Plating solution and plating method

Abstract

A plating solution according to one embodiment of the present disclosure contains: an ionic liquid that contains an aluminum halide; and a reducing agent that contains at least one of hydrazine and a hydrazine derivative. In addition, the content of the aluminum halide in the ionic liquid is 30 (mol%) to 60 (mol%).

Description

[Technical Field]

[0001] The present disclosure relates to a plating solution and a plating method. [Background technology]

[0002] Conventionally, a method for forming an aluminum film on a substrate by electroless plating is known, and this conventional technique uses a plating solution containing an alkali metal element (such as lithium or sodium) hydride as a reducing agent (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-13845 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that allows for efficient formation of an aluminum film on a semiconductor substrate. [Means for solving the problem]

[0005] A plating solution according to one embodiment of the present disclosure includes an ionic liquid containing an aluminum halide and a reducing agent containing at least one of hydrazine and a hydrazine derivative, wherein the aluminum halide content in the ionic liquid is 30 (mol%) to 60 (mol%). [Effects of the Invention]

[0006] According to the present disclosure, an aluminum film can be efficiently formed on a semiconductor substrate. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the configuration of a substrate processing apparatus according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of the plating processing unit according to the embodiment. [Figure 3] FIG. 3 is a flowchart showing a processing procedure in the plating process according to the embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between the molar ratio of aluminum halide in the ionic liquid and the abundance ratio of anions in the ionic liquid. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the plating solution and plating method disclosed herein will be described in detail with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments shown below. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of elements may differ from reality. Furthermore, the dimensional relationships and ratios may differ between the drawings.

[0009] A conventional method for forming an aluminum film on a substrate using electroless plating is known. This conventional technique uses a plating solution containing an alkali metal hydride (such as lithium or sodium) as a reducing agent.

[0010] On the other hand, when an aluminum film is formed on the surface of a semiconductor substrate using this conventional technology, the alkali metal elements contained in the reducing agent diffuse into the interior of the semiconductor substrate, resulting in contamination of the semiconductor substrate.

[0011] Furthermore, in this conventional technique, a highly reactive hydride is used as a reducing agent, which requires careful handling in some cases. Furthermore, in this conventional technique, the aluminum film formation rate is slow, so it takes a long time (e.g., several hours) to obtain a sufficient film thickness, making it difficult to efficiently form the aluminum film.

[0012] Therefore, there is a need for a technology that can overcome the above-mentioned problems and efficiently form an aluminum film on a semiconductor substrate.

[0013] <Outline of substrate processing equipment> First, a schematic configuration of a substrate processing apparatus 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the substrate processing apparatus 1 according to an embodiment. In the following, to clarify the positional relationships, mutually orthogonal X-axis, Y-axis, and Z-axis are defined, and the positive direction of the Z-axis is defined as the vertically upward direction.

[0014] 1, the substrate processing apparatus 1 includes a loading / unloading station 2 and a processing station 3. The loading / unloading station 2 and the processing station 3 are provided adjacent to each other.

[0015] The loading / unloading station 2 includes a carrier mounting table 11 and a transport unit 12. On the carrier mounting table 11, a plurality of carriers C are mounted, each of which accommodates a plurality of substrates, in this embodiment, semiconductor wafers (hereinafter also referred to as substrates W), in a horizontal state.

[0016] A plurality of load ports are arranged on the carrier mounting table 11 adjacent to the transfer section 12, and one carrier C is mounted on each of the plurality of load ports.

[0017] The transport section 12 is provided adjacent to the carrier mounting table 11 and includes a substrate transport device 13 and a transfer section 14. The substrate transport device 13 includes a substrate holding mechanism that holds the substrate W. The substrate transport device 13 is capable of moving horizontally and vertically and rotating about a vertical axis, and transports the substrate W between the carrier C and the transfer section 14 using the substrate holding mechanism.

[0018] The processing station 3 is provided adjacent to the transport section 12. The processing station 3 includes a transport section 15 and a plurality of plating sections 5. The plurality of plating sections 5 are provided side by side on both sides of the transport section 15. The configuration of the plating sections 5 will be described later.

[0019] The transport section 15 includes a substrate transport device 17 therein. The substrate transport device 17 includes a substrate holding mechanism that holds the substrate W. The substrate transport device 17 is capable of moving in the horizontal and vertical directions and rotating about a vertical axis, and transports the substrate W between the delivery section 14 and the plating processing section 5 using the substrate holding mechanism.

[0020] The substrate processing apparatus 1 also includes a control device 9. The control device 9 is, for example, a computer, and includes a control unit 91 and a storage unit 92. The storage unit 92 stores programs for controlling various processes executed in the substrate processing apparatus 1. The control unit 91 controls the operation of the substrate processing apparatus 1 by reading and executing the programs stored in the storage unit 92.

[0021] The program may be recorded on a computer-readable storage medium and installed into the storage unit 92 of the control device 9 from the storage medium.

[0022] Examples of computer-readable storage media include hard disks (HDs), flexible disks (FDs), compact disks (CDs), magneto-optical disks (MOs), and memory cards.

[0023] In the substrate processing apparatus 1 configured as described above, first, the substrate transport device 13 of the loading / unloading station 2 removes the substrate W from the carrier C placed on the carrier placement table 11, and places the removed substrate W on the transfer section 14.

[0024] The substrate W placed on the transfer section 14 is taken out of the transfer section 14 by the substrate transport device 17 of the processing station 3, transported to the plating processing section 5, and processed by the plating processing section 5.

[0025] The substrate W processed by the plating processing section 5 is carried out from the plating processing section 5 by the substrate transport device 17 and placed on the delivery section 14. Then, the processed substrate W placed on the delivery section 14 is returned to the carrier C on the carrier mounting table 11 by the substrate transport device 13.

[0026] <Overview of Plating Department> Next, the schematic configuration of the plating processing section 5 will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of the plating processing section 5 according to an embodiment. The plating processing section 5 is configured, for example, as a single-wafer processing unit that processes substrates W one by one.

[0027] The plating processing section 5 is configured to perform liquid processing including electroless plating processing, and includes a chamber 20, a substrate holding section 30, a plating solution supply section 40, and a processing solution supply section 60.

[0028] The substrate holding unit 30 is disposed in the chamber 20 and holds the substrate W horizontally. The plating solution supply unit 40 supplies a plating solution M to the surface (upper surface) of the substrate W held by the substrate holding unit 30. The processing solution supply unit 60 supplies various processing solutions to the surface (upper surface) of the substrate W held by the substrate holding unit 30.

[0029] The substrate holding unit 30 has a holding unit 31, a support unit 32, and a drive unit 33. The holding unit 31 holds the substrate W horizontally. The support unit 32 is a member extending in the vertical direction, and its base end is rotatably supported by the drive unit 33, with its tip end supporting the holding unit 31 horizontally. The drive unit 33 rotates the support unit 32 around a vertical axis.

[0030] The substrate holding unit 30 rotates the support member 32 using the drive unit 33, thereby rotating the holding unit 31 supported by the support member 32, and thereby rotating the substrate W held by the holding unit 31.

[0031] A holding member 34 that holds the substrate W from the side is provided on the upper surface of the holding part 31 of the substrate holding unit 30. The substrate W is held horizontally by the holding member 34 at a slight distance from the upper surface of the holding part 31. The substrate W is held by the holding part 31 with the surface on which substrate processing is performed facing upward.

[0032] The plating solution supply unit 40 has a nozzle 41 that discharges the plating solution M onto the substrate W held by the substrate holder 30 , and a plating solution supply source 42 that supplies the plating solution M to the nozzle 41 .

[0033] The plating solution M is supplied to the nozzle 41 from a plating solution supply source 42 via a valve 43 and a heater 44. The plating solution supply source 42 is, for example, a tank that stores the plating solution M.

[0034] The plating solution M is produced, for example, by mixing an ionic liquid L1 and a diluted reducing agent L2. The ionic liquid L1 contains an aluminum halide and a 1,3-dialkylimidazolium halide.

[0035] The aluminum halide contained in ionic liquid L1 is a compound represented by AlX3 (X represents a halogen atom). Examples of aluminum halides contained in ionic liquid L1 include aluminum fluoride (AlF3), aluminum chloride (AlCl3), aluminum bromide (AlBr3), and aluminum iodide (AlI3).

[0036] The aluminum halide used in the ionic liquid L1 according to this embodiment is preferably aluminum chloride or aluminum bromide, and more preferably anhydrous aluminum chloride from the viewpoints of low melting point and cost.

[0037] The 1,3-dialkylimidazolium halide contained in the ionic liquid L1 has an alkyl group with a carbon number of 1 to 12. The 1,3-dialkylimidazolium halide used in the ionic liquid L1 according to this embodiment is preferably 1-ethyl-3-methylimidazolium halide.

[0038] Furthermore, from the viewpoints of low melting point and cost, 1-ethyl-3-methylimidazolium chloride (hereinafter also referred to as "EMIC") is more preferable as the 1,3-dialkylimidazolium halide used in the ionic liquid L1 according to the embodiment.

[0039] In the embodiment, for example, an aluminum halide supplied from a first supply source 46 and a 1,3-dialkylimidazolium halide supplied from a second supply source 47 are mixed in a tank 48 to generate an ionic liquid L1 in the tank 48. The generated ionic liquid L1 is then supplied from the tank 48 to the plating solution supply source 42.

[0040] The diluted reducing agent L2 contains a reducing agent and an organic solvent. The reducing agent according to the embodiment contains at least one of hydrazine (N2H4) and a hydrazine derivative. The hydrazine derivative used in the diluted reducing agent L2 is at least one selected from methylhydrazine, dimethylhydrazine, phenylhydrazine, and benzophenone hydrazone.

[0041] The organic solvent used in the diluted reducing agent L2 is preferably at least one selected from benzene, toluene, and xylene.

[0042] In the embodiment, for example, a reducing agent supplied from the reducing agent supply source 49 and an organic solvent supplied from the organic solvent supply source 50 are mixed in a tank 51 to generate a diluted reducing agent L2 in the tank 51. The generated diluted reducing agent L2 is then supplied from the tank 51 to the plating solution supply source 42.

[0043] The nozzle 41 is connected to a nozzle moving mechanism 52. The nozzle moving mechanism 52 moves the nozzle 41. The nozzle moving mechanism 52 has an arm 53, a moving body 54, and a swivel / lift mechanism 55. The moving body 54 is a moving body with a built-in drive mechanism that can move along the arm 53. The swivel / lift mechanism 55 swivels and lifts / lowers the arm 53.

[0044] The nozzle 41 is attached to a moving body 54. The nozzle moving mechanism 52 can move the nozzle 41 between a position above the center of the substrate W held by the substrate holder 30 and a position above the periphery of the substrate W. The nozzle moving mechanism 52 can also move the nozzle 41 to a standby position located outside a cup 80, which will be described later, in a plan view.

[0045] The processing liquid supply unit 60 has a nozzle 61 that ejects a catalyst liquid onto the substrate W held by the substrate holding unit 30, and a catalyst liquid supply source 62 that supplies the catalyst liquid to the nozzle 61. The catalyst liquid is supplied to the nozzle 61 from the catalyst liquid supply source 62 via a valve 63. The catalyst liquid supply source 62 is, for example, a tank that stores the catalyst liquid.

[0046] The processing liquid supply unit 60 also has a nozzle 64 that ejects a cleaning liquid onto the substrate W held by the substrate holder 30, and a cleaning liquid supply source 65 that supplies the cleaning liquid to the nozzle 64. The cleaning liquid is supplied to the nozzle 64 from the cleaning liquid supply source 65 via a valve 66. The cleaning liquid supply source 65 is, for example, a tank that stores the cleaning liquid.

[0047] The processing liquid supply unit 60 also has a nozzle 67 that ejects a rinse liquid onto the substrate W held by the substrate holder 30, and a rinse liquid supply source 68 that supplies the rinse liquid to the nozzle 67. The rinse liquid is supplied to the nozzle 67 from the rinse liquid supply source 68 via a valve 69. The rinse liquid supply source 68 is, for example, a tank that stores the rinse liquid.

[0048] The catalytic solution contains metal ions that have catalytic activity for the oxidation reaction of the reducing agent in the plating solution M. In the electroless plating process, in order for the deposition of metal ions in the plating solution M to begin, it is necessary for the initial film surface (i.e., the surface to be plated of the substrate W) to have sufficient catalytic activity for the oxidation reaction of the reducing agent in the plating solution M.

[0049] Examples of such catalysts include those containing iron group elements (Fe, Co, Ni), platinum group elements (Ru, Rh, Pd, Os, Ir, Pt), Cu, Ag, or Au. The formation of a catalytically active metal film occurs through a substitution reaction. In this substitution reaction, the components that make up the substrate's surface to be plated act as reducing agents, and metal ions (e.g., Pd ions) in the catalytic solution are reduced and precipitated on the substrate's surface to be plated.

[0050] Examples of cleaning solutions that can be used include organic acids such as formic acid, malic acid, succinic acid, citric acid, and malonic acid, and hydrofluoric acid (DHF) diluted to a concentration that does not corrode the surface of the substrate to be plated. Examples of rinsing solutions that can be used include deionized water (DIW).

[0051] As the cleaning liquid, an alcohol such as absolute ethanol can be used.

[0052] The nozzles 61, 64, and 67 are connected to a nozzle movement mechanism 70. The nozzle movement mechanism 70 moves the nozzles 61, 64, and 67. The nozzle movement mechanism 70 has an arm 71, a moving body 72, and a swivel / lift mechanism 73. The moving body 72 is a moving body with a built-in drive mechanism that can move along the arm 71. The swivel / lift mechanism 73 swivels and lifts / lowers the arm 71.

[0053] The nozzles 61, 64, and 67 are attached to a movable body 72. The nozzle movement mechanism 70 can move the nozzles 61, 64, and 67 between a position above the center of the substrate W held by the substrate holder 30 and a position above the periphery of the substrate W. The nozzle movement mechanism 70 can also move the nozzles 61, 64, and 67 to a standby position located outside the cup 80 in a plan view.

[0054] A cup 80 is disposed around the substrate holder 30. The cup 80 receives various processing liquids (for example, plating liquid M, catalyst liquid, cleaning liquid, rinse liquid, etc.) that have splashed from the substrate W and discharges them outside the chamber 20. The cup 80 has an elevating mechanism 81 that drives the cup 80 up and down.

[0055] <Plating process details> Next, details of the plating process according to the embodiment will be described with reference to Figures 3 and 4. Figure 3 is a flowchart showing the processing procedure of the plating process according to the embodiment.

[0056] As shown in FIG. 3, the control unit 91 (see FIG. 1) first dissolves a reducing agent containing at least one of hydrazine and a hydrazine derivative in an organic solvent in the tank 51 (see FIG. 2) (step S1) to produce a diluted reducing agent L2 (see FIG. 2).

[0057] Thus, in the plating process according to the embodiment, at least one of hydrazine and a hydrazine derivative (hereinafter also referred to as "hydrazine, etc.") is used as the reducing agent in the electroless plating solution.

[0058] In this way, by using a highly reducing agent such as hydrazine as a reducing agent in the electroless plating solution, it is possible to efficiently form a plating film of aluminum, which has a high affinity for oxygen, at a high film formation rate.

[0059] In addition, in the embodiment, by using hydrazine or the like that does not contain alkali metal elements as a reducing agent in the electroless plating solution, contamination of the substrate W (see FIG. 2) by alkali metal elements can be suppressed.

[0060] In an embodiment, a reducing agent such as hydrazine may be dissolved in an organic solvent before preparing the plating solution M. This allows the preparation of a plating solution M with more stable properties than when the reducing agent is directly mixed with the ionic liquid L1 (see FIG. 2) without being dissolved in an organic solvent.

[0061] In parallel with the process of step S1, the control unit 91 mixes an aluminum halide and a 1,3-dialkylimidazolium halide in the tank 48 (see FIG. 2) to produce an ionic liquid L1 (step S2).

[0062] Thus, in this embodiment, the plating solution M is not produced from an aqueous solution containing an aluminum halide, but from an ionic liquid L1 containing an aluminum halide. This "ionic liquid" is also called a room-temperature molten salt, and refers to a salt that exists in a liquid state at room temperature.

[0063] In an embodiment, by generating the plating solution M using an ionic liquid, which is a non-aqueous liquid, even aluminum, which has a high affinity for oxygen and a deposition potential lower than that of hydrogen, can be stably present as ions in the plating solution M.

[0064] In the treatment of step S2, the content of aluminum halide in ionic liquid L1 is preferably 30 (mol %) to 60 (mol %). The reason for this will be explained with reference to Fig. 4. Fig. 4 is a diagram showing the relationship between the molar ratio of aluminum halide in ionic liquid L1 and the abundance ratio of anions in ionic liquid L1.

[0065] As shown in FIG. 4, when the molar ratio of aluminum halide in ionic liquid L1 is 30 (mol%) to 60 (mol%), the anions present in ionic liquid L1 are AlCl4 - becomes dominant.

[0066] On the other hand, when the molar ratio of aluminum halide in ionic liquid L1 is greater than 60 (mol%), the anions present in ionic liquid L1 are Al2Cl7 - In addition, when the molar ratio of aluminum halide in the ionic liquid L1 is less than 30 (mol%), the anion present in the ionic liquid L1 is Cl. -becomes dominant.

[0067] Here, in the existing technology, AlCl4 - Al2Cl7, which is thought to be more chemically unstable than - It has been thought that by incorporating a large amount of into the liquid or vapor phase, it is possible to efficiently form an aluminum film.

[0068] However, in the plating process according to the embodiment, hydrazine or the like is used as a reducing agent, so that AlCl4 - It was found that under the conditions where the above-mentioned is dominant, an electroless plating film of aluminum can be efficiently formed.

[0069] That is, in the embodiment, AlX4 contained in the ionic liquid L1 - (X is a halogen atom) is Al2X7 - This allows the aluminum film to be formed on the substrate W efficiently.

[0070] In the embodiment, the content of aluminum halide in the ionic liquid L1 is preferably 30 (mol%) to 60 (mol%), and more preferably 30 (mol%) to 50 (mol%), which allows an aluminum film to be efficiently formed on the substrate W.

[0071] In addition, in the embodiment, when a hydrazine derivative is used as the reducing agent, the hydrazine derivative is preferably at least one selected from methylhydrazine, dimethylhydrazine, phenylhydrazine, and benzophenone hydrazone.

[0072] In addition, the molar ratio of the 1,3-dialkylimidazolium halide in the ionic liquid L1 according to the embodiment is preferably 30 (mol%) to 70 (mol%) (however, the sum with the aluminum halide does not exceed 100 (mol%)). -Since the electroless plating process can be performed under the conditions where the above-mentioned is dominant, an aluminum film can be formed efficiently.

[0073] Furthermore, as the 1,3-dialkylimidazolium halide used in the ionic liquid L1 according to the embodiment, 1-ethyl-3-methylimidazolium halide is preferred because it has a wide composition range in which it forms a liquid phase at room temperature and has high electrical conductivity.

[0074] Returning to the description of Fig. 3, the control unit 91 then mixes the diluted reducing agent L2 produced in the process of step S1 and the ionic liquid L1 produced in the process of step S2 in the plating solution supply source 42 to produce a plating solution M (step S3).

[0075] In the treatment of step S3, it is preferable to add 0.01 to 0.5 moles, and more preferably 0.02 to 0.05 moles, of a reducing agent such as hydrazine per 1 L of ionic liquid L1. If the amount of reducing agent is less than this range, it is difficult to deposit aluminum over the entire substrate W, and the substrate W may become exposed.

[0076] Next, the control unit 91 transports the substrate W into the plating processing unit 5 (see FIG. 2) and holds the substrate W with the substrate holding unit 30 (see FIG. 2) (step S4).

[0077] As the substrate W, for example, a silicon substrate, a silicon substrate coated with W (tungsten), a silicon substrate coated with TiN (titanium nitride), or the like can be used.

[0078] The substrate W may be a silicon substrate coated with SiO2 (silicon oxide), a silicon substrate coated with Ru (ruthenium), or a HfO x A silicon substrate coated with hafnium oxide (HAF) may be used. xA silicon substrate with an (aluminum oxide) coating may also be used.

[0079] Next, the control unit 91 applies the catalyst to the surface of the substrate W by ejecting the catalyst solution from the nozzle 61 (see FIG. 2) onto the surface of the substrate W while rotating the substrate W at a given rotation speed (step S5).

[0080] In the plating processing unit 5, various processing solutions including a catalyst solution are discharged to the center of the substrate W and spread over the entire surface of the substrate W by centrifugal force caused by the rotation of the substrate W. Processing solutions scattered from the substrate W are discharged via a cup 80 (see FIG. 2).

[0081] Next, the control unit 91 causes the substrate W to rotate at a given rotation speed while discharging a rinse liquid from the nozzle 67 (see FIG. 2) onto the surface of the substrate W, thereby rinsing the surface of the substrate W (step S6). As a result, the catalyst liquid is washed away from the surface of the substrate W.

[0082] Next, the control unit 91 ejects plating solution M from the nozzle 41 (see FIG. 2) onto the surface of the substrate W while rotating the substrate W at a given low rotation speed, thereby forming a liquid film of plating solution M on the surface of the substrate W.

[0083] Then, the control unit 91 holds the liquid film of the plating solution M for a given time, thereby performing an electroless plating process on the surface of the substrate W, and forming an aluminum film on the surface of the substrate W (step S7).

[0084] The process of step S7 is preferably performed in a dry inert gas atmosphere in the chamber 20. This makes it possible to suppress oxidation during the formation of the aluminum film, thereby enabling the formation of an aluminum film with good properties.

[0085] The process of step S7 may be performed while raising the temperature of the plating solution M to be discharged onto the substrate W with the heater 44. For example, the process of step S7 may be performed while raising the temperature of the plating solution M within a range from room temperature to 60°C. This allows the aluminum film to be formed on the substrate W more efficiently.

[0086] Next, the control unit 91 causes the cleaning liquid to be discharged from the nozzle 64 (see FIG. 2) onto the surface of the substrate W while rotating the substrate W at a given rotation speed, thereby cleaning the surface of the substrate W (step S8). As a result, the plating liquid M is removed from the surface of the substrate W.

[0087] Next, the control unit 91 causes the substrate W to rotate at a given rotation speed while discharging a rinse liquid from the nozzle 67 (see FIG. 2) onto the surface of the substrate W, thereby rinsing the surface of the substrate W (step S9). As a result, the cleaning liquid is washed away from the surface of the substrate W.

[0088] Finally, the control unit 91 rotates the substrate W at a given high rotation speed to shake off the rinse liquid remaining on the substrate W and dry the substrate W (step S10). This completes a series of plating processes for one substrate W. [Example]

[0089] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0090] [Example 1] In a glove box with a dry argon atmosphere, anhydrous aluminum chloride (AlCl3) and EMIC were weighed out to a molar ratio of 50:50, and dissolved by stirring at around 50°C while being careful not to raise the temperature.

[0091] Next, a sufficient amount of aluminum wire (99.99(%)) was immersed in this solution and subjected to substitution purification at room temperature for one week to obtain the base ionic liquid with a composition of 50(mol%) AlCl3-50(mol%) EMIC.

[0092] Next, 40 mL of the obtained ionic liquid was measured and poured into a tall beaker, and hydrazine was added as a reducing agent in an amount of 0.03 moles per 1 L of the ionic liquid to obtain solution 1 for electroless aluminum deposition.

[0093] In addition, the W-coated silicon substrate was degreased and pickled, and then a palladium catalyst was attached using a commercially available catalyst application solution.The substrate was then washed with water and dried with cold air to prepare a substrate for electroless aluminum deposition.

[0094] The prepared substrate was then immersed in electroless aluminum deposition solution 1 and left at room temperature for 10 minutes, after which the substrate was removed and washed in an acetonitrile solution to wash away the electroless aluminum deposition solution 1 adhering to the surface, thereby obtaining the plated substrate of Example 1.

[0095] [Example 2] In a glove box with a dry argon atmosphere, anhydrous aluminum chloride and EMIC were weighed out to a molar ratio of 50:50, and dissolved by stirring at around 50°C while being careful not to raise the temperature.

[0096] Next, a sufficient amount of aluminum wire (99.99(%)) was immersed in this solution and subjected to substitution purification at room temperature for one week to obtain the base ionic liquid with a composition of 50(mol%) AlCl3-50(mol%) EMIC.

[0097] Next, 40 mL of the obtained ionic liquid was measured out into a tall beaker, and hydrazine, which had been dissolved in toluene in advance, was added as a reducing agent in an amount of 0.03 moles per 1 L of the ionic liquid to obtain solution 2 for electroless aluminum deposition.

[0098] In the above, when hydrazine was dissolved in toluene in advance, the hydrazine was dissolved in toluene so that the concentration was 1 (mol / L).

[0099] In addition, the W-coated silicon substrate was degreased and pickled, and then a palladium catalyst was attached using a commercially available catalyst application solution.The substrate was then washed with water and dried with cold air to prepare a substrate for electroless aluminum deposition.

[0100] The prepared substrate was then immersed in electroless aluminum deposition solution 2 and left at room temperature for 10 minutes, after which the substrate was removed and washed in an acetonitrile solution to wash away the electroless aluminum deposition solution 2 adhering to the surface, thereby obtaining the plated substrate of Example 2.

[0101] [Example 3] A plated substrate of Example 3 was obtained by the same procedure as in Example 1 above, except that the composition of the base ionic liquid in Example 1 was changed to 55 (mol %) AlCl3-45 (mol %) EMIC.

[0102] [Example 4] The plating-treated substrate of Example 4 was obtained by the same procedure as in Example 2, except that the composition of the base ionic liquid of Example 2 was changed to 55 (mol %) AlCl3-45 (mol %) EMIC.

[0103] [Example 5] The same procedure as in Example 1 was carried out, except that the base reducing agent in Example 1 was changed to phenylhydrazine, to obtain a plated substrate of Example 5.

[0104] [Comparative Example 1] The same procedure as in Example 3 was carried out, except that the base reducing agent in Example 1 was changed to diisobutylaluminum hydride (DIBAH) and its concentration was changed to 0.2 (mol) per 1 L of ionic liquid, to obtain a plated substrate for Comparative Example 1.

[0105] Next, the plated substrates of Examples 1 to 5 and Comparative Example 1 obtained above were evaluated visually and by X-ray diffraction measurement to evaluate the state of the aluminum film formed on the surface. The aluminum film formation conditions and evaluation results are shown in Table 1.

[0106] [Table 1]

[0107] A comparison between Examples 1 to 5, in which hydrazine or the like was used as the reducing agent, and Comparative Example 1, in which DIBAH was used as the reducing agent, shows that an aluminum film can be formed efficiently by using hydrazine or the like as the reducing agent.

[0108] Under the plating conditions of Comparative Example 1, the prepared substrate was immersed in the electroless aluminum deposition solution and left at room temperature for 3 hours before deposits were finally observed.

[0109] Furthermore, by comparing Examples 2 and 4, in which the reducing agent was dissolved in an organic solvent before being added to the ionic liquid, with Examples 1 and 3, in which the reducing agent was added directly to the ionic liquid, it can be seen that dissolving the reducing agent in an organic solvent beforehand enables the aluminum film to be formed more efficiently.

[0110] In addition, by comparing Examples 1 and 2 with Examples 3 and 4, which have different ionic liquid compositions, it was found that AlCl4 - It can be seen that under conditions where is dominant, the aluminum film can be formed more efficiently.

[0111] In addition, experiments were also conducted in the same manner as in the above examples and comparative examples, except that the base substrate was replaced with a TiN-coated silicon substrate, and the results were similar to those shown in Table 1 above.

[0112] The plating solution M according to the embodiment contains an ionic liquid L1 containing an aluminum halide and a reducing agent containing at least one of hydrazine and a hydrazine derivative. The aluminum halide content in the ionic liquid is 30 (mol%) to 60 (mol%). This allows an aluminum film to be efficiently formed on the substrate W.

[0113] Furthermore, in the plating solution M according to this embodiment, the content of aluminum halide in the ionic liquid L1 is 30 (mol %) to 50 (mol %), which allows the aluminum film to be formed on the substrate W more efficiently.

[0114] The plating solution M according to the embodiment contains an ionic liquid L1 containing an aluminum halide and a reducing agent containing at least one of hydrazine and a hydrazine derivative. - (X is a halogen atom) is Al2X7 - This allows the aluminum film to be formed on the substrate W efficiently.

[0115] In the plating solution M according to this embodiment, the ionic liquid L1 contains a 1,3-dialkylimidazolium halide (wherein the alkyl group has 1 to 12 carbon atoms), which allows an aluminum film to be formed on the substrate W efficiently.

[0116] In the plating solution M according to the embodiment, the content of 1,3-dialkylimidazolium halide in the ionic liquid L1 is 40 (mol %) to 70 (mol %) (however, the sum with the aluminum halide does not exceed 100 (mol %)). This allows an aluminum film to be formed efficiently on the substrate W.

[0117] In the plating solution M according to the embodiment, the hydrazine derivative is at least one selected from methylhydrazine, dimethylhydrazine, phenylhydrazine, and benzophenone hydrazone.

[0118] The plating method according to the embodiment also includes a step of generating a plating solution M (step S3) and a step of forming an aluminum film (step S7). The step of generating the plating solution M (step S3) involves mixing an ionic liquid L1 containing an aluminum halide with a reducing agent containing at least one of hydrazine and a hydrazine derivative to generate the plating solution M. The step of forming the aluminum film (step S7) involves plating a semiconductor substrate (substrate W) with the generated plating solution M to form an aluminum film on the semiconductor substrate (substrate W). This allows the aluminum film to be formed efficiently on the substrate W.

[0119] Furthermore, in the plating method according to the embodiment, the step of forming the aluminum film (step S7) is performed without applying a voltage to the semiconductor substrate (substrate W). This allows an aluminum film with little variation in film thickness to be formed even on a substrate W having vias, trenches, etc. formed on its surface.

[0120] Moreover, the plating method according to the embodiment further includes a step (step S1) of dissolving a reducing agent in an organic solvent before the step (step S3) of producing the plating solution M. This allows the aluminum film to be formed on the substrate W more efficiently.

[0121] In the plating method according to the embodiment, the content of aluminum halide in the ionic liquid L1 is 30 (mol %) to 60 (mol %), which allows an aluminum film to be formed on the substrate W efficiently.

[0122] In the plating method according to the embodiment, the content of aluminum halide in the ionic liquid L1 is 30 (mol %) to 50 (mol %), which allows the aluminum film to be formed on the substrate W more efficiently.

[0123] In the plating method according to the embodiment, the ionic liquid L1 contains AlX4 - (X is a halogen atom) is Al2X7 -This allows an aluminum film to be formed on the substrate W efficiently.

[0124] In the plating method according to the embodiment, the ionic liquid contains a 1,3-dialkylimidazolium halide (wherein the alkyl group has 1 to 12 carbon atoms), which allows an aluminum film to be formed on the substrate W efficiently.

[0125] In the plating method according to the embodiment, the content of the 1,3-dialkylimidazolium halide in the ionic liquid L1 is 40 (mol %) to 70 (mol %) (however, the sum with the aluminum halide does not exceed 100 (mol %)), which allows an aluminum film to be efficiently formed on the substrate W.

[0126] In the plating method according to the embodiment, the hydrazine derivative is at least one selected from methylhydrazine, dimethylhydrazine, phenylhydrazine, and benzophenone hydrazone.

[0127] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the present disclosure. For example, in the above embodiments, an example in which plating processing is performed in a single-wafer processing unit that processes substrates W one by one is shown, but the present disclosure is not limited to such an example.

[0128] For example, the plating process according to this embodiment may be performed in a batch processing unit that simultaneously processes a plurality of substrates W. This also makes it possible to efficiently form an aluminum film on the substrates W.

[0129] Furthermore, in the above embodiment, an example has been shown in which the substrate W is subjected to electroless plating using the plating solution M, but the substrate W may also be subjected to electrolytic plating using the plating solution M. This also makes it possible to efficiently form an aluminum film on the substrate W.

[0130] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0131] 5. Plating department 30 Board holding part 91 Control Unit L1 ionic liquid L2 Diluted Reducing Agent W substrate

Claims

1. an ionic liquid containing an aluminum halide; a reducing agent comprising a hydrazine derivative; Including, the content of the aluminum halide in the ionic liquid is 30 (mol%) to 60 (mol%); The ionic liquid contains a 1,3-dialkylimidazolium halide (wherein the alkyl group has 1 to 12 carbon atoms). Plating solution.

2. The content of the aluminum halide in the ionic liquid is 30 (mol%) to 50 (mol%). The plating solution according to claim 1.

3. an ionic liquid containing an aluminum halide; a reducing agent comprising a hydrazine derivative; Including, The ionic liquid may contain AlX ４ － (X is a halogen atom) is Al ２ X ７ － It contains more than The ionic liquid contains a 1,3-dialkylimidazolium halide (wherein the alkyl group has 1 to 12 carbon atoms). Plating solution.

4. The content of the 1,3-dialkylimidazolium halide in the ionic liquid is 40 (mol%) to 70 (mol%) (however, the sum with the aluminum halide does not exceed 100 (mol%)). The plating solution according to any one of claims 1 to 3.

5. The hydrazine derivative is at least one selected from methylhydrazine, dimethylhydrazine, phenylhydrazine, and benzophenone hydrazone. The plating solution according to any one of claims 1 to 4.

6. A step of mixing an ionic liquid containing an aluminum halide and a reducing agent containing a hydrazine derivative to generate a plating solution; a step of plating a semiconductor substrate with the produced plating solution to form an aluminum film on the semiconductor substrate; Including, the content of the aluminum halide in the ionic liquid is 30 (mol%) to 60 (mol%); The ionic liquid contains a 1,3-dialkylimidazolium halide (wherein the alkyl group has 1 to 12 carbon atoms). Plating method.

7. The step of forming the aluminum film is performed in a state where no voltage is applied to the semiconductor substrate. The plating method according to claim 6.

8. a step of dissolving the reducing agent in an organic solvent before the step of forming the plating solution; The plating method according to claim 6 or 7, further comprising:

9. The content of the aluminum halide in the ionic liquid is 30 (mol%) to 50 (mol%). The plating method according to any one of claims 6 to 8.

10. A plating solution comprising: a step of mixing an ionic liquid containing an aluminum halide and a reducing agent containing a hydrazine derivative to produce a plating solution; a step of plating a semiconductor substrate with the produced plating solution to form an aluminum film on the semiconductor substrate; Including, The ionic liquid may contain AlX ４ － (X is a halogen atom) is Al ２ X ７ － It contains more than The ionic liquid contains a 1,3-dialkylimidazolium halide (wherein the alkyl group has 1 to 12 carbon atoms). Plating method.

11. The content of the 1,3-dialkylimidazolium halide in the ionic liquid is 40 (mol%) to 70 (mol%) (however, the sum with the aluminum halide does not exceed 100 (mol%)). The plating method according to any one of claims 6 to 10.

12. The hydrazine derivative is at least one selected from methylhydrazine, dimethylhydrazine, phenylhydrazine, and benzophenone hydrazone. The plating method according to any one of claims 6 to 11.

Images