Raw material supply apparatus and raw material supply method

A raw material supply apparatus according to an aspect of the present disclosure includes: a container configured to store a solution of a first solid raw material dissolved in a solvent or a dispersion system of the first solid raw material dispersed in a dispersion medium; a removal part configured to form a second solid raw material by removing the solvent or the dispersion medium from the solution or the dispersion system stored in the container; a detection part configured to detect a completion of a removal of the solvent or the dispersion medium from the solution or the dispersion system; and a heater configured to heat the second solid raw material.

This is a National Phase Application filed under 35 U.S.C. 371 as a national stage of PCT/JP2020/034971, filed Sep. 15, 2020, an application claiming the benefit of Japanese Application No. 2019-173420, filed Sep. 24, 2019, the content of each of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a raw material supply apparatus and a raw material supply method.

BACKGROUND

There is known a technique of confirming that a liquid raw material is filled to a position where the liquid raw material can be sprayed in a liquid raw material vaporization mechanism that vaporizes the liquid raw material through spraying when forming a thin film for a semiconductor element on a substrate surface by spraying and vaporizing the liquid raw material (see, for example, Patent Document 1).

PRIOR ART DOCUMENTS

Patent Documents

The present disclosure provides a technique capable of detecting that the separation of a solvent or a dispersion medium contained in a solution or a dispersion system from a solid raw material is completed.

SUMMARY

A raw material supply apparatus according to an aspect of the present disclosure includes: a container configured to store a solution of a first solid raw material dissolved in a solvent or a dispersion system of the first solid raw material dispersed in a dispersion medium; a removal part configured to form a second solid raw material by removing the solvent or the dispersion medium from the solution or the dispersion system stored in the container; a detection part configured to detect a completion of a removal of the solvent or the dispersion medium from the solution or the dispersion system; and a heater configured to heat the second solid raw material.

According to the present disclosure, it is possible to detect that the separation of a solvent or a dispersion medium contained in a solution or a dispersion system from a solid raw material is completed.

DETAILED DESCRIPTION

Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all of the accompanying drawings, the same or corresponding members or components will be denoted by the same or corresponding reference numerals, and redundant descriptions will be omitted.

Raw Material Supply System

TheFIG.1is a view illustrating an example of a raw material supply system. As illustrated inFIG.1, a raw material supply system1includes a raw material source10, a carrier gas source20, raw material supply apparatuses30and40, a processing apparatus50, and a controller90.

The raw material source10supplies a solution of a first solid raw material dissolved in a solvent or a slurry of a first solid raw material dispersed in a solvent (a dispersion medium) to the raw material supply apparatuses30and40. The form of the raw material source10is not particularly limited as long as the solution or the slurry M can be supplied to the raw material supply apparatuses30and40.

FIGS.2A to2Care views illustrating exemplary raw material sources10, which provide examples of configurations where the raw material source10supplies a solution of a first solid raw material dissolved in a solvent to the raw material supply apparatuses30and40are illustrated. As illustrated inFIG.2A, the raw material source10includes, for example, a tank11filled with a solution LS, a pipe12inserted into the tank11from above, and a valve13interposed in the pipe12. In the raw material source10illustrated inFIG.2A, the solution LS filled in the tank11is supplied from the pipe12under pressure by its own weight. In addition, as illustrated inFIG.2B, the raw material source10may include, for example, a tank11filled with a solution LS, pipes12and14inserted into the tank11from above, and valves13and15interposed in the pipes12and14. In the raw material source10illustrated inFIG.2B, by supplying an inert gas such as nitrogen (N2) into the tank11from the pipe14, the interior of the tank11is pressurized, and the solution LS is supplied from the pipe12. In addition, as illustrated inFIG.2C, the raw material source10may include, for example, a tank11filled with a solution LS, a pipe16connected to the bottom side of the tank11, and a valve17interposed in the pipe16. In the raw material source10illustrated inFIG.2C, the solution LS is supplied from the bottom side of the tank11via the pipe16using natural fall due to gravity.

FIG.3is a view illustrating another exemplary raw material source10, in which a configuration example in which the raw material source10supplies a slurry of a first solid raw material dispersed in a solvent to the raw material supply apparatuses30and40is illustrated. As illustrated inFIG.3, for example, the raw material source10includes a tank11filled with a slurry SL, a pipe12inserted into the tank11from above, a valve13interposed in the pipe12, and a vibration stage18configured to vibrate the tank11. In the raw material source10illustrated inFIG.3, the slurry SL is supplied from the pipe12by pressurizing the slurry SL filled in the tank11by its own weight while vibrating the tank11placed on the vibration stage18.

The raw material source10is connected to a raw material supply apparatus30via pipes L10and L11and thus supplies a solution of the first solid raw material dissolved in a solvent or a slurry of the first solid raw material dispersed in a solvent to the raw material supply apparatus30via the pipes L10and L11. Valves V11aand V11bare interposed in the pipe L11. When the valves V11aand V11bare opened, the solution or slurry M is supplied from the raw material source10to the raw material supply apparatus30, and when the valves V11aand V11bare closed, the supply of the solution or slurry M from the raw material source10to the raw material supply apparatus30is blocked. In addition, the pipe L11may be provided with a flow rate controller (not illustrated), an additional valve, or the like that controls the flow rate of the solution or slurry M flowing through the pipe L11.

In addition, the raw material source10is connected to a raw material supply apparatus40via pipes L10and L12and thus supplies the solution of the first solid raw material dissolved in the solvent or slurry of the first solid raw material dispersed in the solvent to the raw material supply apparatus40via the pipes L10and L12. Valves V12aand V12bare interposed in the pipe L12. When the valves V12aand V12bare opened, the solution or slurry M is supplied from the raw material source10to the raw material supply apparatus40, and when the valves V12aand V12bare closed, the supply of the solution or slurry M from the raw material source10to the raw material supply apparatus40is blocked. In addition, the pipe L12may be provided with a flow rate controller (not illustrated), an additional valve, or the like that controls the flow rate of the solution or slurry M flowing through the pipe L12.

The first solid raw material is not particularly limited, but may be, for example, an organic metal complex containing a metal element such as strontium (Sr), molybdenum (Mo), ruthenium (Ru), zirconium (Zr), hafnium (Hf), tungsten (W), or aluminum (Al), or a chloride containing a metal element such as tungsten (W) or aluminum (Al).

The solvent may be hexane, for example, as long as it can dissolve or disperse the first solid raw material to form a solution or slurry M.

The carrier gas source20supplies a carrier gas to the raw material supply apparatuses30and40. The carrier gas source20is connected to the pipe L11via the pipes L20and L21, and supplies the carrier gas to the raw material supply apparatus30via the pipes L20, L21, and L11. A valve V21is interposed in the pipe L21. When the valves V21and V11bare opened, the carrier gas is supplied from the carrier gas source20to the raw material supply apparatus30, and when the valves V21and V11bare closed, the supply of the carrier gas from the carrier gas source20to the raw material supply apparatus30is blocked. In addition, the pipe L21may be provided with a flow rate controller (not illustrated), an additional valve, or the like that controls the flow rate of the carrier gas flowing through the pipe L21.

In addition, the carrier gas source20is connected to the pipe L12via the pipes L20and L22, and supplies the carrier gas to the raw material supply apparatus40via the pipes L20, L22, and L12. A valve V22is interposed in the pipe L22. When the valves V22and V12bare opened, the carrier gas is supplied from the carrier gas source20to the raw material supply apparatus40, and when the valves V22and V12bare closed, the supply of the carrier gas from the carrier gas source20to the raw material supply apparatus40is blocked. In addition, the pipe L22may be provided with a flow rate controller (not illustrated), an additional valve, or the like that controls the flow rate of the carrier gas flowing through the pipe L22.

The carrier gas is not particularly limited, but may be, for example, an inert gas such as nitrogen (N2) or argon (Ar).

The raw material supply apparatus30stores the solution of the first solid raw material dissolved in the solvent or the slurry of the first solid raw material dispersed in the solvent, wherein the solution or slurry is supplied from the raw material source10. The raw material supply apparatus30includes a container31, a storage part33, a heater35, an exhaust apparatus37, and a detection part39.

The container31stores the solution or slurry M. For example, the tip end of the pipe L11is inserted into the container31from above, and the solution or slurry M and the carrier gas are supplied via the pipe L11. For example, a spray nozzle may be installed at the tip end of the pipe L11. In addition, for example, the tip end of a pipe L51is inserted into the container31from above, and a reactive gas generated in the container31is supplied to the processing apparatus50via the pipe L51. Furthermore, for example, the tip end of a pipe L30is inserted into the container31from above, and the interior of the container31is evacuated through the pipe L30, whereby the solvent is removed from the solution or slurry M in the container31so that a second solid raw material M2is formed.

Plural storage parts33are provided in the container31to store the solution or slurry M. The storage parts33have, for example, a tray shape having an opening in upper portion thereof. By providing the plural storage parts33in the container31, a specific surface area, which is the surface area per unit volume of the solution or slurry M stored in the container31, increases so that the time for removing the solvent from the solution or slurry M can be shortened.

The heater35heats the second solid raw material M2formed by removing the solvent from the solution or slurry M, thereby sublimating the second solid raw material M2to generate a reactive gas. The heater35may be, for example, a heater disposed so as to cover the bottom portion and the outer periphery of the container31. The heater35is configured to heat the interior of the container31to a temperature at which the second solid raw material M2can be sublimated to generate a reactive gas.

The exhaust apparatus37is connected to the container31via the pipe L30and evacuates the interior of the container31. When the interior of the container31in which the solution or slurry M is stored is evacuated by the exhaust apparatus37, the solvent is removed from the solution or slurry M in the container31, so that the second solid raw material M2is formed. A valve V30is interposed in the pipe L30. When the valve V30is opened, the interior of the container31is evacuated, and when the valve V30is closed, the evacuation of the interior of the container31is blocked. The exhaust apparatus37is an example of the removal part and includes a pressure adjusting valve, a vacuum pump, and the like.

The detection part39is interposed in the pipe L30. The detection part39detects whether or not the removal of the solvent from the solution or slurry M stored in the container31is completed by analyzing the components contained in the fluid flowing through the pipe L30. The detection part39includes at least one of a quadrupole mass spectrometer (QMS), a quantum cascade laser (QCL), an optical emission spectroscopy (OES), and a pressure gauge.

In the example ofFIG.1, the case where the pipe L21for supplying the carrier gas is connected to the pipe L11for supplying the solution or slurry M has been described, but the present disclosure is not limited thereto. For example, the tip end of the pipe L21for supplying the carrier gas may be directly inserted into the container31.

In addition, in the example ofFIG.1, the case where the pipe L30for evacuating the interior of the container31is inserted into the container31separately from the pipe L51for supplying a reactive gas to the processing apparatus50has been described, but the present disclosure is not limited thereto. For example, the pipe L30for evacuating the interior of the container31may be connected to the pipe L51for supplying a reactive gas to the processing apparatus50.

The raw material supply apparatus40is provided in parallel with the raw material supply apparatus30. The raw material supply apparatus40stores the solution of the first solid raw material dissolved in the solvent or the slurry of the first solid raw material dispersed in the solvent, wherein the solution or slurry is supplied from the raw material source10. The raw material supply apparatus40includes a container41, a storage part43, a heater45, an exhaust apparatus47, and a detection part49.

The container41stores the solution or slurry M. For example, the tip end of the pipe L12is inserted into the container41from above, and the solution or slurry M and the carrier gas are supplied via the pipe L12. For example, a spray nozzle may be installed to the tip end of the pipe L12. In addition, for example, the tip end of a pipe L52is inserted into the container41from above, and a reactive gas generated in the container41is supplied to the processing apparatus50via the pipe L52. Furthermore, for example, the tip end of a pipe L40is inserted into the container41from above, and the interior of the container41is evacuated through the pipe L40, whereby the solvent is removed from the solution or slurry M in the container41so that a second solid raw material M2is formed.

A plurality of storage parts43are provided in the container41to store the solution or slurry M. The storage parts43have, for example, a tray shape having an opening in upper portion thereof. By providing plural storage parts43in the container41, a specific surface area, which is the surface area per unit volume of the solution or slurry M stored in the container41, increases so that the time for removing the solvent from the solution or slurry M can be shortened.

The heater45heats the second solid raw material M2formed by removing the solvent from the solution or slurry M, thereby sublimating the second solid raw material M2to generate a reactive gas. The heater45may be, for example, a heater disposed so as to cover the bottom portion and the outer periphery of the container41. The heater45is configured to be able to heat the interior of the container41to a temperature at which the second solid raw material M2can be sublimated to generate a reactive gas.

The exhaust apparatus47is connected to the container41via the pipe L40and evacuates the interior of the container41. When the interior of the container41in which the solution or slurry M is stored is evacuated by the exhaust apparatus47, the solvent is removed from the solution or slurry M in the container41, so that the second solid raw material M2is formed. A valve V40is interposed in the pipe L40. When the valve V40is opened, the interior of the container41is evacuated, and when the valve V40is closed, the evacuation of the interior of the container41is blocked. The exhaust apparatus47is an example of the removal part and includes a pressure adjusting valve, a vacuum pump, and the like.

The detection part49is interposed in the pipe L40. The detection part49detects whether or not the removal of the solvent from the solution or slurry M injected into the container41is completed by analyzing the components contained in the fluid flowing through the pipe L40. Like the detection part39, the detection part49includes at least one of a QMS, a QCL, an OES, and a pressure gauge.

In the example ofFIG.1, the case where the pipe L22for supplying the carrier gas is connected to the pipe L12for supplying the solution or slurry M has been described, but the present disclosure is not limited thereto. For example, the tip end of the pipe L22for supplying the carrier gas may be directly inserted into the container41.

In addition, in the example ofFIG.1, the case where the pipe L40for evacuating the interior of the container41is inserted into the container41separately from the pipe L52for supplying a reactive gas to the processing apparatus50has been described, but the present disclosure is not limited thereto. For example, the pipe L40for evacuating the interior of the container41may be connected to the pipe L52for supplying a reactive gas to the processing apparatus50.

The processing apparatus50is connected to the raw material supply apparatus30via the pipes L51and L50, and the processing apparatus50is supplied with a reactive gas generated by heating and sublimating the second solid raw material M2in the raw material supply apparatus30. A valve V51is interposed in the pipe L51. When the valve V51is opened, the reactive gas is supplied from the raw material supply apparatus30to the processing apparatus50, and when the valve V51is closed, the supply of the reactive gas from the raw material supply apparatus30to the processing apparatus50is blocked.

In addition, the processing apparatus50is connected to the raw material supply apparatus40via the pipes L52and L50, and the processing apparatus50is supplied with a reactive gas generated by heating and sublimating the second solid raw material M2in the raw material supply apparatus40. A valve V52is interposed in the pipe L52. When the valve V52is opened, the reactive gas is supplied from the raw material supply apparatus40to the processing apparatus50, and when the valve V52is closed, the supply of the reactive gas from the raw material supply apparatus40to the processing apparatus50is blocked.

The processing apparatus50executes various processes such as a film forming process on a substrate such as a semiconductor wafer using the reactive gas supplied from the raw material supply apparatuses30and40. The processing apparatus50includes a processing container51, a mass flow meter52, and a valve53. The processing container51accommodates one or more substrates. The mass flow meter52is interposed in the pipe L50and measures the flow rate of the reactive gas flowing through the pipe L50. The valve53is interposed in the pipe L50. When the valve V53is opened, the reactive gas is supplied from the raw material supply apparatuses30and40to the processing container51, and when the valve V53is closed, the supply of the reactive gas from the raw material supply apparatus30and40to the processing container51is blocked.

The controller90controls each part of the raw material supply system1. For example, the controller90controls the operations of the raw material source10, the carrier gas source20, the raw material supply apparatuses30and40, the processing apparatus50, the exhaust apparatuses37and47, the detection parts39and49, and the like. The controller90controls the opening/closing of various valves. The controller90is an example of the controller, and may be, for example, a computer.

End Point Detection Process

With reference toFIG.4, an example of a process for detecting that the removal of the solvent from the solution or slurry M stored in the containers31and41of the raw material supply apparatuses30and40is completed (hereinafter referred to as an “end point detection process”) will be described.FIG.4is a flowchart illustrating an example of the end point detection process. Hereinafter, the end point detection process in the raw material supply apparatus30will be described as an example. However, the end point detection process in the raw material supply apparatus40may be the same as the end point detection process in the raw material supply apparatus30.

First, the controller90controls the opening/closing of the raw material source10and various valves so that the solution or slurry M is injected into the container31(step S1). In step S1, for example, after a predetermined time has elapsed, the controller90controls the opening/closing of the raw material source10and various valves to terminate the injection of the solution or slurry M into the container31. Furthermore, in step S1, for example, after a predetermined amount of solution or slurry M is supplied into the container31, the controller90may control the raw material source10and various valves to terminate the injection of the solution or slurry M into the container31. As described above, the timing at which the injection of the solution or the slurry M into the container31is terminated in step S1may be determined based on various conditions.

Subsequently, the controller90controls the opening and closing of the exhaust apparatus37and various valves to evacuate the interior of the container31, thereby initiating the removal of the solvent from the solution or slurry M stored in the container31(step S2).

Subsequently, the controller90acquires a detection result from the detection part39, and determines whether or not the removal of the solvent from the solution or slurry M stored in the container31is completed based on the detection result (step S3). For example, when the detection part39is a pressure gauge, the controller90determines that the removal of the solvent from the solution or slurry M stored in the container31is completed when the pressure gauge detects a pressure equal to or lower than a predetermined pressure. The predetermined pressure is determined by, for example, a preliminary experiment or the like.

When it is determined in step S3that the removal of the solvent from the solution or slurry M is completed, the controller90controls the opening/closing of the exhaust apparatus37and various valves to terminate the removal of the solvent from the solution or slurry M in the container31(step S4) and finishes the process. Meanwhile, when it is determined in step S3that the removal of the solvent from the solution or slurry M has not been completed, the controller90returns the process to step S2. That is, step S2is repeated until the removal of the solvent from the solution or slurry M is completed.

According to the end point detection process described above, the controller90detects that the removal of the solvent from the solution or slurry M stored in the container31is completed based on the detection result from the detection part39interposed in the pipe L30that connects the container31and the exhaust apparatus37to each other. As a result, it is possible to detect that the separation of the solvent contained in the solution or slurry M stored in the container31from the solid raw material is completed.

Operation of Raw Material Supply System

An example of the operation of the raw material supply system1(a raw material supply method) will be described. In the raw material supply system1, the controller90controls the opening/closing of various valves to supply a reactive gas from one of the two raw material supply apparatuses30and40provided in parallel to the processing apparatus50, and to fill the other one of the two raw material supply apparatuses30and40with a solid raw material. Hereinafter, an example of the operation of the raw material supply system1will be described in detail.

First, with reference toFIG.5, a case where the raw material supply apparatus30supplies a reactive gas to the processing apparatus50and the raw material supply apparatus40is filled with a solid raw material will be described.FIG.5is a view for explaining the operation of the raw material supply system1. InFIG.5, the pipes through which the carrier gas, the solution or slurry M, and the reactive gas are flowing are indicated by thick solid lines, and the pipes in which the carrier gas, the solution or slurry M, and the reactive gas are not flowing are indicated by thin solid lines. In the raw material supply system1, as illustrated inFIG.1, it is assumed that the valves V11a,V11b,V12a,V12b,V21, V22, V30, V40, V51, and V52are all closed in the initial state. It is also assumed that the second solid raw material M2is stored in the raw material supply apparatus30.

The controller90controls the heater35of the raw material supply apparatus30to heat and sublimate the second solid raw material M2stored in the storage parts33in the container31, thereby generating the reactive gas. In addition, the controller90opens the valves V21, V11b,and V51. As a result, the carrier gas is injected from the carrier gas source20into the container31of the raw material supply apparatus30via the pipes L20, L21, and L11, and the reactive gas generated in the container31is supplied to the processing apparatus50via the pipes L50and L51together with the carrier gas. In addition, the controller90opens the valves V12aand V12b.As a result, the solution or slurry M is injected from the raw material source10into the raw material supply apparatus40via the pipes L10and L12, and the solution or slurry M is stored in the storage parts43in the container41of the raw material supply apparatus40. After a predetermined amount of solution or slurry M is stored in the storage parts43in the container41, the controller90closes the valves V12aand V12band opens the valve V40. As a result, the interior of the container41is evacuated by the exhaust apparatus47, and the solvent is removed from the solution or slurry M stored in the container41. At this time, the controller90acquires a detection result from the detection part49, and determines whether or not the removal of the solvent from the solution or slurry M stored in the container41is completed based on the detection result. When the controller90determines that the removal of the solvent from the solution or the slurry M stored in the container41is completed, the controller90closes the valve V40. As a result, the evacuation of the interior of the container41by the exhaust apparatus47is blocked.

Next, with reference toFIG.6, a description is made of the case where the state in which the raw material supply apparatus30supplies the reactive gas to the processing apparatus50(seeFIG.5) is switched to the state in which the raw material supply apparatus40supplies the reactive gas to the processing apparatus50and the raw material supply apparatus30is filled with the solid raw material. The switching is executed, for example, when the removal of the solvent from the solution or slurry M stored in the container31of the raw material supply apparatus30is completed, and the remaining amount of the second solid raw material M2stored in the container41of the raw material supply apparatus40becomes a predetermined value or less.

FIG.6is a view for explaining the operation of the raw material supply system1. InFIG.6, the pipes through which the carrier gas, the solution or slurry M, and the reactive gas are flowing are indicated by thick solid lines, and the pipes in which the carrier gas, the solution or slurry M, and the reactive gas are not flowing are indicated by thin solid lines. In the raw material supply system1, it is assumed that the valves V11b,V21, and V51are opened, and the valves V11a,V12a,V12b,V22, V30, V40, and V52are closed in the state before switching.

First, the controller90turns off the heater35of the raw material supply apparatus30and closes the valves V11b,V21, and V51. As a result, the supply of the reactive gas from the raw material supply apparatus30to the processing apparatus50is stopped.

The controller90continuously controls the heater45of the raw material supply apparatus40to heat and sublimate the second solid raw material M2stored in the storage parts43in the container41, thereby generating the reactive gas. In addition, the controller90opens the valves V22, V12b,and V52. As a result, the carrier gas is injected from the carrier gas source20into the container41of the raw material supply apparatus40via the pipes L20, L22, and L12, and the reactive gas generated in the container41is supplied to the processing apparatus50via the pipes L50and L52together with the carrier gas. In addition, the controller90opens the valves V11aand V11b.As a result, the solution or slurry M is injected from the raw material source10into the raw material supply apparatus30via the pipes L10and L11, and the solution or slurry M is stored in the storage parts33in the container31of the raw material supply apparatus30. After a predetermined amount of solution or slurry M is stored in the storage parts33in the container31, the controller90closes the valves V11aand V11band opens the valve V30. As a result, the interior of the container31is evacuated by the exhaust apparatus37, and the solvent is removed from the solution or slurry M stored in the container31. At this time, the controller90acquires a detection result from the detection part39, and determines whether or not the removal of the solvent from the solution or slurry M stored in the container31is completed based on the detection result. When the controller90determines that the removal of the solvent from the solution or the slurry M stored in the container31is completed, the controller90closes the valve V30. As a result, the evacuation of the interior of the container31by the exhaust apparatus37is blocked.

With the raw material supply system1, the controller90controls the opening/closing of various valves to supply a reactive gas from one of the two raw material supply apparatuses30and40to the processing apparatus50, and to fill the other one of the two raw material supply apparatuses30and40with a solid raw material. This makes it possible for the raw material to be automatically replenished to the raw material supply apparatuses30and40so that the continuous operation capacity of the processing apparatus50can be improved, and the operating rate of the processing apparatus50can be improved.

In addition, with the raw material supply system1, the controller90detects that the removal of the solvent from the solution or slurry M stored in the container31is completed based on the detection result from the detection part39interposed in the pipe L30that connects the container31and the exhaust apparatus37to each other. As a result, it is possible to detect that the separation of the solvent contained in the solution or slurry M stored in the container31from the solid raw material is completed.

In addition, with the raw material supply system1, the controller90detects that the removal of the solvent from the solution or slurry M stored in the container41is completed based on the detection result from the detection part49interposed in the pipe L40that connects the container41and the exhaust apparatus47to each other. As a result, it is possible to detect that the separation of the solvent contained in the solution or slurry M stored in the container41from the solid raw material is completed.

The embodiments disclosed herein should be considered to be exemplary in all respects and not restrictive. The above-described embodiments may be omitted, replaced, or modified in various forms without departing from the scope and spirit of the appended claims.

In the above-described embodiments, a solution of a first solid raw material dissolved in a solvent or a slurry of a first solid raw material dispersed in a dispersion medium has been described as an example, but the present disclosure is not limited thereto. For example, instead of the slurry, a dispersion system such as a colloidal solution of the first solid raw material dispersed in a dispersion medium may also be used. For example, by using a colloidal solution, it is possible to fill a precursor having a higher concentration than that in the case of using a solution or slurry. The dispersion system includes a slurry and a colloid as subordinate concepts. The slurry is also referred to as a suspension. The colloid includes a colloidal solution as a subordinate concept. The colloidal solution is also referred to as sol.

The present international application claims priority based on Japanese Patent Application No. 2019-173420 filed on Sep. 24, 2019, the disclosure of which is incorporated herein in its entirety by reference.

EXPLANATION OF REFERENCE NUMERALS