Patent Publication Number: US-11639548-B2

Title: Film-forming material mixed-gas forming device and film forming device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/890,041, filed on Aug. 21, 2019, in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a film-forming material mixed-gas forming device and a film forming device. 
     Related Art 
     The film-forming technique of forming a desired material layer on a base substrate is widely used when manufacturing semiconductor devices or the like. For example, a film-forming material, which is in liquid phase at room temperature and atmospheric pressure and contains atoms forming at least part of the material laminated on a semiconductor substrate, may be used. Examples of such a film-forming material in liquid form include triethoxysilane (TEOS) used to form a SiO 2  insulating film. If the film-forming material in liquid form is used, a device is required which vaporizes the film-forming material to thereby supply the vaporized film-forming material and a carrier gas to a reaction chamber. 
     For example, U.S. Pat. No. 6,210,485 discloses a device that quantitatively supplies a film-forming material in liquid form (liquid precursor substance) and a carrier gas, vaporizes the supplied film-forming material, mixes the vaporized film-forming material with the carrier gas, and supplies a mixed gas of the vaporized film-forming material and the carrier gas to a reaction chamber. 
     SUMMARY OF THE INVENTION 
     In a case of forming a thick film, a large amount of a film-forming material is desirably supplied to improve production efficiency. However, in a case of using a film-forming material in liquid form at room temperature and atmospheric pressure, such a large amount of the film-forming material may possibly lead to insufficient vaporization of the film-forming material. If the film-forming material is insufficiently vaporized, droplets of the film-forming material are carried over to the reaction chamber and are attached to a surface of the substrate. This may possibly cause degradation in the quality of a formed film. Therefore, it is desirable to use a film-forming material mixed-gas forming device and a film forming device which are capable of reliably vaporizing the film-forming material. 
     According to an aspect of the present disclosure, there is provided a film-forming material mixed-gas forming device including: a film-forming material supply unit that supplies a film-forming material in liquid form at a predetermined flow rate; a carrier gas supply unit that supplies a carrier gas at a predetermined flow rate; a main vaporization unit that vaporizes the film-forming material by heating the film-forming material supplied from the film-forming material supply unit and the carrier gas supplied from the carrier gas supply unit; and an auxiliary vaporization unit having a porous vaporization member which captures carried over droplets of the film-forming material in gas flowing out from the main vaporization unit and vaporizes the captured droplets of the film-forming material. 
     In the film-forming material mixed-gas forming device according to the aspect of the present disclosure, the porous vaporization member may be formed of a sintered metallic body. 
     In the film-forming material mixed-gas forming device according to the aspect of the present disclosure, the sintered metallic body may be formed of a fibrous sintered metallic body. 
     The film-forming material mixed-gas forming device according to the aspect of the present disclosure may further include an auxiliary heater that heats the auxiliary vaporization unit. 
     In the film-forming material mixed-gas forming device according to the aspect of the present disclosure, the auxiliary vaporization unit may be provided adjacent to the main vaporization unit. 
     The film-forming material mixed-gas forming device according to the aspect of the present disclosure may further include a second material gas supply unit that supplies a second material gas to a location downstream of the auxiliary vaporization unit at a predetermined flow rate. 
     According to another aspect of the present disclosure, there is provided a film forming device including: the film-forming material mixed-gas forming device according to one aspect; and a reaction chamber to which the film-forming material and the carrier gas are supplied from the film-forming material mixed-gas forming device. 
     The film-forming material mixed-gas forming device and the film forming device according to one aspect of the present disclosure are capable of reliably vaporizing the film-forming material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram illustrating a configuration of a film forming device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinbelow, an embodiment of the present disclosure will be described with reference to the drawing.  FIG.  1    is a schematic diagram illustrating a configuration of a film forming device  100 . 
     The film forming device  100  includes a film-forming material mixed-gas forming device  1  according to the embodiment of the present disclosure, a film-forming material supply  2 , a carrier gas supply  3 , a second material gas supply  4 , and a reaction chamber  5 . The film-forming material supply  2  supplies a film-forming material R 1  to the film-forming material mixed-gas forming device  1 . The carrier gas supply  3  supplies a carrier gas C to the film-forming material mixed-gas forming device  1 . The second material gas supply  4  supplies a second material gas R 2  to the film-forming material mixed-gas forming device  1 . A film-forming material mixed gas Gm, which is a mixed gas of the vaporized film-forming material R 1 , the carrier gas C, and the second material gas R 2 , is supplied from the film-forming material mixed-gas forming device  1  to the reaction chamber  5 . 
     The film-forming material mixed-gas forming device  1  includes a film-forming material supply unit  11 , a carrier gas supply unit  12 , a main vaporization unit  13 , an auxiliary vaporization unit  14 , an auxiliary heater  15 , an outflow valve  16 , and a second material gas supply unit  17 . The film-forming material supply unit  11  supplies the film-forming material R 1  in liquid form at a predetermined flow rate. The carrier gas supply unit  12  supplies the carrier gas C at a predetermined flow rate. The main vaporization unit  13  vaporizes the film-forming material R 1  by heating the film-forming material R 1  supplied from the film-forming material supply unit  11  and the carrier gas C supplied from the carrier gas supply unit  12 , and forms a preliminary mixed gas Gp which is a mixed gas of the vaporized film-forming material R 1  and the carrier gas C. The auxiliary vaporization unit  14  captures carried over droplets of the film-forming material R 1  in the preliminary mixed gas Gp flowing out from the main vaporization unit, and vaporizes the captured droplets of the film-forming material R 1 . The auxiliary heater  15  heats the auxiliary vaporization unit  14 . The outflow valve  16  is capable of stopping an outflow of the preliminary mixed gas Gp. The second material gas supply unit  17  is provided downstream of the auxiliary vaporization unit  14 , and supplies the second material gas R 2  at a predetermined flow rate. 
     The film-forming material supply unit  11  regulates the flow rate of the film-forming material R 1 , which is supplied from the film-forming material supply  2 , at the predetermined flow rate in advance. The film-forming material supply unit  11  may be configured to have a flow rate sensor and a flow rate regulating valve. The film-forming material R 1  is selected depending on the material of a film to be formed, and, for example, triethoxysilane (TEOS) is used as the film-forming material R 1 . 
     The carrier gas supply unit  12  regulates the flow rate of the carrier gas C, which is supplied from the carrier gas supply  3 , at the predetermined flow rate in advance. The carrier gas supply unit  12  can be configured to have a flow rate sensor and a flow rate regulating valve. Inert gas such as helium, argon or nitrogen is used as the carrier gas C. 
     The main vaporization unit  13  vaporizes the film-forming material R 1  by heating the film-forming material R 1  and the carrier gas C which have been supplied. For this reason, the main vaporization unit  13  can be configured to have a heat source, for example, an electric heater. In addition, the main vaporization unit  13  preferably has a heat transfer structure capable of transferring sufficient heat to the film-forming material R 1  supplied from the film-forming material supply unit  11 , and to the carrier gas C supplied from the carrier gas supply unit  12 . The heated temperature of the main vaporization unit  13  is preferably greater than or equal to the boiling point of the film-forming material R 1 , more preferably a temperature greater by 5° C. to 20° C. than the boiling point of the film-forming material R 1 . 
     In addition, the main vaporization unit  13  may be configured to generate a gas flow, for example, a swirl gas in flows of the carrier gas C, which is capable of facilitating the vaporization of the film-forming material R 1  by shearing and breaking up the film-forming material R 1  in liquid form. 
     The auxiliary vaporization unit  14  has a porous vaporization member  141  formed of a porous body having pores which prevents droplets of the film-forming material R 1  from passing therethrough. The porous vaporization member  141  prevents droplets of the film-forming material R 1  from being introduced into the reaction chamber  5  by capturing the droplets of the film-forming material R 1  contained in the preliminary mixed gas Gp flowing out from the main vaporization unit  13 . In addition, since the droplets of the film-forming material R 1  captured by the porous vaporization member  141  penetrate into the porous vaporization member  141 , the area of contact between the porous vaporization member  141  and the preliminary mixed gas Gp passing therethrough becomes large, the residence time in the member  141  become longer and thus the vaporization of the preliminary mixed gas Gp becomes facilitated. 
     Since the preliminary mixed gas Gp flowing out from the main vaporization unit  13  has been heated in the main vaporization unit  13 , it is considered that the preliminary mixed gas Gp has thermal energy enough to vaporize the droplets of the film-forming material R 1  contained therein. For this reason, when the droplets of the film-forming material R 1  stay inside the auxiliary vaporization unit  14 , the film-forming material R 1  in liquid phase can be vaporized by the heat contained in both of the film-forming material R 1  in gaseous phase and the carrier gas. 
     In more detail, when the saturated vapor pressure of the liquid of the film-forming material R 1  captured by the auxiliary vaporization unit  14  is greater than the partial vapor pressure of the film-forming material R 1  in the preliminary mixed gas Gp passing through the auxiliary vaporization unit  14 , the liquid of the film-forming material R 1  captured by the auxiliary vaporization unit  14  can be vaporized. If the amount of film-forming material R 1  vaporizing in the auxiliary vaporization unit  14  is greater than the amount of the liquid of the film-forming material R 1  newly flowing out from the main vaporization unit  13 , it is possible to attain an equilibrium state where the film-forming material mixed gas Gm containing a predetermined amount of film-forming material R 1  is formed while preventing the auxiliary vaporization unit  14  from being blocked. 
     A sintered metallic body is preferably used as the porous body forming the porous vaporization member  141  of the auxiliary vaporization unit  14 . If the porous vaporization member  141  is formed of the sintered metallic body, since it is possible to increase the thermal conductivity of the porous vaporization member  141 , the captured droplets of the film-forming material R 1  can be rapidly vaporized owing to heat being transferred thereto. A chemically stable metal such as stainless steel is preferably used as metal forming the porous vaporization member  141 . 
     In addition, a fibrous sintered metallic body is preferably used as the sintered metallic body forming the porous vaporization member  141 . It is possible to increase the porosity of the fibrous sintered metallic body while reducing the pore diameters of the fibrous sintered metallic body. This makes it possible to reduce passing resistance of the preliminary mixed gas Gp while reliably preventing the droplets of the film-forming material R 1  from passing through the porous vaporization member  141 , thereby rapidly vaporizing the captured film-forming material R 1 . It is desirable that the filtration accuracy of the porous vaporization member  141  be, for example, less than or equal to 0.5 μm. Furthermore, it is possible to improve a vaporization capability (the vaporized amount of film-forming material R 1  per unit time) of the porous vaporization member  141  by increasing the volume of the porous vaporization member  141 . As described above, since the vaporization capability of the porous vaporization member  141  depends on various conditions, it is possible to determine specifications of the porous vaporization member  141  by experiments or an actual operation. 
     The auxiliary vaporization unit  14  can be configured to have a flange  142  for fixing the porous vaporization member  141  in a flow path. The porous vaporization member  141  can be formed into the shape of a tube having one sealed end and the other end that is connected to the flange  142 . If the porous vaporization member  141  and the flanges  142  are formed of metal, it is possible to rapidly vaporize the captured droplets of the film-forming material R 1  by conducting heat of the auxiliary heater  15  to the porous vaporization member  141 . In addition, if the auxiliary vaporization unit  14  is configured such that the flange  142  is provided at one end of the porous vaporization member  141  having a tubular shape, the auxiliary vaporization unit  14  can be configured such that the porous vaporization member  141  is disposed in the interior of an inlet flow path or the like of the outflow valve  16 . Therefore, since the auxiliary vaporization unit  14  does not require a dedicated housing, it is possible to reduce the size of the film-forming material mixed-gas forming device  1 . 
     It is preferable that the auxiliary vaporization unit  14  is provided adjacent to the main vaporization unit  13 . In the present embodiment, branches or other devices are not provided in a passage between the main vaporization unit  13  and the auxiliary vaporization unit  14 . This makes it possible for the auxiliary vaporization unit  14  to facilitate the vaporization of the droplets of the film-forming material R 1 , which are captured by the porous vaporization member  141 , by making efficient use of thermal energy of the preliminary mixed gas Gp flowing out from the main vaporization unit  13 . 
     The auxiliary heater  15  is provided so as to directly heat the auxiliary vaporization unit  14 , or to indirectly heat the auxiliary vaporization unit  14  by heating a configuration element in the vicinity of the auxiliary vaporization unit  14 . As described above, the preliminary mixed gas Gp flowing out from the main vaporization unit  13  to the auxiliary vaporization unit  14  has sufficient heat. For this reason, the heating temperature of the auxiliary heater  15  only has to be set such that the auxiliary heater  15  is capable of preventing a decrease in the temperature of the auxiliary vaporization unit  14 , which is caused by heat radiation to the ambient atmosphere. Therefore, the heating temperature may be less than the boiling point of the film-forming material. Specifically, the heating temperature of the auxiliary heater  15  can be set less than by approximately 20° C. to 40° C. than the boiling point of the film-forming material. 
     In accordance with an operation mode of the reaction chamber  5 , the outflow valve  16  selects whether the preliminary mixed gas Gp is supplied or the supply of the preliminary mixed gas Gp is stopped. In addition, the outflow valve  16  can be used to stabilize the vaporization of the film-forming material R 1  by applying a proper back pressure to the main vaporization unit  13 . 
     The second material gas supply unit  17  further adds the second material gas R 2  to the preliminary mixed gas Gp flowing out from the outflow valve  16 . This allows the film-forming material mixed gas Gm, which is a mixed gas of the preliminary mixed gas Gp and the second material gas R 2 , to be formed. The film-forming material mixed-gas forming device  1  of the present embodiment supplies the film-forming material mixed gas Gm, which is formed in this manner, to the reaction chamber  5 . 
     The second material gas supply unit  17  can be configured to have a flow rate sensor and a flow rate regulating valve. The second material gas supply unit  17  mixes the preliminary mixed gas Gp with the second material gas R 2 , after the complete vaporization of the film-forming material R 1  by the auxiliary vaporization unit  14 . The temperature of the second material gas R 2  may be lower than that of the preliminary mixed gas Gp. This makes it possible for the film-forming material mixed-gas forming device  1  to vaporize the film-forming material R 1  in liquid form by making efficient use of heat of the main vaporization unit  13 . It should be noted that the temperature of the second material gas R 2  is set so as to prevent the vapor of the film-forming material from being condensed during mixing. For example, oxygen, argon, helium, or nitrogen gas is used as the second material gas R 2 . 
     The film-forming material supply  2  is configured so as to be capable of supplying the film-forming material R 1  in liquid form at a pressure where the film-forming material R 1  can be introduced into the film-forming material mixed-gas forming device  1  against the internal pressure thereof. As a specific example, the film-forming material supply  2  can be configured to include a sealed container  21  that stores the film-forming material R 1  in liquid phase, and a pressurizing mechanism  22  that introduces pressurizing gas for pressurizing the film-forming material R 1  into a head space inside the sealed container  21 . 
     The sealed container  21  can be configured such that a pipe is connected to a lower portion of the sealed container  21 , from which the film-forming material R 1  is allowed to flow out. The pressurizing mechanism  22  can be configured to have a pressurizing gas cylinder  221  that stores the pressurizing gas, and a pressurizing gas regulating valve  222  that regulates the pressure of the pressurizing gas supplied from the pressurizing gas cylinder  221  to the sealed container  21 . It is preferable that inert gas such as helium gas is used as the pressurizing gas. 
     The carrier gas supply  3  can be configured to have a carrier gas cylinder  31  that stores the carrier gas C, and a carrier gas regulating valve  32  that regulates the pressure of the carrier gas C supplied from the carrier gas cylinder  31  to the film-forming material mixed-gas forming device  1 . 
     The second material gas supply  4  can be configured to have a second material gas cylinder  41  that stores the second material gas R 2 , and a second material gas regulating valve  42  that regulates the pressure of the second material gas R 2  supplied from the second material gas cylinder  41  to the film-forming material mixed-gas forming device  1 . 
     The reaction chamber  5  is configured such that the base substrate, on which a film is formed using the film-forming material mixed gas, is accommodated in the reaction chamber  5  and the internal space of the reaction chamber  5  can be vacuumed. The reaction chamber  5  is capable of having a well-known configuration having an auxiliary device for forming a film, for example, a plasma generator. 
     As described above, the film-forming material mixed-gas forming device  1  and the film forming device  100  including the film-forming material mixed-gas forming device  1  include the auxiliary vaporization unit  14 , thereby capturing and vaporizing droplets of the film-forming material R 1  contained in the gas flowing out from the main vaporization unit  13 . This makes it possible to improve film-forming quality by preventing the droplets of the film-forming material R 1  from being introduced into the reaction chamber  5 . 
     The embodiment of the present disclosure has been described above; however, the present disclosure is not limited to the foregoing embodiment. In addition, the effects in the above-described embodiment have been described merely as an example of the most suitable effects of the present disclosure, and the effects of the present disclosure are not limited to those in the above-described embodiment. 
     For example, in the film-forming material mixed-gas forming device according to the present disclosure, the auxiliary heater  15 , the outflow valve  16 , and the second material gas supply unit  17  are optional configuration elements, which may be omitted. In addition, in the film-forming material mixed-gas forming device  1  according to the present disclosure, the auxiliary vaporization unit  14  may be provided downstream of a merging point between the outflow valve  16  and the second material gas supply unit  17 . 
     EXAMPLES 
     Using the film forming device having the configuration of  FIG.  1   , all gases were supplied to the reaction chamber in which a wafer was loaded. Thereafter, the number of particles attached to a surface of the wafer inside the reaction chamber was measured in each range. For comparison, the same test was conducted using a film forming device having the same configuration except that the porous vaporization member of the auxiliary vaporization unit was removed. It should be noted that the porous vaporization member of the auxiliary vaporization unit, which was formed of a fibrous sintered stainless steel body and was formed into the shape of a tube having one sealed end, was used. 
     Triethoxysilane was used as the film-forming material, and the supply amount of the film-forming material was 16.5 g/min. Argon gas was used as the carrier gas, and the supply amount of carrier gas was 10 slm. Oxygen gas was used as the second material gas, and the supply amount of second material gas was 40 slm. After the resultant mixed gas was supplied to the reaction chamber for 300 seconds, the number of particles attached to the surface of the wafer was counted. The following Table 1 shows the results of counting the number of particles. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Number of particles [Piece] 
                 Number of particles [Piece] 
               
               
                 Particle size 
                 (Auxiliary vaporization unit 
                 (Auxiliary vaporization unit 
               
               
                 [μm] 
                 is not provided) 
                 is provided) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 0.026-0.045 
                 12533 
                 35 
               
               
                 0.045-0.06  
                 1200 
                 5 
               
               
                 0.06-0.10 
                 20 
                 3 
               
               
                 0.10-0.20 
                 1 
                 0 
               
               
                 0.2-0.5 
                 0 
                 0 
               
               
                 0.5-1.0 
                 0 
                 0 
               
               
                 1.0&lt; 
                 1 
                 2 
               
               
                 Total 
                 13755 
                 45 
               
               
                   
               
            
           
         
       
     
     As described above, it has been confirmed that it was possible to prevent the film-forming material in liquid phase from being carried over into the reaction chamber by vaporizing the film-forming material using the film-forming material mixed-gas forming device having the auxiliary vaporization unit. In addition, in maintenance after a long period of operation, it has been confirmed that no liquid was stored in the porous vaporization member, that is, all of the film-forming material in liquid form could be vaporized. 
     EXPLANATION OF REFERENCE NUMERALS 
     
         
         
           
               1  FILM-FORMING MATERIAL MIXED-GAS FORMING DEVICE 
               2  FILM-FORMING MATERIAL SUPPLY 
               3  CARRIER GAS SUPPLY 
               4  SECOND MATERIAL GAS SUPPLY 
               5  REACTION CHAMBER 
               11  FILM-FORMING MATERIAL SUPPLY UNIT 
               12  CARRIER GAS SUPPLY UNIT 
               13  MAIN VAPORIZATION UNIT 
               14  AUXILIARY VAPORIZATION UNIT 
               15  AUXILIARY HEATER 
               16  OUTFLOW VALVE 
               17  SECOND MATERIAL GAS SUPPLY UNIT 
               100  FILM FORMING DEVICE 
               141  POROUS VAPORIZATION MEMBER