JP2008195979A - Film forming apparatus and film forming method - Google Patents

Abstract

Provided is a film forming apparatus for reducing radiant heat in electron beam evaporation of an active material layer or the like used for an electrode plate for a battery, and a film forming method having excellent productivity and stability using the same. And providing a film forming method using the same. Not only for battery applications, but also to solve the heat load problem in general vacuum film forming apparatus.
This is achieved by an evaporation mechanism in which an electron beam is selectively irradiated onto a melting region divided into three or more melting surface regions by a shielding plate 37 that shields a part of the upper surface of a container 32 that holds the evaporation material 31. Do the membrane.
[Selection] Figure 1

Description

  The present invention relates to a film forming apparatus and a film forming method for performing film formation in a vacuum.

  Thin film processes are widely used as means for realizing high-performance devices, and have become a part of industrial structure. Thin film equipment is required to have high performance, high productivity and low cost, and from the viewpoint of environmental energy, high efficiency and low energy of thin film processes are being promoted. In the vacuum deposition method, which is one of the typical thin film processes, it is effective to increase the evaporation rate and the film deposition rate in order to improve productivity. In particular, in the case of the electron beam evaporation method, the evaporation rate and the film deposition rate can be increased by increasing the electron beam power supplied to the evaporation source.

  For example, a technique for forming a thin film of a silicon-based material that is actively developed as a high-capacity negative electrode active material by an electron beam evaporation method is disclosed (Patent Document 1). However, when the thin film is formed by the electron beam evaporation method or the like, the current collector as the substrate becomes high temperature. The current collector is generally a metal foil that is work-hardened by rolling or the like. It is known that when such a metal foil reaches a high temperature, mechanical strength such as tensile strength is greatly reduced by recrystallization, and the metal foil is easily deformed. In order to solve this problem, it is disclosed that a current collector as a substrate is cooled (Patent Document 2).

  However, as a constituent factor of the heat load applied to the substrate, thermal energy when the film forming material changes from the gas phase to the solid phase and radiant heat from the evaporation source occupy a large proportion. The proportion of heat load components varies depending on the equipment configuration and process conditions. For example, the proportion of radiant heat in the heat load received by copper foil when silicon-based materials are continuously deposited on the copper foil substrate. Is, for example, about 50%. Therefore, it has been desired to reduce the radiant heat in order to prevent the mechanical properties of the copper foil from being lowered.

Patent Document 3 discloses an apparatus for manufacturing an information recording medium in which a vapor flow passes through an opening divided in the width direction of a crucible and is deposited on a substrate. A conceptual diagram is shown in FIG. In this document, the evaporation material 31 is held in a molten state in a container 32. A rectifying plate 50 is installed on the container 32. Further, a substrate (not shown) is installed above the container. According to this configuration, only the vapor flow component dispersed above the container can pass through the rectifying plate 50, and the vapor flow component dispersed in the other direction can be recirculated to the crucible, so that the high efficiency of the evaporation material can be obtained. Can be made. At the same time, since a plurality of shielding plates are arranged immediately above the evaporation source, there is an effect of reducing radiant heat.
JP 2005-29389 A JP 2004-95474 A Japanese Patent Laid-Open No. 9-16960

  However, the configuration of Patent Document 3 cannot be expected to significantly reduce the radiant heat received by the substrate. Radiant heat is mainly determined by the melt temperature of the evaporation source and the upper area of the melt, but in Patent Document 3, by providing a plurality of shielding plates, the vapor flow from the evaporation source is rectified, but the upper area of the melt is Not alleviated. This is because most of the radiant heat reaches the substrate directly or reflected by the shielding plate.

The present invention solves the above-mentioned conventional problems, and provides a film forming apparatus for reducing the radiant heat received by a substrate in an electron beam vapor deposition method. The purpose is to solve the thermal load problem.

  In order to solve the above-described conventional problems, a film forming apparatus of the present invention includes a container that holds an evaporation material, a shielding plate that shields a part of the upper surface of the container, and an evaporation material held in the container. And an evaporation mechanism that selectively irradiates the melted region divided into three or more melted surface regions by the shielding plate with an electron beam, and can reduce thermal radiation.

  In addition, the film forming apparatus of the present invention can supply the evaporation material to at least one location of the melting surface region.

  The manufacturing method of the present invention is a film forming method in which deposition is performed by irradiating an electron beam onto a material held in a container and in a molten state, and the material is shielded by a shielding plate that shields a part of the upper surface of the container. The present invention is characterized in that an electron beam is selectively irradiated to the melted region divided into the above melted surface regions.

  According to the present invention, it is possible to significantly reduce the radiant heat received by the substrate by reducing the surface of the evaporation source. As a result, a film forming apparatus having an evaporation mechanism with a small thermal load on the substrate can be configured.

  Further, according to the present invention, the material supply can be easily performed. Further, the evaporation fluctuation due to the recirculation of the evaporant is less likely to occur, and the change in the evaporation source temperature is less likely to occur when the material adhering to the shielding plate is circulated into the evaporation source melt as a droplet. In addition, since the problem of splashing can be solved, a film forming apparatus having excellent productivity and stability can be configured.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a top view and a cross-sectional view showing an example of a film forming apparatus of the present invention. In FIG. 1A, the evaporation material 31 selected according to the purpose of film formation is held in a container 32 in a molten state. A part of the upper surface of the container 32 is shielded by a shielding plate 37. The evaporating material 31 is in a molten state by heating with the electron beam 41. In this figure, the melt surface is divided into three or more melt surface regions 38 by a shielding plate 37. Further, the evaporating material 31 is connected at a portion other than the melting surface area divided by the shielding plate 37. As a result, the liquid level in the molten surface region 38 can be made uniform.

  By adopting such a configuration, the radiation heat received by the substrate in the electron beam evaporation method can be reduced. The mechanism that can reduce the thermal load with the configuration of the present invention is considered as follows. Radiant heat is proportional to the fourth power of temperature and the area, as represented by the Stefan Boltzmann equation. Moreover, in the structure of this invention, the area of a fusion | melting surface area | region falls with a shielding board. Although the decrease in the melt surface area acts in the direction of reducing radiant heat, it is necessary to increase the evaporation rate per unit area of the melt surface as the melt surface area is reduced, so the temperature of the melt surface area is lower than before the division. Must be hot. However, the evaporation rate of the evaporating material from the melt surface area is very sensitive to the melt surface temperature and the required temperature rise is small. Therefore, according to the configuration of the present invention, it is possible to reduce the excessive radiant heat by compensating for the increase in radiant heat proportional to the fourth power of the temperature.

When high purity is required for the evaporation material or it is difficult to prevent reaction with the crucible material, it is effective to use the water-cooled metal hearth 33 as shown in FIG. Of these, water-cooled copper hearth is often the most suitable in terms of thermal conductivity, workability, and cost. Although it is more preferable to use oxygen-free copper as the copper material, a general copper material may be used according to cost requirements. Further, it is effective to use a crucible 34 as shown in FIG. 1B in order to dissolve and evaporate the evaporation material with a small electron beam power. The material used for the crucible can be alumina, magnesia, zirconia, yttria, boron nitride, carbon, and other high temperature resistant materials, and since it is in contact with the high temperature evaporation material, it is a material related to chemical stability at high temperatures. Is selected according to the evaporation material. Further, the crucible can be held in a crucible case 35 made of metal or the like. It is also effective to use a filler 36 between the crucible case and the crucible in order to stabilize the crucible case 35 and the crucible 34 and stabilize the thermal conductivity. As the filler 36, powder made of a material used for a crucible can be used.

  Since the shielding plate 37 is exposed to a high temperature, it is effective to use water-cooled metal, and it is easy to use water-cooled copper for the same reason as in the case of the water-cooled metal hearth 33 described above. In order to reduce the temperature drop of the evaporation material due to the shielding plate 37 coming into contact with the melt of the evaporation material 31, the shielding plate 37 is made of the high temperature resistant material 39 and the water-cooled metal material 40 as shown in FIG. It is also effective to arrange a high temperature resistant material 39 on the liquid contact portion side and a water-cooled metal material 40 on the opposite side as a double structure. With such a structure, it is possible to reduce the radiant heat from the evaporation source in a state where the molten metal temperature of the evaporation material 31 is less decreased by the shielding plate 37. As the high temperature resistant material 39, the same material as that used for the crucible 34 can be used. Specifically, alumina, magnesia, zirconia, yttria, boron nitride, carbon, and other high temperature resistant materials can be used.

  Various electron beam sources can be used. One or a plurality of small 180-degree deflecting electron guns and 270-degree deflecting electron guns can be used. For wide film formation, a straight-ahead electron gun or a deflection coil 42 of about 90 degrees is combined. Things are suitable because they can operate a wide range of electron beams.

  The aim of the present invention is to reduce the area of the melting surface region 38 divided by the shielding plate, and the area of the melting surface region 38 is desirably 50% or less of the container opening. The division of the molten surface region 38 is set to 3 or more by adjusting the power of the electron beam 41 incident on the divided molten surface region 38, thereby forming the film thickness in the film forming width direction 43 by dividing the molten surface region 37. This is effective because it can prevent the distribution from occurring. Since the radiant heat can be reduced when the shape of the divided molten surface region 38 is small, it is important to improve the aperture of the electron beam. The shape of the divided melt surface region 38 is, for example, a circle, an ellipse, a rectangle, a polygon, a combination thereof, or the like.

  A part of the melting surface is provided with a feed material 44 directed above it. There are various methods for supplying the supply material 44 into the container 32, and the shape of the supply material 44 is appropriately selected depending on the type of evaporation material to be used, and the supply material 44 in the form of wire, granule, pellet, rod, etc. Can be used. In the case of solid supply, these supply materials are supplied to the container 32 and dissolved and mixed with the evaporation material 31 in a dissolved state. In the case of dissolution supply, the supply material 44 moving along the moving direction 46 is dissolved by the electron beam 41 and dropped into the container 32 that holds the evaporated material 31 in a molten state. Since the supply material 44 has a higher temperature in the melt supply than in the solid supply, the melt supply is preferable in order to reduce the change in the evaporation source temperature due to the material supply.

A case where a battery electrode plate is formed using the film forming apparatus of the present invention will be briefly described with reference to FIGS. 3 and 4, the vacuum chamber 2 is evacuated by the vacuum pump 1. The degree of vacuum of the vacuum chamber 2 is appropriately selected within a range of, for example, 0.0005 to 0.2 Pa. In the vacuum chamber 2, an evaporation source 9 and a transport system for the substrate 20 are installed. The width | variety of the board | substrate 20 conveyed is suitably selected in the range of 100-1000 mm, for example. The board | substrate 20 conveyed is selected from copper, nickel, titanium, SUS, and aluminum, for example. The weight thickness of the substrate 20 is appropriately selected within a range of 3 to 50 microns, for example. If necessary, it is possible to use a substrate having a surface provided with irregularities. The substrate transport system includes an unwinding roll 8, a transporting roller 5, a can 6, a winding roll 3, a tension detection mechanism (not shown), and the like. A part of the transport system, for example, a driving motor or the like may be disposed outside the vacuum chamber 2 and a driving force may be introduced into the vacuum chamber 2 via a rotation introduction terminal. The substrate 20 unwound from the unwinding roll 8 is transported along the substrate transport system. A conveyance speed is suitably selected from the range of 0.05-100 m / min, for example. A shielding plate 10 having an opening is provided between the evaporation source 9 and the can 6, and some of the particles flying from the evaporation source 9 adhere to the substrate 20 via the opening and are active material layers. Form. The film formation may be performed with the substrate 20 along the can 6 as shown in FIG. 3, or may be performed in the middle of the transport system as shown in FIG. 4, and other methods are also appropriately selected. The substrate 4 on which the film has been formed is taken up by a take-up roll 3. The film thickness is appropriately selected within a range of, for example, 3 to 30 microns, and the film thickness may be completed during one transport of the substrate, or may be divided by repeated transport. The can 6 is cooled by a refrigerant circulation mechanism. As described above, the evaporation source 9 includes the container 32 that holds the evaporation material 31 and the shielding plate 37 that shields a part of the upper surface of the container, and is divided into three or more by the shielding plate 37. An evaporation mechanism that selectively irradiates the melting surface region 38 with the electron beam 41 is provided. The size of the container 32 is appropriately selected, for example, when the inner dimension in the substrate running direction 45 is, for example, in the range of 50 to 300 mm, and the inner dimension in the film forming width direction is appropriately selected, for example, in the range of 1-3 times the substrate width. The inner dimension in the depth direction is appropriately selected within a range of, for example, 30 to 200 mm. The shielding rate of the upper surface opening of the container 32 by the shielding plate 37 is appropriately selected within a range of 50 to 95%, for example. The acceleration voltage of the electron beam 41 is appropriately selected from the range of −6 to −40 kV, for example. A negative electrode plate of a lithium ion secondary battery can be formed by using copper foil as the substrate 20 and silicon as an evaporation material held in the evaporation source 9. A silicon oxide thin film can be formed by introducing oxygen gas from the gas introduction tube 11 during film formation.

  Silicon-based materials are promising as high-capacity negative electrodes because they have a large amount of lithium occlusion, but large expansion and contraction occurs when lithium is occluded and released, so that a large amount of stress is easily applied to the copper foil as a current collector. When the deformation of the plate occurs, the repeated charge / discharge characteristics deteriorate. However, according to the film forming apparatus and film forming method of the present invention, the deterioration of the mechanical characteristics of the copper foil due to the thermal load during film formation can be reduced. It is effective in realizing.

  In addition to lithium ion secondary batteries, radiant heat can be reduced by the film forming apparatus of the present invention by appropriately changing the substrate material, evaporation material, and other film forming conditions in magnetic recording media, solar cells, capacitors, and the like. It is.

According to the film forming apparatus and the film forming method of the present invention, it is possible to reduce the thermal radiation of the evaporation source, which is typified by wide high-speed electron beam evaporation. As a result, since the thermal load on the substrate can be reduced, it is widely useful as a film forming apparatus and a film forming method by electron beam evaporation.

The conceptual diagram which shows an example of the film-forming apparatus of this invention, (a) The figure in the case of using a water-cooled metal hearth, (b) The figure in the case of using a crucible The conceptual diagram which shows an example of the film-forming apparatus of this invention, (a) The figure in the case of using a water-cooled metal hearth, (b) The figure in the case of using a crucible The conceptual diagram which shows an example of the film-forming apparatus of this invention The conceptual diagram which shows an example of the film-forming apparatus of this invention Conceptual diagram showing an example of a conventional film forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum pump 2 Vacuum tank 3 Winding roll 4 Electron gun 5 Transport roller 6 Can 8 Unwinding roll 9 Evaporation source 10 Shielding plate 11 Gas introduction pipe 20 Substrate 31 Evaporation material 32 Container 33 Water-cooled metal hearth 34 Crucible 35 Crucible case 36 Filling Agent 37 Shield plate 38 Melting surface area 39 High temperature resistant material 40 Water-cooled metal material 41 Electron beam 42 Deflection coil 43 Deposition width direction 44 Supply material 45 Substrate traveling direction 50 Rectification plate

Claims (5)

A melt having a container for holding an evaporating material, a shielding plate for shielding a part of the upper surface of the container, and an evaporating material held in the container, and divided into three or more melting surface regions by the shielding plate A film forming apparatus including an evaporation mechanism that selectively irradiates an area with an electron beam. The film forming apparatus according to claim 1, wherein 50% or more of the opening on the upper surface of the container is shielded by the shielding plate. The film forming apparatus according to claim 1, wherein the evaporating material is supplied to at least one portion of the melting surface region. In a film forming method in which deposition is performed by irradiating an electron beam onto a material held in a container and in a molten state,
The material is divided into three or more melting surface regions by a shielding plate that shields a part of the upper surface of the container,
A film forming method, wherein the material is melted by selectively irradiating the melting surface region with an electron beam. The film-forming method of Claim 4 which manufactures the electrode plate for batteries by using silicon as said material and forming into a film on a copper foil board | substrate.

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