Substrate processing method

Abstract

To provide a technology that can reduce the time required to remove liquid adhering to undersides of substrates as they are brought into a chamber.SOLUTION: A substrate processing method of the present invention comprises a process for supporting a substrate with liquid on its upper surface by placing the substrate on a flat support tray in an almost horizontal position; sealing an internal space by accommodating the support tray in the internal space of a chamber; introducing pressurized gas toward a gap space between a lower surface of the support tray and a bottom surface of the internal space; and introducing supercritical processing fluid into the interior space, and treating the substrate with the supercritical processing fluid.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a substrate processing technique for processing a substrate using a processing fluid in a supercritical state within a processing container.

Background Art

[0002] Processing steps for various substrates such as semiconductor substrates and glass substrates for display devices include processing substrates with various processing fluids. Such processing is sometimes performed in an airtight processing container for the purpose of efficiently using the processing fluid and preventing dissipation to the outside. For example, in the processing apparatus described in Patent Document 1, a substrate to be processed is carried into the internal space of a chamber having an opening on a side surface in a state where the substrate is placed on a flat support tray integrated with a lid, and the internal space is sealed when the lid closes the opening. From this state, a supercritical processing fluid is introduced to process the substrate. Since the internal space of the chamber is formed to be slightly larger than the enveloped outer contours of the substrate and the support tray, it is possible to reduce the amount of the processing fluid used and improve the processing efficiency.

[0003] In this type of technology, in order to prevent an unprocessed substrate from being exposed to air, or to prevent collapse of fine patterns formed on the substrate surface, the substrate is sometimes carried into the chamber in a state where liquid is pooled on its surface. Even in the above-mentioned conventional technology, the carried-in substrate has a surface covered with a liquid film of an organic solvent, for example, IPA (isopropyl alcohol), after a cleaning treatment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The liquid that forms such a film contributes to protecting the substrate surface during transport, but it should be removed as soon as possible during the subsequent supercritical fluid treatment. However, when substrates are transported while placed on a support tray, as in the conventional technology described above, the liquid that gets into the tiny gap between the bottom of the substrate and the support tray is particularly difficult to remove. This can lead to problems such as the time required for treatment to completely remove the liquid being prolonged, or poor treatment results due to the liquid remaining for a long time.

[0006] Therefore, it is preferable to take measures to promptly drain any liquid that has seeped to the underside of the substrate, but the conventional technology described above, which does not employ such measures, has room for improvement in this respect.

[0007] This invention has been made in view of the above problems, and aims to provide a technology that can shorten the time required to remove liquid adhering to the lower surface of a substrate being brought into a chamber, in a substrate processing technology that processes a substrate using a supercritical processing fluid in a chamber. [Means for solving the problem]

[0008] One aspect of the substrate processing method according to this invention involves processing a substrate with liquid deposited on its upper surface into a flat plate shape. A through hole was provided that penetrates between the upper and lower surfaces. Place it on the support tray. With a gap formed between the lower surface of the substrate and the upper surface of the support tray. A process of supporting in a horizontal position, and placing the support tray into the internal space of the chamber. With gap spaces formed between the lower surface of the support tray and the bottom surface of the internal space, and between the upper surface of the substrate and the ceiling surface of the internal space. The process of housing and sealing the internal space, and the lower surface of the support tray and the bottom surface of the internal space The aforementioned Pressurized gas is introduced into the gap space. Then, a pressure gradient from the lower side to the upper side of the support tray generates an airflow that flows from the lower side of the support tray through the through hole into the gap. The process includes the steps of introducing a supercritical fluid into the internal space and processing the substrate with the supercritical fluid.

[0009] In this configuration, a substrate with liquid-filled top surface is placed on a support tray and housed in the chamber, after which pressurized gas is introduced to the underside of the support tray. Immediately after the chamber is sealed, the air pressure inside is atmospheric pressure, and in this state, the introduction of pressurized gas to the underside of the support tray eventually fills the internal space with pressurized gas. During this process, an airflow is generated from the bottom to the top of the support tray due to the pressure gradient. This airflow also enters the gap between the underside of the substrate and the support tray, pushing away any liquid adhering to the underside of the substrate. As a result, it is possible to promote the removal of liquid from the underside of the substrate. [Effects of the Invention]

[0010] As described above, in this invention, by first introducing pressurized gas to the underside of the support tray housed in the chamber together with the substrate, liquid adhering to the underside of the substrate can be flushed away. Therefore, the time required to remove residual liquid in the subsequent supercritical fluid treatment can be shortened, and treatment defects caused by residual liquid can be suppressed. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows a schematic configuration of one embodiment of a substrate processing apparatus according to the present invention. [Figure 2] This is a perspective view showing the main parts of the processing unit. [Figure 3] This flowchart shows the processes performed by the substrate processing system. [Figure 4] This is a flowchart showing the processing steps for supercritical drying. [Figure 5] This diagram schematically shows the flow of the processing fluid in the processing space. [Figure 6] This diagram schematically shows the airflow inside the chamber during the drying gas supply process. [Figure 7] This figure shows an example of a fluid flow path for processing. [Modes for carrying out the invention]

[0012] Figure 1 shows a schematic configuration of one embodiment of the substrate processing apparatus according to the present invention. This substrate processing apparatus 1 is a device for processing the surface of various substrates, such as semiconductor substrates, using a supercritical fluid. In order to consistently show directions in the following figures, an XYZ Cartesian coordinate system is set up as shown in Figure 1. Here, the XY plane is the horizontal plane, and the Z direction represents the vertical direction. More specifically, the (-Z) direction represents the vertically downward direction.

[0013] In this embodiment, the "substrate" can be various types of substrates, including semiconductor wafers, photomask glass substrates, liquid crystal display glass substrates, plasma display glass substrates, FED (Field Emission Display) substrates, optical disk substrates, magnetic disk substrates, and magneto-optical disk substrates. The following description will primarily use a substrate processing apparatus used for processing disc-shaped semiconductor wafers as an example, with reference to the drawings, but the apparatus can be similarly applied to processing the various types of substrates exemplified above. Furthermore, various substrate shapes are also applicable.

[0014] Furthermore, many of the main components and basic operations of the substrate processing apparatus 1 in this embodiment are common to those described in Patent Document 1. For this reason, the configuration and operating principles of each part, which can be understood by referring to Patent Document 1, may be simplified or omitted in this specification.

[0015] The substrate processing apparatus 1 comprises a processing unit 10, a transfer unit 30, a supply unit 50, and a control unit 90. The processing unit 10 is the main unit for performing the supercritical drying process. The transfer unit 30 receives unprocessed substrates S transported by an external transport device (not shown) and loads them into the processing unit 10, and also transfers the processed substrates S from the processing unit 10 to the external transport device. The supply unit 50 supplies the chemical substances, power, and energy necessary for processing to the processing unit 10 and the transfer unit 30.

[0016] The control unit 90 controls each part of these apparatuses to implement predetermined processing. For this purpose, the control unit 90 includes 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 a user and external apparatuses. The operation of the apparatus described below is implemented when the CPU 91 executes a control program previously written in the storage 93 and causes each part of the apparatus to perform a predetermined operation.

[0017] The processing unit 10 has a structure in which a processing chamber 12 is mounted on a pedestal 11. The processing chamber 12 is formed by a combination of a plurality of metal blocks, and the hollow internal space of the processing chamber 12 constitutes a processing space SP. A substrate S to be processed is carried into the processing space SP and subjected to processing. A slit-shaped opening 121 extending elongated in the X direction is formed on the (-Y) side surface of the processing chamber 12, and the processing space SP communicates with an external space through the opening 121.

[0018] A lid member 13 is provided on the (-Y) side surface of the processing chamber 12 so as to close the opening 121. The lid member 13 closes the opening 121 of the processing chamber 12 to form an airtight processing container, which enables processing of the substrate S under high pressure in the internal processing space SP. A flat plate-shaped support tray 15 is attached to the (+Y) side surface of the lid member 13 in a horizontal posture, and the upper surface of the support tray 15 serves as a support surface on which the substrate S can be placed. The lid member 13 is supported so as to be horizontally movable in the Y direction by a support mechanism (not shown).

[0019] The lid member 13 is movable forward and backward relative to the processing chamber 12 by an advancing / retreating mechanism 53 provided in a supply unit 50. Specifically, the advancing / retreating 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, for example, and such a linear motion mechanism moves the lid member 13 in the Y direction. The advancing / retreating mechanism 53 operates in response to a control command from the control unit 90.

[0020] As the lid member 13 moves in the (-Y) direction, it separates from the processing chamber 12, and as shown by the dotted line, the support tray 15 is pulled out from the processing space SP through the opening 121, making the support tray 15 accessible. That is, it becomes possible to place the substrate S onto the support tray 15 and to remove the substrate S that is placed on the support tray 15. On the other hand, as the lid member 13 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.

[0021] The lid member 13 moves in the (+Y) direction and closes the opening 121, thereby sealing the processing space SP. A sealing member 122 is provided between the (+Y) side surface of the lid member 13 and the (-Y) side surface of the processing chamber 12, maintaining the airtight state of the processing space SP. The sealing member 122 is made of rubber, for example. In addition, the lid member 13 is fixed to the processing chamber 12 by a locking mechanism (not shown). Thus, in this embodiment, the lid member 13 can be switched between a closed state (solid line) in which the opening 121 is closed and the processing space SP is sealed, and a separated state (dotted line) in which it is far enough away from the opening 121 that the substrate S can be inserted and removed.

[0022] With the processing space SP in an airtight state, processing of the substrate S is carried out within the processing space SP. In this embodiment, a processing 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 low pressures, and it has the property of dissolving organic solvents, which are frequently used in substrate processing, well. 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.

[0023] The processing fluid is filled into the processing space SP, and when the processing space SP reaches an appropriate temperature and pressure, the processing space SP is filled with the processing fluid in a supercritical state. In this way, the substrate S is processed by the supercritical fluid in the processing chamber 12. The supply unit 50 is provided with a fluid recovery unit 55, and the fluid after processing is recovered by the fluid recovery unit 55. The fluid supply unit 57 and the fluid recovery unit 55 are controlled by the control unit 90. As will be described later, the fluid supply unit 57 has the function of supplying not only the processing fluid such as carbon dioxide that becomes supercritical, but also a pressurized inert gas, such as nitrogen gas, to the processing chamber 12.

[0024] To prevent the supercritical processing fluid from cooling and undergoing a phase change within the processing chamber 12, it is preferable to provide an appropriate heat source inside the processing chamber SP. In particular, to prevent unintended phase changes from occurring around the substrate S, a heater (not shown) is built into the support tray 15 in this embodiment. The heater's temperature is controlled by the temperature control unit 59 of the supply unit 50. The temperature control unit 59 operates in response to control commands from the control unit 90 and, as will be described later, also has the function of controlling the temperature of the processing fluid supplied from the fluid supply unit 57.

[0025] The processing space SP has a shape and volume that can accommodate the support tray 15 and the substrate S supported thereon. Specifically, the processing space SP has a rectangular cross-sectional shape that is wider horizontally than the width of the support tray 15 and greater vertically than the combined height of the support tray 15 and the substrate S, and has a depth that can accommodate the support tray 15. Thus, although the processing space SP has a shape and volume that can accommodate the support tray 15 and the substrate S, the gap between the support tray 15 and the substrate S and the inner wall surface of the processing space SP is small. Therefore, the amount of processing fluid required to fill the processing space SP is relatively small.

[0026] The transfer unit 30 is responsible for transferring the substrate S between the external transport device and the support tray 15. For this purpose, the transfer unit 30 comprises a main body 31, a lifting member 33, a base member 35, and a plurality of lift pins 37. The lifting member 33 is a columnar member extending in the Z direction and is supported so as to be movable in the Z direction by a support mechanism (not shown). A base member 35 having a substantially horizontal upper surface is attached to the upper part of the lifting member 33, and a plurality of lift pins 37 are erected upward from the upper surface of the base member 35. Each of the lift pins 37 supports the substrate S in a horizontal position from below by its upper end contacting the lower surface of the substrate S. In order to stably support the substrate S in a horizontal position, it is desirable to provide three or more lift pins 37 whose upper end heights are equal to each other.

[0027] The lifting member 33 is movable up and down by a lifting mechanism 51 provided in the supply unit 50. Specifically, the lifting mechanism 51 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 lifting member 33 in the Z direction. The lifting mechanism 51 operates in response to control commands from the control unit 90.

[0028] The lifting member 33 moves up and down, causing the base member 35 to move vertically, and the multiple lift pins 37 move vertically in conjunction with it. This enables the transfer of the substrate S between the transfer unit 30 and the support tray 15.

[0029] Figure 2 is a perspective view showing the main part of the processing unit. When the lid member 13 is separated in the (-Y) direction, the support tray 15 is pulled out from the processing chamber 12 into the external space. Below the support tray 15 at this time, a base member 35 having a lift pin 37 is positioned. A through hole 152 with a diameter larger than the diameter of the lift pin 37 is drilled in the support tray 15 at a position directly above the lift pin 37.

[0030] When the base member 35 rises, the upper end of the lift pin 37 reaches above the support surface 151 of the support tray 15 through the through hole 152. In this state, the substrate S, which is supported and transported by the hand H of an external transport device, is handed over to the lift pin 37. After the hand H is retracted, the lift pin 37 descends, and the substrate S is handed over from the lift pin 37 to the support tray 15. The substrate S can be unloaded by following the reverse procedure described above.

[0031] A recess 153, slightly larger than the planar size of the substrate S, is provided on the upper surface of the support tray 15. The substrate S, transferred from the lift pin 37 to the support tray 15, is housed in this recess 153, thereby restricting its horizontal displacement on the support tray 15. Given the positional relationship in which the lift pin 37 supports the lower surface of the substrate S and raises and lowers it, and the substrate S is housed in the recess 153, the through hole 152 for inserting the lift pin 37 is provided inside the recess 153.

[0032] Figure 3 is a flowchart showing some of the processes performed by the substrate processing system, including this substrate processing apparatus. This substrate processing apparatus 1 is used to dry the substrate S that has been cleaned with a cleaning solution in the previous process. Specifically, it is as follows: After the substrate S has been cleaned with a cleaning solution in the previous process (step S101), a liquid film of isopropyl alcohol (IPA) has been formed on its surface (step S102), and the substrate S is then transported to the substrate processing apparatus 1 (step S103).

[0033] 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 deterioration such as oxidation. To prevent these problems, the substrate S surface (pattern-forming surface) may be covered with a liquid or solid surface layer during transport.

[0034] 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 supported in a horizontal position and transported to the substrate processing apparatus 1 with a liquid film formed on its upper surface.

[0035] The substrate S is placed on the support tray 15 with the pattern-forming surface facing upwards and the upper surface covered with a thin liquid film (step S104). As the support tray 15 and the lid member 13 move together in the (+Y) direction, the support tray 15 supporting the substrate S is housed in the processing space SP within the processing chamber 12, and the opening 121 is closed by the lid member 13 (step S105).

[0036] In the sealed processing space SP into which the substrate S is brought along with the support tray 15, a drying gas is first supplied downwards towards the support tray 15 (step S106). This is a process to remove any liquid adhering to the underside of the substrate S by using the airflow to wash it away.

[0037] Between the lower surface of the substrate S and the upper surface of the support tray 15, more specifically the upper surface of the recess 153 that accommodates the substrate S, liquid that was adhering to the lower surface of the substrate S during loading, or liquid that has seeped in from the upper surface after loading, may have entered. The liquid forming the liquid film will be replaced by the supercritical fluid that is introduced later, but replacing the liquid that has entered such a tiny gap requires a long time, which increases the amount of processing fluid used. In addition, liquid that remains without being replaced can cause processing defects such as the re-adhesion of contaminants to the substrate S.

[0038] To avoid this problem, in this embodiment, a pressurized drying gas, such as nitrogen gas, is introduced from below the support tray 15 to push out any liquid that has entered the gap between the lower surface of the substrate S and the upper surface of the support tray 15. At this stage, it is not necessary to discharge the liquid out of the chamber. Details of this process will be described later.

[0039] After the supply of drying gas, supercritical drying is performed (step S107). Then, the processed substrate S is discharged to the next process (step S108). That is, the lid member 13 moves in the (-Y) direction, causing the support tray 15 to be pulled out of the processing chamber 12, and the substrate S is transferred to an external transport device via the transfer unit 30. At this point, the substrate S is in a dried state. The content of the next process is arbitrary.

[0040] Figure 4 is a flowchart showing the processing steps of the supercritical drying treatment. Below, we will describe an example in which carbon dioxide (CO2) is used as the processing fluid, but the type of processing fluid is not limited to this. A substrate S on which a paddle-shaped liquid film LP (Figure 5) has been formed is brought into the processing chamber 12 from the outside, and after the drying gas is supplied, the processing fluid is introduced into the processing space SP in a gas phase state (step S201). By introducing the gas phase processing fluid while exhausting the processing space SP, the atmosphere of the processing space SP is replaced by the processing fluid.

[0041] Next, the liquid-phase processing fluid is introduced into the processing space SP (step S202). The liquid carbon dioxide thoroughly dissolves the liquid (organic solvent; for example, IPA) that constitutes the liquid film LP on the substrate S, and releases it from the upper surface of the substrate S. By discharging the liquid in the processing space SP, the IPA remaining on the substrate S can be discharged (step S203).

[0042] Next, a supercritical processing fluid is introduced into the processing space SP (step S204). The processing fluid may be introduced after being brought to a supercritical state outside the processing chamber 12, or the processing fluid may be brought to a supercritical state by raising the temperature and pressure inside the processing chamber 12, which is filled with liquid processing fluid, above the critical point.

[0043] Subsequently, the processing chamber 12 is depressurized while maintaining its temperature, causing the supercritical fluid to vaporize and be discharged without passing through the liquid phase (step S205). This dries the substrate S. During this time, the pattern-forming surface of the substrate S is not exposed to the interface between the liquid and gas phases, thus preventing pattern collapse caused by the surface tension of the liquid. Furthermore, because the supercritical fluid has extremely low surface tension, the processing fluid can easily penetrate into the interior of the patterns, even on substrates with fine patterns formed on their surface. Therefore, any remaining liquid inside the patterns can be efficiently replaced. In this way, the substrate S is thoroughly dried.

[0044] As described above, in this embodiment, the processing space SP within the processing chamber 12 containing the substrate S is filled with a supercritical fluid to remove any remaining liquid components from the substrate S and dry the substrate S. Therefore, if the supercritical fluid that comes into contact with the substrate S contains impurities, these impurities will remain on the substrate S after drying, contaminating the substrate S.

[0045] Such sources of contamination include residual liquid that was attached to the substrate S during loading and impurities brought into the processing space SP from the outside. In particular, near the opening 121 of the processing chamber 12, impurities arriving from the outside space during loading and unloading of the substrate S, as well as impurities generated from components such as the sealing member 122, may be mixed into the processing fluid. Below, we will describe the measures taken in this embodiment to prevent the substrate S from being contaminated with impurities during the supercritical drying process.

[0046] Figure 5 is a schematic diagram showing the flow of the processing fluid in the processing space. As shown in Figure 5, the fluid supply unit 57 that supplies the processing fluid is connected to introduction channels 123 and 124 provided on the (+Y) side of the processing space SP, that is, on the opposite side from the opening 121 when viewed from the processing space SP. More specifically, the first introduction channel 123 and the second introduction channel 124 are formed in the processing chamber 12 further (+Y) side than the (+Y) side end of the substrate S housed in the processing space SP.

[0047] The first inlet channel 123 is connected to the fluid supply unit 57 by a pipe 162 having a valve 161. When the valve 161 is opened, the processing fluid from the fluid supply unit 57 flows into the first inlet channel 123. The first inlet channel 123 ultimately directs the fluid flow direction to the horizontal and discharges the processing fluid from the first inlet port 123a, which opens facing the processing space SP at the (+Y) side end of the processing space SP.

[0048] Meanwhile, the second inlet channel 124 is connected to the fluid supply unit 57 by a pipe 164 having a valve 163 and a pipe 166 having a valve 165. The processing fluid supplied from the fluid supply unit 57 is passed through pipe 164, and valve 163 is responsible for opening and closing the channel and adjusting the flow rate. On the other hand, nitrogen gas supplied from the fluid supply unit 57 is passed through pipe 166, and valve 165 is responsible for opening and closing the channel and adjusting the flow rate. Pipes 164 and 166 merge at the output sides of valves 163 and 165, respectively, and are connected to the second inlet channel 124. Therefore, it is possible to supply the processing fluid to the second inlet channel 124 via pipe 164 and nitrogen gas via pipe 166.

[0049] When valve 163 is opened, the processing fluid from the fluid supply unit 57 flows into the second flow path 124. When valve 165 is opened, nitrogen gas flows from the fluid supply unit 57 into the second flow path 124. The second inlet flow path 124 ultimately directs the fluid flow direction to the horizontal and discharges these fluids from the second inlet 124a, which opens facing the processing space SP at the (+Y) side end of the processing space SP.

[0050] The first inlet 123a opens to the processing space SP above the substrate S held within the processing space SP. On the other hand, the second inlet 124a opens to the processing space SP below the substrate S held within the processing space SP, and more precisely, below the support tray 15 that supports the substrate S. The first inlet 123a and the second inlet 124a are slit-shaped openings that extend elongated in the X direction with a constant opening width, and in the X direction they extend beyond the edge of the substrate S. Therefore, the processing fluid discharged from the first inlet 123a and the second inlet 124a, respectively, is introduced into the processing space SP as a thin layer in the vertical direction (Z direction) and wider than the width of the substrate S in the X direction, flowing in the (-Y) direction. It is sufficient that the direction of the processing fluid ultimately discharged from the first inlet 123a and the second inlet 124a is generally horizontal, and the intermediate flow path shapes are not limited to those shown.

[0051] Given the objective of the process, which is to fill the substrate S with supercritical fluid, one option is to not discharge the processing fluid until the processing space SP is filled with supercritical fluid. However, doing so could cause the processing fluid to stagnate within the processing space SP, potentially contaminating the substrate S with impurities present in the space. To prevent this, it is desirable to discharge the processing fluid even in the supercritical state, ensuring that a clean processing fluid is constantly supplied to the substrate S.

[0052] For this purpose, a first discharge channel 125 and a second discharge channel 126 for discharging the processing fluid are provided near the (-Y) side end of the processing space SP. Specifically, a first discharge port 125a opens on the ceiling surface of the processing space SP on the (-Y) side of the substrate S housed in the processing space SP, and the first discharge channel 125 communicating with this port is connected to the fluid recovery section 55 via a pipe 176 having a valve 175. When the valve 175 is opened, the processing fluid in the processing space SP is discharged to the fluid recovery section 55 via the first discharge channel 125.

[0053] On the other hand, a second discharge port 126a is opened at the bottom surface of the processing space SP, further to the (-Y) side than the (-Y) side end of the substrate S housed in the processing space SP. A second discharge channel 126 communicating with this port is connected to the fluid recovery section 55 via a pipe 178 having a valve 177. When the valve 177 is opened, the processing fluid in the processing space SP is discharged to the fluid recovery section 55 via the second discharge channel 126.

[0054] The first outlet 125a and the second outlet 126a are slit-shaped openings that extend elongated in the X direction with a constant opening width, and in the X direction they extend beyond the edge of the substrate S. In the Y direction, they open further to the (-Y) side than the (-Y) side edge of the substrate S. In the vicinity of these placement positions, the processing space SP is substantially divided vertically by the support tray 15. Therefore, the processing fluid flowing above the substrate S is discharged from the first outlet 125a, while the processing fluid flowing below the substrate S is discharged from the second outlet 126a.

[0055] The opening degrees of valves 171 and 175 are adjusted so that the flow rate of the processed fluid supplied to the first inlet channel 123 is equal to the flow rate of the processed fluid discharged from the first outlet channel 125. Similarly, the opening degrees of valves 173 and 177 are adjusted so that the flow rate of the processed fluid supplied to the second inlet channel 124 is equal to the flow rate of the processed fluid discharged from the second outlet channel 126.

[0056] With these configurations, the processing fluid introduced from the fluid supply unit 57 via the first introduction channel 123 is discharged almost horizontally from the first inlet 123a, flows along the upper surface of the substrate S, and is finally discharged to the outside from the first outlet 125a, and is ultimately recovered in the fluid recovery unit 55. On the other hand, the processing fluid introduced from the fluid supply unit 57 via the second introduction channel 124 is discharged almost horizontally from the second inlet 124a, flows along the lower surface of the support tray 15, and is finally discharged to the outside from the second outlet 126a, and is ultimately recovered in the fluid recovery unit 55. In other words, it is expected that a laminar flow of processing fluid in the (-Y) direction will be formed above the substrate S and below the support tray 15 within the processing space SP. The white arrows shown in Figures 5(a) and 5(b) schematically illustrate this flow of processing fluid.

[0057] In this way, by forming a laminar flow of the processing fluid moving in one direction in the processing space SP, particularly the space above the substrate S, it is possible to prevent turbulence from occurring around the substrate S. Therefore, even if liquid adheres to the surface of the substrate S, it dissolves into the supercritical processing fluid and flows downstream, preventing it from remaining on the substrate S after drying. Furthermore, by setting the flow direction of the processing fluid so that the opening 121, where impurities that can become sources of contamination are likely to be generated, is located downstream of the substrate S, it is prevented that impurities generated around the opening 121 are carried upstream by turbulence and adhere to the substrate S. As a result, it is possible to dry the substrate S well without contamination.

[0058] Next, the drying gas supply process (step S106 in Figure 3) performed in this embodiment will be described. As mentioned above, this process is performed after the substrate S is placed in the processing space SP and prior to the supercritical process, in order to flush out any liquid that has entered the gap between the substrate S and the support tray 15.

[0059] Figure 6 schematically shows the airflow inside the chamber during the drying gas supply process. When the support tray 15 on which the substrate S is placed is housed in the processing space SP and the lid 13 closes the opening 121, valves 161, 163, 165, 175, and 177 are closed, and the pressure inside the processing space SP is atmospheric pressure. From this state, valve 165 is opened. Then, pressurized nitrogen gas (N2 gas) supplied from the fluid supply unit 57 is introduced into the processing space SP from the second inlet 124a via the second introduction channel 124. The pressure of the nitrogen gas at this time can be significantly higher than atmospheric pressure and significantly lower than the critical pressure of the processing fluid, for example, around 0.1 MPa.

[0060] In Figure 6, the white arrows schematically represent the flow of nitrogen gas introduced into the processing space SP. The pressurized nitrogen gas is discharged from the second inlet 124a in a substantially horizontal direction toward the space between the lower surface of the support tray 15 and the bottom surface of the processing space SP. As a result, the pressure rises rapidly below the support tray 15. On the other hand, the pressure rise is more gradual above the support tray 15. Therefore, a pressure difference is created between the upper and lower parts of the support tray 15, which causes an airflow to flow upward from below the support tray 15.

[0061] Since the processing space SP is almost completely divided vertically by the support tray 15, a large pressure difference is generated in the short term, resulting in a high-velocity airflow. This airflow passes through small gaps, such as between the side of the support tray 15 and the side wall of the processing space SP, and moves upward towards the support tray 15. A portion of it also enters the gap between the substrate S and the support tray 15 through the through-holes 152 provided in the support tray 15. At this time, the liquid adhering to the lower surface of the substrate S is pushed out by the airflow and expelled from the gap between the substrate S and the support tray 15. On the other hand, above the support tray 15, there is no large horizontal pressure difference that would generate a strong airflow. Therefore, the impact on the liquid film LP covering the upper surface of the substrate S is small.

[0062] The liquid pushed out from the gap between the substrate S and the support tray 15 is discharged from the processing space SP to the outside by the introduction of the processing fluid in the subsequent supercritical drying process. In the drying gas supply process, even if only some of the liquid that has entered the narrow gap between the substrate S and the support tray 15 is pushed out to the outside, it is possible to shorten the time required for liquid discharge in the supercritical drying process. For this reason, it is not necessary to completely remove the liquid in the drying gas supply process.

[0063] When the drying gas fills the processing space SP and the pressure in the processing space SP becomes approximately equal to the pressure of the introduced drying gas, valve 165 is closed, and the supply of drying gas is stopped. Subsequently, valves 161 and 163 are opened, and the supply of the gaseous processing fluid to the processing space SP begins. In other words, the supercritical drying process begins.

[0064] The nitrogen gas used as the drying gas may be at room temperature, but it may also be heated to a temperature similar to that of the processing fluid introduced later. This is not, for example, to accelerate the volatilization of the liquid, but rather to maintain the temperature within the processing space SP. Furthermore, the type of gas used as the drying gas is not limited to nitrogen gas; various chemical substances can be used. To avoid affecting the substrate S, it is desirable that the gas does not contain oxygen or water vapor. Nitrogen gas, which is available in high purity and relatively low cost, is suitable for this application.

[0065] Furthermore, it is also possible to use carbon dioxide, which is the processing fluid, as the drying gas. When the same type of gas as the processing fluid is used as the drying gas, the difference from conventional processing is that after the support tray 15 is placed inside, there is a period during which the pressurized processing fluid is discharged only downwards from the support tray 15. In other words, after the support tray 15 is placed inside the processing space SP, valve 161 is closed and valve 163 is open for a certain period of time.

[0066] As a result, the gaseous processing fluid is introduced below the support tray 15, and the airflow caused by the pressure difference acts to push out the liquid in the gap between the substrate S and the support tray 15. In contrast, if the processing fluid is supplied both above and below the support tray 15 from the beginning, the airflow caused by the pressure difference described above will not occur, and therefore the effect of pushing out the liquid on the underside of the substrate S will be reduced.

[0067] Next, we will explain some more specific system configurations for achieving these conditions using several examples. Note that, for the purpose of explaining the principle, the valves and piping between the first introduction channel 123 and the second introduction channel 124 and the fluid supply unit 57 were represented in a simplified form above. In reality, as illustrated below, the fluid supply path becomes more complex in order to introduce the processed fluid into the processing space SP at the required time and in the required state.

[0068] Figure 7 shows an example of a fluid flow path for the processed fluid. Hereafter, the entire piping system provided between the fluid supply unit 57 and the processing chamber 12, and between the processing chamber 12 and the fluid recovery unit 55, will be denoted by reference numeral 200. In this example, the fluid supply unit 57 has the function of supplying carbon dioxide (CO2) as the processed fluid in gaseous, liquid, and supercritical states, and the function of supplying nitrogen (N2) gas as a dry gas.

[0069] The output of gaseous CO2 is branched into two pipes 201 and 221. Valve 202 is installed in one pipe 201. Valve 222 is installed in the other pipe 221. Similarly, the output of liquid CO2 is branched into two pipes 203 and 223. Valve 204 is installed in one pipe 203. Valve 224 is installed in the other pipe 223.

[0070] Furthermore, the output of the supercritical CO2 is branched into two pipes, 207 and 227. A valve 208 is inserted into one of the pipes 207. A heater 209 is provided on the output side of valve 208. A valve 211 is inserted into pipe 210, which is connected to the output side of heater 209. Similarly, a valve 228 is inserted into the other pipe 227, and a heater 229 is provided on the output side of valve 228. A valve 231 is inserted into pipe 230, which is connected to the output side of heater 229.

[0071] Pipes 201 and 203 merge at the output side of valves 202 and 204 to form pipe 205. Valve 206 is inserted into pipe 205. Pipes 205 and 210 merge at the output side of valves 206 and 211 to form pipe 212, which is connected to the first inlet channel 123 of the processing chamber 12. Similarly, pipes 221 and 223 merge at the output side of valves 222 and 224 to form pipe 225, which has valve 226 inserted into pipe 225. Pipes 225 and 230 merge at the output side of valves 226 and 231 to form pipe 232, which is connected to the second inlet channel 124 of the processing chamber 12.

[0072] In order to prioritize the clear indication of the flow of the processed fluid, the arrangement of the first inlet channel 123, the second inlet channel 124, the first discharge channel 125, and the second discharge channel 126 in the processing chamber 12 in Figure 7 differs from that shown in Figure 5, etc. Specifically, the positional relationship between the inlet channel and the discharge channel is reversed left to right.

[0073] On the output side of heater 209, pipe 213 branches off from pipe 210, and a valve 214 is inserted into pipe 213. Similarly, on the output side of heater 229, pipe 233 branches off from pipe 230, and a valve 234 is inserted into pipe 233. Pipes 213 and 233 are provided as a circulation path to return the supercritical fluid in the pipes to the fluid supply unit 57.

[0074] A pipe 251 is connected to the first discharge channel 125 of the processing chamber 12, and a temperature sensor 252 and a valve 253 are inserted into the pipe 251. The output side of the valve 253 is connected to the fluid recovery unit 55. Similarly, a pipe 261 is connected to the second discharge channel 126, and a temperature sensor 262 for detecting the fluid temperature and a valve 263 are inserted into the pipe 261. The output side of the valve 263 is connected to the fluid recovery unit 55.

[0075] The nitrogen gas output of the fluid supply unit 57 is connected to the second inlet 124 of the processing chamber 12 via piping 241. More specifically, valve 242, heater 249, and valve 249 are interposed in piping 241 in this order along the direction of nitrogen gas flow. At its end, piping 241 merges with piping 232.

[0076] The valves described above operate in response to control commands from the control unit 90, opening and closing the piping and adjusting the flow rate. In particular, when supercritical fluid is supplied to the processing space SP, the opening degree of each valve along the flow path is adjusted so that the flow rate of the processing fluid supplied to the first inlet channel 123 of the processing chamber 12 is equal to the flow rate of the processing fluid discharged from the first outlet channel 125, and so that the flow rate of the processing fluid supplied to the second inlet channel 124 is equal to the flow rate of the processing fluid discharged from the second outlet channel 126.

[0077] If the ratio between the amount of processing fluid supplied to the first introduction channel 123 and the amount of processing fluid supplied to the second introduction channel 124 is too large or too small, there is a risk that the processing fluid flowing below the substrate S may overflow above the substrate S, or conversely, the processing fluid flowing above the substrate S may overflow below. It is desirable that the flow rate of the processing fluid supplied to the first introduction channel 123 and the flow rate of the processing fluid supplied to the second introduction channel 124 be between 1:5 and 5:1, depending on the ratio of the cross-sectional area of ​​the channels above and below the substrate, respectively.

[0078] Furthermore, heaters 209 and 229 are controlled by the temperature control unit 59 of the supply unit 50 to heat the supplied fluid and adjust it to a target temperature. For this purpose, heaters 209 and 229 are assumed to have temperature sensors (not shown) that detect the temperature of the fluid. The outputs of these temperature sensors and temperature sensors 252 and 262 are provided to the temperature control unit 59, which then controls the energization of heaters 209 and 229.

[0079] To explain in relation to the supercritical drying process shown in Figure 4, in step S201, when a gaseous processing fluid is supplied, valves 202, 206, 222, and 226 on the path from the gas output of the fluid supply unit 57 to the processing chamber 12 are opened. As a result, gaseous carbon dioxide (CO2) is supplied to the processing space SP as the processing fluid. On the other hand, in step S202, when a liquid-phase processing fluid is supplied, valves 204, 206, 224, and 226 on the path from the liquid output of the fluid supply unit 57 to the processing chamber 12 are opened, thereby supplying liquid carbon dioxide (CO2) to the processing space SP as the processing fluid.

[0080] Furthermore, in step S204, when supercritical fluid is supplied as the processing fluid, valves 208, 211, 228, and 231 on the path from the supercritical output of the fluid supply unit 57 to the processing chamber 12 are opened. As a result, the supercritical fluid output via heater 209 is supplied to the first introduction channel 123 of the processing chamber 12, and the supercritical fluid output via heater 229 is supplied to the second introduction channel 124.

[0081] In response to control commands from the control unit 90, valves 253 and 263 are opened at appropriate timings, thereby adjusting the discharge amount of processing fluid from the processing space SP. In this way, as the supercritical drying process progresses, the valves work in coordination to supply and discharge the processing fluid into the processing chamber 12 in a manner appropriate to the processing content.

[0082] Furthermore, in the drying gas supply process shown in step S106 of Figure 3, when valve 242 is opened, pressurized nitrogen gas output from the fluid supply unit 57 is supplied to heater 249, and the nitrogen gas is heated to a predetermined temperature. Then, when valve 246 is opened, the heated nitrogen gas is supplied to the processing space SP via the second introduction channel 124. In this sense, it can be said that piping 241 corresponds one-to-one with piping 166 in Figure 5, and valve 246 corresponds one-to-one with valve 165 in Figure 5.

[0083] For supercritical processing fluids, the temperature and pressure of the processing fluid may change due to stagnation or pressure loss in the piping, and the state of the processing fluid supplied to the processing space SP may differ from the intended state. For example, even if the temperature of the processing fluid at the output of heaters 209 and 229 is at the target temperature, it may cool down in the piping and its temperature at the time of introduction into the processing space SP may be lower than the target temperature.

[0084] To address this problem, the following methods can be considered. Firstly, the output of heaters 209 and 229 can be kept circulating at all times. Specifically, when supercritical fluid is not being supplied to the processing chamber 12, that is, when valves 211 and 231 are closed, valves 214 and 234 can be opened to form a circulation path for the supercritical fluid via pipes 213 and 233. In this way, the supercritical fluid controlled to the target temperature will constantly circulate through the circulation path, preventing a drop in the temperature of the pipes when supply is not needed, and allowing for the rapid supply of processing fluid at a predetermined temperature when required.

[0085] Secondly, there is a method that uses the temperature detection results on the discharge side. Specifically, by detecting the temperature of the processing fluid discharged from the first discharge channel 125 through the piping 251 using the temperature sensor 252, the temperature of the processing fluid flowing above the substrate S in the processing space SP can be detected. Also, by detecting the temperature of the processing fluid discharged from the second discharge channel 126 through the piping 261 using the temperature sensor 262, the temperature of the processing fluid flowing below the support tray 15 in the processing space SP can be detected. By feeding these temperature detection results back into the temperature control of heaters 209 and 229, the temperature of the processing fluid flowing in the processing space SP can be brought closer to the original target temperature.

[0086] This method is also effective when there are factors within the processing space SP that cause changes in the temperature of the processing fluid. For example, if the temperature of the heated support tray 15 is higher than the temperature of the processing fluid supplied below the support tray 15, the heating of the processing fluid may cause an upward flow within the processing space SP. A temperature sensor installed on the discharge path can detect such temperature changes, and by feeding the detection results back into the heater control, the generation of turbulence can be prevented.

[0087] The apparatus configuration shown in Figure 7 above corresponds to the piping system described in Figure 7 of Patent Document 1, with the addition of a flow path for supplying nitrogen gas. Several modifications of the piping system described in Patent Document 1 can also be applied to this embodiment by adding a flow path for supplying nitrogen gas.

[0088] Furthermore, when using gaseous CO2 as the drying gas, the piping systems described in Patent Document 1 can be used as they are. That is, by using a piping system similar to these and changing the control method of the valve opening and closing timing, the same effects as in this embodiment can be obtained. Specifically, after the support tray 15 is placed inside, a period is provided in which only the flow path for introducing the processing fluid below the support tray 15 is opened, allowing the airflow generated by the introduced pressurized gas to push the liquid on the underside of the substrate S away.

[0089] Furthermore, in the piping system 200 of the above example, the flow paths for the processing fluids in the gas phase, liquid phase, and supercritical state are separated, and the shared paths are limited to a minimum. Therefore, the temperature of the processing fluid in each state can be set individually, and each can be optimized according to the purpose of the processing. As a result, it is possible to perform the supercritical drying process under optimal conditions and dry the substrate S well. In addition, since it is not necessary to change the fluid temperature as the process progresses, it is also advantageous in terms of processing throughput.

[0090] 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, carbon dioxide is used as the processing fluid for supercritical fluid treatment, and IPA is used as the liquid for forming the liquid film. However, this is merely an example, and the chemical substances used are not limited to these.

[0091] Furthermore, the support tray 15 in the above embodiment incorporates a heater and has through holes 152 for inserting lift pins 37. However, even if at least one of these is not provided, it is possible to obtain the same effects as in the above embodiment. Therefore, the transfer of substrates from the outside does not have to be done via lift pins, and for example, an external transport device may directly place the substrates on the support tray. In this case, the transfer unit 30 can be omitted. Even in this case, it is desirable to appropriately provide through holes for allowing liquid to fall downward, or notches in the peripheral edge of the recess 153, etc., in order to prevent liquid from accumulating on the upper surface of the support tray 15, more specifically in the recess 153, due to liquid flowing down from the substrate S.

[0092] For example, in the drying gas supply process of the above embodiment, of the piping system connected to the processing chamber 12, only the flow path that supplies drying gas to the area below the support tray 15 is open, while the other introduction and discharge paths are closed. Alternatively, the valve 263 in Figure 7, which corresponds to the valve 175 in Figure 6, may also be opened to facilitate the discharge of liquid pushed out from the gap between the substrate S and the support tray 15 to the outside.

[0093] As described above with examples of specific embodiments, nitrogen gas or carbon dioxide can be used as the gas in the substrate processing method according to the present invention. High-purity nitrogen with low oxygen and water vapor content can be used, and it has little adverse effect on the substrate itself, making it suitable as a gas for this application. On the other hand, carbon dioxide has a low critical point and can be used as a supercritical fluid. Therefore, the present invention can be implemented without adding equipment configurations for introducing other gases.

[0094] Furthermore, these gases may be introduced into the internal space in a preheated state. The gas of the present invention, supplied for the purpose of pushing out liquid adhering to the underside of the substrate by forming an airflow, does not need to have enough heat to evaporate the liquid. On the other hand, a decrease in temperature inside the chamber due to gas flow reduces the stability of subsequent processing by the supercritical fluid. For this reason, introducing a preheated gas contributes to stabilizing the temperature inside the chamber.

[0095] Furthermore, in this invention, the portion of the support tray on which the substrate is placed may be provided with vertical through-holes. These through-holes may be for inserting lift pins for placing the substrate onto the support tray. With such a configuration, the pressurized gas introduced below the support tray reaches the bottom surface of the substrate through the through-holes, thereby enhancing the liquid removal effect on the bottom surface of the substrate.

[0096] For example, the upper surface of the support tray may be provided with a recess that has a planar size larger than the planar size of the substrate and accommodates the substrate, and through holes may be provided inside the recess. In this case, the position of the through holes will be directly below the substrate on which it is placed, making it possible to effectively send pressurized gas to the underside of the substrate. [Industrial applicability]

[0097] This invention can be applied to all types of substrate processing apparatus that use supercritical fluids to process substrates. In particular, it can be suitably applied to substrate drying processes in which substrates such as semiconductor substrates are dried using supercritical fluids. [Explanation of Symbols]

[0098] 1. Substrate processing device 12 Processing Chamber 13 Lid 15 Support tray 37 Lift pins 57 Fluid supply section 152 Through hole 153 Indentation S substrate SP Processing Space

Claims

1. A step of placing a substrate with liquid applied to its upper surface onto a flat support tray having through holes that penetrate between its upper and lower surfaces, thereby supporting the substrate in a horizontal position with a gap formed between the lower surface of the substrate and the upper surface of the support tray, The process of sealing the internal space by accommodating the support tray in the internal space of the chamber such that the support tray divides the internal space vertically, A step of introducing pressurized gas towards the gap between the lower surface of the support tray and the bottom surface of the internal space, thereby generating an airflow that flows from the lower side of the support tray through the through hole into the gap due to a pressure gradient from the lower side to the upper side of the support tray, A step of introducing a supercritical fluid into the internal space and processing the substrate with the supercritical fluid. A substrate processing method comprising:

2. The substrate processing method according to claim 1, wherein the gas is nitrogen gas.

3. The substrate processing method according to claim 2, wherein the heated nitrogen gas is introduced into the internal space.

4. The substrate processing method according to claim 1, wherein the supercritical processing fluid is carbon dioxide.

5. The substrate processing method according to claim 4, wherein the gas is carbon dioxide.

6. The substrate processing method according to any one of claims 1 to 5, wherein the through hole is provided in the portion of the support tray on which the substrate is placed.

7. The substrate processing method according to claim 6, wherein the substrate is placed on the support tray by raising and lowering a lift pin inserted through the through hole.

8. The substrate processing method according to claim 7, wherein the upper surface of the support tray is provided with a recess having a planar size larger than the planar size of the substrate and for accommodating the substrate, and the through hole is provided inside the recess.

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