Substrate processing method and ionic liquid

Abstract

To provide a technique capable of suppressing pattern collapse.SOLUTION: A substrate processing method according to an embodiment of the present invention includes the steps of supplying an ionic liquid to the surface of a patterned substrate to form a film of the ionic liquid on the surface of the substrate, and the ionic liquid has a cation including a hydrocarbon chain of 6 or more carbon atoms, the hydrocarbon chain has at least one hydrogen atom replaced by a fluorine atom.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a substrate processing method and an ionic liquid.

Background Art

[0002] There is known a technique in which after isopropyl alcohol (IPA) is filled as a liquid for preventing drying on the surface of a substrate on which a pattern is formed, supercritical treatment is performed on the substrate (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of suppressing pattern collapse.

Means for Solving the Problems

[0005] A substrate processing method according to an aspect of the present disclosure includes a step of supplying an ionic liquid to the surface of a substrate on which a pattern is formed and forming a film of the ionic liquid on the surface of the substrate The process involves subjecting the substrate on which the ionic liquid film is formed to supercritical fluid treatment, The ionic liquid has a cation containing a hydrocarbon chain having 6 or more carbon atoms, and at least one hydrogen atom in the hydrocarbon chain is replaced by a fluorine atom.

Effects of the Invention

[0006] According to the present disclosure, pattern collapse can be suppressed.

Brief Description of the Drawings

[0007] [Figure 1] A flowchart showing a substrate processing method according to an embodiment [Figure 2] Cross-sectional view showing a substrate processing method according to an embodiment. [Figure 3] Schematic diagram showing an example of a cleaning device. [Figure 4] Schematic diagram showing an example of a coating apparatus. [Figure 5] Schematic diagram showing an example of a supercritical fluid processing device. [Figure 6] Schematic diagram showing an example of a substrate processing system. [Figure 7] Schematic diagram showing another example of a substrate processing system. [Figure 8] Diagram illustrating ionic liquids (1) [Figure 9] Diagram illustrating ionic liquids (2) [Figure 10] Figure showing the results of the surface tension analysis of ionic liquids. [Modes for carrying out the invention]

[0008] Hereinafter, exemplary embodiments of the present disclosure, not limited to those described herein, will be described with reference to the attached drawings. In all attached drawings, identical or corresponding members or components are denoted by the same or corresponding reference numerals, and redundant descriptions are omitted.

[0009] [Substrate processing method] Referring to Figures 1 and 2, a substrate processing method according to an embodiment will be described. As shown in Figure 1, the substrate processing method according to the embodiment includes a cleaning step S10, an ionic liquid coating step S20, and a drying step S30.

[0010] The cleaning step S10 includes supplying a chemical solution and a rinsing solution to the surface of the substrate W on which the pattern 11 is formed in a predetermined order to clean the surface of the substrate W (see Figure 2(a)). The substrate W is, for example, a semiconductor wafer. The chemical solution includes SC1 solution (a mixture of ammonia and hydrogen peroxide), which is an alkaline chemical solution. By supplying SC1 solution to the surface of the substrate W, particles and organic contaminants adhering to the surface of the substrate W can be removed. The chemical solution may also include a dilute hydrofluoric acid aqueous solution (DHF), which is an acidic chemical solution. By supplying DHF to the surface of the substrate W, the native oxide film formed on the surface of the substrate W can be removed. The rinsing solution includes deionized water (DIW). An example of the cleaning step S10 includes removing particles and organic contaminants with SC1 solution, rinsing with DIW, removing the native oxide film with DHF, and rinsing with DIW in this order. However, the cleaning step S10 is not limited to this.

[0011] The ionic liquid coating step S20 includes supplying an ionic liquid to the surface of the substrate W, whose surface has been cleaned, to form an ionic liquid film 12 on the surface of the substrate W (see Figure 2(b)). The ionic liquid is deposited on the surface of the substrate W and penetrates into the pattern 11 formed on the surface of the substrate W, forming the ionic liquid film 12.

[0012] Ionic liquids contain both positive ions (cations) and negative ions (anions).

[0013] As the cation, those containing a hydrocarbon chain having 6 or more carbon atoms (hereinafter also referred to as "the first hydrocarbon chain") and having at least one hydrogen (H) atom of the first hydrocarbon chain replaced by a fluorine (F) atom can be used. Since the fluorine atom has a larger atomic radius than the hydrogen atom, the CF group has a larger excluded volume than the CH group. Therefore, an ionic liquid having a cation in which at least one hydrogen atom of the hydrocarbon chain is replaced by a fluorine atom has a lower density than an ionic liquid having a cation in which the hydrogen atoms of the hydrocarbon chain are not replaced by fluorine atoms. As a result, the intermolecular force between the molecules constituting the ionic liquid becomes smaller, and the surface tension of the ionic liquid becomes smaller. As a result, when drying the substrate W in the drying step S30 to remove the ionic liquid film 12 formed on the surface of the substrate W, pattern collapse in which adjacent patterns 11 overlap can be suppressed.

[0014] Preferably, in the first hydrocarbon chain, all hydrogen atoms bonded to the carbon (C) atom located at the tip are replaced by fluorine atoms. As a result, even if the CH group located at the tip is replaced by a CF group, it becomes nonpolar, so the intermolecular force with adjacent molecules becomes particularly small, and the surface tension of the ionic liquid can be made lower. In this case, in the first hydrocarbon chain, all hydrogen atoms bonded to the carbon atom located on the base end side rather than the carbon atom located at the tip may or may not be replaced by fluorine atoms. From the viewpoint of achieving a lower density, it is more preferable that all hydrogen atoms of the first hydrocarbon chain are replaced by fluorine atoms.

[0015] In addition to the first hydrocarbon chain, the cation may contain another hydrocarbon chain. From the viewpoint of reducing the surface tension, it is preferable that at least one hydrogen atom of the other hydrocarbon chain is replaced by a fluorine atom, similar to the first hydrocarbon chain, and more preferably all hydrogen atoms are replaced by fluorine atoms.

[0016] The central element of the cation may be, for example, nitrogen (N), phosphorus (P), aluminum (Al), or gallium (Ga).

[0017] The anion is not particularly limited, and for example, those containing a hydrocarbon chain (hereinafter also referred to as "second hydrocarbon chain") can be used. In this case, from the perspective of reducing the surface tension, it is preferable that at least one hydrogen atom in the second hydrocarbon chain is replaced by a fluorine atom, similar to the first hydrocarbon chain, and more preferably all hydrogen atoms are replaced by fluorine atoms.

[0018] The ionic liquid preferably has a surface tension at 25 °C of 30 mN / m or less, and more preferably a surface tension at 25 °C of 20 mN / m or less. Thereby, the ionic liquid easily enters into Pattern 11.

[0019] As the ionic liquid, those in which at least one hydrogen atom of the hydrocarbon chain of BHDP (tributyl(hexadecyl)phosphonium)-DSS (2,2-dimethyl-2-silapentane-5-sulfonate), BDDP (tributyl(dodecyl)phosphonium)-DSS, and BHDA (tributyl(hexadecyl)ammonium)-DSS is replaced by a fluorine atom can be preferably used. The ionic liquid may be one in which at least one hydrogen atom of the hydrocarbon chain of an ionic liquid obtained by replacing phosphorus (P), which is the central element of the cation (BHDP) of BHDP-DSS, with aluminum (Al) or gallium (Ga) is replaced by a fluorine atom. However, the ionic liquid is not limited thereto.

[0020] The drying step S30 includes drying and removing the ionic liquid film 12 formed on the surface of the substrate W (see Fig. 2(c)). The drying step S30 includes subjecting the substrate W on which the ionic liquid film 12 is formed to a supercritical treatment.

[0021] In supercritical fluid processing, a substrate W is placed inside a processing container, and then supercritical CO2 heated and pressurized to 31°C and 7.5 MPa or higher at a predetermined flow rate is introduced into the processing container. At this time, on the surface of the substrate W, the ionic liquid film 12 that has been deposited on the surface of the substrate W comes into contact with the supercritical CO2 and is extracted by the supercritical CO2, and the ionic liquid film 12 is removed from the surface of the substrate W. Furthermore, as time passes, the supercritical CO2 enters the pattern 11 formed on the surface of the substrate W, and extracts and removes the ionic liquid film 12 within the pattern 11. As a result, the ionic liquid film 12 that filled the pattern 11 is replaced by supercritical CO2 and removed from the surface of the substrate W.

[0022] However, if the ionic liquid does not sufficiently replace supercritical CO2 on the surface of the substrate W, and the surface tension of the ionic liquid film 12 is high, the pattern 11 may collapse when the surface tension of the ionic liquid film 12 remaining in the pattern 11 acts on the pattern 11. In contrast, according to this embodiment, the ionic liquid has a cation containing a hydrocarbon chain with 6 or more carbon atoms, and at least one hydrogen atom in the hydrocarbon chain is replaced by a fluorine atom. As a result, the surface tension of the ionic liquid is reduced, so even if the ionic liquid film 12 remains in the pattern 11, the collapse of the pattern can be suppressed.

[0023] In addition, in the drying process S30, instead of supercritical fluid treatment, the ionic liquid film 12 on the surface of the substrate W may be peeled off and removed by performing physical operations on the substrate W. Examples of physical operations include horizontal movement, rotation, and tilting of the substrate W. Alternatively, the ionic liquid may undergo a phase transition to reduce the viscosity of the ionic liquid film 12.

[0024] As described above, the substrate processing method according to the embodiment includes an ionic liquid coating step S20 in which an ionic liquid is supplied to the surface of a substrate W on which a pattern 11 is formed, and an ionic liquid film 12 is formed on the surface of the substrate W. The ionic liquid used in the ionic liquid coating step S20 has a cation containing a hydrocarbon chain with 6 or more carbon atoms, and at least one hydrogen atom in the hydrocarbon chain is replaced by a fluorine atom.

[0025] Since fluorine (F) atoms have a larger atomic radius than hydrogen (H) atoms, the excluded volume of a CF group is larger than that of a CH group. Therefore, an ionic liquid having a cation in which at least one hydrogen atom in the hydrocarbon chain is replaced by a fluorine atom will have a lower density than an ionic liquid having a cation in which the hydrogen atoms in the hydrocarbon chain are not replaced by fluorine atoms. This reduces the intermolecular forces between the molecules constituting the ionic liquid, and thus reduces the surface tension of the ionic liquid. As a result, when drying the substrate W and removing the ionic liquid film 12 formed on the surface of the substrate W, pattern collapse, where adjacent patterns overlap, can be suppressed.

[0026] Furthermore, according to the substrate processing method of the embodiment, after the cleaning step S10, the substrate W is dried using an ionic liquid instead of isopropyl alcohol (IPA). Since the ionic liquid can be used even at high temperatures, the amount of moisture absorbed is significantly less compared to IPA. Therefore, pattern deformation is less likely to occur. Also, since the ionic liquid does not vaporize, condensation due to vaporization, as with IPA, can be suppressed. In addition, since the ionic liquid is a conductive liquid, static electricity can be removed from the substrate W by the ionic liquid.

[0027] [Cleaning equipment] Referring to Figure 3, a cleaning apparatus 100 capable of performing the cleaning step S10 of the substrate processing method according to the embodiment will be described.

[0028] The cleaning device 100 is a single-wafer type device that cleans substrates W one by one, for example, by spin cleaning. The cleaning device 100 includes a chamber 110, a holding mechanism 120, a liquid discharge unit 130, a liquid receiving unit 140, and a control unit 190.

[0029] Chamber 110 forms a processing space. A drain port 111 and an exhaust port 112 are formed at the bottom of Chamber 110. Drain port 111 discharges the chemical solution and rinse solution from inside Chamber 110. Exhaust port 112 exhausts the inside of Chamber 110.

[0030] The holding mechanism 120 is located inside the chamber 110. The holding mechanism 120 holds the substrate W in a nearly horizontal position and rotates the substrate W by rotating around a vertical axis. A chemical supply passage 121 is formed inside the holding mechanism 120. The chemical supply passage 121 supplies a chemical solution and a rinsing solution to the back surface of the substrate W held by the holding mechanism 120. This performs a cleaning process on the back surface of the substrate W.

[0031] The liquid dispensing unit 130 includes an arm 131 and a nozzle 132. The arm 131 is configured to enter above the rotating substrate W. The nozzle 132 is provided at the tip of the arm 131. The nozzle 132 is configured to dispense a chemical solution and a rinse solution. The liquid dispensing unit 130 enters the arm 131 above the rotating substrate W and supplies the chemical solution and rinse solution from the nozzle 132 in a predetermined order. This performs a cleaning treatment on the surface of the substrate W. The cleaning treatment includes, for example, the removal of particles and organic contaminants with SC1 liquid, rinsing with DIW, the removal of the native oxide film with DHF, and rinsing with DIW in this order. However, the cleaning treatment is not limited to this.

[0032] The liquid receiving section 140 receives the chemical solution and rinse solution that spills or is shaken off from the substrate W, and discharges them through the drain port 141.

[0033] The control unit 190 processes computer-executable instructions that cause the cleaning device 100 to perform the cleaning process S10. The control unit 190 may be configured to control each element of the cleaning device 100 to perform the cleaning process S10. The control unit 190 includes, for example, a computer. The computer includes, for example, a CPU, a memory unit, and a communication interface.

[0034] [Coating equipment] Referring to Figure 4, a vacuum slit coater 200, which is an example of a coating apparatus capable of performing the ionic liquid coating step S20 of the substrate processing method according to the embodiment, will be described.

[0035] The vacuum slit coater 200 includes a chamber 210, a liquid supply unit 220, a liquid circulation unit 230, and a control unit 290.

[0036] Chamber 210 forms a sealed processing space 211 that houses the substrate W inside. A stage 212 is provided inside chamber 210. The stage 212 holds the substrate W in a substantially horizontal position. The stage 212 is connected to the upper end of a rotating shaft 214 that rotates by a drive mechanism 213, and is configured to be rotatable. A liquid receiving section 215, which opens upward, is provided around the lower part of the stage 212. The liquid receiving section 215 receives and stores ionic liquid that spills or is shaken off from the substrate W. The inside of chamber 210 is exhausted by an exhaust system (not shown) including a pressure control valve and a vacuum pump.

[0037] The liquid supply unit 220 includes a slit nozzle 221. The slit nozzle 221 moves horizontally above the substrate W, supplying ionic liquid for preventing drying from the liquid circulation unit 230 to the surface of the substrate W placed on the stage 212.

[0038] The liquid circulation unit 230 recovers the ionic liquid stored in the liquid receiving unit 215 and supplies it to the slit nozzle 221. The liquid circulation unit 230 includes a compressor 231, a stock tank 232, a carrier gas supply source 233, a cleaning unit 234, and pH sensors 235 and 236.

[0039] The compressor 231 is connected to the liquid receiving section 215 via piping 239a, and recovers the ionic liquid stored in the liquid receiving section 215 and compresses it to, for example, atmospheric pressure or higher. The compressor 231 is connected to the stock tank 232 via piping 239b, and transports the compressed ionic liquid to the stock tank 232 via piping 239b. Piping 239a is interposed with, for example, a valve and a flow controller (neither of which are shown). For example, by controlling the opening and closing of the valve, the transport of ionic liquid from the compressor 231 to the stock tank 232 is performed periodically.

[0040] The stock solution tank 232 stores the ionic liquid. One end of each pipe 239b to 239d is inserted into the stock solution tank 232. The other end of pipe 239b is connected to the compressor 231, and the ionic liquid compressed by the compressor 231 is supplied to the stock solution tank 232 via pipe 239b. The other end of pipe 239c is connected to the carrier gas supply source 233, and a carrier gas such as nitrogen (N2) gas is supplied to the stock solution tank 232 from the carrier gas supply source 233 via pipe 239c. The other end of pipe 239d is connected to the slit nozzle 221, and the ionic liquid in the stock solution tank 232 is transported to the slit nozzle 221 via pipe 239d along with the carrier gas. For example, valves and flow controllers (neither of which are shown) are interposed in pipes 239b to 239d.

[0041] The carrier gas supply source 233 is connected to the stock tank 232 via piping 239c and supplies carrier gas such as N2 gas to the stock tank 232 via piping 239c.

[0042] The cleaning unit 234 is interposed in the piping 239b. The cleaning unit 234 cleans the ionic liquid transported from the compressor 231. A drain pipe 239e is connected to the cleaning unit 234, and the ionic liquid whose properties have deteriorated is discharged through the drain pipe 239e. For example, the cleaning unit 234 controls whether to reuse or discharge the ionic liquid based on the detection value of the pH sensor 236. Alternatively, for example, the cleaning unit 234 may control whether to reuse or discharge the ionic liquid based on the detection value of the pH sensor 235. Alternatively, for example, the cleaning unit 234 may control whether to reuse or discharge the ionic liquid based on the detection values ​​of both the pH sensor 235 and the pH sensor 236.

[0043] The pH sensor 235 is installed in the compressor 231 and detects the hydrogen ion concentration (pH) of the ionic liquid inside the compressor 231.

[0044] The pH sensor 236 is located in the cleaning unit 234 and detects the hydrogen ion concentration (pH) of the ionic liquid in the cleaning unit 234.

[0045] The control unit 290 processes computer-executable instructions to cause the vacuum slit coater 200 to perform the ionic liquid coating process S20. The control unit 290 may be configured to control each element of the vacuum slit coater 200 to perform the ionic liquid coating process S20. The control unit 290 includes, for example, a computer. The computer includes, for example, a CPU, a memory unit, and a communication interface.

[0046] [Supercritical fluid processing device] Referring to Figure 5, a supercritical processing apparatus 300, which is an example of a drying apparatus capable of performing the drying step S30 of the substrate processing method according to the embodiment, will be described.

[0047] The supercritical fluid processing apparatus 300 is a device that removes ionic liquid, which is a liquid used to prevent drying, that adheres to the surface of the substrate W. The supercritical fluid processing apparatus 300 includes a processing container 310, a fluid supply unit 320, a discharge unit 330, and a control unit 390.

[0048] The processing container 310 forms a processing space capable of accommodating, for example, a substrate W with a diameter of 300 mm. The processing container 310 is equipped with a pressure gauge 311. The pressure gauge 311 detects the pressure inside the processing container 310 and outputs the detected value to the control unit 390.

[0049] The fluid supply unit 320 includes a fluid supply source 321, a fluid supply line 322, an on / off valve 323, a filter 324, and a flow control valve 325.

[0050] The fluid supply source 321 includes, for example, a CO2 cylinder for storing liquid CO2 and a booster pump, such as a syringe pump or diaphragm pump, for pressurizing the liquid CO2 supplied from the CO2 cylinder to a supercritical state. Figure 5 shows the CO2 cylinder and booster pump in general terms in terms of cylinder shape.

[0051] The fluid supply line 322 connects the processing vessel 310 and the fluid supply source 321. The fluid supply line 322 supplies supercritical CO2, which is a high-pressure fluid, from the fluid supply source 321 to the processing vessel 310.

[0052] The on-off valve 323, filter 324, and flow control valve 325 are interposed in the fluid supply line 322. The on-off valve 323 opens and closes in accordance with the supply and cessation of supercritical CO2 to the processing container 310. The filter 324 removes impurities contained in the supercritical CO2 flowing through the fluid supply line 322. The flow control valve 325 adjusts the flow rate of supercritical CO2 flowing through the fluid supply line 322. The supercritical CO2 supplied from the fluid supply source 321 has its flow rate adjusted by the flow control valve 325 and is supplied to the processing container 310. The flow control valve 325 is composed of, for example, a needle valve and also functions as a shut-off unit that blocks the supply of supercritical CO2 from the fluid supply source 321.

[0053] The discharge section 330 includes a discharge line 331, a pressure reducing valve 332, and a pressure controller 333. The discharge line 331 is connected to the side wall of the processing container 310. The discharge line 331 discharges the fluid inside the processing container 310. The pressure controller 333 is connected to the pressure reducing valve 332. The pressure controller 333 adjusts the opening of the pressure reducing valve 332 based on a pressure measurement taken from a pressure gauge 311 installed in the processing container 310 and a predetermined pressure setting.

[0054] The control unit 390 processes computer-executable instructions to cause the supercritical apparatus 300 to perform the drying process S30. The control unit 390 may be configured to control each element of the supercritical apparatus 300 to perform the drying process S30. The control unit 390 includes, for example, a computer. The computer includes, for example, a CPU, a memory unit, and a communication interface.

[0055] [Substrate Processing System] Referring to Figure 6, an example of a substrate processing system capable of implementing the substrate processing method according to the embodiment will be described. As shown in Figure 6, the substrate processing system PS1 is configured as an atmospheric device.

[0056] The substrate processing system PS1 includes an air transport module TM1, process modules PM11 to PM14, buffer modules BM11 and BM12, and a loader module LM1, among others.

[0057] The atmospheric transport module TM1 has a roughly rectangular shape in plan view. Process modules PM11 to PM14 are connected to two opposing sides of the atmospheric transport module TM1. Buffer modules BM11 and BM12 are connected to one of the other two opposing sides of the atmospheric transport module TM1. The atmospheric transport module TM1 has a transport chamber with an inert gas atmosphere, and a transport robot (not shown) is located inside. The transport robot is configured to rotate, extend and retract, and move up and down. The transport robot transports the substrate W based on operation instructions output by the control unit CU1, which will be described later. For example, the transport robot holds the substrate W with a fork located at its tip and transports the substrate W between buffer modules BM11 and BM12 and process modules PM11 to PM14. The fork is also called a pick or end effector.

[0058] Process modules PM11 to PM14 have a processing chamber and a stage (not shown) located inside. Process modules PM11 to PM14 include the aforementioned cleaning device 100 and supercritical fluid processing device 300. Process modules PM11 to PM14 may also include devices other than the cleaning device 100 and supercritical fluid processing device 300. The atmospheric transport module TM1 and process modules PM11 to PM14 are separated by a gate valve G11 that can be opened and closed.

[0059] Buffer modules BM11 and BM12 are positioned between the air transport module TM1 and the loader module LM1. Buffer modules BM11 and BM12 have internally positioned stages. The substrate W is transferred between the air transport module TM1 and the loader module LM1 via buffer modules BM11 and BM12. Buffer modules BM11 and BM12 are separated from the air transport module TM1 by a gate valve G12 that can be opened and closed. Buffer modules BM11 and BM12 are separated from the loader module LM1 by a gate valve G13 that can be opened and closed.

[0060] The loader module LM1 is positioned opposite the atmospheric transport module TM1. The loader module LM1 is, for example, an EFEM (Equipment Front End Module). The loader module LM1 is rectangular in shape, equipped with an FFU (Fan Filter Unit), and is an atmospheric transport chamber maintained at atmospheric pressure. Two buffer modules BM11 and BM12 are connected to one side of the loader module LM1 along its longitudinal direction. Load ports LP11 to LP14 are connected to the other side of the loader module LM1 along its longitudinal direction. Containers (not shown) for accommodating multiple (e.g., 25) substrates W are placed on the load ports LP11 to LP14. The containers are, for example, FOUPs (Front-Opening Unified Pods). A transport robot (not shown) for transporting the substrates W is positioned inside the loader module LM1. The transport robot is configured to move along the longitudinal direction of the loader module LM1 and to be able to rotate, extend and retract, and move up and down. The transport robot transports the substrate W based on the operation instructions output by the control unit CU1. For example, the transport robot holds the substrate W with a fork located at its tip and transports the substrate W between the load ports LP11~LP14 and the buffer modules BM11, BM12.

[0061] The PCB processing system PS1 is equipped with a control unit CU1. The control unit CU1 may be, for example, a computer. The control unit CU1 includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), auxiliary storage device, etc. The CPU operates based on a program stored in the ROM or auxiliary storage device and controls each part of the PCB processing system PS1.

[0062] Referring to Figure 7, another example of a substrate processing system capable of implementing the substrate processing method according to the embodiment will be described. As shown in Figure 7, the substrate processing system PS2 is configured as a vacuum device.

[0063] The substrate processing system PS2 includes a vacuum transport module TM2, process modules PM21 to PM24, load lock modules LL21 and LL22, and a loader module LM2, among others.

[0064] The vacuum transport module TM2 has a roughly rectangular shape in plan view. Process modules PM21 to PM24 are connected to two opposing sides of the vacuum transport module TM2. Load lock modules LL21 and LL22 are connected to one of the other two opposing sides of the vacuum transport module TM2. The vacuum transport module TM2 has a vacuum chamber with a vacuum atmosphere, and a transport robot (not shown) is located inside. The transport robot is configured to be able to rotate, extend and retract, and move up and down. The transport robot transports the substrate W based on operation instructions output by the control unit CU2, which will be described later. For example, the transport robot holds the substrate W with a fork located at its tip and transports the substrate W between the load lock modules LL21 and LL22 and the process modules PM21 to PM24.

[0065] Process modules PM21 to PM24 have a processing chamber and a stage (not shown) located inside. Process modules PM21 to PM24 include the vacuum slit coater 200 described above. Process modules PM21 to PM24 may also include equipment other than the vacuum slit coater 200. The vacuum transport module TM2 and process modules PM21 to PM24 are separated by a gate valve G21 that can be opened and closed.

[0066] The load lock modules LL21 and LL22 are positioned between the vacuum transport module TM2 and the loader module LM2. Each load lock module LL21 and LL22 has a variable internal pressure chamber that can be switched between vacuum and atmospheric pressure. Each load lock module LL21 and LL22 also has an internal stage (not shown). When loading a substrate W from the loader module LM2 to the vacuum transport module TM2, the load lock modules LL21 and LL22 maintain atmospheric pressure inside to receive the substrate W from the loader module LM2, then reduce the internal pressure to load the substrate W into the vacuum transport module TM2. When unloading a substrate W from the vacuum transport module TM2 to the loader module LM2, the load lock modules LL21 and LL22 maintain a vacuum inside to receive the substrate W from the vacuum transport module TM2, then increase the internal pressure to atmospheric pressure to load the substrate W into the loader module LM2. The load lock modules LL21 and LL22 are separated from the vacuum transport module TM2 by a gate valve G22 that can be opened and closed. The load lock modules LL21 and LL22 and the loader module LM2 are separated by a gate valve G23 that can be opened and closed.

[0067] The loader module LM2 is positioned opposite the vacuum transport module TM2. The loader module LM2 is, for example, an EFEM. The loader module LM2 is a rectangular parallelepiped, equipped with an FFU, and is an atmospheric transport chamber maintained at atmospheric pressure. Two load lock modules LL21 and LL22 are connected to one side of the loader module LM2 along its longitudinal direction. Load ports LP21 to LP24 are connected to the other side of the loader module LM2 along its longitudinal direction. Containers (not shown) for containing multiple (e.g., 25) substrates W are placed on the load ports LP21 to LP24. The containers are, for example, FOUPs. A transport robot (not shown) for transporting the substrates W is located inside the loader module LM2. The transport robot is configured to be movable along the longitudinal direction of the loader module LM2 and is also configured to be able to rotate, extend and retract, and move up and down. The transport robot transports the substrates W based on operation instructions output by the control unit CU2. For example, the transport robot holds the substrate W with a fork positioned at its tip and transports the substrate W between load ports LP21~LP24 and load lock modules LL21, LL22.

[0068] The circuit board processing system PS2 is equipped with a control unit CU2. The control unit CU2 may be, for example, a computer. The control unit CU2 includes a CPU, RAM, ROM, auxiliary storage device, etc. The CPU operates based on a program stored in the ROM or auxiliary storage device and controls each part of the circuit board processing system PS2.

[0069] [Analysis results] Referring to Figures 8 to 10, the results of the simulation analysis of the surface tension of ionic liquids are explained. In the simulation, the surface tension at 25°C was calculated for ionic liquids A1, A2, B1, and B2. In addition, the surface tension at 100°C was also calculated for ionic liquids A2 and B2.

[0070] Ionic liquid A1 is an ionic liquid represented by the chemical formula in Figure 8, and is BHDP-DSS. Ionic liquid A2 is an ionic liquid obtained by replacing all hydrogen atoms in the hydrocarbon chain of ionic liquid A1 with fluorine atoms. Ionic liquid B1 is an ionic liquid represented by the chemical formula in Figure 9, and is BHDA-DSS. Ionic liquid B2 is an ionic liquid obtained by replacing all hydrogen atoms in the hydrocarbon chain of ionic liquid B1 with fluorine atoms.

[0071] Figure 10 shows the results of simulations calculating the surface tension of ionic liquids. As shown in Figure 10, the surface tension of ionic liquid A1 at 25°C is 29 mN / m, the surface tension of ionic liquid A2 at 25°C is 22 mN / m, and the surface tension of ionic liquid A2 at 100°C is 15 mN / m. From these results, it is shown that the surface tension of an ionic liquid can be lowered by replacing the hydrogen atoms in the hydrocarbon chain of the ionic liquid BHDP-DSS with fluorine atoms. Furthermore, it is shown that the surface tension of an ionic liquid can be lowered even further by replacing the hydrogen atoms in the hydrocarbon chain of the ionic liquid BHDP-DSS with fluorine atoms and increasing the temperature of the ionic liquid. The surface tension of IPA at 25°C is approximately 20 mN / m.

[0072] Furthermore, as shown in Figure 10, the surface tension of ionic liquid B1 at 25°C is 39 mN / m, the surface tension of ionic liquid B2 at 25°C is 19 mN / m, and the surface tension of ionic liquid B2 at 100°C is 17.5 mN / m. These results demonstrate that the surface tension of ionic liquids can be lowered by replacing the hydrogen atoms in the hydrocarbon chain of BHDA-DSS with fluorine atoms. It also demonstrates that the surface tension of ionic liquids can be further lowered by replacing the hydrogen atoms in the hydrocarbon chain of BHDA-DSS with fluorine atoms and increasing the temperature of the ionic liquid.

[0073] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of Symbols]

[0074] 11 patterns 12 Ionic liquid membranes W board S20 Ionic liquid coating process

Claims

1. A step of supplying an ionic liquid to the surface of a substrate on which a pattern has been formed, and forming a film of the ionic liquid on the surface of the substrate, A step of subjecting the substrate on which the ionic liquid film is formed to supercritical treatment, It has, The ionic liquid has a cation containing a hydrocarbon chain with six or more carbon atoms. The hydrocarbon chain has at least one hydrogen atom replaced by a fluorine atom. Substrate processing method.

2. The aforementioned hydrocarbon chain includes a carbon atom at the tip, in which all bonded hydrogen atoms are replaced by fluorine atoms. The substrate processing method according to claim 1.

3. The hydrocarbon chain includes a carbon atom at the base end, in which all bonded hydrogen atoms are not replaced by fluorine atoms. The substrate processing method according to claim 1 or 2.

4. The hydrocarbon chain in which all hydrogen atoms are replaced by fluorine atoms, The substrate processing method according to claim 1 or 2.

5. The central element of the cation is nitrogen (N), phosphorus (P), aluminum (Al), or gallium (Ga). A substrate processing method according to any one of claims 1 to 4.

6. The surface tension of the ionic liquid at 25°C is 30 mN / m or less. A substrate processing method according to any one of claims 1 to 5.

7. The ionic liquid is obtained by replacing at least one hydrogen atom in the hydrocarbon chain of BHDP-DSS with a fluorine atom. A substrate processing method according to any one of claims 1 to 6.

8. The process includes supplying an ionic liquid to the surface of a substrate on which a pattern is formed, and forming a film of the ionic liquid on the surface of the substrate. The ionic liquid is obtained by replacing at least one hydrogen atom in the hydrocarbon chain of BHDP-DSS with a fluorine atom. Substrate processing method.

9. An ionic liquid for forming a film on the surface of a substrate on which a pattern has been formed, The ionic liquid is obtained by replacing at least one hydrogen atom in the hydrocarbon chain of BHDP-DSS with a fluorine atom. Ionic liquid.

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