JP2017066429A - Sputtering apparatus and method for manufacturing thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering apparatus capable of obtaining a thin film having high film thickness uniformity even when film formation by a sputtering method is performed for a long time.SOLUTION: A sputtering apparatus for forming a thin film by a sputtering method comprises a vacuum container, a mechanism for continuously conveying a substrate F in a roll-to-roll system in the vacuum container, a mechanism for generating plasma in a gap between facing surfaces of a sputtering cathode 1 and the substrate F, and a film thickness control mask 10 disposed between a target 2 disposed on the sputtering cathode 1 and the substrate F, in which the film thickness control mask 10 is made of an iron alloy (invariant steel) containing 34-37 mass% of nickel and 0-10 mass% of cobalt.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical thin film used for various optical filters and the like, a sputtering apparatus used for manufacturing a transparent thin film and a conductive thin film used for semiconductor parts, liquid crystal parts, optical disk parts, electronic devices, etc. And a method of manufacturing a thin film using the sputtering apparatus.

  In recent years, the sputtering method is generally employed as a means for forming transparent thin films and conductive thin films used in semiconductor parts, liquid crystal parts, optical disk parts, electronic devices, and the like because dense and high-quality thin films can be obtained. . Also, in the field of optical thin film, which was mainly produced by vapor deposition, in order to obtain high productivity, a roll-to-roll method was adopted, and an optical thin film was continuously formed by sputtering. The method is adopted.

  In a generally known sputtering method, under an argon gas atmosphere of about 10 Pa or less, a substrate is used as an anode, a target is used as a cathode, a glow discharge is caused between them, and argon is brought into a plasma state. A thin film is formed by colliding a cation with a target of a cathode, thereby repelling particles of a target component and depositing the particles on a substrate.

  Sputtering methods are classified according to the method of generating argon plasma, and are roughly classified into a direct current sputtering method using direct current plasma and a high frequency sputtering method using high frequency plasma. In addition, the DC sputtering method uses a magnetron sputtering method in which a magnet is disposed on the back side of the target so that argon plasma is concentrated directly on the target and the argon ion collision efficiency is increased even under a low gas pressure. There is a magnetron sputtering method. Furthermore, there is a high-frequency superimposed DC sputtering method using a plasma with a high frequency superimposed on the basis of a DC magnetron sputtering method, which has a feature that the discharge voltage can be lowered. The direct current magnetron sputtering method and the high frequency superimposed direct current sputtering method are mainly applied when an oxide thin film such as a transparent conductive film using an oxide target is produced on an industrial scale.

  Sputtering methods are broadly divided into static facing sputtering methods and in-line sputtering methods from the viewpoint of operational methods. In the stationary facing sputtering method, in a vacuum vessel, the substrate moves immediately above the target and is stationary, then plasma is generated on the target, and a film formation process is performed for a predetermined time. When the film is formed on the substrate, the discharge is stopped to stop the film formation, and then the substrate is moved away from the target.

  On the other hand, the in-line sputtering method allows a substrate to be transported and approached at a constant moving speed on a target that continuously generates and maintains argon plasma in a vacuum vessel, and passes without stopping. It is the method of forming into a film. The thin film thickness can be determined relatively easily by controlling the power applied to the target and the conveyance speed, and in-line sputtering is possible because of the characteristics of the construction method that enables uniform film formation on a large area substrate. The law is most widely used industrially. In the in-line sputtering method, for example, a resin film is transported as a long substrate by a roll-to-roll method.

  In either method, in order to generate plasma during film formation by sputtering, the gas is supplied into the vacuum vessel while evacuation is performed to control the inside of the vacuum vessel to a predetermined pressure, and the target and High frequency power or DC power is applied between the substrates. Usually, the high frequency power or DC power applied at this time is proportional to the film forming rate. Therefore, in order to improve productivity, a larger amount of electric power is applied as long as there is no thermal influence on the substrate to be used or the film to be formed. In addition, since the deposition rate can be increased by setting the distance between the target and the substrate to be small, the distance between the target and the substrate is usually set to be smaller.

  In the magnetron sputtering method, a difference in plasma density occurs due to the magnetic field formed by the magnet placed on the back side of the target, forming a region where the sputtering phenomenon is likely to occur (erosion region) and a region where the sputtering phenomenon is difficult to occur (non-erosion region). Is done. Specifically, in the region where the parallel component of the magnetic field is large, the density of the cyclone-moving electrons increases, so the portion of the target that has a high plasma concentration below the parallel component of the magnetic field becomes the erosion region, The other part is a non-erosion region. According to the shape of the erosion region and the shape of the target, a film thickness control mask is arranged between the target on the sputtering cathode and the substrate, and the shape of the opening of the film thickness control mask is adjusted. Thus, it is possible to increase the uniformity of the film thickness by controlling the film thickness of the thin film to be formed (JP-A-1-240661).

  The sputtering method has a problem that the sputtering state becomes unstable due to generation of nodules and particles formed on the target during film formation. Generation of such nodules and particles may lead to a failure of the thin film device due to generation of abnormal discharge or formation of a cluster-like film. The particles are fine particles derived from the target material in which deposits deposited on the non-erosion region of the target, the inner wall of the sputtering apparatus and its internal components, or the film thickness control mask are peeled off and dropped from these components. Powder or flakes. A nodule is a foreign substance that precipitates on the surface of the target as the sputtering time elapses, and causes abnormal discharge and generation of particles. Defects in the thin film device occur due to the occurrence of abnormal discharge and the scattering of particles onto the substrate surface.

  As a measure for preventing the generation of nodules and particles, it is conceivable to prevent deposits from being deposited on the inner wall and internal components of the sputtering apparatus other than the substrate. Specifically, before the peripheral portion of the substrate, the shield, the backing plate, the shutter, the target (non-erosion region), and the deposits fixed to the constituent members such as the support become thick and peel and fall off. In addition, measures are taken such as periodically cleaning these constituent members or replacing these constituent members. In addition, for a component member on which a large amount of deposits are deposited, a metal spray coating is formed on the surface of the component member in advance (Japanese Patent Laid-Open No. 61-56277), or physical surface roughness such as blasting is performed. It has been proposed to keep the deposits on these constituent members and prevent their peeling and dropping by applying a chemical treatment (Japanese Patent Laid-Open No. 62-142758).

  In addition, it prevents the target component material that has jumped out of the target from reaching the substrate or the component between the target on the sputtering cathode and the substrate when the initial plasma is unstable or between the target and the internal component. A landing plate is arranged. Since deposits are very easy to deposit on such an adhesion-preventing plate and film thickness control mask, the surface of these adhesion-prevention plate and film thickness control mask is previously subjected to sandblasting (Japanese Patent Laid-Open No. 3-138354). ) By using a material that reduces the difference between the coefficient of linear expansion and the coefficient of linear expansion of the target material as a material for these deposition prevention plates and film thickness control masks (JP-A-2-285067), It has been proposed to prevent the deposits from peeling off and dropping off from the deposition plate or the film thickness control mask.

  In sputtering, especially when forming a thick film, or when forming a thin film continuously over a long period of time using a roll-to-roll method, a substrate, a deposition plate around the substrate, a film thickness control mask, etc. Is exposed to plasma with a significant temperature rise. In particular, the shape of the opening of the film thickness control mask plays a role in controlling the film thickness uniformity of the thin film, but thermal expansion occurs in the film thickness control mask due to the rise in temperature during film formation. The shape of the opening may change. In such a case, there arises a problem that uniformity of a predetermined film thickness cannot be ensured. In particular, in multilayer films for optical components, the thickness of each layer is designed in accordance with the light interference conditions, so the inability to sufficiently control the thickness has a significant impact on the quality. become.

  For example, Japanese Patent Laid-Open No. 2013-225105 discloses the production of an optical thin film in which an oxide dielectric film or a metal film is continuously formed by a roll-to-roll method. Since the above continuous film formation is required, the uniformity of the thin film formed from the start to the end of the film formation is maintained due to the change in the shape of the opening due to the temperature rise of the film thickness control mask. Is difficult. In this way, the continuous film formation method adopting the roll-to-roll method cannot make the production length per batch sufficiently long so that the characteristics of the obtained thin film do not vary. There arises a problem that it is difficult to control.

  For the purpose of controlling the amount of light incident on the solid-state imaging device, an ND filter (gradation ND filter) designed so that the transmittance gradually changes in a certain direction of the thin film has been proposed. In the production of such a gradation ND filter, an oxide dielectric film and a metal film are defined by using a roll-to-roll method and defining a sputtering area with respect to the substrate using a film thickness control mask having a predetermined shape. The film is formed by magnetron sputtering while controlling the film thickness (Japanese Patent Laid-Open No. 2003-322709). Even in such a case, depending on the sputtering conditions, the shape of the film thickness control mask is deformed such as a curve as the temperature rises, and the gradation density distribution changes depending on the film formation time. It is difficult to produce a film continuously and constantly.

JP-A-1-240661 JP-A-61-56277 Japanese Patent Laid-Open No. 62-142758 Japanese Patent Laid-Open No. 3-138354 JP-A-2-285067 JP 2013-225105 A JP 2003-322709 A

  The present invention has been made to solve the technical problems as described above, and includes a vacuum container, a mechanism for continuously transporting a substrate in a roll-to-roll manner in the vacuum container, and the vacuum. A mechanism for supplying and evacuating the gas into the vessel, a mechanism for maintaining a constant gas pressure in the vacuum vessel, and plasma in a gap between the sputtering cathode and the opposing surface of the substrate. A sputtering apparatus for forming a thin film by a sputtering method, comprising: a mechanism for generating the film; and a film thickness control mask disposed between the target disposed on the sputtering cathode and the substrate. Even when film formation is performed for a long time, it is possible to produce a thin film continuously and consistently without changing the film thickness uniformity. For the purpose.

  As a result of diligent study, the present inventor paid attention to the heat generated by the generation of plasma during film formation, and made the film thickness control mask disposed between the target and the substrate with a material that is not easily deformed by heat. By configuring, it was found that it is possible to produce a thin film continuously and consistently without losing the uniformity of the film thickness even in the film forming process by a long sputtering method, and the present invention was completed. It came to do.

  That is, according to one embodiment of the present invention, plasma is generated in a vacuum container, a mechanism for continuously transporting a substrate in a roll-to-roll manner in the vacuum container, and a gap between the sputtering cathode and the facing surface of the substrate. And a film thickness control mask disposed between the target disposed on the sputtering cathode and the substrate, and a sputtering apparatus for forming a thin film by a sputtering method. In the present invention, the concept of the film thickness control mask is that the target constituent material that has jumped out of the target is arranged so as not to reach the substrate or other internal constituent members, that is, a film thickness control mask is used to control the film thickness to zero. A landing plate is also included.

  In particular, in the sputtering apparatus of the present invention, the film thickness control mask is made of an iron alloy (invariant steel) containing 34 mass% to 37 mass% nickel and 0 to 10 mass% cobalt. It is characterized by that.

  Another aspect of the present invention relates to a method for producing a thin film by a sputtering method. The thin film manufacturing method uses a sputtering apparatus, exhausts gas from the vacuum container while supplying gas into the vacuum container of the sputtering apparatus, controls the inside of the vacuum container to a predetermined pressure, and roll-to-roll. The substrate is transported continuously by this method, high frequency power or direct current power is applied between the sputtering cathode and the substrate, and plasma is generated in the gap between the target disposed on the sputtering cathode and the opposing surface of the substrate. And a step of forming a thin film on the substrate.

  In particular, in the method for producing a thin film of the present invention, the sputtering apparatus of the present invention is used, two or more types of targets selected from a dielectric material and a metal material are arranged, and a selection is made from a dielectric film and a metal film. A laminated film in which two or more kinds of thin films are laminated is formed on a substrate.

  The method for producing a thin film of the present invention is suitably applied when producing a thin film in which at least one thin film constituting the laminated film has an in-plane thickness gradient.

  In addition, the thin film manufacturing method of the present invention is particularly a laminate in which the dielectric material is silicon oxide, the metal material is a nickel alloy, and the silicon oxide thin film and the nickel alloy thin film are alternately laminated. It is suitably applied when forming a film.

  In the sputtering apparatus and the thin film manufacturing method using the apparatus according to the present invention, the film thickness control mask including the deposition preventing plate is made of a material having a small dimensional change due to heat. The film thickness control due to the deformation of the part can be eliminated, so even when the film is formed by sputtering for a long time using the roll-to-roll method, the film thickness is kept uniform and constant. Thus, a thin film can be manufactured.

  Further, in the conventional sputtering apparatus, operational measures such as cleaning and replacement of the deposition preventive plate and the film thickness control mask, which are required when operating continuously for a long time, are unnecessary in the present invention. Furthermore, in the sputtering apparatus of the present invention, the quality of the thin film is maintained even if the film forming speed is increased by operating at a higher sputtering power within a range that does not affect the film characteristics of the substrate and the film to be formed. .

  Thus, according to the present invention, not only optical thin films that require appropriate control of film thickness, but also transparent thin films and conductive thin films used in semiconductor parts, liquid crystal parts, optical disk parts, electronic devices, etc. Also in this field, since it is possible to sufficiently improve the productivity and reduce the cost, the industrial significance of the present invention is great.

FIG. 1 is a schematic view showing an example of a roll-to-roll type sputtering apparatus to which the present invention is applied. FIG. 2 is a schematic view showing another example of a sputtering apparatus using a roll-to-roll method to which the present invention is applied. FIG. 3 is a schematic view showing an example of the film thickness control mask of the present invention. FIG. 4A is a schematic diagram showing another example of the film thickness control mask of the present invention, and FIG. 4B shows the formation of a thin film formed using another example of the film thickness control mask. It is the schematic which shows an example of a pattern. FIG. 5 is a graph showing the spectral transmission characteristics of the absorption multilayer ND filter according to an embodiment of the present invention.

  Hereinafter, specific embodiments of the present invention will be described in detail.

1. Sputtering equipment (basic configuration)
A basic structure of a sputtering apparatus to which the present invention is applied is for continuously supplying a substrate by a general roll-to-roll method as shown in FIG. 1 and for forming a thin film on the surface of the substrate. The structure is the same as that of the sputtering apparatus. Specifically, the sputtering apparatus according to an example of one embodiment of the present invention includes a vacuum container 3 that is a vacuum container, and a long resin film F that is a substrate in a roll-to-roll manner in the vacuum container 3. An unwinding roll 4, a cooling drum 5, a winding roll 6, and a guide roll 7, which are mechanisms for continuous conveyance, and a mechanism for supplying gas into the vacuum container 3 and exhausting it from the vacuum container 3 ( (Not shown), a mechanism (not shown) for maintaining the gas pressure in the vacuum vessel 3 constant, and a mechanism for generating plasma in the gap between the facing surfaces of the sputtering cathodes 1a to 1c and the resin film F (see FIG. And a film thickness control mask 10 disposed between the sputtering targets 2a to 2c and the resin film F respectively disposed on the sputtering cathodes 1a to 1c. While the sputtering targets 2a to 2c are respectively disposed on the ring cathodes 1a to 1c, and the film thickness control mask 10 is disposed between the resin film F and the sputtering targets 2a to 2c, the resin film F is being conveyed. The thin film is formed on the resin film F by sputtering.

  Note that the sputtering apparatus of this example is particularly characterized by the structure of the film thickness control mask including the deposition preventing plate, and the same internal mechanism as the conventional sputtering apparatus can be adopted. It is.

  In the sputtering apparatus of this example, the sputtering cathodes 1a to 1c are disposed on the back side of the backing plate to which the sputtering targets 2a to 2c are bonded, respectively, and the housing cover having the cooling water jacket and further on the back side of the housing cover. A magnetic generation mechanism is provided. That is, in this example, a direct current magnetron sputtering method or a high frequency superimposed direct current sputtering method is employed.

  However, the present invention is not limited to a roll-to-roll film forming method, and is not limited to a film forming method by a direct current magnetron sputtering method or a high frequency superimposed direct current sputtering method. The present invention can be widely applied to a sputtering method that requires a film thickness control mask to be included.

  In the sputtering apparatus of this example, the sputtering targets 2a to 2c are placed on the sputtering cathodes 1a to 1c so as to face the resin film F, which is a long substrate conveyed in a roll-to-roll method, in the vacuum vessel 3. In the vacuum container 3 that is disposed and decompressed, the long resin film F is unwound from the unwinding roll 4, conveyed by the guide roll 7 or the cooling drum 5, and wound around the winding roll 6. By applying a high frequency or direct current power between the resin film F, plasma is generated in the gap between the facing surfaces of the sputtering targets 2a to 2c and the resin film F, and the target constituent material jumped out of the sputtering targets 2a to 2c Is deposited on the surface of the resin film F to form a thin film.

  The sputtering targets 2a to 2c are arranged on the sputtering cathodes 1a to 1c, respectively, such that the long side direction is substantially parallel to the width direction of the resin film and faces the cooling drum 5. A coolant such as cooling water supplied from the outside of the vacuum vessel 3 is supplied inside the cooling drum 5 to cool the resin film F during film formation. Further, between the upper side of the vacuum vessel 3 where the unwinding roll 4 and the winding roll 6 of the resin film F are arranged, and the film forming side where the sputtering cathodes 1a to 1c are arranged, and adjacent sputtering cathodes. Between 1a-1c, the partition plate 8 for preventing mixing of sputtering particles and film formation atmosphere gas is arrange | positioned, respectively.

(Thickness control mask)
In the gap between the facing surfaces of the sputtering targets 2a to 2c and the resin film F, the target constituent material that has jumped out of the sputtering targets 2a to 2c is the resin film until the plasma is stabilized after the plasma is generated. The deposition preventing plate (not shown) configured not to reach the substrate F and the film thickness control mask 10 are arranged so as to overlap each other. After the plasma is stabilized, only the deposition preventing plate is moved, and only the film thickness control mask 10 having an opening is arranged in the gap between the facing surfaces of the sputtering targets 2a to 2c and the resin film F. To. When the target constituent material that has jumped out of the sputtering targets 2 a to 2 c reaches the resin film substrate F through the opening of the film thickness control mask 10, a thin film is formed on the surface of the resin film F.

  The above operations for the deposition preventing plate (not shown) and the film thickness control film 10 are performed for all the deposition preventing plates (not shown) when the sputtering targets 2a to 2c are used for film formation. When sputtering is performed using only a selected target among the sputtering targets 2a to 2c, it is only necessary to perform an operation on the deposition preventing plate (not shown) of the target to be operated.

  Although not shown in FIG. 1, a deposition plate (not shown) configured so that the target constituent material jumping out of the sputtering targets 2 a to 2 c does not reach the internal constituent member during film formation is used as a sputtering target. It is preferable to arrange | position between 2a-2c and these internal structural members.

In general, the constituent material of the film thickness control mask 10 including these deposition prevention plates is made of an aluminum material, or a peeling process by etching or the like on an aluminum material or an adhering material scattered during preliminary sputtering or film formation. In consideration of ease, stainless steel is used. Since these film thickness control masks 10 are installed in the vicinity of the region where the plasma exists, the temperature may rise to several hundred degrees during the film formation for a long time. In the case of an aluminum material, since the linear expansion coefficient in the vicinity of room temperature (0 ° C. to 200 ° C.) of aluminum is about 23 × 10 ⁻⁶ / ° C., a dimensional change of about 0.2% is caused by a temperature rise of 100 ° C. It will be. That is, in the case of a 300 mm wide mask, it is deformed by about 0.6 mm, and the influence on the film thickness distribution cannot be ignored. In the case of stainless steel, depending on the type, the linear expansion coefficient of stainless steel is about 10 to 17 × 10 ⁻⁶ / ° C., and the dimensional change is about 0.1% to 0.2% with a temperature increase of 100 ° C. Thus, in the case of a 300 mm wide mask, the deformation is about 0.3 mm to 0.6 mm.

In the sputtering apparatus of this example, an iron alloy containing 34 mass% to 37 mass% nickel and 0 to 10 mass% cobalt as a constituent material of the film thickness control mask 10 including the deposition preventing plate, that is, invariant steel. Is used. The iron alloy having this composition is generally called an Invar (registered trademark) alloy. The iron alloy, linear expansion coefficient at around room temperature (0 ° C. to 200 DEG ° C.) is 1.2 × ^{10 -6} / ℃ about or less ^{(0.5 × 10 -6 /℃~1.0 -6 /} ℃ about) And has a low value. This low-expansion mechanism of the iron alloy is explained by an interaction caused by a very large spontaneous volume magnetostriction, generally called “invar effect”. In this example, the iron alloy used as a member of the film thickness control mask 10 is particularly an Invar (registered trademark) alloy (Fe-35% to 36% Ni alloy, expansion coefficient of about 1 to 1.2 × 10 ^−6. ), And Super Invar® alloy (Fe-32% -34% Ni-4% -6% Co prepared by alloying 4% -6% cobalt in the Fe-Ni alloy matrix) An alloy having an excellent characteristic that the linear expansion coefficient near normal temperature is 0.5 × 10 ⁻⁶ / ° C. or lower and lower than that of the Invar alloy can be given as a preferred example.

  In such a film thickness control mask 10 using an iron alloy containing 34 mass% to 37 mass% nickel and 0 to 10 mass% cobalt, 0.005% to 0 at a temperature increase of 100 ° C. Only dimensional change of about 012%. That is, even with a 300 mm wide mask, the deformation is only about 0.015 mm to 0.036 mm.

  A book using an iron alloy (invariant steel) containing 34 mass% to 37 mass% nickel and 0 to 10 mass% cobalt as a constituent material of the film thickness control mask 10 including the deposition preventing plate. The sputtering apparatus of an example is especially effective in the structure of the roll-to-roll system in which a board | substrate (resin film F) is conveyed continuously. That is, by using an Invar (registered trademark) alloy with a small thermal expansion as the material of the film thickness control mask, it becomes possible to keep the influence of thermal deformation very slight, and even in a film forming process by a long-time sputtering method, It is possible to continuously produce a thin film while maintaining the uniformity of the film thickness.

  Moreover, since the film thickness uniformity during mass production is improved by manufacturing a thin film using the sputtering apparatus of this example, the film thickness of the sputtering apparatus of this example is required to be controlled with higher accuracy. It is particularly preferably applied to the production of thin films for optical components. For example, for the production of an absorption multilayer ND filter provided with an absorption multilayer film constituted by alternately laminating oxide dielectric films and metal films, the thickness of the inserted metal film is Since the thickness is about several nanometers, it becomes possible to efficiently manufacture the sputtering apparatus of this example by taking advantage of the feature of suppressing the film thickness fluctuation during mass production. Similarly, it can also be suitably applied to the production of gradation ND filters (ND filters designed so that the transmittance gradually changes in a certain direction of the thin film), which is a thin film for optical components. Since this gradation ND filter is manufactured by gradually changing the film thickness formed on the substrate (in-plane film thickness inclination), precise control is required for the film thickness. The roll-to-roll method can be adopted by utilizing the feature of suppressing the film thickness fluctuation during mass production of the sputtering apparatus, and the production can be performed efficiently.

2. Thin Film Manufacturing Method Using Sputtering Apparatus A thin film manufacturing method according to an example of one embodiment of the present invention uses, for example, the sputtering apparatus shown in FIG. 1 and supplies a gas to the vacuum container 3 of the sputtering apparatus while supplying a vacuum container. 3 is evacuated, the inside of the vacuum vessel 3 is controlled to a predetermined pressure, and the resin film F as a substrate is continuously conveyed by a roll-to-roll method, and between the sputtering cathodes 1 a to 1 c and the resin film F. A process of generating a thin film on the resin film F by applying high-frequency power or DC power to generate plasma in the gap between the facing surfaces of the sputtering targets 2a to 2c and the resin film F disposed on the sputtering cathodes 1a to 1c. Is provided.

  In particular, the thin film manufacturing method of the present example includes an adhesion preventing plate made of an iron alloy (invariant steel) containing 34 mass% to 37 mass% nickel and 0 to 10 mass% cobalt. It is characterized in that a sputtering apparatus provided with the film thickness control mask 10 is used.

(Method for manufacturing absorption multilayer ND filter)
For example, when an absorption type multilayer ND filter is manufactured using the sputtering apparatus shown in FIG. 2, for example, one of the sputtering cathodes 1 a and 1 b is replaced with two sputtering cathodes by using two sputtering cathodes. A dual magnetron sputtering method is used in which the sputtering targets installed on the sputtering cathodes are alternately discharged, and an oxide dielectric film is formed by the dual magnetron sputtering method. On the other hand, a film thickness control mask 10a having an opening 11a having the shape shown in FIG. 3 is installed between another sputtering cathode 1b and the resin film F, and the DC magnetron sputtering method is performed while correcting the film thickness. Thus, a metal film is formed. By using the film thickness control mask 10a having the opening 11a having such a shape, it becomes possible to form a metal film having a thickness of several nanometers continuously and constantly while maintaining the film thickness uniformity. . In addition, about the shape of the opening part 11, the film | membrane which has the opening part shape from which the film-forming test of arbitrary number of times is performed beforehand using the film thickness control mask from which an opening part shape differs, and desired film thickness uniformity is obtained. The optimization can be achieved by selecting the thickness control mask 10a.

(Manufacturing method of gradation ND filter)
The present invention can also be suitably applied to the production of a gradation ND filter (an ND filter designed so that the transmittance gradually changes in a certain direction of the thin film), which is a thin film for optical components. . This gradation ND filter is designed so that the transmittance gradually changes in a certain direction of the thin film. Specifically, the film thickness of the metal film formed on the substrate is gradually changed (in-plane film thickness). (Tilt).

  In this example as well, the sputtering apparatus shown in FIG. 2 is used, but this in-plane thickness-inclined structure uses a film thickness control mask 10b having a plurality of triangular openings 11b shown in FIG. By forming the film while being placed between the target 2b for forming the film and the resin film F, a metal film having the film formation pattern shown in FIG. 4B can be formed.

  For the gradation ND filter, for example, an oxide dielectric film is formed by applying an absorption multilayer ND filter manufacturing method, and a metal film is inclined in the in-plane thickness on the oxide dielectric film. In addition, an oxide dielectric film, a metal film having an in-plane thickness gradient, and an oxide dielectric film are sequentially formed thereon.

  By using the sputtering apparatus of this example provided with such film thickness control masks 10, 10a, and 10b, the linear expansion coefficient of the material constituting the film thickness control masks 10, 10a, and 10b is extremely low. Even when film formation is performed over a wide range, the deformation of the film thickness control masks 10, 10a, 10b due to heat and the shapes of the openings 11a, 11b of the film thickness control masks 10, 10a, 10b due to this deformation change. It is suppressed.

(substrate)
In any embodiment, the long resin film F as a substrate is unwound from the unwinding roll 4, transported by the guide roll 7 or the cooling drum 5, and sputtered while being wound around the winding roll 6. A thin film is formed on F. Although the material which comprises a resin film is not specifically limited, What is transparent is preferable, When considering mass productivity, it is preferable that it is a flexible substrate which can be formed into a film with a dry-type sputtering roll coater. A flexible substrate is superior in that it is cheaper, lighter, and more deformable than a conventional glass substrate. It is also suitable for press cutting.

  Specific examples of the resin film F include resin films selected from polyethylene terephthalate (PET), polyether sulfone (PES), polyarylate (PAR), polycarbonate (PC), polyolefin (PO), and norbornene resin materials. Examples thereof include a single body or a composite of a single resin film selected from the above resin materials and an acrylic organic film covering one or both sides of the single body. In particular, as for norbornene resin materials, representative examples include ZEONOR (registered trademark) manufactured by Nippon Zeon Co., Ltd. and ARTON (registered trademark) manufactured by JSR Corporation.

(Metal film)
In an absorptive multilayer ND filter composed of a laminated film in which an oxide dielectric film and a metal film are alternately laminated, the metal film functions as an absorbing film. A nickel (Ni) alloy is mainly used as a target for forming such a metal film serving as an absorption film. This is because nickel alone or a nickel alloy is relatively hardly oxidized even when applied to an absorption film, and does not lower the extinction coefficient of the absorption film. However, since pure nickel material is a ferromagnetic material, the leakage magnetic field is weak at the initial stage of film formation, and it is difficult to concentrate the plasma efficiently and to form the film efficiently. Therefore, there is a problem that the film forming speed is changed and it is difficult to control the film thickness when the film is continuously formed for a long time. Therefore, one or more elements selected from titanium (Ti), aluminum (Al), vanadium (V), tungsten (W), tantalum (Ta), and silicon (Si) are added instead of nickel alone. It is preferable to use a target made of a nickel alloy. Each addition amount is appropriately determined from the viewpoint of weakening the ferromagnetic properties of nickel and preventing the formation of a large amount of intermetallic compounds.

  The thickness of each metal film in the laminated film is preferably 3 nm to 20 nm. If the thickness of the metal film is less than 3 nm, the metal film layer becomes too thin and oxidation inside the metal film layer may proceed. On the other hand, if it exceeds 20 nm, the spectral transmittance may be reduced.

(Dielectric film)
As the dielectric film of the absorption multilayer film, a silicon dioxide (SiO ₂ ) film can be applied as in the conventional case. In this case, silicon, silicon carbide (SiC), or a film forming material containing silicon as a main component can be used as a target. Using such a target, it is preferable to obtain a SiO _x (1.5 <x <2) film having an extinction coefficient of 0.005 to 0.05 at a wavelength of 550 nm. This is because this film is weak in oxidizing an adjacent metal film even in a high temperature and high humidity environment. In addition, as the dielectric film, a magnesium fluoride (MgF ₂ ) film or an alumina (Al ₂ O ₃ ) film can also be applied.

  The thickness of each dielectric film in the laminated film is preferably 3 nm to 150 nm. If the film thickness of the dielectric film is less than 3 nm, it does not function sufficiently as an optical thin film, and it becomes difficult to control the film thickness. On the other hand, if it exceeds 150 nm, the function of controlling the extinction coefficient at a wavelength of 550 nm cannot be further improved, and the production efficiency is lowered.

(Manufacture of multilayer films)
When an absorption multilayer ND filter composed of a laminated film in which an oxide dielectric film and a metal film are alternately laminated is manufactured, for example, the metal film is formed by direct current while introducing Ar gas using a nickel alloy target. The film is formed by magnetron sputtering. At this time, the film thickness control masks 10, 10a, 10b are selectively applied according to the use and the properties of the thin film to be formed.

On the other hand, the SiO ₂ layer is formed by performing dual magnetron sputtering while introducing Ar gas using a target appropriately selected from the Si-based targets described above, and further introducing oxygen to change the composition and structure of the oxide. Film. In the dual magnetron sputtering method, sputtering is performed to suppress the occurrence of arcing by alternately applying medium frequency (40 kHz) pulses to two targets in order to form an insulating film at high speed, thereby preventing the formation of an insulating layer on the target surface. Is the method. By performing these in an appropriate procedure, an absorption multilayer film in which oxide dielectric films and metal films are alternately laminated can be formed.

More specifically, when the sputtering apparatus shown in FIG. 2 is used,
1) The inside of the vacuum vessel 3 is exhausted to 1 × 10 ⁻⁴ Pa.
2) The resin film F is transported in the forward rotation direction after setting a transport speed at which a desired oxide dielectric film thickness is obtained.
3) was placed in a sputtering cathode 1a a Si target 2a, and, in the state in which the film thickness control mask 10, an Ar gas was introduced to the Si target side, while introducing oxygen at the same time, the dual magnetron sputtering, SiO ₂ Forming a film,
4) The resin film F is transported in the reverse direction after setting a transport speed at which a desired metal film thickness can be obtained.
5) The Ni alloy target 2b is installed on the sputtering cathode 1b, and any one of the film thickness control masks 10a and 10b is arranged, Ar gas is introduced into the Ni alloy target side, and the metal film is formed by DC magnetron sputtering. Film formation,
Film formation is performed according to the process. In order to form a laminated film, the steps 2) to 5) are further repeated, and finally a SiO ₂ film is formed on the outermost surface. If necessary, after the film formation on one side is completed, the resin film F after the one-side film formation is rewound with the surface already formed on the inside, and set on the unwinding roll 4 again. The same film is formed on the non-film-formed surface.

  As an example, the sputtering apparatus of the present invention will be further described while illustrating the production of an absorption-type multilayer ND filter by a roll-to-roll method. In order to clarify the effect of the present invention, the uniformity of the film thickness during the manufacturing process was evaluated by measuring the optical characteristics of the manufactured ND filter.

  In addition, a following example shows only an example of this invention and this invention is not limited to the content of a present Example.

Example 1
An absorptive multilayer ND filter having an average transmittance of 6.3% at a wavelength of 400 nm to 700 nm was prepared to have the laminated film configuration shown in Table 1. For film formation, a sputtering roll coater apparatus (manufactured by Hirano Kotone Co., Ltd.) having the same configuration as that of FIG. 2 was used. A Ni target (manufactured by Sumitomo Metal Mining Co., Ltd., target size: 600 mm × 125 mm) is used as a target for forming a metal absorption film, and a Si target is used as a target for forming a SiO ₂ film as an oxide dielectric film. A target (manufactured by Sumitomo Metal Mining Co., Ltd.) was used.

Metal absorbing film (Ni film), while introducing Ar gas deposited by DC magnetron sputtering, a SiO ₂ film performs the dual magnetron sputtering while introducing Ar gas, by introducing oxygen at the same time, the SiO ₂ film Was deposited. The amount of oxygen introduced was controlled by an impedance monitor (Phon Ardennes, plasma emission monitor).

  Further, a film thickness control mask (alloy composition: 63.5% Fe-36.5Ni, size: 800 mm × 500 mm × 1 mm) shown in FIG. 3 is arranged immediately above the Ni target to control the film thickness of the metal absorption film. As a result, the density distribution of the ND filter was adjusted. Further, a PET film having a thickness of 100 μm, a width of 300 mm, and a length of 90 m was used as the resin film constituting the substrate. In addition, as a pretreatment of the film forming process, the PET film was preliminarily subjected to plasma treatment in a vacuum in order to increase the adhesion of the absorption multilayer film.

The absorption multilayer film was formed according to the following procedure.
1) The inside of the vacuum vessel 3 was evacuated to 1 × 10 ⁻⁴ Pa.
2) The resin film was conveyed in the forward rotation direction at a speed of 1.50 m / min.
3) Ar gas was introduced at 100 sccm to the Si target side, and film formation was performed by a dual magnetron with a sputtering output of 10 kW. At this time, the oxygen introduction amount was controlled by an impedance monitor (the same operation was performed in steps (7) and (11)).
4) The film was conveyed in the reverse direction at a speed of 0.94 m / min.
5) Ar gas was introduced at 100 sccm on the Ni target side, and film formation was performed by direct current magnetron sputtering at a sputtering output of 1 kW.
6) The film was conveyed in the forward direction at a speed of 0.43 m / min.
7) Ar gas was introduced at 100 sccm to the Si target side, and film formation was performed at a sputtering output of 10 kW.
8) The film was conveyed in the reverse direction at a speed of 0.94 m / min.
9) Ar gas was introduced at 100 sccm on the Ni target side, and film formation was performed at a sputtering output of 1 kW.
10) The film was conveyed in the forward direction at a speed of 0.46 m / min.
11) Ar gas was introduced at 100 sccm on the Si target side, and film formation was performed at a sputtering output of 10 kW.
12) The film on which the formation of the multilayer film on one side was completed was taken out, rewound, set upside down, and steps 1) to 11) were performed again.
13) The film in which the multilayer film was completely formed on both sides was taken out, and the film formation process was completed.

  The spectral transmission characteristics of the obtained ND filter were measured using an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, V570). FIG. 5 shows the spectral transmittance of the absorption multilayer ND filter having an average transmittance of 6.3%.

In addition, as an evaluation index of film thickness uniformity during long-time film formation, an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, V570) is used, and the wavelength is 400 nm, which is sensitive to the film thickness of the Si film. The maximum reflectance (%) between ˜700 nm was measured. This is because the SiO ₂ film is formed with high power, so the deformation of the film thickness control mask due to heat and the deviation from the target film thickness are conspicuous, and it is easy to judge the quality. is there.

  Specifically, as evaluation of film thickness uniformity during long-time film formation, a position near the start of film formation (position of 1 m in the length direction of the PET film) and a position just before the end (length of the PET film) And a position on the longitudinal center line of the film (the center in the width direction of the film) and 100 mm on both sides in the width direction of the film from the longitudinal center line of the film. A total of three points of position were compared. The results are shown in Table 2.

(Example 2)
In the film formation of Example 1, except that the alloy composition of the film thickness control mask was changed to 63% Fe-32% Ni-5% Co, the same as in Example 1 with respect to both sides of the film A multilayer film was formed.

(Comparative Example 1)
In the film formation of Example 1, a multilayer film was formed on both sides of the film in the same manner as in Example 1 except that the film thickness control mask was changed to one made of an aluminum alloy.

(Comparative Example 2)
In the film formation of Example 1, multilayer films were formed on both sides of the film in the same manner as in Example 1 except that the film thickness control mask was changed to one made of stainless steel alloy (SUS306).

[Evaluation results]
When a film formation process is performed for a long time using the film thickness control mask of the aluminum alloy material of Comparative Example 1 and the film thickness control mask of the stainless steel (SUS306) material of Comparative Example 2, the film length is about 2% at 1 m position in the film length direction. It is understood that the suppressed reflectance is increased up to about 5 to 6% at the position of 85 m in the film length direction. On the other hand, in the film thickness control masks of the 63.5% Fe-36.5Ni alloy of Example 1 and the 63% Fe-32% Ni-5% Co alloy of Example 2, the reflectance is unavoidable at the initial stage of film formation. In the range of the process variation that occurs in the film, almost no change occurs in the film length direction.

  Therefore, it can be understood that, by using the sputtering apparatus of the present invention, the film thickness variation due to the thermal deformation of the film thickness control mask is greatly reduced even if the film forming process is continued for a long time.

DESCRIPTION OF SYMBOLS 1, 1a-1c Sputtering cathode 2, 2a-2c Sputtering target 3 Vacuum container 4 Unwinding roll 5 Cooling drum 6 Winding roll 7 Guide roll 8 Partition plate 10, 10a, 10b Film thickness control mask 11a, 11b Opening part F board | substrate

Claims (4)

A vacuum vessel, a mechanism for continuously transporting the substrate in a roll-to-roll manner in the vacuum vessel, a mechanism for generating plasma in a gap between the facing surface of the sputtering cathode and the substrate, and the sputtering cathode A sputtering apparatus for forming a thin film by a sputtering method, comprising a film thickness control mask disposed between the disposed target and the substrate, wherein the film thickness control mask is 34 mass% to 37 mass%. % Of nickel and an iron alloy containing 0 to 10% by mass of cobalt. Using a sputtering device, gas is exhausted from the vacuum vessel while supplying gas into the vacuum vessel, the inside of the vacuum vessel is controlled to a predetermined pressure, and the substrate is continuously conveyed by a roll-to-roll method, and sputtering is performed. Forming a thin film on the substrate by applying high-frequency power or direct current power between the cathode and the substrate, generating plasma in a gap between the target disposed on the sputtering cathode and the facing surface of the substrate; A method for producing a thin film comprising:
The sputtering apparatus is the sputtering apparatus according to claim 1, and two or more kinds of targets selected from a dielectric material and a metal material are arranged, and selected from a dielectric film and a metal film. A method for producing a thin film, comprising forming a laminated film in which two or more kinds of thin films are laminated on a substrate.   The manufacturing method of the thin film of Claim 2 with which the at least 1 sort (s) or more of thin film which comprises the said laminated film has the in-plane film thickness inclination. 3. The thin film according to claim 2, wherein the dielectric material is silicon oxide, and the metal material is a nickel alloy, and a laminated film is formed by alternately laminating a silicon oxide thin film and a nickel alloy thin film. Production method.