Cleaning solution, cleaning method, substrate processing method, and substrate processing apparatus

Abstract

To enable cleaning using liquids under reduced pressure.SOLUTION: A cleaning solution composed of ionic liquids or boiling-point-elevating mixtures that does not volatilize at 25°C under low vacuum.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cleaning liquid, a cleaning method, a substrate processing method, and a substrate processing apparatus. [Background technology]

[0002] In the manufacturing process of semiconductor devices and the like, a cleaning process is performed on a substrate such as a semiconductor wafer (hereinafter referred to as "wafer") to clean its surface. This cleaning process may be performed using a cleaning liquid. Patent Document 1 discloses that a substrate is washed with water after etching. Note that cleaning processes using cleaning liquids are also performed in processes other than the manufacturing process (for example, in equipment maintenance processes, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-116449 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, cleaning using a cleaning liquid has conventionally been carried out under atmospheric pressure, and there is a risk that the cleaning liquid will volatilize when exposed to a reduced pressure atmosphere.

[0005] The present invention has been made in view of the above circumstances, and has as its object to enable cleaning under reduced pressure using a liquid. [Means for solving the problem]

[0006] To achieve the above object, one aspect of the present invention is a cleaning liquid that is made of an ionic liquid or a mixture that increases the boiling point, and is characterized by not volatilizing at 25°C and in low vacuum.

[0007] The cleaning solution according to the present invention does not volatilize at 25° C. and in a low vacuum, and therefore cleaning can be performed under reduced pressure using the cleaning solution. [Effects of the Invention]

[0008] According to the present invention, cleaning using a liquid under reduced pressure can be made possible. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view showing an outline of the configuration of a wafer processing apparatus as a substrate processing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a longitudinal cross-sectional view showing an outline of the configuration of a processing module. [Figure 3] 2 is a flowchart showing main steps of an example of processing by the wafer processing apparatus of FIG. 1, including etching processing of metal on a wafer W. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Wafer processing equipment> First, a wafer processing apparatus as a substrate processing apparatus according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a plan view showing an outline of the configuration of the wafer processing apparatus. In this specification and drawings, elements having substantially the same functional configuration are designated by the same reference numerals, and redundant description will be omitted.

[0011] The wafer processing apparatus 1 in FIG. 1 performs various processes on wafers W as substrates, and includes an atmospheric section 10 and a reduced pressure section 11, which are connected together via load lock modules 20 and 21. The atmospheric section 10 includes an atmospheric module whose interior is kept under atmospheric pressure. The reduced pressure section 11 includes a reduced pressure module that performs desired processes on wafers W in a reduced pressure atmosphere (vacuum atmosphere). Note that reduced pressure in the present invention refers to a pressure range below "low vacuum," which will be explained later, and includes pressure ranges such as "medium vacuum," "high vacuum," and "ultra-high vacuum."

[0012] The load lock modules 20 and 21 are provided to connect the loader module 30 included in the atmospheric section 10 and the transfer module 50 included in the reduced pressure section 11 via a gate valve (not shown). The load lock modules 20 and 21 are configured to temporarily hold the wafer W. The load lock modules 20 and 21 are also configured so that the interior thereof can be switched between an atmospheric pressure atmosphere and a reduced pressure atmosphere.

[0013] The atmospheric section 10 has a loader module 30 equipped with a transfer mechanism 40 (described later), and a load port 32 on which a FOUP 31 is placed. The FOUP 31 is a container capable of storing multiple wafers W. The loader module 30 may be connected to an orienter module (not shown) that adjusts the horizontal orientation of the wafer W, a buffer module (not shown) that temporarily stores multiple wafers W, and the like.

[0014] The loader module 30 has a rectangular housing, the interior of which is maintained at atmospheric pressure. A plurality of, for example, five load ports 32 are arranged side by side on one side that constitutes the long side of the housing of the loader module 30. Load lock modules 20 and 21 are arranged side by side on the other side that constitutes the long side of the housing of the loader module 30.

[0015] A transfer mechanism 40 configured to hold and transfer a wafer W is provided inside the housing of the loader module 30. The transfer mechanism 40 has a transfer arm 41 that supports the wafer W during transfer, a rotary table 42 that rotatably supports the transfer arm 41, and a base 43 on which the rotary table 42 is mounted. Also, a guide rail 44 extending in the longitudinal direction of the loader module 30 is provided inside the loader module 30. The base 43 is provided on the guide rail 44, and the transfer mechanism 40 is configured to be movable along the guide rail 44.

[0016] The decompression unit 11 has a transfer module 50, a processing module 60 as a cleaning unit, and another processing module 61 that performs a different process on the wafer W from the processing module 60. The interiors of the transfer module 50 and the processing modules 60, 61 (specifically, the interiors of the decompression transfer chamber 51 and chamber 100 described below) are each maintained in a decompressed atmosphere. A single transfer module 50 may be provided with a plurality of processing modules 60, and a single processing module 61 may also be provided with a plurality of processing modules 61. In the example shown in the figure, one processing module 60 and a plurality of processing modules 61 are provided. The number and arrangement of the processing modules 60, 61 are not limited to those in this embodiment and can be set as desired.

[0017] The transfer module 50 is configured to transfer the wafer W therein. The transfer module 50 includes a decompression transfer chamber 51 having a housing that is polygonal in plan view (rectangular in plan view in the illustrated example), and the decompression transfer chamber 51 is connected to the load lock modules 20 and 21.

[0018] The transfer module 50 transports wafers W that have been loaded into the load lock module 20 to the processing module 60, transports wafers W that have been processed in the processing module 60 to the processing module 61, and transports wafers W that have been processed in the processing module 61 to the load lock module 21.

[0019] The processing module 60 cleans the wafer W, the metal of which has been etched, under reduced pressure using a cleaning liquid. In this embodiment, the processing module 60 etches the metal of the wafer W using an etching liquid. That is, in this embodiment, the processing module 60 functions not only as a cleaning unit but also as an etching unit. Furthermore, in this embodiment, etching by the processing module 60 is performed under reduced pressure. The processing module 60 may be configured to adjust the temperature of at least one of the wafer W and the etching liquid. Although the etching rate varies depending on the etching liquid, if the etching rate improves as the temperature of at least one of the wafer W and the etching liquid increases, the desired etching rate can be obtained by adjusting the temperature of at least one of the wafer W and the etching liquid according to the etching liquid. The processing module 60 is connected to the transfer module 50 via a gate valve 62. The specific configuration of the processing module 60 will be described later.

[0020] The processing module 61 performs a desired process (for example, a film formation process) under reduced pressure on the wafer W that has been processed in the processing module 60. The processing module 61 is connected to the transfer module 50 via a gate valve 63.

[0021] A transfer robot 70 is provided inside the reduced pressure transfer chamber 51 of the transfer module 50. The transfer robot 70 is configured to be able to hold and transfer a wafer W.

[0022] The transfer robot 70 has a transfer arm 71 that is configured to be able to rotate, extend, and move up and down while holding a wafer W. The tip of the transfer arm 71 is branched into two forks 72 that serve as holding parts. Each of the forks 72 is configured to be able to hold a wafer W to be transferred.

[0023] In the transfer module 50, the transfer arm 71 receives the wafer W held in the load lock module 20 and carries it into the processing module 60. The transfer arm 71 also receives the wafer W that has been processed in the processing module 60 and carries it into the processing module 61. The transfer arm 71 also receives the wafer W that has been processed in the processing module 61 and carries it out to the load lock module 21.

[0024] Furthermore, the wafer processing apparatus 1 has a control unit 80. The control unit 80 includes a computer equipped with a processor such as a CPU, a memory, and the like, and has a program storage unit (not shown). The program storage unit stores a program including instructions for processing by the wafer processing apparatus 1. The program may be recorded on a computer-readable storage medium H and installed into the control unit 80 from the storage medium H. The storage medium H may be a medium for temporary storage or a medium for non-temporary storage.

[0025] <Processing Module 60> FIG. 2 is a vertical cross-sectional view showing the outline of the configuration of the processing module 60. As shown in FIG.

[0026] 2, the processing module 60 includes a chamber 100 configured so that the interior can be depressurized. A loading / unloading port (not shown) for the wafer W is formed on the side of the chamber 100 facing the transfer module 50 (see FIG. 1), and a gate valve 62 is provided at the loading / unloading port.

[0027] A rotary holder 110 is provided within the chamber 100. The rotary holder 110 holds the wafer W and is configured to be rotatable around a vertical axis. The rotary holder 110 has a base 111 and a holder 112.

[0028] The base 111 includes a disk-shaped top plate portion 111a. A plurality of holders 112 are provided on the outer periphery of the top plate portion 111a. Each of the holders 112 holds the wafer W from its side. These holders 112 hold the wafer W horizontally while slightly spaced apart from the upper surface of the top plate portion 111a. The holders 112 may be formed with a recess (not shown) into which the peripheral edge of the wafer W is fitted, and may be configured to be movable horizontally (specifically, in the radial direction of the top plate portion 111a).

[0029] The base 111 further includes a columnar shaft 111b. The shaft 111b is connected to the center of the lower surface of the top plate 111a. The shaft 111b is also connected to a rotation mechanism 113. The rotation mechanism 113 includes a drive source such as a motor, and rotates the shaft 111b around a vertical axis at a desired speed. This allows the wafer W held by the rotation holder 110, which includes the shaft 111b, to be rotated around the vertical axis at a desired speed. The base 111 is rotatably supported by the chamber 100 and a cup 120 (described later) via bearings 114 .

[0030] The spin holder 110 also has a gas supply unit 115 as a heating unit for heating the wafer W. The gas supply unit 115 supplies a heating gas from below to the wafer W held by the spin holder 110. The gas supply unit 115 is, for example, a columnar member inserted into a hollow portion 111c formed in the center of the base 111. A flow path 115a is formed inside the gas supply unit 115. A heating gas supply source 116 is connected to the flow path 115a via a supply equipment group 117. The supply equipment group 117 includes a valve and a flow rate regulator that control the flow of the heating gas. The heating gas is, for example, an inert gas at a temperature higher than room temperature, and the inert gas is, for example, nitrogen gas.

[0031] In this embodiment, the gas supply unit 115 is configured to be able to raise and lower the wafer W in order to transfer the wafer W between the transfer robot 70 provided in the transfer module 50 and the rotation holder 110. Specifically, the gas supply unit 115 is connected to a lifting mechanism 118 including a drive source (e.g., a cylinder) for raising and lowering the gas supply unit 115.

[0032] In addition, in order to prevent the reduced pressure state in chamber 100 from being impaired through hollow portion 111c of base 111 through which gas supply portion 115 is inserted, for example, a bellows (not shown) is provided to cover the periphery of the portion of gas supply portion 115 that is exposed downward from shaft portion 111b of base 111.

[0033] Furthermore, a cup 120 is provided around the base 111 of the rotary holder 110 to receive and collect liquid that splashes or drops from the wafer W. A discharge pipe 121 that discharges the collected liquid to the outside of the processing module 60 and an exhaust pipe 122 that discharges the atmosphere in the cup 120 to the outside of the processing module 60 are connected to the bottom of the cup 120. Even when the pressure inside the chamber 100 is reduced, the pressure inside the exhaust pipe 121 and the exhaust pipe 122 is controlled to be equal to the pressure inside the chamber 100 so that the processing liquid and the atmosphere do not flow back through the exhaust pipe 121 and the exhaust pipe 122.

[0034] Additionally, a first arm 130 and a second arm 140 are provided above the cup 120 within the chamber 100 .

[0035] The first arm 130 is provided with an etching nozzle 131 that discharges an etching solution and supplies it onto the wafer W. The first arm 130 is also rotatable about a vertical axis and movable up and down by a movement mechanism 132 including a drive source (e.g., a motor, etc.). This allows the etching nozzle 131 to move from outside the cup 120 to above the center of the wafer W in the cup 120, and also allows the height of the etching nozzle 131 to be adjusted.

[0036] An etching liquid supply source 133 is connected to the etching nozzle 131 via a supply device group 134. The supply device group 134 includes a valve and a flow rate regulator that controls the flow of the etching liquid.

[0037] The etching liquid supplied from the etching nozzle 131 is, for example, an ionic liquid consisting of a carboxylate anion and a quaternary cation. Examples of the carboxylate anion include acetic acid (AcO) anion, formic acid anion, propionic acid (EtCO2H) anion, butyric acid anion, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, and 2-ethylhexanoic acid. Examples of the quaternary cation include an ammonium cation, a pyrrolidinium cation, a pyridinium cation, an imidazolium cation, and a phosphonium cation. An example of the imidazolium cation is 1-ethyl-3-methylimidazolium (EMI) cation.

[0038] The etching solution may also be a protic ionic liquid, which is an ionic liquid synthesized by neutralizing a Bronsted base and a Bronsted acid, and is also called a neutralized ionic liquid. The cation of the protic ionic liquid is preferably a proton adduct of a primary, secondary, or tertiary amine, and specific examples include cyclic ammonium cations such as imidazolium cation and pyrrolidinium cation, and chain ammonium cations such as cations in which hydrogen is added to ethylamine, butylamine (BuNH3), and N,N-diethyl-N-2-methoxyethylamine. The cation of the protic ionic liquid may also be a cation in which hydrogen is added to DBU or DBN. An example of the pyrrolidinium cation is a cation in which hydrogen is added to N-2-methoxyethylpyrrolidine. Examples of the anions of the above protic ionic liquids include nitrate anion (NO3 -), sulfate anion (HSO4 - ), carbonate anion (HCO3 - ), phosphate anion (H2PO4 - ), sulfonate anions, sulfate ester anions, phosphate ester anions, carboxylate anions, and the like.

[0039] Furthermore, the etching liquid may be a mixture of the ionic liquid comprising the above-mentioned carboxylic acid anion and quaternary cation, and a protic ionic liquid.

[0040] The etching solution may also be an ionic liquid obtained by diluting the above-mentioned ionic liquid composed of a carboxylate anion and a quaternary cation as a first ionic liquid capable of dissolving metals with a second ionic liquid having a low ability to dissolve metals. In other words, the etching solution may be an ionic liquid containing a carboxylate anion. Examples of the second ionic liquid used as a diluent include ionic liquids having quaternary salts and anions other than carboxylic acids, such as N,N-diethyl-N-2-methoxyethyl-N-methylammonium tosylate (DEME·TsO), 1-ethylpyridinium bis(fluorosulfonyl)amide (EtPy·FSA), N,N-diethyl-N-2-methoxyethyl-N-methylammonium bis(fluorosulfonyl)amide (DEME·FSA), N-2-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide (MEMP·TFSA), and N,N-diethyl-N-2-methoxyethyl-N-methylammonium tetrafluoroborate (DEME·BF4). The concentration of the carboxylic acid anion-containing ionic liquid in the etching solution may be appropriately determined within the range of 99 wt% to 10 ppm, taking into consideration the etching rate of each etching solution. A higher concentration may be used to speed up the etching rate, and a lower concentration may be used to slow down the etching rate, but in practice, a concentration of 50 wt% to 0.5 wt% is preferred.

[0041] The etching solution may also be an ionic liquid containing a halide anion. Specifically, it may be an ionic liquid solution or a mixed ionic liquid solution in which a halide salt is diluted with an ionic liquid having low metal dissolving ability. In this case, the salt containing a halide anion may be a solid or an ionic liquid. Specifically, the etching solution may be an ionic liquid solution in which a solid halide salt is diluted with an ionic liquid having low metal dissolving ability, or a mixed liquid of an ionic liquid comprising a halide anion and a quaternary cation and an ionic liquid having low metal dissolving ability. The ionic liquid having low metal dissolving ability may be the same as the second ionic liquid used as a diluent described above. Examples of the halide anion include bromide (Br) anion and chloride (Cl) anion. Examples of the quaternary cation for the halide anion include imidazolium cation, N,N-diethyl-N-2-methoxyethyl-N-methylammonium (DEME) cation, etc. Examples of the cation that forms a solid salt with the halide include inorganic cations such as sodium and potassium. The concentration of the halide salt in the etching solution may be appropriately determined within the range of 99 wt% to 10 ppm, taking into consideration the etching rate of each etching solution. A higher concentration may be used to speed up the etching rate, and a lower concentration may be used to slow down the etching rate, but in practice, a concentration of 50 wt% to 0.5 wt% is preferable.

[0042] The etching solution may be an ionic liquid obtained by containing the above-mentioned protic ionic liquid as a first ionic liquid capable of dissolving metals, and diluting this protic ionic liquid with the above-mentioned second ionic liquid having a low ability to dissolve metals. The concentration of the protic ionic liquid in the etching solution may be appropriately determined within the range of 99 wt% to 10 ppm, taking into consideration the etching rate of each etching solution. A higher concentration may be used to speed up the etching rate, and a lower concentration may be used to slow down the etching rate, but in practice, a concentration of 50 wt% to 0.5 wt% is preferable.

[0043] Furthermore, the etching solution may contain a plurality of ionic liquids selected from an ionic liquid containing a carboxylate anion, an ionic liquid containing a halide anion, and a protic ionic liquid. Specifically, the first ionic liquid serving as an etching agent constituting the etching solution may contain a plurality of ionic liquids selected from an ionic liquid containing a carboxylate anion, an ionic liquid containing a halide anion, and a protic ionic liquid.

[0044] The second arm 140 is provided with a cleaning nozzle 141 that discharges a cleaning liquid and supplies it onto the wafer W. The second arm 140 is also rotatable about a vertical axis and movable up and down by a movement mechanism 142 including a drive source (e.g., a motor, etc.). This allows the cleaning nozzle 141 to move from the outside of the cup 120 to above the center of the wafer W in the cup 120, and also allows the height of the cleaning nozzle 141 to be adjusted.

[0045] A cleaning liquid supply source 143 is connected to the cleaning nozzle 141 via a supply device group 144. The supply device group 144 includes a valve and a flow rate regulator that controls the flow of the cleaning liquid.

[0046] The cleaning liquid supplied from the cleaning nozzle 141 is made of an ionic liquid, which does not volatilize at 25°C and low vacuum. In this specification, "low vacuum" refers to the pressure range specified by JIS (Japanese Industrial Standards). That is, "low vacuum" means a pressure range of 10 5 Pa~10 2 This is the pressure range of Pa.

[0047] The ionic liquid used as the cleaning liquid is not particularly limited as long as it is classified as an ionic liquid because it does not volatilize at 25°C and in low vacuum due to its physical properties, and may be a quaternary salt type ionic liquid or a protic ionic liquid, or may be the same as the ionic liquid used as the etching liquid. In other words, the cleaning liquid and the etching liquid may be the same liquid. Specifically, the cleaning liquid may be composed of an ionic liquid consisting of a carboxylate anion and a quaternary cation, and / or a protic ionic liquid. Alternatively, the cleaning liquid may be an ionic liquid obtained by diluting a first ionic liquid, which serves as an etching agent capable of dissolving metals, with a second ionic liquid, which serves as a diluent having low metal dissolving ability. The cleaning liquid may be composed of an ionic liquid containing at least one of a halide anion, a carboxylate anion, and a protic ionic liquid.

[0048] Furthermore, the ionic liquid used as the cleaning liquid may not contain a first ionic liquid capable of dissolving metals, but may instead consist of a second ionic liquid having a low ability to dissolve metals.

[0049] Furthermore, the cleaning liquid may be a mixture whose boiling point increases, specifically a mixture whose boiling point increases when mixed, and which does not volatilize at 25° C. and in a low vacuum. An example of a mixed liquid is a mixture of two kinds of liquids, but there is no particular limitation as long as the mixture exhibits a boiling point higher than the boiling points of the original liquids. A suitable example of a combination of the two types of liquids is a combination of a liquid amine and a liquid acid. Examples of the amines include primary to tertiary amines. Furthermore, examples of combinations of the liquid amines and liquid acids include combinations of N-alkylimidazoles and carboxylic acids. Examples of N-alkylimidazoles include 1-methylimidazole (MeIm), 1-ethylimidazole (EtIm), 1-butylimidazole (BuIm), 1-hexylimidazole (HexIm), 1-octylimidazole (OctIm), 1-decylimidazole (DecIm), and 1-dodecylimidazole (DodeIm). Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, and 2-ethylhexanoic acid. The mixture may be a mixture in which a solute is dissolved in a solvent.

[0050] Whether the cleaning liquid is an ionic liquid or a mixture of the above, if removal is not taken into consideration, it is preferable that the cleaning liquid does not volatilize at 25°C and medium vacuum, more preferably at 25°C and high vacuum, and even more preferably at 25°C and ultra-high vacuum or lower. In this specification, "medium vacuum" and "high vacuum" refer to the pressure ranges specified by JIS (Japanese Industrial Standards). That is, "medium vacuum" means a pressure range of 10 2 Pa~10 -1 Pa, and "high vacuum" is defined as a pressure range of 10 -1 Pa~10 -5 Pa, and "ultra-high vacuum" is 10 -5 Pa~10 -9 This is the pressure range of Pa.

[0051] This cleaning solution can be removed by controlling the degree of vacuum and the ambient temperature. For example, it can be removed by volatilizing it by increasing the vacuum from a low vacuum to a high vacuum, or by heating the ambient temperature to above 25°C even while maintaining the low vacuum. In this case, the cleaning solution can be removed while maintaining the vacuum without returning to atmospheric pressure, which is useful for simplifying the process.

[0052] The chamber 100 is also formed with an exhaust port 101. Specifically, the exhaust port 101 is formed, for example, at the bottom of the chamber 100. An exhaust mechanism 150 is connected to the exhaust port 101. The exhaust mechanism 150 includes, for example, a pressure adjustment valve and a vacuum pump. The vacuum pump is, for example, a turbomolecular pump, a roughing pump, or a combination thereof. By drawing air through the exhaust mechanism 150, the inside of the chamber 100 can be made into a reduced pressure atmosphere.

[0053] Furthermore, an ammonia gas supply port 102 may be formed in the chamber 100. An ammonia gas supply source 160 is connected to the supply port 102 via a supply equipment group 161. The supply equipment group 161 includes a valve and a flow rate regulator that controls the flow of the ammonia gas. An inert gas such as nitrogen gas, helium gas, or argon gas may be supplied from the supply port 102. Specifically, the flow rate of an inert gas such as nitrogen gas from a supply source 160 may be adjusted by a supply device group 161, and the inert gas may be supplied into the chamber 100 via the supply port 102. This allows the interior of the chamber 100 to be filled with an inert gas atmosphere.

[0054] <Processing by wafer processing device 1> Next, an example of processing by the wafer processing apparatus 1 will be described. Fig. 3 is a flowchart showing the main steps of an example of processing by the wafer processing apparatus 1, including etching processing of metal on the wafer W. Note that each of the following steps is executed under the control of the control unit 80 based on a program stored in the above-mentioned program storage unit (not shown).

[0055] (Step S1) First, the wafer W is transferred from the outside of the wafer processing apparatus 1 to the processing module 60.

[0056] Specifically, the wafer W is removed from the FOUP 31 by the transfer mechanism 40 and transferred to the load lock module 20. Next, the inside of the load lock module 20 is sealed and depressurized. Thereafter, the inside of the load lock module 20 is connected to the inside of the transfer module 50, which has been depressurized in advance.

[0057] Next, the wafer W is transferred from the load lock module 20 to the transfer module 50 by the transfer robot 70 . Subsequently, the gate valve 62 corresponding to the processing module 60 is opened, and the transfer robot 70 transfers the wafer W into the chamber 100 of the processing module 60, which has been previously depressurized. Thereafter, the gas supply unit 115 is raised and lowered, and the transfer robot 70 is retracted from the chamber 100, whereby the wafer W is held by the holder 112 of the rotating holder 110 via the gas supply unit 115. Then, the gate valve 62 is closed.

[0058] (Step S2) The wafer W is then subjected to processing in the processing module 60 . Specifically, for example, the following steps S2a, S2b, and S2c are performed.

[0059] (Step S2a) In this step, the metal formed on the wafer W is etched by the etching solution. The metal etched in this step is, for example, copper, although the metal may also be tungsten, molybdenum, cobalt, an aluminum-copper alloy, or an aluminum-nickel alloy.

[0060] Specifically, in this step, the metal formed on the wafer W is etched under reduced pressure with an etching solution.

[0061] More specifically, in the chamber 100, which has a reduced pressure atmosphere, the etching nozzle 131 is moved above the center of the wafer W held by the holder 112. Thereafter, for a predetermined time T1, an etching liquid is discharged from the etching nozzle 131 toward the wafer W, and the wafer W is rotated at a predetermined rotation speed R1. As a result, a puddle (liquid film) of the etching liquid is formed on the wafer W.

[0062] Thereafter, after the discharge of the etching liquid from the etching nozzle 131 is stopped, the etching nozzle 131 is retracted from above the wafer W, and the puddle of etching liquid is maintained for a predetermined time T2. As a result, the metal on the surface of the wafer W reacts with the etching liquid and is removed. At this time, for example, the upper part of the metal pattern on the surface of the wafer W is removed, and the lower part remains. The wafer W may be rotated while the puddle of etchant is maintained. Furthermore, if the etching rate improves as the processing temperature increases, one or both of the wafer W and the etching solution may be heated to achieve a desired etching rate. In this case, etching is performed while heating the wafer W by supplying a heating gas to the wafer W from the gas supply unit 115. The etching solution is supplied from the etching nozzle 131 in a heated state. The etching solution is heated by, for example, a heater attached to the supply source 133 or a pipe connecting the supply source 133 and the etching nozzle 131.

[0063] If an oxide film is formed on the surface of the metal formed on the wafer W before the start of this process, this oxide film is also removed by the etching solution in this process. Specifically, in this case, the oxide film on the metal surface is first removed by the etching solution in this process, and then the metal under the oxide film is removed.

[0064] (Step S2b) After step S2a, the wafer W is cleaned with a cleaning liquid. Specifically, the wafer W is cleaned with a cleaning liquid under reduced pressure. More specifically, in the chamber 100, which has a reduced pressure atmosphere, the cleaning nozzle 141 is moved above the center of the wafer W held by the holder 112. Thereafter, a cleaning liquid is discharged from the cleaning nozzle 141 toward the wafer W for a predetermined time T3, and the wafer W is rotated at a predetermined rotation speed R2. As a result, the etching liquid containing a reaction product with the metal on the etched wafer W is washed away from the wafer W by the cleaning liquid. As a result, the surface of the metal remaining on the wafer W is cleaned by the cleaning liquid.

[0065] (Step S2c) After step S2b, the cleaning liquid on the wafer W is removed under reduced pressure, and the wafer W is dried. The cleaning liquid is removed, for example, by volatilizing the cleaning liquid by creating a high vacuum; specifically, by further reducing the pressure in chamber 100, which was already at a reduced pressure in step S2b, to volatilize the cleaning liquid on wafer W. The cleaning liquid may be removed by volatilizing the cleaning liquid through heating. Specifically, the cleaning liquid may be removed by supplying a heating gas from the gas supply unit 115 to the wafer W to heat the wafer W, thereby volatilizing the cleaning liquid on the wafer W. Furthermore, the cleaning liquid may be removed by volatilizing the cleaning liquid through a reaction with ammonia gas. Specifically, the cleaning liquid may be removed by volatilizing the cleaning liquid on the wafer W through a reaction with ammonia gas supplied into the chamber 100 via the supply port 102. The cleaning liquid may also be removed by volatilizing the cleaning liquid through a combination of two or more of high vacuum, heating, and reaction with ammonia gas.

[0066] In step S2c, immediately before the cleaning liquid is removed from the wafer W by high vacuum or the like as described above, the wafer W may be further rotated so that a certain amount of the cleaning liquid is shaken off from the wafer W.

[0067] (Step S3) The wafer W processed in the processing module 60 is transferred to the processing module 61.

[0068] Specifically, the wafer W processed in the processing module 60 is transferred in a reduced pressure atmosphere and loaded into the processing module 61. More specifically, the gate valve 62 is opened, and the wafer W is transferred by the transfer robot 70 to the transfer module 50, which has been depressurized in advance. Subsequently, the gate valve 63 corresponding to the processing module 61 is opened, and the transfer robot 70 transfers the wafer W into the pre-depressurized processing module 61. Thereafter, the transfer robot 70 retreats from the chamber 100, and the gate valve 63 is closed.

[0069] (Step S4) The wafer W is then subjected to processing in the processing module 61 . Specifically, a predetermined process is performed under reduced pressure on the wafer W. As a result, for example, a desired layer is formed on the metal remaining on the surface of the wafer W even after step S2.

[0070] (Step S5) Then, the wafer W is transferred from the processing module 61 to the outside of the wafer processing apparatus 1.

[0071] Specifically, the gate valve 62 is opened, and the wafer W in the processing module 61 is transferred to the transfer module 50 by the transfer robot 70. Next, the wafer W is transferred from the transfer module 50 to the load lock module 21 by the transfer robot 70. Subsequently, the inside of the load lock module 21 is sealed and an atmospheric pressure atmosphere is created. Thereafter, the inside of the load lock module 21 and the inside of the housing of the loader module 30 are connected to each other. Then, the wafer W is transferred from the load lock module 21 by the transfer mechanism 40 and returned to the FOUP 31.

[0072] This completes the series of processes performed by the wafer processing apparatus 1.

[0073] <Major Effects of This Embodiment> As described above, in this embodiment, the cleaning liquid used is an ionic liquid or a mixture liquid that increases the boiling point and does not volatilize at 25° C. and in low vacuum. Therefore, according to this embodiment, the wafer W can be cleaned under reduced pressure using the cleaning liquid. As a result, the metal on the wafer W is not exposed to an atmosphere with high water and oxygen concentrations during cleaning, and therefore, it is possible to prevent oxides of the metal from being formed during or immediately after cleaning.

[0074] Furthermore, since etching of the wafer W using the cleaning liquid can be performed under reduced pressure, by combining with the following (A) and (B), the metal present on the wafer W after cleaning is not exposed to an atmosphere with a high concentration of water and oxygen before a desired layer is formed on the metal. (A) Removing the cleaning liquid in an atmosphere with low water and oxygen concentrations (specifically, under reduced pressure), that is, drying the wafer W. (B) When the dried wafer W is transferred to the processing module 61 where a desired layer is formed, the wafer W is transferred in an atmosphere with low water and oxygen concentrations (specifically, a reduced pressure atmosphere). Therefore, it is possible to prevent an unnecessary oxide film from being formed between the metal and the desired layer after cleaning.

[0075] <Modification> As described above, the cleaning liquid and the etching liquid may be the same. In this case, the etching nozzle 131 may be omitted. This simplifies the configuration of the processing module 60, thereby reducing costs.

[0076] In the above examples, the metal etching using the etching solution is performed under reduced pressure. Alternatively, the metal etching using the etching solution may be performed in an atmosphere of an inert gas such as nitrogen gas. That is, the atmosphere with low water and oxygen concentrations around the wafer W during the metal etching using the etching solution may be realized by an inert gas atmosphere.

[0077] In the above example, the wafer W is dried under reduced pressure. Alternatively, the wafer W may be dried under an atmosphere of an inert gas such as nitrogen gas. That is, the atmosphere around the wafer W during drying, which has low concentrations of water and oxygen, may be realized by an inert gas atmosphere.

[0078] In the above example, the dried wafer W is transferred in a reduced pressure atmosphere when being transferred to the processing module 61. Alternatively, the dried wafer W may be transferred in an atmosphere of an inert gas such as nitrogen gas when being transferred to the processing module 61. That is, the atmosphere with low water and oxygen concentrations around the wafer W when being transferred to the processing module 61 may be realized by an inert gas atmosphere.

[0079] Furthermore, at least one of etching the metal using the etching liquid, drying the wafer W, and transferring it to the processing module 61 after drying may be performed under atmospheric pressure and in an atmospheric gas atmosphere with relatively high concentrations of water and oxygen.

[0080] In the above example, one processing module 60 functions not only as a cleaning unit but also as an etching unit, and further functions as a drying unit that dries the wafer W after cleaning. Alternatively, one processing module may function only as an etching unit, and another processing module may function as a cleaning unit and a drying unit. Furthermore, one processing module may function as an etching unit and a cleaning unit, and another processing module may function only as a drying unit. Furthermore, the etching unit, cleaning unit, and drying unit may each be realized by a different processing module. Furthermore, by having one processing module function as more than one of the etching section, cleaning section, and drying section, it is possible to reduce the size of the wafer processing apparatus (specifically, the floor area occupied by the wafer processing apparatus).

[0081] In the above example, the etching of the metal using the etching solution and the cleaning of the wafer W using the cleaning solution are each performed once, but these may be performed alternately. In this case, the drying of the wafer W may be performed each time the etching and cleaning are repeated, or may be performed every n times (n is an integer of 2 or more), or may be performed only after the final cleaning.

[0082] In the above examples, the wafer is heated by bringing a heating gas into contact with the wafer. Alternatively, the wafer may be heated by radiant heat such as an infrared heater or a hot plate, and there are no particular limitations on the heating method.

[0083] In the above example, the wafers are processed one by one. Alternatively, a plurality of wafers W may be processed at once. That is, the wafer processing apparatus may perform batch processing on the wafers W.

[0084] In the above example, the object to be cleaned was a wafer W after etching. However, the object to be cleaned by the cleaning method according to the present invention is not limited to this, and may be, for example, a wafer after being subjected to a process other than etching, or may be something other than the wafer W (specifically, a wafer processing apparatus 1, etc.). Furthermore, the object to be cleaned may be an apparatus other than so-called semiconductor manufacturing equipment. [Example]

[0085] Next, examples of the present invention will be described, but the present invention should not be construed as being limited to the following examples.

[0086] A cleaning solution with the composition shown in Table 1 was prepared, and the cleaning solution was placed in a flask and exposed to a reduced pressure (2 mmHg) using a vacuum pump for 1 hour to measure the weight loss before and after the pressure reduction. In the type column for the cleaning solutions shown in Table 1, ionic liquids are indicated by "◎" if they are protic ionic liquids, "○" if they are not protonic ionic liquids, and "△" if they are mixed liquids that are not ionic liquids.

[0087] In addition, a cleaning solution with the composition shown in Table 2 was prepared, and the cleaning solution was placed in a flask and exposed to each temperature listed in the table for 1 hour under a reduced pressure (2 mmHg) atmosphere using a vacuum pump, and the weight loss before and after the pressure reduction was measured. Of the cleaning solutions shown in Table 2, protic ionic liquids are indicated by "◎" in the type column, and mixed liquids that are not ionic liquids are indicated by "△". Blank columns indicate conditions for which no data was collected.

[0088] Furthermore, a cleaning solution having the composition shown in Table 3 was prepared, and the cleaning solution was placed in a glass test tube under high vacuum (10 -3 The cleaning solution was exposed to a 200 Pa (1000 Pa) atmosphere for 1 hour, and the reduction in the amount of cleaning solution in the glass test tube was visually confirmed before and after the reduced pressure. In the "Non-Volatility Evaluation" column of Table 3, if a reduction in the amount of cleaning solution was visually confirmed, it was marked with "X" as it was assumed that the cleaning solution had volatilized due to the reduced pressure, and if not, it was marked with "O". In the column for type of cleaning solution shown in Table 3, "◎" indicates a protic ionic liquid, and "O" indicates an ionic liquid that is not a protic ionic liquid.

[0089] The comparative example in Tables 1 and 3 is water.

[0090] <cation> The cations in each cleaning solution used here are shown by abbreviation, and their structures are as follows:

[0091] [ka]

[0092] EMI R1=Et, R2=Me BMI R1=n-Bu, R2=Me HMeIm R1=Me, R2=H HBuIm R1=n-Bu, R2=H HHexIm R1=n-Hex, R2=H HOctIm R1=n-Oct, R2=H HDecIm R1=n-Dec, R2=H HDodeIm R1=n-Dode, R2=H

[0093] [ka]

[0094] DEME R1=Et R2=Et, R3=CH2CH2OCH3, R4=Me EtNH3 R1=Et R2=H, R3=H, R4=H BuNH3 R1=Bu R2=H, R3=H, R4=H

[0095] [ka]

[0096] P14 R1=Me, R2=n-Bu MePyr R1 = Me, R2 = H MEMP R1 = CH2CH2OCH3, R2 = Me

[0097] [ka] HDBN R=H

[0098] [ka]

[0099] HDBU R=H

[0100] [ka]

[0101] EtPy R=Et

[0102] Here, Me represents a methyl group, Et represents an ethyl group, Bu represents a butyl group, Hex represents a hexyl group, Oct represents an octyl group, Dec represents a decyl group, and Dode represents a dodecyl group.

[0103] <anion> The anion abbreviations and names or structures are as follows: AcO acetate anion PF6 hexafluorophosphate anion BF4 tetrafluoroborate anion CH3SO3 methanesulfonate anion NO3 nitrate anion CH3CH2CO2 propionate anion CH3CH2CH2CO2 butanoic acid anion CH3(CH2)3CO2 Pentanoic acid anion CH3(CH2)4CO2 hexanoic acid anion CH3(CH2)5CO2 heptanoate anion CH3(CH2)6CO2 octanoate anion HCO2 formate anion CH3OCH2CH2CO2 3-Methoxypropionic acid anion CH3(CH2)3CH(C2H5)CO2 2-ethylhexanoic acid anion

[0104] [ka]

[0105] FSA R=F TFSA R=CF3

[0106] [Table 1]

[0107] [Table 2]

[0108] [Table 3]

[0109] [Example 46] A half drop of HDBN·CH3(CH2)6CO2 was dropped onto a silicon chip (2 cm square) with a 100 nm thermal oxide film using a dropper, and the chip was placed on a designated holder and placed in a vacuum heating device MILA-5000UHV (with turbomolecular pump, manufactured by Advance Riko Co., Ltd.) and the pressure was reduced at 25°C. After about 60 minutes, the vacuum level reached 3×10 -4 After confirming that the pressure had reached and stabilized at 10 Pa, heating was started at a rate of 10°C / min. The degree of vacuum began to decrease around 40°C, temporarily reaching 3.3 x 10 -3 The pressure reached 100 Pa, then increased, and by the time 100°C was reached, the pressure had dropped below the pressure before starting. After that, heating was stopped, and after confirming that the temperature had returned to room temperature, the silicon chip was removed and the disappearance of the ionic liquid was visually confirmed. It is believed that the ionic liquid volatilized while the vacuum was changing in the temperature range above 40°C.

[0110] The results in Table 1 show that cleaning solutions made from ionic liquids and cleaning solutions made from mixed solutions of a predetermined composition do not volatilize at 25°C and low vacuum. The results in Table 2 show that cleaning solutions made from ionic liquids and cleaning solutions made from mixed solutions of a predetermined composition can be removed by increasing the ambient temperature even under reduced pressure. Furthermore, as shown in Table 3, it is clear that ionic liquids do not volatilize under high vacuum and can be used as cleaning solutions. Furthermore, as shown in Example 46, the cleaning solution of the present invention can be removed at 10 -4 It exists without volatilizing even under high vacuum conditions at the Pa level, and can be removed by subsequent heat treatment.

[0111] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the components of the above-described embodiments may be arbitrarily combined. Such an arbitrary combination naturally provides the functions and effects of each of the components involved in the combination, and also provides other functions and effects that are apparent to those skilled in the art from the description of this specification.

[0112] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0113] Note that the following configuration examples also fall within the technical scope of the present disclosure. (1) A cleaning solution consisting of an ionic liquid or a mixture with an elevated boiling point, which does not volatilize at 25°C and low vacuum. (2) The cleaning solution according to (1) above, wherein the ionic liquid is a protic ionic liquid. (3) The cleaning solution according to (1), wherein the ionic liquid is a protic ionic liquid or the mixture contains an amine. (4) A cleaning method comprising the step of cleaning an object to be cleaned under reduced pressure using the cleaning liquid according to any one of (1) to (3) above. (5) After the cleaning step, the cleaning solution is removed under reduced pressure, and the object to be cleaned is dried. The cleaning method according to (4) above, wherein the drying step involves volatilizing and removing the cleaning solution by applying a high vacuum, heating, reacting with ammonia gas, or a combination of two or more of these. (6) A substrate processing method, comprising the step of cleaning a substrate, the surface of which has been etched, under reduced pressure using the cleaning liquid according to any one of (1) to (3). (7) After the cleaning step, the cleaning solution is removed under reduced pressure, and the substrate is dried; The substrate processing method according to (6) above, wherein the drying step volatilizes and removes the cleaning liquid by applying a high vacuum, heating, reacting with ammonia gas, or a combination of two or more of these. (8) The substrate processing method according to (6) or (7), further comprising the step of etching the metal of the substrate using an etching solution before the cleaning step. (9) The substrate processing method according to (9), wherein the cleaning step includes a step of flushing out the etching solution on the etched substrate with the cleaning solution. (10) The substrate processing method according to (8) or (9), wherein the cleaning liquid and the etching liquid are the same liquid. (11) The substrate processing method according to any one of (8) to (10), wherein the etching liquid comprises an ionic liquid composed of a carboxylic acid anion and a quaternary cation, and / or a protic ionic liquid. (12) The substrate processing method according to any one of (8) to (10), wherein the etching solution is an ionic liquid containing 10 ppm or more of at least one of a halide anion, a carboxylate anion, and a protic ionic liquid. (13) A substrate processing apparatus having a cleaning unit that cleans a substrate having an etched metal surface under reduced pressure using a cleaning liquid consisting of an ionic liquid or a mixture that increases the boiling point and does not volatilize at 25°C in a low vacuum. (14) The cleaning unit further removes the cleaning solution under reduced pressure after cleaning and dries the substrate; The substrate processing apparatus according to (13), wherein, in the drying by the cleaning unit, the cleaning liquid is volatilized and removed by high vacuum, heating, reaction with ammonia gas, or a combination of two or more of these. (15) The substrate processing apparatus according to (13) or (14), further comprising an etching unit that etches the metal of the substrate using an etching solution before cleaning by the cleaning unit. (16) The substrate processing apparatus according to (15), wherein the cleaning unit further flushes out the etching liquid on the etched substrate with the cleaning liquid. (17) The substrate processing apparatus according to (15) or (16), wherein the cleaning liquid and the etching liquid are the same liquid. (18) The substrate processing apparatus according to any one of (15) to (17), wherein the etching liquid is an ionic liquid containing a carboxylic acid anion and a quaternary cation, and / or a protic ionic liquid. (19) The substrate processing apparatus according to any one of (15) to (17), wherein the etching liquid is an ionic liquid containing 10 ppm or more of at least one of halide anions, carboxylate anions, and protic ionic liquids. [Explanation of symbols]

[0114] 1. Wafer processing equipment 10 Atmospheric Section 11 Pressure reducing section 20, 21 Load lock module 30 Loader Module 31 Hoop 32 Loading Port 40 Conveyor mechanism 41 Transfer arm 42 Turntable 43 Foundation 44 Guide rail 50 Transfer Module 51 Decompression transport chamber 60, 61 Processing module 62, 63 Gate valve 70 Transport Robot 71 Transfer arm 72 Fork 80 Control Unit 100 Chambers 101 Exhaust port 102 Supply port 110 Rotation holding part 111 Base 111a Top plate 111b Shaft 111c Hollow part 112 Holding part 113 Rotation mechanism 114 Bearings 115 Gas supply section 115a Channel 116 Source 117 Supply equipment group 118 Lifting mechanism 120 cups 121 Discharge pipe 122 Exhaust pipe 130 First Arm 131 Etching nozzle 132 Moving mechanism 133 Source 134 Supply equipment group 140 Second Arm 141 Cleaning nozzle 142 Moving mechanism 143 Source 144 Supply equipment group 150 Exhaust system 160 Source 161 Supply equipment group H storage medium W wafer

Claims

1. A cleaning liquid comprising an ionic liquid or a mixture with an elevated boiling point, which does not volatilize at 25°C and low vacuum.

2. The cleaning solution according to claim 1 , wherein the ionic liquid is a protic ionic liquid.

3. The cleaning solution according to claim 1 , wherein the ionic liquid is a protic ionic liquid or the mixture contains an amine.

4. A cleaning method comprising the step of cleaning an object to be cleaned under reduced pressure using the cleaning liquid according to any one of claims 1 to 3.

5. The method further includes a step of removing the cleaning liquid under reduced pressure and drying the object to be cleaned after the cleaning step, 5. The cleaning method according to claim 4, wherein the drying step volatilizes and removes the cleaning liquid by applying a high vacuum, heating, reacting with ammonia gas, or a combination of two or more of these.

6. A substrate processing method comprising the step of cleaning a substrate, the metal of which has been etched, under reduced pressure using the cleaning solution according to any one of claims 1 to 3.

7. After the cleaning step, the cleaning solution is removed under reduced pressure and the substrate is dried; 7. The substrate processing method according to claim 6, wherein the drying step volatilizes and removes the cleaning liquid by applying a high vacuum, heating, reacting with ammonia gas, or a combination of two or more of these.

8. The substrate processing method according to claim 6 , further comprising the step of etching the metal of the substrate using an etching solution before the cleaning step.

9. 9. The substrate processing method according to claim 8, wherein the cleaning step includes the step of washing away the etching liquid on the etched substrate with the cleaning liquid.

10. The substrate processing method according to claim 8 , wherein the cleaning liquid and the etching liquid are the same liquid.

11. 9. The substrate processing method according to claim 8, wherein the etching liquid comprises an ionic liquid containing a carboxylic acid anion and a quaternary cation, or / and a protic ionic liquid.

12. 9. The substrate processing method according to claim 8, wherein the etching solution is an ionic liquid containing 10 ppm or more of at least one of a halide anion, a carboxylate anion, and a protic ionic liquid.

13. A substrate processing apparatus including a cleaning unit that cleans a substrate having a metal etched from its surface under reduced pressure using a cleaning liquid that is made of an ionic liquid or a mixture that increases the boiling point and does not volatilize at 25°C in a low vacuum.

14. the cleaning unit further removes the cleaning solution under reduced pressure after cleaning and dries the substrate; The substrate processing apparatus according to claim 13 , wherein, in the drying by the cleaning unit, the cleaning liquid is volatilized and removed by a high vacuum, heating, reaction with ammonia gas, or a combination of two or more of these.

15. The substrate processing apparatus according to claim 13 or 14, further comprising an etching unit that etches the metal of the substrate using an etching solution before cleaning by the cleaning unit.

16. The substrate processing apparatus according to claim 15 , wherein the cleaning unit further flushes away the etching liquid on the etched substrate with the cleaning liquid.

17. The substrate processing apparatus according to claim 15 , wherein the cleaning liquid and the etching liquid are the same liquid.

18. The substrate processing apparatus according to claim 15, wherein the etching liquid comprises an ionic liquid containing a carboxylic acid anion and a quaternary cation, and / or a protic ionic liquid.

19. 16. The substrate processing apparatus according to claim 15, wherein the etching solution is an ionic liquid containing 10 ppm or more of at least one of halide anions, carboxylate anions, and protic ionic liquids.

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