Patent Publication Number: US-2019181015-A1

Title: Substrate Processing Method and Substrate Processing Apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Japanese Patent Application No. 2016-078421, filed on Apr. 8, 2016, in the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a substrate processing method and a substrate processing apparatus. More particularly, the present disclosure further relates to a substrate processing method and a substrate processing apparatus for removing an oxide film. 
     BACKGROUND 
     In a manufacturing method of an electronic device by using a silicon wafer (hereinafter, referred to as a “wafer”), for example, a film forming process for forming a conductive film or an insulating film on the surface of the wafer, a lithography process for forming a photoresist layer in a predetermined pattern on the formed conductive film or insulating film, an etching process for shaping the conductive film into a gate electrode or for forming a wiring groove or a contact hole in the insulating film by means of plasma generated from a process gas by using the photoresist layer as a mask, and the like are repeatedly performed. 
     As an example, in a certain manufacturing method of an electronic device, after forming a groove in a predetermined pattern in the polysilicon film that is formed on the surface of the wafer, a silicon oxide film is formed as an oxide film to fill the groove. Then, the silicon oxide film is removed to be a predetermined thickness by etching or the like. 
     At this time, as a method for removing the silicon oxide film, there has been known a substrate processing method, which performs a COR (Chemical Oxide Removal) process and a PHT (Post Heat Treatment) process with respect to the wafer. The COR process is a process of chemically reacting the silicon oxide film with gas molecules to thereby produce a reaction product. The PHT process is a process of heating the wafer with the COR process performed to sublimate the reaction product that has been produced on the wafer through the chemical reaction of the COR process, for removal from the wafer. 
     As a substrate processing apparatus for performing the substrate processing method including the COR process and the PHT process, there has been known a substrate process apparatus having a chemical reaction chamber (COR processing chamber) and a heat treatment chamber (PHT processing chamber) connected to the chemical reaction chamber. In addition, another substrate processing apparatus configured to perform the COR process with respect to the wafer at a low temperature, and then perform the PHT process by heating the wafer to a predetermined temperature in the same processing chamber. 
     However, since the sublimated product stagnates in the vicinity of the wafer in the PHT process, a case of hindering the sublimation of the new reaction product from the wafer may occur. As a result, time is required to perform the PHT process, so that it is difficult to improve the throughput of the oxide film removal. 
     SUMMARY 
     The present disclosure provides a substrate processing method and a substrate processing apparatus capable of improving the throughput of the oxide film removal. 
     According to one embodiment of the present disclosure, there is provided a substrate processing method for removing an oxide film formed on the surface of a substrate. The method includes modifying the oxide film into a reaction product by supplying a halogen element-containing gas and an alkaline gas onto the substrate accommodated in the interior of a processing chamber, and sublimating the reaction product by stopping the supply of the halogen element-containing gas into the processing chamber for removal from the substrate. An internal pressure of the processing chamber in the sublimating is set to be higher than an internal pressure of the processing chamber in the modifying by supplying an inert gas into the processing chamber. 
     According to another embodiment of the present disclosure, there is provided a substrate processing apparatus including a processing chamber configured to accommodate a substrate, and a gas supply unit configured to selectively supply a halogen element-containing gas, an alkaline gas, or an inert gas into the processing chamber. The gas supply unit is configured to perform modifying an oxide film formed on the substrate accommodated in the processing chamber into a reaction product by supplying the halogen element-containing gas and the alkaline gas into the processing chamber and sublimating the reaction product for removal from the substrate by stopping the supply of the halogen element-containing gas into the processing chamber. The gas supply unit is configured to supply an inert gas into the processing chamber to set an internal pressure of the processing chamber in the sublimating to be higher than an internal pressure of the processing chamber in the modifying. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in, and constitute a part of, the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure. 
         FIG. 1  is a plan view schematically showing the configuration of a substrate processing system that adopts a substrate processing apparatus, according to an embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view schematically showing the configuration of an etching device in  FIG. 1 . 
         FIGS. 3A to 3J  are process diagrams showing an oxide film removal process as a substrate processing method according to an embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view for explaining stagnation of sublimation of the reaction product from a wafer. 
         FIGS. 5A and 5B  are process diagrams for explaining a method for removing a sublimation gas in a PHT process of the oxide film removal process in  FIG. 3 . 
         FIG. 6  is a graph showing an etching amount in the oxide film removal process of  FIG. 3  when varying a supply amount of an inert gas in a PHT process. 
         FIGS. 7A and 7B  are cross-sectional views schematically showing configuration of a modified example of the etching device in  FIG. 2 , wherein  FIG. 7A  shows a first modified example and  FIG. 7B  shows a second modified example. 
         FIGS. 8A to 8D  are timing charts showing a supply start or supply stop of various gases in the COR operation and the PHT operation of the oxide film removal process in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. 
       FIG. 1  is a plan view schematically showing the configuration of a substrate processing system that adopts a substrate processing apparatus, according to an embodiment of the present disclosure. In  FIG. 1 , some elements are illustrated as if they are transparent in order to facilitate the understanding of the present disclosure. 
     In  FIG. 1 , the substrate processing system  10  includes a loading/unloading part  11  configured to load/unload a semiconductor wafer (hereinafter, simply referred to as a “wafer”), which is an substrate to be processed substrate, two load lock chambers  12  installed adjacent to the loading/unloading part  11 , heat treatment devices  13  installed adjacent to the load lock chambers  12 , respectively, and configured to perform heat treatment with respect to the wafer W, etching devices  14  installed adjacent to the heat treatment devices  13 , respectively, to perform an oxide film removal process including a COR process and a PHT process with respect to the wafer W, and a control unit  15 . 
     The loading/unloading part  11  has a loader module chamber  17  in which a wafer transfer mechanism  16  for transferring the wafer W is installed. The wafer transfer mechanism  16  has two transfer arms  16   a  and  16   b  for holding the wafer W in a substantially horizontal position. A load port  18  is installed in the side portion of the loader module chamber  17  in the longitudinal direction thereof, and, for example, three carriers C capable of receiving a plurality of wafers may be loaded and connected in the load port  18 . In addition, an orienter  19 , which rotates the wafer to optically measure an eccentric amount of the wafer W, and perform position alignment, is installed adjacent to the loader module chamber  17 . 
     In the loading/unloading unit  11 , the wafer W is held by the transfer arms  16   a  and  16   b  and is straightly moved on a substantially horizontal plane and elevated by the wafer transfer mechanism  16  to be transferred to a desired position. In addition, the transfer arms  16   a  and  16   b  move forward or backward with respect to the carrier C on the load port  18 , the orienter  19 , and the load lock chamber  12 , respectively, to load/unload the wafer W therebetween. 
     Each load lock chamber  12  is connected to the loader module chamber  17  with a gate valve  20  interposed therebetween. A wafer transfer mechanism  21  for transferring the wafer W is installed in each load lock chamber  12 . Further, the load lock chamber  12  is configured to be vacuumized to a predetermined vacuum degree. 
     The wafer transfer mechanism  21  is provided with an articulated arm structure that has a peak for holding the wafer W in a substantially horizontal position. The peak is positioned inside the load lock chamber  12  during a state of retracting the articulated arm structure, the peak reaches the heat treatment device  13  by expanding the articulated arm structure, and the peak reaches the etching device  14  by further expanding the articulated arm structure. According to this, the wafer transfer mechanism  21  transfers the wafer W between the load lock chamber  12 , the heat treatment device  13 , and the etching device  14 . 
     The heat treatment device  13  has a chamber  22  that can be vacuumized A mounting table (not shown) for mounting the wafer W thereon is installed in the chamber  22 , and a heater (not shown) is embedded in the mounting table. In the heat treatment device  13 , the wafer W on which the COR process and PHT process have been repeatedly performed in the etching device  14  is mounted on the mounting table and heated by the heater so that residue, existing on the wafer W after the oxide film removal process, are evaporated to be removed. 
     A loading/unloading port (not shown) is formed on the side of the chamber  22  facing the load lock chamber  12  for transferring the wafer W to or from the load lock chamber  12 , and the loading/unloading port is opened or closed by a gate valve  23 . In addition, another loading/unloading port (not shown) is formed on the side of the chamber  22  facing the etching device  14  for transferring the wafer W to or from the etching device  14 , and the loading/unloading port is opened or closed by a gate valve  24 . 
     A gas supply path (not shown) is connected to the upper portion of the side wall of the chamber  22 , and the gas supply path is connected to a gas supply part (not shown). In addition, an exhaust path (not shown) is connected to the bottom wall of the chamber  22 , and the exhaust path is connected to a vacuum pump (not shown). Furthermore, a flow rate control valve is installed in the gas supply path from the gas supply part to the chamber  22 , and a pressure control valve is installed in the exhaust path, so that a heat treatment can be performed on the wafer W while maintaining the interior of the chamber  22  to have a predetermined pressure by controlling the valves. 
       FIG. 2  is a cross-sectional view schematically showing the configuration of the etching device in  FIG. 1 . 
     In  FIG. 2 , the etching device  14  includes a chamber  25  that is a processing chamber, a mounting table  26  that is disposed in the chamber  25 , and a shower head  27  that is disposed to face the mounting table  26  in the upper portion of the chamber  25 . In addition, the etching device  14  includes a TMP (Turbo Molecular Pump)  28  and an APC (Adaptive pressure control) valve  30 , which is disposed between exhaust ducts extending from the TMP  28  and the chamber  25  as a variable valve for controlling the internal pressure of the chamber  25 , as an exhaust unit for exhausting gas or the like inside the chamber  25 . 
     The shower head  27  has a double-layer structure comprised of a lower portion  31  and an upper portion  32 , wherein the lower portion  31  and the upper portion  32  have a lower buffer chamber  33  and an upper buffer chamber  34 , respectively. The lower buffer chamber  33  and the upper buffer chamber  34  communicate with the interior of the chamber  25  through gas vent holes  35  and  36 , respectively. That is, the shower head  27  is configured with two plate bodies (the lower portion  31  and the upper portion  32 ) that are stacked in a layered shape having internal passages for the gases that are supplied from the lower buffer chamber  33  and the upper buffer chamber  34 , respectively, to the interior of the chamber  25 . 
     The chamber  25  is connected to an ammonia (NH 3 ) gas supply system  37  and a hydrogen fluoride (HF) gas supply system  38 . The ammonia gas supply system  37  includes an ammonia gas supply pipe  39  communicating with the lower buffer chamber  33  of the lower portion  31 , an ammonia gas valve  40  disposed on the ammonia gas supply pipe  39 , and an ammonia gas supply part  41  connected to the ammonia gas supply pipe  39 . The ammonia gas supply part  41  is configured to supply an ammonia gas to the lower buffer chamber  33  through the ammonia gas supply pipe  39  while adjusting a flow rate of the supplied ammonia gas. The ammonia gas valve  40  is configured to allow the ammonia gas supply pipe  39  to be open or closed. 
     In addition, the ammonia gas supply system  37  includes a nitrogen (N 2 ) gas supply part  42 , a nitrogen gas supply pipe  43  connected to the nitrogen gas supply part  42 , and a nitrogen gas valve  44  disposed on the nitrogen gas supply pipe  43 . The nitrogen gas supply pipe  43  is connected to the ammonia gas supply pipe  39  between the lower buffer chamber  33  and the ammonia gas valve  40 . The nitrogen gas supply part  42  is configured to supply a nitrogen gas to the lower buffer chamber  33  through the nitrogen gas supply pipe  43  and the ammonia gas supply pipe  39 . Further, the nitrogen gas supply part  42  is configured to control a flow rate of the nitrogen gas to be supplied. The nitrogen gas valve  44  is configured to allow the nitrogen gas supply pipe  43  to be open or closed. 
     In the etching device  14 , the type of gas to be supplied to the lower buffer chamber  33  and to be further supplied to the interior of the chamber  25  is selectively switched by switching the opening and closing of the ammonia gas valve  40  and the nitrogen gas valve  44 . 
     The hydrogen fluoride gas supply system  38  includes a hydrogen fluoride gas supply pipe  45  communicating with the upper buffer chamber  34  of the upper portion  32 , a hydrogen fluoride gas valve  46  disposed on the hydrogen fluoride gas supply pipe  45 , and a hydrogen fluoride gas supply part  47  connected to the hydrogen fluoride gas supply pipe  45 . The hydrogen fluoride gas supply part  47  is configured to supply a hydrogen fluoride gas to the upper buffer chamber  34  through the hydrogen fluoride gas supply pipe  45 . In addition, the hydrogen fluoride gas supply part  47  is configured to control a flow rate of the hydrogen fluoride gas to be supplied. The hydrogen fluoride gas valve  46  is configured to allow the hydrogen fluoride gas supply pipe  45  to be open or closed. A heater (not shown) is embedded in the upper portion  32  of the shower head  27  to heat the hydrogen fluoride gas inside the upper buffer chamber  34 . 
     In addition, the hydrogen fluoride gas supply system  38  includes, an argon (Ar) gas supply part  48 , an argon gas supply pipe  49  connected to the argon gas supply part  48 , and an argon gas valve  50  disposed on the argon gas supply pipe  49 . The argon gas supply pipe  49  is connected to the hydrogen fluoride gas supply pipe  45  between the upper buffer chamber  34  and the hydrogen fluoride gas valve  46 . The argon gas supply part  48  is configured to supply an argon gas to the upper buffer chamber  34  through the argon gas supply pipe  49  and the hydrogen fluoride gas supply pipe  45 . Further, the argon gas supply part  48  is configured to control a flow rate of the argon gas to be supplied. The argon gas valve  50  is configured to allow the argon gas supply pipe  49  to be open or closed. 
     In the etching device  14 , the flow rate ratios of the ammonia gas and the hydrogen fluoride gas supplied from the shower head  27  to the interior of the chamber  25  is controlled by cooperation of the ammonia gas supply part  41  of the ammonia gas supply system  37  and the hydrogen fluoride gas supply part  47  of the hydrogen fluoride gas supply system  38 . Furthermore, as described above, the etching device  14  is designed such that the ammonia gas and the hydrogen fluoride gas are initially mixed in the interior of the chamber  25  (post-mix design). According to this, it is possible to prevent the ammonia gas and the hydrogen fluoride gas from being mixed and from reacting with each other prior to being introduced into the chamber  25 . In addition, a heater (not shown) is embedded in the side wall of the chamber  25  in the etching device  14 , so that a decrease of the internal ambient temperature of the chamber  25  can be prevented, and further, the reproducibility of the oxide film removal process can be improved. Also, it is possible to limit reaction products or by-products, which are produced inside the chamber  25  during the oxide film removal process, from being attached onto the inner surface of the side wall thereof by controlling the temperature of the side wall. 
     The mounting table  26  is fixed to the bottom of the chamber  25 . A temperature controller  51  is installed in the mounting table  26  to adjust the temperature of the mounting table  26 . For example, the temperature controller  51  is provided with a pipe line through which a temperature control medium, such as water, circulates, and performs a heat-exchange with the temperature control medium flowing through the conduit. Therefore, the temperature of the mounting table  26  is controlled and the temperature of the wafer W on the mounting table  26  is controlled. 
     The mounting table  26  includes lift pins (not shown) for lifting the wafer W on the upper surface of the mounting table  26  so as to perform sending/receiving the wafer W to/from the wafer transfer mechanism  21 . In addition, the details of the oxide film removal process that is performed in the etching device  14  will be described later with reference to  FIG. 3 . 
     Referring back to  FIG. 1 , the control unit  15  includes a process controller  52  having a microprocessor (computer) for controlling respective elements of the substrate processing system  10 . The process controller  52  is connected to a user interface  53 , which has a keyboard for performing an input manipulation of commands to manage the substrate processing system  10 , a display for visually displaying an operating state of the substrate processing system  10  or the like. In addition, a storage part  54  is connected to the process controller  52 . The storage part  54  stores a control program for implementing various processes in the substrate processing system  10 , for example, supply of process gases used for the oxide film removal process performed in the etching device  14 , exhaust of an interior of the chamber  25  or the like, by means of the control of the process controller  52 , a process recipe that is a control program for implementing predetermined processes in the respective elements of the substrate processing system  10  according to a process condition, and various databases. The control unit  15  retrieves the process recipe or the like from the storage part  54 , and executes the same in the process controller  52  to thereby perform a desired process. 
     In the substrate processing system  10  described above, a sheet of wafer W is transferred from the carrier C of the loading/unloading unit  11  into the load lock chamber  12  by means of one of the transfer arms  16   a  and  16   b  of the wafer transfer mechanism  16  while the gate valve  20  is opened, and then transferred to the peak of the wafer transfer mechanism  21  in the load lock chamber  12 . Thereafter, the gate valve  20  is closed and the load lock chamber  12  is vacuum-exhausted. Subsequently, the gate valve  24  is opened and the peak of the wafer transfer mechanism  21  expands to the etching device  14  so that the wafer W is transferred into the etching device  14 . 
     Next, the peak of the wafer transfer mechanism  21  retracts to the load lock chamber  12 , and the gate valve  24  is closed. Then, an oxide film removal process is performed on the wafer W in the etching device  14  as described later. The gate valves  23  and  24  are opened after the oxide film removal process is finished, and the wafer W with the oxide film removal performed is transferred to the heat treatment device  13  by the peak of the wafer transfer mechanism  21  and then mounted on the mounting table installed in the heat treatment device  13 . Next, the wafer W on the mounting table is heated by the heater to evaporate residues of the wafer W for removal while introducing an inert gas or the like into the chamber  22 . 
     Subsequently, the gate valve  23  is opened after the residue removal is completed in the heat treatment device  13 , and the wafer W on the mounting table of heat treatment device  13  is returned to (stored in) the load lock chamber  12  by the peak of the wafer transfer mechanism  21 . Then, the wafer W is returned back to the carrier C by one of the transfer arms  16   a  and  16   b  of the wafer transfer mechanism  16 . As a result, the process for one sheet of wafer W is completed. 
     Further, the heat treatment device  13  is optional in the substrate processing system  10 . In the case where the heat treatment device  13  is not installed, the wafer W is returned to (stored in) the load lock chamber  12  by the peak of the wafer transfer mechanism  21  after the completion of the oxide film removal process, and is then returned back to the carrier C by one of the transfer arms  16   a  and  16   b  of the wafer transfer mechanism  16 . 
     Now, an oxide film removal process performed in the etching device  14  will be described.  FIGS. 3A to 3J  are process diagrams illustrating an oxide film removal process as the substrate processing method, according to an embodiment of the present disclosure.  FIGS. 3A to 3J  show respective steps of the oxide film removal process through the enlarged cross-sectional views in the vicinity of the surface of the wafer W. In addition, as illustrated in  FIG. 3A , the wafer W has a structure in which a groove is formed in a predetermined pattern on a polysilicon film  56  formed on the surface of a silicon (Si) layer  55  as a substrate, and a silicon oxide (SiO 2 ) film  57  is formed in the groove. Although a process of completely removing the silicon oxide film  57  from the wafer W is described, the present disclosure may also be applied to a process of partially removing the silicon oxide film  57 . In addition, the wafer W is generally manufactured through processes of forming a polysilicon film  56  on the surface of the silicon layer  55 , forming a resist film in a predetermined pattern on the polysilicon film  56 , forming a groove by etching the polysilicon film  56  using the resist film as an etching mask, removing the resist film, forming a silicon oxide film  57 , and performing CMP (Chemical Mechanical Polishing) with respect to the surface. Therefore, as illustrated in  FIG. 3A , the silicon oxide film  57  has the same height as the polysilicon film  56  prior to performing the oxide film removal process. The groove in which the silicon oxide film  57  is formed is, for example, an element isolation region in the memory device. 
     First, when the wafer W is mounted on the mounting table  26  and the chamber  25  is sealed, a nitrogen gas and an argon gas are supplied from the nitrogen gas supply part  42  and the argon gas supply part  48  into the chamber  25 , for example, at a flow rate of 150 sccm and for example, at a flow rate of 300 sccm, respectively. In addition, with the operation of the TMP  28 , the internal pressure of the chamber  25  is decreased to a predetermined degree of vacuum (for example, 2000 mTorr (=266.63 Pa)), which is lower than atmospheric pressure. Furthermore, the temperature of the wafer W is maintained at a constant temperature (for example, 120 degrees C.) in the range of 80 degrees C. to 120 degrees C. by means of the temperature controller  51 . In addition, the temperature of the wafer W is kept at the constant temperature on the mounting table  26  until the oxide film removal process is completed. 
     Next, the wafer W is subjected to a reaction process (hereinafter, referred to as a “COR process”) in which a portion of the surface side of the silicon oxide film  57  reacts with an ammonia gas and a hydrogen fluoride gas to produce a reaction product. In the COR process, first, an ammonia gas is supplied into the chamber  25  from the ammonia gas supply part  41 . At this time, the flow rate of ammonia gas is, for example, 300 sccm. The argon gas and the nitrogen gas are supplied to the interior of the chamber  25 , for example, at a flow rate of 150 sccm, and, for example, at a flow rate of 300 sccm, respectively. In addition, the flow rates of the nitrogen and argon gases may not be limited to the embodiment above, and the supply of one of the nitrogen gas and the argon gas may be stopped. At this time, the internal pressure of the chamber  25  is maintained, for example, at 2000 mTorr by the operation of the TMP  28 . 
     Then, a hydrogen fluoride gas is supplied into the chamber  25  from the hydrogen fluoride gas supply part  47 , for example, at a flow rate of 450 sccm while continuously supplying the ammonia gas into the chamber  25 , for example, at a flow rate of 300 sccm. For example, the ammonia gas and the hydrogen fluoride gas are supplied for three seconds. At this time, the internal pressure of the chamber  25  is also maintained, for example, at 2000 mTorr by the operation of the TMP  28 . Here, since the ammonia gas has been previously supplied into the chamber  25 , an internal atmosphere of the chamber  25  becomes a mixed gas including the hydrogen fluoride gas and the ammonia gas by supplying the hydrogen fluoride gas thereto. Thus, the silicon oxide film  57  is exposed to the mixed gas to thereby produce reaction products, such as ammonium hexa-fluorosilicate ((NH 4 ) 2 SiF 6 ) (hereinafter, referred to as “AFS”), water or the like, according to the following reaction formula. 
       SiO 2 +6HF+2NH 3 →(NH 4 ) 2 SiF 6 +2H 2 O↑
 
       FIG. 3B  schematically illustrates the COR process in which the hydrogen fluoride gas and the ammonia gas modify the silicon oxide film  57  according to the above reaction formula, and  FIG. 3C  schematically illustrates a state in which the AFS, which is a main reaction product, is formed on the silicon oxide film  57 . In addition, water, which is one of the reaction products, is evaporated. 
     Next, the wafer W is subjected to a sublimation process (hereinafter, referred to as a “PHT process”) for removing the reaction products (mainly, the AFS) that are produced in the COR process from the wafer W by sublimating the same in the etching device  14 . In the PHT process, an argon gas and/or a nitrogen gas are supplied into the chamber  25  while stopping the supply of the hydrogen fluoride gas and ammonia gas. In addition, the temperature of the wafer W is maintained to be the same as that in the COR process (for example, 120 degrees C.) in the range of 80 degrees C. to 120 degrees C. by the temperature controller  51 .  FIG. 3D  schematically illustrates a state in which the AFS, which is a main reaction product, is sublimating. 
     After the COR process of the first time and the following PHT process of the first time are completed (see  FIG. 3E ), the COR process and the PHT process are repeatedly performed several times until the silicon oxide film  57  is completely removed.  FIG. 3F  schematically illustrates the COR process of the second time and  FIG. 3G  schematically illustrates the PHT process of the second time. In addition,  FIG. 3H  schematically illustrates the COR process of the third time and  FIG. 3I  schematically illustrates the PHT of the third time. The COR process and the PHT process may be performed four times or more, or may be finished by two times according to necessity. Here, the process conditions of the COR processes of the second and third times are the same as those of the COR process of the first time, and the process conditions of the PHT processes of the second and third times are the same as those of the PHT process of the first time, so the descriptions thereof will be omitted. 
       FIG. 3J  schematically illustrates a state in which the silicon oxide film  57  is completely removed. The wafer W from which the silicon oxide film  57  has been completely removed through the oxide film removal process is transferred to the heat treatment device  13 , and then a nitrogen gas (or an argon gas) into the chamber  22  for a predetermined time (for example, 5 seconds) in a state in which the wafer W is heated to a predetermined temperature, so that residue on the wafer W are vaporized to thereby become removed. Further, the residue removal process may be performed to follow the final PHT process in the etching device  14 . 
     Meanwhile, in order to improve the throughput of the oxide film removal process, it is necessary to shorten the processing time of the PHT process, as well as the processing time of the COR process. Therefore, the processing time of the PHT process corresponds to the time taken for completely removing the reaction products that are produced in the COR process, and is also set as short as possible. However, the reaction products (mainly, the AFS) sublimate from the wafer W according to the following reaction formula in the PHT operation. 
       (NH 4 ) 2 SiF 6 (Solid)→(NH 4 ) 2 SiF 6 ↑
 
       (NH 4 ) 2 SiF 6 (Solid)→2NH 3 ↑+SiF 4 ↑+2HF↑
 
     Thus, as shown in  FIG. 4 , in some cases, the gas  58  of AFS, NH 3 , SiF 4 , or HF (hereinafter, integrally referred to as a “sublimation gas”) that has been evaporated by sublimation stagnates in the vicinity of the wafer W in the interior of the chamber  25 , thereby increasing the concentration of the sublimation gas  58 . When the concentration of the sublimation gas  58  increases, the reaction from the left side to the right side of each formula above stagnates so that the sublimation of the reaction product from the wafer W becomes stagnant. As a result, a time to remove the reaction products that are produced in the COR process is required, so there is a concern of degrading the throughput of the oxide film removal. In response thereto, the present embodiment facilitates the sublimation of the reaction product from the wafer W by removing the sublimation gas  58  from the vicinity of the wafer W in the PHT process. 
       FIGS. 5A and 5B  are process diagrams for explaining a removing method of the sublimation gas in the PHT process of the oxide film removal process in  FIG. 3 . 
     In the oxide film removal process of  FIG. 3 , an argon gas and a nitrogen gas, which are inert gases, are supplied into the chamber  25 , for example, at a total flow rate of 450 sccm in the COR process, however, an inert gas is supplied into the chamber  25  at a flow rate of at least three times (for example, 1350 scccm or more) in the PHT process than that of the inert gas of the COR process. At this time, due to the increase in the amount of supplied inert gas, the internal pressure of the chamber  25  becomes higher than that of the chamber  25  of the COR process. When the amount of the supplied inert gas increases, a flow  59  of the inert gas occurs in the chamber  25  so that the sublimation gas  58  stagnating in the vicinity of the wafer W is removed from the vicinity of the wafer W ( FIG. 5A ). As a result, the reaction from the left side to the right side in each formula proceeds, and the sublimation of the reaction products from the wafer W is accelerated ( FIG. 5B ), thereby improving the throughput of the oxide film removal. 
     As described above, since the sublimation of the reaction product from the wafer W is accelerated in the oxide film removal process of  FIGS. 3A to 3J , it is possible to shorten the processing time of the PHT process. Thus, for example, the processing time of the PHT process may be set to be 5 seconds (preferably, 3 seconds). 
     In addition, there is a case that the supply amount of the inert gas that increases in the PHT process may exceed the maximum supply amount of the nitrogen gas or argon gas from the nitrogen gas supply part  42  or argon gas supply part  48 . In response thereto, the etching device  14  has an inert gas storage tank  60  (a gas storage unit and a gas supply unit) for additionally supplying the inert gas. The inert gas storage tank  60  pre-stores a predetermined amount of inert gas (for example, a nitrogen gas or an argon gas), and is configured to supply the stored inert gas into the chamber  25  in the PHT process. Thus, it is possible to avoid a case in which the flow  59  of the inert gas does not occur in the chamber  25  due to an insufficient supply of the inert gas in the PHT process. Here, the predetermined amount of inert gas, which is stored in the inert gas storage tank  60 , is an amount that is possible to supply the inert gas at a flow rate of at least three times that of the inert gas supplied in the COR process for a predetermined period of time in the PHT process. Furthermore, the inert gas supplied from the inert gas storage tank  60  may be one of a nitrogen gas, an argon gas, or a mixed gas thereof. 
     Meanwhile, when an inert gas is rapidly supplied into the chamber  25  of a relatively large capacity at a high flow rate in the PHT process, there is a concern that the temperature of the supplied inert gas may decrease because of adiabatic expansion. When the temperature of the supplied inert gas is lowered, the wafer W mounted on the mounting table  26  is cooled, so that the sublimation of the reaction product is stagnated. In response thereto, the etching device  14  has a heater  61  (a gas heating unit) for heating the inert gas stored in the inert gas storage tank  60 . Usually, when the temperature of the wafer W falls below 80 degrees C., the sublimation of the reaction product is extremely stagnant. Thus, the heater  61  heats the inert gas stored in the inert gas storage tank  60  such that the inert gas supplied from the inert gas storage tank  60  and expanded in the interior of the chamber  25  has a temperature of 80 degrees C. or more (preferably, 120 degrees C. or more). According to this, the lowering in the temperature of the wafer W is suppressed in the PHT process, so that the degradation of the sublimation efficiency of the reaction product from the wafer W can be prevented. 
     As described above, when an inert gas is supplied into the chamber  25  at a high flow rate in the PHT process, there is a concern that particles are blown away by the generated flow  59  of the inert gas and are then attached to the wafer W in the chamber  25  and, furthermore, a problem is caused due to the particles in the electronic device formed on the wafer W. In response thereto, in the oxide film removal process of  FIGS. 3A to 3J , the supply amount of the inert gas in the PHT process is limited such that the difference between the internal pressure of the chamber  25  in the COR process and the internal pressure of the chamber  25  in the PHT process is less than 4 Torr. Since the particles are not blown away unless a change in the internal pressure of the chamber  25  is quite big, the configuration described above can prevent the particles from being blown away, so that it is possible to prevent the particles from being attached to the wafer W inside the chamber  25 . 
     In addition, since the COR process and the PHT process are repeatedly performed plural times in the oxide film removal process of  FIGS. 3A to 3J , it is possible to reduce the modification amount of the silicon oxide film  57  into the reaction product while the COR process is performed one time. According to this, the amount of the reaction product to be removed in the PHT process can be reduced, and the reaction product can be surely removed. As a result, it is possible to prevent the remaining reaction product from covering the silicon oxide film  57  and from hindering the reaction of the silicon oxide film  57  and the mixed gas in the subsequent COR process. Therefore, the modification efficiency into the reaction product can be maintained at a high level, thereby surely improving the throughput of the oxide film removal. 
       FIG. 6  is a graph showing an etching amount in the oxide film removal process of  FIGS. 3A to 3J  when varying the supply amount of the inert gas in the PHT process. The supply amount of the inert gas was set to have three levels (specifically, 2400 sccm, 1200 sccm, and 450 sccm). In addition, since there is a case that a silicon nitride (SiN) film is formed on the wafer W, as well as the silicon oxide film  57 , and the silicon nitride also reacts with the mixed gas containing the hydrogen fluoride gas and the ammonia gas to thereby produce a reaction product in the COR process, the etching amount of the silicon nitride film, as well as the etching amount of the silicon oxide film  57 , was measured. In addition, the COR process was performed for 3 seconds, and in the COR operation, an ammonia gas was supplied at a flow rate of 300 sccm, a hydrogen fluoride gas was supplied at a flow rate of 450 sccm, and an inert gas was supplied at a flow rate of 450 sccm, so that the internal pressure of the chamber  25  is maintained at 2000 mTorr. In addition, the PHT process was continued for 5 seconds, and the COR process and PHT process were repeated 50 times. 
     As shown in  FIG. 6 , the etching amount of the silicon oxide film  57  significantly increased in the case where the supply amount of the inert gas in the PHT process is at least three times (2400 sccm) than the supply amount of the inert gas in the COR process, compared with the case where the supply amount of the inert gas in the PHT process is less than three times (1200 sccm or 450 sccm) than the supply amount of the inert gas in the COR process. More specifically, the etching amount was 467.7 Å when the flow rate was 450 sccm, and the etching amount was 450.3 Å when the flow rate was 1200 sccm, whereas the etching amount was 988.8 Å when the flow rate was 2400 sccm. This is estimated because the stronger flow  59  of the inert gas occurs in the chamber  25  with an increase in the supply amount of the inert gas in the PHT process and the sublimation of the reaction product from the wafer W is accelerated, so that the remaining silicon oxide film  57  is prevented from being covered by the reaction product that cannot be completely removed, and the silicon oxide film  57  smoothly reacts with the mixed gas in the subsequent COR process so that the modification of the silicon oxide film  57  into the reaction product is not stagnant. 
     In addition, the etching amount of the silicon nitride film is reduced in the case where the supply amount of the inert gas in the PHT process is three times (2400 sccm) or more than the supply amount of the inert gas in the COR process, compared to the case where the supply amount of the inert gas in the PHT process is less than three times (1200 sccm or 450 sccm) than the supply amount of the inert gas in the COR process. More specifically, the etching amount was 2.2 Å when the flow rate was 450 sccm, and the etching amount was 2.1 Å when the flow rate was 1200 sccm, whereas the etching amount was 0.3 Å when the flow rate was 2400 sccm. This is estimated because the silicon oxide film  57  smoothly reacts with the mixed gas in the COR process at a flow rate of 2400 sccm so that the mixed gas to react with the silicon nitride film decreases, and as a result, the modification of the silicon nitride film into the reaction product does not proceed. In addition, the selection ratio of the silicon oxide film  57  to the silicon nitride film was 209.3 at a flow rate of 450 sccm of the inert gas in the PHT process, and the selection ratio was 210.6 at a flow rate of 1200 sccm, whereas the selection ratio was 3676.0 at a flow rate of 2400 sccm. That is, it can be seen that it is preferable to increase the supply amount of the inert gas in the PHT process so as not to positively remove the silicon nitride film in the case of using the silicon nitride film as an etching stop film. 
     Until now, although the embodiment of the present disclosure has been described as above, the embodiment of the present disclosure is not limited thereto. 
     For example, the type of a silicon oxide film to be removed in the oxide film removal process is not particularly limited, and may be a variety of silicon oxide films, such as a natural oxide film, a BPSG film, an HDP-SiO 2  film, or the like. In addition, although the nitrogen gas and the argon gas have been used as the inert gas in the PHT process of the above embodiment, one of them may be used, or other inert gases, such as a helium gas or a xenon gas, or a mixture thereof may be used. 
     Furthermore, when an inert gas is supplied into the chamber  25  at a high flow rate in the PHT process, since the opening area of the APC valve  30  is limited, the conductance of the exhaust gas may be reduced and the sublimation gas  58  may stagnate in the interior of the chamber  25  so that there is a concern that the occurrence of the inert gas flow  59  may be difficult. In response thereto, as shown in  FIG. 7A , a bypass line  62  is installed to connect the exhaust duct  29  to the TMP  28  by detouring the APC valve  30  in the exhaust unit of the etching device  14 , and a bypass valve  63  is installed on the bypass line  62  for opening or closing thereof. At this time, the bypass line  62  is opened by means of the bypass valve  63  in the PHT process to allow the exhaust gas to flow from the chamber  25  to the TMP  28  through the bypass line  62 , as well as through the APC valve  30 . According to this, it is possible to improve the conductance of the exhaust gas and to prevent the sublimation gas  58  from stagnating in the interior of the chamber  25 , so that it ensures the occurrence of the inert gas flow  59  in the chamber  25 . 
     In addition, a buffer tank  64  is installed on the bypass line  62 , and a tank valve  65  is installed to separate the exhaust duct  29  and the buffer tank  64  from each other, or a tank valve  66  is installed to separate the buffer tank  64  and the TMP  28  from each other. At this time, the tank valve  65  is opened to communicate the exhaust duct  29  with the buffer tank  64  in the PHT process so that the exhaust gas containing the sublimation gas  58  that has failed to completely pass through the APC valve  30  is introduced and stored into the buffer tank  64 . Thus, it is possible to prevent the sublimation gas  58  from stagnating in the interior of the chamber  25 . Further, in the subsequent COR process, the tank valve  66  is opened to communicate the buffer tank  64  with the TMP  28 , so that the exhaust gas stored in the buffer tank  64  is exhausted by means of the TMP  28 . 
     A supply timing of an ammonia gas, a hydrogen fluoride gas, or an inert gas (argon gas or nitrogen gas) may be more finely controlled in the COR process.  FIG. 8A  is a timing chart showing a supply start or supply stop of various gases in the COR process and the PHT process. In addition, for each of the ammonia gas and the hydrogen fluoride gas, “ON” indicates that a gas is supplied and “OFF” indicates that the supply of gas is stopped. Further, the supply of the inert gas does not stop in the course of the process, and “BIG” represents that a supply amount of the inert gas is big and “SMALL” represents that a supply amount of the inert gas is small. 
     In the timing chart of  FIG. 8A , the COR process is initiated at time t0 so that an ammonia gas and an inert gas are supplied into the chamber  25 . In addition, a hydrogen fluoride gas is supplied into the chamber  25  at time t1. At the following time t2, in order to switch from the COR process to the PHT process, the supply amount of the inert gas increases while the supply of the hydrogen fluoride gas and the ammonia gas is stopped to increase the internal pressure of the chamber  25 . Thereafter, the PHT process is terminated at time t3. 
       FIG. 8B  is a chart showing an actual change in the internal pressure of the chamber  25  and the supply/stop state of gases when the timing chart of  FIG. 8A  is implemented. As described with reference to  FIG. 2 , the ammonia gas valve  40  is installed on the ammonia gas supply pipe  39  that connects the ammonia gas supply part  41  and the chamber  25 , and a specific pipe length of the ammonia gas supply pipe  39  exits from the ammonia gas valve  40  to the chamber  25 . Likewise, the hydrogen fluoride gas valve  46  is installed on the hydrogen fluoride gas supply pipe  45  that connects the hydrogen fluoride gas supply part  47  and the chamber  25 , and a specific pipe length of the hydrogen fluoride gas supply pipe  45  exists from the hydrogen fluoride gas valve  46  to the chamber  25 . 
     Therefore, even if the ammonia gas valve  40  and the hydrogen fluoride gas valve  46  are opened at time t0 and time t1, respectively, as shown in  FIG. 8B , there is a delay time A for the ammonia gas and the hydrogen fluoride gas to actually reach the interior of the chamber  25 . Here, for the sake of simple explanation, it is assumed that the ammonia gas and the hydrogen fluoride gas have the same delay time A. Further, even when the ammonia gas valve  40  and the hydrogen fluoride gas valve  46  are closed at time t2 in order to stop the supply of the ammonia gas and hydrogen fluoride gas, the ammonia gas and hydrogen fluoride gas are continuously supplied into the chamber  25  for a while. 
     Here, in the oxide film removal process of  FIG. 3 , since the processing time of the COR process of one time is short (3 seconds), when the supply amount of the inert gas increases before a predetermined amount of hydrogen fluoride gas is supplied into the chamber  25 , a portion of the hydrogen fluoride gas does not participate in the reaction with the silicon oxide film  57  and is removed from the vicinity of the wafer W and the distribution uniformity of the hydrogen fluoride gas is degraded in the chamber  25  by the inert gas flow  59  occurring due to the increase in the supply amount of the inert gas. As a result, there are concerns that the modification amount of the silicon oxide film  57  into the reaction product is reduced, and the in-plane uniformity with respect to the generation of the reaction product is degraded. In addition, since the supply time of the ammonia gas is longer than the supply time of the hydrogen fluoride gas, the delay of the ammonia gas supply does not really matter. 
     Accordingly, the timing of stopping the supply of the hydrogen fluoride gas into the chamber  25  may be adjusted to the timing of increasing the amount of supplied inert gas at a time of transition from the COR process to the PHT process by adjusting the timing of increasing the supply amount of the inert gas according to the supply delay caused by the length of the hydrogen fluoride gas supply pipe  45 . 
       FIG. 8C  is a timing chart of a modified example of the oxide film removal process. In the timing chart of the ammonia gas, the hydrogen fluoride gas, and the inert gas shown in  FIG. 8C , the supply amount of the inert gas increases at time t4, which is later than time t2 by a time A. In addition, the end timing of the PHT process is prolonged from time t3 to time t5, which is later by a time A, to secure the processing time of the PHT process. Here, the time A is dependent on the length of the hydrogen fluoride gas supply pipe  45  from the hydrogen fluoride gas valve  46  to the chamber  25 , and may be approximately 1 second to 3 seconds (preferably, 2 seconds). Meanwhile, it is not preferable to set a long time because the throughput is lowered. 
       FIG. 8D  is a chart showing an actual change in the internal pressure of the chamber  25  and the supply/stop state of gases when the timing chart of  FIG. 8C  is implemented. As shown in  FIG. 8D , the timing of stopping the supply of the hydrogen fluoride gas into the chamber  25  matches the timing of increasing the amount of supplied inert gas by increasing the amount of supplied inert gas at time t4, which is later than time t2 by a time A. According to this, since the inert gas flow  59  occurs after a predetermined amount of hydrogen fluoride gas completely reacts with the silicon oxide film  57 , it is possible to eliminate the problem in which a portion of the hydrogen fluoride gas does not react with the silicon oxide film  57  and is not removed from the vicinity of the wafer W, and the distribution uniformity of the hydrogen fluoride gas is prevented from being degraded in the chamber  25 . As a result, a predetermined amount of silicon oxide film  57  can be surely modified into the reaction product, and the in-plane uniformity with respect to the generation of the reaction product can be improved. 
     In addition, the present disclosure may be achieved by supplying a storage unit  54  in which a program code of software for executing the functions of the embodiment described above is recorded to the process controller  52  provided in the control unit  15  and by reading and executing the program code stored in the storage unit  54  by a CPU of the process controller  52 . 
     In this case, the program code itself that is read out from the storage unit  54  implements the functions of the embodiment described above, and the program code and the storage unit  54  storing the same constitute the present disclosure. 
     Further, the storage unit  54 , for example, may be RAM, NV-RAM, a floppy (registered trademark) disc, a hard disc, a magneto-optical disc, an optical disc, such as CD-ROM, CD-R, CD-RW, or DVD (DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), a magnetic tape, a non-volatile memory card, or other ROMs that can memorize the program code. Furthermore, the program code may be downloaded from a computer or database (not shown) that is connected to the Internet, a commercial network, or a local area network to then be provided to the process controller  52 . 
     In addition, the process controller  52  may execute the read program code to implement the functions of the embodiment above, or an OS (Operating System) that is operated in the CPU may execute all or some of the actual processes based on instructions of the program code to implement the functions of the embodiment above. 
     Furthermore, the program code read out from the storage unit  54  may be written in the memory provided in the function extension board that is inserted into the process controller  52  or in the function extension unit that is connected to the process controller  52 , and a CPU provided in the function extension board or function extension unit may execute all or some of the actual processes based on instructions of the program code to implement the functions of the embodiment above. 
     The program code may be configured in the form of an object code, a program code executed by an interpreter, script data supplied to the OS, or the like. 
     According to the present disclosure, since the internal pressure of the processing chamber in the sublimation process becomes higher than the internal pressure of the processing chamber in the reaction operation by supplying an inert gas into the processing chamber, an inert gas flow occurs in the interior of the processing chamber in the sublimation process so that the reaction product gas that sublimates from the substrate can be removed from the vicinity of the substrate by means of the inert gas flow. As a result, the sublimation of the reaction product from the substrate is accelerated, thereby improving the throughput of the oxide film removal. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.