Patent Publication Number: US-2023146375-A1

Title: Substrate processing method and substrate processing apparatus

Description:
TECHNICAL FIELD 
     The present disclosure relates to a substrate processing method and a substrate processing apparatus. 
     BACKGROUND 
     For example, a substrate processing apparatus for embedding a film in a substrate having irregularities formed therein is known. 
     Patent Document 1 discloses a film forming method including: a step of mounting, in multiple stages into a reaction tube, a plurality of substrates in which a pattern having depressions is formed; a film forming step of forming silicon oxide films on the plurality of substrates by supplying a silicon-containing gas and an oxygen-containing gas to the reaction tube; and an etching step of etching the silicon oxide films formed in the film forming step by supplying a hydrofluoric acid gas and an ammonia gas to the reaction tube, wherein the film forming step and the etching step are alternately repeated. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-199306 
       
    
     The present disclosure provides some embodiments of a substrate processing method and a substrate processing apparatus which are capable of achieving good etching characteristics. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a method of etching a SiN film formed on a substrate by supplying a HF gas at a processing temperature is 450 degrees C. or higher. 
     According to an aspect, it is possible to provide a substrate processing method and a substrate processing apparatus which are capable of achieving good etching characteristics. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic diagram illustrating a configuration example of a substrate processing apparatus. 
         FIG.  2    is one example of a time chart illustrating an etching process in a first example of the substrate processing apparatus. 
         FIG.  3 A  is one example of a schematic cross-sectional view of a substrate in the etching process of the first example. 
         FIG.  3 B  is one example of the schematic cross-sectional view of the substrate in the etching process of the first example. 
         FIG.  4    is one example of a time chart illustrating an etching process in a second example of the substrate processing apparatus. 
         FIG.  5 A  is one example of a schematic cross-sectional view of a substrate in the etching process of the second example. 
         FIG.  5 B  is one example of the schematic cross-sectional view of the substrate in the etching process of the second example. 
         FIG.  5 C  is one example of the schematic cross-sectional view of the substrate in the etching process of the second example. 
         FIG.  5 D  is one example of the schematic cross-sectional view of the substrate in the etching process of the second example. 
         FIG.  5 E  is one example of the schematic cross-sectional view of the substrate in the etching process of the second example. 
         FIG.  6    is one example of a graph illustrating a relationship between the number of cycles and an etching amount in the etching process of the second example. 
         FIG.  7    is one example of a time chart illustrating an etching process in a third example of the substrate processing apparatus. 
         FIG.  8    is one example of a graph illustrating a relationship between the number of cycles and an etching amount in the etching process of the third example. 
         FIG.  9    is one example of a flowchart illustrating one example of a film forming process performed by the substrate processing apparatus. 
         FIG.  10    is one example of a time chart illustrating a film forming process performed by the substrate processing apparatus. 
         FIG.  11    is one example of a time chart illustrating an etching process in a fourth example of the substrate processing apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments for implementing the present disclosure will be described with reference to the drawings. In each drawing, the same components will be designated by like reference numerals with the descriptions thereof omitted 
     [Substrate Processing Apparatus] 
     A substrate processing apparatus  100  according to the present embodiment will be described using  FIG.  1   .  FIG.  1    is a schematic diagram illustrating a configuration example of the substrate processing apparatus  100 . 
     The substrate processing apparatus  100  includes a roofed cylindrical processing container  1  with its lower end opened. The entire processing container  1  is made of, for example, quartz. A ceiling plate  2  made of quartz is provided in the vicinity of an upper end inside the processing container  1  so that a region defined below the ceiling plate  2  is sealed. A metal-made manifold  3  formed in a cylindrical shape is connected to a lower end opening of the processing container  1  via a seal member  4  such as an O ring or the like. 
     The manifold  3  supports the lower end of the processing container  1 . A wafer boat  5  in which a plurality of (for example, 25 to 150) semiconductor wafers (hereinafter referred to as “wafers W”) as substrates are placed in multiple stages is inserted into the processing container  1  from below the manifold  3 . As described above, the plurality of substrates W are substantially horizontally accommodated in the processing container  1  at intervals along a vertical direction. The wafer boat  5  is formed of, for example, quartz. The wafer boat  5  includes three rods  6  (of which only two are illustrated in  FIG.  1   ). The plurality of substrates W are supported by grooves (not illustrated) formed in the rods  6 . 
     The wafer boat  5  is placed on a table  8  via a quartz-made heat-insulating cylinder  7 . The table  8  is supported on a rotary shaft  10  that penetrates a lid  9  made of metal (stainless steel) and configured to open and close a lower end opening of the manifold  3 . 
     A magnetic fluid seal  11  is provided in the penetrating portion of the rotary shaft  10 . The magnetic fluid seal  11  rotatably supports the rotary shaft  10  while airtightly sealing the rotary shaft  10 . A seal member  12  for keeping the interior of the processing container  1  in a sealed state is provided between a peripheral portion of the lid  9  and the lower end of the manifold  3 . 
     The rotary shaft  10  is attached to the tip of an arm  13  supported by, for example, an elevating mechanism (not illustrated) such as a boat elevator or the like. The wafer boat  5  and the lid  9  are raised and lowered together and are inserted into and removed from the interior of the processing container  1 . Alternatively, the table  8  may be fixedly provided at the side of the lid  9  so that the wafer W can be processed without rotating the wafer boat  5 . 
     Further, the substrate processing apparatus  100  includes a gas supplier  20  that supplies predetermined gases, such as a processing gas, a purge gas or the like, into the processing container  1 . 
     The gas supplier  20  includes gas supply pipes  21 ,  22 ,  23 , and  24 . The gas supply pipe  21  is formed of, for example, quartz, and is constituted with a quartz pipe that passes through a sidewall of the manifold  3  inward and is bent upward. The gas supply pipe  22  is formed of, for example, quartz, and passes through the sidewall of the manifold  3  inward, is bent upward, and extends vertically. A plurality of gas holes  22   g  is formed at predetermined intervals in a vertical portion of the gas supply pipe  22  over a vertical length corresponding to a wafer support range of the wafer boat  5 . A gas is discharged via each gas hole  22   g  in a horizontal direction. The gas supply pipe  23  is formed of, for example, quartz, and passes through the sidewall of the manifold  3  inward, is bent upward, and extends vertically. In a vertical portion of the gas supply pipe  23 , a plurality of gas holes  23   g  is formed at predetermined intervals over the vertical length corresponding to the wafer support range of the wafer boat  5 . A gas is discharged via each gas hole  23   g  in the horizontal direction. The gas supply pipe  24  is formed of, for example, quartz, and is constituted with a short quartz pipe provided to penetrate the sidewall of the manifold  3 . 
     An etchant gas is supplied from a gas source  21   a  to the gas supply pipe  21  via a gas pipe. The gas pipe is provided with a flow controller  21   b  and an on-off valve  21   c . With this configuration, the etchant gas from the gas source  21   a  is supplied into the processing container  1  via the gas pipe and the gas supply pipe  21 . As the etchant gas, a hydrogen halide such as, for example, hydrogen fluoride (HF) may be used. 
     The vertical portion (in which the gas holes  22   g  are formed) of the gas supply pipe  22  is provided inside the processing container  1 . The gas supply pipe  22  is supplied with a processing gas from the gas source  22   a  via the gas pipe. The gas pipe is provided with a flow controller  22   b  and an on-off valve  22   c . With this configuration, the processing gas from the gas source  22   a  is supplied into the processing container  1  via the gas pipe and the gas supply pipe  22 . In addition, the processing gas supplied from the gas source  22   a  will be described later. 
     The vertical portion (in which the gas holes  23   g  are formed) of the gas supply pipe  23  is provided in a plasma generation space which will be described later. The gas supply pipe  23  is supplied with a processing gas from the gas source  23   a  via the gas pipe. The gas pipe is provided with a flow controller  23   b  and an on-off valve  23   c . With this configuration, the processing gas from the gas source  23   a  is supplied to the plasma generation space via the gas pipe and the gas supply pipe  22 , is plasmarized in the plasma generation space, and is supplied into the processing container  1 . In addition, the processing gas supplied from the gas source  23   a  will be described later. 
     The gas supply pipe  24  is supplied with a purge gas from a purge gas source (not illustrated) via a gas pipe. The gas pipe (not illustrated) is provided with a flow controller (not illustrated) and an on-off valve (not illustrated). With this configuration, the purge gas from the purge gas source is supplied into the processing container  1  via the gas pipe and the gas supply pipe  24 . As the purge gas, an inert gas such as, for example, argon (Ar), nitrogen (N 2 ) or the like, may be used. Although the case in which the purge gas is supplied from the purge gas source into the processing container  1  via the gas pipe and the gas supply pipe  24  has been described, the present disclosure is not limited thereto. The purge gas may be supplied from either the gas supply pipe  21  or the gas supply pipe  22 . 
     A plasma generation mechanism  30  is formed in a portion of the sidewall of the processing container  1 . The plasma generation mechanism  30  forms the processing gas from the gas source  23   a  into plasma. 
     The plasma generation mechanism  30  includes a plasma partition wall  32 , a pair of plasma electrodes  33  (only one illustrated in  FIG.  1   ), a power feed line  34 , a radio-frequency power supply  35 , and an insulating protective cover  36 . 
     The plasma partition wall  32  is hermetically welded to an outer wall of the processing container  1 . The plasma partition wall  32  is formed of quartz, for example. The plasma partition wall  32  is concave in a cross section and covers an opening  31  formed in the sidewall of the processing container  1 . The opening  31  is formed to be elongated in the vertical direction so as to cover all the substrates W supported by the wafer boat  5  in the vertical direction. The gas supply pipe  23  for discharging the processing gas is arranged in an inner space defined by the plasma partition wall  32  and communicating with the interior of the processing container  1 , that is, the plasma generation space. In addition, the gas supply pipe  22  for discharging the processing gas is provided at a position close to the substrate W along an inner sidewall of the processing container  1  outside the plasma generation space. 
     The pair of plasma electrodes  33  (only one illustrated in  FIG.  1   ) have an elongated shape, and are arranged on outer surfaces of both sidewalls of the plasma partition wall  32  to face each other along the vertical direction. Each plasma electrode  33  is held by, for example, a holding portion (not illustrated) provided on the side surface of the plasma partition wall  32 . The power feed line  34  is connected to a lower end of each plasma electrode  33 . 
     The power feed line  34  electrically connects each plasma electrode  33  and the radio-frequency power supply  35 . In the illustrated example, one end of the power feed line  34  is connected to the lower end of each plasma electrode  33  and the other end thereof is connected to the radio-frequency power supply  35 . 
     The radio-frequency power supply  35  is connected to the lower end of each plasma electrode  33  via the power feed line  34 , and supplies radio-frequency power of, for example, 13.56 MHz, to the pair of plasma electrodes  33 . With this configuration, the radio-frequency power is applied into the plasma generation space defined by the plasma partition wall  32 . The processing gas discharged from the gas supply pipe  22  is plasmarized inside the plasma generation space to which the radio-frequency power is applied, and is supplied to the interior of the processing container  1  via the opening  31 . 
     The insulating protective cover  36  is provided outside the plasma partition wall  32  so as to cover the plasma partition wall  32 . A refrigerant passage (not illustrated) is provided in an inner portion of the insulating protective cover  36 . The plasma electrodes  33  are cooled by allowing a refrigerant such as a cooled nitrogen (N 2 ) gas to flow through the refrigerant passage. Moreover, a shield (not illustrated) may be provided between the plasma electrodes  33  and the insulating protective cover  36  so as to cover the plasma electrodes  33 . The shield is formed of a good conductor such as, for example, metal or the like, and is grounded. 
     An exhaust port  40  for evacuating the interior of the processing container  1  is provided in a sidewall portion of the processing container  1 , which faces the opening  31 . The exhaust port  40  is formed to be elongated vertically in correspondence to the wafer boat  5 . An exhaust port cover member  41  formed in a U-shape in cross-section so as to cover the exhaust port  40  is provided in a portion of the processing container  1 , which corresponds to the exhaust port  40 . The exhaust port cover member  41  extends upward along the sidewall of the processing container  1 . An exhaust pipe  42  for exhausting the processing container  1  via the exhaust port  40  is connected to a lower portion of the exhaust port cover member  41 . A pressure control valve  43  for controlling an internal pressure of the processing container  1 , and an exhaust device  44  including a vacuum pump and the like are connected to the exhaust pipe  42 . The interior of the processing container  1  is exhausted by the exhaust device  44  via the exhaust pipe  42 . 
     In addition, a cylindrical heating mechanism  50  for heating the processing container  1  and the substrates W in the processing container  1  is provided so as to surround the outer periphery of the processing container  1 . 
     In addition, the substrate processing apparatus  100  includes a controller  60 . The controller  60  controls, for example, the operation of each part of the substrate processing apparatus  100 , for example, the supply and cutoff of each gas by the opening and closing of the on-off valves  21   c  to  23   c , the control of the flow rate of each gas by the flow controllers  21   b  to  23   b , and the exhaust by the exhaust device  44 . Moreover, the controller  60  performs, for example, the on-off control of the radio-frequency power by the radio-frequency power supply  35 , and the control of the temperature of the substrates W by the heating mechanism  50 . 
     The controller  60  may be, for example, a computer or the like. Further, a computer program for executing the operation of each part of the substrate processing apparatus  100  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. 
     &lt;Etching Process in First Example&gt; 
     Next, one example of substrate processing performed by the substrate processing apparatus  100  illustrated in  FIG.  1    will be described.  FIG.  2    is one example of a time chart illustrating an etching process in the first example by the substrate processing apparatus  100 . Here, the substrate processing apparatus  100  etches a SiN film formed on the substrate W. 
     In the etching process of the first example, a HF gas is supplied as an etchant gas from the gas supply pipe  21 , and a N 2  gas is supplied as a carrier gas from the gas supply pipe  24 . Further, in the substrate processing apparatus  100  that performs the etching process of the first example, the gas supply pipes  22  and  23  and the plasma generation mechanism  30  may be omitted. 
     Here, preferable ranges of etching conditions of the SiN film in the etching process of the first example are as follows. 
     Temperature: 450 to 650 degrees C. 
     Pressure: 5 to 150 Torr 
     Flow rate of HF gas: 500 to 5,000 sccm 
     Flow rate of N 2  gas: 500 to 5,000 sccm 
       FIG.  3 A  is one example of a schematic cross-sectional view of the substrate W before the etching process of the first example. A concave structure  800  such as a trench is formed in a surface of the substrate W. A conformal SiN film  810  is also formed on the surface of the substrate W. Further, a shoulder portion  811  of the SiN film  810  projects toward an opening portion  801  of the concave structure  800 , so that the opening portion  801  of the concave structure  800  is closed. 
       FIG.  3 B  is one example of a schematic cross-sectional view of the substrate W after the etching process of the first example. According to the etching process of the first example, the shoulder portion  811  of the SiN film  810  in the opening portion  801  is etched more than a middle portion  802  and an inner portion  803  of the concave structure  800 . This makes it possible to prevent the opening portion  801  of the SiN film  810  from being closed. 
     Here, when a processing temperature at the time of etching is set to 120 degrees C. or lower, ammonium silicofluoride is formed on the surface of the SiN film  810  by the HF gas. Then, by heating the substrate W to a temperature of 160 degrees C. or higher, the ammonium silicofluoride on the surface is sublimated and the SiN film  810  is etched. 
     In this process, after performing the process of forming the ammonium silicofluoride using silicon or nitrogen atoms contained in the SiN film  810 , an ammonium silicofluoride layer is removed by the supply of heat energy by which the ammonium silicofluoride is sublimated and the pressure conditions. Simultaneously, a portion of the SiN film consumed during the formation of the ammonium silicofluoride is reduced. The ammonium silicofluoride can be formed uniformly or non-uniformly on the SiN film coated on the concave structure  800  by the conditions of temperature, gas, and pressure in the process of forming the ammonium silicofluoride. 
     On the other hand, in the etching process of the first example, a processing temperature at the time of etching is set to 550 degrees C. In this case, radical species of the HF gas are produced inside the processing container  1  at a high temperature. The radical species of the HF gas collide (attack) with the surface of the SiN film  810 , so that reaction products such as SiFx or NFx are produced. The reaction products are discharged from the interior of the processing container  1  by the exhaust device  44 . As a result, the SiN film  810  is etched. Here, in the etching process of the first example, an etching profile (conformality) may be changed by changing the condition of gas or pressure when removing the SiN film coated on the concave structure  800 . The etching conformality also varies with a ratio of depth and width dimensions of the concave structure  800 . In a method of the first example, according to the pressure condition when the etching gas is supplied, a change may be made from conformal etching to a profile in which an opening side is preferentially etched. Increasing the processing pressure as the changing means provides the following effects. Many collisions may occur at the opening portion  801  rather than the middle portion  802  and the inner portion  803  of the concave structure  800 . Thus, the shoulder portion  811  of the SiN film  810  is etched more. As a result, an opening shape (e.g., a V-shape) in which the opening portion  801  widens may be obtained. Further, in a film forming process as a subsequent process, an easy-to-embed shape in which a film is easy to be embedded in the concave structure  800  may be obtained. In addition, an inert gas such as an Ar gas, or a reducing gas such as hydrogen or NH 3  may be supplied in parallel to the introduction of the HF gas. Moreover, the etching gas may be activated by applying RF in parallel to the introduction of the HF gas. This makes it possible to control a production concentration of the active species effective for etching. Thus, the change may be made from conformal etching to the profile in which the opening side is preferentially etched as described above. 
     &lt;Etching Process of Second Example&gt; 
       FIG.  4    is one example of a time chart illustrating an etching process of a second example performed by the substrate processing apparatus  100 . Here, the substrate processing apparatus  100  etches the SiN film formed on the substrate W. 
     In the etching process of the second example, a HF gas is supplied as an etchant gas from the gas supply pipe  21 , a DCS (dichlorosilane, SiH 2 Cl 2 ) gas is supplied as a processing gas from the gas supply pipe  22 , a NH 3  gas is supplied as a processing gas from the gas supply pipe  23 , and a N 2  gas is supplied as a carrier gas from the gas supply pipe  24 . In addition, the processing gas supplied from the gas supply pipe  22  is not limited to the DCS gas, but may be HCDS (hexachlorodisilane), halogenated silanes such as fluorine, bromine, iodine and the like, higher-order silanes, aminosilane compounds, silylamines, or the like. Further, the processing gas supplied from the gas supply pipe  23  is not limited to the NH 3  gas, but may be nitrogen, a mixed gas of nitrogen and hydrogen and argon, helium, or the like, a nitrogen-containing compound such as a hydrazine compound, or the like. 
     The etching process illustrated in  FIG.  4    is a process of etching a SiN film formed on the substrate W by repeating a predetermined number of cycles including step S 201  of supplying the HF gas, step S 202  of performing a purging process, step S 203  of supplying the DCS gas, step S 204  of performing the purging process, step S 205  of supplying the HF gas, step S 206  of performing the purging process, step S 207  of supplying the NH 3  gas while applying RF power, and step S 208  of performing the purging process. In  FIG.  4   , one cycle is merely illustrated. Moreover, in steps S 201  to S 208 , the N 2  gas as a purge gas is constantly (continuously) supplied from the gas supply pipe  24  during the etching process. 
     Step S 201  of supplying the HF gas is a step of supplying the HF gas into the processing container  1 . In step S 201  of supplying the HF gas, the HF gas is supplied into the processing container  1  from the gas source  21   a  via the gas supply pipe  21  by opening the on-off valve  21   c.    
     Step S 202  of performing the purging process is a step of purging the excess HF gas or the like inside the processing container  1 . In step S 202  of performing the purging process, the on-off valve  21   c  is closed to stop the supply of the HF gas. As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess HF gas and the like inside the processing container  1 . 
     Step S 203  of supplying the DCS gas is a step of supplying the DCS gas. In step S 203  of supplying the DCS gas, the DCS gas is supplied from the gas source  22   a  into the processing container  1  via the gas supply pipe  22  by opening the on-off valve  22   c.    
     Step S 204  of performing the purging process is a step of purging the excess DCS gas or the like inside the processing container  1 . In step S 204  of performing the purging process, the on-off valve  22   c  is closed to stop the supply of the DCS gas. As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess DCS gas and the like inside the processing container  1 . 
     Step S 205  of supplying the HF gas is a step of supplying the HF gas into the processing container  1 . In step S 205  of supplying the HF gas, the HF gas is supplied from the gas source  21   a  into the processing container  1  via the gas supply pipe  21  by opening the on-off valve  21   c.    
     Step S 206  of performing the purging process is a step of purging the excess HF gas or the like inside the processing container  1 . In step S 206  of performing the purging process, the on-off valve  21   c  is closed to stop the supply of the HF gas. As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess HF gas and the like inside the processing container  1 . 
     Step S 207  of supplying the NH 3  gas while applying the RF power is a step of supplying active species of the NH 3  gas. In step S 207 , the NH 3  gas is supplied from the gas source  23   a  inward of the plasma partition wall  32  via the gas supply pipe  23  by opening the on-off valve  23   c . Further, RF is applied from the radio-frequency power supply  35  to the plasma electrodes  33  to generate plasma inside the plasma partition wall  32 . Active species of the NH 3  gas are generated and are supplied into the processing container  1  via the opening  31 . 
     Step S 208  of performing the purging process is a step of purging the excess NH 3  gas, reaction products ((NH 4 ) 2 SiF 6  to be described later), or the like inside the processing container  1 . In step S 208  of performing the purging process, the on-off valve  23   c  is closed to stop the supply of the NH 3  gas. Further, the application of RF to the plasma electrodes  33  by the radio-frequency power supply  35  is stopped to stop the plasma generation inside the plasma partition wall  32 . As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess NH 3  gas, the reaction products, or the like inside the processing container  1 . 
     By repeating the above cycle, the SiN film formed on the substrate W is etched. 
     Here, preferable ranges of etching conditions used in the etching process of the second example are as follows. 
     Temperature: 250 to 630 degrees C. 
     Pressure: 0.1 to 100 Torr 
     Flow rate of HF gas: 500 to 5,000 sccm 
     Flow rate of DCS gas: 500 to 5,000 sccm 
     Flow rate of NH 3  gas: 500 to 10,000 sccm 
     Flow rate of N 2  gas: 50 to 5,000 sccm 
     Time period of step S 201 : 2 to 30 seconds 
     Time period of step S 202 : 5 to 30 seconds 
     Time period of step S 203 : 2 to 30 seconds 
     Time period of step S 204 : 2 to 30 seconds 
     Time period of step S 205 : 2 to 30 seconds 
     Time period of step S 206 : 5 to 30 seconds 
     Time period of step S 207 : 5 to 60 seconds 
     Time period of step S 208 : 5 to 30 seconds 
     RF power: 50 to 500 W 
     The etching process of the second example will be further described with reference to  FIGS.  5 A to  5 E .  FIGS.  5 A to  5 E  are examples of schematic cross-sectional views of the substrate W in the etching process of the second example. 
       FIG.  5 A  shows a state of the surface of the substrate W before starting step S 201  of supplying the HF gas. As illustrated in  FIG.  5 A , NH groups exist at the end of the surface of the substrate W. 
     In step S 201  of supplying the HF gas, the HF gas is supplied into the processing container  1  and the substrate W is exposed to the HF gas so that the end is fluorinated as illustrated in  FIG.  5 B . 
     In step S 203  of supplying the DCS gas, the DCS gas is supplied into the processing container  1  and the substrate W is exposed to the DCS gas so that the NH groups at the end are substituted with SiH groups or SiCl groups derived from DCS as illustrated in  FIG.  5 C . 
     In step S 205  of supplying the HF gas, the HF gas is supplied into the processing container  1  and the substrate W is exposed to the HF gas so that H or Cl at the end is fluorinated as illustrated in  FIG.  5 D . 
     In step S 207  of supplying the NH 3  gas while applying the RF power, NH 3  radicals are supplied into the processing container  1  and the substrate W is exposed to the NH 3  radicals so that (NH 4 ) 2 Si 2 F 6  as a reaction product is produced as illustrated in  FIG.  5 E . (NH 4 ) 2 Si 2 F 6  is sublimated and exhausted by the exhaust device  44 . 
     In this case, concentrations of the NH 3  radicals are different from each other in the opening portion  801 , the middle portion  802  and the inner portion  803  of the concave structure  800 . That is, the opening portion  801  has more NH 3  radicals than the middle portion  802  and the inner portion  803 . Therefore, the shoulder portion  811  of the SiN film  810  is etched more. As a result, an opening shape (e.g., a V-shape) in which the opening portion  801  widens may be obtained. Further, in the film forming process as a subsequent process, an easy-to-embed shape in which a film is easy to be embedded in the concave structure  800  may be obtained. Moreover, by controlling the supply of the NH 3  radicals in terms of the depth direction in the trench, it is possible to uniformly etch from the upper portion to the lower portion of the concave structure  800 , or to preferentially remove the upper portion. 
       FIG.  6    is one example of a graph illustrating a relationship between the number of cycles and an etching amount in the etching process of the second example. As illustrated in  FIG.  6   , the etching amount increases with an increase in the number of cycles. In other words, the etching amount may be controlled with high precision by the number of cycles. Specifically, an etching rate of about 0.3 to 1.0 Å per cycle may be obtained. 
     &lt;Etching Process of Third Example&gt; 
       FIG.  7    is one example of a time chart illustrating an etching process of a third example performed by the substrate processing apparatus  100 . Here, the substrate processing apparatus  100  etches the SiN film formed on the substrate W. 
     In the etching process of the third example, a HF gas is supplied as an etchant gas from the gas supply pipe  21 , an Ar gas is supplied as a processing gas from the gas supply pipe  23 , and a N 2  gas is supplied as a carrier gas from the gas supply pipe  24 . In addition, the processing gas supplied from the gas supply pipe  23  is not limited to the Ar gas, but may be a reducing gas containing hydrogen and deuterium, for example, ammonia compounds, hydrazine compounds, or the like. These gases may be in a state of being mixed with an inert gas such as Ar or the like. Further, in the substrate processing apparatus  100  that performs the etching process of the third example, the gas supply pipe  22  may be omitted. 
     The etching process illustrated in  FIG.  7    is a process of etching a SiN film formed on the substrate W by repeating, a predetermined number of times, a cycle including step S 301  of supplying the HF gas, step S 302  of performing a purging process, step S 303  of supplying the Ar gas while applying RF power, and step S 304  of performing the purging process. Further, in  FIG.  7   , only one cycle is illustrated. Moreover, in steps S 301  to S 304 , a N 2  gas which is a purge gas is supplied constantly (continuously) from the gas supply pipe  24  during the etching process. 
     Step S 301  of supplying the HF gas is a step of supplying the HF gas into the processing container  1 . In step S 301  of supplying the HF gas, the HF gas is supplied into the processing container  1  from the gas source  21   a  via the gas supply pipe  21  by opening the on-off valve  21   c.    
     Step S 302  of performing the purging process is a step of purging the excess HF gas or the like inside the processing container  1 . In step S 302  of performing the purging process, the on-off valve  21   c  is closed to stop the supply of the HF gas. As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess HF gas and the like inside the processing container  1 . 
     Step S 303  of supplying the Ar gas while applying the RF power is a step of supplying radicals of the Ar gas. In step S 303 , the Ar gas is supplied from the gas source  23   a  inward of the plasma partition wall  32  via the gas supply pipe  23  by opening the on-off valve  23   c . Further, RF is applied to the plasma electrodes  33  by the radio-frequency power supply  35  to generate plasma inside the plasma partition wall  32 . The radicals of the Ar gas are generated and supplied into the processing container  1  via the opening  31 . 
     Step S 304  of performing the purging process is a step of purging the excess Ar gas, reaction products, or the like inside the processing container  1 . In step S 304  of performing the purging process, the on-off valve  23   c  is closed to stop the supply of the Ar gas. Further, the application of RF to the plasma electrodes  33  by the radio-frequency power supply  35  is stopped to stop the generation of plasma inside the plasma partition wall  32 . As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess Ar gas, the reaction products, or the like inside the processing container  1 . 
     By repeating the above cycle, the SiN film formed on the substrate W is etched. 
     In this case, preferable ranges of etching conditions used in the etching process of the third example are as follows. 
     Temperature: 250 to 630 degrees C. 
     Pressure: 0.1 to 10 Torr 
     Flow rate of HF gas: 500 to 5,000 sccm 
     Flow rate of Ar gas: 500 to 5,000 sccm 
     Flow rate of N 2  gas: 50 to 5,000 sccm 
     Time period of step S 301 : 5 to 60 seconds 
     Time period of step S 302 : 5 to 30 seconds 
     Time period of step S 303 : 5 to 30 seconds 
     Time period of step S 304 : 5 to 30 seconds 
     RF power: 50 to 500 W 
     The etching process of the third example will be further described. 
     In step S 301  of supplying the HF gas, the HF gas is supplied into the processing container  1  and the substrate W is exposed to the HF gas so that NH groups existing on the surface of the substrate W are fluorinated. 
     In step S 303  of supplying the Ar gas while applying the RF power, Ar radicals are supplied into the processing container  1  and the substrate W is exposed to the AR radicals so that the Ar radicals collide (attack) with the surface of the SiN film to produce reaction products such as SiF 4 . The reaction products are discharged from the interior of the processing container  1  by the exhaust device  44 . The SiN film  810  is etched by obtaining energy from Ar radicals or hydrogen radicals activated on the surface of the fluorinated SiN or SiO 2  film. 
     Here, in the etching process of the third example, many collisions may occur at the opening portion  801  rather than the middle portion  802  and the inner portion  803  of the concave structure  800 . Therefore, the shoulder portion  811  of the SiN film  810  is etched more. As a result, an opening shape (e.g., a V-shape) in which the opening portion  801  widens may be obtained. Further, in a film forming process as a subsequent process, an easy-to-embed shape in which a film is easy to be embedded in the concave structure  800  may be obtained. 
       FIG.  8    is one example of a graph illustrating a relationship between the number of cycles and an etching amount in the etching process of the third example. In addition, in  FIG.  8   , there are illustrated examples of a SiN film and a SiO 2  film as films to be etched. As illustrated in  FIG.  8   , the etching amount increases with an increase in the number of cycles. In other words, the etching amount may be controlled with high precision by the number of cycles. 
     &lt;Film Forming Process&gt; 
     Next, a film forming process performed by the substrate processing apparatus  100  will be described with reference to  FIG.  9   .  FIG.  9    is one example of a flowchart illustrating one example of the film forming process performed by the substrate processing apparatus  100 . Here, the substrate processing apparatus  100  embeds a SiN film in the substrate W in which a concave structure such as a trench is formed. 
     In step S 401 , the SiN film is formed on the substrate W in which the concave structure such as a trench is formed (in a first film forming process). 
     In step S 402 , the SiN film formed on the substrate W is etched (in an etching process). In addition, the etching processes of the first to third examples described above may be used in the etching process S 402 . As a result, an opening shape (e.g., a V-shape) in which the opening portion widens may be obtained. Further, in a film forming process as a subsequent process an easy-to-embed shape in which a film is easy to be embedded in the concave structure. 
     In step S 403 , a SiN film is formed on the substrate W which has been subjected to the etching process (in a second film forming process). 
     &lt;Film Forming Process&gt; 
     The film forming processes performed in steps S 401  and S 403  will be further described with reference to  FIG.  10   .  FIG.  10    is one example of a time chart illustrating the film forming process performed by the substrate processing apparatus  100 . Here, the substrate processing apparatus  100  forms the SiN film on the substrate W. 
     In each film forming process, the DCS gas is supplied as a processing gas from the gas supply pipe  22 , the NH 3  gas is supplied as a processing gas from the gas supply pipe  23 , and the N 2  gas is supplied as a carrier gas from the gas supply pipe  24 . In addition, the processing gas supplied from the gas supply pipe  22  is not limited to the DCS gas, but may be HCDS (hexachlorodisilane), halogenated silanes such as fluorine, bromine, iodine and the like, higher-order silanes, aminosilane compounds, silylamines, or the like. Further, the processing gas supplied from the gas supply pipe  23  is not limited to the NH 3  gas, but may be nitrogen or a mixed gas of nitrogen and hydrogen and argon, helium, or the like, a nitrogen-containing compound such as a hydrazine compound, or the like. Moreover, in the substrate processing apparatus  100  that performs the film forming process, the gas supply pipe  21  may be omitted. 
     The etching process illustrated in  FIG.  10    is a process of forming the SiN film formed on the substrate W by repeating, a predetermined number of times, a cycle including step S 501  of supplying a DCS gas, step S 502  of performing a purging process, step S 503  of supplying a NH 3  gas while applying RF power, and step S 504  of performing the purging process. Further, in  FIG.  10   , only one cycle is illustrated. Moreover, in steps S 501  to S 504 , a N 2  gas as a purge gas is supplied constantly (continuously) from the gas supply pipe  24  during the etching process. 
     Step S 501  of supplying the DCS gas is a step of supplying the DCS gas into the processing container  1 . In step S 501  of supplying the DCS gas, the DCS gas is supplied into the processing container  1  from the gas source  22   a  via the gas supply pipe  22  by opening the on-off valve  22   c.    
     Step S 502  of performing the purging process is a step of purging the excess DCS gas or the like inside the processing container  1 . In step S 502  of performing the purging process, the on-off valve  22   c  is closed to stop the supply of the DCS gas. As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess DCS gas and the like inside the processing container  1 . 
     Step S 503  of supplying the NH 3  gas while applying the RF power is a step of supplying radicals of the NH 3  gas. In step S 503 , the NH 3  gas is supplied inward of the plasma partition wall  32  from the gas source  23   a  via the gas supply pipe  23  by opening the on-off valve  23   c . Further, RF is applied to the plasma electrodes  33  by the radio-frequency power supply  35  to generate plasma inside the plasma partition wall  32 . The radicals of the NH 3  gas are generated and supplied into the processing container  1  via the opening  31 . 
     Step S 504  of performing the purging process is a step of purging the excess NH 3  gas or the like inside the processing container  1 . In step S 504  of performing the purging process, the on-off valve  23   c  is closed to stop the supply of the NH 3  gas. Further, the application of RF to the plasma electrodes  33  by the radio-frequency power supply  35  is stopped to stop the generation of plasma inside the plasma partition wall  32 . As a result, the purge gas supplied constantly from the gas supply pipe  24  purges the excess NH 3  gas or the like inside the processing container  1 . 
     By repeating the above cycle, the SiN film is formed on the substrate W. 
     In this case, preferable ranges of conditions of the film forming process are as follows. In addition, process conditions of the first film forming process S 401  and the second film forming process S 403  may be changed as appropriate as long as they are within the following preferable ranges. For example, the process conditions of the first film forming process S 401  and the second film forming process S 403  may be the same or different from each other. The first film forming process, the etching process, and the second film forming process may be repeated until a desired film formation amount or shape is obtained. When a film forming temperature is 550 degrees C. or higher, a film may be formed with a thermally-activated NH 3  gas without applying RF at the time of supplying the NH 3  gas. 
     Temperature: 250 to 630 degrees C. 
     Pressure: 0.1 to 9 Torr 
     Flow rate of DCS gas: 500 to 5,000 sccm 
     Flow rate of NH 3  gas: 500 to 10,000 sccm 
     Flow rate of N 2  gas: 50 to 5,000 sccm 
     Time period of step S 501 : 2 to 30 seconds 
     Time period of step S 502 : 5 to 30 seconds 
     Time period of step S 503 : 5 to 60 seconds 
     Time period of step S 504 : 5 to 30 seconds 
     RF power: 0 to 500 W 
     With the substrate processing apparatus  100  according to the present embodiment, it is possible to improve the property of the embedding of the SiN film in the concave structure such as a trench. That is, a conformal SiN film may be formed in the first film forming process of step S 401 , and the opening shape (e.g., a V-shape) in which the opening portion widens may be obtained in the etching process of step S 402 . As a result, it is possible to suppress the occurrence of voids when embedding the SiN film in the second film forming process of step S 403 , which is a subsequent process. 
     Further, with the substrate processing apparatus  100  according to the present embodiment, the first film forming process of step S 401 , the etching process of step S 402 , and the second film forming process of step S 403  may be performed in-situ (within the same processing container  1 ). This makes it possible to improve productivity. In addition, it is possible to suppress a native oxide film at an interface between the SiN film formed in the first film forming process of step S 401  and the SiN film formed in the second film forming process of step S 403 . Moreover, a configuration in which the first film forming process of step S 401 , the etching process of step S 402 , and the second film forming process of step S 403  are performed ex-situ, may be employed. 
     In addition, according to the etching processes of the first to third examples, the etching process may be performed in the temperature range of the film forming process. That is, a film forming temperature during the first film forming process of step S 401  and an etching temperature during the etching process of step S 402  may be identical to each other or within a predetermined temperature range (e.g., a temperature difference between the film forming temperature and the etching temperature may be within 50 degrees C.). Further, a film forming temperature during the second film forming process of step S 403  and the etching temperature during the etching process of step S 402  may be identical to each other or within a predetermined temperature range (e.g., a temperature difference between the film forming temperature and the etching temperature may be within 50 degrees C.). 
     As a result, the temperature during the film forming process of the SiN film illustrated in  FIG.  9    may be maintained constant or in the predetermined temperature range. Thus, it is possible to suppress the generation of particles due to an increase or decrease of the temperature. Further, it is possible to shorten a temperature adjustment time period from after the end of the first film forming process of step S 401  to before the start of the etching process of step S 402 . Moreover, it is possible to shorten a temperature adjustment time period from after the end of the etching process of step S 402  to before the start of the second film forming process of step S 403 . This makes it possible to shorten a processing time period of the entire process. 
     In addition, since the temperature adjustment time period between the film forming process and the etching process can be shortened, it is possible to suppress an increase in the processing time period of the entire process even if the number of repetitions of the film forming process and the etching process is increased. Moreover, by increasing the number of repetitions of the film forming process and the etching process, it is possible to further suppress the occurrence of voids when embedding the SiN film. 
     Although the substrate processing by the substrate processing apparatus  100  has been described above, the present disclosure is not limited to the above embodiments and the like, and various modifications and improvements may be made within the scope of the gist of the present disclosure set forth in the claims. 
     As an example, the apparatus of the present disclosure may be a single-type substrate processing apparatus that processes one sheet of substrate, a batch-type substrate processing apparatus that simultaneously processes plural sheets of (e.g., four) substrates on the same plane, and a carousel-type substrate processing apparatus that processes plural sheets of (e.g., five) substrates while rotating the substrates. 
     The first film forming process of step S 401  and the second film forming process of step S 403  is not limited to those illustrated in  FIG.  10   , but may be film forming processes of forming other SiN films. 
     In addition, the etching process of step S 402  is not limited to the etching processes of the first to third examples, but may be other etching process, for example, an etching process to be described later. 
     &lt;Etching Process of Fourth Example&gt; 
     Here, an etching process of a fourth example performed by the substrate processing apparatus  100  will be described with reference to  FIG.  11   .  FIG.  11    is one example of a time chart illustrating the etching process of the fourth example performed by the substrate processing apparatus  100 . Here, the substrate processing apparatus  100  etches a SiN film formed on the substrate W. 
     In the etching process of the fourth example, a HF gas is supplied as an etchant gas from the gas supply pipe  21 , a NH 3  gas is supplied as a processing gas from the gas supply pipe  22 , and a N 2  gas is supplied as a carrier gas from the gas supply pipe  24 . In addition, the processing gas supplied from the gas supply pipe  22  is not limited to the NH 3  gas, but may be H 2 , D 2 , ND 3 , amines, a hydrazine compound, a halogen compound, a mixed gas of hydrocarbon and an inert gas such as Ar or He, or the like. Further, in the substrate processing apparatus  100  that performs the etching process of the fourth example, the gas supply pipe  23  and the plasma generation mechanism  30  may be omitted. 
     In this case, preferable ranges of etching conditions of the SiN film in the etching process of the fourth example are as follows. 
     Temperature: 250 to 630 degrees C. 
     Pressure: 0.1 to 150 Torr 
     Flow rate of HF gas: 50 to 5,000 sccm 
     Flow rate of NH 3  gas: 50 to 10,000 sccm 
     Flow rate of N 2  gas: 50 to 5,000 sccm 
     The etching process (step S 402 ) in the film forming process illustrated in  FIG.  9    may be performed by the etching process of the fourth example illustrated in  FIG.  11   . Also in this configuration, the first film forming process of step S 401 , the etching process of step S 402 , and the second film forming process of step S 403  may be performed in-situ. Further, the etching process may be performed in the temperature range of the film forming process. 
     In addition, this application claims the priority from Japanese Patent Application No. 2020-53329 filed on Mar. 24, 2020, the disclosure of which is incorporated herein in its entirety by reference. 
     EXPLANATION OF REFERENCE NUMERALS 
     W: substrate,  100 : substrate processing apparatus,  1 : processing container,  2 : ceiling plate,  20 : gas supplier,  21  to  24 : gas supply pipes,  21   a  to  23   a : gas sources,  30 : plasma generation mechanism,  44 : exhaust device,  50 : heating mechanism,  60 : controller