Substrate processing method and substrate processing apparatus

Abstract

It efficiently removes metal films. [Solution] A substrate processing method for a substrate having a recess, wherein at least a portion of the side surface or bottom surface of the recess has a region where metal is exposed, comprising: a first step of oxidizing the exposed metal with a first processing solution; and a second step of etching the oxidized metal with a second processing solution after the first step, It is equipped with.

Description

Technical Field

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus.

Background Art

[0002] Conventionally, in a laminated structure in which an insulating film and a metal film such as TiN that is difficult to remove by wet etching are alternately laminated, a method of selectively removing a part of the metal film is known. This method involves heating the substrate in an atmospheric atmosphere to oxidize a part of the metal film such as TiN to make it easier to be wet-etched, and then performing wet etching with a chemical solution capable of removing the oxide film (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of efficiently removing a metal film.

Means for Solving the Problems

[0005] According to one embodiment of the present disclosure, a substrate processing method for processing a substrate having a concave portion and having a region where metal is exposed on at least a part of a side surface or a bottom surface of the concave portion, a first step including oxidizing the exposed metal with a first processing solution, a second step including etching the oxidized metal with a second processing solution after the first step, A substrate processing method including these is provided.

Effects of the Invention

[0006] According to one embodiment of the present disclosure described above, the metal film can be removed efficiently. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic plan view showing the overall configuration of a substrate processing system, which is one embodiment of a substrate processing apparatus. [Figure 2] Figure 2 is a schematic longitudinal cross-sectional view showing an example configuration of a processing unit incorporated into the substrate processing system shown in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view showing one example of a laminated substrate structure that can be processed by a substrate processing method according to one embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing the state during the etching of TiN contained in the laminated structure shown in Figure 3 by a substrate processing method according to one embodiment. [Figure 5] Figure 5 is a flowchart showing a series of steps performed in a substrate processing method according to one embodiment. [Figure 6] Figure 6 is a schematic cross-sectional view showing the configuration of a sample used in an experiment conducted to confirm the effectiveness of a substrate processing method according to one embodiment. [Figure 7] Figure 7 is a graph showing the results of the experiment described above. [Modes for carrying out the invention]

[0008] The following describes in detail, with reference to the drawings, embodiments for implementing the substrate processing apparatus (substrate processing system) and the substrate processing method performed using the same according to this disclosure. However, this disclosure is not limited by these embodiments.

[0009] <Overall configuration of the substrate processing system> First, the overall schematic configuration of a substrate processing system 1 according to an embodiment of a substrate processing apparatus will be described with reference to FIG. 1. FIG. 1 is a diagram showing the schematic configuration of the substrate processing system 1 according to the first embodiment. Hereinafter, in order to clarify the positional relationship, X-axis, Y-axis, and Z-axis orthogonal to each other are defined, and the positive direction of the Z-axis is the vertically upward direction.

[0010] As shown in FIG. 1, a substrate processing system 1 (an example of a substrate processing apparatus) includes a loading / unloading station 2 and a processing station 3.

[0011] The loading / unloading station 2 includes a carrier placement unit 11 and a transfer unit 12. A plurality of carriers C (for example, FOUP) are placed on the carrier placement unit 11. Each carrier C houses a plurality of substrates W (in this embodiment, for example, semiconductor wafers) in a horizontal posture at equal intervals in the vertical direction.

[0012] Inside the transfer unit 12, a substrate transfer apparatus 13 and a delivery unit 14 are provided. The substrate transfer apparatus 13 is composed of a multi-axis transfer robot or an articulated transfer robot. The substrate transfer apparatus 13 holds the wafer by a fork-shaped wafer holder as an end effector and transfers the substrate W between the carrier C and the delivery unit 14.

[0013] The processing station 3 includes a transfer unit 15 and a plurality of processing units 16.

[0014] Inside the transfer unit 15, a substrate transfer apparatus 17 is provided. The substrate transfer apparatus 17 is composed of a multi-axis transfer robot or an articulated transfer robot. The substrate transfer apparatus 17 holds the wafer by a fork-shaped wafer holder as an end effector and transfers the substrate W between the carrier C and the delivery unit 14.

[0015] The processing unit 16 performs liquid processing by supplying a processing fluid to the substrate W carried in by the substrate transfer apparatus 17.

[0016] The substrate W accommodated in the carrier C is taken out by the substrate transfer device 13 of the transfer unit 12 and carried into the delivery unit 14. This substrate W is taken out by the substrate transfer device 17 of the transfer unit 15 and carried into the processing unit 16. The wafer processed by the processing unit 16 is returned to the original carrier C along the reverse route of the above.

[0017] The substrate processing system 1 includes a control device 4 (shown only in FIG. 1). The control device 4 can control the operations of all operable components included in the substrate processing system 1. The control device 4 is, for example, a computer and includes a control arithmetic unit 18 and a storage unit 19. In the storage unit 19, programs for controlling various processes executed in the substrate processing system 1 (including process recipes that define the sequence of processes) are stored. The control arithmetic unit 18 controls the operation of the substrate processing system 1 by reading and executing the programs stored in the storage unit 19. The control arithmetic unit 18 may be a CPU (Central Processing Unit) or one or more circuits.

[0018] Note that the above programs may be recorded on a computer-readable storage medium and installed from the storage medium into the storage unit 19 of the control device 4. Examples of computer-readable storage media include any one of a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magneto-optical disk (MO), a memory card, a RAM (Random Access Memory), a ROM (Read Only Memory), and a SSD (Solid State Drive), or a combination of two or more of them.

[0019] <Configuration of the processing unit> Next, the configuration of the processing unit 16 will be described with reference to FIG. 2.

[0020] The processing unit 16 has the necessary configuration to perform a series of liquid treatments required for etching the TiN film onto the substrate W, which will be described in detail later.

[0021] The processing unit 16 includes a chamber 41 and a substrate holding section 42 provided inside the chamber 41.

[0022] The substrate holding section 42 includes a rotating shaft 421 extending vertically within the chamber 41, a turntable 422 attached to the upper end of the rotating shaft 421, a chuck 423 provided on the outer periphery of the upper surface of the turntable 422 to support the outer edge of the substrate W, and a drive section 424 that rotates the rotating shaft 421.

[0023] The substrate W is supported by the chuck 423 and held horizontally on the turntable 422, slightly separated from the upper surface of the turntable 422. In this embodiment, the substrate W is held by the substrate holding section 42 in a manner that is a so-called mechanical chuck type, in which the outer edge of the substrate W is gripped by the movable chuck 423. However, it may also be a so-called vacuum chuck type, in which the back surface of the substrate W is vacuum-suctioned.

[0024] The base end of the rotating shaft 421 is rotatably supported by the drive unit 424, and the tip of the rotating shaft 421 horizontally supports the turntable 422. When the rotating shaft 421 rotates, the turntable 422 attached to the upper end of the rotating shaft 421 rotates, and as a result the substrate W held on the turntable 422 while supported by the chuck 423 rotates. The control unit 3 controls the operation of the drive unit 424 and controls the rotation timing, rotation speed, etc. of the substrate W.

[0025] The processing unit 16 includes a dilute hydrofluoric acid supply unit 43a, a concentrated nitric acid supply unit 43b, a hydrochloric acid supply unit 43c, and a rinse solution supply unit 43d. The dilute hydrofluoric acid supply unit 43a, the concentrated nitric acid supply unit 43b, the hydrochloric acid supply unit 43c, and the rinse solution supply unit 43d are collectively referred to as the processing solution supply unit.

[0026] The dilute hydrofluoric acid supply unit 43a includes a nozzle 431a that discharges dilute hydrofluoric acid (also referred to as "DHF" for simplicity) to a substrate W held by the substrate holding unit 42, and a dilute hydrofluoric acid supply source 432a that supplies dilute hydrofluoric acid to the nozzle 431a. The dilute hydrofluoric acid supply source 432a may be a tank or one provided as a factory supply. Dilute hydrofluoric acid is supplied to the nozzle 431a from the dilute hydrofluoric acid supply source 432a at a controlled flow rate through a supply pipeline 434a equipped with flow control equipment 433a (on-off valve, flow control valve, flow meter, etc.).

[0027] The concentrated nitric acid supply unit 43b includes a nozzle 431b that discharges concentrated nitric acid (also referred to as "HNO3" for simplicity) to the substrate W held in the substrate holding unit 42, and a concentrated nitric acid supply source 432b that supplies concentrated nitric acid to the nozzle 431b. The concentrated nitric acid supply source 432b may be a tank or one provided as a factory supply. Concentrated nitric acid is supplied to the nozzle 431b from the concentrated nitric acid supply source 432b at a controlled flow rate through a supply pipeline 434b equipped with flow control equipment 433b (on-off valve, flow control valve, flow meter, etc.). In this embodiment, as the concentrated nitric acid, for example, nitric acid with a concentration of about 60-70 wt% (a higher concentration may also be used) can be used.

[0028] The hydrochloric acid supply unit 43c includes a nozzle 431c that discharges hydrochloric acid (also referred to as "HCl" for simplicity) to the substrate W held in the substrate holding unit 42, and a hydrochloric acid supply source 432c that supplies hydrochloric acid to the nozzle 431c. The hydrochloric acid supply source 432c may be a tank or one provided as a factory supply. Hydrochloric acid is supplied to the nozzle 431c from the hydrochloric acid supply source 432c at a controlled flow rate through a supply pipeline 434c equipped with flow control equipment 433c (on-off valve, flow control valve, flow meter, etc.). In this embodiment, for example, dilute hydrochloric acid (hydrochloric acid diluted with water (DHCl)) with a concentration of about 5 to 10 wt% is used as the hydrochloric acid.

[0029] The rinse liquid supply unit 43d includes a nozzle 431d that discharges pure water (DIW) as a rinse liquid to the substrate W held in the substrate holding unit 42, and a rinse liquid supply source 432d that supplies the rinse liquid to the nozzle 431d. The rinse liquid supply source 432d is usually provided as a factory power source. Rinse liquid is supplied to the nozzle 431d from the rinse liquid supply source 432d at a controlled flow rate through a supply pipeline 434d equipped with flow control equipment 433d (on-off valve, flow control valve, flow meter, etc.).

[0030] Two or more processing solutions (for example, dilute hydrofluoric acid and rinsing solution) may be supplied to the substrate W selectively from the same single nozzle.

[0031] The processing unit 16 may also include an organic solvent supply unit having a nozzle for discharging a drying organic solvent such as isopropyl alcohol (IPA) onto the substrate W held in the substrate holding unit 42, and an organic solvent supply source for supplying the drying organic solvent to the nozzle. Alternatively, the processing unit 16 may also include a drying gas supply unit having a nozzle for discharging a drying gas such as nitrogen gas or dry air onto the substrate W held in the substrate holding unit 42, and a drying gas supply source for supplying the drying gas to the nozzle.

[0032] The processing unit 16 includes a nozzle moving mechanism 44 for driving nozzles 431a to 431d. The nozzle moving mechanism 44 has an arm 441, a movable body 442 with a built-in drive mechanism that can move along the arm 441, and a swivel and lifting mechanism 443 for swiveling and raising / lowering the arm 441. The nozzles 431a to 431d are attached to the movable body 442. The nozzle moving mechanism 44 can move the nozzles 431a to 431d between a position above the center of the substrate W held by the substrate holding part 42 and a position above the periphery of the substrate W, and further, can move them to a standby position outside the cup 45, which will be described later in a plan view. In this embodiment, the nozzles 431a to 431d are held by a common arm, but they may each be held by separate arms and be able to move independently.

[0033] The processing unit 16 is equipped with a cup (liquid receiving cup) 45. The cup 45 is provided around the substrate holding section 42 and receives and collects various processing liquids (e.g., cleaning liquid, rinsing liquid, etc.) scattered from the substrate W. The cup 45 is provided with a lifting mechanism (not shown) for driving the cup 45 vertically, an exhaust port 46 for exhausting the atmosphere inside the cup 45, and a drain port 47 for discharging the various processing liquids scattered from the substrate W from the cup 45. The cup 45 has a configuration that allows the exhaust destination and drain destination to be changed depending on the type of liquid (acid, alkali, organic). Since such a configuration is well known in the field of semiconductor manufacturing equipment, illustration and detailed explanation are omitted.

[0034] Next, an example of the processing of the substrate W performed within the processing unit 16 will be described.

[0035] A substrate processing method according to one embodiment of this disclosure can be used, for example, in an etching step to etch a TiN layer horizontally during a series of steps for GAA-FET formation. A schematic representation of the structure of the substrate W immediately before the start of the etching step is shown in Figure 3.

[0036] The substrate W to be etched has two regions. The first region 101 corresponds to the region where PMOS is formed. In this first region 101, multiple silicon nanosheets (Si-NS), each covered by a hafnium oxide layer (HfOx), are spaced apart in the vertical direction. These silicon nanosheets are surrounded by TiN formed, for example, by the ALD method. The second region 102 corresponds to the region where NMOS is formed. Just before reaching the state shown in Figure 3, the structure of the second region 102 is generally identical to the structure of the first region 101.

[0037] Immediately before reaching the state shown in Figure 3, the substrate W is subjected to dry etching with an etch mask applied to the first region 101 and without an etch mask applied to the second region 102. As a result, most of the TiN in the second region 102 is removed, except for the portion between the silicon nanosheets. Consequently, the substrate W has a recess 104 between the first region 101 and the second region 102. At least a portion of the TiN in the second region 102 is exposed on the side (side wall) of the recess 104.

[0038] One embodiment of a substrate processing method according to one embodiment of the present disclosure is intended to completely remove TiN in the narrow gaps between silicon nanosheets in a second region, while etching TiN in a first region without exposing the silicon nanosheets, starting from the state shown in Figure 3. To achieve this, it is necessary to bring the etching rate of TiN along the narrow gaps (see arrow 106 in Figure 4) as close as possible to the etching rate of the surface facing a relatively wider space (see arrow 108 in Figure 4). Figure 4 shows a state where the etching of TiN, which will be described below, has progressed partway.

[0039] Based on the above, the following describes the series of steps for etching TiN.

[0040] <Processing conditions common to the series of steps> The substrate W to be processed is brought into the processing unit 16 and held by the substrate holding unit 42. Next, the substrate W (a silicon substrate on which the GAA FET is formed) is rotated. The rotation of the substrate W continues until the series of processes is completed. Unless otherwise specified, the processing liquid (dilute hydrofluoric acid, concentrated nitric acid, hydrochloric acid, DIW, etc.) is discharged from the corresponding nozzle toward the surface of the substrate W so that the entire surface of the substrate is covered with the processing liquid, and the liquid lands on the center of the rotating substrate (the center of rotation or a position slightly offset from the center of rotation).

[0041] <Pre-treatment process> Dilute hydrofluoric acid is supplied to the surface of a rotating substrate W to remove the native oxide film adhering to the substrate W's surface. This makes the surface of the substrate W hydrophilic, allowing for smoother subsequent processing. Next, the supply of dilute hydrofluoric acid is stopped, and a rinsing solution (in this case, DIW (pure water)) is supplied to the surface of the substrate W to remove the dilute hydrofluoric acid and reaction products from the substrate surface. Then, while the substrate W is still rotating, the supply of the rinsing solution is stopped to remove the DIW from the surface of the substrate W (i.e., the substrate W is completely dried), and then the process immediately proceeds to the next step. (This completes step S1 in the flowchart of Figure 5)

[0042] Furthermore, if hafnium oxide or amorphous silicon that can be etched by dilute hydrofluoric acid is exposed on the surface of the substrate W, the pretreatment step is omitted. Also, if the hydrophilicity of the surface of the substrate W is sufficiently high, the pretreatment step may not be necessary.

[0043] <First step (TiN oxidation step)> Next, concentrated nitric acid is supplied to the surface of the rotating substrate W for a predetermined time. This causes the surface of the TiN exposed to the concentrated nitric acid and its vicinity to oxidize, forming a TiO2 (titanium oxide) film. Next, the supply of concentrated nitric acid is stopped, and a rinsing solution (DIW in this case) is supplied to the surface of the substrate W to remove the concentrated nitric acid and reaction products from the substrate surface. Then, while the substrate W is still rotating, the supply of the rinsing solution is stopped to remove the DIW from the surface of the substrate W (i.e., the substrate W is shaken dry), and then the process immediately proceeds to the next step (S2 in the flowchart of Figure 5).

[0044] <Second step (Oxide etching step)> Next, hydrochloric acid (here, dilute hydrochloric acid (DHCl) is used) is supplied to the surface of the rotating substrate W for a predetermined time. This causes the surface of the TiN exposed to the hydrochloric acid and the surrounding TiO2 portion (the portion oxidized in the first step) to dissolve (etch) due to the hydrochloric acid. Next, the supply of hydrochloric acid is stopped and a rinsing solution (here, DIW) is supplied to the surface of the substrate W to remove the hydrochloric acid and reaction products from the substrate surface. Then, while the substrate W is still rotating, the supply of the rinsing solution is stopped to remove the DIW from the surface of the substrate W (i.e., the substrate W is shaken dry), and then the process immediately proceeds to the next step (S3 in the flowchart of Figure 5).

[0045] The first and second steps are performed at least once each. In this example, as shown in Figure 4, a layer made of the second material (a TiN layer) sandwiched between layers made of the first material (a Si-NS layer surrounded by HfOx) is etched in the transverse direction (a direction perpendicular to the stacking direction). When etching this structure, it is usually difficult to achieve the desired amount of TiN etching by performing the first and second steps only once each. In that case, the first and second steps should be repeated alternately multiple times (for example, several dozen times) until the desired amount of etching is obtained (in this example, until the TiN layer between the layers made of the first material is completely removed) (S2 to S4 in the flowchart of Figure 5).

[0046] The reason for drying the substrate W when transitioning from the first to the second process is that if rinsing solution (DIW) remains on the substrate W, the hydrochloric acid supplied to the substrate W in the second process will be diluted, making it impossible to sufficiently etch the oxidized TiN layer. In particular, after etching has progressed to a certain extent, a relatively long time is required to replace the DIW located deep within the narrow space between two adjacent layers made of the first material (layers made of Si-NS surrounded by HfOx) with hydrochloric acid. For this reason, from the viewpoint of shortening processing time, it is preferable to dry the substrate W when transitioning from the first to the second process.

[0047] The reason for drying the substrate W when transitioning from the Nth second step to the N+1th first step is that if rinsing solution (DIW) remains on the substrate W, the concentrated nitric acid supplied to the substrate W in the N+1th first step will be diluted. If the concentrated nitric acid is diluted, not only will it be impossible to oxidize TiN to the desired state, but there is also a risk of dissolving TiN or etching parts that are not to be etched. Therefore, it is preferable to dry the substrate W when transitioning from the Nth second step to the N+1th first step, not only from the viewpoint of shortening the processing time, but also from the viewpoint of ensuring that TiN is oxidized to the desired state.

[0048] As described above, when transitioning from the first process to the second process (the same applies when transitioning from the pretreatment process to the first first process for the first time), and when transitioning from the Nth second process to the N+1th first process, the substrate only needs to be dry, and the substrate can be dried in any way. For example, after rinsing with a chemical solution (concentrated nitric acid or hydrochloric acid), the rinsing solution may be replaced with an organic drying solvent such as IPA (a liquid that is compatible with water and has a lower surface tension than water), and then shake-drying may be performed. Shake-drying may also be performed while blowing an inert gas such as nitrogen gas or a low-humidity gas onto the substrate.

[0049] Furthermore, if the second step is the final second step for a single substrate W, the series of processes for the substrate W may be completed by performing the final shake-drying of the substrate W in the second step as the final procedure. Alternatively, after supplying the rinsing solution to the substrate W in the second step, and before performing the shake-drying of the substrate W, the rinsing solution on the substrate W may be replaced with a drying organic solvent, such as IPA (isopropyl alcohol), before performing the shake-drying of the substrate.

[0050] When concentrated nitric acid is supplied to the substrate in the first step, and / or when hydrochloric acid is supplied to the substrate in the second step, the rotation speed of the substrate W may be changed, or the substrate W may be oscillated (repeated rotation in the forward and reverse directions).

[0051] <Chemical Reaction in the Embodiment> The chemical reaction occurring in the above embodiment will be described below.

[0052] When concentrated nitric acid is supplied to the TiN layer in the first step, the following reaction occurs, and TiN (titanium nitride) becomes TiO2 (titanium dioxide). TiN + HNO3 → TiNOH + NO2 →→ TiO2 ··· (Reaction 1) When hydrochloric acid is supplied to the TiN layer whose surface has been oxidized to TiO2 in the second step, the following reaction occurs, and TiCl4 (titanium (IV) chloride) is produced. Since titanium (IV) chloride is soluble in hydrochloric acid, Ti that forms TiO2 dissolves into the solution and is removed from the TiN layer. TiO2 + 4HCl → TiCl4 + 2H2O ··· (Reaction 2)

[0053] In Reaction 1, the oxidation reaction that produces TiO2, which is easily dissolved by hydrochloric acid, with TiN as the starting material is completed. Therefore, in Reaction 2, only the dissolution reaction of TiO2 needs to occur. Thus, in order to separately perform different reactions such as oxidation and dissolution in the first step and the second step respectively, the efficiency of each step is improved, and the TiN film can be etched and removed efficiently as a whole.

[0054] Hereinafter, another known method for removing the TiN film will be described.

[0055] <Chemical Reaction in the First Known Method Using SC2> The first known method sequentially performs a step of supplying SC2 to the substrate to wet-etch TiN, a DIW rinse step, and a spin-dry step.

Number

[0055] , , , , , , , , ++ , or Ti(OH)++ is generated, and then Cl - forms a complex with it. As a result, Ti dissolves in the liquid.

[0056] <Chemical reaction in the second known method using H2O2 (hydrogen peroxide solution)> The second known method sequentially performs a process of supplying hydrogen peroxide solution to a substrate to wet-etch TiN, a DIW rinse process, and a spin-drying process.

Number

[0057] The experimental results of comparing the method according to the above embodiment with the above first and second known methods will be described below. A sample having the laminated structure shown in FIG. 6 was prepared. This sample mimics the structure of the GAA·FET described above. On a bare silicon substrate, an a-Si (amorphous silicon) film, a 2-nm-thick HfO2 film, a TiN film (fabricated by an ALD process), a 2-nm-thick HfO2 film, and an a-Si film were sequentially laminated from the bottom, and then a recess reaching the bare silicon substrate was formed in the central portion by dry etching. The thicknesses of the TiN films were 4 nm, 6 nm, 1 nm, and 25 nm. The ends of the TiN films are exposed on the sidewalls of the recess.

[0058] For the sample having this laminated structure, the TiN film was etched using the method according to the above embodiment and the above first and second known methods. In all of the method according to the embodiment and the above first and second known methods, the above-described pretreatment process was performed. In the pretreatment process, a 0.57 wt% dilute hydrofluoric acid at room temperature was supplied to the rotating sample for 5 minutes, then DIW rinsing was performed, and then spin-drying was performed.

[0059] In the method according to the embodiment, the chemical treatment in the first step (meaning the treatment using a reactive chemical solution excluding the rinsing and shake-drying steps of the said step; the same applies hereinafter) was performed by supplying 69 wt% concentrated nitric acid at room temperature to a rotating sample for 2 minutes. The chemical treatment in the second step was performed by supplying 6.9 wt% dilute hydrochloric acid at 40°C to a rotating sample for 2 minutes. The first and second steps were performed alternately 44 times each. In the first and second steps, after the chemical treatment was completed, rinsing and shake-drying were performed thereafter.

[0060] The first step involved supplying SC2 at 50°C (here, a mixture of hydrochloric acid, hydrogen peroxide, and water in a ratio of 1:1:50) to a rotating sample for 7 minutes. The second step involved supplying diluted hydrogen peroxide at 50°C (here, a mixture of hydrogen peroxide and water in a ratio of 1:5) to a rotating sample for 8 minutes.

[0061] For the sake of simplicity, the etching process described above on the sample will also be referred to as "narrow area TiN film etching."

[0062] Furthermore, using the same processing conditions as described above, a substrate on which a flat TiN film was formed was also subjected to etching of the TiN film (which will also be referred to as "flat TiN film etching" for simplicity of description) under the same conditions as the method according to the above embodiment performed on the sample described above, as well as the first and second known methods described above.

[0063] The experimental results are shown in the graph in Figure 7. The horizontal axis represents the thickness of the TiN film in the sample shown in Figure 6. The vertical axis represents the value obtained by dividing the etching amount in narrow-area TiN film etching by the etching amount in flat TiN film etching and multiplying by 100 (%) (hereinafter also referred to as the "narrow-area etching efficiency value"). ◇ indicates the method according to the embodiment, △ indicates the first known method, and ○ indicates the results of the second known method. Naturally, when performing narrow-area TiN film etching, the thinner the TiN film thickness, the deeper the liquid needs to be injected into the narrow space as etching progresses. Therefore, the thinner the TiN film thickness, the more difficult it becomes to advance etching in the lateral direction. Consequently, in all methods, the narrow-area etching efficiency value decreases as the TiN film thickness decreases.

[0064] As is clear from the graph in Figure 7, the method according to the above embodiment showed a higher narrow-area etching efficiency even when the thickness of the TiN film was reduced, compared to the first and second known methods described above.

[0065] In the first step, treatment with concentrated nitric acid causes a TiO2 film to form on and near the surface of the TiN layer. Once the TiO2 film is formed on and near the surface of the TiN layer, the reaction hardly proceeds from there. Therefore, there is little difference in the thickness of the TiO2 film formed on the surface of TiN depending on whether the TiN layer faces a relatively wide space (the recess in the example of Figure 6) or a relatively narrow space (the gap between adjacent a-Si films (sandwiched between HfO2 films) in the vertical direction in the example of Figure 6). In the second step, hydrochloric acid is supplied, causing only the TiO2 film to dissolve, while the underlying TiN layer does not dissolve. Therefore, it is thought that a high narrow-area etching efficiency can be obtained.

[0066] When TiN is etched using the first and second known methods described above, the TiN layer itself dissolves in the solution, and a TiO2 film is not formed. Therefore, the etch rate of the TiN layer facing a relatively wide space, where the chemical solution near the area to be etched is easily replaced with fresh chemical solution, tends to be higher than the etch rate of the TiN layer facing a relatively narrow space. This is thought to be the reason why the etching efficiency value in narrow areas is low.

[0067] Furthermore, if dilute nitric acid is used instead of concentrated nitric acid in the first step, the TiN layer itself will dissolve in the solution, and a TiO2 film will not be formed. In this case as well, the etch rate of the TiN layer facing a relatively wide space where the chemical solution near the etching area is easily replaced with fresh chemical solution tends to be higher than that of the TiN layer facing a relatively narrow space. Also, dilute nitric acid may corrode materials other than TiN. Therefore, it is desirable to use concentrated nitric acid in the first step.

[0068] According to the above embodiment, when etching TiN, it is possible to perform etching efficiently while suppressing the influence of the shape of the film formed by TiN or the environment surrounding the film. According to the above embodiment, it is possible to suppress the reduction in the amount of etching of films in narrow spaces (recesses, lateral depressions) within the pattern. In addition, when a single substrate contains a mixture of TiN films facing relatively wide spaces and TiN films facing relatively narrow spaces, it is possible to suppress the occurrence of the phenomenon in which the amount of etching of the TiN films facing relatively narrow spaces is significantly smaller than the amount of etching of the TiN films facing relatively wide spaces.

[0069] As an example of a combination of a film facing a relatively wide space and a film facing a relatively narrow space, in addition to those mentioned above, a combination of a film formed on the surface of the substrate W and a film formed on the inner surface (bottom or side surface of the recess) of a recess formed on the surface of the substrate W can be considered.

[0070] One possible approach is to perform the oxidation of the TiN film in a bake unit that heats the substrate in an oxidizing atmosphere (e.g., air), and then perform the subsequent etching in a liquid treatment unit. In this case, the total processing time increases, especially due to the transfer of the substrate between units. However, according to the above embodiment, one substrate can be processed by one liquid treatment unit (liquid treatment module), thus reducing the processing time. Furthermore, the equipment cost can also be reduced.

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

[0072] The substrate is not limited to semiconductor wafers, but may be any type of substrate used in the field of semiconductor manufacturing, such as glass substrates or ceramic substrates.

[0073] The film to be etched is not limited to a TiN film provided in a narrow space between multiple silicon films sandwiched or surrounded by an HfOx film, as described above. The film to be etched is not limited to TiN, but may be one or more metals selected from the group consisting of TiN, SiN, W, and Mo. In this specification, "metal" also includes nitrides such as TiN and SiN, which are good conductive materials treated as metals in the field of semiconductor manufacturing. The series of steps according to the above embodiment (first step → second step) is not limited to etching a metal film provided in a narrow space, but may also be used to etch a metal film formed on the surface of a substrate facing a wide space. Films other than the film to be etched surrounding the film to be etched are not limited to multiple silicon films sandwiched or surrounded by an HfOx film. They may be any film made of a material that is not affected by or is negligibly affected by the processing solution used in the first and second steps.

[0074] The processing solution (oxidizing agent) used in the first step is not limited to concentrated nitric acid; any solution that can oxidize the film to be etched without substantially dissolving it, and that does not affect the surrounding film or only negligibly does not affect it, is acceptable. Examples of such solutions include ozonated water, permanganate solution, and periodic acid solution.

Claims

1. A substrate processing method for processing a substrate having a recess, wherein at least a portion of the side surface or bottom surface of the recess has a region where metal is exposed, A first step includes oxidizing the exposed metal with a first processing solution, A second step, which includes etching the oxidized metal with a second processing solution, after the first step, A substrate processing method comprising the following:

2. The substrate processing method according to claim 1, wherein the first step and the second step are performed in the same liquid processing unit.

3. The substrate processing method according to claim 1, wherein the first step and the second step are performed alternately at least twice or more times.

4. The first step includes rinsing the substrate after oxidizing the metal with the first processing solution, and then drying the substrate. The second step includes etching the oxidized metal with a second processing solution, rinsing the substrate, and then drying the substrate. The substrate processing method according to claim 3.

5. The substrate treatment method according to claim 1, wherein the first treatment solution is concentrated nitric acid.

6. The substrate processing method according to claim 1, wherein the first processing solution is ozonated water.

7. The substrate treatment method according to claim 1, wherein the second treatment solution is hydrochloric acid.

8. The substrate processing method according to claim 1, wherein the metal is one of TiN, SiN, W, or Mo.

9. The aforementioned metal is TiN, The first treatment solution is concentrated nitric acid. The substrate treatment method according to claim 1, wherein the second treatment solution is hydrochloric acid.

10. Before performing the first step described above, a pretreatment step is carried out. The substrate processing method according to claim 1, wherein the pretreatment step includes washing the substrate with dilute hydrofluoric acid, rinsing the substrate thereafter, and drying the substrate thereafter.

11. The metal forms at least one of the multiple films that constitute the laminated structure. With respect to the stacking direction of the plurality of films, non-etching target films are provided on both sides of one film, the non-etching target films being made of a material that is not substantially etched by the first and second processing solutions used in the first and second steps, respectively. The substrate processing method according to claim 1, wherein the substrate processing method involves etching one film from the end of the one film exposed in the recess in a direction perpendicular to the stacking direction of the plurality of films.

12. A substrate holding part that holds and rotates the substrate, A processing liquid supply unit is configured to supply a first processing liquid and a second processing liquid to a substrate held by the substrate holding unit, Control at least the substrate holding unit and the processing liquid supply unit, The process of holding and rotating a substrate having a recess, wherein the substrate has a region in which metal is exposed on at least a part of the side surface or bottom surface of the recess, in the substrate holding portion, A first step includes supplying the first processing liquid to the substrate using the processing liquid supply unit to oxidize the exposed metal with the first processing liquid, A second step, which includes supplying the second processing solution to the substrate by the processing solution supply unit after the first step, and etching the oxidized metal with the second processing solution, A control unit that causes a substrate processing method to be executed, A substrate processing apparatus equipped with the following:

13. The substrate processing apparatus according to claim 12, wherein the control unit causes the first step and the second step to be repeated alternately at least two or more times.

14. The first step includes supplying the first processing solution to the substrate to oxidize the metal, then supplying a rinsing solution to the substrate to rinse it, and then rotating the substrate to completely dry it. The second step includes etching the oxidized metal with a second processing solution, then supplying a rinsing solution to the substrate to rinse it, and then rotating the substrate to completely dry it. The substrate processing apparatus according to claim 13.

15. The substrate processing apparatus according to claim 12, wherein the first processing solution is concentrated nitric acid.

16. The substrate processing apparatus according to claim 12, wherein the first processing liquid is ozonated water.

17. The substrate processing apparatus according to claim 12, wherein the second processing solution is hydrochloric acid.

18. The substrate processing apparatus according to claim 12, wherein the metal is one of TiN, SiN, W, or Mo.

19. The aforementioned metal is TiN, The first treatment solution is concentrated nitric acid. The substrate processing apparatus according to claim 12, wherein the second processing solution is hydrochloric acid.

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