Substrate processing method

Abstract

A high etching rate is ensured as a whole, while achieving a uniform distribution of etching amounts across the entire substrate. The substrate processing method includes a first etching step in which an etching liquid is supplied to the surface of the substrate while the substrate is rotated, and a second etching step performed thereafter. The first etching step is performed under the condition that the etching amount of a second area on the peripheral side of the surface of the substrate is greater than the etching amount of a first area on the central side, and the second etching step is performed under the condition that the etching amount of the second area is smaller than the etching amount of the first area. The second etching step is performed under the condition that the temperature of the substrate is higher than the temperature when no temperature regulating liquid is supplied by supplying a temperature regulating liquid to the central portion of the back side of the substrate. The temperature regulating liquid absorbs heat from the substrate while expanding toward the periphery of the substrate, thereby making the temperature of the first area on the surface of the substrate higher than the temperature of the second area.

Description

Technical Field

[0001] The present disclosure relates to a substrate processing method. Background Art

[0002] The manufacture of semiconductor devices includes an etching process that wet-etches a thin film formed on the surface of a substrate such as a semiconductor wafer. Patent Document 1 describes an etching method for etching a thin film having a film thickness distribution in which the film thickness is thicker at the periphery. This etching method includes: a first step in which an etching liquid is supplied to a film formed at the periphery, which is thicker than at the center, while rotating the substrate; and an etching inhibitor liquid is supplied to a position on the substrate closer to the center than the position to which the etching liquid is supplied, thereby etching the film at the periphery; and a second step in which, after the first step, the etching liquid is supplied to the rotating substrate and the film is etched to a predetermined film thickness. This method achieves a uniform film thickness distribution after etching.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2018 / 079494 Pamphlet Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The present disclosure provides a technology capable of achieving uniformity in the distribution of etching amount across the entire substrate while ensuring a high etching rate overall.

[0008] Solutions for solving problems

[0009] One embodiment of a substrate processing method includes: a first etching step of supplying an etching liquid to a surface of the substrate while rotating the substrate, and performing etching under conditions such that an etching amount of an etching target film in a second region located on a peripheral side of the substrate surface is greater than an etching amount of an etching target film in a first region located on a central side of the substrate surface; and a second etching step of supplying the etching liquid to the surface of the substrate while rotating the substrate after the first etching step, and performing etching under conditions such that an etching amount of the etching target film in the second region of the substrate surface is less than an etching amount of the etching target film in the first region of the substrate surface. The first etching step is performed before the second etching step, and the second etching step is performed under conditions such that a temperature of the substrate is raised compared to a temperature in the absence of the temperature regulating liquid by supplying a temperature regulating liquid to a central portion of a rear surface of the substrate. In the second etching step, the temperature regulating liquid absorbs heat from the substrate and spreads toward the periphery of the substrate, thereby raising the temperature of the first region of the substrate surface to a higher temperature than that of the second region.

[0010] Effects of the Invention

[0011] According to the above embodiment, it is possible to achieve uniformity in the etching amount distribution across the entire substrate while ensuring a high etching rate as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The diagram is a cross-sectional view of a substrate processing apparatus according to one embodiment.

[0013] Figure 2 It is a schematic longitudinal sectional view showing the structure of the processing unit.

[0014] Figure 3A This is a diagram used to explain the operation of one step of substrate processing.

[0015] Figure 3B This is a diagram used to explain the operation of one step of substrate processing.

[0016] Figure 3C This is a diagram used to explain the operation of one step of substrate processing.

[0017] Figure 3D This is a diagram used to explain the operation of one step of substrate processing.

[0018] Figure 4 This is a schematic cross-sectional view for explaining the film thickness distribution of the etching target film after the first etching step is completed.

[0019] Figure 5 It is a graph for explaining the distribution of etching amount.

[0020] Figure 6 This is a graph showing the change over time in the temperature distribution of the wafer when the second etching step is performed.

[0021] Figure 7 This is a graph for explaining the relationship between wafer temperature distribution and etching amount distribution. DETAILED DESCRIPTION

[0022] One embodiment of a substrate processing apparatus will be described with reference to the accompanying drawings.

[0023] Figure 1 1 and 2. The diagram schematically illustrates the structure of the substrate processing system according to the present embodiment. To clarify the positional relationship, the X-axis, Y-axis, and Z-axis are defined as being perpendicular to each other, with the positive direction of the Z-axis being the vertically upward direction.

[0024] like Figure 1 As shown, the substrate processing system 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.

[0025] The loading and unloading station 2 includes a carrier placement unit 11 and a conveying unit 12. The carrier placement unit 11 places a plurality of carriers C for horizontally storing a plurality of substrates, in this embodiment, semiconductor wafers (hereinafter referred to as wafers W).

[0026] The transport unit 12 is disposed adjacent to the carrier placement unit 11 and includes a substrate transport device 13 and a delivery unit 14 therein. The substrate transport device 13 includes a wafer holding mechanism for holding a wafer W. The substrate transport device 13 is movable in the horizontal and vertical directions and rotatable about a vertical axis. The substrate transport device 13 uses the wafer holding mechanism to transport the wafer W between the carrier C and the delivery unit 14.

[0027] The processing station 3 is provided adjacent to the conveying device 12. The processing station 3 includes a conveying section 15 and a plurality of processing units 16. The plurality of processing units 16 are provided on both sides of the conveying section 15 in a row.

[0028] The transport unit 15 includes a substrate transport device 17 therein. The substrate transport device 17 includes a wafer holding mechanism for holding the wafer W. The substrate transport device 17 is movable in the horizontal and vertical directions and rotatable about a vertical axis. The substrate transport device 17 uses the wafer holding mechanism to transport the wafer W between the interface 14 and the processing unit 16.

[0029] The processing unit 16 performs predetermined substrate processing on the wafer W transferred by the substrate transfer device 17 .

[0030] The substrate processing system 1 also includes a control device 4. The control device 4 is, for example, a computer and includes a control unit 18 and a storage unit 19. The storage unit 19 stores programs for controlling various processes performed in the substrate processing system 1. The control unit 18 controls the operation of the substrate processing system 1 by reading and executing the programs stored in the storage unit 19.

[0031] Alternatively, the program 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 a hard disk (HD), a floppy disk (FD), a compact disk (CD), a magneto-optical disk (MO), and a memory card.

[0032] In the substrate processing system 1 configured as described above, the substrate transfer device 13 of the loading / unloading station 2 first removes a wafer W from the carrier C placed on the carrier placement portion 11 and places the removed wafer W on the delivery portion 14. The substrate transfer device 17 of the processing station 3 removes the wafer W placed on the delivery portion 14 from the delivery portion 14 and carries the wafer W into the processing unit 16.

[0033] After the wafer W loaded into the processing unit 16 is processed by the processing unit 16, the wafer W is unloaded from the processing unit 16 by the substrate transfer device 17 and placed on the delivery unit 14. The substrate transfer device 13 then returns the processed wafer W placed on the delivery unit 14 to the carrier C of the carrier placement unit 11.

[0034] Next, refer to Figure 2 The structure of the processing unit 16 will be described.

[0035] The processing unit 16 includes a chamber 20 , a substrate holding and rotating mechanism 30 , a first processing fluid supply unit 40 , a second processing fluid supply unit 50 , and a recovery cup 60 .

[0036] The chamber 20 houses the substrate holding and rotating mechanism 30 and the recovery cup 60. A fan filter unit (FFU) 21 is provided on the top of the chamber 20. The FFU 21 is used to form a downward flow in the chamber 20.

[0037] The substrate holding and rotating mechanism 30 includes a substrate holding portion 31, a support column 32, and a rotation drive unit 33. The substrate holding portion 31 is configured as a mechanical chuck having a disk-shaped base 31a and a plurality of gripping claws 31b arranged at intervals along the circumferential edge of the base 31a. The substrate holding portion 31 holds the wafer W horizontally using the gripping claws 31b. When the gripping claws 31b grip the substrate, a gap is formed between the upper surface of the base 31a and the lower surface of the wafer W.

[0038] The support 32 is a hollow member extending in the vertical direction. The upper end of the support 32 is connected to the base 31a. The rotation drive 33 rotates the support 32, thereby rotating the substrate holder 31 and the wafer W held therein about the vertical axis.

[0039] The recovery cup 60 is arranged so as to surround the substrate holding portion 31. The recovery cup 60 captures the processing liquid scattered from the wafer W held in the substrate holding portion 31 for rotation. A drain port 61 is formed at the bottom of the recovery cup 60. The processing liquid captured by the recovery cup 60 is discharged to the outside of the processing unit 16 through the drain port 61. An exhaust port 62 is formed at the bottom of the recovery cup 60. The internal space of the recovery cup 60 is sucked through the exhaust port 62. The gas supplied from the FFU 21 is sucked into the interior of the recovery cup 60 and then discharged to the outside of the processing unit 16 through the exhaust port 62.

[0040] The first processing fluid supply unit 40 is used to supply various processing fluids (liquid, gas, gas-liquid mixed fluid, etc.) to the upper surface of the wafer W held on the substrate holding unit 31 (usually the surface of the wafer W on which the device is formed). The first processing fluid supply unit 40 has one or more surface nozzles 41 for spraying the processing fluid onto the upper surface (first surface) of the wafer W. The number of surface nozzles 41 is set to the number required for the processing performed in the processing unit 16. Figure 2 Although five surface nozzles 41 are depicted in FIG. 5 , the number is not limited to this.

[0041] The first processing fluid supply unit 40 includes one or more (two in the illustrated example) nozzle arms 42. Each nozzle arm 42 carries at least one of the plurality of surface nozzles 41. Each nozzle arm 42 is capable of moving the surface nozzle 41 it carries between a position (processing position) substantially directly above the center of rotation of the wafer W and a retreat position further outward from the upper opening of the recovery cup 60.

[0042] To each surface nozzle 41 in the surface nozzle 41, a treatment fluid is supplied from the corresponding treatment fluid supply mechanism 43. The treatment fluid supply mechanism 43 can include a treatment fluid supply source such as a tank, a bomb, or a factory supply energy source, a supply pipeline for supplying the treatment fluid (treatment liquid or treatment gas) from the treatment fluid supply source to the surface nozzle 41, and a flow regulating device such as an on-off valve and a flow control valve arranged on the supply pipeline. The supply pipeline can be connected to a discharge pipeline to discharge the treatment fluid (especially the treatment liquid) retained in the supply pipeline of the surface nozzle 41 and its vicinity. Such a treatment fluid supply mechanism 43 is widely known in the technical field of semiconductor manufacturing equipment, so the illustration and detailed description of the structure are omitted. A liquid receiving portion (not shown) is provided in the processing unit 16 so that a dummy-dispense can be performed when each surface nozzle 41 is in a retreat position.

[0043] The second processing fluid supply unit 50 is used to supply various processing fluids (processing liquid, processing gas, etc.) to the lower surface of the wafer W held on the substrate holding unit 31 (usually the back surface of the wafer W where no device is formed). The second processing fluid supply unit 50 has one or more (two in the example shown) back surface nozzles 51 for spraying the processing fluid to the lower surface (second surface) of the wafer W. Figure 2 As schematically shown in FIG, a processing liquid supply pipe 52 extends vertically within the hollow support portion 32. The upper end openings of the two flow paths extending vertically within the processing liquid supply pipe 52 each function as a back nozzle 51. The processing liquid supply pipe 52 is disposed within the support portion 32 so as to maintain a non-rotating state even when the substrate holding portion 31 and the support portion 32 rotate.

[0044] The treatment fluid is supplied from the corresponding treatment fluid supply mechanism 53 to each of the back nozzles 51. The treatment fluid supply mechanism 53 has the same structure as the treatment fluid supply mechanism 43 for the front nozzles 41 described above.

[0045] Next, the various steps of liquid treatment performed on a single wafer W using the processing unit 16 will be described. Here, it is assumed that the film to be etched formed on the surface of the wafer W is an oxide film (a thermal oxide film or TEOS). Furthermore, when performing each of the liquid treatment steps described below, one or more surface nozzles 41 are used: a two-fluid nozzle (hereinafter referred to as "two-fluid nozzle 41A") for ejecting a mixed fluid of DHF (dilute hydrofluoric acid) and N2 gas (nitrogen gas) as an etching solution, and two DIW nozzles (hereinafter referred to as "DIW nozzle 41B" and "DIW nozzle 41C").

[0046] In addition, when implementing each step of the liquid treatment described below, a first nozzle arm (hereinafter referred to as "first nozzle arm 42A") and a second nozzle arm (hereinafter referred to as "second nozzle arm 42B") are used as one or more nozzle arms 42.

[0047] In addition, when implementing each of the liquid treatment processes described below, as one or more back nozzles 51, a back liquid nozzle (hereinafter referred to as "back liquid nozzle 51A") for selectively ejecting one of DHF and DIW, and a back gas nozzle (hereinafter referred to as "back gas nozzle 51B") for ejecting N2 gas are used.

[0048] Furthermore, the two-fluid nozzle 41A is configured to atomize the process liquid (e.g., DHF, an etching solution) by merging a flow of gas (e.g., N₂ gas) within the nozzle, thereby ejecting a two-fluid mixture consisting of process liquid droplets and gas. When no gas is supplied to the two-fluid nozzle 41A, the two-fluid nozzle 41A functions as a conventional nozzle that simply ejects the process liquid in the form of a liquid column. Such two-fluid nozzles are well known in the art, and a detailed description of their structure is omitted.

[0049] <Prewetting process>

[0050] While the wafer W is being rotated at a high speed (e.g., about 1000 rpm), the DIW nozzle 41B is positioned above the center of the wafer W, and DIW (pure water) at room temperature (e.g., about 25°C) is sprayed so that the DIW lands on the center of the surface of the wafer W. In addition, in the case of spraying liquid, "spraying so that the DIW lands on the center" means that at least the rotation center of the surface of the wafer W is wetted by the sprayed liquid. In addition, DIW at room temperature (e.g., about 25°C) is sprayed from the back liquid nozzle 51A toward the center of the back of the wafer W. The DIW supplied to the center of the surface and back of the wafer W spreads over the entire area of ​​the surface and back due to centrifugal force, so that the entire area of ​​the surface and back is covered with a liquid film of DIW. Thereafter, the rotation speed of the wafer W is reduced to a low speed (e.g., about 200 rpm). Thereafter, the spraying of DIW from the DIW nozzle 41B and the back liquid nozzle 51A is stopped.

[0051] The DIW nozzle 41B supported by the first nozzle arm 42A retreats from above the center of the wafer W and is positioned above the periphery of the wafer W. The DIW nozzle 41C supported by the second nozzle arm 42B is positioned above the center of the wafer W.

[0052] From the moment the wafer rotation speed is temporarily reduced until the second etching step, described later, is completed, the rotation speed of wafer W is maintained at a low speed of less than 300 rpm, for example, approximately 200 rpm. The rotation speed of wafer W remains constant until the second etching step is completed, but may vary slightly. By suppressing the rotation speed of wafer W to a low level, even when the amount of liquid supplied to the surface of wafer W is low (e.g., the liquid discharge rate from the two-fluid nozzle is approximately 0.1 L / min), the formation of dry areas on the surface of wafer W can be prevented.

[0053] <First Etching Step>

[0054] Next, DIW at room temperature (e.g., about 23°C) is ejected from the DIW nozzle 41C toward the center of the surface of the wafer W. Thus, the DIW liquid film formed on the entire surface of the wafer W is reliably maintained. The ejection of DIW stops in a short time (e.g., less than 1 second). Figure 3A 3 shows the state immediately after the discharge of DIW is stopped. Thereafter, the DIW nozzle 41C is retracted from above the wafer W.

[0055] The liquid film of DIW has the effect of a protective film, which is used to prevent the mist of DHF ejected from the two-fluid nozzle 41A from adhering to the first area described later and causing unintended etching in the first area, or generating particles in the first area. The first area refers to the circular area on the surface of the wafer W described later that is closer to the inner side than the radial position R3. Thus, it is also possible to continue to eject a small amount of DIW from the DIW nozzle 41C when ejecting two fluids from the two-fluid nozzle 41A to the peripheral portion of the wafer W. However, when ejecting two fluids from the two-fluid nozzle 41A to the peripheral portion of the wafer W, if there is a thick liquid film of DIW in the second area described later (the annular area closer to the outer side than the radial position R3), the etching effect of the two fluids will be damaged. Therefore, it is necessary to ensure that the first area is continuously covered by the liquid film. Even in the case of continuously ejecting DIW from the DIW nozzle 41C, it is preferred that the ejection flow rate is less. Furthermore, if the DIW film supplied in the previous pre-wetting step is sufficiently maintained in the first region when the two-fluid nozzle 41A discharges the two-fluid toward the second region of the wafer W, discharge of DIW from the DIW nozzle 41C may be omitted.

[0056] Next, DHF is ejected from the dual-fluid nozzle 41A supported by the first nozzle arm 42A toward the peripheral portion of the wafer W, specifically, toward a radial position slightly inward of the peripheral edge (edge) of the wafer W (hereinafter, this radial position is referred to as "radial position R1"). Afterwards, N2 gas is supplied to the dual-fluid nozzle 41A in addition to DHF, thereby ejecting a mixed fluid of DHF mist and N2 gas, i.e., a dual-fluid, toward the radial position R1. Figure 3B] shows the state immediately after the two-fluid is ejected. Furthermore, since the two-fluid nozzle 41A ejects the two-fluid in a conical shape, i.e., with a certain width, the two-fluid may collide with the edge of the wafer W. The flow rate of DHF supplied to the two-fluid nozzle 41A can be set to 0.1 L / min, for example, but is not limited thereto.

[0057] In addition, at approximately the same time as the supply of N2 gas to the dual-fluid nozzle 41A is started (it can also be slightly earlier or later), a temperature regulating liquid of a first temperature (for example, around 25°C) is started to be ejected from the back liquid nozzle 51A. In this example, DHF, which also serves as a cleaning liquid, is started to be ejected. The DHF ejected from the back liquid nozzle 51A spreads toward the edge of the back side of the wafer W, thereby forming a state in which the entire back side of the wafer W is covered by a liquid film of DHF. The ejection flow rate of the temperature regulating liquid can be set to 1.5 L / min, for example, but is not limited to this. DHF is continuously ejected from the back liquid nozzle 51A until the first etching process is completed.

[0058] Next, while the two-fluid nozzle 41A is kept ejecting two fluids, the two-fluid nozzle 41A is moved at the first moving speed so as to approach the rotation center WC of the wafer W. Figure 3C This state is shown in . The two-fluid nozzle 41A moves to a position where it ejects the two fluids toward a radial position R2 that is further inward than the radial position R1 .

[0059] Next, while the two-fluid nozzle 41A continues to eject the two fluids, it is moved at a second speed greater than the first speed, toward the rotation center of wafer W. The two-fluid nozzle 41A moves to a position where it ejects the two fluids toward radial position R3, which is inward of radial position R2. After that, the ejection of the two fluids from the two-fluid nozzle 41A is stopped. The two-fluid nozzle 41A then moves to a position above the rotation center of wafer W.

[0060] When the radial position of the rotation center of wafer W is represented as 0 (zero) mm and the radial position of the edge of wafer W is represented as 150 mm, radial position R1 is, for example, 146 mm, radial position R2 is, for example, 100 mm, and radial position R3 is, for example, 75 mm (not limited to these values). In addition, the first moving speed is, for example, 15 mm / sec, and the second moving speed is, for example, 150 mm / sec (not limited to these values).

[0061] In this first etching step, an annular (ring-shaped) region outside the radial position R3 on the surface of the wafer W is etched. The circular region from the rotation center of the wafer W to the radial position R3 is not etched.

[0062] Specifically, the first etching step causes a relatively large etching of the area outside the radial position R2 on the surface of the wafer W, and a relatively small etching of the area between the radial position R3 and the radial position R2. As the wafer W is moved radially outward, the longer it is in contact with the DHF, as shown in FIG. Figure 4 As schematically shown in FIG. 1 , the closer a portion is to the edge of the wafer W, the more the oxide film, which is the film to be etched, is removed.

[0063] Furthermore, in this embodiment, the ultimate goal is to make the sum of the etching amount of the first etching step and the etching amount of the second etching step approximately constant over the entire surface of the wafer W, regardless of the radial position, as described later. The first etching step may be performed to achieve this goal, and the conditions of the first etching step are not limited to the above-described conditions. For example, the moving speed of the two-fluid nozzle 41A may be constant throughout the entire first etching step. Alternatively, the moving speed of the two-fluid nozzle 41A may be further varied in multiple stages, or may be varied steplessly.

[0064] Since the DHF ejected from the two-fluid nozzle 41A is in the form of mist (tiny droplets), it is easy to vaporize, and therefore the temperature is easy to drop. For example, when DHF at about 25°C is supplied to the two-fluid nozzle 41A, the temperature of the mist of DHF ejected from the two-fluid nozzle at the moment it lands on the surface of the wafer (hereinafter, for simplicity, also referred to as the "two-fluid temperature when landing") drops to, for example, about 18°C. Therefore, the wafer W is cooled by the two-fluid, and as a result, the etching rate decreases. However, since the DHF, whose temperature (for example, about 25°C) is higher than the two-fluid temperature when landing (for example, about 18°C), covers the entire back side of the wafer W, the temperature drop of the wafer W is suppressed. Therefore, the drop in the etching rate of the surface of the wafer W etched by the DHF ejected from the two-fluid nozzle 41A is also suppressed, thereby preventing the time required for the first etching process from increasing.

[0065] When the first etching step is completed, the discharge of the temperature regulating liquid (DHF) from the backside liquid nozzle 51A is temporarily stopped. Furthermore, the discharge of the two-fluid (DHF + N2 gas) from the two-fluid nozzle 41A is also temporarily stopped, and the two-fluid nozzle 41A is moved above the rotation center of the wafer W. The period during which the discharge of the temperature regulating liquid from the backside liquid nozzle 51A is stopped and the period during which the discharge of the two-fluid from the two-fluid nozzle 41A is stopped is short enough to prevent dry areas from forming on the front and back sides of the wafer W.

[0066] <Second Etching Step>

[0067] Next, DHF is ejected from the two-fluid nozzle 41A toward the rotation center WC of the wafer W. Subsequently, N₂ gas is supplied to the two-fluid nozzle 41A in addition to DHF, thereby ejecting a mixed fluid of DHF mist and N₂ gas, i.e., a two-fluid, toward the center of the wafer W. The flow rate of DHF supplied to the two-fluid nozzle 41A can be set to, for example, 0.1 L / min, but is not limited thereto.

[0068] Also, approximately simultaneously with the start of N2 gas supply to the two-fluid nozzle 41A (which may be slightly earlier or later), the backside liquid nozzle 51A begins to discharge a temperature-regulating liquid at a first temperature (e.g., approximately 25°C). In this example, discharge of DHF, which also functions as a cleaning liquid, begins, covering the backside of the wafer W with the temperature-regulating liquid. The discharge rate of the temperature-regulating liquid can be, for example, set to 1.5 L / min, but is not limited thereto. DHF discharge from the backside liquid nozzle 51A continues until the second etching step is completed.

[0069] The two-fluid nozzle 41A moves from a first position where the two-fluid is ejected toward the rotation center WC of the surface of the wafer W to a second position where the two-fluid is ejected toward a radial position R3 of the surface of the wafer W while ejecting the two-fluid. Figure 3D The state at this time is shown in . The two-fluid nozzle 41A may also repeat the following action multiple times: after moving from the first position to the second position, temporarily stop the ejection of the two-fluid, then return to the first position and start the ejection of the two-fluid at the first position, and move from the first position to the second position. Alternatively, the two-fluid nozzle 41A may be moved back and forth between the first position and the second position multiple times while ejecting the two-fluid. In this way, the etching target film on the surface of the wafer W is etched. If the moving speed of the two-fluid nozzle 41A is too low, a dry area may be generated near the rotation center of the wafer W, especially when the two-fluid nozzle 41A is in the second position. Therefore, the moving speed of the two-fluid nozzle 41A is set so that such a phenomenon does not occur.

[0070] The ejection of the temperature regulating liquid (DHF) from the back liquid nozzle 51A can be continued, but as long as no dry area is generated on the back side of the wafer W, the ejection of the temperature regulating liquid (DHF) from the back liquid nozzle 51A can also be interrupted in the middle of the second etching process. For example, the ejection of the temperature regulating liquid from the back liquid nozzle 51A can be stopped when the ejection of the two fluids from the two-fluid nozzle 41A is temporarily stopped and the two-fluid nozzle 41A is returned from the second position to the first position. The temporary interruption of the ejection of the temperature regulating liquid from the back liquid nozzle 51A can also be used to adjust the temperature distribution of the wafer W in this way. In addition, the temperature distribution of the wafer W can also be adjusted by changing the ejection flow rate of the temperature regulating liquid ejected from the back liquid nozzle 51A in the middle of the ejection.

[0071] Reference Figure 5 The distribution of etching amount in the second etching process is described in comparison with the comparative example. Figure 5 In the graph, the horizontal axis is the radial position R of the surface of the wafer W (0 mm is the rotation center, 150 mm is the edge), and the vertical axis is the Th-Ox (oxide film) etching rate (Th-Ox ER) (unit: angstrom / min).

[0072] In Comparative Example 1 (refer to Figure 5 In the curve C1), DHF at 25°C is continuously supplied to the center of rotation of the wafer surface at a flow rate of 1.5 L / min, and DIW at 25°C is continuously supplied to the center of rotation of the back of the wafer at a flow rate of 1.0 L / min as a temperature regulating liquid. The average etching rate is 31.3 Å / min, and the range of the etching rate (the difference between the maximum and minimum values ​​is 0.7 Å / min). The in-plane uniformity of the etching rate is high. In addition, Figure 5 Although not shown in the graph of , it was confirmed that in Comparative Example 1, even if the temperature regulating liquid was not supplied to the back surface of the wafer, the etching rate and its distribution remained almost unchanged.

[0073] In Comparative Example 2 (refer to Figure 5 In the curve C2 in FIG, the dual fluid (DHF+N2 gas) is continuously supplied to the wafer surface while the ejection position of the dual fluid is moved back and forth between the center and the periphery of the wafer. In addition, no temperature regulating liquid is supplied to the back of the wafer. The supply flow rate of DHF to the dual fluid nozzle is set to 0.1 L / min. The temperature of the dual fluid is 18°C ​​when the liquid falls. The average etching rate is 21.6 angstroms / min. The etching rate in Comparative Example 2 ranges from 1.2 angstroms / min, and the in-plane uniformity of the etching rate is lower than that of Comparative Example 1.

[0074] In the embodiment of the second etching process (refer to Figure 5 In curve C3, the dual-fluid nozzle (DHF + N2 gas) was continuously supplied while reciprocating between the center and periphery of the wafer. 25°C DIW was continuously supplied to the center of rotation on the back side of the wafer at a flow rate of 1.5 L / min as a temperature-regulating liquid. The dual-fluid temperature was 18°C ​​during the deposition. The average etching rate was 31.9 Å / min. The etching rate ranged from 4.2 Å / min, with the lowest in-plane uniformity.

[0075] Compared with Comparative Example 2, the only difference of the embodiment of the second etching process is that a temperature regulating liquid of room temperature (about 25°C) is supplied to the center of the back of the wafer. The temperature of the temperature regulating liquid is 25°C, which is higher than the 18°C ​​temperature of the dual fluid when the liquid is dropped. Therefore, the temperature of the wafer rises as a whole compared to Comparative Example 2, and therefore the etching rate rises as a whole. The temperature regulating liquid supplied to the center of the back of the wafer absorbs heat from the wafer cooled by the dual fluid while expanding toward the periphery of the back of the wafer. Therefore, a temperature distribution is generated in which the temperature is highest near the center of rotation of the wafer and the temperature decreases as it approaches the edge.

[0076] Figure 6 The five graphs in Figure 1 show the time-dependent temperature distribution of the wafer surface at 2-second intervals during the second etching step of an example. The horizontal axis represents the wafer's radial position R (distance from the rotation center WC (mm)), and the vertical axis represents the temperature T (°C). The black triangles indicate the position of the two-fluid nozzle. It can be seen that the portion of the wafer directly below the two-fluid nozzle is cooled by the two-fluid flow. After the two-fluid nozzle passes through, the temperature rises due to the influence of the temperature-regulating liquid supplied to the back surface.

[0077] In addition, if Figure 5 As shown, in Comparative Example 2, curve C2, representing the etching rate distribution, is W-shaped (the etching rate is lowest at a position approximately 50 mm from the center), but in the Example of the second etching step, it is an inverted U-shape, not a W-shape. This is presumably because the heating effect of the temperature-regulating liquid is much greater than the cooling effect of the two-fluid system.

[0078] Based on the above test results, if only the etching rate (size and uniformity) is considered, the results of Comparative Example 1 are the most preferable. However, by supplying a dual fluid to the wafer surface, the physical energy (kinetic energy) possessed by the dual fluid can be utilized to strongly remove particles and foreign matter attached to the wafer surface before etching, thereby having the great advantage of significantly improving the cleanliness of the wafer after etching.

[0079] Therefore, in the second etching process, a temperature-regulating liquid is supplied to the back of the wafer to compensate for the disadvantage of supplying two fluids to the wafer surface, namely, the decrease in etching rate caused by the cooling effect of the two fluids. In addition, a first etching process is provided to selectively etch the peripheral portion of the wafer to compensate for the disadvantage of uneven etching rate caused by supplying temperature-regulating liquid to the central portion of the back of the wafer (the etching rate in the center of the wafer is much higher than that in the peripheral portion). By combining the first etching process and the second etching process in this way, the uniformity of the etching rate within the wafer surface is improved to a level that does not cause problems.

[0080] In addition, the disadvantage of uneven etching rate caused by supplying temperature regulating liquid to the central part of the back side of the wafer may be eliminated by providing a so-called strip nozzle below the back side of the wafer. (In addition, as is well known in the art, a strip nozzle refers to a rod-shaped nozzle extending from below the center of the wafer to below the periphery of the wafer. There are also nozzles of a type that can supply liquid to different radial positions of the wafer under different conditions.) Providing such a strip nozzle will lead to an increase in the cost of the processing unit. Therefore, when it is necessary to supply liquid to the back side of the wafer W, liquid is usually supplied from the front end of the liquid supply pipe that passes through the hollow rotating shaft of the rotary chuck to the rotation center of the back side of the wafer W or its vicinity. In the above embodiment, even when using such a processing unit of conventional structure, the desired etching result can be obtained only by changing the operation method of the device.

[0081] From the perspective of reducing equipment and operating costs, it is most preferable to set the temperature of the temperature-regulating liquid ejected from the backside liquid nozzle during the second etching step to room temperature. However, the temperature of the temperature-regulating liquid only needs to be at least higher than the temperature of the two fluids at the time of deposition. The temperature of the temperature-regulating liquid can also be higher than room temperature, for example, around 30°C.

[0082] Next, reference data related to the above-mentioned embodiment will be described. Figure 7 It is a graph showing the experimental results obtained by investigating the relationship between the etching amount distribution and the temperature distribution in the second etching process. The experiment was carried out by spraying 25°C DIW at 1.5L / min from the back liquid nozzle 51A while making the dual-fluid nozzle 41A supplying dual fluids reciprocate multiple times between the rotation center of the wafer W and the aforementioned radial position R1. The horizontal axis is the radial position (RP) of the surface of the wafer W (0mm is the rotation center, 150mm is the edge), the left vertical axis is the etching rate (Th-Ox ER) (angstroms / min) of the Th-Ox (oxide film), and the right vertical axis is the time integral value (IT) of the actual temperature. The etching rate and the actual temperature were measured at radial positions of 0mm, 9mm, 37mm, 74mm, 110mm, and 147mm. The solid line represents the etching rate, and the dotted line represents the time integral value of the actual temperature. From Figure 7 It is clear that the etching rate (ie, etching amount) of the surface of the wafer W is the highest at the center and decreases toward the periphery; and that the etching amount distribution roughly corresponds to the temperature distribution.

[0083] Next, the steps after the second etching step will be briefly described.

[0084] <Rinsing process>

[0085] After the second etching process is completed by stopping the discharge of the two-fluid from the two-fluid nozzle 41A and the discharge of the temperature-regulating liquid DHF from the backside liquid nozzle 51A, a rinsing process is performed. Specifically, for example, DIW is discharged from the DIW nozzle 41C toward the center of the surface of the wafer W, while DIW is discharged from the backside liquid nozzle 51A toward the backside of the wafer W. At this time, the rotation speed of the wafer W is increased to, for example, 1000 rpm. Thus, both the front and back sides of the wafer W are rinsed.

[0086] <Drying Process>

[0087] Next, the supply of DIW to the front and back surfaces of wafer W is stopped, and wafer W is continued to rotate at high speed, thereby performing spin drying of wafer W. With these actions, the drying process is completed, and the series of liquid treatments for a single wafer is also completed. At this time, N2 gas may also be ejected from back surface gas nozzle 51B.

[0088] In addition, in a modified example, after the rinsing process, a replacement process is performed to replace the DIW on the surface of the wafer W with a low surface tension and high volatility drying organic solvent such as IPA (isopropyl alcohol), and then a drying process is performed. In the drying process, a drying gas with low oxygen concentration and low humidity such as nitrogen can also be supplied to the surface of the wafer W. In this case, an IPA nozzle and an N2 nozzle can also be provided as the above-mentioned surface nozzle 41. In this case, the rinsing process and the drying process on the back side of the wafer W can be the same as the processes described above.

[0089] [Other embodiments]

[0090] Alternatively, the first etching process can be performed by moving the dual-fluid nozzle 41A that sprays dual fluids (DHF+N2) between the aforementioned first position and second position (e.g., reciprocating motion) while spraying a low-temperature temperature regulating liquid from the back liquid nozzle 51A. In this case, the temperature of the temperature regulating liquid is set to a temperature lower than the "dual-fluid temperature when the dual fluids from the dual-fluid nozzle 41A fall." The low-temperature temperature regulating liquid sprayed from the back liquid nozzle 51A absorbs heat from the wafer W while expanding toward the peripheral portion of the wafer W. Therefore, the same as Figure 5 The temperature distribution is opposite to that of curve C3, with a lower temperature at the center and a higher temperature at the periphery. As previously explained, the etching amount distribution roughly corresponds to the temperature distribution, so an etching amount distribution similar to that of the first etching step described above can be obtained. In this case, the second etching step can be the same as the second etching step in the previously described embodiment, and in this case, the same effects as those of the previously described embodiment can be achieved.

[0091] The embodiments disclosed herein are illustrative in all respects and should not be construed as restrictive. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope of the appended claims and the spirit thereof.

[0092] For example, the etching treatment of the wafer surface in the second etching process can also be carried out without using a dual fluid (that is, by a liquid medicine that is not mixed with N2 gas). Regardless of whether the liquid medicine supplied to the wafer surface is a dual fluid, in the second etching process, there may be a situation where the etching amount of the center of the wafer is greater than the etching amount of the peripheral portion of the wafer. For example, when the temperature of the temperature regulating liquid supplied to the central portion of the back of the wafer is higher than the temperature of the liquid medicine supplied to the wafer surface while moving the liquid landing point along the radial direction of the wafer, such an etching amount distribution may be produced. In addition, when the flow rate of the temperature regulating liquid supplied to the central portion of the back of the wafer is greater than the flow rate of the liquid medicine supplied to the wafer surface, such an etching amount distribution may also be produced. In such a case, it is also beneficial to implement the first etching process under the condition of eliminating the uneven etching amount distribution in the second etching process.

[0093] Alternatively, for example, during the first half of the second etching process, the two-fluid nozzle 41A may be moved back and forth between the center and periphery of the wafer while ejecting the two-fluid. During the second half, DHF that does not contain N2 gas (not in mist form) may be supplied from the two-fluid nozzle 41A. In this case, during the second half, the two-fluid nozzle 41A may be moved between the first and second positions or fixed at the first position.

[0094] In at least one period of the first etching step, non-atomized DHF may be used as the etching solution.

[0095] The etching liquid is not limited to DHF, and any etching liquid having a temperature-dependent etching rate can be used.

[0096] The substrate to be processed is not limited to a semiconductor wafer, but may be various substrates used in the field of semiconductor device manufacturing, such as a glass substrate and a ceramic substrate.

Claims

1. A substrate processing method comprising the following steps: In a first etching step, the etching liquid is supplied to the surface of the substrate while the substrate is rotated, and etching is performed under conditions such that the etching amount of the etching target film in a second region on the peripheral side of the substrate surface is greater than the etching amount of the etching target film in a first region on the central side of the substrate surface; as well as A second etching step is performed after the first etching step, wherein the etching liquid is supplied to the surface of the substrate while the substrate is rotated, and etching is performed under conditions such that an etching amount of the etching target film in the second area of ​​the substrate surface is smaller than an etching amount of the etching target film in the first area of ​​the substrate surface. wherein the first etching process is performed before the second etching process, The second etching step is performed under conditions where the temperature of the substrate is higher than that in the case where the temperature regulating liquid is not supplied by supplying a temperature regulating liquid to the center portion of the back surface of the substrate. In the second etching step, the temperature regulating liquid absorbs heat from the substrate while spreading toward the periphery of the substrate, thereby making the temperature of the first region on the surface of the substrate higher than that of the second region. The sum of the etching amount in the first etching step and the etching amount in the second etching step is constant over the entire surface of the substrate regardless of the radial position.

2. The substrate processing method according to claim 1, wherein: The first etching step is performed under conditions such that the etching amount of the etching target film in the second region increases as the etching amount approaches the periphery of the substrate.

3. The substrate processing method according to claim 2, wherein: The first etching step is performed while the landing position of the etching liquid on the surface of the substrate is moved from the peripheral edge side of the substrate toward the center side of the substrate within the second region.

4. The substrate processing method according to claim 1, wherein: In the first etching step, the etching liquid is supplied only to the second region of the substrate, and the etching amount of the etching target film in the first region is zero.

5. The substrate processing method according to claim 4, wherein: The first etching step is performed with a liquid film of a protective liquid different from the etching liquid formed on the entire surface of the substrate. The protective liquid film prevents the etching liquid from directly landing on at least the first area of ​​the substrate surface.

6. The substrate processing method according to claim 5, wherein: The protective liquid is pure water.

7. The substrate processing method according to claim 1, wherein: In the second etching process, the following actions are performed one or more times: the etching liquid is supplied to the surface of the substrate in the form of a two-fluid that is atomized and mixed with a gas, and the falling position of the etching liquid on the surface of the substrate is moved from the center of the substrate to the periphery or from the periphery of the substrate to the center.

8. The substrate processing method according to claim 7, wherein: In the second etching step, the temperature of the temperature-adjusting liquid supplied to the center portion of the rear surface of the substrate is set to be higher than the temperature of the two-fluid at the time of landing on the surface of the substrate.

9. The substrate processing method according to claim 1, wherein: The second etching step is performed under conditions such that the etching amount of the etching target film on the surface of the substrate decreases from the center toward the periphery of the substrate.

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