Patent Application
20240279790
This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2023-024929, filed Feb. 21, 2023, and Japanese Patent Application No. 2023-096544, filed Jun. 12, 2023, which are incorporated by reference.
The present invention relates to an evaporation source for use in a vacuum evaporation apparatus, the evaporation source being for depositing an evaporation material on a to-be-deposited article by evaporating the evaporation material in a vacuum chamber.
Among these kinds of evaporation sources for use in a vacuum evaporation apparatus, there is known, e.g., in patent document 1 an example in which an evaporation boat is employed. The evaporation source in question comprises: a boat main body having a containing part for containing therein an evaporation material; rising plate parts each rising upward from respective ends as seen in one direction of the boat main body; and electrode mounting plate parts each extending from an upper end of the respective rising plate parts outward. In order to attain reduced costs, etc., ordinarily, each part such as the boat main body, the rising plate part, and the electrode mounting plate part is formed by a plate material made of metal. Then, the evaporation boat is placed in position inside the vacuum chamber by respectively holding (pinching) it by a pair of the upper and the lower electrode plates. At the time of depositing the evaporation material on an article to be processed (elsewhere also called “a to-be-processed article”) inside the vacuum chamber, the evaporation boat main body is heated by Joule heat by applying power by electric source through electrode plates to both the electrode mounting plate parts. For example, by constantly or intermittently feeding a wire-shaped evaporation material, e.g., from an upper side of the boat main body to the containing part of the boat main body, thereby melting and evaporating the evaporation material inside the containing part. As a result of splashing of this evaporated evaporation material, it is deposited on the to-be-processed article. At this time, the evaporated material is fluidized in the containing part and this fluidized material is prevented by the rising plate parts from crawling up (rising) to the electrode mounting plate parts.
By the way, if the above-mentioned evaporation boat is heated in a state in which there is no evaporation material inside the containing part, the boat main body, the rising plate parts and the electrode mounting plate parts are subjected to heating to an equivalent temperature. However, it has been found that, when the wire-shaped evaporation material is fed to the containing part of the heated boat main body, there are cases where the rising plate parts get overheated to a high temperature. Should the state in which the rising plate parts get overheated be continued in this manner, there will result in deformation of each part of the evaporation boat. On occasions, there will occur disadvantages in that the plate thickness is reduced (thinner-plate thickness), resulting in the occurrence of holes. There is thus a problem in that the evaporation boat will become shorter in its lifetime. This is considered to be attributable to the following causes. Namely, when the wire-shaped evaporation material is fed to, and melted in, the containing part of the boat main body, depending on the kind of the evaporation materials, the electric resistance value of the boat main body will be reduced (in other words, the energized current will be divided into the molten evaporation material), so that the electric resistance value at the rising plate parts becomes relatively high.
This invention has been made in view of the above-mentioned points and has a problem of providing an evaporation source for use in a vacuum evaporation apparatus, in which the evaporation source prevents excessive local overheating in order to attain a longer lifetime.
In order to solve the above-mentioned problem, an evaporation source for use in a vacuum evaporation apparatus according to this invention is to deposit an evaporation material on a to-be-deposited article by evaporating the evaporation material in a vacuum chamber. The evaporation source comprises an evaporation boat including: a boat main body having a containing part for the evaporation material; rising plate parts each rising upward from respective ends as seen in one direction of the boat main body; and electrode mounting plate parts each extending from an upper end of the respective rising plate parts outward. The boat main body is heated by applying electric power across both the electrode mounting plate parts, thereby causing the evaporation material inside the containing part to be evaporated. In the above-mentioned arrangement, the rising plate parts are provided with dividing passages for the applied electric current.
According to this invention, when the evaporation material is melted in the containing part of the boat main body under heated conditions, even if the electric resistance value of the boat main body has been decreased, the electric resistance value of the rising plate parts can be prevented, by the dividing passages, from relatively getting higher. As a result, the overheating of the rising plate parts can be prevented to the best extent possible, thereby prolonging the lifetime of the evaporation boat. In this case, it is preferable to set the dividing passages such that the electric resistance value at the rising plate parts becomes equivalent to the electric resistance value at the boat main body during evaporation. According to this arrangement, the boat main body and the rising plate parts can be made equivalent in temperature during evaporation. As a consequence, even if the evaporation material that has been melted inside the containing part may try to crawl up to the rising plate parts, this crawled-up evaporation material may also be evaporated quickly. In this manner, the evaporation material can be prevented from getting deposited at the rising plate part and, in addition, the fluctuation in the deposition rate can also be prevented. It is to be noted that, once the rising plate parts are overheated, bumping may take place at the time of contact of the molten evaporation material's crawling up into contact with the rising plate parts. However, since the overheating of the rising plate parts is prevented from taking place, the occurrence of bumping can also be prevented to the best extent possible.
In this invention the dividing passages can be constituted by a pair of reinforcing plates which are arranged to pinch the electrode mounting plate parts and the rising plate parts from both sides thereof as seen in the plate thickness direction of both the plate parts. As a result, without impairing the function of preventing the relative increase in the electric resistance value of the rising plate parts, the electrode mounting plate parts and the rising plate parts can be reinforced, thereby advantageously further preventing the deformation of the evaporation boat. In this case, the reinforcing plates shall preferably be constituted by a high-melting point metallic material selected from the group consisting of molybdenum, tungsten, and tantalum.
Further, in this invention, in case the evaporation source comprises a pair of upper and lower electrode plates for pinching therebetween the electrode mounting plate parts, there may be employed an arrangement in which screen parts are disposed each on the reinforcing plate that is positioned on the upper side so as to cover an end face, lying on the side of the boat main body, of the electrode plate. According to this arrangement, even if the molten evaporation material may crawl up to the electrode mounting plate parts through the rising plate parts for some reasons or other, the molten evaporation material can be blocked by the screen parts, thereby surely preventing the molten evaporation material from directly reaching the electrode plates.
With reference to the drawings, description will be made of an embodiment of an evaporation source BS for use in a vacuum evaporation apparatus of this invention based on an example in which a copper film is evaporated on a deposition surface of a substrate Sg in a vacuum chamber while feeding an evaporation material Em to thereby evaporate it, on condition: that an article (hereinafter called “a substrate Sg”) to receive thereon evaporated particles is a square glass substrate; that an evaporation material Em is made of copper formed into a wire shape; and that, while feeding the evaporation material Em and allow it to be evaporated, a copper film is vapor-deposited on a film-forming surface of the substrate Sg inside a vacuum chamber. In the following descriptions the terms showing the direction such as up (or upper), down (or lower) shall be based on
With reference to
With reference also to
On the inner surface of the lower wall 1a of the vacuum chamber, there are installed two supporting platforms 4, 4 which are constituted by an insulating material at a distance from each other as seen in the longitudinal direction. On an upper surface of the supporting platforms 4, 4 there are installed a pair of upper and lower electrode plates 5a, 5b made of a metal of good conductivity such as copper in such a manner that each of the electrode mounting plate parts 33 of the evaporation boat 3 is detachably mounted by pinching them in a vertical direction by means of a fastening means 41 such as bolts and the like. In this case, such parts of the electrode plates 5a, 5b as will pinch the electrode mounting plate parts 33 have a far wider width than does the electrode plates 5a, 5b so that the electrode mounting plate parts 33 can be kept in close contact with each other over the entire surface thereof. The electrode mounting plate parts 33 can thus be fastened by the fastening means 41 on both sides of the electrode mounting plate parts 33. In a state of having mounted the electrode plates 5a, 5b while pinching the electrode mounting plate parts 33, the evaporation boat 3 is installed at a predetermined height position from the inner surface of the lower wall 1a of the vacuum chamber in a posture in which the bottom plate of the boat main body 31, defining the recessed part 31a, becomes horizontal.
Inside the vacuum chamber 1 there is provided a material feeding means 6 for continuously or intermittently feeding the wire-shaped evaporation material Em into the recessed part 31a of the boat main body 31. The material feeding means 6 is provided with: a feed roller 61 which is installed on a side opposite to the evaporation source BS relative to a deposition preventing plate 11 disposed inside the vacuum chamber 1; an electric motor 62 for driving, by rotation, the feed roller 61; and a pair of upper and lower guide rollers 63, 63. The deposition preventing plate 11 has formed therein a through hole 11a which is positioned above the evaporation boat 3 and which is for inserting therethrough the evaporation material Em. On such a side of the deposition preventing plate 11 as lies on the side of the evaporation source BS, there is installed a guide pipe 64 of a predetermined length bent into an articulated manner. As the evaporation material Em there is used one formed into an outside diameter of 1 mm through 5 mm, which is wound around the feed roller 61 in advance. Then, the front end of the wire-shaped evaporation material Em that is wound around the feed roller 61 is pulled out so as to pass it through the pair of upper and lower guide rollers 63, 63, thereby allowing it to pass from the through hole 11a to the inside of the guide pipe 64. The front end of the evaporation material Em to be protruded out of the guide pipe 64 is arranged to come into contact with the inner bottom surface in the longitudinally central region of the recessed part 31a. The wire-shaped evaporation material Em is prepared in this manner.
In case a copper film is deposited on a lower surface of the substrate Sg inside the vacuum chamber 1 under vacuum atmosphere, the boat main body 31 is heated by Joule heat by applying electric current from a power source (not illustrated) across both the electrode mounting plate parts 33, 33 through the electrode plates 5a, 5b. After a lapse of a predetermined time, the feed roller 61 is driven for rotation by the electric motor 62 so as to feed the wire-shaped evaporation material Em. According to these operations, the evaporation material Em that is present inside the recessed part 31a is melted and evaporated. As a result of splashing of the evaporated material, a copper film is deposited on the lower surface of the substrate Sg that is moving in one direction. At this time, the melted evaporation material Em will be fluidized in the recessed part 31a, and this fluidized evaporation material is prevented by the rising plate parts 32 from crawling up toward the electrode mounting plate parts 33, 33. The current value to be applied across both the electrode mounting plate parts 33, 33 and the feeding speed of the wire-shaped evaporation material Em are appropriately set depending on the rate of deposition on the substrate Sg.
When the wire-shaped evaporation material Em is fed to the recessed part 31a of the heated boat main body 31, there will be a case in which the rising plate parts 32 will sometimes be heated to an elevated temperature. This is considered to be due to the fact that the electric resistance value of the boat main body 31 is reduced (in other words, the applied electric current is divided into the molten evaporation material Em), and that the electric resistance value of the rising plate parts 32 becomes relatively high. If the state in which the rising plate parts 32 are overheated continues, each part of the evaporation boat 3 will result in thermal deformation and, in some cases, the plate thickness is reduced (thin-walling), thereby resulting in a disadvantage of making (springing) holes. As a result, the evaporation boat 3 ends in an early lifetime.
In this embodiment, in order for the rising plate parts 32 and the electrode mounting plate parts 33 to coincide with each other in outline, the following arrangements have been made. Namely, there are prepared two pieces of reinforcing plates 7a, 7b, each being formed by fabricating a single plate material having a constant plate thickness into an L-shape. When they are attached to the electrode plates 5a, 5b, the electrode mounting plate parts 33 and the rising plate parts 32 are arranged to be pinched by a pair of the reinforcing plates 7a, 7b from both sides as seen in the plate thickness direction (vertical direction). As the reinforcing plates 7a, 7b, there may be used one made of a metal of high-melting point. Further, as shown in
According to the above-mentioned arrangement, when the wire-shaped evaporation material Em is fed into, and melted in, the recessed part 31a of the boat main body 31 under heated conditions, even if the electric resistance value of the boat main body 31 may be decreased, the pair of reinforcing plates 7a, 7b serve the purpose of dividing passages for the applied electric current. The electric resistance value of the rising plate parts 32 can thus be prevented from relatively rising, so that the overheating of the rising plate parts 32 can be prevented to the best extent possible. Further, since the electrode mounting plate parts 33 and the rising plate parts 32 are reinforced by a pair of reinforcing plates 7a, 7b, the evaporation boat 3 can still further be prevented from deformation. As a result, the evaporation boat 3 can be prevented from getting locally overheated or deformed, thereby attempting to extend the lifetime of the evaporation boat 3. In this case, in order for the electric resistance value at the rising plate parts 32 to be equivalent to the electric resistance value of the boat main body 31 during deposition, the sectional area of each of the reinforcing plates 7a, 7b shall preferably be set accordingly. According to this arrangement, during deposition, the boat main body 31 and the rising plate parts 32 can be made equivalent to each other in temperature. As a result, even if the molten evaporation material Em, melted inside the recessed part 31a during evaporation, were to crawl up to the rising plate parts 32, the crawled up evaporation material Em will also be quickly evaporated. Consequently, the evaporation material Em can be prevented from getting accumulated at the rising plate parts 32 and, in addition, the change in the deposition rate can also be prevented. By the way, once the rising plate parts 32 get overheated, bumping may occur when the molten evaporation material Em crawls up into contact with the rising plate parts 32. But since the overheating of the rising plate parts 32 is prevented, the occurrence of the bumping can also be prevented.
By the way, as noted above, when the wire-shaped evaporation material Em is fed to the recessed part 31a of the heated boat main body 31, depending on the heating temperature of the boat main body 31 and the feeding speed of the evaporation material Em, depending on the evaporation rate, the following will occur. Namely, as shown in
In this embodiment, supporting means 8 is disposed in a manner to contact the bottom plate part 31b from the lower side thereof. The supporting means 8 is provided with a first base plate 82 which is installed horizontally by interposing first insulators 81a on the inside of the lower wall 1a of the vacuum chamber, the supporting means being positioned on the inner side of both the supporting stands 4, 4. The first base plate 82 has vertically installed two supporting columns 83, 83 which extend upward. Then, at a predetermined height position from the inner wall of the vacuum chamber 1a, there is provided a second base plate 84, by being supported by each of the supporting columns 83. The second base plate 84 is provided with supporting plates 85 whose upper ends come into contact with the lower surface of the boat main body 31 by interposing second insulators 81b. The supporting plates 85 have a larger width (in the vertical direction as seen in
By being supported by each of the supporting columns 83, a reflector plate 86 having an area equivalent to the bottom surface of the evaporation boat 3 is disposed. The reflector plate 86 is constituted by a high-melting point metallic plate material having a plate thickness in a range of 0.1 mm through 2 mm. In this case, such a surface of the reflector plate 86 as lies opposite to the boat main body 31 may be subjected to mirror finish. Further, the reflector plate 86 has formed therein a slit 86a so as to enable the supporting plates 85, 85 to be inserted therethrough. In this embodiment, the supporting columns 83, 83 are provided on their external surfaces with screw threads 83a so that a plurality of nut members 83b are in threaded engagement with the screw threads 83a. In this case, the second base plate 84 and the reflector plate 86 have formed through holes (not illustrated) which penetrate in the plate thickness direction. The supporting columns 83, 83 are inserted into the through holes for positioning thereof by means of the nut members 83b which form a pair in the vertical direction. It is thus so arranged that the height position of the second base plate 84 and reflector plate 86 relative to the boat main body 31 can be appropriately fine-adjusted.
According to the above-mentioned arrangement, by providing the bottom plate part 31b of the boat main body 31 with supporting means 8 so as to come into contact from the lower side, with which load to be caused by the feeding of the evaporating material Em operates, the creep deformation can be prevented to the best extent possible. At this time, by constituting the supporting means 8 as defined above, the area of contact with the bottom plate part 31b can be made small to the best extent possible. In addition, even if the region on which the load is operated on the bottom plate part 31b by the vibrations, etc. at the time of feeding the wire-shaped evaporation material Em, may vary to some degrees, the free ends 85a, 85b of the supporting plates 85 can be managed to be positioned, and thus the bottom plate part 31b on which the load operates can be constantly supported. In addition, since the two pieces of flexed (or bent) supporting plates 85, 85 are arranged in parallel with each other, the other free end of each of the supporting plates 85, 85 will support the longitudinal both ends (parts other than the bottom plate part 31b). Therefore, the deformation of the entire boat main body 31 can be reduced and, during evaporation work, the boat main body 31 can be held substantially horizontal all the time.
Further, since the reflector plate 86 is further provided, in case bumping should occur inside the recessed part 31a of the boat main body 31 due to some causes or other during evaporation, there can be surely prevented such an occurrence as an electric insulation breakdown as a result of adhesion of the evaporation material Em in the liquid state or solid state that is caused to occur by the bumping inside the recessed part 31a of the boat main body 31. Still furthermore, as a result of reflection of radiation heat from the boat main body 31, in case some parts or others such as piping or wiring are disposed in the lower space of the boat main body 31, such parts can advantageously be protected from the heat. As a result, together with the fact of having provided the reinforcing plates 7a, 7b which serve as the dividing passages, the prolonged lifetime of the evaporation boat 3 can be attained.
In order to confirm the above effects, by using the vacuum evaporation apparatus Es as shown in
Descriptions have so far been made of the embodiments of this invention but, as long as the technical concept of this invention is not deviated, various modifications are possible. In the above-mentioned embodiments, descriptions have been made based on examples of constituting dividing passages by a pair of reinforcing plates 7a, 7b. Provided, however, that dividing passages can be arranged to prevent the relative increase in the electric resistance value of the rising plate parts 32 during evaporation, there is no need of limiting to the above-mentioned examples. Instead, electrical conductive parts such as cables or bus bars may be used in connecting in parallel the boat main body 31 with the electrode mounting plate parts 33, thereby forming the dividing passages for the rising plate parts. Further, in the above-mentioned embodiments, descriptions were made based on examples in which the reinforcing plates 7a, 7b are partly inclined relative to the rising plate parts 32 so that the rising plate parts 32 are pinched by a pair of reinforcing plates 7a, 7b. But instead of limiting to them, the following arrangement may be employed. For example, after having installed a pair of reinforcing plates 7a, 7b on each side of the rising plate parts 32 and the electrode mounting plate parts 33 as seen in the thickness direction thereof, the reinforcing plates 7a, 7b are fastened by means of high-melting point metallic bolts and the like, or else, are integrated by spot welding so that the rising plate parts 32 may be integrated for pinching together.
Further, in the above-mentioned embodiments, regarding the supporting means 8 a description was made of an example in which two pieces of supporting plates 85, 85 bent into the shape of a “E” are arranged in parallel with each other. However, it need not be limited to the above as long as the bottom plate part 31b, on which is operated the load to be brought by the feeding of the evaporating material Em, can be supported by contact, from the lower side, with the bottom plate part 31b. For example, a beam member which is circular in cross section or in an ellipse may be disposed in a manner to bridge the bottom plate part 31b so as to support the bottom plate part 31b. Or else, a plurality of columnar bodies may be vertically installed on the supporting plates 85 so as to support the bottom plate part 31b. By the way, in case the supporting means 8 is provided, this invention may also be applicable to a shape having no rising plate parts 32 as the evaporation port 3. Further, in the above-mentioned embodiments, descriptions were made of examples in which the free ends 85a, 85b of the supporting plates 85 are installed in parallel in a posture to coincide orthogonally with the longitudinal direction of the boat main body 31. However, this invention is not to be limited thereto but, depending on the direction of vibrations of the wire-shaped evaporation material Em when the evaporation material Em is fed, each of the supporting plates 85, 85 may be installed in a posture in which the width direction of each of the supporting plates 85, 85 coincides with the longitudinal direction of the boat main body 31.
Further, in the above-mentioned embodiments, descriptions were made of examples in which a single piece of plate material was formed into L-shape as the reinforcing plates 7a, 7b. However, this invention shall not be limited thereto. In a modified example, as shown in
In addition, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-024929 | Feb 2023 | JP | national |
| 2023-096544 | Jun 2023 | JP | national |
