JP2012062549A - Film deposition device and film deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop film deposition reaction in an extreme short period of time and suppress overshoot.SOLUTION: The film deposition device includes: a first chamber 3 where a substrate 10 is stored; a supply line for supplying a medium, in which a film deposition material is mixed in a supercritical state, onto the first chamber 3; a stage 9 for holding the substrate 10 in the first chamber 3; a second chamber 4 for decompressing the pressure inside the first chamber 3 to lower pressure than the critical pressure of the medium; a pipe 7a for connecting the first chamber 3 and the second chamber 4; and a valve 7b provided in the pipe 7a.

Description

  The present invention relates to a film forming apparatus and a film forming method for forming a predetermined film on a substrate.

  In the manufacture of a semiconductor device, a thin film having a predetermined function is formed on a ground surface that has been finely processed. Conventionally, a film forming method such as a CVD (Chemical Vapor Deposition) method is used for forming a thin film.

  However, with the recent miniaturization and higher performance of semiconductor devices, there is a demand for films that are difficult to form by conventional film formation methods. For example, formation of an insulating film having a high dielectric constant and formation of a film on a base surface having a three-dimensional structure are required. In order to meet such a demand, a film forming method using a supercritical fluid has been studied.

  For example, Patent Document 1 describes a film forming method in which a supercritical fluid in which a film forming material is dissolved is sprayed from a nozzle to rapidly reduce the pressure to near atmospheric pressure. In such a film forming method, the supercritical fluid is rapidly depressurized, so that the film forming material dissolved in the supercritical fluid is deposited and deposited to form a film.

  In Patent Document 2, a supercritical fluid is used for transporting a film forming material into the film forming chamber. In the film forming chamber, a film is deposited by a reaction of a CVD method, that is, by thermal decomposition and heat reaction of the film forming material. The method of doing is described.

JP 2008-300781 A JP 2006-120713 A

  In the film forming method described in Patent Document 1, it is possible to form a relatively thick film having a film thickness of about 1 μm to several tens of μm. However, it is impossible to form a thin film having a film thickness of 100 nm or less uniformly. It was difficult. For example, in a generation DRAM after the design rule of 50 nm, a high dielectric film having a film thickness of about 6 to 10 nm is required as a capacitor insulating film of a capacitor constituting a memory cell. Furthermore, it is also required to form the high dielectric film uniformly on the electrode having a three-dimensional structure. However, it has been difficult to accurately form the above-described thin film by a film forming method in which a supercritical fluid in which a film forming material is dissolved is sprayed from a nozzle.

  Here, the supercritical fluid is excellent in the solubility of the film forming material and the permeability to fine portions. Therefore, according to the film forming method described in Patent Document 2, it is possible to form a uniform film on the base surface having a three-dimensional complicated structure. When a film is formed by thermal decomposition and thermal reaction of the film forming material, the film forming reaction is stopped when the film thickness reaches a predetermined thickness. In order to stop the film formation reaction, it is common to stop the heating of the substrate or stop the supply of the film forming raw material. However, even if heating means such as a heater is stopped, the temperature of the substrate does not drop rapidly. Similarly, even if the supply of the film forming material is stopped, the concentration of the material in the film forming chamber does not decrease rapidly. Accordingly, even after the film formation reaction is stopped, an overshoot phenomenon occurs in which the film formation reaction proceeds for a while. Therefore, conventionally, film formation is controlled in anticipation of overshoot of the film formation reaction. However, the film thickness deposited during the overshoot period is not always constant. This is because the method of decreasing the concentration of the film forming material and the method of decreasing the substrate temperature are strongly influenced by various film forming parameters such as a change with time in the film forming chamber, the pressure and supply speed of the supercritical fluid. For this reason, it is not easy to perform strict film thickness control with good reproducibility in consideration of various parameters. For example, when an extremely thin film having a film thickness of 10 nm or less is formed, it is necessary to control the film thickness at a level of 1 nm or less. However, in the conventional film forming method, since it is necessary to perform control in consideration of an overshoot, it is difficult to control the film thickness with high accuracy.

  In the film forming method of the present invention, a film forming raw material is transferred into a film forming chamber using a medium in a supercritical state, and when a film with a predetermined film thickness is formed, the film forming chamber is decompressed to form a film. The membrane reaction is stopped. If the film formation reaction is stopped in this manner, the film formation reaction is stopped in an extremely short time, and overshoot is suppressed.

  The film forming apparatus of the present invention has a second chamber for depressurizing the inside of the chamber in addition to the film forming chamber.

  Since overshoot at the time of film formation using a medium in a supercritical state is suppressed, the film thickness can be easily controlled. Thereby, a highly accurate film can be formed.

It is a schematic diagram which shows an example of a structure of the film-forming apparatus of this invention. It is a figure which shows an example of the relationship between the film-forming time at the time of forming a silicon oxide film, and a film thickness. It is a schematic diagram which shows the flow of the supercritical fluid in each process of the film-forming method. It is a figure which shows the calculated value of the pressure change before and behind opening of the valve | bulb between a film-forming chamber and a pressure release chamber. (A) is a figure which shows the change of the raw material density | concentration in the film-forming chamber and film-forming speed | rate in the conventional film-forming method, (b) is the raw material density | concentration in the film-forming chamber and film-forming speed | rate in the film-forming method of this invention. It is a figure which shows a change. (A) is a figure which shows the structure by which the film-forming chamber and the collection | recovery tank were connected via the back pressure regulator, (b) is a film release chamber and a collection | recovery tank, a pressure release chamber and a back pressure regulator. It is a figure which shows the structure connected through this. It is a schematic diagram which shows one of the modifications of the film-forming chamber. It is a typical sectional view showing the structure of a stage.

  Next, a first embodiment of the film forming apparatus of the present invention will be described. FIG. 1 shows a configuration of a film forming apparatus according to this embodiment. The illustrated film forming apparatus includes a film forming chamber 3, a pressure release chamber 4, a pipe 7 a (first pipe) connecting the film forming chamber 3 and the pressure release chamber 4, and a valve 7 b ( A first valve).

  The film formation chamber 3 and the pressure release chamber 4 are stainless steel high-pressure containers that can withstand a pressure of 20 MPa or more. A pipe 7a connecting the film forming chamber 3 and the pressure release chamber 4 is a stainless steel pipe having a large diameter (1 inch or more). A valve 7b provided in the middle of the pipe 7a can be opened and closed instantaneously in response to a control signal from a control means (computer or the like) not shown.

  A stage 9 with a built-in heater is provided in the film forming chamber 3, and a semiconductor substrate 10 as a film forming target is fixed to the stage 9. The semiconductor substrate 10 is fixed to the stage 9 so that the surface (processing surface) on which the film is formed faces downward.

  An example of a specific configuration of the stage 9 is shown in FIG. The stage 9 includes a substrate holding part 15 and a heat insulating member 16. The substrate holding part 15 is formed of metal, and heating means such as a heater 17 is incorporated inside. The heater 17 is, for example, a heating wire, and heats the substrate holding unit 15. The substrate holding unit 15 is provided with temperature detection means (for example, thermocouple wiring) not shown. The semiconductor substrate 10 is maintained at a predetermined temperature by controlling the power supplied to the heater 17 based on the detection result of the temperature detection means.

  Inside the heat insulating member 16, a cooling tube 18 is provided so as to surround the upper surface and the side surface of the substrate holding portion 15. By circulating a cooling medium such as water in the cooling tube 18, the propagation of the heat of the heater 17 to the film forming chamber 3 is suppressed.

  The cooling tube 18 is used to suppress the heat of the stage 9 from propagating to the outside. In other words, it is not used for rapidly cooling the semiconductor substrate 10 when the film formation reaction is stopped. With the recent increase in size of semiconductor substrates, the stage has also increased in size. As a result, the heat capacity of the substrate holder 15 is also increasing, and it is difficult to rapidly cool the semiconductor substrate using the cooling tube 18.

  As a method for fixing the semiconductor substrate 10 to the substrate holding part 15, in addition to a mechanical fixing means using a hook or the like, a method of closely fixing the semiconductor substrate 10 to the surface of the substrate holding part 15 using static electricity is used. Also good.

  Refer to FIG. 1 again. The film forming apparatus according to this embodiment is provided with two raw material supply lines. One raw material supply line includes a medium supply facility 11a, a liquid feed pump 1a, a heat exchanger 2a, a film forming raw material supplier 12a, and a valve 6a. The medium supply facility 11a supplies a medium (liquid) that is a source of the supercritical fluid. The liquid supplied from the medium supply equipment 11a is sent to the heat exchanger 2a by the liquid feed pump 1b, and is heated by the heat exchanger 2a to become a supercritical fluid. The first film-forming raw material supplied from the film-forming raw material supply device 12a is mixed (dissolved) with the supercritical liquid thus produced. Then, a supercritical liquid mixed with the first film forming raw material is supplied to the film forming chamber 3.

  The other raw material supply line has the same configuration. That is, it is comprised from the medium supply equipment 11b, the liquid feeding pump 1b, the heat exchanger 2b, the film-forming raw material supply device 12b, and the valve 6b. The medium (liquid) supplied from the medium supply facility 11b is heated by the heat exchanger 2b to become a supercritical fluid, and the second film forming raw material supplied from the film forming raw material supply device 12b is mixed with the supercritical liquid. (Dissolved). Then, a supercritical liquid in which the second film forming raw material is mixed is supplied to the film forming chamber 3.

  When film formation is performed using three or more kinds of film forming raw materials, three or more raw material supply lines similar to the above may be provided. The plurality of raw material supply lines need not all have the same structure, and the structure of the supply line may be changed as appropriate according to the characteristics of the raw material to be supplied.

  The film formation chamber 3 and the pressure release chamber 4 are connected to a back pressure regulator 5 via a plurality of pipes each provided with a valve. The back pressure regulator 5 is recovered via a heat exchanger 21. Connected to the tank 20. The collection tank 20 is used for collecting film forming raw materials remaining after the film formation and by-products generated by the film formation reaction. Specifically, the pressure release chamber 4 is connected to the back pressure regulator 5 via a pipe 80a (second pipe) provided with a valve 80b (second valve). The film forming chamber 3 is connected to the back pressure regulator 5 via a pipe 81a (third pipe) provided with a valve 81b (third valve). Furthermore, the film forming chamber 3 and the pressure release chamber 4 are connected to each other via a pipe 82a (fourth pipe) provided with a valve 82b (fourth valve).

  In addition, stainless steel piping is used for piping of each raw material supply line. Also, stainless steel pipes are used for the pipes 80a, 81a, and 82a. However, the pipes of the raw material supply lines and the pipes 80a, 81a, 82a are all smaller in diameter than the pipe 7a.

Next, a first embodiment of the film forming method of the present invention will be described. In the present embodiment, a case where carbon dioxide (CO ₂ ) is used as a supercritical fluid and a silicon oxide film (SiO ₂ ) is formed on the semiconductor substrate 10 will be specifically described.

  Carbon dioxide is known to enter a supercritical state at temperatures above the critical temperature and pressures above the critical pressure. Carbon dioxide has a critical temperature Tc of 31.1 ° C. and a critical pressure Pc of 7.38 MPa.

  Liquid medium carbon dioxide cylinders are used as the medium supply facilities 11a and 11b shown in FIG. You may supply what was changed into the liquid state by cooling gaseous carbon dioxide to 0 degreeC with a cooler.

As the film forming raw material, vaporized TEOS gas (Tetraethoxysilane) and oxygen gas (O ₂ ) can be used.

  A semiconductor substrate 10 is fixed on the stage 9 in the film forming chamber 3. At this time, it fixes so that the process surface of the semiconductor substrate 10 may face downward. Further, the valve 7 between the film forming chamber 3 and the pressure release chamber 4 is closed.

  Next, carbon dioxide in a supercritical state is supplied into the film forming chamber 3 set at a predetermined pressure (10 MPa in this embodiment). The temperature of carbon dioxide at this time is set to a temperature (100 ° C. in this embodiment) that is not lower than the critical temperature and sufficiently lower than the film formation reaction temperature. In the film forming chamber 3, the supercritical state of carbon dioxide is maintained. At this time, the film forming raw material is not supplied.

  Subsequently, the semiconductor substrate 10 is heated by the heater 17 (FIG. 8), and the temperature of the semiconductor substrate 10 is raised to a predetermined temperature (300 ° C. in this embodiment) at which the film formation reaction occurs.

  After the conditions necessary for the film-forming reaction are achieved, the film-forming raw materials (TEOS and oxygen) are mixed with carbon dioxide in the supercritical state from the film-forming raw material feeders 12a and 12b, respectively. Thereby, the supercritical carbon dioxide mixed with the film forming material is supplied into the film forming chamber 3.

  On the surface of the heated semiconductor substrate 10, thermal decomposition of the supplied TEOS and reaction with oxygen occur, and a silicon oxide film is deposited on the surface of the semiconductor substrate 10. FIG. 2 shows an example of the relationship between the film formation time and the film thickness when forming the silicon oxide film. In this embodiment, the silicon oxide film having a thickness of about 5 nm can be deposited by continuing the supply of the film forming material for 6 minutes. Since the relationship between the film formation time and the film thickness changes depending on the film formation temperature and the supply rate of the film formation raw material, the above relationship is investigated in advance according to the film formation conditions to be used.

  When the silicon oxide film reaches a predetermined film thickness, the heating reaction by the heater 17, the supply of the film forming raw material, and the rapid depressurization of carbon dioxide in the supercritical state are simultaneously performed to stop the film forming reaction. Rapid decompression is performed by opening the valve 7 shown in FIG.

FIG. 3 shows the flow of supercritical fluid (CO ₂ ) in each step of the film forming method of the present invention. FIG. 3A shows the flow of the supercritical fluid during the film forming process. FIG. 3B shows the flow of the supercritical fluid during the rapid decompression process. FIG. 3C shows the flow of the supercritical fluid during the raw material discharge process. In addition, the thick line in each figure has shown the passage route of the supercritical fluid.

  During the film formation reaction, the supercritical liquid flows from the discharge port (not shown) provided in the upper part of the film formation chamber 3 to the back pressure regulator 5 (FIG. 3a). The supercritical liquid that has passed through the back pressure regulator 5 is collected in a recovery tank 20 shown in FIG. The valve 8 on the path where the supercritical fluid is not flowing is closed.

  At the time of rapid decompression, the discharge port provided in the upper part of the film forming chamber 3 is closed and the valve 7 is opened. As a result, the supercritical fluid is discharged into the pressure release chamber 4 through the large-diameter pipe at once. Here, the pressure in the pressure release chamber 4 is previously maintained in the range from atmospheric pressure (about 0.1 MPa) to about 4 MPa. Then, when the valve 7 between the film forming chamber 3 and the pressure release chamber 4 is opened, the pressure in the film forming chamber 3 is rapidly reduced to a critical pressure of supercritical fluid (7.38 MPa in the case of carbon dioxide) or less. The In this embodiment, the pressure in the pressure release chamber 4 before opening the valve 7 is atmospheric pressure. A specific calculated value of the pressure change is shown in FIG.

  In the calculation, the volume of the film forming chamber 3 was 10 L (liter), and the volume of the pressure release chamber 4 was 7 L. The pressure release chamber 4 is maintained at atmospheric pressure (0.1 MPa) before the valve 7 is opened. In the calculation, for simplification, the temperature decrease due to adiabatic expansion of carbon dioxide and the temperature increase due to heater heating near the semiconductor substrate are not taken into account. small).

  As shown in FIG. 4, by opening the valve 7 and connecting the pressure release chamber 4 to the film forming chamber 3, the pressure in the film forming chamber 3 rapidly decreases to 6.6 MPa. Due to the connection of the pressure release chamber 4 to the film formation chamber 3, the carbon dioxide that has become the critical pressure (7.38 MPa) or less changes to carbon dioxide gas in a gaseous state.

  The medium that is no longer in the supercritical state (in this embodiment, carbon dioxide gas) has a markedly reduced ability to dissolve the film forming raw material. As a result, rapid deposition of the film forming material (TEOS in this embodiment) occurs. The deposited film forming material settles down to the bottom of the film forming chamber 3. Thereby, the density | concentration of the film-forming raw material in the film-forming chamber 3 decreases rapidly, and the film-forming reaction stops instantaneously.

  The semiconductor substrate 10 is held on the upper part of the film forming chamber 3. Therefore, adhesion of the deposited film forming material to the semiconductor substrate 10 is avoided. In particular, since the semiconductor substrate 10 is held with its processing surface facing downward, deposition of deposited film forming material on the processing surface of the semiconductor substrate 10 is avoided.

  FIG. 5A schematically shows changes in the raw material concentration and the film forming speed in the film forming chamber in the conventional film forming method. On the other hand, FIG. 5B schematically shows changes in the raw material concentration and the deposition rate in the deposition chamber in the deposition method of the present invention.

  As shown in FIG. 5A, in the conventional method, even if the supply of the raw material is stopped, the concentration of the raw material in the film forming chamber does not rapidly decrease but slowly decreases. Further, even when the heater heating is stopped, the surface temperature of the semiconductor substrate does not rapidly decrease. For this reason, even if the supply of the film forming material is stopped and the heater heating is stopped simultaneously, the film forming speed does not become zero, and the film forming reaction continues (overshoot state).

  On the other hand, as shown in FIG. 5B, in the film forming method of the present invention, it is possible to rapidly bring the concentration of the film forming material near the surface of the semiconductor substrate close to zero by utilizing the deposition of the film forming material. Become. As a result, the film formation reaction can be stopped instantaneously without causing film formation overshoot.

  When the film formation reaction is stopped and the temperature of the semiconductor substrate 10 is lower than the film formation reaction temperature, it is supercritical into the film formation chamber 3 and the pressure release chamber 4 through the path shown in FIG. Supply the state carbon dioxide again. Thereby, the inside of the film forming chamber 3 and the pressure release chamber 4 is raised to a predetermined pressure (10 MPa in this embodiment) that is equal to or higher than the critical pressure. The temperature of the supercritical carbon dioxide supplied at this time is set to 100 ° C. as before the start of film formation. This temperature is sufficiently lower than the film formation reaction temperature. At this time, the heater 17 (FIG. 1) is stopped. Therefore, even if the inside of the film forming chamber 3 returns to the supercritical state and the film forming raw material deposited and settled is dissolved again in the supercritical fluid, the film forming reaction is not resumed on the surface of the semiconductor substrate.

  The dissolved film forming raw material is discharged to the collection tank 20 shown in FIG. 1 through the route shown in FIG. After the film forming material discharging step is completed, the film forming chamber 3 is decompressed to atmospheric pressure, and the semiconductor substrate 10 is taken out. Thus, the film forming process is completed.

The pressure release chamber, which is a feature of the film forming apparatus of the present invention, plays the following two roles in controlling the film thickness using rapid decompression.
(1) Control the pressure after rapid decompression.
(2) Avoid damage to the device due to rapid decompression.

  The pressure control (1) will be specifically described. In a conventional film forming apparatus, a back pressure regulator is used for reducing the pressure in the film forming chamber. However, in a film deposition system using a supercritical fluid, it is necessary to control the discharge and stoppage of the supercritical fluid with a valve, so the flow path in the back pressure regulator is narrow and a rapid pressure drop must be realized. It is difficult. This is because a back pressure regulator for a supercritical fluid adjusts the pressure by continuing to discharge the supercritical fluid at a relatively slow flow rate for a certain period of time.

  On the other hand, in the present invention in which a pressure release chamber is used for decompression in the film formation chamber, the pressure after decompression is the volume difference between the film formation chamber and the pressure release chamber and before the pressure release between the film formation chamber and the pressure release chamber. Automatically determined by the internal pressure difference. Therefore, rapid decompression can be achieved by simply opening the valve between both chambers. Thereby, in this invention, it becomes possible to stop the film-forming reaction in an instant.

  The damage of the device (2) will be specifically described. What is concerned about rapid decompression is the freezing of piping and related parts (such as valves and seal rings inside the back pressure regulator) due to adiabatic cooling (cooling due to adiabatic expansion of carbon dioxide) associated with rapid decompression. is there. Specifically, it is assumed that carbon dioxide flowing in the piping becomes dry ice and clogs, or plastic parts such as a seal ring are frozen and broken.

  Here, as shown in FIG. 6A, when carbon dioxide (for example, pressure 10 MPa) in the film forming chamber is exhausted to the outside (recovery tank) through the back pressure regulator as it is, Immediately after passing through the back pressure regulator, the pressure is reduced to atmospheric pressure (about 0.1 MPa) at a stretch. Thereby, adiabatic cooling occurs in the vicinity of the back pressure regulator, and freezing occurs. Furthermore, the freezing region gradually expands while carbon dioxide is being discharged, and eventually the piping and related parts are completely frozen.

  On the other hand, when the pressure is reduced through the pressure release chamber as shown in FIG. 6B, the film formation after the valve release is performed even if the pressure in the pressure release chamber before the valve release is in the atmospheric pressure state. The carbon dioxide pressure in the chamber does not drop to atmospheric pressure. That is, as shown in FIG. 4, the pressure in the film forming chamber after the valve is released only decreases to about 6.6 MPa, for example. For this reason, adiabatic cooling is suppressed. In addition, since the pressure reduction ends in an instant, the residual heat cooling does not continue for a long time. For this reason, it does not lead to freezing related parts, such as piping and a valve. Furthermore, when the carbon dioxide in the pressure release chamber is discharged to the recovery tank in the atmospheric pressure state, it is not necessary to suddenly reduce the pressure, so that adiabatic cooling can be avoided by gradually reducing the pressure.

  Further, by making the film forming chamber, the pressure release chamber, the piping, and the like made of stainless steel having a thickness capable of withstanding a sufficiently high pressure, physical damage caused by pressure change can be avoided.

  As described above, the structure in which the film forming chamber and the pressure release chamber are connected via the valve makes it possible to easily and safely carry out rapid decompression.

  As described above, according to the present invention, the film formation reaction can be rapidly stopped. As a result, film overshoot is avoided, the film thickness during film formation can be easily controlled, and a highly accurate film can be formed.

  There is no particular limitation on the type of supercritical fluid used in the film forming apparatus and the film forming method of the present invention, and it can be appropriately selected according to the characteristics of the film forming material. For example, water in a supercritical state (critical temperature Tc = 374 ° C., critical pressure Pc = 22 MPa) can be used.

The film forming method of the present invention can be applied in addition to the formation of a silicon oxide film. For example, a metal chelate compound is used as one film forming raw material, and oxygen, ozone, hydrogen, nitrogen, ammonia, water vapor, etc., which generate a film by reacting with the metal chelate compound etc. as the other film forming raw material. Can be used. Thereby, a film containing a metal, for example, a titanium oxide film (TiO ₂ ) or the like can be formed.

  Examples of metal chelate compounds used as a film forming raw material include bis (ethylcyclopentadienyl) ruthenium, tris (2,4-octadionato) ruthenium, pentakis (dimethylamino) tantalum, pentaethoxytantalum, tetra-t-butoxytitanium, Examples thereof include tetrakis (N-ethyl-N-methylamino) titanium, iridium acetylacetone, platinum acetylacetone and the like.

  The film forming chamber 3 shown in FIG. 1 and the like can be changed as shown in FIG. Two windows (an incident window 30a and a detection window 30b) are provided in the lower part of the film forming chamber 3 shown in FIG. Therefore, light can be incident into the film forming chamber 3 through the incident window 30a, and the light reflected by the semiconductor substrate 10 can be emitted from the detection window 30b. That is, the light reflected by the semiconductor substrate 10 can be monitored externally. Therefore, a measuring device 31 capable of measuring the thickness of the film on the semiconductor substrate using light, such as ellipsometry, can be arranged as shown in FIG. 7 to measure the thickness of the film on the semiconductor substrate. As a result, it is possible to determine the timing for stopping the film formation reaction while monitoring the actual film thickness during the film formation process.

  The entrance window 30a and the detection window 31b are made of sapphire having a thickness that can sufficiently withstand the pressure in the supercritical state.

DESCRIPTION OF SYMBOLS 3 Deposition chamber 4 Pressure release chamber 5 Back pressure regulator 7a Piping 7b Valve 9 Stage 10 Semiconductor substrate 80a, 81a, 82a Piping 80b, 81b, 82b Valve

Claims (11)

A film forming apparatus comprising: a first chamber that accommodates a substrate; and a supply line that supplies a supercritical medium mixed with film forming raw materials to the first chamber,
A stage that is provided in the first chamber and holds the substrate so that a film formation target surface of the substrate is vertically downward;
A second chamber for reducing the pressure in the first chamber to a pressure lower than the critical pressure of the medium;
A first pipe connecting the first chamber and the second chamber;
A film forming apparatus comprising: a first valve provided in the first pipe. A back pressure regulator connected to the second chamber via a second pipe;
A second valve provided in the second pipe,
The film forming apparatus according to claim 1, wherein a diameter of the first pipe is larger than a diameter of the second pipe. A third pipe connecting the first chamber and the back pressure regulator, and a third valve provided in the third pipe,
During film formation, the third valve is opened, the first valve and the second valve are closed,
3. The film forming apparatus according to claim 2, wherein at the time of decompression, the first valve is opened, and the second valve and the third valve are closed. A fourth pipe connecting the first chamber and the second chamber, and a fourth valve provided in the fourth pipe;
When the film forming raw material remaining in the first chamber is discharged after the film formation, the second valve and the fourth valve are opened, and the first valve and the third valve are opened. The film forming apparatus according to claim 3, wherein the valve is closed. Using a film forming apparatus including a first chamber, a second chamber, and a medium supply facility,
A first step of accommodating the substrate in the first chamber such that a film formation target surface of the substrate faces vertically downward;
A second step of supplying the medium from the supply equipment to the first chamber in a state in which the medium is in a supercritical state and set to a temperature higher than the critical temperature and lower than the film formation reaction temperature;
A third step of mixing a film forming raw material with the medium in a supercritical state supplied to the first chamber after raising the temperature of the substrate to a temperature at which a film forming reaction occurs or higher;
After the film having a predetermined thickness is formed on the film formation target surface, the heating of the substrate and the supply of the medium to the first chamber are stopped simultaneously with the first chamber and the second chamber. And a fourth step of reducing the pressure in the first chamber to a pressure lower than the critical pressure of the medium. Prior to execution of the fourth step, the first chamber is maintained at a pressure higher than atmospheric pressure,
The film forming method according to claim 5, wherein the pressure in the second chamber is set to an atmospheric pressure state. A fifth step of supplying again the medium having a temperature not lower than the critical temperature and lower than the film formation reaction temperature to the first chamber after the temperature of the substrate is lowered to a temperature lower than the temperature at which the film formation reaction occurs; ,
The film forming method according to claim 5, further comprising a sixth step of collecting the medium supplied to the first chamber through the second chamber.   The film forming method according to claim 5, wherein carbon dioxide is used as the medium. Using water as the medium,
The film forming method according to any one of claims 5 to 7, wherein, in the second step, the pressure in the first chamber is maintained at 22 MPa or more.   The film forming method according to claim 5, wherein a silicon oxide film is formed using TEOS gas and oxygen gas as the film forming material. The film forming raw material contains metal chelate compounds,
The film-forming method according to claim 5, wherein a film containing a metal contained in the metal chelate compound as a component is formed on the substrate.

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