Vacuum processing method for a substrate processing apparatus and a substrate processing apparatus

Abstract

To efficiently dry the inside of a vacuum chamber in a substrate processing apparatus.SOLUTION: In a decompression processing method for a substrate processing apparatus, a substrate processing apparatus includes a chamber for processing a substrate therein, a decompression unit that decompresses the interior of the chamber, and a gas supply unit that supplies gas to the interior of the chamber, and the decompression processing method includes the steps of supplying an additional substance that is miscible with liquid or solid moisture by the gas supply unit within the chamber, making the moisture a mixture of the additional substance, and decompressing the interior of the chamber by the decompression unit to remove the mixture from the interior of the chamber as a gas.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for depressurizing a substrate processing apparatus and a substrate processing apparatus.

Background Art

[0002] Patent Document 1 discloses an exhaust method in which the wall of an airtight container is heated to a desired temperature before the airtight container is opened to the atmosphere, the airtight container is maintained at the desired heating temperature for a desired time during the opening to the atmosphere and during the evacuation to vacuum, and then cooled to the desired temperature.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology according to the present disclosure efficiently dries the inside of a vacuum chamber in a substrate processing apparatus.

Means for Solving the Problems

[0005] One aspect of the present disclosure is a method for depressurizing a substrate processing apparatus, the substrate processing apparatus including a chamber for processing a substrate therein, a decompression unit for decompressing the inside of the chamber, and a gas supply unit for supplying a gas into the chamber, the decompression processing method including: supplying, inside the chamber, an additional substance that can be mixed with liquid or solid moisture by the gas supply unit; making the moisture into a mixture with the additional substance; and decompressing the inside of the chamber by the decompression unit and removing the mixture as a gas from the inside of the chamber.

Effects of the Invention

[0006] According to the present disclosure, drying inside a vacuum chamber in a substrate processing apparatus can be efficiently performed.

Brief Description of the Drawings

[0007]

Figure 1

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Mode for Carrying Out the Invention

[0008] In the manufacturing process of semiconductor devices, a processing gas is supplied to a vacuum chamber containing a semiconductor wafer (hereinafter sometimes referred to as "wafer"), and wafer processing is performed by reacting with the wafer. The surface of parts inside the vacuum chamber exposed to the processing gas together with the wafer is composed of a material that does not react with the processing gas, such as anodized aluminum.

[0009] By the way, for example, moisture in the air can mix into the inside of the vacuum chamber that is opened to the atmosphere during the manufacturing process, or the inside of the vacuum chamber that is opened to the atmosphere outside the manufacturing process such as maintenance. When a processing gas is supplied to the inside of the vacuum chamber in a state where moisture is mixed in the wafer processing, reaction products of the processing gas and moisture may react with the surface of parts such as anodized aluminum, causing discoloration and deterioration of the surface of the parts. Therefore, prior to the supply of the processing gas, it is required to remove the moisture inside the vacuum chamber as much as possible, that is, to dry it.

[0010] In the conventional pressure reduction treatment method, a vacuum drying method is adopted in which the inside of the vacuum chamber is evacuated to lower the boiling point of the mixed moisture and the moisture is recovered as a gas. However, when the liquid moisture condensed on the surface of parts during vacuum drying vaporizes, the liquid moisture may freeze and become solid due to its heat of vaporization. The sublimation rate from solid moisture is lower than the vaporization rate from liquid moisture, so it is considered that the drying time becomes longer. Also, if solid moisture remains inside the vacuum chamber, it dissolves due to the pressure increase and temperature increase due to heat input during wafer processing, causing moisture to be released inside the vacuum chamber.

[0011] Here, Patent Document 1 discloses an exhaust method in which an airtight container is heated for a desired time during atmosphere opening and during vacuum evacuation, and the inner wall of the airtight container is heated to a temperature equal to or higher than the vaporization temperature of water. By this, it is disclosed that adhesion of moisture to the inner wall of the airtight container can be suppressed, and also condensation and dew formation due to decompression of moisture can be suppressed by heating in the same manner also during the initial period of vacuum evacuation, and a good high vacuum can be achieved inside the airtight container.

[0012] However, in the method disclosed in Patent Document 1, time is required for heating and maintaining a high temperature of the vacuum container. Further, since fine pores are formed on the surface of parts made of anodized aluminum or the like, moisture that has entered the inside of the fine pores remains without being released from the fine pores even after heating, and after the elapse of the initial period of the above-described vacuum evacuation, there is a possibility that it will not be removed from inside the airtight container because it will condense again and become solid as it cools.

[0013] In view of the above problems, in the pressure reduction treatment method according to the present disclosure, the time required for drying the inside of the vacuum chamber in a manufacturing process, maintenance, etc. is shortened, and the inside of the vacuum chamber is appropriately dried.

[0014] Hereinafter, a plasma processing system including a plasma processing apparatus as a substrate processing apparatus according to the present embodiment, and a pressure reduction processing method of the plasma processing apparatus will be described with reference to the drawings. In this specification, for elements having substantially the same functional configuration, the same reference numerals are given to omit redundant description.

[0015] <Plasma Processing System> FIG. 1 is a plan view showing an outline of the configuration of a plasma processing system according to the present embodiment. In one embodiment, the plasma processing system includes a plasma processing apparatus 1 and a control unit 2. The plasma processing apparatus 1 includes a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. Further, the plasma processing chamber 10 has at least one gas supply port for supplying at least one processing gas and an additional gas GA described later to the plasma processing space, and at least one gas discharge port for discharging gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20 described later, and the gas discharge port is connected to a pressure reduction unit 40 described later. The substrate support unit 11 is disposed in the plasma processing space and has a substrate support surface for supporting a substrate.

[0016] The plasma generation unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR plasma (Electron-Cyclotron-resonance plasma), helicon wave plasma (HWP), surface wave plasma (SWP), or the like. Also, various types of plasma generation units including an AC (Alternating Current) plasma generation unit and a DC (Direct Current) plasma generation unit may be used. In one embodiment, the AC signal (AC power) used in the AC plasma generation unit has a frequency in the range of 100 kHz to 10 GHz. Therefore, the AC signal includes an RF (Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 200 kHz to 150 MHz.

[0017] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to execute various processes described in the present disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 so as to execute the various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processing unit (CPU: Central Processing Unit) 2a1, a storage unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control operations based on a program stored in the storage unit 2a2. The storage unit 2a2 may include a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network). Note that the above program may be recorded in a storage unit 2a2 readable by the computer 2a and installed from the storage unit 2a2 into the control unit 2. Also, the above storage unit 2a2 may be temporary or non-temporary.

[0018] Next, a configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus 1 will be described with reference to FIG. 2. The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and a pressure reduction unit 40. The plasma processing apparatus 1 also includes a substrate support unit 11 and a gas introduction unit. The gas introduction unit is configured to introduce at least one process gas and an additional gas GA into the plasma processing chamber 10. The gas introduction unit includes a shower head 13. The substrate support unit 11 is disposed in the plasma processing chamber 10. The shower head 13 is disposed above the substrate support unit 11. In one embodiment, the shower head 13 constitutes at least a part of the ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the shower head 13, the side wall 10a of the plasma processing chamber 10, and the substrate support unit 11. The side wall 10a is grounded. The shower head 13 and the substrate support unit 11 are electrically insulated from the plasma processing chamber 10 housing.

[0019] The substrate support part 11 includes a main body part 111 and a ring assembly 112. The main body part 111 has a central region (substrate support surface) 111a for supporting a substrate (wafer) W and an annular region (ring support surface) 111b for supporting the ring assembly 112. The annular region 111b of the main body part 111 surrounds the central region 111a of the main body part 111 in a plan view. The substrate W is disposed on the central region 111a of the main body part 111, and the ring assembly 112 is disposed on the annular region 111b of the main body part 111 so as to surround the substrate W on the central region 111a of the main body part 111. In one embodiment, the main body part 111 includes a base and an electrostatic chuck. The base includes a conductive member. The conductive member of the base functions as a lower electrode. The electrostatic chuck is disposed on the base. The upper surface of the electrostatic chuck has the substrate support surface 111a. The ring assembly 112 includes one or more annular members. At least one of the one or more annular members is an edge ring. Also, although not shown, the substrate support part 11 may include a temperature control module as a temperature control part configured to adjust at least one of the electrostatic chuck, the ring assembly 112, and the substrate to a target temperature. The temperature control module may include a heater, a heat transfer medium, a flow path, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path. Further, the substrate support part 11 may include a heat transfer gas supply part configured to supply a heat transfer gas between the back surface of the substrate W and the substrate support surface 111a.

[0020] The shower head 13 is configured to introduce at least one process gas and an additional gas from the gas supply unit 20 into the plasma processing space 10s. The shower head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and a plurality of gas introduction ports 13c. The process gas and the additional gas supplied to the gas supply port 13a pass through the gas diffusion chamber 13b and are introduced into the plasma processing space 10s from the plurality of gas introduction ports 13c. Further, the shower head 13 includes a conductive member. The conductive member of the shower head 13 functions as an upper electrode. In addition, the gas introduction unit may include one or more side gas injectors (SGI) attached to one or more openings formed in the side wall 10a in addition to the shower head 13.

[0021] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is configured to supply at least one process gas and an additional gas GA from the corresponding gas source 21 to the shower head 13 via the corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Further, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rates of at least one process gas and the additional gas GA.

[0022] In addition, in one embodiment, the introduction of the additional gas GA into the plasma processing chamber 10 is performed using the gas supply unit 20 and the gas introduction unit, but is not limited thereto. For example, the plasma processing apparatus 1 may include an arbitrary additional gas supply unit that is provided separately from the gas supply unit 20 and the gas introduction unit and introduces the additional gas GA into the plasma processing chamber 10.

[0023] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power), such as a source RF signal and a bias RF signal, to the conductive member of the substrate support 11 and / or the conductive member of the showerhead 13. Thereby, plasma is formed from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generation unit 12. Also, by supplying a bias RF signal to the conductive member of the substrate support 11, a bias potential is generated on the substrate W, and the ion component in the formed plasma can be drawn into the substrate W.

[0024] In one embodiment, the RF power supply 31 includes a first RF generation unit 31a and a second RF generation unit 31b. The first RF generation unit 31a is coupled to the conductive member of the substrate support unit 11 and / or the conductive member of the shower head 13 via at least one impedance matching circuit, and is configured to generate a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 13 MHz to 150 MHz. In one embodiment, the first RF generation unit 31a may be configured to generate a plurality of source RF signals having different frequencies. The generated one or more source RF signals are supplied to the conductive member of the substrate support unit 11 and / or the conductive member of the shower head 13. The second RF generation unit 31b is coupled to the conductive member of the substrate support unit 11 via at least one impedance matching circuit, and is configured to generate a bias RF signal (bias RF power). In one embodiment, the bias RF signal has a frequency lower than that of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 400 kHz to 13.56 MHz. In one embodiment, the second RF generation unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to the conductive member of the substrate support unit 11. Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0025] In addition, the power supply 30 may include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a first DC generation unit 32a and a second DC generation unit 32b. In one embodiment, the first DC generation unit 32a is connected to the conductive member of the substrate support unit 11 and is configured to generate a first DC signal. The generated first DC signal is applied to the conductive member of the substrate support unit 11. In one embodiment, the first DC signal may be applied to other electrodes such as the electrodes in the electrostatic chuck. In one embodiment, the second DC generation unit 32b is connected to the conductive member of the shower head 13 and is configured to generate a second DC signal. The generated second DC signal is applied to the conductive member of the shower head 13. In various embodiments, the first and second DC signals may be pulsed. Note that the first and second DC generation units 32a and 32b may be provided in addition to the RF power supply 31, or the first DC generation unit 32a may be provided instead of the second RF generation unit 31b.

[0026] The pressure reducing unit 40 can be connected to, for example, the gas discharge port 10e provided at the bottom of the plasma processing chamber 10. The pressure reducing unit 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may include a turbo molecular pump, a dry pump, or a combination thereof.

[0027] The pressure reducing unit 40 configured as described above can evacuate the inside of the plasma processing chamber 10 by evacuation described later and reduce the pressure inside the chamber.

[0028] The plasma processing apparatus 1 according to the present embodiment is configured as described above.

[0029] <First Embodiment> Next, the pressure reducing method MT1 of the plasma processing apparatus 1 according to the first embodiment will be described.

[0030] In the pressure reduction treatment method MT1 according to the present embodiment, the inside of the plasma processing chamber 10 is dried by sequentially executing the following steps ST1 to ST9. Note that the inside of the plasma processing chamber 10 includes the plasma processing space 10s and the part surface SF of the parts that are exposed to the plasma processing space 10s among the parts constituting the plasma processing chamber 10. The parts of the present embodiment may include various metal parts such as, for example, an anodized cooling plate. However, the parts of the present embodiment are not limited thereto. In addition to the above, parts that include a portion exposed to the plasma processing space 10s and into which the additional gas GA can be introduced onto the part surface SF may be included.

[0031] Hereinafter, steps ST1 to ST9 will be described with reference to FIGS. 3 to 9. FIG. 3 is a schematic diagram showing the state of solid moisture MS, liquid moisture ML, or gaseous moisture MG mixed inside the plasma processing chamber 10 and the surrounding atmosphere when the following steps ST1 to ST9 according to the present embodiment are executed. FIGS. 4 to 9 are state diagrams showing the state of moisture or a mixture described later in each step.

[0032] In the pressure reduction treatment method MT1, the temperature may change with the change in the pressure inside the plasma processing chamber 10 in steps ST1 to ST9. However, in the present embodiment, the inside of the plasma processing chamber 10 is heated and temperature-controlled to reach a certain temperature. The temperature control may be, for example, that the control unit 2 monitors the current temperature inside the plasma processing chamber 10, and when the current temperature is not the above-mentioned certain temperature, a signal is sent from the control unit 2 to the temperature control module, and the temperature is adjusted to the above-mentioned certain temperature using the function of the temperature control module. The above-mentioned certain temperature may be in a temperature range from slightly higher than room temperature to the upper limit temperature of a resin material such as an O-ring used in a part of the chamber, depending on the capacity of the function of the temperature control module used. Such a temperature range may be, for example, 40 to 200°C.

[0033] Before the execution of the pressure reduction treatment method MT1, moisture may enter the inside of the plasma processing chamber 10. Such entry may occur, for example, when replacing the substrate W during the manufacturing process, when opening the inside of the plasma processing chamber 10 to the atmosphere during maintenance, or when initially installing the plasma processing chamber 10 in the plasma processing apparatus 1. As a result of such entry, gas moisture MG enters the plasma processing space 10s inside the plasma processing chamber 10, and liquid moisture ML enters the surface SF of the parts (Fig. 3(A)). Note that the liquid moisture ML in Fig. 3 indicates one droplet of the liquid moisture ML that has entered the inside of the plasma processing chamber 10 on the surface SF of the parts. In the following description, the state of the liquid moisture ML as this one droplet will be described, but the same applies to other droplets of the liquid moisture ML that have entered the surface SF of the parts among the liquid moisture ML that has entered the inside of the plasma processing chamber 10.

[0034] In step ST1, the inside of the plasma processing chamber 10 is evacuated to a desired degree of vacuum using the pressure reduction unit 40. Specifically, the inside of the plasma processing chamber 10 is exhausted and pressure-reduced so as to have a degree of vacuum of, for example, 1 mTorr or less. Note that the desired degree of vacuum may more preferably be 1×10 -5 Torr (0.01 mTorr) or less.

[0035] According to step ST1, the gas moisture MG that has entered the inside of the plasma processing chamber 10 is removed from the plasma processing chamber 10 through the gas discharge port 10e.

[0036] During the evacuation in step ST1, among the liquid moisture ML, a part of the liquid moisture MLA vaporizes (VR) to become gas moisture MG, and the remaining liquid moisture MLB solidifies (FR) to become solid moisture MS (Fig. 3(B)). The gas moisture MG is removed from the plasma processing chamber 10 through the gas discharge port 10e. Also, the solid moisture MS remains on the surface SF of the parts inside the plasma processing chamber 10 even after the execution of step ST1. Note that the details of the vaporization (VR) of the part of the liquid moisture MLA and the solidification (FR) of the remaining liquid moisture MLB will be described later.

[0037] Next, in step ST2, an additional gas GA as an additive substance is introduced into the interior of the plasma processing chamber 10 (FIG. 3(C)). Specifically, for example, the additional gas GA is supplied from the corresponding gas source 21 of the gas supply unit 20 to the shower head 13 via the corresponding flow controller 22, and is introduced into the interior of the plasma processing chamber 10 from the shower head 13. Here, in the present embodiment, the pressure is controlled so that the interior of the plasma processing chamber 10 into which the additional gas GA is introduced reaches a certain pressure. Specifically, for example, the control unit 2 monitors the current pressure inside the plasma processing chamber 10. When the current pressure is not the above-mentioned certain pressure, a signal is sent from the control unit 2 to the gas supply unit 20 to change the flow rate of the additional gas GA supplied from the gas supply unit 20. Alternatively, a signal is sent from the control unit 2 to the pressure reducing unit 40 to change the exhaust rate from the plasma processing chamber 10. Thereby, the pressure is adjusted to the above-mentioned certain pressure.

[0038] The above-mentioned certain pressure is higher than the pressure at which the heat of the parts surface SF is efficiently transferred to the liquid moisture ML by the introduced additional gas GA, lower than the pressure at which the additional gas GA condenses on the parts surface SF, and is desirably lower than the vapor pressure VP of the liquid mixture MXL formed in step ST5 described later. Such a certain pressure may be, for example, 900 mTorr.

[0039] Next, in step ST3, the additional gas GA introduced into the interior of the plasma processing chamber 10 in step ST2 adsorbs (AD) to the solid moisture MS remaining on the parts surface SF in step ST1 (FIG. 3(D)). The adsorption (AD) may be, for example, due to the additional gas GA around the solid moisture MS being condensed by having its heat taken away by the solid moisture MS and adhering as a liquid to the surface of the solid moisture MS. Further, the adsorption (AD) may be, for example, due to the additional gas GA around the solid moisture MS being dissolved in the surface of the solid moisture MS.

[0040] Next, in step ST4, under the above-mentioned constant temperature and the above-mentioned constant pressure, the solid moisture MS melts to become liquid moisture ML (Fig. 3(E)). Details of the melting will be described later.

[0041] Next, in step ST5, the adsorbed additional gas GA is mixed with the liquid moisture ML generated in step ST4 to form a liquid mixture MXL of the liquid moisture ML and the additional gas GA (Fig. 3(F)).

[0042] Next, in step ST6, under the above-mentioned constant temperature and the above-mentioned constant pressure, a part of the liquid mixture MXL, i.e., liquid mixture MXLA, vaporizes (VR) to become a gas mixture MXG, and the remaining liquid mixture MXLB solidifies (FR) to become a solid mixture MXS (Fig. 3(G)). The gas mixture MXG is removed from the plasma processing chamber 10 through the gas discharge port 10e. Also, the solid mixture MXS remains on the surface SF of the parts inside the plasma processing chamber 10 after the execution of step ST6. Details of the vaporization (VR) of the part of the liquid mixture MXLA and the solidification (FR) of the remaining liquid mixture MXLB will be described later.

[0043] Next, in step ST7, the additional gas GA is adsorbed (AD) onto the remaining solid mixture MXS (Fig. 3(H)). The adsorption (AD) may be, for example, due to the additional gas GA around the solid mixture MXS being condensed by having heat taken away by the solid mixture MXS and adhering as a liquid to the surface of the solid mixture MXS. Also, the adsorption (AD) may be, for example, due to the additional gas GA around the solid mixture MXS being dissolved in the surface of the solid mixture MXS.

[0044] Next, in step ST8, under the above-mentioned constant temperature and the above-mentioned constant pressure, the solid mixture MXS melts to become a liquid mixture MXL (Fig. 3(I)).

[0045] Next, in step ST9, the adsorbed additional gas GA is mixed with the liquid mixture MXL generated in step ST8 to form a liquid mixture MXL with a higher concentration of the additional gas GA (Fig. 3(J)).

[0046] Next, under the above constant temperature and the above constant pressure, process ST6 is executed again. By process ST6, a part of the liquid mixture MXLA in the liquid mixture MXL vaporizes (VR) to become a gas mixture MXG, and the remaining liquid mixture MXLB solidifies (FR) to become a solid mixture MXS (Fig. 3(G)). The gas mixture MXG is removed from the plasma processing chamber 10 through the gas discharge port 10e. Further, the solid mixture MXS remains on the part surface SF inside the plasma processing chamber 10 even after the execution of process ST6 again.

[0047] After the above process ST6 is repeated, processes ST7 to ST9 are sequentially executed again, and thereafter, processes ST6 to ST9 are repeated.

[0048] By the above repetition, the volume of the liquid mixture MXL gradually decreases, and the concentration of the additional gas GA increases. After the last process ST9 described later, all of the liquid mixture MXL vaporizes (VR) to become a gas mixture MXG (Fig. 3(K)). The gas mixture MXG is removed from the plasma processing chamber 10 through the gas discharge port 10e. As a result, all the liquid moisture ML is removed from the inside of the plasma processing chamber 10, and the drying inside the plasma processing chamber 10 is completed.

[0049] Note that the above processes ST3 to ST9 proceed spontaneously while the additional gas GA is introduced into the plasma processing chamber 10 in process ST2 and maintained at the above constant pressure. Proceeding spontaneously means that processes ST3 to ST9 proceed without requiring other operations or controls.

[0050] Here, the vaporization (VR) of the above part of the liquid moisture MLA and the solidification (FR) of the above remaining liquid moisture MLB in process ST1 will be described with reference to FIGS. 4 to 6. FIGS. 4 and 5 are state diagrams showing the states that the above part of the liquid moisture MLA can take during the execution of process ST1. FIG. 6 is a state diagram showing the states that the above remaining liquid moisture MLB can take during the execution of process ST1.

[0051] In the state diagrams of FIGS. 4 to 6, the vertical axis represents pressure (Torr) and the horizontal axis represents Celsius temperature (°C). The solid line is the state curve of water or a mixture, showing the sublimation curve SC, the melting curve MC, and the vapor pressure curve VC. These state curves intersect at the triple point TP. The region surrounded by the sublimation curve SC and the melting curve MC, that is, the water or mixture contained in the solid phase SP, forms solid water MS or solid mixture MXS. The region surrounded by the melting curve MC and the vapor pressure curve VC, that is, the water or mixture contained in the liquid phase LP, forms liquid water ML or liquid mixture MXL. The region surrounded by the vapor pressure curve VC and the sublimation curve SC, that is, the water or mixture contained in the gas phase GP, forms gaseous water MG or gaseous mixture MXG. Also, the thick arrow is the locus showing the transition of the state of the water or mixture of interest. For example, the pressure and temperature at a point on the thick arrow indicate the pressure and temperature of the water or mixture of interest at that point. Note that the same applies to FIGS. 7 to 9 and FIGS. 11 to 13 described later.

[0052] First, the state of the above-mentioned partial liquid water MLA will be described. In FIG. 4, before the evacuation starts in step ST1, the above-mentioned partial liquid water MLA is in the state shown in state (a) of FIG. 4. When the evacuation starts in step ST1, the pressure of the above-mentioned partial liquid water MLA decreases along the thick arrow in FIG. 4 and vaporizes (VR) at the vapor pressure VP, and at the pressure at the end of the evacuation, it becomes the state shown in state (b) of FIG. 4, that is, gaseous water MG.

[0053] Here, when a part of the liquid moisture MLA vaporizes (VR), it absorbs the heat of vaporization from the part of the liquid moisture MLA itself, so the temperature of the part of the liquid moisture MLA itself decreases. While the part of the liquid moisture MLA continues to vaporize (VR), the temperature of the part of the liquid moisture MLA itself continues to decrease. FIG. 5 shows the state of the part of the liquid moisture ML in this case. In state (c) of FIG. 5, the temperature continues to decrease. Then, as the pressure decreases, the part of the liquid moisture MLA whose temperature has decreased above also vaporizes (VR) at the vapor pressure VP in sequence. At the pressure at the end of the evacuation, it is in the state shown in state (d) of FIG. 5, that is, it becomes gaseous moisture MG.

[0054] Also, there is a part of the part of the liquid moisture MLA whose temperature continues to decrease, solidifies (FR) at the freezing point FP, and becomes solid moisture MS. The part of the part of the liquid moisture MLA that has become solid moisture MS then sublimes at the sublimation pressure SLP as the pressure decreases. For the above part, at the pressure at the end of the evacuation, it is in the state shown in state (e) of FIG. 5, that is, it becomes gaseous moisture MG.

[0055] Next, the state of the remaining liquid moisture MLB will be described. In FIG. 6, before the evacuation starts in process ST1, the remaining liquid moisture MLB is in the state shown in state (a) of FIG. 6. When the evacuation starts in process ST1, the pressure of the remaining liquid moisture MLB decreases along the thick arrow in FIG. 6.

[0056] Here, when a part of the liquid moisture MLA vaporizes (VR), it absorbs the heat of vaporization from the remaining liquid moisture MLB, so the temperature of the remaining liquid moisture MLB decreases. While the part of the liquid moisture MLA continues to vaporize (VR), the temperature of the remaining liquid moisture MLB continues to decrease (state (f) of FIG. 6).

[0057] Subsequently, as the pressure decreases due to evacuation, the proportion of the above-mentioned partial liquid moisture MLA that vaporizes (VR) gradually decreases, and the proportion of the remaining liquid moisture MLB that solidifies (FR) increases. When all of the above-mentioned partial liquid moisture MLA has vaporized (VR) and all of the above-mentioned remaining liquid moisture MLB has solidified (FR), the temperature of the above-mentioned remaining liquid moisture MLB no longer decreases. At the pressure at the end of evacuation, the above-mentioned remaining liquid moisture MLB becomes in the state shown in state (g) of FIG. 6, that is, solid moisture MS.

[0058] Note that since the liquid moisture ML is constantly mixed with water molecules in different states due to molecular motion and the state is homogenized, strictly speaking, the above-mentioned partial liquid moisture MLA and the above-mentioned remaining liquid moisture MLB are not distinguishable. Therefore, in this embodiment, for convenience, conversely, the liquid moisture ML that reaches the state (b) of FIGS. 4 and 5 and becomes gaseous moisture MG at the end of evacuation is defined as the above-mentioned partial liquid moisture MLA, and the liquid moisture ML that reaches the state (g) of FIG. 6 and becomes solid moisture MS at the end of evacuation is defined as the above-mentioned remaining liquid moisture MLB.

[0059] Also, as described above, since the plasma processing chamber 10 is maintained at the above-mentioned constant temperature, the temperature of the liquid moisture ML attached to the part surface SF inside the plasma processing chamber 10 rises due to the heat input from the part surface. However, in this embodiment, since the rate of temperature rise due to the above-mentioned heat input is sufficiently small compared to the rate of temperature decrease when heat is taken away as the heat of vaporization by the above-mentioned vaporization (VR), the temperature rise due to the above-mentioned heat input is not considered in the above description and is omitted.

[0060] Next, the states of the solid moisture and the liquid mixture MXL during the execution of steps ST2 to ST9 will be described with reference to FIGS. 7 to 9. FIG. 7 is a state diagram showing the possible states of the solid moisture MS when additional gas is introduced in step ST2 and the pressure inside the plasma processing chamber 10 is adjusted to the above-mentioned constant pressure. FIG. 8 is a state diagram showing the possible states of the mixture in step ST6, and FIG. 9 is a state diagram showing the possible states of the mixture when all the liquid mixture MXL vaporizes (VR) after steps ST6 to ST9 are repeated.

[0061] As described above, the solid moisture MS remaining after evacuation in step ST1 melts in step ST4 to become liquid moisture ML. Specifically, in FIG. 7, in step ST2, additional gas GA is introduced and the pressure rises to the above-mentioned constant pressure. At the same time, it rises to the above-mentioned constant temperature by the heat input from the part surface SF (thick arrow in FIG. 7). As the pressure and temperature rise, the solid moisture MS melts at the freezing point FP and becomes the state shown in state (h) of FIG. 7, that is, liquid moisture ML.

[0062] Thereafter, additional gas GA is mixed with the liquid moisture ML in state (h) of FIG. 7 in step ST5, and a liquid mixture MXL is formed.

[0063] In FIG. 8, the solid line indicates the state curve of the mixture formed in step ST5, and the broken line indicates the state curve of the moisture when the above-mentioned additional gas GA is not mixed. In the liquid mixture MXL mixed with the additional gas GA according to the present embodiment, the boiling point temperature and the freezing point FP temperature under the condition of constant pressure are lower than those of the moisture when the additional gas GA is not mixed. Therefore, the state curve of the mixture shown by the solid line in FIG. 8 has moved to the left compared to the state curve of the moisture when the additional gas GA shown by the broken line is not mixed. Note that state (j) in FIG. 8, which is the state immediately after becoming the liquid mixture MXL in step ST5, has the same temperature and pressure as state (h) in FIG. 7 immediately after melting in step ST4.

[0064] As a result of the movement of the state curve of the mixture as described above, the vapor pressure VP of the liquid mixture MXL becomes higher than the vapor pressure VP of the liquid moisture ML. Further, since the above-mentioned constant pressure in the present embodiment is set to be lower than the vapor pressure VP of the liquid mixture MXL as described above, the mixture in the state (j) of FIG. 8 is included in the gas phase GP. Therefore, in step ST6, a part of the liquid mixture MXLA vaporizes (VR) to become a gas mixture MXG.

[0065] In setting the above-mentioned constant pressure in the present embodiment, as the vapor pressure VP of the liquid mixture MXL, a value obtained in advance may be used. That is, for example, calculations or experiments are performed on the liquid mixture MXL for each type of additional gas GA, and the theoretical value or measured value of the vapor pressure VP is obtained in advance, and this is used as the vapor pressure VP of the liquid mixture MXL to set the above-mentioned constant pressure.

[0066] Further, in step ST6, when a part of the liquid mixture MXLA vaporizes (VR), it takes away the heat of vaporization from the remaining liquid mixture MXLB, so the temperature of the remaining liquid mixture MXLB decreases. While a part of the liquid mixture MXLA continues to vaporize (VR), the temperature of the remaining liquid mixture MXLB continues to decrease (state (k) in FIG. 8). When the temperature of the remaining liquid mixture MXLB drops below the freezing point FP, the remaining liquid mixture MXLB solidifies (FR) and becomes the state shown in state (l) of FIG. 8, that is, a solid mixture MXS.

[0067] As described above, steps ST6 to ST9 are repeated for the liquid mixture MXL, and the volume of the liquid mixture MXL gradually decreases and the concentration of the additional gas GA increases. According to the above repetition, as the concentration of the additional gas GA increases, the state curve of the mixture further moves to the left.

[0068] In FIG. 9, it is assumed that a liquid mixture MXL in the state shown in state (m) of FIG. 9 is formed by the process ST9 after the above repetition. As a result of the movement of the state curve of the mixture by the above repetition, the liquid mixture MXL in state (m) of FIG. 9 is contained in the gas phase GP. Therefore, the liquid mixture MXL in state (m) of FIG. 9 vaporizes (VR) to become a gas mixture MXG. At this time, even if all of the liquid mixture MXL in state (m) of FIG. 9 vaporizes (VR) and the temperature drops to state (n) of FIG. 9 due to the heat of vaporization, the freezing point FP of the mixture is not reached, and the mixture in state (n) of FIG. 9 does not solidify (FR). Therefore, after the process ST9 after the above repetition, all of the liquid mixture MXL vaporizes (VR) to become a gas mixture MXG.

[0069] <Second Embodiment> Next, a pressure reduction treatment method MT2 of the plasma processing apparatus 1 according to the second embodiment will be described.

[0070] In the pressure reduction treatment method MT2 according to the present embodiment, the inside of the plasma processing chamber 10 is dried by sequentially executing the following steps ST20 to ST29. Hereinafter, steps ST20 to ST29 will be described with reference to FIGS. 10 to 13. FIG. 10 is a schematic diagram showing the state of solid moisture MS, liquid moisture ML, or gas moisture MG mixed inside the plasma processing chamber 10 when the following steps ST20 to ST29 according to the present embodiment are executed. FIGS. 11 to 13 are state diagrams showing the state of moisture or a mixture described later in each step.

[0071] Similar to the pressure reduction treatment method MT1 of the first embodiment, moisture may be mixed inside the plasma processing chamber 10 before the execution of the pressure reduction treatment method MT2. As a result of such mixing, gas moisture MG is mixed in the plasma processing space 10s, and liquid moisture ML is mixed on the part surface SF inside the plasma processing chamber 10 (FIG. 10(A)).

[0072] In process ST20, the inside of the plasma processing chamber 10 is evacuated to a desired degree of vacuum using the decompression unit 40. Specifically, the inside of the plasma processing chamber 10 is exhausted and decompressed so that the degree of vacuum becomes, for example, 1 mTorr or less. After the evacuation to the desired degree of vacuum is completed, the evacuation of the plasma processing chamber 10 by the decompression unit 40 is stopped. The desired degree of vacuum is more preferably 1×10 -5 Torr (0.01 mTorr) or less.

[0073] According to process ST20, the gaseous moisture MG mixed into the inside of the plasma processing chamber 10 is removed from the plasma processing chamber 10 through the gas outlet 10e.

[0074] By process ST20, a part of the liquid moisture MLA among the liquid moisture ML vaporizes (VR) to become gaseous moisture MG, and the remaining liquid moisture MLB solidifies (FR) to become solid moisture MS (FIG. 10(B)). The gaseous moisture MG is removed from the plasma processing chamber 10 through the gas outlet 10e. Also, the solid moisture MS remains on the part surface SF inside the plasma processing chamber 10 even after the execution of process ST20. The details of the vaporization (VR) of the part of the liquid moisture MLA and the solidification (FR) of the remaining liquid moisture MLB are the same as the description using FIGS. 4 to 6 according to the first embodiment, and thus are omitted.

[0075] Next, in step ST21, an additional gas GA as an additive substance is introduced into the interior of the plasma processing chamber 10 (FIG. 10(C)). Specifically, for example, the additional gas GA is supplied from the corresponding gas source 21 of the gas supply unit 20 to the shower head 13 via the corresponding flow controller 22, and is introduced into the interior of the plasma processing chamber 10 from the shower head 13. Here, in the present embodiment, the pressure is controlled so that the interior of the plasma processing chamber 10 into which the additional gas GA is introduced reaches a certain pressure. Specifically, for example, the control unit 2 monitors the current pressure inside the plasma processing chamber 10. When the current pressure is not the above-mentioned certain pressure, a signal is sent from the control unit 2 to the gas supply unit 20, and the pressure is adjusted to the above-mentioned certain pressure by changing the flow rate of the additional gas GA supplied from the gas supply unit 20.

[0076] The above-mentioned certain pressure is desirably in a range higher than the pressure at which the heat of the part surface SF is efficiently transferred to the liquid moisture ML by the introduced additional gas GA, and higher than the pressure at which the solid moisture MS and the solid mixture MXS formed in step ST25 described later melt, and lower than the pressure at which the additional gas GA condenses on the part surface SF. Such a certain pressure may be, for example, atmospheric pressure, but since there is a risk that the interior of the plasma processing chamber 10 will be opened to the atmosphere and moisture in the atmosphere will be mixed in again when it is above atmospheric pressure, it is desirable that the pressure be lower than atmospheric pressure.

[0077] Next, in step ST22, the additional gas GA introduced into the interior of the plasma processing chamber 10 in step ST21 adsorbs (AD) to the solid moisture MS remaining in step ST20 (FIG. 10(D)). The adsorption (AD) may be, for example, due to the additional gas GA around the solid moisture MS being condensed by having its heat taken away by the solid moisture MS and adhering as a liquid to the surface of the solid moisture MS. Further, the adsorption (AD) may be, for example, due to the additional gas GA around the solid moisture MS being dissolved in the surface of the solid moisture MS.

[0078] Next, in step ST23, under the above constant pressure, the solid moisture MS melts to become liquid moisture ML (Figure 10(E)). Details of the melting will be described later.

[0079] Next, in step ST24, the adsorbed additional gas GA is mixed with the liquid moisture ML generated in step ST23 to form a liquid mixture MXL of the liquid moisture ML and the additional gas GA (Figure 10(F)).

[0080] Next, in step ST25, again, the inside of the plasma processing chamber 10 is evacuated to a desired degree of vacuum using the decompression unit 40. The evacuation in step ST25 evacuates the inside of the plasma processing chamber 10 to a pressure lower than at least the vapor pressure VP of the liquid mixture MXLA described later, and decompresses it. Specifically, for example, it may be decompressed to the same degree of vacuum as in step ST20. Further, after the evacuation to the desired degree of vacuum is completed, the evacuation of the plasma processing chamber 10 by the decompression unit 40 is stopped.

[0081] During the execution of step ST25, part of the liquid mixture MXL, the liquid mixture MXLA, vaporizes (VR) to become a gas mixture MXG, and the remaining liquid mixture MXLB solidifies (FR) to become a solid mixture MXS (Figure 10(G)). The gas mixture MXG is removed from the plasma processing chamber 10 through the gas discharge port 10e. Also, the solid mixture MXS remains on the part surface SF inside the plasma processing chamber 10 even after the execution of step ST25. Note that details of the vaporization (VR) of the part of the liquid mixture MXLA and the solidification (FR) of the remaining liquid mixture MXLB will be described later.

[0082] Next, in step ST26, again, the additional gas GA is introduced into the plasma processing chamber 10 (Figure 10(H)). In step ST26, the additional gas GA is introduced to the above constant pressure in the same manner as in step ST21.

[0083] Next, in step ST27, the additional gas GA introduced into the interior of the plasma processing chamber 10 in step ST26 adsorbs (AD) to the remaining solid mixture MXS (FIG. 10(I)). The adsorption (AD) may be, for example, due to the additional gas GA around the solid mixture MXS condensing by having its heat taken away by the solid mixture MXS and adhering as a liquid to the surface of the solid mixture MXS. Also, the adsorption (AD) may be, for example, due to the additional gas GA around the solid mixture MXS being dissolved in the surface of the solid mixture MXS.

[0084] Next, in step ST28, under the above-mentioned constant pressure, the solid mixture MXS melts to become a liquid mixture MXL (FIG. 10(J)).

[0085] Next, in step ST29, the adsorbed additional gas GA is mixed with the liquid mixture MXL generated in step ST28 to form a liquid mixture MXL with a higher concentration of the additional gas GA (FIG. 10(K)).

[0086] After step ST29, step ST25 is executed again, and the interior of the plasma processing chamber 10 is evacuated to a desired degree of vacuum using the decompression unit 40. That is, after step ST29, steps ST25 to ST29 are repeated. From another perspective, in the decompression processing method MT2 according to the second embodiment, the step of supplying the additional gas GA and the step of evacuating are alternately repeated.

[0087] By the above repetition, the volume of the liquid mixture MXL gradually decreases, and the concentration of the additional gas GA increases. After step ST29 after the above repetition, all of the liquid mixture MXL vaporizes (VR) to become a gas mixture MXG (FIG. 10(L)). The gas mixture MXG is removed from the plasma processing chamber 10 through the gas discharge port 10e. Thereby, all of the liquid moisture ML is removed from the interior of the plasma processing chamber 10, and the drying of the interior of the plasma processing chamber 10 is completed.

[0088] Next, the states of the water content and the mixture during the execution of the reduced-pressure treatment method MT2 will be described with reference to FIGS. 11 to 13. FIG. 11 is a state diagram showing the possible states of the solid moisture MS when the additional gas GA is introduced to reach the above-mentioned constant pressure in step ST21. FIG. 12 is a state diagram showing the possible states of the mixture in the above-mentioned step ST25 again, and FIG. 13 is a state diagram showing the possible states of the mixture when all the liquid mixture MXL vaporizes (VR) after step ST29 after the above-mentioned repetition.

[0089] As described above, the solid moisture MS remaining after evacuation in step ST20 melts in step ST23 to become liquid moisture ML. Specifically, in FIG. 11, from the state (p) showing the state of the solid moisture MS remaining after evacuation in step ST20, the additional gas GA is introduced in step ST21 and the pressure rises to the above-mentioned constant pressure. Since the above-mentioned constant pressure in the present embodiment is set to be higher than the pressure at which the solid moisture MS melts as described above, the solid moisture MS melts at the pressure of the freezing point FP. Also, the temperature slightly rises due to the latent heat such as the melting and the condensation of the gaseous moisture MG. As a result, the solid moisture MS becomes the state shown in state (q) in FIG. 11, that is, liquid moisture ML.

[0090] In addition, when setting the above-mentioned constant pressure in the present embodiment, as the pressure at which the solid moisture MS and the solid mixture MXS formed in step ST25 described later melt, for example, theoretical values or measured values obtained in advance by calculation or experiment for each type of the additional gas GA may be used.

[0091] Thereafter, the additional gas GA is mixed with the liquid moisture ML in state (q) in FIG. 11 in step ST24, and a liquid mixture MXL is formed.

[0092] In FIG. 12, the solid line indicates the state curve of the mixture formed in process ST24, and the dashed line indicates the state curve of the moisture when the additional gas GA is not mixed. In the liquid mixture MXL in which the additional gas GA is mixed, the vapor pressure VP under the condition of constant temperature increases and the pressure of the freezing point FP decreases as compared with the moisture when the additional gas GA is not mixed. For this reason, the state curve of the mixture shown by the solid line in FIG. 12 has moved to the left from the state curve of the moisture when the additional gas GA shown by the dashed line is not mixed.

[0093] Here, the state (r) in FIG. 12, which is the state immediately after the liquid mixture MXL is formed in process ST24, has the same temperature and pressure as the state (q) in FIG. 11 immediately after melting in process ST23. In this state, when process ST25 is started, a part of the liquid moisture MLA decreases in pressure along the thick arrow in FIG. 12 and vaporizes (VR) at the vapor pressure VP, and at the pressure when process ST25 is completed, it becomes the state shown by the state (s) in FIG. 12, that is, the gaseous moisture MG.

[0094] Here, when a part of the liquid mixture MXLA vaporizes (VR) in process ST25, it takes the heat of vaporization from the remaining liquid moisture MLB, so the temperature of the remaining liquid mixture MXB decreases. While a part of the liquid mixture MXLA continues to vaporize (VR), the temperature of the remaining liquid mixture MXB continues to decrease. When the temperature of the remaining liquid mixture MXB drops below the freezing point FP, the remaining liquid mixture MXB solidifies (FR) and becomes the state shown by the state (t) in FIG. 12, that is, the solid mixture MXS.

[0095] For the solid mixture MXS shown by the state (t) in FIG. 12, as described above, processes ST26 to ST29 are repeated. As a result, the volume of the liquid mixture MXL gradually becomes smaller and the concentration of the additional gas GA becomes higher. According to the above repetition, as the concentration of the additional gas GA increases, the state curve of the mixture moves further to the left.

[0096] In FIG. 13, it is assumed that the liquid mixture MXL in the state shown in state (x) of FIG. 13 is formed by the process ST29 after the above repetition. When the process ST25 is executed on the liquid mixture MXL in the state (x) of FIG. 13, the liquid mixture MXL vaporizes (VR) at the vapor pressure VP and becomes the state shown in state (y) of FIG. 13, that is, the gas mixture MXG. At this time, since the heat of vaporization is taken from the liquid mixture MXL itself, the temperature of the liquid mixture MXL decreases. However, as a result of the movement of the state curve of the mixture due to the above repetition, the temperature of the liquid mixture MXL does not drop below the freezing point FP. Therefore, the temperature-decreased liquid mixture MXL also sequentially vaporizes (VR) at the vapor pressure VP, and even the liquid mixture MXL with the most decreased temperature becomes the state shown in state (z) of FIG. 13, that is, the gas mixture MXG.

[0097] Here, the additional substances that can be used as the additional gas GA in the above first and second embodiments will be described.

[0098] The additional gas GA may be a substance that is miscible with moisture and causes the state curve of the mixture formed by mixing to shift so that it becomes easier to vaporize (VR) than moisture. In Table 1 below, an appropriateness evaluation is performed on such substances as the additional gas GA.

[0099]

Table 1

[0100] Table 1 shows an example of the gas that can be introduced into the plasma processing chamber 10 in the plasma processing apparatus 1 according to the present embodiment, and their solubility in water, freezing point, boiling point, and azeotropic point. Also, regarding the appropriateness evaluation, appropriateness A means that the substance is most suitable as the additional gas GA, appropriateness B is the next most suitable after appropriateness A, appropriateness C is the next most suitable after appropriateness B, and appropriateness D means that it is applicable but inferior in appropriateness compared to the substances of appropriateness A to C.

[0101] In the proper evaluation, the propriety can be determined mainly by considering the solubility in water and the degrees of decrease in boiling point, freezing point, and azeotropic point when dissolved.

[0102] In this embodiment, ammonia (NH3) and its aqueous solution showed high propriety with Propriety A. Next, alcohols such as ethanol and propanol showed Propriety B and had a relatively high propriety after ammonia. Also, carbon dioxide (CO2) showed Propriety C and a certain propriety. Substances other than the above were Propriety D, which were applicable but had inferior propriety compared to the substances with Propriety A to C. Therefore, as the additional gas GA according to this embodiment, it is particularly preferable to apply ammonia, which is a substance with Propriety A. Next, it is preferable to apply alcohol, which is a substance with Propriety B. Then, it is preferable to apply carbon dioxide, which is a substance with Propriety C.

[0103] Note that as a method for introducing the additional substance, in this embodiment, it is introduced as the additional gas GA from the gas supply unit 20 through the gas introduction unit, but it is not limited to this. As long as it can be uniformly introduced into the plasma processing chamber 10, the additional substance can be introduced in the form of droplets such as aerosol (mist), and a mixture can be formed.

[0104] By the way, according to the present disclosure, for example, even by introducing the additional substance without performing the above evacuation and forming a mixture, it is possible to shorten the time required for drying the inside of the plasma processing chamber 10. However, it is preferable to introduce the additional gas GA in the state where the above evacuation is performed as in the above embodiment. Hereinafter, the significance of the above evacuation, that is, the process ST1 according to the first embodiment, the processes ST20 and ST25 according to the second embodiment, will be described in detail with reference to FIGS. 14 to 16.

[0105] In FIG. 14, fine pores MV may be formed on the surface SF of parts such as anodized aluminum inside the plasma processing chamber 10 according to this embodiment. When moisture enters the plasma processing chamber 10, liquid moisture ML can enter the fine pores MV due to capillary action.

[0106] Here, when the above evacuation is not performed and, for example, alcohol AH is applied as an additional substance, it is conceivable to form a mixture by means such as wiping the parts with alcohol just before installation or immersing the parts in alcohol AH in advance. However, the ease of entry into the fine pores MV by capillary action differs between liquid moisture ML and alcohol AH, and since alcohol is less likely to enter, alcohol AH cannot reach the depths of the fine pores MV, and a mixture cannot be formed deep inside the fine pores MV.

[0107] Hereinafter, the ease of entry into the fine pores MV by capillary action will be described in detail. The ease of entry when a liquid such as liquid moisture ML or alcohol AH enters the fine pores MV by capillary action can be estimated by obtaining the liquid level height h based on the following formula (1).

[0108] h = 2T × cosθ / (ρ × g × r) ···(1)

[0109] However, in formula (1), h is the liquid level height of the liquid entering the fine pores MV, T is the surface tension of the above liquid, θ is the contact angle of the above liquid, ρ is the density of the above liquid, g is the acceleration due to gravity, and r is the inner diameter of the fine pores MV.

[0110] FIG. 15 is a schematic cross-sectional view of the part showing the liquid level height h of alcohol AH entering the fine pores MV when attempting to form a mixture by means such as wiping the parts with alcohol (AH) just before installation or immersing the parts in alcohol AH in advance. As an example of alcohol AH, although not limited, ethanol (EtOH), propanol (n-ProOH), isopropyl alcohol (IPA), etc. can be considered. Further, FIG. 16 is a schematic cross-sectional view of the part showing the liquid level height h of liquid moisture ML when liquid moisture ML enters the fine pores MV under the same conditions.

[0111] Based on Equation (1), considering the contact angle θ, gravitational acceleration g, and inner diameter r as constants under equal conditions, and comparing the T / ρ values of liquid moisture ML and alcohol AH respectively, the liquid level height h of alcohol AH shown in Figure 15 is about 40% of the liquid level height h of water shown in Figure 16. That is, the ease of entry into the fine pores MV is about 2.5 times greater for liquid moisture ML than for alcohol AH.

[0112] Therefore, by means such as wiping the parts surface SF with alcohol (AH) immediately before installation or immersing the parts in alcohol AH in advance, alcohol AH cannot enter to the deepest part of the fine pores MV where liquid moisture ML can enter, and a mixture cannot be formed.

[0113] For this reason, in order to form a mixture to the deepest part of the fine pores MV, shorten the time required for drying the inside of the vacuum chamber, and properly dry the inside of the vacuum chamber, it is preferable to introduce additional gas GA after performing the above evacuation.

[0114] According to the above embodiments, the time required for drying the inside of the vacuum chamber can be shortened, and the inside of the vacuum chamber can be properly dried.

[0115] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, or changed in various forms without departing from the scope and gist of the appended claims.

Explanation of Reference Numerals

[0116] 1 Plasma processing apparatus 10 Plasma processing chamber 10 20 Gas supply unit 40 Pressure reduction unit MT1 Pressure reduction processing method GA Additional gas ML Liquid moisture MS Solid moisture MG Gas moisture MXL Liquid mixture MXS Solid mixture MXG gas mixture

Claims

1. A method for pressure reduction treatment of a substrate processing apparatus, comprising: The substrate processing apparatus includes: a chamber for processing a substrate therein; a pressure reduction unit for reducing the pressure inside the chamber; a gas supply unit for supplying gas into the chamber, The pressure reduction treatment method includes: in the chamber, a step of supplying an additional substance that can be mixed with liquid or solid moisture by the gas supply unit; a step of making the moisture into a mixture with the additional substance; a step of reducing the pressure inside the chamber by the pressure reduction unit and removing the mixture as a gas from inside the chamber, A method for pressure reduction treatment of a substrate processing apparatus, wherein the step of supplying the additional substance and the step of reducing the pressure are alternately repeated.

2. The method for pressure reduction treatment of a substrate processing apparatus according to claim 1, wherein the additional substance includes at least one of alcohol, ammonia, and carbon dioxide.

3. The method for pressure reduction treatment of a substrate processing apparatus according to claim 1 or 2, wherein in the step of supplying the additional substance, the additional substance is supplied in a state where the pressure inside the chamber is reduced by the pressure reduction unit.

4. The substrate processing apparatus further includes a temperature control unit, During the execution of the pressure reduction treatment method, the temperature inside the chamber is raised by the temperature control unit. The method for pressure reduction treatment of a substrate processing apparatus according to any one of claims 1 to 3.

5. The method for pressure reduction treatment of a substrate processing apparatus according to claim 4, wherein in the step of supplying the additional substance, the additional substance is supplied so as to have a pressure lower than the vapor pressures of the additional substance and the mixture.

6. The method for pressure reduction treatment of a substrate processing apparatus according to any one of claims 1 to 3, wherein in the step of supplying the additional substance, the additional substance is supplied so as to have a pressure higher than the pressure at which the solid moisture or the solid mixture melts and lower than the vapor pressure of the additional substance.

7. A method for pressure reduction treatment of a substrate processing apparatus, comprising: The substrate processing apparatus includes: a chamber for processing a substrate therein; a pressure reduction unit for reducing the pressure inside the chamber; a gas supply unit for supplying gas into the chamber, The pressure reduction treatment method includes: in the chamber, a step of supplying an additional substance by the gas supply unit; a step of reducing the pressure inside the chamber by the pressure reduction unit, The additional substance includes at least alcohol, ammonia, or carbon dioxide. Repeating the step of supplying the additive substance and the step of reducing the pressure alternately. A method for pressure reduction treatment of a substrate processing apparatus.

8. A substrate processing apparatus, comprising: A chamber for processing a substrate therein; A pressure reduction unit for reducing the pressure inside the chamber; A gas supply unit for supplying gas into the chamber; A control unit for controlling the substrate processing apparatus, wherein the control unit: In the chamber, a step of supplying an additive substance that can be mixed with liquid or solid moisture by the gas supply unit; A step of making the moisture into a mixture of the additive substance; The substrate processing apparatus is configured to be controllable to execute a step of reducing the pressure inside the chamber by the pressure reduction unit and removing the mixture as a gas from inside the chamber, and the substrate processing apparatus is configured to be controllable to alternately repeat the step of supplying the additive substance and the step of reducing the pressure.

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