Substrate processing method and substrate processing system

Abstract

To provide technique enabling formation of a protective film that has high barrier properties to oxidized gas and is easy to remove.SOLUTION: A substrate processing method has the steps of: preparing a substrate with a target film exposed on the surface; supplying the surface of the substrate with an ionic liquid including oxoacid structure having a carbon number of 6 or more at a first temperature to form a liquid film on the surface of the target film; cooling the substrate to a second temperature lower than the first temperature to solidify the liquid film to form a solid film; and supplying the substrate with a polar solvent to remove the solid film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing method and a substrate processing system. [Background technology]

[0002] A technique is known in which a liquid material containing an ionic liquid is applied onto a substrate to form a protective film (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 220883 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique for forming a protective film that has high barrier properties against oxidizing gases and is easy to remove. [Means for solving the problem]

[0005] A substrate processing method according to one embodiment of the present disclosure includes the steps of preparing a substrate having a target film exposed on its surface; supplying an ionic liquid containing an oxo acid structure having six or more carbon atoms to the surface of the substrate at a first temperature to form a liquid film on the surface of the target film; cooling the substrate to a second temperature lower than the first temperature to solidify the liquid film to form a solid film; and supplying a polar solvent to the substrate to remove the solid film. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to form a protective film that has high blocking properties against oxidizing gases and is easy to remove. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a flowchart illustrating a substrate processing method according to an embodiment. [Figure 2] 1 is a cross-sectional view illustrating a substrate processing method according to an embodiment; [Figure 3] Schematic diagram showing an example of a coating device [Figure 4] Schematic diagram showing an example of a substrate processing system [Figure 5] 1 is a schematic diagram illustrating another example of a substrate processing system. [Figure 6] FIG. 1 is a diagram showing an example of a process including a substrate processing method. [Figure 7] Cross-sectional view (1) showing an example of a process including a substrate processing method [Figure 8] Cross-sectional view (2) showing an example of a process including a substrate processing method [Figure 9] Cross-sectional view (3) showing an example of a process including a substrate processing method [Figure 10] Cross-sectional view (4) showing an example of a process including a substrate processing method. [Figure 11] Cross-sectional view (5) showing an example of a process including a substrate processing method. [Figure 12] Cross-sectional view (6) showing an example of a process including a substrate processing method [Figure 13] Cross-sectional view (7) showing an example of a process including a substrate processing method [Figure 14] Cross-sectional view (8) showing an example of a process including a substrate processing method [Figure 15] Cross-sectional view (9) showing an example of a process including a substrate processing method [Figure 16] Cross-sectional view showing the method for preparing a sample for solid film evaluation [Figure 17] Cross-sectional view showing the method for preparing a sample for liquid film evaluation [Figure 18] Diagram showing the oxidation state of the copper film surface protected by a solid film [Figure 19] Diagram showing the oxidation state of the copper film surface protected by a liquid film DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the accompanying drawings, the same or corresponding reference numerals are used to designate the same or corresponding members or components, and redundant descriptions will be omitted.

[0009] [Substrate Processing Method] A substrate processing method according to an embodiment will be described with reference to Figures 1 and 2. As shown in Figure 1, the substrate processing method according to the embodiment includes a preparation step S10, a liquid film formation step S20, a solid film formation step S30, and a removal step S40.

[0010] The preparation step S10 includes preparing a substrate W having a pattern 11 on its surface covered with a metal film 12 (see FIG. 2(a)). The substrate W is, for example, a semiconductor wafer. The pattern 11 is, for example, a trench or a hole. The metal film 12 is exposed on the surface of the substrate W. The metal film 12 may be, for example, a copper (Cu) film, an aluminum (Al) film, a cobalt (Co) film, a ruthenium (Ru) film, or a tantalum (Ta) film. The metal film 12 is formed by, for example, a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method such as a sputtering method. However, the method for forming the metal film 12 is not limited thereto. The method may include removing a native oxide film on the surface of the substrate W at least either before or after forming the metal film 12.

[0011] The liquid film forming step S20 is performed after the preparation step S10. The liquid film forming step S20 is preferably performed without exposing the substrate W to an oxygen-containing atmosphere after the metal film 12 is formed, so as to prevent oxidation of the metal film 12 exposed on the surface of the substrate W. The liquid film forming step S20 is performed in an oxygen-free atmosphere, such as a vacuum atmosphere or an inert gas atmosphere.

[0012] The liquid film forming step S20 includes supplying an ionic liquid to the surface of the substrate W at a first temperature to form a film of the ionic liquid (hereinafter referred to as "liquid film 13") on the surface of the metal film 12 (see Figure 2(b)). The first temperature may be any temperature at which the ionic liquid can be applied in a liquid phase, and may be, for example, a temperature higher than the freezing point of the ionic liquid. When supplying the ionic liquid, the substrate W may be heated to a predetermined temperature. By heating the substrate W, the ionic liquid remains in a liquid phase on the surface of the substrate W, making it easier for the ionic liquid to spread over the entire surface of the substrate W. The predetermined temperature may be, for example, the same temperature as the first temperature. It is not necessary to heat the substrate W when supplying the ionic liquid.

[0013] The ionic liquid contains an oxo acid structure having six or more carbon atoms. When the carbon number is six or more, the ionic liquid exhibits low viscosity at relatively low temperatures, allowing the ionic liquid to be applied to the substrate W at relatively low temperatures. The carbon number is preferably eight or more. In this case, the ionic liquid can be easily applied to the substrate W at low temperatures. When the ionic liquid contains an oxo acid structure, the solid film 14, which will be described later, can be easily removed. Details will be described later.

[0014] When an ionic liquid is used to form a protective film in a front end of line (FEOL) process, it is preferable that the ionic liquid does not contain metal ions in order to prevent diffusion of metals into the film to be protected, etc. If the ionic liquid contains metal ions, the metal ions contained in the ionic liquid may diffuse into the film to be protected during heat treatment in the FEOL process, degrading the characteristics of the semiconductor device.

[0015] The oxo acid structure may be present in at least one of a cation and anion. Examples of the oxo acid structure include a carboxylate anion having 6 or more carbon atoms. Examples of the carboxylate anion having 6 or more carbon atoms include a decanoate anion (CH 19 COO -When the ionic liquid contains a carboxylic acid anion having 6 or more carbon atoms, various cations can be used. Examples of the cation include phosphate cation and sulfate cation.

[0016] A specific example of the ionic liquid is trihexyltetradecylphosphonium decanoate (THTDP-DcO). When the ionic liquid is THTDP-DcO, the first temperature is preferably 50°C or higher and 200°C or lower, and more preferably 70°C or higher and 90°C or lower.

[0017] The solid film forming step S30 is performed after the liquid film forming step S20. The solid film forming step S30 is performed in an oxygen-free atmosphere, such as a vacuum atmosphere or an inert gas atmosphere. The solid film forming step S30 may be performed in the same chamber as the liquid film forming step S20, or in a chamber different from the liquid film forming step S20.

[0018] The solid film forming step S30 includes cooling the substrate W to a second temperature and solidifying the liquid film 13 to form a solid film 14 (see FIG. 2(c)). The solid film 14 has a higher blocking ability against oxidizing gases such as oxygen gas than the liquid film 13. Therefore, even if the substrate W on which the solid film 14 has been formed is exposed to an atmosphere containing oxygen, the solid film 14 prevents the oxidizing gas from reaching the metal film 12. As a result, oxidation of the metal film 12 is suppressed. In this way, the solid film 14 functions as a protective film that protects the metal film 12 from oxidizing gases. The reason why the solid film 14 has a higher blocking ability against oxidizing gases than the liquid film 13 is thought to be that the liquid film 13 becomes solid and crystallizes, thereby reducing the diffusion path for oxygen. The second temperature is a temperature lower than the first temperature. The second temperature may be any temperature at which the liquid film 13 can be solidified, for example, a temperature below the freezing point of the ionic liquid. When the ionic liquid used in the liquid film forming step S20 is THTDP-DcO, the second temperature is preferably 20°C or higher and 30°C or lower, and more preferably 25°C.

[0019] The removal step S40 is performed after the solid film formation step S30. A step of exposing the substrate W to an atmosphere including air may be included between the solid film formation step S30 and the removal step S40. The step of exposing the substrate W to an atmosphere including air may include, for example, transporting the substrate W in an atmosphere including air by a transport device from an apparatus where the solid film formation step S30 is performed to an apparatus where the removal step S40 is performed. The removal step S40 is preferably performed immediately before the next step, such as a film formation step. This prevents the surface of the metal film 12 from being oxidized by the solid film 14 until immediately before the next step is performed.

[0020] The removal step S40 includes supplying a polar solvent to the substrate W and removing the solid film 14 (see FIG. 2(d)). The removal step S40 includes esterifying at least a portion of the oxo acid structures contained in the solid film 14. When the ionic liquid contains an oxo acid structure, supplying a polar solvent to the solid film 14 causes at least a portion of the oxo acid structures contained in the solid film 14 to be esterified by a condensation reaction with the polar solvent. When at least a portion of the oxo acid structures are esterified, the polarity changes and the hydrophobicity increases, thereby weakening the bond with the metal film 12 and making the solid film 14 more likely to peel off from the surface of the metal film 12. In this way, when the ionic liquid contains an oxo acid structure, the solid film 14 obtained by solidifying the liquid film 13 is used as a protective film, and then the solid film 14 can be removed by a simple method of supplying a polar solvent to the solid film 14 in the removal step S40. Furthermore, since the solid film 14 can be removed in a solid state without returning it to a liquid phase, when foreign matter such as particles is attached to the surface of the substrate W, the attached matter can be removed simultaneously with the solid film 14. Examples of polar solvents include alcohol-based solvents such as methanol, ethanol, propanol, and isopropyl alcohol.

[0021] The removal step S40 is preferably performed in an inert gas atmosphere. This can prevent oxidation of the metal film 12 that is exposed by removing the solid film 14. The inert gas atmosphere may be, for example, an argon atmosphere. If the polar solvent is a solvent that does not evaporate in a vacuum atmosphere, the removal step S40 may be performed in a vacuum atmosphere. Alternatively, the solid film 14 may be removed by ashing before supplying the polar solvent to the substrate W.

[0022] As described above, according to the substrate processing method of the embodiment, an ionic liquid containing an oxo acid structure having six or more carbon atoms is supplied to the surface of the substrate W at a first temperature to form a liquid film 13 on the surface of the metal film 12. Next, the substrate W is cooled to a second temperature lower than the first temperature, and the liquid film 13 is solidified to form a solid film 14. This makes it possible to form a protective film that has high barrier properties against oxidizing gases and is easy to remove.

[0023] [Coating device] A vacuum slit coater 200, which is an example of a coating apparatus, will be described with reference to Figure 3. The vacuum slit coater 200 can perform the liquid film forming step S20 and the solid film forming step S30 of the substrate processing method according to the embodiment.

[0024] The vacuum slit coater 200 includes a chamber 210 , a liquid supply unit 220 , a liquid circulation unit 230 , a heating unit 240 , and a control unit 290 .

[0025] The chamber 210 forms a sealed processing space 211 that accommodates the substrate W therein. A stage 212 is provided within the chamber 210. The stage 212 holds the substrate W in a substantially horizontal position. The stage 212 is rotatably connected to the upper end of a rotation shaft 214 that is rotated by a drive mechanism 213. A liquid receiving section 215 that is open on the upper side is provided around the lower periphery of the stage 212. The liquid receiving section 215 receives and stores the ionic liquid that spills or is shaken off from the substrate W. The interior of the chamber 210 is evacuated by an exhaust system (not shown) that includes a pressure control valve, a vacuum pump, etc.

[0026] The liquid supply unit 220 includes a slit nozzle 221. The slit nozzle 221 moves horizontally above the substrate W to supply the ionic liquid from the liquid circulation unit 230 onto the surface of the substrate W placed on the stage 212.

[0027] Liquid circulation unit 230 recovers the ionic liquid stored in liquid receiving unit 215 and supplies it to slit nozzle 221. Liquid circulation unit 230 includes a compressor 231, a raw liquid tank 232, a carrier gas supply source 233, a cleaning unit 234, and pH sensors 235 and 236.

[0028] Compressor 231 is connected to liquid receiver 215 via pipe 239a, recovers the ionic liquid stored in liquid receiver 215, and compresses it to, for example, atmospheric pressure or higher. Compressor 231 is connected to raw liquid tank 232 via pipe 239b, and transports the compressed ionic liquid to raw liquid tank 232 via pipe 239b. Pipe 239a is provided with, for example, a valve and a flow rate controller (neither of which are shown). For example, the ionic liquid is transported from compressor 231 to raw liquid tank 232 periodically by controlling the opening and closing of a valve.

[0029] The raw liquid tank 232 stores an ionic liquid. One ends of pipes 239b to 239d are inserted into the raw liquid tank 232. The other end of pipe 239b is connected to compressor 231, and the ionic liquid compressed by compressor 231 is supplied to the raw liquid tank 232 via pipe 239b. The other end of pipe 239c is connected to carrier gas supply source 233, and a carrier gas such as nitrogen (N2) gas is supplied to the raw liquid tank 232 from carrier gas supply source 233 via pipe 239c. The other end of pipe 239d is connected to slit nozzle 221, and the ionic liquid in the raw liquid tank 232 is transported together with the carrier gas to slit nozzle 221 via pipe 239d. For example, valves and flow rate controllers (neither of which are shown) are installed in pipes 239b to 239d.

[0030] The carrier gas supply source 233 is connected to the raw liquid tank 232 via a pipe 239c, and supplies a carrier gas such as N2 gas to the raw liquid tank 232 via the pipe 239c.

[0031] Cleaning unit 234 is provided in pipe 239b. Cleaning unit 234 cleans the ionic liquid transported from compressor 231. A drain pipe 239e is connected to cleaning unit 234, and ionic liquid with deteriorated properties is discharged via drain pipe 239e. For example, cleaning unit 234 controls whether to reuse or discharge the ionic liquid based on the detection value of pH sensor 236. Furthermore, for example, cleaning unit 234 may control whether to reuse or discharge the ionic liquid based on the detection value of pH sensor 235. Furthermore, for example, cleaning unit 234 may control whether to reuse or discharge the ionic liquid based on the detection values ​​of pH sensors 235 and 236.

[0032] The pH sensor 235 is provided in the compressor 231 and detects the hydrogen ion exponent (pH) of the ionic liquid in the compressor 231 .

[0033] The pH sensor 236 is provided in the cleaning section 234 and detects the hydrogen ion exponent (pH) of the ionic liquid in the cleaning section 234 .

[0034] The heating unit 240 includes a pipe heater 241 and a heat lamp 242. The pipe heater 241 is attached to the pipe 239d. The pipe heater 241 heats the ionic liquid flowing through the pipe 239d to a first temperature. As a result, the liquefied ionic liquid is applied to the substrate W on the stage 212. The heat lamp 242 is provided above the stage 212. The heat lamp 242 heats the substrate W placed on the stage 212 to a predetermined temperature by irradiating it with light in the absorption wavelength range of the substrate W, for example, infrared light. The predetermined temperature may be the same as the first temperature, for example. A plurality of heat lamps 242 may be provided.

[0035] The control unit 290 processes computer-executable instructions that cause the vacuum slit coater 200 to perform the liquid film formation process S20 and the solid film formation process S30. The control unit 290 can be configured to control each element of the vacuum slit coater 200 to perform the liquid film formation process S20 and the solid film formation process S30. The control unit 290 includes, for example, a computer. The computer includes, for example, a CPU, a storage unit, and a communication interface.

[0036] An example of the case where the liquid film forming step S20 and the solid film forming step S30 are performed in the vacuum slit coater 200 will be described.

[0037] First, the substrate W is loaded into the chamber 210 through a loading / unloading port (not shown) and placed on the stage 212. Next, the substrate W on the stage 212 is heated to a predetermined temperature by the heat lamps 242. Next, while the stage 212 is rotated by the drive mechanism 213, the slit nozzle 221 applies an ionic liquid to the surface of the substrate W on the stage 212. At this time, the ionic liquid is supplied to the slit nozzle 221 while being adjusted to a first temperature by the pipe heater 241. As a result, the liquefied ionic liquid is applied to the substrate W on the stage 212, and the ionic liquid spreads over the entire surface of the substrate W. Furthermore, since the ionic liquid is maintained in a liquid phase on the surface of the substrate W by heating the substrate W by the heat lamps 242, the ionic liquid easily spreads over the entire surface of the substrate W. In this way, a liquid film 13 can be formed over the entire surface of the substrate W. Next, heating of the substrate W by the heat lamps 242 is stopped. As a result, the substrate W is cooled to the second temperature, and the liquid film 13 solidifies to form a solid film 14.

[0038] In the above example, the case where the ionic liquid is circulated and reused is described, but the present invention is not limited to this. For example, the ionic liquid does not have to be circulated. Furthermore, in the above example, the case where the substrate W on the stage 212 is cooled by stopping heating by the heat lamps 242 is described, but the present invention is not limited to this. For example, a cooling mechanism for cooling the substrate W on the stage 212 may be provided. The cooling mechanism may be air-cooled or water-cooled.

[0039] [Substrate Processing System] An example of a substrate processing system capable of carrying out a substrate processing method according to an embodiment will be described with reference to Fig. 4. As shown in Fig. 4, the substrate processing system PS1 is configured as an atmospheric device.

[0040] The substrate processing system PS1 includes an atmospheric transfer module TM1, process modules PM11 to PM14, buffer modules BM11 and BM12, a loader module LM1, and the like.

[0041] The atmospheric transfer module TM1 has a substantially rectangular shape in a plan view. The atmospheric transfer module TM1 has two opposing side surfaces to which the process modules PM11 to PM14 are connected. Of the other two opposing side surfaces of the atmospheric transfer module TM1, the buffer modules BM11 and BM12 are connected to one side surface. The atmospheric transfer module TM1 has a transfer chamber with an inert gas atmosphere, and a transfer robot (not shown) is disposed inside. The transfer robot is configured to be able to freely rotate, extend, and move up and down. The transfer robot transfers the substrate W based on operation instructions output by a control unit CU1, which will be described later. For example, the transfer robot holds the substrate W with forks disposed at the tip and transfers the substrate W between the buffer modules BM11 and BM12 and the process modules PM11 to PM14. The forks are also called picks or end effectors.

[0042] Each of the process modules PM11 to PM14 has a processing chamber and a stage (not shown) disposed therein. The atmospheric transfer module TM1 and the process modules PM11 to PM14 are separated by a gate valve G11 that can be opened and closed.

[0043] The buffer modules BM11 and BM12 are disposed between the atmospheric transfer module TM1 and the loader module LM1. The buffer modules BM11 and BM12 have stages disposed therein. The substrates W are transferred between the atmospheric transfer module TM1 and the loader module LM1 via the buffer modules BM11 and BM12. The buffer modules BM11 and BM12 and the atmospheric transfer module TM1 are separated by an openable and closable gate valve G12. The buffer modules BM11 and BM12 and the loader module LM1 are separated by an openable and closable gate valve G13.

[0044] The loader module LM1 is disposed opposite the atmospheric transfer module TM1. The loader module LM1 is, for example, an Equipment Front End Module (EFEM). The loader module LM1 is a rectangular parallelepiped atmospheric transfer chamber equipped with an FFU (Fan Filter Unit) and maintained at atmospheric pressure. Two buffer modules BM11 and BM12 are connected to one longitudinal side of the loader module LM1. Load ports LP11 to LP14 are connected to the other longitudinal side of the loader module LM1. Containers (not shown) that accommodate a plurality of substrates W (e.g., 25 substrates) are placed on the load ports LP11 to LP14. The containers are, for example, Front-Opening Unified Pods (FOUPs). A transfer robot (not shown) that transfers the substrates W is disposed within the loader module LM1. The transfer robot is configured to be movable along the longitudinal direction of the loader module LM1 and is also configured to be rotatable, extendable, and elevating. The transport robot transports the substrate W based on an operation instruction output by the control unit CU1. For example, the transport robot holds the substrate W with a fork disposed at the tip, and transports the substrate W between the load ports LP11 to LP14 and the buffer modules BM11 and BM12.

[0045] The substrate processing system PS1 is provided 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), an auxiliary storage device, etc. The CPU operates based on a program stored in the ROM or the auxiliary storage device, and controls each part of the substrate processing system PS1.

[0046] Another example of a substrate processing system capable of carrying out a substrate processing method according to an embodiment will be described with reference to Fig. 5. As shown in Fig. 5, the substrate processing system PS2 is configured as a vacuum device.

[0047] The substrate processing system PS2 includes a vacuum transfer module TM2, process modules PM21 to PM24, load lock modules LL21 and LL22, a loader module LM2, and the like.

[0048] The vacuum transfer module TM2 has a substantially rectangular shape in a plan view. The vacuum transfer module TM2 has two opposing side surfaces to which process modules PM21 to PM24 are connected. Of the other two opposing side surfaces of the vacuum transfer module TM2, load lock modules LL21 and LL22 are connected to one side surface. The vacuum transfer module TM2 has a vacuum chamber with a vacuum atmosphere, and a transfer robot (not shown) is disposed inside. The transfer robot is configured to be able to rotate, extend, and move up and down freely. The transfer robot transfers the substrate W based on operation instructions output by a control unit CU2, which will be described later. For example, the transfer robot holds the substrate W with forks disposed at its tip, and transfers the substrate W between the load lock modules LL21 and LL22 and the process modules PM21 to PM24.

[0049] Each of the process modules PM21 to PM24 has a processing chamber and a stage (not shown) disposed therein. Each of the process modules PM21 to PM24 includes the above-mentioned vacuum slit coater 200. The vacuum transfer module TM2 and the process modules PM21 to PM24 are separated by a gate valve G21 that can be opened and closed.

[0050] The load lock modules LL21 and LL22 are disposed between the vacuum transfer module TM2 and the loader module LM2. The load lock modules LL21 and LL22 have an internal pressure variable chamber whose interior can be switched between vacuum and atmospheric pressure. The load lock modules LL21 and LL22 have a stage (not shown) disposed therein. When transferring a substrate W from the loader module LM2 to the vacuum transfer module TM2, the load lock modules LL21 and LL22 maintain the interior at atmospheric pressure while receiving the substrate W from the loader module LM2, and then reduce the interior pressure before transferring the substrate W into the vacuum transfer module TM2. When transferring a substrate W from the vacuum transfer module TM2 to the loader module LM2, the load lock modules LL21 and LL22 maintain the interior at vacuum while receiving the substrate W from the vacuum transfer module TM2, and then increase the interior pressure to atmospheric pressure before transferring the substrate W into the loader module LM2. The load lock modules LL21 and LL22 and the vacuum transfer module TM2 are separated 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.

[0051] The loader module LM2 is disposed opposite the vacuum transfer module TM2. The loader module LM2 is, for example, an EFEM. The loader module LM2 is a rectangular parallelepiped atmospheric transfer chamber equipped with an FFU and maintained at atmospheric pressure. Two load lock modules LL21 and LL22 are connected to one longitudinal side of the loader module LM2. Load ports LP21 to LP24 are connected to the other longitudinal side of the loader module LM2. Containers (not shown) that accommodate multiple (e.g., 25) substrates W are placed on the load ports LP21 to LP24. The containers are, for example, FOUPs. A transfer robot (not shown) that transfers the substrates W is disposed within the loader module LM2. The transfer robot is configured to be movable along the longitudinal direction of the loader module LM2 and is also configured to be freely rotatable, extendable, and elevating. The transfer robot transfers the substrates W based on operation instructions output by the control unit CU2. For example, the transfer robot holds the substrate W with a fork disposed at the tip, and transfers the substrate W between the load ports LP21 to LP24 and the load lock modules LL21 and LL22.

[0052] The substrate processing system PS2 is provided with a control unit CU2. The control unit CU2 may be, for example, a computer. The control unit CU2 includes a CPU, RAM, ROM, an auxiliary storage device, etc. The CPU operates based on a program stored in the ROM or the auxiliary storage device, and controls each unit of the substrate processing system PS2.

[0053] [Semiconductor manufacturing process including substrate processing method] An example of a semiconductor manufacturing process to which the substrate processing method according to the embodiment can be applied will be described with reference to FIGS.

[0054] First, a copper film 22 is formed on the surface of a substrate 21 by electroless plating (see FIG. 7). The thickness of the copper film is, for example, 0.5 μm. Next, a resist film 23 is formed on the copper film 22 by coating (see FIG. 8).

[0055] Next, the substrate 21 on which the resist film 23 has been formed is transported via a loader to an exposure device in the atmospheric device, where an exposure process is performed to expose a part of the resist film 23 using a photomask 24 (see FIG. 9). The exposure device may be, for example, any of the process modules PM11 to PM14 in the substrate processing system PS1.

[0056] Next, the substrate 21 that has been subjected to the exposure process is carried out of the atmospheric apparatus via a loader and transferred into a vacuum apparatus via the loader by an atmospheric transfer mechanism. Next, the substrate 21 transferred into the vacuum apparatus is transferred to a developing apparatus in the vacuum apparatus, and the resist film 23 is developed in the developing apparatus to form a resist pattern 23p having an opening that exposes a part of the copper film 22 (see FIG. 10). The developing apparatus may be, for example, any of the process modules PM21 to PM24 in the substrate processing system PS2.

[0057] Next, the substrate 21 is transferred from the developing apparatus to an ionic liquid coating apparatus, where an ionic liquid is coated on the resist pattern 23p, thereby forming an ionic liquid film 25 (see FIG. 11). When forming the ionic liquid film 25, it is preferable to apply the liquid film forming step S20 and the solid film forming step S30 of the substrate processing method according to the above-described embodiment. In this case, the ionic liquid film 25 functions as a protective film that has high barrier properties against oxidizing gases, preventing the oxidizing gases from reaching the copper film 22. As a result, corrosion of the surface of the copper film 22 can be suppressed. The ionic liquid coating apparatus may be, for example, any of the process modules PM21 to PM24 in the substrate processing system PS2. The ionic liquid film 25 may also be formed in the developing apparatus.

[0058] Next, the substrate 21 on which the ionic liquid film 25 is formed is removed from the vacuum chamber via a loader and transferred into an atmospheric chamber via the loader by an atmospheric transfer mechanism. The substrate 21 is then transferred to a film-forming apparatus within the atmospheric chamber, where a film-forming process is performed on the substrate 21 to form a metal film 26 (see FIG. 12 ). The film-forming process may be, for example, a plating process. Because the ionic liquid is conductive, electrolytic plating using the ionic liquid can be performed. Alternatively, electroless plating may be performed. The ionic liquid film 25 applied to the surface of the substrate 21 in the film-forming apparatus may be removed by washing it away (replacement cleaning) before the film-forming process. The removal of the ionic liquid film 25 is preferably performed by applying the removal step S40 of the substrate processing method according to the embodiment described above. In this case, the ionic liquid film 25 can be easily removed. If the film-forming process is a plating process, the ionic liquid film 25 may be replaced (by washing away) with an ionic liquid in which the metal to be formed is dissolved. The film forming apparatus may be, for example, one of the process modules PM11 to PM14 in the substrate processing system PS1.

[0059] Next, the substrate 21 is transferred from the film forming apparatus to an ionic liquid coating apparatus, where an ionic liquid is applied onto the metal film 26 to form an ionic liquid film 27 (see FIG. 13). When forming the ionic liquid film 27, it is preferable to apply the liquid film forming step S20 and the solid film forming step S30 of the substrate processing method according to the above-described embodiment. In this case, the ionic liquid film 27 functions as a protective film that has high barrier properties against oxidizing gases, preventing the oxidizing gases from reaching the metal film 26. As a result, corrosion of the surface of the metal film 26 can be suppressed. The ionic liquid coating apparatus may be, for example, any of the process modules PM11 to PM14 in the substrate processing system PS1. The ionic liquid film 27 may also be formed in a film forming apparatus.

[0060] Next, the substrate 21 on which the ionic liquid film 27 has been formed is carried out of the atmospheric apparatus via a loader and transferred into a vacuum apparatus via the loader by an atmospheric transfer mechanism. Next, the substrate 21 transferred into the vacuum apparatus is transferred to an ionic liquid removal apparatus within the vacuum apparatus, where the ionic liquid film 27 is removed (see FIG. 14). When removing the ionic liquid film 27, it is preferable to apply the removal step S40 of the substrate processing method according to the above-described embodiment. In this case, the ionic liquid film 27 can be easily removed. The ionic liquid removal apparatus may be, for example, any of the process modules PM21 to PM24 in the substrate processing system PS2.

[0061] Next, the substrate 21 is transferred from the ionic liquid removal apparatus to a resist removal apparatus, where the resist pattern 23p is removed by ashing or the like (see FIG. 15). The resist removal apparatus may be, for example, any of the process modules PM21 to PM24 in the substrate processing system PS2. The resist pattern 23p may also be removed in the ionic liquid removal apparatus.

[0062] The loader for the atmospheric device may be, for example, any one of the load ports LP11 to LP14 in the substrate processing system PS1, and the loader for the vacuum device may be, for example, any one of the load ports LP21 to LP24 in the substrate processing system PS2.

[0063] [Evaluation results] 16 to 19, the oxidizing gas barrier properties of a solid film and a liquid film of THTDP-DcO, which is an example of an ionic liquid, were evaluated.

[0064] First, a method for fabricating a sample for evaluating the oxidizing gas barrier property of a solid film of THTDP-DcO (hereinafter referred to as a "solid film evaluation sample") will be described with reference to Fig. 16. Fig. 16 is a cross-sectional view showing the fabrication method of the solid film evaluation sample.

[0065] As shown in FIG. 16(a), a copper film 32 was formed on a silicon substrate 31 by sputtering. Next, as shown in FIG. 16(b), THTDP-DcO was supplied to the surface of the copper film 32 at 80°C, forming a liquid film 33 on the surface of the copper film 32. Next, as shown in FIG. 16(c), the silicon substrate 31 was cooled to 25°C, and the liquid film 33 was solidified to form a solid film 34. The silicon substrate 31 was then left in a dry air atmosphere with an oxygen concentration of approximately 20% for 24 hours. While the silicon substrate 31 was left in the dry air atmosphere, the higher the barrier property of the solid film 34 against oxidizing gases, the less oxidation there was on the surface of the copper film 32 protected by the solid film 34. Next, as shown in FIG. 16(d), an alcohol-based solvent was supplied to the silicon substrate 31, and the solid film 34 was removed. Next, as shown in FIG. 16( e), a copper film 35 was formed on the copper film 32 by sputtering to a thickness of approximately 13 nm. The copper film 35 functions as a protective film to prevent the surface of the copper film 32, exposed by removing the solid film 34, from oxidizing prior to the evaluation described below. A sample for solid film evaluation was fabricated using the above method. The formation of the copper film 32, the formation of the liquid film 33, the formation of the solid film 34, the removal of the solid film 34, and the formation of the copper film 35 were all carried out in an argon atmosphere with a dew point of −59°C and an oxygen concentration of 25 ppm.

[0066] Next, a method for producing a sample for evaluating the oxidizing gas barrier property of a THTDP-DcO liquid film (hereinafter referred to as a "liquid film evaluation sample") will be described with reference to Fig. 17. Fig. 17 is a cross-sectional view showing the method for producing the liquid film evaluation sample.

[0067] As shown in FIG. 17(a), a copper film 32 was formed on a silicon substrate 31 by sputtering. Next, as shown in FIG. 17(b), THTDP-DcO was supplied to the surface of the copper film 32 at 80°C to form a liquid film 33 on the surface of the copper film 32. Next, while the liquid film 33 was maintained at 80°C to prevent solidification, the silicon substrate 31 was left in a dry air atmosphere with an oxygen concentration of approximately 20% for 24 hours. While the silicon substrate 31 was left in the dry air atmosphere, the higher the barrier property of the liquid film 33 against oxidizing gases, the less oxidation occurred on the surface of the copper film 32 protected by the liquid film 33. Next, as shown in FIG. 17(c), an alcohol-based solvent was supplied to the silicon substrate 31, and the liquid film 33 was removed. Next, as shown in FIG. 17(d), a copper film 35 was formed on the copper film 32 by sputtering to a thickness of approximately 22 nm. The copper film 35 functions as a protective film to prevent the surface of the copper film 32, which is exposed by removing the liquid film 33, from oxidizing before the evaluation described below. A sample for liquid film evaluation was prepared using the above method. The formation of the copper film 32, the formation of the liquid film 33, the removal of the liquid film 33, and the formation of the copper film 35 were carried out in an argon atmosphere with a dew point of -59°C and an oxygen concentration of 25 ppm.

[0068] Next, the atomic concentrations of oxygen atoms (O) and copper atoms (Cu) in the depth direction of the solid film evaluation sample and the liquid film evaluation sample were measured by X-ray photoelectron spectroscopy (XPS). The atomic concentrations were measured in the regions of the copper film 32 protected by the solid film 34 and the liquid film 33 when the solid film evaluation sample and the liquid film evaluation sample were fabricated.

[0069] FIG. 18 is a diagram showing the oxidation state of the surface of copper film 32 protected by solid film 34, showing the atomic concentrations of oxygen atoms and copper atoms in the depth direction of the solid film evaluation sample. FIG. 19 is a diagram showing the oxidation state of the surface of copper film 32 protected by liquid film 33, showing the atomic concentrations of oxygen atoms and copper atoms in the depth direction of the liquid film evaluation sample. In FIGS. 18 and 19, the horizontal axis represents the depth [nm] from the surface of copper film 35, and the vertical axis represents the atomic concentrations [at%] of oxygen atoms and copper atoms. In FIGS. 18 and 19, the solid line represents the atomic concentration of oxygen atoms, and the dashed line represents the atomic concentration of copper atoms.

[0070] 18 and 19, it can be seen that the oxygen concentration at the surface of the copper film 32 of the solid film evaluation sample is significantly lower than the oxygen concentration at the surface of the copper film 32 of the liquid film evaluation sample. This result shows that the barrier properties of THTDP-DcO against oxidizing gases are significantly improved by using it in the solid phase.

[0071] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0072] In the above embodiment, a protective film is formed on the surface of a metal film, which is an example of a target film. However, the present disclosure is not limited to this. For example, the target film may be any film for which unintended surface alteration during semiconductor manufacturing processes is desired to be suppressed. Examples of such films include conductive films such as polysilicon films, and diffusion layers (p-type diffusion layers, n-type diffusion layers) on semiconductor device substrates, which are susceptible to surface oxidation by oxidizing gases. Forming a protective film on the surface of a conductive film, diffusion layer, or the like can suppress surface oxidation of the conductive film, diffusion layer, or the like. The various films may also be insulating films. Examples of insulating films include low-k films such as SiOC films and boron nitride (BN) films. Oxidation of the surface of a low-k film can sometimes cause degradation of the k value. Forming a protective film on the surface of a low-k film can suppress degradation of the k value. Low-k films are used, for example, as interlayer insulating films. [Explanation of symbols]

[0073] 12 metal film 13 Liquid Film 14 Solid Film W substrate S10 Preparation Project S20 Liquid film formation process S30 Solid Film Formation Engineering S40 Removal Process

Claims

1. preparing a substrate having a target film exposed on its surface; supplying an ionic liquid containing an oxo acid structure having six or more carbon atoms to the surface of the substrate at a first temperature to form a liquid film on the surface of the target film; cooling the substrate to a second temperature lower than the first temperature to solidify the liquid film to form a solid film; supplying a polar solvent to the substrate and removing the solid film; having Substrate processing method.

2. The second temperature is a temperature equal to or lower than the freezing point of the ionic liquid. The substrate processing method according to claim 1 .

3. the step of removing the solid film includes esterifying at least a portion of the oxo acid structure contained in the solid film. The substrate processing method according to claim 1 or 2.

4. The oxo acid structure contains a carboxylate anion. The substrate processing method according to claim 1 .

5. The carboxylate anion is a decanoate anion. The substrate processing method according to claim 4 .

6. The ionic liquid is trihexyltetradecylphosphonium decanoate. The substrate processing method according to claim 1 .

7. the first temperature is equal to or higher than 50°C and equal to or lower than 200°C, The second temperature is 20°C or higher and 30°C or lower. The substrate processing method according to claim 6 .

8. The polar solvent is an alcohol-based solvent. The substrate processing method according to claim 1 .

9. a step of exposing the substrate to the atmosphere between the step of forming the solid film and the step of removing the solid film; The substrate processing method according to claim 1 .

10. a first processing device that performs a first processing on a substrate; a second processing device that performs a second processing on the substrate; a third processing apparatus for performing a third processing on the substrate; a transfer device that transfers the substrate between the first processing device and the second processing device without exposing the substrate to an atmosphere containing oxygen; Equipped with the first process includes a process of forming a target film on a surface of the substrate; the second treatment includes a step of supplying an ionic liquid containing an oxo acid structure having six or more carbon atoms to a surface of the substrate at a first temperature to form a liquid film on the surface of the target film, and a step of cooling the substrate to a second temperature lower than the first temperature to solidify the liquid film to form a solid film; the third treatment includes a treatment of supplying a polar solvent to the substrate and removing the solid film; Substrate processing system.

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