Patent Publication Number: US-2022223404-A1

Title: Cleaning method and processing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based upon and claims priority to Japanese Patent Application No. 2021-002979, filed on Jan. 12, 2021, and the entire contents of this application is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a cleaning method and a processing apparatus. 
     2. Background Art 
     In a processing apparatus that is used in a semiconductor process, when a film is formed on a substrate, a film is also deposited in the apparatus. Therefore, in such a processing apparatus, a cleaning process is performed by which a cleaning gas is supplied into a process container heated to a predetermined temperature to remove a film deposited in the apparatus (see, for example, Patent Document 1). In Patent Document 1, the temperature in a reaction container is detected while a cleaning gas containing fluorine is supplied into the reaction container, and the supply of the cleaning gas is stopped based on the detected temperature. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     [Patent Document 1] Japanese Laid-open Patent Publication No. 2004-172409 
     The present disclosure provides a technique that can reduce damage to a quartz member when removing a silicon-containing film. 
     SUMMARY 
     According to one aspect of the present disclosure, a cleaning method for removing a silicon-containing film deposited in a temperature-adjustable process container by a heater and a cooler includes: stabilizing a temperature in the process container to a cleaning temperature; and removing the silicon-containing film by supplying a cleaning gas into the process container stabilized at the cleaning temperature; wherein in the removing the silicon-containing film, a heating capability of the heater and a cooling capability of the cooler are controlled based on the temperature in the process container. 
     According to the present disclosure, it is possible to reduce damage to a quartz member when removing a silicon-containing film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an example of a processing apparatus according to an embodiment; 
         FIG. 2  is a diagram illustrating an example of a change in the temperature at the time of cleaning; 
         FIG. 3  is a diagram illustrating a temperature dependence of the etching rate of quartz; 
         FIG. 4  is a diagram illustrating a temperature dependence of the etching rate for each of Poly-Si and quartz; 
         FIG. 5  is a flowchart illustrating an example of a cleaning method according to the embodiment; 
         FIG. 6  is a diagram illustrating an example of a cleaning step; 
         FIG. 7  is a diagram illustrating another example of the cleaning step; and 
         FIG. 8  is a diagram illustrating still another example of the cleaning step. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the accompanying drawings, the same or corresponding reference numerals shall be attached to the same or corresponding members or components and overlapping descriptions may be omitted. 
     [Processing Apparatus] 
     Referring to  FIG. 1 , an example of a processing apparatus according to an embodiment will be described.  FIG. 1  is a schematic diagram illustrating an example of a processing apparatus  1  according to an embodiment. 
     The processing apparatus  1  includes a process container  10 , a gas supply section  20 , an exhaust section  30 , a heater  40 , a cooler  50 , a temperature sensor  60 , a controller  90 , and the like. 
     The process container  10  has a generally cylindrical shape. The process container  10  includes an inner pipe  11 , an outer pipe  12 , a manifold  13 , an injector  14 , a gas outlet  15 , a lid  16 , and the like. 
     The inner pipe  11  has a generally cylindrical shape. The inner pipe  11  is formed of a heat-resistant material such as quartz. The inner pipe  11  is also referred to as an inner tube. 
     The outer pipe  12  has a generally cylindrical shape with a ceiling and is concentrically provided around the inner pipe  11 . That is, the inner pipe  11  and the outer pipe  12  form a double pipe structure. The outer pipe  12  is formed of a heat-resistant material such as quartz. The outer pipe  12  is also referred to as an outer pipe. 
     The manifold  13  has a generally cylindrical shape. The manifold  13  supports the lower ends of the inner pipe  11  and the outer pipe  12 . The manifold  13  may be formed, for example, of stainless steel. 
     The injector  14  penetrates the manifold  13  to extend horizontally in the inner pipe  11 , and bends in the inner pipe  11  to extend upward in an L-shaped manner. The injector  14  has a base end connected to a gas supply pipe  22 , which will be described later below, and a tip that is opened. The injector  14  discharges a process gas, introduced through the gas supply pipe  22 , from the opening at the tip into the inner pipe  11 . Examples of the process gas may include a deposition gas, a cleaning gas, and a purge gas. In the present embodiment, the deposition gas is a gas used to deposit a silicon-containing film. Examples of the deposition gas may include a silicon-containing gas, a nitride gas, an oxide  2 ′ gas, and a doping gas. Examples of the silicon-containing film may include a silicon film, a silicon nitride film, and a silicon oxide film. Examples of the silicon film may include an amorphous silicon (a-Si) film, a polysilicon (Poly-Si) film, and a doped silicon (Doped-Si) film. The cleaning gas is a gas used to perform a cleaning method, which will be described later below. Examples of the cleaning gas may include halogen-containing gases such as F 2  gas, Cl 2  gas, ClF 3  gas, NF 3  gas, and HF gas. The purge gas is a gas for replacing the atmosphere in the process container  10  with an inert gas atmosphere. Examples of the purge gas may include an inert gas such as N 2  gas and Ar gas. In the example of  FIG. 1 , a single injector  14  is illustrated, but a plurality of injectors  14  may be used. 
     The gas outlet  15  is formed in the manifold  13 . The gas outlet  15  is connected to an exhaust pipe  32 , which will be described later. The process gas supplied into the process container  10  is evacuated by the exhaust section  30  through the gas outlet  15 . 
     The lid  16  airtightly seals the opening at the lower end of the manifold  13 . The lid  16  is formed, for example, of stainless steel. A wafer boat  18  is mounted on the lid  16  via a heat insulation cylinder  17 . The heat insulation cylinder  17  and the wafer boat  18  may be formed of a heat resistant material such as quartz, for example. The wafer boat  18  holds a plurality of wafers W generally horizontally with predetermined intervals in the vertical direction. The wafer boat  18  is carried (loaded) into the process container  10  by a lifting and lowering mechanism  19  lifting the lid  16  and is accommodated in the process container  10 . The wafer boat  18  is carried out (unloaded) from the process container  10  by the  2 ′ lifting and lowering mechanism  19  lowering the lid  16 . 
     The gas supply section  20  includes a gas source  21 , a gas supply pipe  22 , and a flow rate controller  23 . The gas source  21  is the source of the process gas and includes, for example, a deposition gas source, a cleaning gas source, and a purge gas source. The gas supply pipe  22  connects the gas source  21  to the injector  14 . The flow controller  23  is disposed on to control the flow rate of the gas that flows through the gas supply pipe  22 . The flow rate controller  23  includes, for example, a mass flow controller and an opening/closing valve. The gas supply section  20  controls the flow rate of the process gas from the gas source  21  by the flow rate controller  23  and supplies the process gas to the injector  14  via the gas supply pipe  22 . 
     The exhaust section  30  includes an exhaust device  31 , an exhaust pipe  32 , and a pressure controller  33 . For example, the exhaust device  31  is a vacuum pump such as a dry pump or a turbomolecular pump. The exhaust pipe  32  connects the gas outlet  15  to the exhaust device  31 . The pressure controller  33  is disposed on the exhaust pipe  32  to control the pressure within the process container  10  by adjusting the conductance of the exhaust pipe  32 . The pressure controller  33  may be, for example, an automatic pressure control valve. 
     The heater  40  includes a heat insulating material  41 , a heating element  42 , and a jacket  43 . The heat insulating material  41  has a generally cylindrical shape and is provided around the outer pipe  12 . The heat insulating material  41  is formed mainly of silica and alumina. The heating element  42  is linear and provided in a spiral or serpentine shape around the inner periphery of the heat insulating material  41 . The heating element  2 ′  42  is configured to enable temperature control in a plurality of zones divided in the height direction of the process container  10 . Hereinafter, the plurality of zones are referred to as “TOP”, “C-T”, “CTR”, “C-B”, and “BTM” in order from the top. The jacket  43  is provided to cover the outer periphery of the heat insulating material  41 . The jacket  43  retains the shape of the heat insulating material  41  and reinforces the heat insulating material  41 . The jacket  43  is formed of a metal such as stainless steel. A water-cooled jacket (not illustrated) may be provided around the outer periphery of the jacket  43  in order to suppress the thermal effect on the outside of the heater  40 . The heater  40  heats the interior of the process container  10  by heat generation of the heating element  42 . 
     The cooler  50  supplies a cooling fluid to the process container  10  and cools the wafers W in the process container  10 . The cooling fluid may be, for example, air. For example, after a heat treatment, the cooler  50  supplies the cooling fluid to the process container  10  when rapidly cooling the wafers W. Also, the cooler  50  supplies the cooling fluid into the process container  10 , for example, at the time of cleaning for removing a deposit film in the process container  10 . The cooler  50  includes fluid flow paths  51 , blowout holes  52 , a distribution flow path  53 , flow rate adjusters  54 , and a heat exhaust port  55 . 
     The plurality of fluid flow paths  51  are formed in the height direction between the heat insulating material  41  and the jacket  43 . The fluid flow paths  51  may be, for example, flow paths formed along the circumferential direction on the outside of the heat insulating material  41 . 
     The blowout holes  52  are formed penetrating the heat insulating material  41  from the respective fluid flow paths  51  and blow the cooling fluid into the space between the outer pipe  12  and the heat insulating material  41 . 
     The distribution flow path  53  is provided outside the jacket  43 , and distributes and supplies the cooling fluid to each fluid flow path  51 . 
     The flow rate adjusters  54  are disposed on the distribution flow path  53  to adjust the flow rate of the cooling fluid supplied to the fluid flow paths  51 . 
     The heat exhaust port  55  is provided above a plurality of blowout holes  52  to discharge the cooling fluid supplied to the space between the outer pipe  12  and the heat insulating material  41  to the outside of the processing apparatus  1 . The cooling fluid discharged to the outside of the processing apparatus  1  is cooled, for example, by a heat exchanger, and supplied again to the distribution flow path  53 . However, the cooling fluid discharged to the outside of the processing apparatus  1  may be discharged without being reused. 
     The temperature sensor  60  detects the temperature in the process container  10 . The temperature sensor  60  is provided, for example, in the inner pipe  11 . However, the temperature sensor  60  may be provided at a position where the temperature within the process container  10  can be detected. For example, the temperature sensor  60  may be provided in a space between the inner pipe  11  and the outer pipe  12 . The temperature sensor  60  includes a plurality of temperature gauges  61  to  65  disposed at different positions in the height direction corresponding to a plurality of zones, for example. The temperature gauges  61  to  65  are provided corresponding to the respective zones “TOP”, “C-T”, “CTR”, “C-B”, and “BTM”. The plurality of temperature gauges  61  to  65  may be, for example, thermocouples or temperature measuring resistors. The temperature sensor  60  transmits the temperature detected by the plurality of the temperature gauges  61  to  65  to the controller  90 . 
     The controller  90  controls the operation of the processing apparatus  1 . The controller  90  may be, for example, a computer. A computer program for performing the overall operation of the processing apparatus  1  is stored in a storage medium. The storage medium may be, for example, a flexible disk, a compact disk, a hard disk, a flash memory, a DVD, or the like. 
     Here, a cleaning gas is used when removing a silicon-containing film deposited in the process container  10  in the processing apparatus  1 . The removal reaction of the silicon-containing film by the cleaning gas may generate reaction heat and increase the temperature in the process container  10 . As the temperature in the process container  10  increases, the removal reaction of the silicon-containing film becomes easy to proceed, and reaction heat is further generated to increase the temperature in the process container  10 . Thus, the removal reaction of the silicon-containing film may proceed in a state of a desired temperature or more, causing damage (etching) to a member, such as quartz, used in the process container  10 . As a result, particles are generated due to a member such as quartz, or the life of the member such as quartz is shortened and replacement frequency is increased. Also, when the cleaning temperature is set to be low considering the reaction heat, the etching rate of the silicon-containing film is lowered, and the productivity deteriorates. 
       FIG. 2  is a diagram illustrating an example of a change in the temperature in the process container  10  (hereinafter referred to as the “in-furnace temperature”) at the time of cleaning.  FIG. 2  illustrates the change in the in-furnace temperature when the wafer boat  18  is carried into the process container  10  in which a silicon-film is deposited, F 2  gas is supplied into the process container  10  after the in-furnace temperature is stabilized, and the inside of the process container  10  is cleaned. In  FIG. 2 , the horizontal axis indicates time and the vertical axis indicates the in-furnace temperature [° C.]. In  FIG. 2 , the solid line, the broken line, and the dash-dotted line respectively indicate the in-furnace temperature at the top (TOP), the center (CTR), and the bottom (BTM) of the wafer boat  18 . 
     As illustrated in  FIG. 2 , when the F 2  gas is supplied into the process container  10  after the temperature in the process container  10  is stabilized, it can be seen that the temperature in the process container  10  is increased in each of TOP, CTR and BTM. For example, for TOP, the in-furnace temperature increases from about 310° C. before the start of cleaning to about 400° C. Also, for CTR, the in-furnace temperature increases from about 325° C. before the start of cleaning to about 425° C. For BTM, the in-furnace temperature increases from about 360° C. before the start of cleaning to about 450° C. 
       FIG. 3  is a diagram illustrating a temperature dependence of the etching rate of quartz.  FIG. 3  illustrates the etching rate (E/R) of quartz when F 2  gas is supplied into the process container  10  having the in-furnace temperature set to 350° C., 400° C., and 450° C. In  FIG. 3 , the horizontal axis indicates the in-furnace temperature [° C.] and the vertical axis indicates E/R [nm/min]. As illustrated in  FIG. 3 , E/R is about 3 nm/min  2 ′ when the in-furnace temperature is 350° C., while E/R is about 20 nm/min when the in-furnace temperature is 400° C. When the in-furnace temperature is 450° C., E/R is about 90 nm/min. 
       FIG. 4  is a diagram illustrating a temperature dependence of the etching rate for each of Poly-Si and quartz.  FIG. 4  illustrates the etching rate (E/R) for each of Poly-Si and quartz when F 2  gas is supplied into the process container  10  having the in-furnace temperature set to 200° C., 300° C., and 400° C. In  FIG. 4 , the horizontal axis indicates the in-furnace temperature [° C.] and the vertical axis indicates E/R [nm/min]. As illustrated in  FIG. 4 , it can be seen that the lower the in-furnace temperature, the higher the selection ratio of Poly-Si to quartz. 
     As described above, from the results of  FIG. 3  and  FIG. 4 , it can be seen that Poly-Si can be selectively removed with little etching of quartz when the in-furnace temperature is about 200° C. to about 350° C. On the other hand, it can be seen that when the in-furnace temperature is 400° C. or higher, the selection ratio of Poly-Si to quartz decreases and quartz is damaged. 
     Hereinafter, an example of a cleaning method according to an embodiment that can reduce damage to a quartz member when removing a silicon-containing film in the process container  10  will be described. 
     Cleaning Method 
     Referring to  FIG. 5 , an example of a cleaning method of an embodiment will be described. Hereinafter, a case for removing a silicon-containing film deposited in the process container  10  by repeating a process of depositing the silicon-containing film on a wafer W in the above-described processing apparatus  1  will be described as an example. 
     The cleaning method of the embodiment includes a carry-in step S 10 , a temperature stabilization step S 20 , a cleaning step S 30 , a purge step S 40 , and a carry-out step S 50 . 
     The carry-in step S 10  is a step of carrying the wafer boat  18  into the process container  10 . In the carry-in step S 10 , the controller  90  controls the lifting and lowering mechanism  19  to lift the lid  16  to carry the lid  16  and the wafer boat  18  on the lid  16  into the process container  10 . At this time, the temperature in the process container  10  is raised to the cleaning temperature by the heater  40 . The cleaning temperature may be, for example, 300° C. to 350° C. 
     The temperature stabilization step S 20  is performed after the carry-in step S 10 . In the temperature stabilization step S 20 , the controller  90  controls the heater  40  and the cooler  50  to stabilizes the temperature in the process container  10  to the cleaning temperature. In the temperature stabilization step S 20 , the controller  90  controls the gas supply section  20  to supply the purge gas into the process container  10  through the injector  14  and controls the exhaust section  30  to adjust the pressure in the process container  10  to the cleaning pressure. 
     The cleaning step S 30  is performed after the temperature stabilization step S 20 . In the cleaning step S 30 , the controller  90  controls the gas supply section  20  to supply F 2  gas, which is an example of the cleaning gas, into the process container  10  stabilized at the cleaning temperature to remove the silicon-containing film. 
       FIG. 6  is a diagram illustrating an example of the cleaning step S 30 . The cleaning step S 30  illustrated in  FIG. 6  is a step for removing the silicon-containing film deposited in the process container  10  by repeating a cycle including a F 2  supply step S 31  and a cooling step S 32 . 
     In the present embodiment, the controller  90  first executes the F 2  supply step S 31 , and when the temperature in the process container  10  becomes equal to or greater than the first temperature T 1  in the F 2  supply step S 31 , the controller  90  transitions from the F 2  supply step S 3  to the cooling step S 32 . Also, when the temperature in the process container  10  is less than or equal to the second temperature T 2  in the cooling step S 32 , the controller  90  transitions from the cooling step S 32  to the F 2  supply step S 31 . 
     The F 2  supply step S 31  is a step of supplying the F 2  gas into the process container  10  without operating the cooler  50 . In the F 2  supply step S 31 , the F 2  gas reacts with the silicon-containing film to generate reaction heat and raise the temperature in the process container  10 . 
     The cooling step S 32  is a step of operating the cooler  50  without supplying the F 2  gas into the process container  10  to increase the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . In the cooling step S 32 , the temperature rise in the process container  10  due to reactive heat is suppressed because the F 2  gas is not supplied into the process container  10 . Further, in the cooling step S 32 , the interior of the process container  10  is cooled because the cooler  50  is operated to increase the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . In the cooling step S 32 , from the viewpoint of increasing the cooling efficiency, it is preferable to supply N 2  gas, which is an example of a purge gas, into the process container  10  to increase the pressure in the process container  10 . 
     The first temperature T 1  is set to, for example, 350° C. to 400° C. Thereby, it is possible to prevent a member such as quartz used in the process container  10  from being etched by the F 2  gas and damaged. The second temperature T 2  is a temperature lower than the first temperature T 1  and is set to, for example, 300° C. to 350° C. 
     According to the cleaning step S 30  illustrated in  FIG. 6 , the silicon-containing film deposited in the process container  10  is removed by supplying the F 2  gas into the process container  10  until the temperature in the process container  10  rises to the first temperature T 1 . Subsequently, when the temperature in the process container  10  becomes greater than or equal to the first temperature T 1 , the supply of the F 2  gas into the process container  10  is stopped, the N 2  gas is supplied into the process container  10 , and the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40  is increased. This cools the interior of the process container  10 . As a result, the silicon-containing film in the process container  10  can be removed while preventing damage to members such as quartz used in the process container  10 . 
     It should be noted that although three times of F 2  supply steps S 31  and two times of cooling steps S 32  are alternately performed in the above described example in  FIG. 6 , the number of times by which F 2  supply steps S 31  and cooling steps S 32  are performed is not limited thereto. 
       FIG. 7  is a diagram illustrating another example of the cleaning step S 30 . In the cleaning step S 30  illustrated in  FIG. 7 , the first temperature T 1  used for determining the transition from the F 2  supply step S 31  to the cooling step S 32  is changed during the cycle. It should be noted that the other configurations may be the same as those of the cleaning step S 30  illustrated in  FIG. 6 . 
     In the present embodiment, a first temperature T 1   b  at the time of the second transition from the F 2  supply step S 31  to the cooling step S 32  is changed to a temperature lower than a first temperature T 1   a  at the time of the first transition from the F 2  supply step S 31  to the cooling step S 32 . 
     It should be noted that although the first temperature T 1  used for determining the transition from the F 2  supply step S 31  to the cooling step S 32  is changed to a lower temperature as the number of cycles is increased in the example of  FIG. 6 , the first temperature T 1  may be changed to a higher temperature as the number of cycles is increased, for example. 
     According to the cleaning step S 30  illustrated in  FIG. 7 , the silicon-containing film deposited in the process container  10  is removed by supplying the F 2  gas into the process container  10  until the temperature in the process container  10  rises to the first temperature T 1   a , T 1   b . Subsequently, when the temperature in the process container  10  becomes greater than or equal to the first temperature T 1   a , T 1   b , the supply of the F 2  gas into the process container  10  is stopped, the N 2  gas is supplied into the process container  10 , and the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40  is increased. This cools the interior of the process container  10 . As a result, the silicon-containing film in the process container  10  can be removed while preventing damage to members such as quartz used in the process container  10 . 
     It should be noted that although three times of F 2  supply steps S 31  and two times of cooling steps S 32  are alternately performed in the above described example in  FIG. 7 , the number of times by which F 2  supply steps S 31  and cooling steps S 32  are performed is not limited thereto. 
       FIG. 8  is a diagram illustrating another example of the cleaning step S 30 . The cleaning step S 30  illustrated in  FIG. 8  is a step for removing the silicon-containing film deposited in the process container  10  by operating the cooler  50  while supplying F 2  gas into the process container  10 . 
     In the present embodiment, the controller  90  first controls the gas supply section  20  to supply the F 2  gas into the process container  10  via an injector  14  to remove the silicon-containing film deposited in the process container  10 . At this time, when the F 2  gas reacts with the silicon-containing film, reaction heat is generated and the temperature in the process container  10  is raised. Subsequently, when the temperature in the process container  10  becomes equal to or greater than the first temperature T 1   a , the controller  90  cools the interior of the process container  10  by increasing the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . Subsequently, when the temperature in the process container  10  becomes less than or equal to the second temperature T 2 , the controller  90  decreases the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . Subsequently, when the temperature in the process container  10  becomes equal to or greater than the first temperature T 1   b , the controller  90  cools the interior of the process container  10  by increasing the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . Subsequently, when the temperature in the process container  10  becomes less than or equal to the second temperature T 2 , the controller  90  decreases the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . Thereafter, similarly, the silicon-containing film deposited in the process container  10  is removed while adjusting the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . 
     According to the cleaning step S 30  illustrated in  FIG. 8 , the silicon-containing film deposited in the process container  10  is removed by supplying the F 2  gas into the process container  10  until the temperature in the process container  10  rises to the first temperature T 1   a , T 1   b . Subsequently, when the temperature in the process container  10  becomes greater than or equal to the first temperature T 1   a , T 1   b , the controller  90  increases the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40  to cool the interior of the process container  10 . Subsequently, when the temperature in the process container  10  becomes less than or equal to the second temperature T 2 , the controller  90  decreases the ratio of the cooling capacity of the cooler  50  to the heating capacity of the heater  40 . Thereby, the silicon-containing film in the process container  10  can be removed while preventing damage to members such as quartz used in the process container  10 . 
     The purge step S 40  is performed after the cleaning step S 30 . The purge step S 40  is a step of replacing the gas in process container  10 . In the purge step S 40 , N 2  gas is supplied from the injector  14  into the process container  10  and the F 2  gas remaining in the process container  10  is replaced with the N 2  gas. 
     The carry-out step S 50  is performed after the purge step S 40 . The carry-out step S 50  is a step of carrying out the wafer boat  18  from within the process container  10 . In the carry-out step S 50 , while operating the cooler  50  to rapidly cool the interior of the process container  10 , by lowering the lid  16  by the lifting and lowering mechanism  19 , the lid  16  and the wafer boat  18  are carried out from the interior of the process container  10 . 
     The embodiment disclosed herein should be considered to be exemplary in all respects and not restrictive. The above embodiment may be omitted, substituted, or modified in various forms without departing from the appended claims and spirit thereof.