Substrate processing method and substrate processing apparatus

Abstract

To satisfactorily dry a substrate while effectively suppressing collapse of a pattern formed on the surface of the substrate in a substrate processing technique for drying the substrate using a processing fluid in a processing space of a processing container.SOLUTION: In a substrate processing technology according to the present invention in which a pressurization step, a constant pressure step, and a depressurization step are performed in this order within a processing container, between the pressurization step and the constant pressure step or in the initial stage of the constant pressure step, while maintaining first pressure in a processing space, the flow rate of the processing fluid in the processing space is suppressed to a second flow rate that is lower than the first flow rate. This promotes interdiffusion between the processing fluid and the liquid in the processing space. After the diffusion progresses, the substrate is dried by discharging the processing fluid from the processing space.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a substrate processing technique for processing a substrate with a processing fluid in a supercritical state in a processing space of a processing vessel. [Background technology]

[0002] Processing processes for various substrates, such as semiconductor substrates and glass substrates for display devices, involve treating the surface of the substrate with various processing fluids. While processing using liquids, such as chemicals and rinses, as processing fluids has been widely used in the past, processing using supercritical fluids has also come into practical use in recent years. In particular, when processing substrates having fine patterns formed on their surfaces, supercritical fluids, which have lower surface tension than liquids, can penetrate deep into the gaps in the patterns, enabling efficient processing and reducing the risk of pattern collapse due to surface tension during drying.

[0003] For example, Patent Document 1 describes a substrate processing apparatus that performs a drying process on a substrate using a supercritical fluid. In this apparatus, a wafer (substrate) placed on a thin holding plate is carried into the interior (processing space) of a processing vessel from one end, and carbon dioxide in a supercritical state is introduced into the processing vessel from the other end. A fluid discharge header is also provided within the processing vessel. A discharge port is connected to this fluid discharge header, and the supercritical fluid is discharged from the processing space to outside the processing vessel via the fluid discharge header and the discharge port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-082043 Summary of the Invention [Problem to be solved by the invention]

[0005] Although not described in detail in Patent Document 1, after a substrate having a pattern formed thereon and a liquid adhering thereto is carried into the processing space of a processing vessel, a pressurization step, a constant pressure step, and a depressurization step are performed in the processing space (see FIG. 3, which will be described later). That is, CO2 (carbon dioxide) is supplied as a processing fluid into the processing space, and the processing fluid in the processing space is pressurized to a pressure at which the processing fluid can be maintained in a supercritical state (pressurization step). Then, by supplying the processing fluid into the processing space and discharging the processing fluid from the processing vessel through the fluid discharge header, a laminar flow of the processing fluid flowing substantially parallel to the surface of the substrate is formed while maintaining the pressure (constant pressure step). This constant pressure step is then performed (depressurization step). The substrate is dried through this series of steps.

[0006] However, in the conventional technology, the processing fluid and the liquid cannot sufficiently interdiffuse with each other in the constant pressure process, and a two-phase state of the processing fluid and the liquid may remain between the patterns as shown in (a) of Figure 5, which will be explained later. As a result, it is difficult to effectively prevent the pattern from collapsing.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a substrate processing method and a substrate processing apparatus that can satisfactorily dry a substrate while effectively suppressing the collapse of a pattern formed on the surface of the substrate. [Means for solving the problem]

[0008] One aspect of the present invention is a substrate processing method for drying a substrate having a pattern formed on its surface and a liquid adhering thereto while the substrate is accommodated in a processing space of a processing vessel using a processing fluid in a supercritical state, the method comprising: a pressurization step in which processing fluid is supplied from a fluid supply unit to the processing space to pressurize the processing space to a first pressure at which the processing space is in a supercritical state; a constant pressure step in which the processing fluid is supplied to the processing space pressurized to the first pressure by the pressurization step and the processing fluid is discharged from the processing space, thereby circulating the processing fluid at a first flow rate through the processing space while maintaining the processing space at the first pressure; a depressurization step in which the processing fluid is discharged from the processing space following the constant pressure step to depressurize the processing space; and a diffusion step in which the flow rate of the processing fluid in the processing space is reduced to a second flow rate lower than the first flow rate while maintaining the processing space at the first pressure, between the pressurization step and the constant pressure step or during an initial stage of the constant pressure step, thereby mutually diffusing the liquid and the processing fluid in the processing space. Equipped with In the diffusion step, a flow rate switching operation is repeated to switch the flow rate of the processing fluid in the processing space between a first flow rate and a second flow rate.

[0009] Another aspect of the present invention is a substrate processing apparatus that dries a substrate having a pattern formed on its surface and a liquid adhering thereto using a processing fluid in a supercritical state while accommodating the substrate in a processing space of a processing vessel, the apparatus comprising: a fluid supply unit that supplies a processing fluid for supercritical processing to the processing space accommodating the substrate; a fluid discharge unit that discharges the processing fluid from the processing space accommodating the substrate; a fluid flow adjustment unit that adjusts the supply of the processing fluid from the fluid supply unit to the processing space and the discharge of the processing fluid from the processing space to the fluid discharge unit; and a control unit, wherein the control unit controls the fluid flow adjustment unit to supply the processing fluid to the processing space, thereby bringing the processing space into a supercritical state. a constant pressure operation in which the processing fluid is circulated through the processing space at a first flow rate while maintaining the processing space at the first pressure by supplying the processing fluid to the processing space pressurized to the first pressure and discharging the processing fluid from the processing space; a depressurization operation in which the processing space is depressurized by discharging the processing fluid from the processing space following the constant pressure operation; and a diffusion operation in which the liquid and the processing fluid are mutually diffused in the processing space by maintaining the processing space at the first pressure and reducing the flow rate of the processing fluid in the processing space to a second flow rate lower than the first flow rate between the pressurization operation and the constant pressure operation or during an initial stage of the constant pressure operation. In the diffusion operation, a flow rate switching operation is repeatedly performed to switch the flow rate of the processing fluid in the processing space between a first flow rate and a second flow rate. It is characterized by the following.

[0010] In the invention configured as described above, immediately after the processing space is pressurized to a first pressure at which the processing space is in a supercritical state, the flow rate of the processing fluid in the processing space is reduced to a second flow rate lower than the first flow rate while maintaining the pressure in the processing space at the first pressure. This promotes interdiffusion between the liquid in the processing space and the processing fluid in the supercritical state. After this diffusion has progressed, the processing fluid is discharged from the processing space to dry the substrate. [Effects of the Invention]

[0011] As described above, according to the present invention, after the liquid and the supercritical processing fluid are mutually diffused in the processing space, the processing fluid is discharged from the processing space to dry the substrate, thereby effectively suppressing pattern collapse and allowing the substrate to be satisfactorily dried. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a substrate processing apparatus to which a first embodiment of a substrate processing method according to the present invention can be applied. [Figure 2A] 10A and 10B are diagrams illustrating an operation of supplying a processing fluid to a processing space and an operation of discharging the processing fluid from the processing space in an example of a fluid flow adjusting unit installed in a substrate processing apparatus. [Figure 2B] 10A and 10B are diagrams illustrating a bypass operation of a processing fluid in an example of a fluid flow adjusting unit provided in a substrate processing apparatus. [Figure 3] 10 is a graph showing an example of changes in CO2 inflow and outflow amounts and changes in pressure in a processing space in the prior art. [Figure 4] 6 is a graph showing an example of changes in CO 2 inflow and outflow amounts and changes in pressure in a processing space in a first embodiment of a substrate processing method according to the present invention. [Figure 5] 1A and 1B are diagrams schematically showing a mixed state of a processing fluid and a liquid in the prior art and the first embodiment. [Figure 6]10 is a graph showing an example of changes in CO 2 inflow and outflow amounts and changes in pressure in the processing space in a second embodiment of the substrate processing method according to the present invention. [Figure 7] 10 is a graph showing an example of changes in CO 2 inflow and outflow amounts and changes in pressure in the processing space in a third embodiment of the substrate processing method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a diagram showing a schematic configuration of a substrate processing apparatus to which a first embodiment of a substrate processing method according to the present invention can be applied. The substrate processing apparatus 1 is an apparatus for processing the surface of various substrates, such as semiconductor substrates, using a supercritical fluid. To unify the directions in the following figures, an XYZ Cartesian 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 the vertical downward direction.

[0014] Here, the "substrate" in this embodiment can be any of various substrates such as semiconductor wafers, glass substrates for photomasks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FEDs (Field Emission Displays), substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, etc. Below, a substrate processing apparatus used mainly for processing semiconductor wafers will be described with reference to the drawings, but the apparatus can also be applied to processing the various substrates exemplified above.

[0015] The substrate processing apparatus 1 includes a processing unit 10, a supply unit 50, a fluid flow adjustment unit 70, and a control unit 90. The processing unit 10 is the main unit that performs the supercritical drying process, and the supply unit 50 supplies the processing unit 10 with chemical substances and power required for the process. The fluid flow adjustment unit 70 is provided between the processing unit 10 and the supply unit 50, and adjusts the supply of fluids used in the process to and the discharge of fluids from the processing unit 10.

[0016] 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 users and external devices. The operation of the devices, which will be described later, is achieved by the CPU 91 executing the control programs written in advance in the storage 93 and causing each part of the devices to perform predetermined operations.

[0017] The processing unit 10 includes a processing chamber 100. The processing chamber 100 includes 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 in the vertical direction by a joining member (not shown), and the third member 13 is joined to the (+Y) side surface of the first member 11 and the second member 12 by a joining member (not shown), thereby forming the processing chamber 100 with a hollow structure. The hollow internal space serves as a processing space SP where processing is performed on a substrate S. The substrate S to be processed is loaded into the processing space SP and undergoes processing. A slit-shaped opening 101 extending elongatedly in the X direction is formed on the (-Y) side surface of the processing chamber 100, and the processing space SP communicates with the external space via the opening 101.

[0018] A lid member 14 is provided on the (-Y) side surface of the processing chamber 100 so as to close the opening 101. A flat support tray 15 is attached in a horizontal position to the (+Y) side surface of the lid member 14, and the upper surface of the support tray 15 serves as 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 formed slightly larger than the planar size of the substrate S is provided on a substantially flat upper surface 151. The substrate S is accommodated in this recess 152, thereby holding the substrate S in a predetermined position on the support tray 15. The substrate S is held with the surface Sa to be processed (hereinafter sometimes simply referred to as the "substrate surface") facing upward. In this case, it is preferable that the upper surface 151 of the support tray 15 and the substrate surface Sa are flush with each other.

[0019] The lid member 14 is supported by a support mechanism (not shown) so as to be horizontally movable in the Y direction. The lid member 14 can be moved forward and backward relative to the processing chamber 100 by an advance / retract mechanism 53 provided in the supply unit 50. Specifically, the advance / retract mechanism 53 has a linear motion mechanism such as a linear motor, a linear motion guide, a ball screw mechanism, a solenoid, or an air cylinder, and this linear motion mechanism moves the lid member 14 in the Y direction. The advance / retract mechanism 53 operates in response to a control command from the control unit 90.

[0020] When the cover member 14 moves in the (-Y) direction, the support tray 15 is pulled out from 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 the substrate S on the support tray 15 and to remove the substrate S placed on the support tray 15. On the other hand, when the cover member 14 moves in the (+Y) direction, the support tray 15 is accommodated in the processing space SP. When a substrate S is placed on the support tray 15, the substrate S is carried into the processing space SP together with the support tray 15.

[0021] In supercritical drying, which is primarily intended to dry a substrate while preventing pattern collapse due to the surface tension of the liquid, the surface Sa of the substrate S is covered with a liquid film to prevent the pattern (denoted by symbol PT in FIG. 5) formed on the surface Sa from collapsing when the surface Sa is exposed. In other words, the substrate S is loaded into the processing space SP with the liquid constituting the liquid film adhering to the surface Sa. Suitable examples of the liquid include organic solvents with relatively low surface tension, such as isopropyl alcohol (IPA) and acetone. In this embodiment, isopropyl alcohol is used as an example of the "liquid" of the present invention.

[0022] The lid member 14 moves in the (+Y) direction to close the opening 101, thereby sealing the processing space SP. A seal 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 processing space SP in an airtight state. The seal member 16 may be an annular member made of an elastic resin material, such as rubber. 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 maintained in an airtight state, processing of the substrate S is performed in the processing space SP.

[0023] In this embodiment, a fluid of a substance that can be used in supercritical processing, such as carbon dioxide, is supplied in a gaseous or liquid state from a fluid supply section 57 provided in the supply unit 50 to the processing unit 10. Carbon dioxide is a chemical substance suitable for supercritical drying processing because it reaches a supercritical state at a relatively low temperature and pressure and has the property of dissolving organic solvents that are often used in substrate processing.

[0024] More specifically, the fluid supply unit 57 outputs a supercritical fluid, or a fluid that is supplied in gaseous or liquid form and subsequently becomes supercritical when subjected to a predetermined temperature and pressure, as a processing fluid for processing the substrate S. For example, gaseous or liquid carbon dioxide is output under pressure. The fluid is pressure-fed via the fluid flow adjustment unit 70 to input ports 102 and 103 provided on the (+Y) side surface of the processing chamber 100. That is, the fluid flow adjustment unit 70 operates in response to a control command from the control unit 90, thereby sending the fluid from the fluid supply unit 57 to the processing chamber 100. The detailed configuration and operation of the fluid flow adjustment unit 70 will be described later.

[0025] The fluid flow path 17 extending from the input ports 102, 103 to the processing space SP functions as an introduction flow path that introduces the processing fluid (CO in this embodiment) supplied from the fluid supply unit 57 into the processing space SP. Specifically, a flow path 171 is connected to the input port 102. A buffer space 172 is provided at the end of the flow path 171 opposite to the input port 102, and is formed so that the cross-sectional area of ​​the flow path suddenly increases.

[0026] A flow path 173 is further provided to connect the buffer space 172 and the processing space SP. The flow path 173 has a cross-sectional shape that is narrow in the vertical direction (Z direction) and long and wide in the horizontal direction (X direction), and the cross-sectional shape is approximately constant in the flow direction of the processing fluid. The end of the flow path 171 opposite the buffer space 172 is an outlet 174 that opens toward the processing space SP, and the processing fluid is introduced into the processing space SP from this outlet 174.

[0027] Desirably, the height of the flow path 173 is equal to the distance between the ceiling surface of the processing space SP and the substrate surface Sa when the support tray 15 is accommodated in the processing space SP. The discharge port 174 opens facing the gap between the ceiling surface 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 of the processing space SP can be flush with each other. In this way, the discharge port 174 opens in the shape of a horizontally elongated slit facing the processing space SP.

[0028] Similarly, a flow path for the processing fluid is formed below the support tray 15. Specifically, a flow path 175 is connected to the input port 103. A buffer space 176 is provided at the end of the flow path 175 opposite the input port 103, and is formed so that the cross-sectional area of ​​the flow path suddenly increases.

[0029] 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 long and wide in the horizontal direction (X direction), and the cross-sectional shape is approximately constant in the flow direction of the processing fluid. The end of the flow path 177 opposite the buffer space 176 is an outlet 178 that opens into the processing space SP, and the processing fluid is introduced into the processing space SP from this outlet 178.

[0030] Desirably, the height of the flow path 177 is equal to the distance between the bottom surface of the processing space SP and the lower surface of the support tray 15. The discharge port 178 opens facing the gap between the bottom surface of the processing space SP and the lower surface of the support tray 15. For example, the bottom surface of the flow path 177 and the bottom surface of the processing space SP can be flush with each other. In other words, the discharge port 178 opens in the shape of a horizontally elongated slit facing the processing space SP.

[0031] It is desirable that the positions of the flow paths 171 and 173 are different in the Z direction. When they are at the same height, part of the processing fluid that flows from the flow path 171 into the buffer space 172 flows straight into the flow path 173. This may cause a difference in the flow rate and flow velocity of the processing fluid flowing into the flow path 173 between the position corresponding to the flow path 171 and other positions in the width direction of the flow path, i.e., the X direction, which is perpendicular to the flow direction. This causes non-uniformity in the X direction in the flow of the processing fluid flowing from the flow path 173 into the processing space SP, resulting in turbulence.

[0032] By arranging the flow paths 171 and 173 at different positions in the Z direction, the processing fluid does not move in a straight line from the flow path 171 to the flow path 173, and the processing fluid can be introduced into the processing space SP as a uniform laminar flow in the width direction.

[0033] The processing fluid introduced from the introduction flow path 17 configured in this manner flows along the upper and lower surfaces of the support tray 15 within the processing space SP and is discharged to the outside of the processing chamber via the exhaust flow path 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 both form horizontal planes, and they face each other parallel to each other with a certain gap between them. This gap functions as an upstream region 181 of the exhaust flow path 18 that 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 part 55. This upstream region 181 has a cross-sectional shape that is narrow in the vertical direction (Z direction) and long and wide in the horizontal direction (X direction).

[0034] The end of the upstream region 181 opposite the processing space SP is connected to a buffer space 182. Although a detailed structure will be described later, the buffer space 182 is a space surrounded by the processing chamber 100, the cover member 14, and the seal member 16. The width of the buffer space 182 in the X direction is equal to or greater than the width of the upstream region 181, and the height of the buffer space 182 in the Z direction is greater than the height of the upstream region 181. Therefore, the buffer space 182 has a larger flow path cross-sectional area than the upstream region 181.

[0035] A downstream region 183 is connected to the upper part of the buffer space 182. The downstream region 183 is a through hole provided through the first member 11, which is an upper block constituting the processing chamber 100. The upper end of the downstream region 183 forms an output port 104 that opens to the upper surface of the processing chamber 100, and the lower end opens facing the buffer space 182.

[0036] As described above, in this embodiment, the exhaust flow path 18 on the upper surface side of the support tray 15 is divided into the following three regions: an upstream region 181 formed between the upper surface 151 of the support tray 15 and the lower surface of the first member 11; a downstream region 183 connected to the fluid discharge portion 55; an intermediate region (buffer space 182) that connects the upstream region 181 and the downstream region 183; It has the following characteristics.

[0037] Similarly, the bottom surface of the processing space SP and the lower surface of the support tray 15 both form horizontal planes, and are opposed to each other in parallel with a certain gap maintained therebetween. This gap functions as an upstream region 185 of the exhaust flow path 18 that guides the processing fluid flowing along the lower surface of the support tray 15 to the fluid discharge part 55. Furthermore, the upstream region 185 on the lower surface side of the support tray 15 is connected to a downstream region 187 via a buffer space 186, similar to the upper surface side of the support tray 15. That is, the exhaust flow path 18 on the lower surface side of the support tray 15 is divided into the following three regions, namely: an upstream region 185 formed between the lower surface of the support tray 15 and the upper surface of the second member 12; a downstream region 187 connected to the fluid discharge portion 55; an intermediate region (buffer space 186) that connects the upstream region 185 and the downstream region 187; It has the following characteristics.

[0038] The processing fluid that flows above the support tray 15 in the processing space SP is sent to the output port 104 via the upstream region 181, the buffer space 182, and the downstream region 183. Similarly, the processing fluid that flows below the support tray 15 in the processing space SP is sent to the output port 105 via the upstream region 185, the buffer space 186, and the downstream region 187. These output ports 104, 105 are connected to the fluid discharge unit 55 via the fluid flow adjustment unit 70, which will be described in detail next. Therefore, when the fluid flow adjustment unit 70 operates in response to a control command from the control unit 90, the processing fluid in the processing space SP is collected in the fluid discharge unit 55 via the fluid flow adjustment unit 70.

[0039] 2A and 2B are diagrams illustrating an example of a fluid flow adjustment unit installed in a substrate processing apparatus. FIG. 2A schematically illustrates the operation of each unit component when fresh processing fluid is fed into processing unit 10 and used processing fluid is recovered from processing unit 10. FIG. 2B, on the other hand, schematically illustrates the operation of each unit component when processing fluid is circumvented around processing unit 10 and flows from fluid supply unit 57 to fluid discharge unit 55. In these figures, the path along which the processing fluid flows is indicated by dotted arrows. In addition, in the figures, symbols representing valves with black triangles indicate that the valve is open, and symbols with white triangles indicate that the valve is closed.

[0040] The fluid flow adjusting section 70 has pipes 71 and 72 that connect the fluid supply section 57 to the input ports 102 and 103, respectively, and pipes 73 and 74 that connect the output ports 104 and 105 to the fluid discharge section 55, respectively.

[0041] A valve 751 and a filter 761 are inserted in the piping 71, in this order from the fluid supply unit 57 side (the left-hand side in FIGS. 2A and 2B). Furthermore, a valve 752, a filter 762, and an orifice 772 are inserted in the piping 72, in this order from the fluid supply unit 57 side. Therefore, when the valves 751 and 752 are opened in response to a control command from the control unit 90, the processing fluid is pressure-fed from the fluid supply unit 57 to the processing space SP of the processing chamber 100. Furthermore, in this embodiment, the valve openings of the valves 751 and 752 can be switched in multiple stages or continuously in response to the control command. Therefore, as will be described later, the flow rate of the processing fluid flowing into the processing space SP (hereinafter referred to as the "CO2 inflow rate") can be adjusted with high precision by adjusting the valve openings.

[0042] In this embodiment, the processing fluid is divided into upper and lower portions and flows into the processing space SP. Therefore, even if the valves 751 and 752 are opened to the same valve opening, a pressure difference may occur between the processing fluid flowing in through the input port 102 and the processing fluid flowing in through the input port 103. Therefore, in this embodiment, an orifice 772 is provided in the lower pipe 72 to suppress or eliminate the pressure difference. Of course, the pressure difference varies depending on the configuration of the processing chamber 100 and the dimensional relationships of each part. Therefore, in addition to providing an orifice only in the pipe 72, other configurations are possible, such as providing an orifice only in the pipe 71, providing both the pipes 71 and 72, or providing no orifice in either pipe. Furthermore, as the number of input ports increases, even more configurations are possible. In short, when supplying processing fluid to the processing space SP from multiple input ports, it is desirable to consider inserting an orifice to prevent a pressure difference between the input ports.

[0043] In order to control the discharge of the processing fluid supplied as described above from the processing space SP, a flow meter 783 and a valve 753 are inserted in the pipe 73 in this order from the output port 104 side (left-hand side in FIGS. 2A and 2B). Similarly, a flow meter 782 and a valve 754 are inserted in the pipe 74 in this order from the output port 105 side. Therefore, the processing fluid is recovered from the processing space SP to the fluid discharge unit 55 by opening the valves 753 and 754 in response to a control command from the control unit 90. Furthermore, in this embodiment, the valve openings of the valves 753 and 754 can be switched in multiple stages or continuously in response to the control command. Therefore, as will be described later, the flow rate of the processing fluid flowing out of the processing space SP (hereinafter referred to as the "CO2 outflow rate") can be adjusted with high precision by adjusting the valve openings.

[0044] In this embodiment, the CO inflow and CO outflow rates can be adjusted independently, which allows for variably controlling the pressure and flow rate within the processing space SP of the processing chamber 100, as shown in Figures 3 and 4, which will be described later.

[0045] Meanwhile, bypass pipes 791 and 792 are provided in the fluid flow adjustment unit 70 so as to detour away from the processing chamber 100. The bypass pipe 791 branches off from the pipe 71 on the fluid supply unit 57 side (left hand side in FIGS. 2A and 2B) of the valve 751 and merges with the pipe 73 on the fluid discharge unit 55 side (right hand side in FIGS. 2A and 2B) of the valve 753. The bypass pipe 792 branches off from the pipe 72 on the fluid supply unit 57 side (left hand side in FIGS. 2A and 2B) of the valve 752 and merges with the pipe 74 on the fluid discharge unit 55 side (right hand side in FIGS. 2A and 2B) of the valve 753. Valves 755 and 756 are inserted into the bypass pipes 791 and 792, respectively. Therefore, by opening valves 755 and 756 in response to a control command from control unit 90 while valves 751-754 are closed, all of the processing fluid sent from fluid supply unit 57 bypasses processing chamber 100 and flows to fluid discharge unit 55. In other words, the supply of processing fluid to processing chamber 100 can be temporarily stopped while fluid supply unit 57 and fluid discharge unit 55 remain operating. Valves 755 and 756 may also be designed to have a multi-stage or continuous switching capability for their valve opening in response to the control command. In this case, the amount of CO2 inflow, CO2 outflow, and bypassed CO2 can be adjusted by appropriately controlling the valve opening of valves 751-756. This characteristic is utilized in a second embodiment, which will be described later.

[0046] When a substrate S having a liquid (IPA in this embodiment) puddle on its surface Sa is carried into the substrate processing apparatus 1 configured as described above by a substrate transport device such as a transport robot (not shown), the lid member 14 moves in the (+Y) direction while supporting the substrate S. As a result, the substrate S is accommodated in the processing space SP together with the support tray 15, and the opening 101 is sealed by the lid member 14. During the substrate carrying-in process, all of the valves 751 to 756 are controlled to be closed.

[0047] Subsequently, a pressure increase step, a constant pressure step, and a depressurization step are performed in this order. In particular, in the first embodiment, the effect of suppressing pattern collapse is enhanced by performing a hold step in the initial stage of the constant pressure step. Here, to help understand why this effect is obtained in the first embodiment, first, a case in which the substrate processing apparatus 1 is operated in the same manner as a conventional apparatus will be described with reference to FIGS. 2A and 3. Then, the first embodiment of the present invention will be described in comparison with the conventional technology.

[0048] 3 is a graph showing an example of changes in CO2 inflow and outflow rates and changes in pressure in the processing space in the conventional technology. In the substrate processing apparatus 1, when processing a substrate S accommodated in the processing space SP using the same operational sequence as in the conventional apparatus, valves 755 and 756 are always closed. Therefore, substrate processing is performed as follows by opening and closing valves 751 to 754 and controlling the valve opening degrees without diverting the processing fluid via bypass pipes 791 and 792. In the conventional apparatus, a bypass system consisting of bypass pipes 791 and 792 and valves 755 and 756 is not required, and the apparatus described in Patent Document 1 does not have a bypass system either.

[0049] 2A, while the fluid discharge unit 55 and the fluid supply unit 57 are operating stably, the control unit 90 switches the valves 751 to 754 from a closed state to an open state, thereby starting the inflow of the processing fluid into the processing space SP and the outflow of the processing fluid from the processing space SP (timing T1). In other words, timing T1 indicates the start timing of the pressurization step.

[0050] The control unit 90 controls the valve openings of the valves 751 and 752 depending on the time elapsed since the start of the pressurization process (time T1), changing the CO2 inflow and CO2 outflow according to the profiles shown by the dashed and dotted lines, respectively. During this pressurization process, the CO2 inflow is controlled to be greater than the CO2 outflow, thereby linearly increasing the pressure in the processing space SP as shown by the solid line in Figure 3, and adjusting the pressure to a first pressure P1 higher than the critical pressure of carbon dioxide (approximately 7.9 MPa) at a predetermined time T2. This brings the processing fluid in the processing space SP into a supercritical state. The pressurization process performed from time T1 to time T2 in this manner corresponds to an example of the "pressurization operation" of the present invention.

[0051] Following the pressurization step, the pressure in the processing space SP is maintained at the first pressure P1, i.e., to execute a constant pressure step, the control unit 90 controls the valve apertures of the valves 751-754 as follows (constant pressure operation). That is, even after the timing T2 at which the pressurization step is completed has passed, the control unit 90 increases the CO2 inflow and CO2 outflow rates for a fixed period of time, as shown in Fig. 3. Then, after both the CO2 inflow and CO2 outflow rates reach the same flow rate FR1, the control unit 90 adjusts the valve apertures of the valves 751-754 so that both the CO2 inflow and CO2 outflow rates remain at the flow rate FR1 for a fixed period of time.

[0052] Then, in the latter half of the constant pressure step, the control unit 90 controls the valve apertures of the valves 751 and 752 so that the CO2 inflow rate starts to decrease. Then, at timing T3 after a certain amount of time has elapsed, the control unit 90 controls the valve apertures of the valves 753 and 754 so that the CO2 outflow rate starts to decrease. As a result, the CO2 outflow rate becomes greater than the CO2 inflow rate, the constant pressure step is completed, and the pressure in the processing space SP starts to decrease from the first pressure P1. In other words, timing T3 corresponds to the start timing of the depressurization step.

[0053] In this depressurization step, the control unit 90 controls the valve openings of the valves 751 to 754 so as to reduce the amount of CO2 inflow and outflow (depressurization operation). As a result, the pressure in the processing space SP decreases below the first pressure P1. This depressurization step continues until timing T4, at which the pressure in the processing space SP reaches zero.

[0054] As described above, in the conventional apparatus, the pressurization step, constant pressure step, and depressurization step are performed in this order by controlling the CO2 inflow and outflow rates according to the profile shown in Figure 3. In particular, the constant pressure step aims to mix the liquid into the processing fluid through interdiffusion between the processing fluid and the liquid. However, as described above, in the constant pressure step, the processing fluid flows at the first flow rate FR1 substantially parallel to the surface Sa of the substrate S, forming a laminar flow of the processing fluid. Therefore, as shown in the "Prior Art" section of Figure 5, for example, a two-phase state of the processing fluid (CO2) and the liquid (IPA) may remain between the patterns PT, and the effect of preventing the patterns PT from collapsing is not necessarily sufficient.

[0055] In contrast, in the first embodiment, in the initial stage of the constant pressure step, a flow of the processing fluid via bypass pipes 791 and 792, i.e., a detour is created, thereby suppressing the flow rate of the processing fluid in the processing space SP to a second flow rate FR2 lower than the first flow rate FR1. Hereinafter, the first embodiment of the present invention will be described with reference to Figures 2A, 2B, and 4.

[0056] Fig. 4 is a graph showing an example of changes in CO2 inflow and outflow rates and changes in pressure in the processing space in a first embodiment of the substrate processing method according to the present invention. This first embodiment differs significantly from the conventional technique shown in Fig. 3 in that a hold state is created in which no laminar flow of the processing fluid is formed (or the flow rate is suppressed) in the initial stage (timings T2 to T2a) of the constant pressure process; otherwise, the configuration is basically the same as the conventional technique shown in Fig. 3. Therefore, the following description will focus on these differences.

[0057] In the first embodiment, following the pressurization step, the control unit 90 stops the supply of the processing fluid to the processing space SP and the discharge of the processing fluid from the processing space SP. More specifically, at timing T2, the control unit 90 switches the valves 751 to 754 from an open state to a closed state, as shown in FIG. 2B. Simultaneously, the control unit 90 switches the valves 755 to 756 from a closed state to an open state. As a result, all of the processing fluid supplied from the fluid supply unit 57 flows to the fluid discharge unit 55 via the bypass pipes 791 and 792, bypassing the processing space SP. This bypass state continues only during the initial stage of the constant pressure step (timings T2 to T2a). At timing T2a, the control unit 90 switches the valves 751 to 754 from a closed state to an open state, and switches the valves 755 to 756 from an open state to a closed state, as shown in FIG. 2A. Therefore, in the initial stage of the constant pressure process, the processing fluid is in a non-circulating state in the processing space SP, and a laminar flow of the processing liquid is not formed, as shown in Fig. 4. Moreover, the processing space SP is maintained at a first pressure P1, and the processing fluid is maintained in a supercritical state. Therefore, in the processing space SP, the processing fluid and the liquid diffuse into each other, and as shown in the "First Embodiment" column of Fig. 5, for example, the processing fluid and the liquid mix with each other even between the patterns PT, forming a homogeneous supercritical phase.

[0058] In this way, the processing fluid and the liquid are effectively mixed to form a supercritical homogeneous phase, and the latter half of the constant pressure step and the depressurization step are carried out in the same manner as in the prior art.

[0059] As described above, according to the first embodiment, immediately after the processing space SP is pressurized to the first pressure P1 at which the processing space SP is in a supercritical state, the flow rate of the processing fluid in the processing space SP is reduced to the second flow rate FR2 (=0), which is lower than the first flow rate FR1. This promotes interdiffusion between the processing fluid and the liquid in the processing space SP. After this diffusion has progressed, the processing fluid is then discharged from the processing space SP. As a result, pattern collapse can be more effectively suppressed than in the prior art, and substrate drying can be performed satisfactorily.

[0060] In the first embodiment, a bypass system including bypass pipes 791 and 792 and valves 755 and 756 is provided to set the second flow rate FR2 to zero. This makes it possible to suddenly change the amount of CO2 inflow by switching between detouring to the bypass system and terminating the detouring while the treatment fluid is being continuously supplied from the fluid supply unit 57. In other words, a hold step can be added while the fluid supply unit 57 is operating stably and steadily.

[0061] The hold time (=T2a-T2) for maintaining the flow rate of the processing fluid in the processing space SP at the second flow rate FR2 can be selected appropriately depending on the combination of the processing fluid and the liquid. However, when the processing fluid and the liquid are carbon dioxide and IPA, respectively, the hold time is preferably set within the range of 30 to 45 seconds. This is because a hold time of less than 30 seconds results in insufficient interdiffusion between the processing fluid and the liquid. Conversely, a hold time of more than 45 seconds makes it difficult to maintain the supercritical state due to a temperature drop caused by heat radiation from the processing chamber 100, since the supply of the processing fluid, which has been adjusted to a temperature suitable for substrate processing, to the processing space SP is stopped. Note that a temperature adjustment means for adjusting the temperature in the processing space SP may be added to set a longer hold time while preventing a temperature drop.

[0062] The first pressure P1 can also be selected appropriately depending on the combination of the processing fluid and liquid. However, when the processing fluid and liquid are carbon dioxide and IPA, respectively, various experiments have confirmed that pattern collapse can be effectively prevented even when the first pressure P1 is set to a value lower than that of the first embodiment (9.5 MPa), for example, 8.5 MPa. However, the supercritical pressure of the mixed phase of carbon dioxide and IPA is higher than the critical pressure of carbon dioxide (7.9 MPa) and approaches the above-mentioned 8.5 MPa, which tends to reduce the diffusion and movement of the liquid (IPA) present between the patterns PT. Therefore, it is more preferable to set the first pressure P1 to a value greater than 8.5 MPa.

[0063] As described above, in the first embodiment, the holding step corresponds to an example of the "diffusion step" of the present invention, and the operation performed in the holding step corresponds to an example of the "diffusion operation" of the present invention. The processing chamber 100 corresponds to an example of the "processing vessel" of the present invention. The control unit 90 corresponds to an example of the "control unit" of the present invention.

[0064] The present invention is not limited to the above-described embodiment, and various modifications other than those described above are possible without departing from the spirit of the present invention. For example, in the first embodiment, the second flow rate FR2 of the processing fluid during the hold step is set to zero. However, as shown in FIG. 6, the CO inflow rate may be set slightly higher than the CO outflow rate, and the second flow rate FR2 may be set to approximately 0.1 (l / min) (second embodiment). Of course, the value of the second flow rate FR2 is not limited to this. In other words, a portion of the processing fluid sent from the fluid supply unit 57 may be sent to the processing space SP, while the remainder may be discharged to the fluid discharge unit 55 via bypass pipes 791 and 792 provided separately from the processing chamber 100, and the processing fluid may also be discharged from the processing space SP, so that the second flow rate FR2 is higher than zero and lower than the first flow rate FR1.

[0065] Furthermore, in the first and second embodiments, the second flow rate FR2 is maintained constant in the hold process, which is an example of the "diffusion process" of the present invention, but as shown in FIG. 7, for example, in the hold process, a flow rate switching operation may be repeated to switch the flow rate of the processing fluid in the processing space SP between the first flow rate FR1 and the second flow rate FR2 (third embodiment).

[0066] In the above embodiment, the diffusion step is performed in the initial stage of the constant pressure step, but a diffusion step may be added between the pressure increase step and the constant pressure step.

[0067] In the above embodiment, the support tray 15 is attached to the side of the lid member 14, and they move together, but this is not limiting. For example, the support tray may be configured to move independently of the lid member. In this case, the lid member may be a door-like member that can be attached to the opening of the processing chamber so as to be able to open and close freely.

[0068] Furthermore, the various chemical substances used in the treatment of the above-described embodiments are only examples, and various substances can be used instead as long as they are consistent with the technical concept of the present invention described above. [Industrial Applicability]

[0069] The present invention can be applied to any substrate processing technology in which a substrate is processed with a processing fluid in a supercritical state in a processing space of a processing vessel. [Explanation of symbols]

[0070] 1...Substrate processing equipment 10...Processing unit 55...Fluid discharge part 57...Fluid supply section 70…Fluid flow adjustment section 90...Control unit (control section) 100...Processing chamber (processing vessel) FR1…1st flow rate FR2…Second flow rate P1...First pressure S...Substrate Sa...(substrate) surface SP...processing space (of the processing chamber)

Claims

1. 1. A substrate processing method for drying a substrate having a pattern formed on a surface to which a liquid is attached, the substrate being accommodated in a processing space of a processing vessel, using a processing fluid in a supercritical state, the method comprising: a pressure increasing step of supplying the processing fluid from a fluid supply unit to the processing space to increase the pressure of the processing space to a first pressure at which the processing space is in a supercritical state; a constant pressure process in which the processing fluid is supplied to the processing space, which has been pressurized to the first pressure in the pressurization process, and the processing fluid is discharged from the processing space, thereby circulating the processing fluid through the processing space at a first flow rate while maintaining the processing space at the first pressure; a decompression step of discharging the processing fluid from the processing space to decompress the processing space following the constant pressure step; a diffusion step in which, between the pressurization step and the constant pressure step or in an initial stage of the constant pressure step, the flow rate of the processing fluid in the processing space is reduced to a second flow rate lower than the first flow rate while maintaining the processing space at the first pressure, thereby causing the liquid and the processing fluid to diffuse mutually in the processing space; Equipped with In the diffusion step, a flow rate switching operation is repeated to switch the flow rate of the processing fluid in the processing space between the first flow rate and the second flow rate. A substrate processing method comprising:

2. 2. The substrate processing method according to claim 1, In the diffusion step, the second flow rate becomes zero by discharging all of the processing fluid sent from the fluid supply unit via a bypass pipe provided separately from the processing vessel.

3. 2. The substrate processing method according to claim 1, In the diffusion process, a portion of the processing fluid sent from the fluid supply unit is sent into the processing space, while the remainder is discharged via a bypass piping provided separately from the processing vessel, and the processing fluid is also discharged from the processing space, so that the second flow rate is higher than zero and lower than the first flow rate.

4. 4. The substrate processing method according to claim 1, further comprising: The substrate processing method, wherein the diffusion step is performed for a period of time in the range of 30 seconds to 45 seconds.

5. 5. The substrate processing method according to claim 1, further comprising: The method for processing a substrate, wherein the processing fluid is carbon dioxide.

6. 1. A substrate processing apparatus that dries a substrate having a pattern formed on its surface and a liquid adhering thereto using a processing fluid in a supercritical state while accommodating the substrate in a processing space of a processing vessel, the apparatus comprising: a fluid supply unit that supplies a processing fluid for supercritical processing to the processing space in which the substrate is accommodated; a fluid discharge unit that discharges the processing fluid from the processing space in which the substrate is accommodated; a fluid flow adjusting unit that adjusts the supply of the processing fluid from the fluid supply unit to the processing space and the discharge of the processing fluid from the processing space to the fluid discharge unit; a control unit, The control unit controls the fluid flow adjustment unit, a pressure increasing operation of increasing the pressure of the processing space to a first pressure at which the processing space is in a supercritical state by supplying the processing fluid to the processing space; a constant pressure operation in which the processing fluid is circulated through the processing space at a first flow rate while maintaining the processing space at the first pressure by supplying the processing fluid to the processing space pressurized to the first pressure and discharging the processing fluid from the processing space; a depressurization operation of depressurizing the processing space by discharging the processing fluid from the processing space following the constant pressure operation; a diffusion operation between the pressurization operation and the constant pressure operation or during an initial stage of the constant pressure operation, in which the flow rate of the processing fluid in the processing space is reduced to a second flow rate lower than the first flow rate while maintaining the processing space at the first pressure, thereby mutually diffusing the liquid and the processing fluid in the processing space; Run In the diffusion operation, a flow rate switching operation is repeated in which the flow rate of the processing fluid in the processing space is switched between the first flow rate and the second flow rate. A substrate processing apparatus characterized by:

7. 7. The substrate processing apparatus according to claim 6, a bypass pipe provided separately from the treatment vessel for directly sending the treatment fluid supplied from the fluid supply unit to the fluid discharge unit; In the diffusion operation, the control unit sends all or part of the processing fluid supplied from the fluid supply unit to the fluid discharge unit via the bypass piping to adjust the flow rate of the processing fluid in the processing space.

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