Substrate processing apparatus and substrate processing method

Abstract

To provide a technique that can reduce processing defects that may be caused by introducing a processing fluid at a high flow rate into a processing chamber, and can be executed in a short time.SOLUTION: A substrate processing method according to the present invention includes steps of: accommodating a substrate whose upper surface is covered with a liquid film in an internal space of a processing chamber in a state where the substrate is placed on a plate-like support member in a horizontal posture; filling the internal space with a processing fluid in a supercritical state; and discharging the processing fluid from the internal space. Supply of the processing fluid is started from a first discharge port that ejects the processing fluid in a horizontal direction toward a space between a bottom surface of a chamber wall surface and a lower surface of the support member. In addition, after an internal pressure of the internal space exceeds a critical pressure, supply of a pressurized processing fluid into the internal space is started from a second discharge port that ejects the processing fluid in the horizontal direction toward a space between a ceiling surface of the chamber wall surface and the upper surface of the substrate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a technology for processing a substrate with a processing fluid in a supercritical state within a processing chamber, and particularly relates to a supply sequence of the processing fluid to the processing chamber.

Background Art

[0002] Processing steps for various substrates such as semiconductor substrates and glass substrates for display devices include processing the surface of a substrate with various processing fluids. Processing using liquids such as chemical solutions and rinsing solutions as processing fluids has been widely performed conventionally, but in recent years, processing using supercritical fluids has also been put into practical use. Particularly, in processing a substrate on which a fine pattern is formed, a supercritical fluid, which has lower surface tension than a liquid, can penetrate deep into the gaps between patterns, enabling efficient processing, and can reduce the risk of pattern collapse caused by surface tension during drying.

[0003] For example, Patent Document 1, which relates to an application filed by the applicant of the present application, discloses that a substrate having a liquid film formed on the upper surface thereof is housed in a processing chamber, which is a high-pressure chamber, in a state of being placed on a flat plate-shaped support member, and the processing fluid is introduced from the side of the substrate to each of the upper surface side of the substrate and the lower surface side of the support member. Further, on each of the upper surface side of the substrate and the lower surface side of the support member, the processing fluid is discharged from the side opposite to the direction in which the processing fluid is introduced when viewed from the substrate. As a result, laminar flows of the processing fluid are formed respectively above the substrate and below the support member, the liquid covering the substrate is replaced by the processing fluid and discharged together with the processing fluid, and finally the substrate is brought into a dry state.

[0004] On the other hand, Patent Document 2 describes a technology for improving the processing effect by supplying a processing fluid to the lower side of a substrate to increase the pressure inside the processing container to a predetermined pressure, and then causing the processing fluid to flow along the upper surface side of the substrate.

Prior Art Literature

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-036123 [Patent Document 2] Japanese Patent Publication No. 2023-017577 [Overview of the project] [Problems that the invention aims to solve]

[0006] When introducing a high-pressure processing fluid into a processing chamber containing a substrate covered with a liquid film, particularly in the initial stages of introduction, the high-velocity processing fluid can cause partial loss of the liquid constituting the film. If this exposes the substrate surface, the risk of processing defects such as pattern collapse increases. Patent Document 1 does not address this problem.

[0007] Furthermore, the technology described in Patent Document 2 addresses this problem by supplying the processing fluid only from the bottom of the substrate until sufficient high pressure is reached inside the processing container. However, with such a configuration, the time required to raise the pressure to a predetermined level becomes longer. If the amount of processing fluid supplied is increased to avoid this, the flow velocity of the processing fluid will increase even further, which can lead to processing failures.

[0008] Thus, in technologies that process substrates by forming a laminar flow of processing fluid around the substrate, no technology has yet been proposed that effectively suppresses processing defects such as pattern collapse caused by the loss of the liquid film on the substrate surface due to the introduction of the processing fluid. In this sense, it can be said that there is still room for improvement in conventional technologies.

[0009] This invention has been made in view of the above problems, and aims to provide a technology that can reduce processing defects that may occur when a high-velocity processing fluid is introduced in a processing chamber for processing a substrate with a supercritical processing fluid, and that can be implemented in a short amount of time. [Means for solving the problem]

[0010] One aspect of this invention is a substrate processing method for processing a substrate with a processing fluid in a supercritical state, comprising: a first step of housing the substrate, whose upper surface is covered with a liquid film, in the internal space of a processing chamber while it is placed horizontally on a flat support member; a second step of filling the internal space with the processing fluid in a supercritical state; and a third step of discharging the processing fluid from the internal space.

[0011] Here, among the wall surfaces of the processing chamber that constitute the internal space, the side wall surface has a gap between the bottom surface and the lower surface of the support member. A slit-shaped opening extends horizontally into the gap formed therein, and is formed in the gap A first discharge port that discharges the processing fluid horizontally into space, and the space between the ceiling surface and the upper surface of the substrate on the wall surface A slit-shaped opening extends horizontally into the gap formed therein, and is formed in the gap A second discharge port is provided for discharging the processing fluid horizontally into space. The processed fluid discharged from the first discharge port and passing between the bottom surface and the lower surface of the support member is discharged from a first discharge channel provided horizontally within the internal space on the side opposite to the side wall surface, sandwiching the support member. The processed fluid discharged from the second discharge port and passing between the ceiling surface and the upper surface of the substrate is discharged from a second discharge channel provided horizontally within the internal space on the side opposite to the side wall surface, sandwiching the support member.

[0012] Then, in the second step, the pressurized processing fluid is supplied from the first discharge port to the internal space to increase the pressure of the internal space, and after the internal pressure of the internal space exceeds the critical pressure of the processing fluid, in addition to the supply from the first discharge port, the supply of the pressurized processing fluid from the second discharge port to the internal space is started.

[0013] Another aspect of this invention is a substrate processing apparatus for processing a substrate with a supercritical processing fluid, comprising: a flat plate-shaped support member on which the substrate can be placed; a processing chamber having an internal space capable of housing the support member together with the substrate in a horizontal position; a fluid supply unit for supplying the processing fluid to the internal space; a fluid discharge unit for discharging the processing fluid from the internal space; and a control unit for controlling the fluid supply unit.

[0014] Here, among the wall surfaces of the processing chamber that constitute the internal space, the side wall surface has a gap between the bottom surface and the lower surface of the support member. A slit-shaped opening extends horizontally into the gap formed therein, and is formed in the gap A first discharge port that discharges the processing fluid horizontally into space, and the space between the ceiling surface and the upper surface of the substrate on the wall surface A slit-shaped opening extends horizontally into the gap formed therein, and is formed in the gap A second discharge port is provided for discharging the processing fluid horizontally into space. The internal space is provided with a first discharge channel that discharges the processing fluid from the side opposite the first discharge port, sandwiching the substrate horizontally, and a second discharge channel that discharges the processing fluid from the side opposite the second discharge port, sandwiching the substrate horizontally, and the fluid discharge section discharges the processing fluid from the internal space via the first discharge channel and the second discharge channel.

[0015] Then, when the support member on which the substrate is placed is housed in the internal space, the control unit controls the fluid supply unit to start supplying the processing fluid from the first discharge port to the internal space, thereby increasing the pressure of the internal space. After the internal pressure of the internal space exceeds the critical pressure of the processing fluid, the control unit starts supplying the processing fluid from the second discharge port to the internal space in addition to the supply from the first discharge port.

[0016] In this configuration, during the initial stage of introducing the processing fluid into the processing chamber, the processing fluid is supplied to the space below the support member. Then, after the internal pressure of the processing chamber exceeds the critical pressure of the processing fluid, the supply of the processing fluid to the space above the substrate begins. At this point, the internal space of the processing chamber is filled with processing fluid at a pressure above the critical pressure, so the problem of the liquid film on the substrate being blown away by the processing fluid supplied along the top surface of the substrate is avoided. Therefore, it is possible to effectively prevent the loss of the liquid film, the exposure of the substrate surface, and the occurrence of processing defects.

[0017] In the technology of processing substrates with a supercritical processing fluid, the internal pressure of the processing chamber is ultimately raised to a pressure well above the critical pressure. In this invention, it is possible to further increase the pressure not only by supplying the processing fluid from below the substrate, but also by supplying it from above the substrate, thus shortening the time required to raise the internal space to the pressure necessary for processing. [Effects of the Invention]

[0018] As described above, in this invention, the processing fluid is first supplied to the space below the substrate, and only after the internal pressure of the processing chamber exceeds the critical pressure is the processing fluid supplied to the space above the substrate. Therefore, the time required for the internal pressure to reach the desired pressure is shortened, and processing defects caused by the spraying of the processing fluid are reduced. [Brief explanation of the drawing]

[0019] [Figure 1] It is a diagram showing a schematic configuration of an example of the substrate processing apparatus according to the present invention. [Figure 2] It is a flowchart showing an outline of processing executed by this substrate processing apparatus. [Figure 3] It is a timing chart showing state changes of each part of the apparatus in this processing. [Figure 4] It is a timing chart showing a first modification of the supercritical drying process. [Figure 5] It is a timing chart showing a second modification of the supercritical drying process. [Figure 6] It is a timing chart showing a third modification of the supercritical drying process.

Mode for Carrying Out the Invention

[0020] FIG. 1 is a diagram showing a schematic configuration of an example of the substrate processing apparatus according to the present invention. This substrate processing apparatus 1 is an apparatus for treating the surface of various substrates such as semiconductor substrates with a supercritical fluid. The substrate processing apparatus 1 has a configuration to which the method for determining completion of replacement and the substrate processing method according to the present invention can be suitably applied. In order to uniformly indicate directions in the following drawings, an XYZ orthogonal coordinate system is set as shown in FIG. 1. Here, the XY plane is a horizontal plane, and the Z direction represents the vertical direction. More specifically, the (-Z) direction represents vertically downward.

[0021] Here, as the "substrate" in the present embodiment, various substrates including semiconductor wafers, glass substrates for photomasks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FED (Field Emission Display), substrates for optical disks, substrates for magnetic disks, and substrates for magneto-optical disks are applicable. In the following description, a substrate processing apparatus used for processing semiconductor wafers will be mainly taken as an example and described with reference to the drawings, but the present invention is also similarly applicable to the processing of various substrates exemplified above.

[0022] The substrate processing apparatus 1 comprises a processing unit 10, a supply unit 50, and a control unit 90. The processing unit 10 is the main component that performs the supercritical drying process, and the supply unit 50 supplies the chemical substances and power necessary for the process to the processing unit 10.

[0023] The control unit 90 controls each part of these devices to perform predetermined processing. For this purpose, the control unit 90 is equipped with a CPU 91 that executes various control programs, a memory 92 that temporarily stores processing data, a storage 93 that stores the control programs executed by the CPU 91, and an interface 94 for exchanging information with the user and external devices. The operation of the devices, which will be described later, is achieved when the CPU 91 executes a control program that has been written to the storage 93 in advance, causing each part of the devices to perform predetermined operations.

[0024] The processing unit 10 includes a processing chamber 100. The processing chamber 100 comprises a first member 11, a second member 12, and a third member 13, each formed from a metal block. The first member 11 and the second member 12 are joined vertically by a connecting member (not shown), and the third member 13 is joined to its (+Y) side surface by a connecting member (not shown), forming a processing chamber 100 with a hollow interior. This hollow interior space serves as the processing space SP where processing is performed on the substrate S. The substrate S to be processed is brought into the processing space SP for processing. A slit-shaped opening 101 extending elongated in the X direction is formed on the (-Y) side surface of the processing chamber 100, and the processing space SP and the external space are in communication through the opening 101.

[0025] A lid member 14 is provided on the (-Y) side of the processing chamber 100 to close the opening 101. A flat support tray 15 is mounted horizontally on the (+Y) side of the lid member 14, and the upper surface of the support tray 15 is a support surface on which a substrate S can be placed. More specifically, the support tray 15 has a structure in which a recess 152 is formed on a substantially flat upper surface 151 that is slightly larger than the planar size of the substrate S. By accommodating the substrate S in this recess 152, the substrate S is held in a predetermined position on the support tray 15. The substrate S is held with the surface to be processed (hereinafter sometimes simply referred to as the "substrate surface") Sa facing upward. At this time, it is preferable that the upper surface 151 of the support tray 15 and the substrate surface Sa are on the same or substantially the same plane.

[0026] The lid member 14 is supported by a support mechanism (not shown) so as to be able to move horizontally in the Y direction. The lid member 14 is also able to move forward and backward relative to the processing chamber 100 by a forward / backward mechanism 53 provided on the supply unit 50. Specifically, the forward / backward mechanism 53 has a linear motion mechanism such as a linear motor, linear guide, ball screw mechanism, solenoid, or air cylinder, and such a linear motion mechanism moves the lid member 14 in the Y direction. The forward / backward mechanism 53 operates in response to control commands from the control unit 90.

[0027] When the lid member 14 moves in the (-Y) direction, the support tray 15 is pulled out of the processing space SP through the opening 101, allowing access to the support tray 15 from the outside. That is, it becomes possible to place a substrate S on the support tray 15 and to remove a substrate S that is placed on the support tray 15. On the other hand, when the lid member 14 moves in the (+Y) direction, the support tray 15 is housed inside the processing space SP. If a substrate S is placed on the support tray 15, the substrate S is transported into the processing space SP together with the support tray 15.

[0028] In supercritical drying, which primarily aims to dry a substrate while preventing pattern collapse due to the surface tension of the liquid, the substrate S is brought in with its surface Sa covered by a liquid film to prevent the surface Sa from being exposed and causing pattern collapse. Suitable liquids for the liquid film include organic solvents with relatively low surface tension, such as isopropyl alcohol (IPA) and acetone.

[0029] The lid member 14 moves in the (+Y) direction and closes the opening 101, thereby sealing the processing space SP. A sealing member 16 is provided between the (+Y) side surface of the lid member 14 and the (-Y) side surface of the processing chamber 100, maintaining the airtight state of the processing space SP. As the sealing member 16, an annular one made of an elastic resin material, such as rubber, can be used. In addition, the lid member 14 is fixed to the processing chamber 100 by a locking mechanism (not shown). With the processing space SP thus airtight, processing of the substrate S is performed within the processing space SP.

[0030] In this embodiment, a fluid of a substance usable for supercritical processing, such as carbon dioxide, is supplied to the processing unit 10 from a fluid supply unit 57 provided in the supply unit 50, in the form of a gas, liquid, or supercritical state. Carbon dioxide is a suitable chemical substance for supercritical drying processing because it becomes supercritical at relatively low temperatures and pressures, and also has the property of readily dissolving organic solvents that are frequently used in substrate processing. The critical point at which carbon dioxide becomes supercritical is a pressure (critical pressure) of 7.38 MPa and a temperature (critical temperature) of 31.1°C.

[0031] More specifically, the fluid supply unit 57 outputs a supercritical fluid, or a fluid supplied in gaseous or liquid form that subsequently becomes supercritical when given a predetermined temperature and pressure, as a processing fluid for processing the substrate S. For example, carbon dioxide heated above its critical temperature is output under pressure. The processing fluid is supplied to input ports 102 and 103, which are arranged vertically (Z direction) on the (+Y) side of the processing chamber 100 and receive the processing fluid supplied to the processing chamber 100 from the outside.

[0032] Specifically, the fluid supply unit 57 and the input port 102 are connected by a pipe 571, and a flow meter 573 and a valve 574 are inserted into the pipe 571. When the valve 574 is opened in response to a control command from the control unit 90, the processed fluid is sent from the fluid supply unit 57 to the processing chamber 100 via the input port 102. The flow meter 573 measures the flow rate of the processed fluid passing through the pipe 571 and transmits the measurement result to the control unit 90.

[0033] Similarly, the fluid supply unit 57 and the input port 103 are connected by piping 572, which contains a flow meter 575 and a valve 576. When the valve 576 is opened in response to a control command from the control unit 90, the processed fluid is sent from the fluid supply unit 57 to the processing chamber 100 via the input port 103. The flow meter 575 measures the flow rate of the processed fluid passing through piping 572 and transmits the measurement result to the control unit 90.

[0034] The fluid channel 17 from input ports 102 and 103 to the processing space SP functions as an introduction channel for introducing the processing fluid supplied from the fluid supply unit 57 into the processing space SP. Specifically, a channel 171 is connected to input port 102, which is located above input port 103. A buffer space 172 is provided at the end of channel 171 opposite to input port 102, which is formed so that the cross-sectional area of ​​the channel expands rapidly.

[0035] A flow path 173 is further provided to connect the buffer space 172 and the processing space SP. The flow path 173 has a wide cross-sectional shape that is narrow in the vertical direction (Z direction) and long in the horizontal direction (X direction), and its cross-sectional shape is substantially constant in the direction of flow of the processing fluid. The end of the flow path 171 opposite to the buffer space 172 is an outlet 174 that opens facing the processing space SP, and the processing fluid is introduced into the processing space SP from this outlet 174.

[0036] Preferably, the height of the flow path 173 is equal to the distance between the ceiling surface 110a of the processing space SP and the substrate surface Sa when the support tray 15 is housed in the processing space SP. The discharge port 174 opens facing the gap between the ceiling surface 110a of the processing space SP and the upper surface 151 of the support tray 15. For example, the ceiling surface of the flow path 173 and the ceiling surface 110a of the processing space SP can be made to be on the same plane. In this way, the discharge port 174 opens in a horizontally elongated slit shape facing the processing space SP.

[0037] Furthermore, the flow path 171, buffer space 172, and flow path 173, which constitute the introduction flow path from the input port 102 to the discharge port 174, together form an "upper introduction flow path 17a" that supplies the processing fluid to the space within the processing space SP that is sandwiched between the ceiling surface 110a, the upper surface 151 of the support tray 15, and the substrate surface Sa.

[0038] Similarly, a fluid channel 17 (lower introduction channel 17b) for the processing fluid is formed below the support tray 15. Specifically, a channel 175 is connected to an input port 103 located below the input port 102. At the end of the channel 175 opposite to the input port 103, a buffer space 176 is provided, which is formed so that the cross-sectional area of ​​the channel expands rapidly.

[0039] The buffer space 176 and the processing space SP are connected via a flow path 177. The flow path 177 has a cross-sectional shape that is narrow in the vertical direction (Z direction) and wide in the horizontal direction (X direction), and its cross-sectional shape is substantially constant in the direction of flow of the processing fluid. The end of the flow path 177 opposite to the buffer space 176 is an outlet 178 that opens facing the processing space SP, and the processing fluid is introduced into the processing space SP from this outlet 178.

[0040] Preferably, the height of the flow path 177 is equal to the distance between the bottom surface 110b of the processing space SP and the bottom surface of the support tray 15. The discharge port 178 opens facing the gap between the bottom surface 110b of the processing space SP and the bottom surface of the support tray 15. For example, the bottom surface 110b of the flow path 177 and the bottom surface of the processing space SP can be made to be on the same plane. In other words, the discharge port 178 opens in a horizontally elongated slit shape facing the processing space SP. The flow path 175, buffer space 176, and flow path 177 that constitute the introduction flow path from the input port 103 to the discharge port 178 constitute the "lower introduction flow path 17b" that supplies the processing fluid to the space sandwiched between the bottom surface 110b of the processing space SP and the bottom surface of the support tray 15.

[0041] In the Z direction, it is desirable that the positions of the flow path 171 and the flow path 173 are different. When they are at the same height, some of the processed fluid that flows from flow path 171 into buffer space 172 will continue straight into flow path 173. In this case, in the width direction of the flow path perpendicular to the flow direction, i.e., in the X direction, there is a risk that differences will occur in the flow rate and velocity of the processed fluid flowing into flow path 173 between the position corresponding to flow path 171 and other positions. This will cause non-uniformity in the X direction of the flow of processed fluid that flows from flow path 173 into processing space SP, leading to turbulence.

[0042] By arranging flow paths 171 and 173 at different angles in the Z direction, the straight-line flow of the processing fluid from flow path 171 to flow path 173 is eliminated, making it possible to introduce the processing fluid into the processing space SP as a uniform laminar flow in the width direction. The same concept can be applied to the positional relationship between flow path 175 and flow path 177.

[0043] The processing fluid introduced from the introduction channel 17 configured in this way flows along the upper and lower surfaces of the support tray 15 within the processing space SP, and is discharged outside the processing container via the discharge channel 18 configured as follows. On the (-Y) side of the substrate S, the ceiling surface of the processing space SP and the upper surface 151 of the support tray 15 are both horizontal planes, and they face each other in parallel while maintaining a certain gap. This gap functions as the upstream section 181 of the discharge channel 18, which guides the processing fluid that has flowed along the upper surface 151 of the support tray 15 and the surface Sa of the substrate S to the fluid discharge section 55. This upstream section 181 has a wide cross-sectional shape that is narrow in the vertical direction (Z direction) and long in the horizontal direction (X direction).

[0044] The end of the upstream section 181 opposite to the processing space SP is connected to the buffer space 182. The buffer space 182 is a space enclosed by the processing chamber 100, the lid member 14, and the sealing member 16. The width of the buffer space 182 in the X direction is equal to or greater than the width of the upstream section 181, and the height of the buffer space 182 in the Z direction is greater than the height of the upstream section 181. Therefore, the buffer space 182 has a larger flow path cross-sectional area than the upstream section 181.

[0045] The downstream portion 183 of the upper discharge channel is connected to the upper part of the buffer space 182. The downstream portion 183 is a through-hole provided through the first member 11, which is the upper block constituting the processing chamber 100. Its upper end constitutes an output port 104 that opens to the upper surface of the processing chamber 100, and its lower end opens facing the buffer space 182.

[0046] Similarly, the bottom surface of the processing space SP and the underside of the support tray 15 are both horizontal planes, and they face each other parallel to maintain a certain gap. This gap functions as the upstream section 185 of the discharge channel 18, which guides the processing fluid flowing along the underside of the support tray 15 to the fluid discharge section 55. Furthermore, the upstream section 185 on the underside of the support tray 15 is connected to the downstream section 187 via a buffer space 186, similar to the upper side of the support tray 15.

[0047] In the processing space SP, the processed fluid that flows over the support tray 15 is sent to the output port 104 via the upstream section 181, buffer space 182, and downstream section 183 of the discharge channel 18, which constitute the upper discharge channel. The output port 104 is connected to the fluid discharge section 55 by piping 551, and a flow meter 552, a valve 553, and a pressure gauge 554 are interposed in the middle of the piping 551. In order to reduce detection errors due to pressure loss in the flow path, it is desirable that the flow meter 552 and the pressure gauge 554 be placed as far upstream as possible in the discharge channel.

[0048] Similarly, the processed fluid that flows below the support tray 15 in the processing space SP is sent to the output port 105 via the upstream section 185, buffer space 186, and downstream section 187 that constitute the lower discharge channel of the discharge channel 18. The output port 105 is connected to the fluid discharge section 55 by piping 555, and a flow meter 556 and a valve 557 are interposed in the middle of the piping 555. A pressure gauge may also be connected to piping 555, similar to piping 551.

[0049] Valves 553 and 557 are controlled by the control unit 90. When valves 553 and 557 open in response to a control command from the control unit 90, the processing fluid in the processing space SP is recovered to the fluid discharge section 55 via the pipes 551 and 555.

[0050] Thus, in this substrate processing apparatus 1, the upstream section 181, buffer space 182, and downstream section 183 of the discharge channel 18, along with the piping 551, together constitute an "upper discharge channel 18a" that discharges the processing fluid passing over the upper surface of the substrate S within the processing space SP. Furthermore, the upstream section 185, buffer space 186, and downstream section 187 of the discharge channel 18, along with the piping 555, together constitute a "lower discharge channel 18b" that discharges the processing fluid passing over the lower surface of the support tray 15 within the processing space SP.

[0051] Furthermore, flow meters 552 and 556 for detecting the fluid flow rate are provided in the upper discharge channel 18a and the lower discharge channel 18b, respectively. Various principles of flow meters capable of detecting the fluid flow rate in the flow path can be applied as flow meters 552 and 556, for example, a mass flow meter, or more specifically, a Coriolis flow meter can be used.

[0052] Figure 2 is a flowchart outlining the process performed by this substrate processing apparatus. Figure 3 is a timing chart showing the state changes of each part of the apparatus during this process. This substrate processing apparatus 1 performs supercritical drying, that is, a process of drying the substrate S that has been cleaned with a cleaning solution in the preceding process. Specifically, it is as follows: The substrate S to be processed is cleaned with a cleaning solution in a preceding process performed by other substrate processing apparatuses that constitute the substrate processing system. After that, with a liquid film formed on its surface, such as isopropyl alcohol (IPA), the substrate S is transported to the substrate processing apparatus 1.

[0053] For example, if a fine pattern is formed on the surface of a substrate S, the surface tension of any residual liquid adhering to the substrate S may cause the pattern to collapse. Also, incomplete drying may leave watermarks on the surface of the substrate S. Furthermore, exposure of the substrate S surface to the outside air may cause oxidation or other deterioration. To prevent these problems, the substrate S surface (the pattern-forming surface) may be transported covered with a liquid or solid surface layer.

[0054] For example, if the cleaning solution is mainly water, the substrate is transported with a liquid film formed using an organic solvent such as IPA or acetone, which has a lower surface tension and is less corrosive to the substrate. In other words, the substrate S is transported to the substrate processing apparatus 1 supported in a horizontal position with a liquid film formed on its upper surface.

[0055] The substrate S, transported by a transport device (not shown), is placed in the processing chamber 100 (step S101). Specifically, the substrate S is transported with the pattern-forming surface facing upwards, and with this surface covered by a thin liquid film. The substrate S is transferred to the support tray 15 via a lift pin (not shown). That is, with the lid member 14 moving to the (-Y) side and the support tray 15 being pulled out, the lift pin advances above the upper surface 151 of the support tray 15 through a through hole (not shown) provided in the support tray 15. The transport device transfers the substrate S to the lift pin, and as the lift pin descends, the substrate S is placed on the support tray 15. As the support tray 15 and the lid member 14 move together in the (+Y) direction, the support tray 15 supporting the substrate S is placed in the processing space SP within the processing chamber 100, and the opening 101 is closed by the lid member 14.

[0056] In Figure 3, the period before time T0 corresponds to the substrate loading process. When the support tray 15 is pulled out of the chamber and the substrate S is loaded, valves 553, 557, 574, and 576 are all closed. Therefore, the amount of processing fluid supplied to and discharged from the processing space SP is zero. Also, at this time, the pressure inside the processing space SP (hereinafter referred to as "chamber pressure") is atmospheric pressure Pa, and the atmosphere inside the processing space SP is air.

[0057] From this state, carbon dioxide is introduced into the processing space SP as the processing fluid. Specifically, this is done as follows: Of the two discharge ports provided vertically facing the processing space SP, the processing fluid is first discharged from the lower discharge port, i.e., discharge port 178 (step S102, time T0). Specifically, valve 576 is opened, and the processing fluid is sent from piping 572 towards discharge port 178. As a result, the processing fluid is supplied to the processing space SP at a predetermined flow rate from the lower introduction channel 17b (simply labeled "lower" in Figure 3), and the processing fluid is discharged into the space below the support tray 15 within the processing space SP.

[0058] When the high-pressure processing fluid flows into the lower-pressure processing space SP, the fluid pressure temporarily decreases and the processing fluid undergoes a phase change from gas to liquid. However, as the supply continues, the chamber pressure gradually increases. This state is maintained until the chamber pressure reaches the critical pressure Pc of the processing fluid (step S103). The chamber pressure can be detected by the pressure gauge 554. The determination in step S103 can be made by comparing the detection result of the pressure gauge 554 with a threshold value set to the critical pressure Pc or a slightly higher value (e.g., 7.5 MPa).

[0059] In principle, it is preferable to determine time T1 from the detection result of the chamber pressure. However, if the amount of processing fluid introduced into the processing space SP is appropriately controlled, it is possible to reproducibly estimate when the chamber pressure will reach the critical pressure Pc. Therefore, for example, the time from the start of introducing the processing fluid until the chamber pressure reaches the critical pressure Pc may be experimentally determined in advance, and a processing recipe may be set accordingly. Then, the chamber pressure may be determined to have reached the critical pressure Pc when that time has elapsed since the start of the processing fluid supply.

[0060] After time T1, when the chamber pressure reaches the critical pressure Pc, valve 574 is opened, and the processing fluid, which has been transported at a predetermined flow rate through the upper inlet channel 17a (simply labeled "upper" in Figure 3), is discharged from the upper discharge port 174 (step S104). The discharged processing fluid flows in the (-Y) direction through the space between the ceiling surface 110a of the processing space SP and the substrate surface Sa. That is, a laminar flow of the processing fluid is formed along the substrate surface Sa. Since the chamber pressure exceeds the critical pressure Pc, a laminar flow of the processing fluid in a supercritical state is formed.

[0061] As the processing fluid is supplied above the substrate S and below the support tray 15, the pressure inside the chamber increases further. When the pressure inside the chamber reaches a preset target pressure Pt, this state is maintained for a predetermined time (step S105, time T2-T3). For example, by pre-setting the pressure of the processing fluid output by the fluid supply unit 57 as the target pressure Pt, the pressure inside the chamber can be maintained at the target pressure Pt. The value of the target pressure Pt should be a value that is sufficiently large compared to the critical pressure Pc; for example, for carbon dioxide, where the critical pressure Pc is 7.38 MPa, the target pressure Pt can be set to about 10-12 MPa.

[0062] As shown in Figure 3, the period from time T0 to time T2 is the "pressure boosting process" period, during which the chamber pressure is increased over time. During the pressure boosting process, the processed fluid is discharged only from the lower discharge port 178 until the chamber pressure reaches the critical pressure Pc. After the time the chamber pressure reaches the critical pressure Pc, the processed fluid is discharged from the upper discharge port 174 in addition to the lower discharge port 178.

[0063] On the other hand, the period from time T2 to time T3 is a "constant pressure processing process" in which the chamber pressure is maintained at the target pressure Pt. During this time, the processing space SP is filled with a supercritical processing fluid, so the liquid film covering the substrate surface Sa is replaced by the processing fluid, and the liquid that has separated from the substrate S dissolves into the processing fluid. The constant pressure processing process continues until the liquid has been completely replaced.

[0064] After the constant-pressure processing process continues for a predetermined time, a "depressurization process" is performed to discharge the processing fluid from the processing space SP and reduce the pressure inside the chamber (step S106, time T3). Specifically, valves 574 and 576 are closed to stop the discharge of the processing fluid from the discharge ports 174 and 178, and valves 553 and 555 are opened to discharge the processing fluid from the processing space SP. Liquid components and contaminants that have separated from the substrate S and dissolved in the processing fluid are also discharged outside the chamber along with the processing fluid. In the figure, the upper discharge channel 18a and the lower discharge channel 18b are simply abbreviated as "upper" and "lower," respectively.

[0065] The discharge volume at this time is relatively small, and the chamber pressure decreases gradually. This prevents the processing fluid from liquefying or solidifying due to a rapid drop in temperature caused by the decrease in pressure. In this case, both valves 553 and 555 are open, and the processing fluid is discharged from both the upper discharge channel 18a and the lower discharge channel 18b, but the processing fluid may be discharged from either the upper or lower channel.

[0066] When it is determined that the chamber pressure has dropped to the critical pressure Pc (step S107, time T4), the discharge rate of the processed fluid is increased (step 108). This increases the rate of depressurization. Since the processed fluid changes from a supercritical state to a gas phase when it falls below the critical pressure Pc, increasing the rate of depressurization does not cause the processed fluid to liquefy and create a gas-liquid interface. In this way, the time required for the depressurization process can be shortened. In this case as well, the determination of the chamber pressure may be based on the detection result of the pressure gauge 554, or on a preset time.

[0067] After time T5, when the chamber pressure drops to approximately atmospheric pressure (Pa), the processed substrate S can be removed from the processing chamber 100 (step S109). This completes the drying process for one substrate S. If there is a new substrate to be processed, the process returns to step S101, a new substrate S is received, and the above process is repeated (step S110).

[0068] As described above, in the supercritical drying process of this embodiment, the supply of the processing fluid is started to the space below the support tray 15 that supports the substrate S in the processing space SP, and after the chamber pressure exceeds the critical pressure Pc, the processing fluid is additionally supplied to the upper part of the substrate S. Therefore, in the initial stage of introducing the processing fluid, that is, when the pressure inside the processing chamber 100 is low, it is avoided that the high-velocity processing fluid will be blown onto the liquid film covering the substrate S. This makes it possible to prevent processing defects such as pattern collapse that occur when the liquid film is lost and the substrate surface Sa is exposed.

[0069] The problem of pattern collapse due to the spraying of processing fluid, and the solution of supplying processing fluid from below the substrate, are also described in the aforementioned Patent Document 2. However, in the prior art described in Patent Document 2, the processing fluid is supplied only from below, and the pressure is increased to a target pressure sufficiently higher than the critical pressure. In contrast, in this embodiment, when the chamber pressure reaches the critical pressure Pc, the processing fluid is also supplied to the space above the substrate S. Therefore, it is possible to shorten the time required to reach the target pressure.

[0070] When the processing fluid is not yet in a supercritical state but is close to it, for example, when the chamber pressure is around 5-6 MPa, a large amount of processing fluid dissolves into the liquid constituting the liquid film, causing a significant decrease in the viscosity of the liquid. This leads to a loss of film maintenance, causing the liquid film to spill off the substrate. If this phenomenon occurs when the surroundings are not filled with supercritical fluid, the substrate surface may be exposed, potentially resulting in processing defects.

[0071] On the other hand, in an environment filled with a supercritical processing fluid that has extremely low surface tension and dissolves liquids well, the liquid quickly dissolves into the processing fluid, and even if the liquid film breaks, it does not cause damage to the substrate. In other words, the reason why pattern collapse occurs due to the spraying of the processing fluid is thought to be that the processing fluid, which is sprayed at such a high flow rate, is in a liquid or gaseous state due to the pressure drop. Therefore, once the processing fluid becomes supercritical, there is no need to be concerned about damage caused by the spraying of the processing fluid. From this viewpoint, in this embodiment, by starting the flow of the processing fluid upwards on the substrate S when the chamber pressure exceeds the critical pressure Pc, it is possible to shorten the processing time compared to conventional technology.

[0072] Furthermore, in the conventional technology described above, after the chamber pressure reaches the target pressure, the supply of processing fluid from below is stopped and the processing fluid is stirred on the upper side of the substrate to improve processing efficiency. In contrast, in this embodiment, the processing fluid is supplied so as to form a horizontal, unidirectional laminar flow both on the upper side of the substrate S and on the lower side of the support tray 15. Supplying the processing fluid in this manner suppresses the generation of turbulence around the substrate S, making it possible to quickly remove liquids and contaminants that have detached from the substrate S and prevent re-adhesion. Thus, this embodiment differs from the conventional technology in terms of the action of the processing fluid flowing along the substrate surface.

[0073] Incidentally, in the supercritical drying process of the above embodiment, the processing fluid is not discharged during the pressurization process. However, as shown in the modified example below, it is also possible to discharge a small amount of fluid in parallel, for example, to purge any remaining outside air or contaminants in the processing space SP.

[0074] Figures 4 through 6 are timing charts showing modified versions of the supercritical drying process. In these figures, only the timing of the discharge start, indicated by the white arrow, differs from the process shown in Figure 3.

[0075] In the first modified example shown in Figure 4, when the supply of the processing fluid from the upper inlet channel 17a is started during the pressurization process, the discharge of the processing fluid via the upper discharge channel 18a is also started. Since the processing fluid flowing over the substrate S contains the liquid that constituted the liquid film, by starting the discharge from the upper discharge channel 18a after the processing fluid has become supercritical, the liquid components separated from the substrate S can be quickly discharged outside the chamber. This reduces the amount of liquid components remaining in the chamber during the subsequent constant-pressure processing process, thereby improving the replacement efficiency.

[0076] In the second modified example shown in Figure 5, when the supply of processing fluid from the upper inlet channel 17a is started during the pressurization process, the processing fluid is discharged via the lower discharge channel 18b instead of the upper discharge channel 18a. In the processing space SP, below the support tray 15, some of the liquid constituting the liquid film may fall due to vibrations during substrate loading or a decrease in viscosity due to mixing with the processing fluid. Discharge from the space below the support tray 15 makes it possible to quickly remove such liquid components.

[0077] Furthermore, in the third modified example shown in Figure 6, the first and second modified examples are combined so that the processed fluid is discharged from both the upper discharge channel 18a and the lower discharge channel 18b. Therefore, it is possible to obtain both the effects of the first and second modified examples described above.

[0078] Furthermore, the pressurization rate can be controlled by adjusting the balance between the supply and discharge rates of the processing fluid during the pressurization process. Moreover, such adjustments can be performed independently between the space above the substrate S and the space below the support tray 15 within the processing space SP. In all examples, however, discharging the processing fluid before the time T1 when it becomes supercritical is undesirable because it reduces the pressurization rate before reaching the supercritical state, thereby increasing the risk of liquid film breakdown.

[0079] As described above, in the substrate processing apparatus 1 of the above embodiment, the processing space SP inside the processing chamber 100 corresponds to the "internal space" of the present invention. In the processing chamber 100, the lower discharge port 178 corresponds to the "first discharge port" of the present invention, and the upper discharge port 174 corresponds to the "second discharge port" of the present invention. In addition, the lower discharge channel 18b and the upper discharge channel 18a function as the "first discharge channel" and "second discharge channel" of the present invention, respectively.

[0080] Furthermore, in the above embodiment, the support tray 15 functions as the "support member" of the present invention. Also, the control unit 90 functions as the "control unit" of the present invention. In addition, in the supercritical drying process shown in Figure 2, step S101 corresponds to the "first step" of the present invention, steps S102 to S105 correspond to the "second step" of the present invention, and steps S106 to S108 correspond to the "third step" of the present invention. Also, in the above embodiment, the critical pressure Pc corresponds to the "first pressure" of the present invention, and the target pressure Pt corresponds to the "second pressure" of the present invention.

[0081] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, in the above embodiments, the critical pressure Pc of carbon dioxide, which is the processing fluid, is used as the value corresponding to the "first pressure" of the present invention for the purpose of explaining the principle. However, in actual processing, in order to more reliably ensure that the supercritical state is maintained regardless of the effects of measurement errors, it is preferable to use a value for the first pressure that is slightly higher than the critical pressure (for example, 7.5 MPa compared to the critical pressure of carbon dioxide of 7.38 MPa).

[0082] Furthermore, for example, in the supercritical drying process of the above embodiment, a constant pressure process and a depressurization process are provided after the pressurization process, and the depressurization rate is changed in two stages during the depressurization process. However, the present invention is characterized by the process when the chamber pressure is increased from approximately atmospheric pressure to a target pressure greater than the critical pressure, and the processing content before and after this is not limited to what is described above.

[0083] Furthermore, the substrate processing apparatus 1 of the above embodiment is equipped with instruments for measuring the flow rate and pressure of the processing fluid. However, if the processing can be performed with high reproducibility by using a processing recipe created based on the results of preliminary experiments, at least some of these instruments may be omitted. Of course, these instruments can be used to monitor whether the processing is being performed according to the recipe.

[0084] Furthermore, the various chemical substances and set values ​​used in the processing of the above embodiments are merely examples, and various other substances can be used as long as they are consistent with the technical concept of the present invention as described above.

[0085] As described above with specific embodiments as examples, in the substrate processing method of the present invention, for example, the second step is configured such that, after the supply of processing fluid from the first discharge port is started, the supply of processing fluid from the second discharge port is started after the pressure in the internal space reaches a first pressure which is equal to or greater than the critical pressure, and the third step may be performed after the supply of processing fluid from the second discharge port is started and the pressure in the internal space reaches a second pressure which is greater than the first pressure.

[0086] With this configuration, the start time of discharge from the second discharge port and the start time of the third process can be determined based on a comparison between the internal pressure of the processing chamber and predetermined values ​​(first pressure, second pressure).

[0087] Alternatively, for example, the third step may be performed after a predetermined period of time during which the pressure inside the internal space remains at or above the second pressure. By maintaining a state in which the pressure inside the processing chamber is greater than the critical pressure in this way, it is possible to sufficiently replace and remove the liquid adhering to the substrate.

[0088] Alternatively, for example, the processing fluid may be supplied to the first and second discharge ports under pressure exceeding the critical pressure. With such a configuration, the processing fluid is supplied under sufficiently high pressure, and a supercritical state can be achieved in the internal space of the processing chamber in a short time.

[0089] In this case, the processing fluid may be supplied to the first and second discharge ports at a temperature higher than the critical temperature. With such a configuration, it is possible to immediately supply the processing fluid in a supercritical state to the internal space, and if necessary, the processing fluid can be changed to any phase by adjusting the pressure.

[0090] Furthermore, for example, in the third step, the processing fluid may be discharged from the side opposite the first discharge port with the substrate in between within the internal space, or from the side opposite the second discharge port with the substrate in between. With such a configuration, the processing fluid forms a laminar flow that flows in one direction within the internal space, which prevents liquid components and contaminants that have migrated from the substrate to the processing fluid from re-adhering to the substrate.

[0091] Furthermore, in the substrate processing apparatus according to the present invention, it is preferable that the first discharge port and the second discharge port are provided in the same direction when viewed from the substrate in a side view. With such a configuration, a flow of processing fluid is formed in the same direction above the substrate and below the support member in the internal space, and the generation of turbulence that causes substrate contamination is suppressed.

[0092] In this case, a first discharge channel is provided in the internal space that discharges the processed fluid from the side opposite the first discharge port, with the substrate in between, and a second discharge channel is provided in the internal space that discharges the processed fluid from the side opposite the second discharge port, with the substrate in between. The fluid discharge section may be configured to discharge the processed fluid from the internal space via the first and second discharge channels. With such a configuration, the flow of the processed fluid forming a laminar flow can be made smoother, and contamination of the substrate by turbulence can be prevented more effectively.

[0093] Furthermore, the control unit may be configured to control the fluid discharge unit so that the discharge of the processed fluid through the first discharge channel and the discharge of the processed fluid through the second discharge channel are performed independently. With such a configuration, it is possible to use either the discharge of the processed fluid from the space above the substrate or the discharge of the processed fluid from the space below the support member, depending on the purpose. [Industrial applicability]

[0094] This invention can be applied to all techniques for processing substrates using a supercritical fluid in a processing chamber. For example, it can be applied to substrate drying processes in which substrates such as semiconductor substrates are dried using a supercritical fluid. [Explanation of Symbols]

[0095] 1. Substrate processing device 15. Support tray (support member) 18a Upper discharge channel (second discharge channel) 18b Lower discharge channel (first discharge channel) 90 Control Unit (Control Section) 100 Processing Chambers 174 Discharge port (second discharge port) 178 Discharge port (1st discharge port) Pc critical pressure (first pressure) Pt Target pressure (second pressure) S substrate S101 1st process S102~S105 2nd process S106~S108 3rd process SP processing space (internal space)

Claims

1. In a substrate processing method in which a substrate is processed with a processing fluid in a supercritical state, The first step involves placing the substrate, whose upper surface is covered with a liquid film, in a horizontal position on a flat support member and housing it in the internal space of the processing chamber. A second step involves filling the internal space with the processing fluid in a supercritical state, A third step involves discharging the processing fluid from the internal space. Equipped with, The side wall surface of the processing chamber that constitutes the internal space is provided with a first discharge port that opens in a slit shape extending horizontally facing the gap formed between the bottom surface of the wall and the lower surface of the support member, and discharges the processing fluid horizontally toward the space formed in the gap, and a second discharge port that opens in a slit shape extending horizontally facing the gap formed between the ceiling surface and the upper surface of the substrate, and discharges the processing fluid horizontally toward the space formed in the gap. The processing fluid discharged from the first discharge port and passing between the bottom surface and the lower surface of the support member is discharged from a first discharge channel provided horizontally within the internal space, on the side opposite the side wall surface, sandwiching the support member. Meanwhile, the processing fluid discharged from the second discharge port and passing between the ceiling surface and the upper surface of the substrate is discharged from a second discharge channel provided horizontally within the internal space, on the side opposite the side wall surface, sandwiching the support member. In the second step described above, The pressurized processing fluid is supplied from the first discharge port into the internal space to increase the pressure of the internal space. A substrate processing method comprising, after the internal pressure of the internal space exceeds the critical pressure of the processing fluid, in addition to supplying from the first discharge port, starting to supply the pressurized processing fluid to the internal space from the second discharge port.

2. In the second step, after the supply of the processing fluid from the first discharge port is started, and after the pressure in the internal space reaches a first pressure which is equal to or greater than the critical pressure, the supply of the processing fluid from the second discharge port is started. The substrate processing method according to claim 1, wherein the third step is performed after the supply of the processing fluid from the second discharge port has started and the pressure in the internal space has reached a second pressure greater than the first pressure.

3. The substrate processing method according to claim 2, wherein the third step is performed after a predetermined period of time during which the pressure in the internal space is equal to or greater than the second pressure.

4. The substrate processing method according to claim 1, wherein the processing fluid is pressurized to a pressure higher than the critical pressure and supplied to the first and second discharge ports.

5. The substrate processing method according to claim 4, wherein the processing fluid is supplied to the first and second discharge ports at a temperature higher than the critical temperature.

6. The substrate processing method according to claim 1, wherein in the second step, the processing fluid is not discharged from the first discharge channel and the second discharge channel at least until the internal pressure exceeds the critical pressure.

7. The substrate processing method according to claim 6, wherein in the second step, after the internal pressure exceeds the critical pressure, the processing fluid is discharged from at least one of the first discharge channel and the second discharge channel.

8. In a substrate processing apparatus that processes a substrate using a processing fluid in a supercritical state, A flat support member on which the aforementioned substrate can be placed, A processing chamber having an internal space capable of housing the support member together with the substrate in a horizontal position, A fluid supply unit that supplies the processing fluid to the internal space, A fluid discharge unit for discharging the processing fluid from the internal space, Control unit for controlling the fluid supply unit and Equipped with, The side wall surface of the processing chamber that constitutes the internal space is provided with a first discharge port that opens in a slit shape extending horizontally facing the gap formed between the bottom surface of the wall and the lower surface of the support member, and discharges the processing fluid horizontally toward the space formed in the gap, and a second discharge port that opens in a slit shape extending horizontally facing the gap formed between the ceiling surface and the upper surface of the substrate, and discharges the processing fluid horizontally toward the space formed in the gap. The internal space is provided with a first discharge channel that discharges the processing fluid from the side opposite the first discharge port, sandwiching the substrate horizontally, and a second discharge channel that discharges the processing fluid from the side opposite the second discharge port, sandwiching the substrate horizontally, and the fluid discharge unit discharges the processing fluid from the internal space via the first discharge channel and the second discharge channel. When the support member on which the substrate is placed is housed in the internal space, the control unit controls the fluid supply unit, The supply of the processing fluid from the first discharge port to the internal space is started to increase the pressure of the internal space. When the internal pressure of the internal space exceeds the critical pressure of the processing fluid, in addition to the supply from the first discharge port, the supply of the processing fluid to the internal space from the second discharge port is started. Circuit board processing equipment.

9. The substrate processing apparatus according to claim 8, wherein, in a side view, the first discharge port and the second discharge port are provided in the same direction when viewed from the substrate.

10. The substrate processing apparatus according to claim 9, wherein the control unit controls the fluid discharge unit and independently performs the discharge of the processing fluid through the first discharge channel and the discharge of the processing fluid through the second discharge channel.

11. The substrate processing apparatus according to claim 10, wherein the processing fluid is not discharged from the first discharge channel and the second discharge channel until the internal pressure exceeds the critical pressure of the processing fluid.

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