formed on the upper and lower edges of the mask opening 33 orthogonal to the rotation direction of the rotating substrate 10, the above-described metal film layer 21 and dielectric film layer 22 can be used to apply "sputter power supply". It is characterized by “adjusting the voltage”, “adjusting the deposition pressure of the working gas”, or “adjusting the mass of the working gas”. Hereinafter, these configurations will be described.

[Adjustment of sputtering power supply voltage]
A power supply coil 35c is connected to the sputter electrodes 35a and 35b, and an AC power supply 35f is supplied to the power supply coil 35c (see FIG. 8). Therefore, the voltages supplied to the first area 36a and the second area 36b are made different. This voltage increase / decrease adjustment is performed by, for example, varying the bias voltage applied to the rotary drum 31 described above.

  Accordingly, the kinetic energy of the sputtered particles from the rotary drum 31 equipped with the substrate 10 and the first, second, and third targets 32a, 32b, and 32c varies depending on the target and the substrate. Therefore, as will be described later, when the first target 32a is sputtered to deposit the metal film layer 21 on the substrate 10, the applied voltage w1 and the second target 32b are sputtered to deposit the dielectric film layer 22 on the substrate 10. The applied voltage w2 is made different so that the latter becomes larger (w1 <w2). The voltage w3 when attaching the surface coating layer 23 is also set large (w1 <w3).

[Deposition pressure adjustment]
Operating gas (argon gas, neon gas) is supplied from the cylinder 38g to the first area 36a, the second area 36b, and the third area 36c. The gas pressure in this area is adjusted by a controller (not shown) in the adjustment valve 38v of the introduction port 38i and the adjustment valve 38w of the discharge port 38t. Therefore, it is possible to adjust the film forming pressure of the active gas in the area by adjusting each of the adjusting valves 38v and 38w. Therefore, as described later, the working gas deposition pressures in the first area 36a for sputtering the first target (metal material) 32a and the second area 36b for sputtering the second target (dielectric material) 32b are different. Make it. The film formation pressure P2 in the second area is set larger than the film formation pressure P1 in the first area (P1 <P2). Then sputtered particles fly from the target is reached or the mask plate 34 while colliding with rough operating gas ions (Ar ^+, etc.), and reaches the mask plate 34 while colliding with the dense gas ions. Therefore, the diffusion amount of the sputtered particles diffusing from the mask plate into the film formation gap d is small (small) in the former and large (large) in the latter.

[Description of dielectric film and metal film deposition process]
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. 5, which illustrates the case where the film forming pressure is changed (the same applies when the power supply amount is changed). As shown in FIG. 5A, when the first metal film layer 21 is formed on the substrate 10, the film forming pressure of the operating gas is set to a predetermined pressure P1 (for example, Pa). At this time, the film forming 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 working gas supplied to the second area 36b when the target 32b is sputtered is formed. The pressure P2 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, the first film formation described above (FIG. 5). The film forming conditions (film forming pressure P1, diffusion angle θ1) similar to (a)) are set. As a result, a film having a linear concentration gradient is obtained as in the first film layer.

  Next, in the case where a dielectric film is formed on the first metal film, the second dielectric film, and the third metal film shown in FIG. 6D, the second film formation condition (FIG. Similarly to 5 (b), the film forming pressure P2 and the diffusion angle θ1) 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. 6F shows the film layer structure of the final product film formed as described above. The uniform film layer (equal concentration region) is configured such that the dielectric film layer and the metal film layer each have a predetermined thickness, and in the gradation region, the film thickness gradually decreases linearly. 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. 6G, the film edge is formed such that the metal film layer is “zero” and the dielectric film layer is “Δh”.

  Furthermore, the present invention is characterized in that the film forming pressure is adjusted by adjusting the amount of operating gas introduced by the controller 38 described above. By adjusting the film forming pressure, the edge width of the dielectric film layer 22 and the metal film layer 21 can be matched with each other in the film forming width (the aforementioned Δx) of the gradation region 20b. In other words, since the thickness gradient (concentration gradient) of the gradation region 20b is set for each film layer by adjusting the pressure of the operating gas, for example, the thickness gradient of the dielectric film layer 22 and the thickness gradient of the metal film 21 are individually set. I can do it.

"Explanation of light intensity adjustment device"
As shown in FIG. 9, 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 substrate 40 and an optical path opening 41 formed in the substrate 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, the ND filter 43 is attached to the narrowed portion 42x of the one blade 42a. The ND 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.

It is a model figure of the film-forming method of the conventional neutral density filter, (a) is explanatory drawing of an apparatus structure, (b) is explanatory drawing of the arrangement configuration of a board | substrate and a mask board. It is a model figure of the film-forming method of the conventional neutral density filter shown in FIG. 1, (a) is a film-forming model of a gradation film layer, (b) is expansion explanatory drawing of the state formed into the film | membrane on the board | substrate. FIG. 4 is a conceptual explanatory diagram of a film forming method according to the present invention, and is a model diagram for causing vapor deposition components to fly from a target. The arrangement | positioning relationship between the board | substrate with which the rotating drum was mounted | worn and a target is shown. It is a film forming method of the neutral density filter according to the present invention, (a) shows the film formation of the first layer, (b) shows the film formation of the second layer, (c) shows the film formation of the third layer. It is explanatory drawing. FIG. 4 shows a method for forming a neutral density filter according to the present invention, wherein (d) shows film formation of the fourth layer, (e) shows film formation of a coating layer, and (f) shows a film layer cross section of the neutral density filter. It is a figure, (g) is an expanded sectional view of a gradation layer. (A) is a schematic diagram showing the relationship between the film thickness of the neutral density filter and the diffusion distance, and (b) is a diagram showing the relationship between the density of the neutral density filter and the film deposition position. The top view of a sputtering device. The perspective view which shows arrangement | positioning of a light quantity adjustment apparatus.

Explanation of symbols

d Deposition gap 10 Substrate (deposition base material)
11 Gas pressure adjusting hole 20 Thin film layer 20a Equivalent film layer 20b Gradation film layer 21 Metal film layer (first target)
22 Dielectric film layer (second target)
23 coating layer 30 chamber 30a outer casing 31 stage (rotating drum)
32 target 32a first target (metal target)
32b Second target (derivative target)
32c Third target (coat layer target)
33 Mask opening 33a Upper edge 33b Lower edge 34 Mask plate 34S Spacer member 35 Sputter electrode (35a, 35b)
35c power supply coil 36a first area 36b second area 36c third area 36d fourth area 37 shielding plate 38 controller 38g supply cylinder 38v regulating valve 38w regulating valve 39 reactive gas generation chamber 40 substrate 41 optical path opening 42 light quantity adjusting blade (42a 42b)
42x Constriction part 42y Constriction part 43 ND filter 45 Bias power supply

Claims (6)

A method of forming a neutral density filter having a neutral density film that suppresses the amount of light transmitted on a substrate,
The attenuating film is formed by laminating a plurality of targets composed of at least a first second material having different optical characteristics with an operating gas, in order of the first material and the second material,
This light-reducing film has an equal density region where the film thickness is substantially equal and a gradation region where the film thickness decreases linearly,
The gradation region is generated such that the film thickness gradually decreases due to diffusion of sputtered particles generated in a predetermined film formation gap formed between the substrate and a mask plate having a mask opening.
The gradation region includes the concentration gradient of the first substance and the second substance depending on the difference in the deposition pressure of the working gas when sputtering the target, the difference in the sputtering voltage applied to the target, or the mass difference in the working gas. A method of forming a neutral density filter, wherein the concentration gradients of the neutral density filter are different. The first material generates a light-absorbing metal film, and the second material generates a dielectric film.
2. The method of forming a neutral density filter according to claim 1, wherein the concentration gradient of the dielectric film is set to be smaller than the concentration gradient of the metal film in the gradation region. Film formation of the dielectric film and the metal film is as follows:
(1) The substrate is mounted on a cylindrical rotating drum disposed in a film forming chamber,
(2) The target is arranged with a plate-like material substantially parallel to the substrate surface,
(3) A mask plate having a mask opening is arranged on the rotating drum so as to form a predetermined film-forming gap between the substrate and the substrate.
The gradation region is formed by diffusion of sputtered particles generated in the film formation gap from a mask opening of the mask plate on upper and lower edges of the substrate orthogonal to a rotation direction of the rotating drum. Item 3. A method of forming a dark filter according to Item 2. A substrate,
It is composed of a dielectric film and a metal film formed in a laminated form on the substrate,
The dielectric film is formed by sputtering a target made of a dielectric substance with an operating gas and then irradiating a reactive gas.
The metal film is formed by sputtering a target made of a metal material with an operating gas,
The dielectric film and the metal film are
When sputtering the target, it has a gradation region in which the film thickness gradually decreases due to the diffusion of sputtered particles from the opening edge of the mask plate that forms a film formation gap with the substrate,
This gradation region is the difference in the concentration gradient of the dielectric film and the metal film due to the difference in the deposition pressure of the working gas when sputtering the target, the difference in the sputtering voltage applied to the target, or the mass difference in the working gas. A neutral density filter having different density gradients. 5. The neutral density filter according to claim 4, wherein the density gradient of the dielectric film is set to be smaller than the concentration gradient of the metal film in the gradation region. An imaging light quantity diaphragm device is arranged in the imaging optical path, and aperture blades for adjusting the imaging light quantity;
A neutral density filter attached to the diaphragm blade;
Consisting of
6. The imaging light amount diaphragm device according to claim 4, wherein the neutral density filter has the configuration according to claim 4.

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