Substrate processing apparatus and substrate processing method

Abstract

To provide a substrate processing method and a substrate processing device for forming a liquid film of concentrated sulfuric acid of 90 wt.% or more on the upper surface of a substrate.SOLUTION: A substrate processing method for forming a liquid film of concentrated sulfuric acid of 90 wt.% or more on the upper surface of a substrate having an upper surface held substantially horizontally includes a first step of supplying concentrated sulfuric acid to an upper surface, a second step of rotating the substrate at a rotational speed such that the concentrated sulfuric acid on the upper surface is not shaken off from the upper surface, in parallel with the first step or after the completion of the first step when a target value of the liquid film thickness is a predetermined value or more, and a third step of rotating the substrate at a rotational speed such that the concentrated sulfuric acid is shaken off from the upper surface in parallel with the first step or after the completion of the first step when the target value is less than the predetermined value.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The technology disclosed in the present specification relates to a substrate processing apparatus and a substrate processing method.

Background Art

[0002] There is known a technology in which plasma is applied to a liquid film of a chemical solution on a substrate to change the chemical solution on the substrate into a chemical solution in which radicals having a strong oxidizing power are generated. For example, the apparatus described in Patent Document 1 includes an electrode group and a dielectric. The dielectric has a first main surface and a second main surface on the side opposite to the first main surface. The electrode group is sealed by the dielectric and includes at least one first electrode and at least one second electrode alternately arranged in an array plane parallel to the first main surface, and an electric field generated by applying a high-frequency voltage between the first electrode and the second electrode acts outside the first main surface. The apparatus described in Patent Document 1 generates plasma at a low voltage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The apparatus described in Patent Document 1 generates plasma in a state where a chemical solution exists as a liquid film on the upper surface of a substrate. The plasma acts on the liquid film of the chemical solution. As a result, radicals having a strong oxidizing power are generated in the liquid film of the chemical solution. Thereby, substrate processing using the chemical solution can be efficiently performed.

[0005] Such a chemical solution preferably contains sulfuric acid. This is because when sulfuric acid is contained, peroxomonosulfuric acid (caro's acid) is generated by irradiating plasma onto the sulfuric acid. At this time, hydrogen peroxide solution, which is usually used for the generation of peroxomonosulfuric acid, is not required.

[0006] However, since sulfuric acid has a high viscosity at room temperature, it has been difficult to uniformly form a liquid film on the upper surface of a substrate or control the thickness of the liquid film using, for example, concentrated sulfuric acid of 90 wt% or more. On the other hand, because efficient processing of the substrate can be achieved with strong oxidizing power, it has been desired to uniformly form a liquid film of concentrated sulfuric acid with a desired thickness on the upper surface of the substrate.

[0007] The technology disclosed in the present specification has been made in view of the problems described above. This technology relates to a substrate processing method and a substrate processing apparatus for forming a liquid film of concentrated sulfuric acid of 90 wt% or more on the upper surface of a substrate.

Means for Solving the Problems

[0008] A first aspect of the substrate processing method disclosed in the present specification is a substrate processing method for forming a liquid film of concentrated sulfuric acid of 90 wt% or more on the upper surface of a substrate having an upper surface held substantially horizontally, the method comprising: a first step of supplying the concentrated sulfuric acid to the upper surface; a second step of rotating the substrate at a rotational speed such that the concentrated sulfuric acid on the upper surface is not shaken off the upper surface, in parallel with the first step or after completion of the first step, when the target value of the thickness of the liquid film is equal to or greater than a predetermined value; and a third step of rotating the substrate at a rotational speed such that the concentrated sulfuric acid is shaken off the upper surface, in parallel with the first step or after completion of the first step, when the target value is less than the predetermined value.

[0009] A second aspect of the substrate processing method disclosed in the present specification is that, in the first aspect, in the first step, when the target value is equal to or greater than the predetermined value, an amount of concentrated sulfuric acid corresponding to the product of the target value and the area of the upper surface is supplied to the upper surface, and when the target value is less than the predetermined value, an amount of concentrated sulfuric acid corresponding to a value greater than the product is supplied to the upper surface.

[0010] A third aspect of the substrate processing method disclosed in the present specification is that, in the first or second aspect, the predetermined value is between 300 μm and 400 μm.

[0011] A fourth aspect of the substrate processing method disclosed in the present specification is that, in any one of the first to third aspects, after the second step or after the third step, a fourth step of rotating the substrate at a higher rotational speed as the amount of recess at the center of the upper surface with respect to the periphery of the upper surface increases is further provided.

[0012] A fifth aspect of the substrate processing method disclosed in the present specification is that, in any one of the first to third aspects, after the second step or after the third step, a fifth step of irradiating the liquid film obtained by the second step or the third step with plasma is further provided.

[0013] A sixth aspect of the substrate processing method disclosed in the present specification is that, in the fifth aspect, in the fifth step, the amount of recess at the center of the upper surface with respect to the periphery of the upper surface is measured over time, and the substrate is rotated at a rotational speed that increases as the amount of recess increases.

[0014] A first aspect of the substrate processing apparatus disclosed in the present specification is a substrate processing apparatus that forms a liquid film of concentrated sulfuric acid with a concentration of 90 wt% or more on the upper surface of a substrate having an upper surface held substantially horizontally. The apparatus includes a holding unit that holds the substrate with the upper surface substantially horizontal, a supply unit that supplies the concentrated sulfuric acid to the upper surface, a rotating unit that rotates the substrate, and a control unit. When the target value of the thickness of the liquid film is equal to or greater than a predetermined value, the control unit controls the rotating unit to rotate the substrate at a rotation speed such that the concentrated sulfuric acid is not shaken off the upper surface when the concentrated sulfuric acid is supplied to the upper surface or after the concentrated sulfuric acid is supplied to the upper surface. When the target value is less than the predetermined value, the control unit controls the rotating unit to rotate the substrate at a rotation speed such that the concentrated sulfuric acid is shaken off the upper surface when the concentrated sulfuric acid is supplied to the upper surface or after the concentrated sulfuric acid is supplied to the upper surface.

[0015] A second aspect of the substrate processing apparatus disclosed in the present specification is, in the first aspect, when the target value is equal to or greater than the predetermined value, the control unit controls the supply unit to supply an amount of the concentrated sulfuric acid corresponding to the product of the target value and the area of the upper surface to the upper surface. When the target value is less than the predetermined value, the control unit controls the supply unit to supply an amount of the concentrated sulfuric acid corresponding to a value greater than the product to the upper surface.

[0016] A third aspect of the substrate processing apparatus disclosed in the present specification is, in the first or second aspect, the predetermined value is between 300 μm and 400 μm.

[0017] A fourth aspect of the substrate processing apparatus disclosed in the present specification is, in any one of the first to third aspects, further includes a plasma irradiation unit that irradiates plasma to the liquid film.

[0018] A fifth aspect of the substrate processing apparatus disclosed in the present specification is, in the fourth aspect, the control unit controls the rotating unit to rotate the substrate at a higher rotation speed as the amount of depression of the upper surface at the center of the upper surface with respect to the periphery of the upper surface is larger.

[0019] The sixth aspect of the substrate processing apparatus disclosed in the present specification further includes a recess measurement unit that measures the amount of recess on the upper surface at the center of the upper surface with reference to the periphery of the upper surface in any one of the first to fifth aspects.

Advantages of the Invention

[0020] According to the substrate processing methods of the first to sixth aspects and the substrate processing apparatuses of the first to sixth aspects disclosed in the present specification, there are provided a substrate processing method and a substrate processing apparatus for forming a liquid film of concentrated sulfuric acid with a concentration of 90 wt% or more on the upper surface of a substrate.

[0021] The objects, features, aspects, and advantages related to the technology disclosed in the present specification will become more apparent from the following detailed description and the accompanying drawings.

Brief Description of the Drawings

[0022]

Figure 1

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Mode for Carrying Out the Invention

[0023] Hereinafter, embodiments will be described with reference to the accompanying drawings. Note that the drawings are schematically shown, and for the sake of convenience of explanation, omissions and simplifications of the configuration are made as appropriate. Also, the sizes and positional interrelationships of the configurations shown in the drawings are not necessarily accurately described and can be changed as appropriate.

[0024] Also, in the following description, the same reference numerals are given to the same components in the drawings, and their names and functions are also regarded as the same. Therefore, detailed descriptions thereof may be omitted to avoid duplication.

[0025] Also, in the following description, even when ordinal numbers such as "first" or "second" are used, these terms are used for convenience in order to facilitate understanding of the content of the embodiments and are not limited to the order that may be caused by these ordinal numbers.

[0026] Expressions indicating relative or absolute positional relationships (e.g., "in one direction", "along one direction", "parallel", "orthogonal", "center", "concentric", "coaxial") shall, unless otherwise specified, not only represent such positional relationships precisely, but also represent states where displacement has occurred with respect to the angle or distance within the range where tolerances or equivalent functions can be obtained. Expressions indicating an equal state (e.g., "identical", "equal", "homogeneous") shall, unless otherwise specified, not only represent a quantitatively exact equal state, but also represent a state where there are differences within the range where tolerances or equivalent functions can be obtained. Expressions indicating a shape (e.g., "quadrangular shape" or "cylindrical shape") shall, unless otherwise specified, not only represent such a shape geometrically precisely, but also represent a shape that has been deformed within the range where equivalent effects can be obtained, for example, a shape having unevenness or chamfers. Expressions such as "comprising", "having", "including", or "possessing" one component do not exclude the presence of other components. The expression "at least any one of A, B, and C" includes only A, only B, only C, any two of A, B, and C, and all of A, B, and C.

[0027] <First Embodiment> <Overall Configuration of Substrate Processing System> FIG. 1 is a plan view schematically showing an example of the configuration of a substrate processing system 100. The substrate processing system 100 is a single-wafer processing apparatus that processes one substrate W to be processed at a time. After processing the substrate W, which is a disk-shaped semiconductor substrate, the substrate processing system 100 performs a drying process. As one of the processes for the substrate W, a process using plasma is included. Although the process using plasma does not particularly need to be limited, as a more specific example, it includes an organic matter removal process. The organic matter removal process is a process for removing organic matter on the main surface of the substrate W, and a resist can be applied as the organic matter. When the organic matter is a resist, the organic matter removal process can also be said to be a resist removal process. Here, a resist is formed on the main surface of the substrate W, and the substrate processing system 100 will be described by taking as an example the removal of the resist as a process for the substrate W.

[0028] Note that the substrate W is not necessarily limited to a semiconductor substrate. For example, various substrates such as a glass substrate for a photomask, a glass substrate for a liquid crystal display, a glass substrate for a plasma display, a substrate for a FED (Field Emission Display), a substrate for an optical disk, a substrate for a magnetic disk, and a substrate for a magneto-optical disk can be applied to the substrate W. Also, the shape of the substrate is not limited to a disk shape, and various shapes such as a rectangular plate shape can be adopted.

[0029] The substrate processing system 100 includes a load port 101, an indexer robot 110, a main transfer robot 120, a plurality of processing units 130, and a control unit 90.

[0030] As illustrated in FIG. 1, a plurality of load ports 101 are arranged side by side. A carrier C is carried into each load port 101. As the carrier C, a FOUP (Front Opening Unified Pod) that houses the substrate W in a sealed space, a SMIF (Standard Mechanical Inter Face) pod, or an OC (Open Cassette) that exposes the substrate W to the outside air may be adopted. The indexer robot 110 transfers the substrate W between the carrier C and the main transfer robot 120. The main transfer robot 120 transfers the substrate W to the processing unit 130.

[0031] The processing unit 130 performs processing on the substrate W. In the substrate processing system 100 according to the present embodiment, 12 processing units 130 are arranged.

[0032] Specifically, four towers each including three processing units 130 stacked in the vertical direction are arranged so as to surround the main transfer robot 120.

[0033] In FIG. 1, one of the processing units 130 stacked in three stages is schematically shown. Note that the number of processing units 130 in the substrate processing system 100 is not limited to 12 and may be appropriately changed.

[0034] The main transfer robot 120 is installed at the center of four towers on which the processing units 130 are stacked. The main transfer robot 120 carries the substrate W to be processed received from the indexer robot 110 into each processing unit 130. Also, the main transfer robot 120 carries out the processed substrate W from each processing unit 130 and delivers it to the indexer robot 110. The control unit 90 controls the operations of the respective components of the substrate processing system 100.

[0035] FIG. 2 is a functional block diagram schematically showing an example of the internal configuration of the control unit 90. The control unit 90 is an electronic circuit and has, for example, a data processing unit 91 and a storage medium 92. In the specific example of FIG. 2, the data processing unit 91 and the storage medium 92 are interconnected via a bus 93. The data processing unit 91 may be an arithmetic processing unit exemplified by a CPU (Central Processor Unit). The storage medium 92 may have a non-temporary storage medium (for example, ROM (Read Only Memory) or hard disk) 921 and a temporary storage medium (for example, RAM (Random Access Memory)) 922. For example, a program defining the processing executed by the control unit 90 may be stored in the non-temporary storage medium 921. By the data processing unit 91 executing this program, the control unit 90 can execute the processing defined in the program. Of course, part or all of the processing executed by the control unit 90 may be executed by hardware. In the specific example of FIG. 2, an example of the mode in which the indexer robot 110, the main transfer robot 120, and the processing unit 130 are connected to the bus 93 is schematically shown.

[0036] <Processing Unit> FIG. 3 is a diagram schematically showing an example of the configuration of the processing unit 130. Note that not all the processing units 130 belonging to the substrate processing system 100 need to have the configuration shown in FIG. 3, and at least one processing unit 130 may have the configuration.

[0037] The processing unit 130 illustrated in FIG. 3 is an apparatus that performs processing using plasma on a substrate W. The substrate W has, for example, a disk shape. Although the size of the substrate W is not particularly limited, its diameter R1 is, for example, about 300 mm.

[0038] The processing unit 130 includes a plasma reactor 1, a substrate holder 3, and a guard 7. In the example of FIG. 3, the processing unit 130 also includes a chamber 80. The chamber 80 forms a processing chamber for processing the substrate W and houses various components described later.

[0039] In the example of FIG. 3, the substrate holder 3 holds the substrate W with the upper surface of the substrate W substantially horizontal. The substrate holder 3 further includes a rotation mechanism 33 that rotates the substrate W around a rotation axis Q1. The rotation axis Q1 passes through the central portion of the substrate W and is an axis along the vertical direction. The rotation mechanism 33 includes, for example, a shaft 34 and a motor 35. The upper end of the shaft 34 is connected to the lower surface of the spin base 31. The motor 35 rotates the shaft 34 around the rotation axis Q1 to rotate the spin base 31. Thereby, the substrate W held by the plurality of chuck pins 32 rotates around the rotation axis Q1. Such a substrate holder 3 may also be called a spin chuck. Hereinafter, the radial direction with respect to the rotation axis Q1 is simply referred to as the radial direction.

[0040] In the example of FIG. 3, the processing unit 130 also includes a nozzle 4. The nozzle 4 is provided in the chamber 80 and is used for supplying a processing liquid to the upper surface of the substrate W. The nozzle 4 is connected to a processing liquid supply source 44 via a supply pipe 41. The processing liquid supply source 44 includes, for example, a tank (not shown) for storing the processing liquid. The processing liquid is, for example, concentrated sulfuric acid of 90 wt% or more, preferably 96 wt% concentrated sulfuric acid. A valve 42 is interposed in the supply pipe 41. When the valve 42 opens, the processing liquid from the processing liquid supply source 44 is supplied to the nozzle 4 through the supply pipe 41 and discharged from the discharge port 4a of the nozzle 4. The concentrated sulfuric acid processing liquid supplied to the upper surface of the substrate W forms a liquid film.

[0041] In the example of FIG. 3, the nozzle 4 is movably provided by a nozzle moving mechanism 45. The nozzle moving mechanism 45 moves the nozzle 4 between a nozzle processing position and a nozzle standby position. The nozzle processing position is a position where the nozzle 4 discharges the processing liquid toward the upper surface of the substrate W. The nozzle processing position is, for example, vertically above the substrate W and in a position vertically opposed to the central portion of the substrate W. The nozzle standby position is, for example, a position radially outside the peripheral edge of the substrate W. In FIG. 3, the nozzle 4 stopped at the nozzle standby position is shown.

[0042] The nozzle moving mechanism 45 has, for example, a ball screw mechanism or an arm turning mechanism. The arm turning mechanism includes an arm, a support column, and a motor (all not shown). The arm has a rod-like shape extending horizontally, the nozzle 4 is connected to the tip of the arm, and the base end of the arm is connected to the support column. The support column extends along the vertical direction and is rotatably provided around its central axis. When the motor rotates the support column, the arm turns and the nozzle 4 moves along the circumferential direction around the central axis. The support column is provided so that the nozzle processing position and the nozzle standby position are located on the movement path of the nozzle 4.

[0043] When the valve 42 opens in a state where the nozzle 4 is located at the nozzle processing position, the processing liquid is discharged from the nozzle 4 toward the upper surface of the substrate W. By rotating the substrate W by the substrate holding unit 3, the processing liquid spreads over the upper surface of the substrate W by centrifugal force and scatters outward from the peripheral edge of the substrate W. Thereby, a liquid film of the processing liquid is formed on the upper surface of the substrate W.

[0044] The nozzle 4 may sequentially discharge a plurality of types of processing liquids. In this case, the nozzle 4 may be connected to another processing liquid supply source (not shown) through a supply pipe (not shown) branched from the supply pipe 41. Alternatively, a plurality of nozzles 4 may be provided, and each nozzle 4 may be connected to a plurality of processing liquid supply sources. The nozzle moving mechanism 45 may move a plurality of nozzles 4 integrally or individually. As processing liquids other than sulfuric acid, for example, rinsing liquids such as pure water and isopropyl alcohol are applicable.

[0045] In the example of FIG. 3, the processing unit 130 also includes a film thickness measurement unit 5. The film thickness measurement unit 5 is provided in the chamber 80 and is used to measure the thickness of the liquid film formed on the upper surface of the substrate W. A distance measuring device, which is a well-known technique, is used for the film thickness measurement unit 5. As the distance measuring device, for example, those using light waves, radio waves, or ultrasonic waves using laser light are used. The film thickness measurement unit 5 is connected to the control unit 90, and the thickness of the liquid film measured by the film thickness measurement unit 5 is stored in the RAM 922 of the control unit 90.

[0046] In the example of FIG. 3, the film thickness measurement unit 5 is movably provided by a film thickness measurement unit moving mechanism 51. The film thickness measurement unit moving mechanism 51 moves the film thickness measurement unit 5 between the measurement position and the standby position. The measurement position is the position where the film thickness measurement unit 5 measures the thickness of the liquid film formed on the upper surface of the substrate W. The measurement position is, for example, vertically above the substrate W and in a position vertically facing the central portion of the substrate W. The standby position is a position that does not interfere with the plasma reactor 1. The standby position is, for example, a position radially outside the peripheral edge of the substrate W. Note that a well-known moving technique is used for the film thickness measurement unit moving mechanism 51.

[0047] The guard 7 is provided in the chamber 80 and has a cylindrical shape surrounding the substrate holding portion 3 and the substrate W held by the substrate holding portion 3. The guard 7 receives the processing liquid scattered from the peripheral edge of the substrate W.

[0048] In the example of FIG. 3, the guards 7 each include a cylindrical portion 71, an inclined portion 72, and an upper end portion 73 surrounding the substrate holding portion 3. The inclined portion 72 is inclined so as to approach the rotation axis Q1 as it goes vertically upward. That is, the inner diameter and the outer diameter of the inclined portion 72 become smaller as it goes vertically upward. The upper end of the cylindrical portion 71 is continuous with the lower end of the inclined portion 72, and the cylindrical portion 71 extends along the vertical direction. In the example of FIG. 3, the upper end of the inclined portion 72 is continuous with the outer peripheral edge of the upper end portion 73. The upper end portion 73 has a ring-shaped plate shape extending horizontally. In the example of FIG. 3, the upper surface and the lower surface of the upper end portion 73 are parallel to the horizontal plane. The inner peripheral edge of the upper end portion 73 forms the upper opening of the guard 7.

[0049] In the example of FIG. 3, the processing unit 130 includes a plurality of guards 7. The plurality of guards 7 are provided concentrically and all surround the substrate holding unit 3. In the example of FIG. 3, two guards 7 are provided. Hereinafter, the outermost guard 7 is referred to as guard 7A, and the innermost guard 7 is also referred to as guard 7B.

[0050] The guard 7 is provided so as to be movable up and down by a guard elevating mechanism 75. The guard elevating mechanism 75 raises and lowers the guard 7 between the upper position and the guard standby position. The upper position is the position where the guard 7 receives the processing liquid. Specifically, it is the position where the upper end 711 of the inner peripheral surface of the guard 7 is vertically above the upper surface of the substrate W. The guard standby position is, for example, the position where the upper surface of the upper end portion 73 of the guard 7 is vertically below the upper surface of the spin base 31. In the example of FIG. 3, the guard 7 stopped at the guard standby position is shown. The guard elevating mechanism 75 may include, for example, a ball screw mechanism and a motor that applies a driving force to the ball screw mechanism, or may include an air cylinder. When a plurality of guards 7 are provided, the guard elevating mechanism 75 raises and lowers the guards 7 individually.

[0051] In a state where the guard elevating mechanism 75 raises the guards 7A and 7B to the upper position, the processing liquid scattered from the periphery of the substrate W is received by the inner peripheral surface of the guard 7B and flows down along the inner peripheral surface of the guard 7B. The processing liquid flowing down along the inner peripheral surface of the guard 7B is received by the cup 76. The processing liquid is recovered, for example, into a tank of the same type of processing liquid supply source through a recovery pipe 77 connected to the cup 76.

[0052] In a state where the guard elevating mechanism 75 lowers the guard 7B to the guard standby position and raises the guard 7A to the upper position, the processing liquid scattered from the periphery of the substrate W is received by the inner peripheral surface of the guard 7A and flows down along the inner peripheral surface of the guard 7A. The processing liquid flowing down along the inner peripheral surface of the guard 7A is received by a cup (not shown). The processing liquid is recovered, for example, into a tank of the same type of processing liquid supply source through a recovery pipe (not shown) connected to the cup.

[0053] As described above, by providing a plurality of guards 7, the processing liquid can be recovered according to its type.

[0054] The plasma reactor 1 is a plasma generating device that generates plasma, and is provided at a position facing the upper surface of the substrate W held by the substrate holding portion 3 in the vertical direction within the chamber 80. The plasma reactor 1 is connected to a plasma power source 16, and receives power from the power source 16 to plasmaize the surrounding gas. Here, as an example, the plasma reactor 1 generates plasma under atmospheric pressure. The atmospheric pressure referred to here is, for example, 80% or more and 120% or less of the standard atmospheric pressure.

[0055] The plasma reactor 1 is a flat plasma reactor having a flat shape. In a plan view, the plasma reactor 1 extends radially outside the periphery of the substrate W. The outer peripheral edge of the plasma reactor 1 has, for example, a circular shape in a plan view, and its outer diameter R2 is larger than the diameter R1 of the substrate W. In the example of FIG. 3, the outer diameter R2 of the plasma reactor 1 is larger than the inner diameter (corresponding to the upper opening diameter) R3 of the upper end portion 73 of the guard 7. According to this structure, the portion of the plasma reactor 1 outside the periphery of the substrate W faces the upper end portion 73 of the guard 7 in the vertical direction. An example of the specific internal configuration of the plasma reactor 1 will be described in detail later.

[0056] The plasma reactor 1 can move from the plasma standby position to the plasma processing position in a state where the nozzle 4 is retracted to the nozzle standby position and all the guards 7 are lowered to, for example, the guard standby position. The plasma reactor 1 moves to the plasma processing position, for example, in a state where a liquid film F1 of the processing liquid is formed on the upper surface of the substrate W (see also FIG. 11).

[0057] The plasma reactor 1 irradiates the upper surface of the substrate W in a processing state where the guard 7 is in the lower position (for example, the guard standby position) and the plasma reactor 1 is in the plasma processing position. When the plasma reactor 1 generates plasma, various active species are generated. For example, when air is plasmaized, various active species such as oxygen radicals, hydroxyl radicals, and ozone gas can be generated. These active species act on the upper surface of the substrate W. As a specific example, the active species act on the liquid film of the processing liquid (sulfuric acid here) on the upper surface of the substrate W. Thereby, the processing performance of the processing liquid is enhanced. Specifically, by the reaction of the active species and sulfuric acid, caroic acid with high processing performance (oxidizing power here) is generated. Caroic acid is also called peroxymonosulfuric acid. When the caroic acid acts on the resist of the substrate W, the resist is oxidized and removed.

[0058] Due to the generation of plasma, the temperature around the plasma reactor 1 rises. For example, the temperature reaches several hundred degrees Celsius, and more specifically, it reaches about 200 degrees Celsius to 350 degrees Celsius. Thereby, the processing liquid on the upper surface of the substrate W is likely to evaporate, and the atmosphere directly above the substrate W contains a large amount of volatile components of the processing liquid. When such a processing liquid atmosphere diffuses into the chamber 80, the volatile components of the processing liquid may adhere to the members in the chamber 80 and cause problems. Therefore, the processing unit 130 is provided with an air supply unit (not shown) and an exhaust unit 82.

[0059] In the example of FIG. 3, the exhaust unit 82 includes a cylindrical member 83 and an exhaust pipe 84. The cylindrical member 83 is provided in the chamber 80. The cylindrical member 83 has a cylindrical shape and surrounds the guard 7 from the outer peripheral side of the outermost periphery of the guard 7. The cylindrical member 83 is provided on the floor surface of the chamber 80. The upstream end of the exhaust pipe 84 is connected to the lower part of the cylindrical member 83, and the downstream end of the exhaust pipe 84 is connected to a suction mechanism (not shown). The processing liquid atmosphere above the substrate W flows into the upstream end of the exhaust pipe 84 through the inside of the guard 7 and is discharged to the outside of the chamber 80 through the exhaust pipe 84. In FIG. 3, the flow of this air current is schematically shown by a dashed arrow.

[0060] Note that the above-described rotation mechanism 33, valve 42, nozzle movement mechanism 45, and plasma generator are controlled by the control unit 90. Also, the film thickness measurement unit 5 and the film thickness measurement unit movement mechanism 51 are also controlled by the control unit 90.

[0061] FIG. 4 is a front view showing an enlarged view of the spin base 31 and the chuck pin 32 of the substrate holding unit 3. FIG. 5 is a schematic diagram showing the amount of depression t on the upper surface of the substrate W. The processing unit 130 further includes a depression measurement unit 36. In the example of FIG. 4, the depression measurement unit 36 is attached to the chuck pin 32. As the depression measurement unit 36, a distance measurement device, which is a well-known technique, is used. As the distance measurement device, for example, an optical wave type, radio wave type, or ultrasonic wave type using laser light is used.

[0062] The depression measurement unit 36 measures the amount of depression on the upper surface at the center of the upper surface with reference to the peripheral edge of the upper surface of the substrate W. Then, the amount of depression t on the upper surface of the substrate W shown in FIG. 5 is measured by the depression measurement unit 36. Note that the depression measurement unit 36 is also connected to the control unit 90, and the amount of depression t measured by the depression measurement unit 36 is stored in the RAM 922 of the control unit 90.

[0063] <Operation Example of Substrate Processing Apparatus> Next, an example of the operation of the processing unit 130 will be described. Here, since concentrated sulfuric acid has a high viscosity at room temperature (20°C ± 15°C), it is not easy to control the thickness of the liquid film. On the other hand, since the film thickness of the processing liquid on the upper surface of the substrate W affects the fineness of the pattern of the substrate W, control in units of μm is necessary. Therefore, by associating the thickness of the liquid film, the supply amount of the processing liquid, and the rotation speed of the substrate W, the thickness of the liquid film can be controlled.

[0064] In this embodiment, the method for forming the liquid film differs depending on the target value T of the thickness of the liquid film. Therefore, in this embodiment, the operation of the processing unit 130 also differs depending on the target value T. FIG. 6 is a flowchart showing an example of the operation of the processing unit 130. First, the substrate holding unit 3 holds the substrate W (step S1: holding step). Specifically, the main transfer robot 120 passes the unprocessed substrate W to the substrate holding unit 3, and the substrate holding unit 3 holds the substrate W. At this time, the substrate holding unit 3 holds the peripheral portion of the substrate W with the upper surface of the substrate W substantially horizontal.

[0065] The supply amount of the processing liquid and the rotation speed of the substrate W are controlled by the control unit 90. Specifically, a liquid film control recipe for controlling the thickness of the liquid film of the processing liquid is determined (step S2: liquid film control recipe determination step). FIG. 7 is a flowchart showing a specific example of the liquid film control recipe determination step. First, the target value T is input to the control unit 90 (step S11: target value input step). Whether the target value T input in step S11 is greater than or equal to a predetermined value is determined by the control unit 90 (step S12). Note that the predetermined value is, for example, between 300 μm and 400 μm.

[0066] In step S12, when it is determined that the target value T is greater than or equal to the predetermined value, the supply amount of the processing liquid is determined to be an amount corresponding to the product of the target value T and the area of the upper surface of the substrate W (step S13). For example, when the target value T is 400 μm and the diameter of the substrate W is 300 mm, 400 μm × (150 mm × 150 mm × π) ≈ 28.3 ml is determined as the supply amount of the processing liquid. Thereafter, the rotation speed is determined such that the processing liquid on the upper surface of the substrate W is not thrown off from the upper surface of the substrate W (step S14). At this time, the thickness of the liquid film may be measured by the film thickness measurement unit 5. The rotation speed at which the processing liquid is not thrown off from the upper surface of the substrate W has been obtained by experiment in advance. Note that the rotation speed also needs to be such that the processing liquid spreads due to centrifugal force. Therefore, the rotation speed is preferably such that the processing liquid is not thrown off and spreads due to centrifugal force.

[0067] On the other hand, in step S12, when it is determined that the target value T is less than the predetermined value, the supply amount of the processing liquid is determined to be an amount corresponding to a value larger than the product of the target value T and the area of the upper surface of the substrate W (step S15). For example, when the target value T is 200 μm and the diameter of the substrate W is 300 mm, the supply amount of the processing liquid is determined to be a value larger than 200 μm × (150 mm × 150 mm × π) ≈ 14.3 ml. After the supply amount of the processing liquid is determined in step S15, the rotation speed is determined to be such that the processing liquid on the upper surface of the substrate W is shaken off from the upper surface of the substrate W (step S16). Similar to step S14, the thickness of the liquid film may be measured by the film thickness measuring unit 5. The rotation speed at which the processing liquid is shaken off from the upper surface of the substrate W has been determined by experiments in advance.

[0068] FIG. 8 is a graph showing experimental data for creating a liquid film control recipe. In FIG. 8, the vertical axis represents the thickness m (μm) of the liquid film F1 measured by the film thickness measuring unit 5, and the horizontal axis represents time (sec). The film thickness measuring unit 5 continuously moves back and forth alternately between a position facing the center of the substrate W and a position facing the edge (periphery) of the substrate W. Due to such movement, the time on the horizontal axis periodically indicates the position between the center and the edge of the substrate W. An example is shown where it takes about 45 seconds to make a round trip between the center and the edge of the substrate W, and the positions facing the center of the substrate W and the edge of the substrate W are indicated by arrows.

[0069] In FIG. 8, with the supply amount of the processing liquid set to 30 ml, the rotation speed was accelerated from 0 rpm to 70 rpm in 1 second, then maintained at 70 rpm for 2 seconds, and further decelerated from 70 rpm to 0 rpm in 1 second (hereinafter referred to as "Condition A"). The results of measuring the thickness m up to 130 seconds are shown by the solid line. Also, with the supply amount of the processing liquid set to 30 ml, the rotation speed was accelerated from 0 rpm to 70 rpm in 1 second, then maintained at 70 rpm for 3 seconds, and further decelerated from 70 rpm to 0 rpm in 1 second (hereinafter referred to as "Condition B"). The results of measuring the thickness m up to 130 seconds are shown by the dotted line. Further, with the supply amount of the processing liquid set to 50 ml, the rotation speed was accelerated from 0 rpm to 70 rpm in 1 second, then maintained at 70 rpm for 2 seconds, and further decelerated from 70 rpm to 0 rpm in 1 second (hereinafter referred to as "Condition C"). The results of measuring the thickness m up to 130 seconds are shown by the dash-dotted line. Also, with the supply amount of the processing liquid set to 50 ml, the rotation speed was accelerated from 0 rpm to 70 rpm in 1 second, then maintained at 70 rpm for 3 seconds, and further decelerated from 70 rpm to 0 rpm in 1 second (hereinafter referred to as "Condition D"). The results of measuring the thickness m up to 130 seconds are shown by the double-dotted line.

[0070] As shown in FIG. 8, in both Condition A and Condition C where the supply amounts are different from each other, up to 130 seconds, the thickness m is maintained at around 200 μm. On the other hand, in both Condition B and Condition D where the supply amounts are different from each other, up to 130 seconds, the thickness m is maintained at around 250 μm. From these results, it can be seen that when the target value T is less than the predetermined value, the thickness m is affected by the time during which a predetermined rotation speed is maintained rather than the supply amount. For a high (thick) target value T, control is adopted to lengthen the time of maintaining the predetermined rotation speed, and for a low (thin) target value T, control is adopted to shorten the time of maintaining the predetermined rotation speed. Specifically, for example, with the predetermined rotation speed set to 70 rpm, when the target value T is 200 μm, a liquid film control recipe for rotating the substrate W while maintaining 70 rpm for 3 seconds is determined. Also, when the target value T is 250 μm, a liquid film control recipe for rotating the substrate W while maintaining 70 rpm for 2 seconds is determined.

[0071] As described above, when forming a relatively thin liquid film such that the target value T is less than a predetermined value, a relatively large amount of the processing liquid is supplied to shake off the processing liquid from the upper surface of the substrate W. In particular, since sulfuric acid is a liquid with a high viscosity, it has been difficult to control the thickness of the liquid film when using a liquid with a high sulfuric acid concentration. However, the thickness m of the liquid film is controlled as described above. By increasing the rotation speed as compared with the case where the target value T is greater than or equal to the predetermined value, a liquid film with a substantially uniform thickness m can be realized up to the peripheral portion of the substrate W. That is, when the target value T is greater than or equal to the predetermined value, the substrate W is rotated at a relatively low rotation speed such that the processing liquid is not shaken off, whereas when the target value T is less than the predetermined value, the substrate W is rotated at a relatively high rotation speed such that the processing liquid is shaken off. Further, by adjusting the time for maintaining the rotation speed, the thickness m of the liquid film F1 is controlled.

[0072] Next, the processing unit 130 forms a liquid film of the processing liquid on the upper surface of the substrate W (step S3: liquid film forming step). FIG. 9 is a diagram schematically showing an example of the state of the processing unit 130 in the liquid film processing step. As illustrated in FIG. 9, the nozzle moving mechanism 45 moves the nozzle 4 to the nozzle processing position, and the guard elevating mechanism 75 raises the guard 7 to the upper position. In the example of FIG. 9, both the guard 7A and the guard 7B are located at the upper position. Then, the substrate holding unit 3 rotates the substrate W around the rotation axis Q1, and the valve 42 opens. Thereby, the processing liquid is supplied from the discharge port 4a of the nozzle 4 toward the upper surface of the rotating substrate W. Here, concentrated sulfuric acid is supplied as the processing liquid. The rotation speed of the substrate W is the number of rotations determined in the liquid film control recipe determination step of step S2, and the supply amount of the processing liquid is the amount determined in the liquid film control recipe determination step of step S2.

[0073] The processing liquid adhering to the upper surface of the substrate W spreads on the upper surface of the substrate W. Thereby, a liquid film F1 of the processing liquid is formed on the upper surface of the substrate W. When the determined amount of the processing liquid is supplied, the valve 42 closes and the supply of the processing liquid stops, and the nozzle moving mechanism 45 moves the nozzle 4 to the nozzle standby position.

[0074] Next, the processing unit 130 performs plasma processing on the substrate W (step S4: plasma processing step). FIG. 10 is a flowchart showing a specific example of the plasma processing step, and FIG. 11 is a diagram schematically showing an example of the state of the processing unit 130 in the plasma processing step.

[0075] In the example of FIG. 10, first, the guard lifting mechanism 75 lowers the guard 7 to the lower position (step S21: guard movement step). The lower position here refers to a position where the upper end 711 of the inner peripheral surface of the outermost guard 7A is vertically below the upper surface of the substrate W held by the substrate holding unit 3. As a specific example of the lower position, a position where the upper end 711 of the guard 7A is vertically below the lower surface of the substrate W may be adopted, a position where the upper end 711 of the guard 7A is below the upper surface of the spin base 31 may be adopted, or the guard standby position may be adopted. Here, the guard standby position is adopted as the lower position. That is, the guard lifting mechanism 75 lowers the guards 7A and 7B to the guard standby position.

[0076] Next, the power supply 16 outputs a plasma voltage to the plasma reactor 1 (step S22: lighting step). Thereby, plasma is generated around the plasma reactor 1. Note that the lighting step may be executed before the guard movement step.

[0077] Next, the plasma lifting mechanism 15 lowers the plasma reactor 1 from the plasma standby position to the plasma processing position (step S23: plasma movement step). In a state where the plasma reactor 1 is located at the plasma processing position, the plasma reactor 1 can irradiate the substrate W with plasma (step S24: plasma irradiation step). In other words, the plasma processing position is a position close to the substrate W to such an extent that the substrate W can be irradiated with plasma.

[0078] FIG. 11 shows the state of the processing unit 130 in the plasma irradiation step. In the example of FIG. 11, the plasma reactor 1 is located at the plasma processing position, and plasma is irradiated onto the liquid film F1 on the upper surface of the substrate W to supply active species to the liquid film F1. Thereby, the processing performance of the processing liquid is improved, and the processing liquid acts on the substrate W with high processing performance. More specifically, oxygen radicals react with sulfuric acid to generate peroxy acid, and the peroxy acid removes the resist on the substrate W.

[0079] In this plasma irradiation step, the substrate holding unit 3 rotates the substrate W (step S25: rotation step). FIG. 12 is a schematic view showing the state of the substrate W when the plasma P is irradiated. When the plasma P is irradiated, the temperature of the substrate W rises. As a result, a dent may occur in the substrate W upward. As shown in FIG. 12, when a dent occurs in the substrate W, the liquid film F1 that was once uniformly formed in the plane moves toward the dent due to gravity. As a result, the thickness of the liquid film F1 becomes thicker at the center than at the edge of the substrate W, and becomes non-uniform in the plane.

[0080] Rotating the substrate W contributes to the uniformization of the thickness m of the liquid film F1. FIG. 13 is a graph showing the relationship between the thickness m of the liquid film F1 and time. In FIG. 13, the vertical axis represents the thickness m (μm) of the liquid film F1, and the horizontal axis represents time (sec). Also, similar to FIG. 8, the film thickness measurement unit 5 continues to alternately move between the position facing the center of the substrate W and the position facing the edge (periphery) of the substrate W. In FIG. 13 as well, an example is shown where it takes about 45 seconds to make a round trip between the center and the edge of the substrate W, and the positions facing the center of the substrate W and the edge of the substrate W are indicated by arrows.

[0081] In FIG. 13, the case where the dent amount t in FIG. 5 is 1.3 μm is shown. Further, in FIG. 13, after making the liquid film F1 uniform in the plane respectively, the results of measuring the thickness m up to 130 seconds under the condition of maintaining different rotational speeds are shown. The result measured under the condition of maintaining the rotational speed at 0 rpm (hereinafter referred to as "Condition 1") is shown by a solid line, the result measured under the condition of maintaining the rotational speed at 6 rpm (hereinafter referred to as "Condition 2") is shown by a dotted line, the result measured under the condition of maintaining the rotational speed at 9 rpm (hereinafter referred to as "Condition 3") is shown by a dashed-dotted line, the result measured under the condition of maintaining the rotational speed at 10 rpm (hereinafter referred to as "Condition 4") is shown by a double-dashed-dotted line, the result measured under the condition of maintaining the rotational speed at 11 rpm (hereinafter referred to as "Condition 5") is shown by a thick solid line, and the result measured under the condition of maintaining the rotational speed at 12 rpm (hereinafter referred to as "Condition 6") is shown by a thick dotted line.

[0082] As shown in FIG. 13, in the case of Condition 1, after 100 seconds, the thickness m of the liquid film F1 in the central part has reached 450 μm, while the thickness m of the liquid film F1 in the edge part (peripheral part) is 100 μm or less. Further, in the case of Condition 2, after 100 seconds, the thickness m of the liquid film F1 in the central part has become 300 μm, while the thickness m of the liquid film F1 in the edge part (peripheral part) is about 150 μm. Further, in the case of Condition 3, after 100 seconds, the thickness m of the liquid film F1 in the central part has become 230 μm, while the thickness m of the liquid film F1 in the edge part (peripheral part) is about 150 μm. From the above, in the cases of Conditions 1 to 3, it can be seen that the thickness m of the liquid film F1 becomes non-uniform in the plane over time. On the other hand, in the cases of Conditions 4 to 5, in both cases after 100 seconds, the thickness m of the liquid film F1 is maintained substantially uniformly in the plane. However, in the case of Condition 6, the thickness of the liquid film F1 in the central part has decreased from about 200 μm to about 175 μm over time. And it can be seen that due to the influence of the increase in centrifugal force caused by the increase in the rotational speed, the liquid film in the central part gradually moves towards the edge part (peripheral part). From the above, it can be seen that there is an appropriate rotational speed to maintain the liquid film thickness uniformly in the plane.

[0083] When the substrate holding unit 3 rotates the substrate W so as to maintain the thickness m of the liquid film F1 uniformly, the active species act on the substrate W more uniformly. Therefore, the uniformity of the process for the substrate W can be improved. The correlation between the amount of indentation t and the rotation speed of the substrate W may be stored in advance in the control unit 90. The indentation measurement unit 36 may measure the amount of indentation t over time and rotate the substrate W at a rotation speed that increases as the amount of indentation t increases based on the above-described correlation. Further, based on the above-described correlation, the substrate W may be rotated at a higher rotation speed as the amount of indentation t is larger.

[0084] Then, when the resist on the substrate W is removed, the plasma lifting mechanism 15 raises the plasma reactor 1 to the plasma standby position, and the power supply 16 stops the output of the voltage (step S26). Also, before and after step S26, the substrate holding unit 3 stops the rotation of the substrate W (step S27).

[0085] Next, the processing unit 130 performs a rinse process on the upper surface of the substrate W (step S5: rinse step). Specifically, the processing unit 130 supplies a rinse liquid from the nozzle 4 to the upper surface of the rotating substrate W and replaces the processing liquid on the upper surface of the substrate W with the rinse liquid.

[0086] Next, the processing unit 130 performs a drying process on the substrate W (step S6: drying step). For example, the substrate W is dried (so-called spin drying) by rotating the substrate W at a rotation speed higher than that in the plasma processing step. Next, the main transfer robot 120 carries out the processed substrate W from the processing unit 130.

[0087] <Others> In the above-described embodiment, the case where the diameter of the substrate W is 300 mm has been described, but the present invention is not limited to the case where the diameter of the substrate W is 300 mm. Substrates W of other sizes may be adopted.

[0088] In the above-described embodiment, the substrate W rotates based on the correlation between the amount of depression t and the rotation speed in the plasma treatment step, but the present invention is not limited to this configuration. In recent years, since the flexibility of the substrate W has been improved, when the substrate holding unit 3 holds the peripheral edge of the substrate W, the central portion may be recessed due to the weight of the substrate W. In such a case, even before the plasma treatment step, the substrate holding unit 3 rotates the substrate W based on the correlation between the amount of depression t and the rotation speed. Thereby, the thickness m of the liquid film F1 is maintained substantially uniformly in the plane.

[0089] In the above-described embodiment, in the liquid film forming step of step S3, the treatment liquid is supplied in parallel with the rotation of the substrate W, but the present invention is not limited to this. After the treatment liquid is supplied, the substrate W may be rotated.

[0090] The embodiments disclosed this time are illustrative and are not limited only to the above-described content. The scope of the present invention is indicated by the scope of the claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of the claims be included.

Explanation of Reference Numerals

[0091] 1 Plasma reactor 3 Substrate holding unit 4 Nozzle 4a Discharge port 5 Film thickness measurement unit 7 Guard 15 Plasma lifting mechanism 16 Power supply 31 Spin base 32 Chuck pin 33 Rotation mechanism 34 Shaft 35 Motor 36 Depression measurement unit 41 Supply pipe 42 Valve 44 Treatment liquid supply source 45 Nozzle movement mechanism 51 Film thickness measurement unit movement mechanism 71 Cylindrical portion 72 Inclined portion 73 Upper end 75 Guard lifting mechanism 76 Cup 77 Recovery pipe 80 Chamber 82 Exhaust part 83 Cylindrical member 84 Exhaust pipe 90 Control unit 91 Data processing unit 92 Memory medium 93 Bus 100 Substrate processing system 101 Load port 110 Indexer robot 120 Main transfer robot 130 Processing unit 711 Upper end F1 Liquid film T Target value W Substrate m Thickness t Dent amount P Plasma

Claims

1. In a substrate processing method for forming a liquid film of concentrated sulfuric acid of 90 wt% or more on the upper surface of a substrate having an upper surface held substantially horizontally, a first step of supplying the concentrated sulfuric acid to the upper surface; a second step of rotating the substrate at a rotational speed such that the concentrated sulfuric acid on the upper surface is not shaken off from the upper surface, in parallel with the first step or after completion of the first step, when the target value of the thickness of the liquid film is equal to or greater than a predetermined value; a third step of rotating the substrate at a rotational speed such that the concentrated sulfuric acid is shaken off from the upper surface, in parallel with the first step or after completion of the first step, when the target value is less than the predetermined value; A substrate processing method comprising:

2. In the first step, when the target value is equal to or greater than the predetermined value, supplying an amount of the concentrated sulfuric acid corresponding to the product of the target value and the area of the upper surface to the upper surface; when the target value is less than the predetermined value, supplying an amount of the concentrated sulfuric acid corresponding to a value greater than the product to the upper surface, the substrate processing method according to claim 1.

3. The substrate processing method according to claim 1 or claim 2, wherein the predetermined value is between 300 μm and 400 μm.

4. A fourth step of rotating the substrate at a higher rotational speed as the amount of recess on the upper surface at the center of the upper surface with respect to the periphery of the upper surface is larger, after the second step or after the third step The substrate processing method according to any one of claims 1 to 3, further comprising:

5. A fifth step of irradiating the liquid film obtained by the second step or the third step with plasma, after the second step or after the third step The substrate processing method according to any one of claims 1 to 3, further comprising:

6. In the fifth step, measuring the amount of recess on the upper surface at the center of the upper surface with respect to the periphery of the upper surface over time; rotating the substrate at a rotational speed that increases as the amount of recess increases, the substrate processing method according to claim 5.

7. In a substrate processing apparatus for forming a liquid film of concentrated sulfuric acid of 90 wt% or more on the upper surface of a substrate having an upper surface held substantially horizontally, a holding unit that holds the substrate with the upper surface substantially horizontal; a supply unit that supplies the concentrated sulfuric acid to the upper surface; a rotating unit that rotates the substrate; a control unit, and the control unit is When the target value of the thickness of the liquid film is greater than or equal to a predetermined value, when supplying the concentrated sulfuric acid to the upper surface or after supplying the concentrated sulfuric acid to the upper surface, the rotating unit is controlled to rotate the substrate at a rotational speed such that the concentrated sulfuric acid is not shaken off from the upper surface. When the target value is less than the predetermined value, when supplying the concentrated sulfuric acid to the upper surface or after supplying the concentrated sulfuric acid to the upper surface, the rotating unit is controlled to rotate the substrate at a rotational speed such that the concentrated sulfuric acid is shaken off from the upper surface. A substrate processing apparatus. **Claim 8** When the target value is greater than or equal to the predetermined value, the control unit controls the supply unit to supply the upper surface with an amount of the concentrated sulfuric acid corresponding to the product of the target value and the area of the upper surface. When the target value is less than the predetermined value, the control unit controls the supply unit to supply the upper surface with an amount of the concentrated sulfuric acid corresponding to a value greater than the product. The substrate processing apparatus according to claim 7. **Claim 9** The predetermined value is between 300 μm and 400 μm. The substrate processing apparatus according to claim 7 or claim 8. **Claim 10** The substrate processing apparatus according to any one of claims 7 to 9, further comprising a plasma irradiation unit that irradiates the liquid film with plasma. **Claim 11** The control unit controls the rotating unit to rotate the substrate at a higher rotational speed as the amount of the depression of the upper surface at the center of the upper surface with respect to the periphery of the upper surface is larger. The substrate processing apparatus according to claim 10. **Claim 12** A depression measurement unit that measures the amount of depression of the upper surface at the center of the upper surface with respect to the periphery of the upper surface The substrate processing apparatus according to any one of claims 7 to 11, further comprising.

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