Patent Publication Number: US-2021187543-A1

Title: Film forming apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a film forming apparatus that is used to manufacture an electronic device such as a solar battery and that forms a thin film on a substrate. 
     BACKGROUND ART 
     As a method of forming a film on a substrate, the chemical vapor deposition (CVD) method has been known. However, the chemical vapor deposition method often requires film formation in a vacuum, and thus a large vacuum chamber, as well as a vacuum pump etc., needs to be used. Further, in the chemical vapor deposition method, there has been a problem in that using a substrate having a large area as a substrate to be subjected to film formation is difficult from a point of view of costs or the like. In view of this, a misting method, which enables film forming treatment in atmospheric pressure, has been drawing attention. 
     As a conventional technology related to a film forming apparatus using such a misting method, for example, there is a technology according to Patent Document 1. 
     In the technology according to the Patent Document 1, atomized source solution and reaction material are sprayed from a source solution ejection port and a reaction material ejection port that are provided on a bottom surface of a mist spray head unit including a mist spray nozzle etc. to a substrate disposed in an atmosphere. With such spraying, a film is formed on the substrate. Note that the reaction material refers to a material that contributes to a reaction with the source solution. 
       FIG. 3  is an explanatory diagram illustrating a schematic configuration of a conventional film forming apparatus. As illustrated in  FIG. 7 , on the upper surface of a substrate placing stage  30  being a substrate placing unit, a plurality of substrates  10  are placed. 
     The substrate placing stage  30  includes a suction mechanism  31  that performs vacuum suction. Using the suction mechanism  31 , the substrate placing stage  30  can suck the entire back surface of each of the plurality of placed substrates  10  onto the upper surface of the substrate placing stage  30 . Further, in the substrate placing stage  30 , a heating mechanism  32  is provided below the suction mechanism  31 . Using the heating mechanism  32 , the substrate placing stage  30  can perform heating treatment on the plurality of substrates  10  placed on the upper surface of the substrate placing stage  30 . 
     A thin film forming nozzle  1  (mist spray unit) performs mist spray treatment of spraying source mist MT downwardly from a spray port provided in a spray surface is. Note that the source mist MT is a mist obtained by atomizing a source solution. Using the thin film forming nozzle  1 , the source mist MT can be sprayed in the atmosphere. 
     All of the thin film forming nozzle  1 , the substrate placing stage  30 , and the plurality of substrates  10  placed on the upper surface of the substrate placing stage  30  are accommodated in a film forming chamber  60 . The film forming chamber  60  includes an upper chamber  68 , a lower chamber  69 , and a door  67 . When the film forming chamber  60  performs film forming treatment, the film forming chamber  60  can isolate the thin film forming nozzle  1 , the substrate placing stage  30 , and the plurality of substrates  10  from the outside by closing the door  67  to close an opening portion between the upper chamber  68  and the lower chamber  69 . 
     Thus, by closing the door  67  of the film forming chamber  60  and performing mist spray treatment using the thin film forming nozzle  1  during the heating treatment of the heating mechanism  32 , a thin film can be formed on the substrates  10  placed on the upper surface of the substrate placing stage  30 . 
     In this manner, a conventional film forming apparatus forms a thin film on the substrates  10  by simultaneously performing mist spray treatment using the thin film forming nozzle  1  and heating treatment using the heating mechanism  32 . 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: WO 2017/068625 A1 
       
    
     SUMMARY 
     Problem to be Solved by the Invention 
     As described above, generally, a conventional film forming apparatus has the following configuration. Specifically, the heating mechanism  32  is provided inside the substrate placing stage  30  that allows the substrates  10 , which are base materials as a target of film formation, to be placed on its upper surface, and the substrate placing stage  30  is used as a flat heating means. 
     When a flat heating means such as the substrate placing stage  30  is used, heating treatment for the substrates  10  is performed by bringing the upper surface of the substrate placing stage  30  and the back surface of the substrates  10  to come in contact with each other and causing heat to be transferred between the substrate placing stage  30  and the substrates  10 . 
     However, when the substrate  10  has such a structure that the lower surface of the substrate is curved or the lower surface has recessed portions and projecting portions, instead of having a flat plate-like shape, the flat heating means allows the upper surface of the substrate placing stage  3 C) and the back surface of the substrates  10  to only locally come in contact with each other, Therefore, there have been problems in that heating of the substrates  10  is uneven when heating treatment is performed by the heating mechanism  32 , and the substrates  10  are warped and deformed, for example. 
     The present invention has an object to solve the problems as described above, and provide a film forming apparatus that can form a thin film on a substrate at low costs without reducing film forming quality and a film forming rate. 
     Means to Solve the Problem 
     A film forming apparatus according to the present invention includes: a substrate placing unit allowing a substrate to be placed thereon; a heating mechanism being provided apart from the substrate placing unit, including an infrared lamp, and being configured to perform heating treatment of heating the substrate by radiating infrared light from the infrared lamp; and a mist spray unit being configured to perform mist spray treatment of spraying source mist obtained by atomizing a source solution on front surface of the substrate. A thin film is formed on the front surface of the substrate by simultaneously performing the heating treatment of the heating mechanism and the mist spray treatment of the mist spray unit. 
     Effects of the Invention 
     The film forming apparatus of the invention of the present application according to claim  1  includes the heating mechanism that is provided apart from the substrate placing unit and that performs heating treatment of heating the substrate by radiating infrared light from the infrared lamp. 
     Therefore, in the invention of the present application according to claim  1 , the substrate can be directly heated by the heating mechanism without touching the substrate. Consequently, uniform heating can be performed without deforming the substrate, regardless of the shape of the substrate. 
     As a result, the film forming apparatus of the invention of the present application according to claim  1  can form a thin film on the substrate at low costs without reducing film forming quality and a film forming rate. 
     These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an explanatory diagram illustrating a schematic configuration of a film forming apparatus according to a first embodiment of the present invention. 
         FIG. 2  is an explanatory diagram illustrating a schematic configuration of a film forming apparatus according to a second embodiment of the present invention. 
         FIG. 3  is an explanatory diagram illustrating a schematic configuration of a conventional film forming apparatus. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG. 1  is an explanatory diagram illustrating a schematic configuration of a film forming apparatus according to the first embodiment of the present invention. An XYZ orthogonal coordinate system is illustrated in  FIG. 1 . 
     As illustrated in  FIG. 1 , a film forming apparatus  11  of the first embodiment includes a film forming chamber  6 A, a thin film forming nozzle  1 , an infrared radiation apparatus  2 , and a conveyor  53  as main components. 
     The conveyor  53  being a substrate placing unit allows a plurality of substrates  10  to be placed on an upper surface of a belt  52 . The conveyor  53  includes a pair of rollers  51  for conveyance provided at both right and left (−X direction, +X direction) ends, and an endless belt  52  for conveyance that is stretched across the pair of rollers  51 . 
     With rotational drive of the pair of rollers  51 , the conveyor  53  can move an upper side (+Z direction side) of the belt  52  along a conveying direction (X direction). 
     The pair of rollers  51  of the conveyor  53  is provided outside the film forming chamber  6 A, and the belt  52  has a center portion being provided inside the film forming chamber  6 A, and can be moved between the inside and the outside of the film forming chamber  6 A through a pair of opening portions  63  provided at a portion of right and left (−X direction, +X direction) side surfaces of the film forming chamber  6 A. 
     The thin film forming nozzle  1 , a part of the conveyor  53 , the plurality of substrates  10  placed on the upper surface of the belt  52  of the conveyor  53 , and the infrared radiation apparatus  2  are accommodated in the film forming chamber  6 A. 
     The film forming chamber  6 A includes an upper chamber  61 , a lower chamber  62 , and a pair of opening portions  63 . The pair of opening portions  63  is located between the upper chamber  61  and the lower chamber  62  in a height direction being the Z direction. Therefore, the conveyor  53  provided between the opening portions  63  and  63  in the film forming chamber  6 A is disposed at a position higher than the lower chamber  62  and lower than the upper chamber  61 . 
     The infrared radiation apparatus  2  being a heating mechanism is fixed at a position apart from the conveyor  53  in the lower chamber  62  by a fixing means (not shown). 
     Note that the infrared radiation apparatus  2  is disposed at a position overlapping the upper surface of the belt  52  in the film forming chamber  6 A in plan view. 
     The infrared radiation apparatus  2  includes a lamp placing table  21  and a plurality of infrared lamps  22 . The plurality of infrared lamps  22  are attached to an upper portion of the lamp placing table  21 . Therefore, the infrared radiation apparatus  2  can radiate infrared light upwardly (+Z direction) from the plurality of infrared lamps  22 . With the above-mentioned infrared radiation of the infrared radiation apparatus  2 , heating treatment for the plurality of substrates  10  placed on the upper surface of the belt  52  can be performed. 
     The thin film forming nozzle  1  being a mist spray unit is fixedly disposed in the upper chamber  61  by a fixing means (not shown). In this case, the thin film forming nozzle  1  is disposed to have such a positional relationship that the spray surface  1 S and the upper surface of the belt  52  face each other. 
     The thin film forming nozzle  1  performs mist spray treatment of spraying source mist MT downwardly (−Z direction) from a spray port provided in the spray surface  1 S. Note that the source mist MT is a mist obtained by atomizing a source solution. Using the thin film forming nozzle  1 , the source mist MT can be sprayed in the atmosphere. 
     The film forming chamber  6 A can isolate the thin film forming nozzle  1 , the plurality of substrates  10  placed on the belt  52 , and the infrared radiation apparatus  2  from the outside by closing the opening portions  63  between the upper chamber  61  and the lower chamber  62  with an air curtain  7  when film forming treatment is performed. 
     Therefore, the film forming apparatus  11  of the first embodiment can set a film forming environment by closing the pair of opening portions  63  of the film forming chamber  6 A with the air curtain  7  and moving the belt  52  of the conveyor  53  along the conveying direction (X direction). 
     Then, the film forming apparatus  11  forms a thin film on the substrates  10  placed on the upper surface of the belt  52  in the film forming chamber  6 A by simultaneously performing the heating treatment of infrared radiation of the infrared radiation apparatus  2  and the mist spray treatment of the thin film forming nozzle  1  under the film forming environment. 
     As described above, the film forming apparatus  11  of the first embodiment includes the infrared radiation apparatus  2  that is provided apart from the conveyor  53  being a substrate placing unit, and that performs heating treatment of directly heating the plurality of substrates  10  by radiating infrared light from the infrared lamps  22  as a heating mechanism. 
     Thus, the film forming apparatus  11  of the first embodiment can directly heat the substrates  10  with the infrared radiation apparatus  2  without touching the substrates  10 . Therefore, the film forming apparatus  11  of the first embodiment can perform uniform healing without deforming the substrates  10 , regardless of the shape of the substrates  10 . 
     As a result, the film forming apparatus  11  of the first embodiment can form a thin film on the substrates  10  at low costs without reducing film forming quality and a film forming rate. 
     Further, by providing the infrared radiation apparatus  2  being a heating mechanism inside the film forming chamber  6 A, the film forming apparatus  11  of the first embodiment can radiate infrared light on the substrates  10  without through the film forming chamber  6 A. Accordingly, the film forming apparatus  11  of the first embodiment can enhance efficiency of radiating infrared light. 
     Note that the radiation of infrared light from the infrared radiation apparatus  2  located below (−Z direction) the conveyor  53  is performed upwardly (+Z direction). This means that infrared light is radiated on the plurality of substrates  10  through the belt  52  (upper side and lower side) of the conveyor  53 . 
     In consideration of such configurations, the first countermeasure and the second countermeasure are conceivable: The first countermeasure adopts a structure in which the belt  52  includes a combination of a pair of linear conveyor chains and an opening portion for transmission of infrared light is provided, and the second countermeasure adopts a configuration in which an infrared light transmitting material having excellent transmittance of infrared light that does not absorb infrared light is used as a constituent material of the belt  52 . 
     Thus, regarding the belt  52 , by adopting at least one countermeasure out of the first and second countermeasures, an infrared light absorption degree of the belt  52  can be reduced to a minimum necessary degree. 
     A specific example of the second countermeasure will be described below. Possible examples of the infrared light transmitting material include germanium, silicon, zinc sulfide, and zinc selenide. Note that it is necessary that strength for being used as the belt  52  be satisfied. 
     Further, regarding the wavelength of the infrared light radiated from the infrared radiation apparatus  2 , it is desirable to adopt of a first modification in which the wavelength is set avoiding an absorption wavelength range of the source mist MT. As a specific setting for implementing the first modification, it is conceivable to set the wavelength of the infrared light radiated from the infrared radiation apparatus  2  to fall within a range of 700 to 900 nm. This is because, by adopting the above specific setting, the absorption wavelength range of the source mist MT using a possible solvent can be avoided. 
     It is confirmed as a known fact that, if water or toluene is used as a solvent of a source solution for forming a film, setting of the wavelength of the infrared light radiated from the infrared radiation apparatus  2  to fall within a range of 700 to 900 nm according to the above specific setting allows the wavelength to fall outside the absorption wavelength range of the source mist MT. 
     By adopting the first modification, the film forming apparatus  11  produces an effect of avoiding occurrence of a source mist evaporation phenomenon, in which the source mist MT absorbs infrared light radiated from the infrared radiation apparatus  2  so that the source mist MT is heated and evaporated. 
     Adopting the specific setting of setting the wavelength of the infrared light to range from 700 to 900 nm as the first modification in particular produces an effect of avoiding occurrence of the source mist evaporation phenomenon for the source mist MT made from any possible source material. 
     Second Embodiment 
       FIG. 2  is an explanatory diagram illustrating a schematic configuration of a film forming apparatus according to the second embodiment of the present invention. An XYZ orthogonal coordinate system is illustrated in  FIG. 2 . 
     As illustrated in  FIG. 2 , a film forming apparatus  12  of the second embodiment includes a film forming chamber  6 B, a thin film forming nozzle  1 , an infrared radiation apparatus  2 , and a conveyor  53  as main components. 
     In the following, components common to those of the film forming apparatus  11  of the first embodiment are denoted by the same reference signs to appropriately omit description thereof, and features of the film forming apparatus  12  of the second embodiment will be mainly described. 
     The thin film forming nozzle  1 , a part of the conveyor  53 , and the plurality of substrates  10  placed on the upper surface of the belt  52  of the conveyor  53  are accommodated in the film forming chamber  6 B. The film forming chamber  6 B includes an upper chamber  61 , a lower chamber  629 , and a pair of opening portions  63 , and the pair of opening portions  63  is provided at a portion of right and left side surfaces of the film forming chamber  6 B. Note that the pair of opening portions  63  is located between the upper chamber  61  and the lower chamber  62 B in the height direction being the Z direction. 
     The film forming chamber  6 B has, as its constituent material, an infrared light transmitting material having excellent transmittance that does not absorb infrared light radiated from the infrared radiation apparatus  2 . Specifically, the film forming chamber  6 B has quartz glass as its constituent material. 
     The infrared radiation apparatus  2  being a heating mechanism is fixed below (−Z direction) and outside the lower chamber  62 B at a position apart from the conveyor  53  by a fixing means (not shown). 
     Note that the infrared radiation apparatus  2  is disposed at a position overlapping the upper surface of the belt  52  in the film forming chamber  6 B in plan view. 
     By radiating infrared light upwardly from the plurality of infrared lamps  22 , the infrared radiation apparatus  2  can perform heating treatment for the plurality of substrates  10  placed on the upper surface of the belt  52  through the lower chamber  62 B and the belt  52 . 
     The film forming chamber  6 B can isolate the thin film forming nozzle  1  and the plurality of substrates  10  placed on the belt  52  from the outside by closing the opening portions  63  between the upper chamber  61  and the lower chamber  62 B with the air curtain  7  when film forming treatment is performed. 
     Therefore, the film forming apparatus  12  of the second embodiment can set a film forming environment by closing the pair of opening portions  63  of the film forming chamber  6 B with the air curtain  7  and moving the belt  52  of the conveyor  53  in the conveying direction (X direction). 
     Then, the film forming apparatus  12  forms a thin film on the substrates  10  placed on the upper surface of the belt  52  in the film forming chamber  6 B by simultaneously performing the heating treatment of infrared radiation of the infrared radiation apparatus  2  and the mist spray treatment of the thin film forming nozzle  1  under the film forming environment. 
     As described above, the film forming apparatus  12  of the second embodiment includes the infrared radiation apparatus  2  that is provided apart from the belt  52  being a substrate placing unit, and that performs heating treatment of heating the plurality of substrates  10  by radiating infrared light from the infrared lamps  22  as a heating mechanism. 
     Thus, similarly to the first embodiment, the film forming apparatus  12  of the second embodiment can heat the substrates  10  with the infrared radiation apparatus  2  without touching the substrates  10 . Therefore, the film forming apparatus  12  of the second embodiment can perform uniform heating without deforming the substrates  10 , regardless of the shape of the substrates  10 . 
     As a result, similarly to the first embodiment, the film forming apparatus  12  of the second embodiment can form a thin film on the substrates  10  at low costs without reducing film forming quality and a film forming rate. 
     Further, by providing the infrared radiation apparatus  2  outside the film forming chamber  6 B, the film forming apparatus  12  of the second embodiment can simplify maintenance of the infrared radiation apparatus  2 , such as replacement of the infrared lamps  22 . 
     In addition, the film forming chamber  6 B of the film forming apparatus  12  of the second embodiment has, as its constituent material, quartz glass being an infrared light transmitting material having excellent transmittance for infrared light radiated from the infrared lamps  22 . This configuration produces an effect of reducing an infrared light absorption degree of the bottom surface of the lower chamber  62  at the time of heating the substrates  10  through the bottom surface of the lower chamber  62  of the film forming chamber  6 B to a minimum necessary degree. 
     Note that, when quartz glass being an infrared light transmitting material is used at least as a constituent material of the bottom surface of the lower chamber  62 B of the film forming chamber  6 B, the above effect can be produced. 
     Further, other than quartz glass, the following materials are conceivable as the infrared light transmitting material, for example. Materials such as borosilicate sapphire, calcium fluoride, barium fluoride, magnesium fluoride, and lithium fluoride have high transmittance for near infrared light, and are thus conceivable as an infrared light transmitting material other than quartz glass. Specifically, it is only necessary that the constituent material of the film forming chamber  6 B contain at least one of quartz glass, borosilicate glass, sapphire, calcium fluoride, barium fluoride, magnesium fluoride, and lithium fluoride. 
     Note that, in the film forming apparatus  12  of the second embodiment as well, similarly to the first embodiment, at least one countermeasure out of the first and second countermeasures related to infrared light absorption of the belt  52  may be adopted. 
     Further, in the film forming apparatus  12  of the second embodiment, similarly to the first embodiment, the first modification (including the specific setting described in the first embodiment) may be adopted regarding the wavelength of the infrared light radiated from the infrared radiation apparatus  2 . 
     Note that, in the present invention, each embodiment can be freely combined or each embodiment can be modified or omitted as appropriate within the scope of the invention. 
     While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous unillustrated modifications and variations can be devised without departing from the scope of the invention. 
     EXPLANATION OF REFERENCE SIGNS 
     
         
         
           
               1  Thin film forming nozzle 
               2  Infrared radiation apparatus 
               11 ,  12  Film forming apparatus 
               21  Lamp placing table 
               22  Infrared lamp 
               6 A,  6 B Film forming chamber 
               51  Roller 
               52  Belt 
               53  Conveyor 
               61  Upper chamber 
               62 ,  62 B Lower chamber 
               63  Opening portion