Metal etching solution, metal etching method, substrate processing method and substrate processing apparatus

Abstract

To provide an etching solution for metals having low volatility, a metal etching method using this etching solution, a substrate processing method, and a substrate processing apparatus.SOLUTION: A metal etching solution comprises an ionic liquid containing at least one of a halide anion, a carboxylate anion, or a protonic ionic liquid.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a metal etching solution, a metal etching method, a substrate processing method, and a substrate processing apparatus. [Background technology]

[0002] In the manufacturing process of semiconductor devices and the like, metal on a substrate such as a semiconductor wafer (hereinafter referred to as "wafer") is etched to form, for example, a metal wiring pattern. An etching solution may be used for etching the metal. Patent Document 1 discloses a copper etching solution. [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, metal etching using an etching solution has conventionally been carried out under atmospheric pressure, and there is a risk that the etching solution will volatilize when exposed to a reduced pressure atmosphere.

[0005] The present invention has been made in view of the above circumstances, and provides a metal etching liquid having low volatility, a metal etching method using the etching liquid, a substrate processing method, and a substrate processing apparatus. [Means for solving the problem]

[0006] One aspect of the present invention is a metal etching solution characterized by comprising an ionic liquid containing at least one of a halide anion, a carboxylate anion, and a protic ionic liquid.

[0007] According to one aspect of the present invention, an ionic liquid containing at least one of a halide anion, a carboxylate anion, and a protic ionic liquid is non-volatile and has the ability to dissolve metals, and therefore, an etching solution for metals having low volatility can be provided. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a metal etching liquid having low volatility, a metal etching method using the etching liquid, a substrate processing method, and a substrate processing apparatus. [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] As a result of extensive research conducted by the present inventors to achieve the above-mentioned object, they have found that, among ionic liquids having low volatility, the following ionic liquids have the ability to dissolve metals, and are capable of dissolving metals including an oxide film of the metal even if the metal has an oxide film on its surface. Ionic liquids containing carboxylate anions ·Ionic liquids containing halide anions Ionic liquids, including protic ionic liquids

[0011] The metal etching solution, substrate processing method, and substrate processing apparatus according to this embodiment are based on the above findings.

[0012] Hereinafter, a substrate processing method and a substrate processing apparatus according to the present embodiment will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0013] <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.

[0014] 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."

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The decompression unit 11 has a transfer module 50, a processing module 60 as an etching unit, and another processing module 61 that performs a process on the wafer W different from that performed by the processing module 60. The interiors of the transfer module 50 and the processing modules 60, 61 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. 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.

[0020] 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.

[0021] 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.

[0022] The processing module 60 etches the metal on the wafer W using an etching solution. In this embodiment, the processing module 60 performs metal etching on the wafer W using the etching solution 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 solution. Although the etching rate varies depending on the etching solution, the higher the temperature of at least one of the wafer W and the etching solution, the higher the etching rate. Therefore, a desired etching rate can be obtained by adjusting the temperature of at least one of the wafer W and the etching solution according to the etching solution. Furthermore, in this embodiment, the processing module 60 cleans the wafer W, whose surface metal has been etched, using a cleaning solution under reduced pressure. That is, in this embodiment, the processing module 60 functions not only as an etching unit but also as a cleaning unit. 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] <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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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 .

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Additionally, a first arm 130 and a second arm 140 are provided above the cup 120 within the chamber 100 .

[0038] 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.

[0039] 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.

[0040] The etching liquid supplied from the etching nozzle 131 is an ionic liquid containing a carboxylate anion, specifically, an ionic liquid obtained by diluting an ionic liquid consisting of a carboxylate anion and a quaternary cation as a first ionic liquid having the ability to dissolve metals with a second ionic liquid having a low ability to dissolve metals. 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. 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 a protic ionic liquid, which is a first ionic liquid capable of dissolving metals, or may be an ionic liquid obtained by diluting this protic ionic liquid with a second ionic liquid having a low ability to dissolve metals. Examples of the second ionic liquid that serves as a diluent are as described above. A protic ionic liquid is an ionic liquid synthesized by neutralizing a Brønsted base and a Brønsted 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. 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, for example, 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 may be the same as the ionic liquid used as the etching liquid, i.e., the cleaning liquid and the etching liquid may be the same liquid. Specifically, the cleaning liquid may be an ionic liquid obtained by diluting a first ionic liquid as an etching agent capable of dissolving metals with a second ionic liquid as a diluent having low metal dissolving ability. That is, 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 contain a second ionic liquid having a low ability to dissolve metals. As with the diluent described above, examples of the second ionic liquid used in the cleaning liquid include quaternary salt ionic liquids formed from anions other than carboxylic acid, but a protic ionic liquid having a low ability to dissolve metals may also be used in the cleaning liquid. In this case, the protic ionic liquid is not particularly limited as long as it has a lower ability to dissolve metals, i.e., an etching ability, than the first ionic liquid used as the etching agent.

[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. As an example of a combination of the above two types of liquids, a combination of a liquid amine and a liquid acid is preferable. 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 thereof, it is preferable that it 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] 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.

[0052] 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.

[0053] <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).

[0054] (Step S1) First, the wafer W is transferred from outside the wafer processing apparatus 1 to the processing module 60.

[0055] 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.

[0056] 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.

[0057] (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.

[0058] (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.

[0059] Specifically, in this step, the metal formed on the wafer W is etched under reduced pressure with an etching solution.

[0060] 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.

[0061] 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, since 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.

[0062] 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.

[0063] (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.

[0064] (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.

[0065] 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 to shake off a certain amount of the cleaning liquid from the wafer W.

[0066] (Step S3) The wafer W processed in the processing module 60 is transferred to the processing module 61.

[0067] 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.

[0068] (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.

[0069] (Step S5) Then, the wafer W is transferred from the processing module 61 to the outside of the wafer processing apparatus 1.

[0070] 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.

[0071] This completes the series of processes performed by the wafer processing apparatus 1.

[0072] <Major Effects of This Embodiment> As described above, in this embodiment, an etching solution for metal is used that is made of the following ionic liquids, which are low-volatility ionic liquids and have the ability to dissolve metals. Ionic liquids containing carboxylate anions, ionic liquids containing halide anions, and ionic liquids containing protic ionic liquids, each of which may be used alone or in combination Furthermore, even if an oxide film of the metal exists on the surface of the metal, these dissolve the metal including the oxide film. Therefore, according to this embodiment, metal etching using an etching solution can be performed under reduced pressure, which prevents the metal on the wafer W from being exposed to an atmosphere with high concentrations of water and oxygen during etching, thereby preventing oxides of the metal from being formed during or immediately after etching.

[0073] Furthermore, since metal etching using an etching solution can be performed under reduced pressure, by combining it with the following (A) to (C), the metal is not exposed to an atmosphere with high water and oxygen concentrations before a desired layer is formed on the metal remaining on the wafer W after etching. (A) Cleaning the wafer W with a cleaning liquid in an atmosphere with low water and oxygen concentrations (specifically, under reduced pressure). (B) Removing the cleaning liquid in an atmosphere with low water and oxygen concentrations (specifically, under reduced pressure), that is, drying the wafer W. (C) 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 etched metal and the desired layer.

[0074] <Modification> As described above, the etching liquid and the cleaning liquid may be the same. In this case, the cleaning nozzle 141 may be omitted. This simplifies the configuration of the processing module 60, thereby reducing costs.

[0075] The inventors have confirmed that the above-mentioned etching solution can dissolve metals and oxide films on the surfaces of the metals even in an atmosphere of an inert gas such as nitrogen gas (specifically, in an atmosphere at atmospheric pressure). Therefore, etching of metal using an etching solution may be performed under an atmosphere of an inert gas such as nitrogen gas, rather than under reduced pressure as in the above example. That is, the atmosphere with low water and oxygen concentrations around the wafer W during etching of metal using an etching solution may be realized by an inert gas atmosphere. In this case, too, the metal on the wafer W is not exposed to an atmosphere with high water and oxygen concentrations, so that it is possible to suppress the formation of oxides of the metal during or immediately after etching.

[0076] In the above example, the cleaning of the wafer W using the cleaning liquid is performed under reduced pressure. Alternatively, the cleaning of the wafer W using the cleaning liquid 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 cleaning using the cleaning liquid may be realized by an atmosphere of an inert gas.

[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] The present inventors have confirmed that the above-mentioned etching solution can dissolve metal and the oxide film on the surface of the metal even in an atmospheric pressure atmosphere, which is an atmospheric gas atmosphere. Therefore, etching of metal using the etching solution may be carried out in an atmospheric pressure atmosphere in which the concentrations of water and oxygen are relatively high. Furthermore, at least one of cleaning of the wafer W using a cleaning liquid, drying of the wafer W, and transfer of the wafer W to the processing module 61 after drying may be performed in an atmospheric atmosphere.

[0080] In the above example, one processing module 60 functions not only as an etching unit but also as a cleaning 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. [Example]

[0084] Next, examples of the present invention will be described, but the present invention should not be construed as being limited to the following examples.

[0085] Etching solutions having the compositions shown in Table 1 were prepared, and etching was performed under the conditions described below. The metal dissolving ability of the etching solutions was evaluated using the evaluation method described below. Among the etching solutions shown in Table 1, those with "◯" in the PIL column indicate that the first ionic liquid is a protic ionic liquid, and those with "-" in the PIL column indicate that the first ionic liquid is an ionic liquid other than a protic ionic liquid.

[0086] <cation> The cations of the etching solutions (ionic liquids) used in this study are shown by abbreviations, and their structures are as follows:

[0087] [ka] EMI R1=Et, R2=Me

[0088] [ka] BuNH3 R1=Bu R2=H, R3=H, R4=H DEME R1=Et R2=Et, R3=CH2CH2OCH3, R4=Me

[0089] [ka]

[0090] MEMP R1 = CH2CH2OCH3, R2 = Me

[0091] [ka]

[0092] HDBN R=H

[0093] [ka]

[0094] EtPy R=CH2CH3

[0095] <anion> The anion abbreviations and names or structures are as follows:

[0096] AcO acetate anion NO3 nitrate anion CH3CH2CO2 propionate anion CL chloride anion Br bromide anion TsO p-toluenesulfonate anion BF4 tetrafluoroborate anion

[0097] [ka]

[0098] TFSA R=CF3 FSA R=F

[0099] <Test board used> A silicon substrate with a 50 nm thick metal layer formed on its surface was prepared as a test substrate, and test specimens were fabricated from the test substrate. The types of metals on the test substrate, i.e., the metals to be etched, are listed in Table 1.

[0100] <Etching conditions> Droplets or a liquid film of the etching solution were formed on the test piece, and the area where the droplets or liquid film were formed was etched. The ambient temperature in which the test piece was present during processing varied depending on the example, but was performed at room temperature, 40°C, 60°C, 80°C, 100°C, and 200°C. After the liquid film was formed at temperatures other than room temperature, the substrate was placed in a vacuum dryer at a specified temperature and observed. The pressure and atmosphere surrounding the test piece during processing were atmospheric pressure and air, respectively. The processing time (the elapsed time after the formation of the etching droplets or liquid film) is shown in Table 1. After etching, the test piece was washed with water and dried, and the following evaluations were performed.

[0101] <Evaluation of dissolution ability> Regarding the evaluation of the substrate after etching, the "Room Temperature" column of the "Solubility" section in Table 1 was marked with a "◎" if the underlying layer of the metal layer was visually confirmed when the ambient temperature in which the test specimen was present was room temperature; a "○" if the underlying layer was not visually confirmed, but there was a visible surface change in the area where the etching droplets or liquid film had formed, and it was clearly etched; and a "△" if there was a visible surface change in the area where the etching droplets or liquid film had formed, but it was difficult to recognize as clear etching. In the "Time to Complete Dissolution" column, the ambient temperature in which the test specimen was present was 40°C, 60°C, 80°C, 100°C, or 200°C. The time at which that state was reached was recorded in parentheses. In the "Time to Complete Dissolution" column, if no visible discoloration was observed in the area where the etching droplets or liquid film had formed, an "×" was recorded. Blank cells in Table 1 indicate conditions where the test was not performed.

[0102] [Table 1]

[0103] The results in Table 1 indicate that the first ionic liquid, i.e., an ionic liquid composed of a carboxylate anion and a quaternary cation, an ionic liquid composed of a halide anion and a quaternary cation, or a protic ionic liquid diluted with a quaternary salt ionic liquid composed of an anion other than carboxylate, has the ability to dissolve copper, cobalt, molybdenum, and tungsten, and that the etching rate increases with heating. The etching rate also increases with increasing the content of the first ionic liquid. Furthermore, because the results in Table 1 were obtained under ambient conditions, copper should have formed an oxide layer on its surface. Therefore, these results also indicate that the ionic liquid composed of a carboxylate anion and a quaternary cation, an ionic liquid composed of a halide anion and a quaternary cation, or a protic ionic liquid diluted with a quaternary salt ionic liquid composed of an anion other than carboxylate not only dissolves and removes copper, cobalt, molybdenum, and tungsten, but also dissolves and removes the oxide layers on the surfaces of these metals. In addition, the present inventors have confirmed that ionic liquids consisting of a carboxylate anion and a quaternary cation, an ionic liquid consisting of a halide anion and a quaternary cation, or a protic ionic liquid diluted with a quaternary salt ionic liquid consisting of an anion other than carboxylate, have the ability to dissolve aluminum-copper alloys or aluminum-nickel alloys.

[0104] 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.

[0105] 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.

[0106] Note that the following configuration examples also fall within the technical scope of the present disclosure. (1) A metal etching solution comprising an ionic liquid containing at least one of a halide anion, a carboxylate anion, and a protic ionic liquid. (2) The metal etching solution according to (1), wherein the halide anion is at least one of a chloride ion and a bromide ion. (3) The metal etching solution according to (1), wherein the carboxylate anion is an acetate anion. (4) The metal etching solution according to any one of (1) to (3) above, wherein the ionic liquid contains 10 ppm or more of at least one of halide anions and carboxylate anions. (4') The metal etching solution according to any one of (1) to (4), wherein the etching solution also etches an oxide film on the surface of the metal. (4") The metal etching solution according to any one of (1) to (4) and (4'), wherein the metal is copper, tungsten, molybdenum, cobalt, an aluminum-copper alloy, or an aluminum-nickel alloy. (5) A method for etching the metal using the etching solution according to any one of (1) to (4). (6) The method for etching a metal according to (5) above, wherein the oxide film on the surface of the metal and the metal itself are etched using the etching solution. (7) The method for etching a metal according to (5) or (6), wherein the metal is copper, tungsten, molybdenum, cobalt, an aluminum-copper alloy, or an aluminum-nickel alloy. (8) A substrate processing method, comprising the step of etching the metal formed on a substrate using the etching solution according to any one of (1) to (4) above. (9) The substrate processing method according to (8), wherein the etching step etches the metal under reduced pressure. (10) The substrate processing method according to (8), wherein the etching step etches the metal in an inert gas atmosphere. (11) The substrate processing method according to (8), wherein at least one of the substrate and the etching solution is heated in the etching step. (12) A substrate processing apparatus comprising an etching unit that etches the metal formed on a substrate using the etching solution according to any one of (1) to (4). (13) The substrate processing apparatus according to (12), wherein the etching unit etches the metal on the substrate using the etching solution under reduced pressure. (14) The substrate processing apparatus according to (12), wherein the etching unit etches the metal on the substrate using the etching solution in an inert gas atmosphere. (15) The substrate processing apparatus according to (12), wherein the etching unit heats at least one of the substrate and the etching solution during etching. [Explanation of symbols]

[0107] 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 Transport 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 unit 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 metal etching solution comprising an ionic liquid containing at least one of a halide anion, a carboxylate anion, and a protic ionic liquid.

2. 2. The metal etching solution according to claim 1, wherein the halide anion is at least one of a chloride ion and a bromide ion.

3. 2. The metal etching solution according to claim 1, wherein the carboxylate anion is an acetate anion.

4. The metal etching solution according to claim 1 , wherein the ionic liquid contains at least one of a halide anion, a carboxylate anion, and a protic ionic liquid in an amount of 10 ppm or more.

5. A method for etching a metal using the etching solution according to any one of claims 1 to 4.

6. The metal etching method according to claim 5 , wherein the oxide film on the surface of the metal and the metal itself are etched using the etching solution.

7. 6. The method for etching a metal according to claim 5, wherein the metal is copper, tungsten, molybdenum, cobalt, an aluminum-copper alloy, or an aluminum-nickel alloy.

8. A substrate processing method, comprising the step of etching the metal formed on a substrate using the etching solution according to any one of claims 1 to 4.

9. The substrate processing method according to claim 8 , wherein the etching step etches the metal under reduced pressure.

10. 9. The substrate processing method according to claim 8, wherein the etching step etches the metal in an inert gas atmosphere.

11. 9. The substrate processing method according to claim 8, wherein at least one of the substrate and the etching solution is heated in the etching step.

12. 5. A substrate processing apparatus comprising an etching unit that etches the metal formed on a substrate using the etching solution according to claim 1.

13. The substrate processing apparatus according to claim 12 , wherein the etching unit etches the metal on the substrate using the etching solution under reduced pressure.

14. The substrate processing apparatus according to claim 12 , wherein the etching unit etches the metal on the substrate using the etching solution in an inert gas atmosphere.

15. The substrate processing apparatus according to claim 12 , wherein the etching unit heats at least one of the substrate and the etching liquid during etching.

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