Substrate processing method, substrate processing apparatus, and storage medium
The substrate processing method forms a protective liquid film and uses supercritical drying to prevent particle adhesion, enhancing the drying process for semiconductor wafers.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOKYO ELECTRON LTD
- Filing Date
- 2023-06-27
- Publication Date
- 2026-06-17
Smart Images
Figure 0007875278000001 
Figure 0007875278000002 
Figure 0007875278000003
Abstract
Description
Technical Field
[0001] The present disclosure relates to a substrate processing method, a substrate processing apparatus, and a storage medium.
Background Art
[0002] In the manufacturing process of semiconductor devices that form a stacked structure of integrated circuits on the surface of a substrate such as a semiconductor wafer (hereinafter referred to as a wafer), liquid processing such as chemical solution cleaning or wet etching is performed. When removing liquids or the like adhering to the surface of the wafer by such liquid processing, in recent years, a drying method using a processing fluid in a supercritical state has been increasingly used (see, for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
[0004] The present disclosure provides a technique capable of suppressing the adhesion of particles onto a substrate.
[0005] A substrate processing method according to an embodiment of the present disclosure includes a liquid film forming step of supplying a protective liquid for protecting a pattern on the surface of the substrate to the surface of the substrate after a liquid processing step with a processing liquid to form a liquid film of the protective liquid covering the surface of the substrate, a substrate loading step of loading the substrate into a processing container in a state where the liquid film of the protective liquid is formed after the liquid film forming step, and after the substrate loading step, supplying a pressurized processing fluid to the processing container and maintaining the pressure in the processing container at a pressure at which the processing fluid maintains a supercritical state while supplying the pressurized processing fluid to the processing container to remove the protective liquidThe process includes a substrate drying step of replacing the substrate with the processing fluid and discharging the processing fluid from the processing container to dry the substrate, and a back surface cleaning step of supplying a cleaning liquid to the back surface of the substrate to clean the back surface of the substrate, wherein the back surface cleaning step is performed at least while the liquid film forming step is being carried out.
[0006] According to the embodiments described above in this disclosure, the adhesion of particles to the substrate can be suppressed. [Brief explanation of the drawing]
[0007] [Figure 1] This is a schematic cross-sectional view of a substrate processing system according to one embodiment of a substrate processing apparatus. [Figure 2] This is a schematic longitudinal cross-sectional view of a liquid treatment unit included in a substrate processing system. [Figure 3] This is a schematic longitudinal cross-sectional view of a supercritical drying unit included in a substrate processing system. [Figure 4A-4L] This is a schematic diagram illustrating the series of processes performed in the liquid processing unit. [Figure 5] This is a schematic diagram showing how the processing liquid supplied to the surface of the substrate flows to the back surface. [Modes for carrying out the invention]
[0008] The configuration of a substrate processing system 1 according to one embodiment of a substrate processing apparatus will be briefly described below with reference to Figure 1. For the sake of simplicity, an XYZ Cartesian coordinate system (see the lower left of Figure 1) will be set and referred to as appropriate.
[0009] <Overall configuration of the substrate processing system> As shown in Figure 1, the substrate processing system 1 includes an input / output station 2 and a processing station 3.
[0010] The loading / unloading station 2 includes a load port 11 and a transport block 12. Multiple carriers C are placed on the load port 11. Each carrier C accommodates multiple substrates W (e.g., semiconductor wafers) in a horizontal position with vertical spacing between them.
[0011] The transport block 12 is equipped with a transport device 13 and a transfer unit 14. The transfer unit 14 has an unprocessed substrate placement section for temporarily placing one or more unprocessed substrates W (substrates W before processing at the processing station 3) and a processed substrate placement section for temporarily placing one or more processed substrates W (substrates W after processing at the processing station 3). The transport device 13 can transport substrates W between any carrier C placed on the load port 11 and the transfer unit 14.
[0012] The processing station 3 comprises a transport block 4 and a pair of processing blocks 5 located on either side of the transport block 4 in the Y direction. Each processing block 5 is equipped with a liquid processing unit 100, a supercritical drying unit 200, and a processing fluid supply cabinet 19. In this embodiment, the liquid processing unit 100 and the supercritical drying unit 200 are single-wafer processing units. The processing fluid necessary for processing is supplied to the liquid processing unit 100 and the supercritical drying unit 200 from the processing fluid supply cabinet 19.
[0013] The transport block 4 comprises a transport area 15 and a transport device 16 located within the transport area 15. The transport device 16 can transport the substrate W between the transfer unit 14, an arbitrary liquid processing unit 100, and an arbitrary supercritical drying unit 200.
[0014] Each processing block 5 may have a multilayer (e.g., three-layer) structure. In this case, each layer is provided with one liquid processing unit 100, one supercritical drying unit 200, and one processing fluid supply cabinet 19. In this case, one transport device 16 may have access to the liquid processing units 100 and supercritical drying units 200 of all layers.
[0015] The substrate processing system 1 includes a control device 6. The control device 6 is, for example, a computer and includes an arithmetic processing unit 61 and a storage unit 62. The arithmetic processing unit 61 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input / output ports, and various circuits. The CPU of such a microcomputer controls the transport devices 13, 16, the liquid processing unit 100, the supercritical drying unit 200, and the processing fluid supply cabinet 19, etc., by reading and executing a program stored in the ROM. Such a program may have been recorded on a storage medium (non-temporary storage medium) that is readable by the computer and installed from that storage medium to the storage unit 62 of the control device 6. Examples of storage media that are readable by the computer include hard disks (HDs), flexible disks (FDs), compact disks (CDs), magnetic optical disks (MOs), and memory cards. The storage unit 62 is implemented by semiconductor memory elements such as RAM and flash memory, or by storage devices such as hard disks and optical disks.
[0016] Next, we will briefly explain the transport flow of the substrate W in the substrate processing system 1 described above.
[0017] An external transport robot (not shown) places a carrier C containing unprocessed substrates W onto the load port 11. A transport device 13 removes one substrate W from the carrier C and transports it to the transfer unit 14. A transport device 16 removes the substrate W from the transfer unit 14 and transports it to the liquid processing unit 100.
[0018] In the liquid processing unit 100, liquid processing consisting of a plurality of steps is performed. Although the details of the liquid processing will be described later, in the final step, a liquid film of IPA (also called an IPA paddle) with a predetermined film thickness is formed on the surface of the substrate W.
[0019] Next, the substrate W with an IPA paddle formed on its surface is taken out from the liquid processing unit 100 by the transfer device 16 and carried into the supercritical drying unit 200. In the supercritical drying unit 200, the substrate W is dried by using the supercritical drying technique according to the procedure described later. Since the surface tension that can cause pattern collapse does not act on the pattern, the supercritical drying technique can be advantageously used for drying a substrate on which a fine and high aspect ratio pattern is formed. Then, the transfer device 16 takes out the dried substrate W from the supercritical drying unit 200 and carries it into the delivery unit 14. The transfer device 13 takes out this substrate W from the delivery unit 14 and accommodates it in the original carrier C placed on the load port 11. Thus, a series of processes for one substrate is completed.
[0020] <Liquid Processing Unit> Next, the configuration of the liquid processing unit 100 will be described with reference to FIG. 2. [[ID=!2]]
[0021] The liquid processing unit 100 includes a chamber 120, a substrate holding and rotating mechanism 130, a first processing fluid supply unit 140, a second processing fluid supply unit 150, and a recovery cup 160.
[0022] The chamber 120 houses the substrate holding and rotating mechanism 130 and the recovery cup 160. An FFU (Fan Filter Unit) 121 is provided on the ceiling of the chamber 120. The FFU 121 forms a downflow in the chamber 20.
[0023] The substrate holding and rotating mechanism 130 comprises a substrate holding section 131, a support column (rotating shaft) 132, and a rotation drive section 133. The substrate holding section 131 is configured as a mechanical chuck having a disc-shaped base 131a and a plurality of gripping claws 131b provided at circumferential intervals on the outer edge of the base 131a. The substrate holding section 131 holds the substrate W horizontally with the gripping claws 131b. When the gripping claws 131b grip the substrate, a gap is formed between the upper surface of the base 131a and the lower surface of the substrate W.
[0024] The support column 132 is a hollow member extending in the vertical direction. The upper end of the support column 132 is connected to the base 131a. For example, a rotary drive unit 133 consisting of an electric motor rotates the support column 132, causing the substrate holding unit 131 and the substrate W held therein to rotate around the vertical axis.
[0025] The collection cup 160 is positioned to surround the substrate holder 131. The collection cup 160 collects the processing liquid that is scattered from the substrate W, which is held and rotated by the substrate holder 131. A drain port 161 is formed at the bottom of the collection cup 160. The processing liquid collected by the collection cup 160 is discharged to the outside of the liquid processing unit 100 through the drain port 161. An exhaust port 162 is formed at the bottom of the collection cup 160. The internal space of the collection cup 160 is drawn in through the exhaust port 162. The gas supplied from the FFU 121 is drawn into the collection cup 160 and then discharged to the outside of the liquid processing unit 100 through the exhaust port 162.
[0026] The first processing fluid supply unit 140 supplies various processing fluids (liquids, gases, gas-liquid mixed fluids, etc.) to the upper surface of the substrate W held by the substrate holding unit 131 (the surface of the substrate W on which the device is formed). The first processing fluid supply unit 140 has one or more surface nozzles 141 that discharge the processing fluid toward the surface of the substrate W. The number of surface nozzles 141 is limited to the number necessary to perform the processing carried out by the liquid processing unit 100. Figure 2 shows five surface nozzles 141, but the number is not limited to this.
[0027] The first processing fluid supply unit 140 has one or more (two in the illustrated example) nozzle arms 142. Each nozzle arm 142 carries at least one of a plurality of surface nozzles 141. Each nozzle arm 142 can move the surface nozzle 141 it carries between a position approximately directly above the rotation center of the substrate W (processing position) and a retracted position outside the upper end opening of the recovery cup 160 (home position).
[0028] Each surface nozzle 141 is supplied with processing fluid from a corresponding processing fluid supply mechanism 143. The processing fluid supply mechanism 143 can consist of a processing fluid supply source such as a tank, cylinder, or factory pump, a supply pipeline that supplies processing fluid (processing liquid or processing gas) from the processing fluid supply source to the surface nozzles 141, and flow rate control equipment such as an on-off valve and a flow rate control valve provided in the supply pipeline. A drain pipeline can be connected to the supply pipeline to discharge processing fluid (especially processing liquid) that remains in the surface nozzles 141 and the supply pipeline in its vicinity. Such processing fluid supply mechanisms 143 are widely known in the field of semiconductor manufacturing equipment, and their structural illustrations and detailed descriptions are omitted. A liquid receiver (not shown) is provided so that dummy dispensing is possible when each surface nozzle 141 is in the retracted position.
[0029] The second processing fluid supply unit 150 supplies various processing fluids (processing liquid, processing gas, etc.) to the underside of the substrate W held by the substrate holding unit 131 (usually the back surface of the substrate W where no devices are formed). The second processing fluid supply unit 150 has one or more (two in the illustrated example) back nozzles 151 that discharge the processing fluid toward the underside of the substrate W. As schematically shown in Figure 2, the processing liquid supply pipe 152 extends vertically inside the hollow support column 132. The upper end openings of each of the two flow paths extending vertically within the processing liquid supply pipe 152 serve as back nozzles 151. The processing liquid supply pipe 152 is installed inside the support column 132 so as to remain in a non-rotating state even when the substrate holding unit 131 and the support column 132 are rotating.
[0030] Each of the rear nozzles 151 is supplied with processing fluid from the corresponding processing fluid supply mechanism 153. The processing fluid supply mechanism 153 has the same configuration as the processing fluid supply mechanism 143 for the front nozzles 141 described above.
[0031] The second processing fluid supply unit 150 is further configured to supply a drying gas to the space below the substrate W (more specifically, the space between the back surface of the substrate W and the disc-shaped base 131a of the substrate holding unit 131). This configuration can be realized by providing a gas supply path (not shown) similar to the flow path for supplying the processing liquid within the processing liquid supply pipe 152, or by using the gap between the outer surface of the processing liquid supply pipe 152 and the inner surface of the support column 132 and the base 131a as a gas supply path. A gas with low humidity and low oxygen concentration is preferred as the drying gas, and nitrogen (N2) gas can be used. Such a drying gas can also be supplied from the processing fluid supply mechanism 153.
[0032] It is known that the recovery cup 160 is equipped with multiple switchable flow paths and corresponding drain ports 161, allowing different types of liquids (acids, alkalis, organic materials) to be discharged via different routes. It is also known that the exhaust port 162 is equipped with a switching mechanism to allow different types of liquids (acids, alkalis, organic materials) to be discharged to different destinations. For the sake of simplicity, the diagrams omit the illustrations of the configurations related to these functions.
[0033] <Supercritical drying unit> Next, the supercritical drying unit 200 will be described with reference to Figure 3. The supercritical drying unit 200 includes a processing container 211 and a substrate holding tray 212 (hereinafter simply referred to as "tray 212") that holds the substrate W within the processing container 211.
[0034] The tray 212 has a lid portion 213 that closes an opening 211C provided in the side wall of the processing container 211, and a horizontally extending substrate holding portion 214 integrally connected to the lid portion (lid body) 213. The substrate holding portion 214 has a plate 215 and a plurality of support pins 216 provided on the upper surface of the plate 215. The substrate W is placed horizontally on the support pins 216 with its surface (the surface on which the device or pattern is formed) facing upward. When the substrate W is placed on the support pins 216, a gap 217 is formed between the upper surface of the plate 215 and the lower surface (back surface) of the substrate W.
[0035] The plate 215 has a plurality of through holes 218 that penetrate vertically through it. The plurality of through holes 218 serve to allow the processing fluid supplied to the space below the plate 215 to flow into the space above the plate 215. Some of the plurality of through holes 218 also serve to allow the passage of lift pins (shown in Figure 1, directly below the tray 212 but hidden from view by the tray 212) that transfer the substrate W between the substrate holding portion 214 of the tray 212 (see Figure 1) pulled out from the processing container 211 and the transfer device 16 (see Figure 1).
[0036] The tray 212 can be moved horizontally (in the X direction) between a closed position (the position shown in Figure 3) and an open position (the position shown in Figure 1) by a tray movement mechanism 212M (schematically shown only in Figure 1).
[0037] In the closed position of the tray 212, the substrate holding portion 214 is located within the internal space of the processing container 211, and the lid portion 213 closes the opening 211C in the side wall of the processing container 211. In the open position of the tray 212, the substrate holding portion 214 is outside the processing container 211 (see Figure 1), and the substrate W can be transferred between the substrate holding portion 214 and a substrate transport arm (not shown) via the aforementioned lift pin.
[0038] When the tray 212 is in the closed position, the plate 215 divides the internal space of the processing container 211 into an upper space 211A above the plate 215 where the substrate W is located during processing, and a lower space 211B below the plate 215. However, the upper space 211A and the lower space 211B are not completely separated; for example, the through holes 218, the elongated holes 219, and the gaps between the periphery of the plate 215 and the inner wall surface of the processing container 211 also connect the upper space 211A and the lower space 211B.
[0039] The processing container 211 is provided with a first discharge section 221 and a second discharge section 22. The first discharge section 221 and the second discharge section 22 discharge the processing fluid (carbon dioxide in this example (hereinafter also referred to as "CO2" for simplicity)) supplied from a supercritical fluid (processing fluid in a supercritical state) supply source (not shown) into the internal space of the processing container 211.
[0040] The first discharge section 221 is located below the plate 215 of the tray 212 when it is in the closed position. The first discharge section 221 discharges CO2 (processing fluid) into the lower space 211B toward the lower surface (upward) of the plate 215.
[0041] The second discharge unit 22 is positioned in front of the substrate W, which is placed on the substrate holding unit 214 of the tray 212 in the closed position (at a position advanced in the positive X direction). The second discharge unit 22 supplies CO2 into the upper space 211A.
[0042] The second discharge section 22 is composed of a rod-shaped nozzle body. More specifically, the second discharge section 22 is formed by drilling a plurality of discharge ports 22b into a tube 22a that extends in the width direction (Y direction) of the substrate W. The plurality of discharge ports 22b are arranged, for example, at equal intervals in the Y direction. Each discharge port 222b supplies CO2 into the upper space 212A toward the opening 211C (generally in the negative X direction).
[0043] The processing container 211 is further provided with a fluid discharge section 224 for discharging the processing fluid from the internal space of the processing container 211. The fluid discharge section 224 is configured as a header having substantially the same configuration as the second discharge section 22. In detail, the fluid discharge section 224 is formed by drilling a plurality of outlets 224b into a horizontally extending pipe 224a. The plurality of outlets 224b are arranged at equal intervals, for example, in the Y direction. Each outlet 224b faces upward and towards the elongated holes 219 formed in the plate 215.
[0044] As indicated by arrow F in Figure 1, CO2 flows through the region above the substrate W in the upper space 211A, then flows into the lower space 211B through a connecting passage (or an elongated hole 219 formed in the plate 215) provided on the periphery of the plate 215, and is then discharged from the fluid discharge section 224.
[0045] The processing unit 210 is provided with a locking mechanism 225 which includes a bolt-shaped locking member 225C for fixing the tray 212 in the closed position, and a lifting device 225B for raising and lowering the locking member 225C between a locked position (the position shown in Figure 3) and an unlocked position lowered from there.
[0046] <Supercritical drying treatment> The following is a brief explanation of the processes performed in the supercritical drying unit 200.
[0047] [Circuit board delivery process] In the liquid treatment unit 100, the substrate W, on which IPA paddles have been formed on its surface, is removed from the liquid treatment unit 100 by the transport device 16 in the transport area 15 and transported into the supercritical drying unit 200. Inside the supercritical drying unit 200, the tray 212 is in the open position (as shown in Figure 1), and the aforementioned lift pin (not shown) is passed through a through hole (not shown) formed in the substrate holding portion 214 of the tray 212, with the tip of the lift pin positioned above the substrate holding portion 214. The transport device 16 places the substrate W on the lift pin, and then the lift pin descends, placing the substrate W on the tray 212. Next, the tray 212 moves to the closed position, the substrate W is placed inside the processing container 211, and the inside of the processing container 211 is sealed. In this state, the supercritical drying process is performed.
[0048] [Pressure Boosting Process] First, a boosting process is performed.
[0049] CO2 (processing fluid) supplied from the supercritical processing fluid source is discharged from the first discharge port 221 into the lower space 211B of the processing container 211. Immediately after the start of CO2 supply, the pressure inside the processing container 211 is atmospheric pressure, so gaseous CO2 is discharged from the first discharge port 221 at high velocity. After its momentum is weakened by colliding with the lower surface of the plate 215, the CO2 flows into the upper space 211A inside the processing container 211 through the through holes 218 and the elongated holes 219, or through the gap between the periphery of the plate 215 and the inner wall surface of the processing container 211. As CO2 flows in, the internal pressure inside the processing container 211 gradually increases.
[0050] When the pressure inside the processing container 211 exceeds the critical pressure of CO2 (approximately 8 MPa), the CO2 present inside the processing container 211 (CO2 not mixed with IPA) becomes supercritical. When the CO2 inside the processing container 211 becomes supercritical, the IPA on the substrate W begins to dissolve into the supercritical CO2. The discharge of CO2 from the first discharge unit 221 is continued, further increasing the pressure inside the processing container 211.
[0051] [Distribution process] When the pressure inside the processing container 211 reaches a pressure (supercritical state guarantee pressure (approximately 16 MPa)) that guarantees the mixed fluid (CO2 + IPA) on the substrate W will be maintained in a supercritical state, regardless of the IPA concentration in the mixed fluid and the temperature of the mixed fluid, the discharge of CO2 from the first discharge section 221 is stopped, the discharge of CO2 from the second discharge section 22 is started, and the discharge of CO2 from the fluid discharge section 224 is also started. By controlling the discharge flow rate from the fluid discharge section 224, CO2 is circulated inside the processing container 211 while the pressure inside the processing container 211 is maintained at the supercritical state guarantee pressure. In the circulation process, the supercritical CO2 supplied into the processing container 211 from the second discharge section 22 flows over the upper region of the substrate and is then discharged from the fluid discharge section 24 (see arrow F in Figure 3). At this time, a laminar flow of supercritical CO2 is formed inside the processing container 211, flowing approximately parallel to the surface of the substrate W. When exposed to a laminar flow of supercritical CO2, the IPA in the mixed fluid (IPA + CO2) on the surface of the substrate W is replaced by supercritical CO2. Ultimately, almost all of the IPA on the surface of the substrate W is replaced by supercritical CO2.
[0052] [Discharge process] Once the replacement of IPA with supercritical CO2 is complete, the supply of CO2 to the processing container 211 is stopped, and the inside of the processing container 211 is connected to the atmosphere of the air via the fluid discharge section 224. As a result, the pressure inside the processing container 211 decreases to atmospheric pressure. Consequently, the supercritical CO2 that was in the pattern of the substrate W turns into a gas and separates from the pattern, and the gaseous CO2 is discharged from the processing container 211. With this, the drying of the substrate W (substrate drying process) is completed.
[0053] [Substrate unloading process] The tray 212 on which the dried substrate W is placed is moved to the open position, and the substrate is unloaded from the supercritical drying unit 200 using the aforementioned lift pins and transport device 16 (not shown) in the reverse order of the substrate loading process.
[0054] <Liquid treatment> Next, a series of processes performed in the liquid processing unit 100 will be described. In the following explanation, we will proceed under the assumption that the liquid processing unit 100 has the following configuration. - The first processing fluid supply unit 140 is equipped with two nozzle arms 142, one of which will be referred to as "arm R" and the other as "arm L". - The tip of arm R is equipped with a surface nozzle 141 (also called "surface nozzle F1") that selectively discharges HF (hydrofluoric acid) and DIW (pure water), and a surface nozzle 141 (also called "surface nozzle F2") that discharges IPA (isopropyl alcohol). - The tip of arm L is equipped with a surface nozzle 141 (also called "surface nozzle F3") for discharging DIW and another surface nozzle 141 (also called "surface nozzle F4") for discharging a water-repellent liquid (e.g., organic silane). - The second processing fluid supply unit 150 includes a back nozzle 151 (also called "back nozzle B1") for discharging DIW and a back nozzle 151 (also called "back nozzle B2") for discharging IPA. Both back nozzles B1 and B2 are configured to discharge liquid so that the liquid lands at a position slightly away from the center of the back surface of the substrate W (the rotation center of the substrate). One of the back nozzles B1 and B2 may discharge liquid so that the liquid lands at the rotation center of the substrate W, while the other discharges liquid so that the liquid lands at a position slightly away from the rotation center of the substrate W. In either case, the back nozzles B1 and B2 discharge liquid so that the liquid lands at the "center" of the substrate as defined later.
[0055] The following describes each process. In the operation diagrams (Figures 4A to 4L) illustrating each process, for the sake of simplicity, the reference numerals "R" and "L" will be used for the nozzle arm 142, "F1," "F2," "F3," and "F4" for the surface nozzle 141, and "B1" and "B2" for the back nozzle 151. In Figures 4A to 4L, the surface nozzle 141 located outside the substrate W should be understood as being in the home position (standby position).
[0056] [Chemical cleaning process] The substrate W, transported to the liquid processing unit 100 by the transport device 16, is held in a horizontal position by the substrate holding section 131 of the substrate holding and rotating mechanism 130. The substrate W is then rotated around its vertical axis by the substrate holding and rotating mechanism 130. The rotation of the substrate W continues until the series of processes is completed, with the rotation speed being changed as needed.
[0057] In this state, as shown in Figure 4A, the surface nozzle F1 of arm R is positioned directly above the center of the substrate W, and the chemical solution HF is supplied so that it lands on the center of the substrate W. The center of the substrate W is not limited to the center of the substrate (center of rotation), but is a concept that also includes a position on the surface of the substrate W that is slightly away from the center of the substrate W, and where, after the liquid (HF) is landed, the force of the landing causes the liquid to spread towards the center of the substrate. Due to centrifugal force, HF spreads to cover the entire surface of the substrate W and flows towards the periphery of the substrate W. As a result, the silicon oxide film on the surface of the substrate W is removed by HF.
[0058] It is preferable to discharge DIW from the back nozzle B1 while the front nozzle F1 is supplying HF to the center of the substrate W. The DIW that has settled in the center of the back surface of the substrate spreads out towards the periphery of the substrate W due to centrifugal force, covering the entire back surface of the substrate W. In other words, the entire back surface of the substrate W is covered with a liquid film of DIW. This prevents HF on the surface of the substrate W from flowing around to the back surface via the periphery (APEX) of the substrate W, and prevents contamination of the back surface of the substrate W by contaminants derived from reaction products, for example.
[0059] Alternatively, prior to this chemical cleaning process, a pre-wetting treatment may be performed in which DIW is supplied from the surface nozzle F1 of the arm R to the center of the surface of the rotating substrate W, thereby covering the entire surface of the substrate with a liquid film of DIW.
[0060] [Rinsing process] Next, as shown in Figure 4B, while maintaining the position of the surface nozzle F1, the processing liquid discharged from the surface nozzle F1 is switched from HF to DIW. The DIW supplied to the center of the substrate W spreads out to cover the entire surface of the substrate W due to centrifugal force and flows towards the periphery of the substrate W. As a result, any HF remaining on the surface of the substrate W and reaction products generated in the chemical cleaning process are washed away from the surface of the substrate W.
[0061] It is preferable to continue discharging DIW from the back nozzle B1 until the rinsing has progressed to a certain extent and all HF and reaction products generated in the chemical cleaning process remaining on the surface of the substrate W have been sufficiently removed.
[0062] Next, as shown in Figure 4C, while continuing to discharge DIW from surface nozzle F1, the surface nozzle F3 of arm L is positioned above the substrate W and discharge of DIW from surface nozzle F3 begins. Then, while continuing to discharge DIW from surface nozzle F3, surface nozzle F3 is brought closer to surface nozzle F1. At this time, when arm L and arm R get close, arm R is retracted to prevent arm L from colliding with arm R. That is, slightly before surface nozzle F3 supported on arm L reaches directly above the center of the substrate W, surface nozzle F1 supported on arm R is retracted to a position slightly away from directly above the center of the substrate W. As shown in Figure 4D, when surface nozzle F3, which is discharging DIW, reaches directly above the center of the substrate W, discharge of DIW from surface nozzle F1 is stopped. The position of surface nozzle F1 and the arm R supporting it (also called the "temporary retracted position") is maintained.
[0063] [IPA replacement process (DIW→IPA)] Next, as shown in Figure 4E, while continuing to discharge DIW from surface nozzle F3 located directly above the center of substrate W, discharge of IPA is started from surface nozzle F2 supported on arm R, which is in a temporarily retracted position. Then, while continuing to discharge DIW from surface nozzle F3, surface nozzle F2 is moved closer to surface nozzle F3. At this time, when arm R and arm L get close, arm L is retracted to prevent arm R from colliding with arm L. That is, slightly before surface nozzle F2 supported on arm R reaches directly above the center of substrate W, surface nozzle F1 supported on arm L is moved from directly above the center of substrate W toward the periphery of substrate W. As shown in Figure 4F, when surface nozzle F2, which is discharging IPA, reaches directly above the center of substrate W, surface nozzle F2 is stopped at that position, and discharge of DIW from surface nozzle F3 is stopped. After that, surface nozzle F3 and the arm L supporting it are moved to the home position and left there in standby.
[0064] By continuously discharging IPA from a surface nozzle F2 located directly above the center of the substrate W for a predetermined time, the DIW on the surface of the substrate W (including the inside of recesses in the patterns formed on the surface) is replaced with IPA. Because the affinity between the water-repellent agent used in the next water-repellent treatment step and the DIW is low, it is difficult to directly replace the DIW with the water-repellent agent. Therefore, the procedure involves first replacing the DIW with IPA, which has a high affinity for DIW, and then replacing it with a water-repellent agent that has a high affinity for IPA.
[0065] Furthermore, in the subsequent water-repellent treatment process, the water-repellent agent (SM) supplied to the surface of the substrate W may wrap around to the back edge of the substrate W via the periphery (APEX) (see Figure 5). Such wrapping can occur to varying degrees with any liquid (PL). At this time, if the DIW supplied to the back surface of the substrate W in the rinsing process remains undried, for example, in the area enclosed by the dashed line in Figure 5, the water-repellent agent and moisture will react, causing stains (deposits), which can become a cause of particles during the subsequent supercritical drying process. To prevent this phenomenon, it is preferable to supply the aforementioned drying gas (in this case, nitrogen gas) to the back surface of the substrate in this IPA replacement process (DIW → IPA). By supplying a drying gas and removing the moisture remaining on the back surface of the substrate W, the occurrence of the above-mentioned stains (deposits) can be prevented. Also, in the IPA replacement process, the IPA supplied to the surface of the substrate W may wrap around to the back edge of the substrate W via the periphery (APEX). The IPA adhering to the periphery of the back surface promotes the circulation of the water-repellent agent supplied to the surface of the substrate W during the water-repellent treatment process to the back surface. In other words, when the water-repellent agent comes into contact with the IPA adhering to the periphery of the back surface, it is drawn into the IPA. This is undesirable from the viewpoint of suppressing the adhesion of substances derived from the water-repellent agent to the back surface. From this viewpoint as well, it is preferable to supply the aforementioned drying gas to the back surface of the substrate during the IPA substitution process (DIW → IPA), and from this viewpoint as well, it is preferable to continue discharging the drying gas until just before the start of the next switching process (IPA → water-repellent agent).
[0066] [Switching process (IPA → water repellent)] Next, while continuing to discharge IPA from surface nozzle F2, arm L is moved to bring surface nozzle F4 closer to surface nozzle F2. At this time, when arm L and arm R are close together, arm R is moved to prevent arm L from colliding with arm R. In other words, surface nozzle F2 is moved away from the position directly above the center of the substrate W. At almost the same time, discharge of the hydrophobic agent (labeled "SM" in the figure) is started from surface nozzle F4 (see Figure 4G).
[0067] When the surface nozzle F4, which is dispensing the hydrophobic agent, reaches directly above the center of the substrate W, the surface nozzle F4 is stopped at that position. Almost simultaneously, the dispensing of IPA from the surface nozzle F2 is stopped, and the surface nozzle F2 and the arm R supporting it are moved to the home position and left there in standby (see Figure 4H).
[0068] In this switching process (IPA → water repellent), as long as the surface of the substrate W remains covered with a liquid film, the timing of the start of water repellent discharge from surface nozzle F4 and the timing of the stop of IPA discharge from surface nozzle F2 do not need to be strictly defined. The start of water repellent discharge may be advanced, or the stop of IPA discharge may be delayed. However, since IPA and water repellent are generally relatively expensive chemicals, the above timings are determined in order to reduce wasteful consumption.
[0069] [Water-repellent treatment process] As shown in Figure 4H, the discharge of the water-repellent agent from the surface nozzle F4 is continued for a predetermined time, starting from the point when the surface nozzle F4, which is discharging the water-repellent agent, is positioned directly above the center of the substrate W. As a result, the IPA on the surface of the substrate W (including the inside of the recesses of the patterns formed on the surface) is replaced with the water-repellent agent. Subsequently, by continuing to discharge the water-repellent agent from the surface nozzle F4 for a predetermined time, the surface of the substrate W (including the inside of the recesses of the patterns formed on the surface) is made water-repellent to the desired level by the water-repellent agent.
[0070] For example, silylation agents can be used as water-repellent agents. Examples of silylation agents include trimethylsilyldimethylamine (TMSDMA), hexamethyldisilazane (HMDS), trimethylsilyldiethylamine (TMSDEA), dimethyl(dimethylamino)silane (DMSDMA), and 1,1,3,3-tetramethyldisilane (TMDS).
[0071] [Switching process (water repellent → IPA)] Next, as shown in Figure 4I, while continuing to discharge the water-repellent agent from the surface nozzle F4 located directly above the center of the substrate W, the arm R is moved to bring the surface nozzle F2 closer to the surface nozzle F4. At this time, when the arm R and the arm L approach each other, the arm L is moved to prevent the arm R from colliding with the arm L. In other words, the surface nozzle F4 is moved away from the position directly above the center of the substrate W. At almost the same time, the discharge of IPA from the surface nozzle F2 is started. When the surface nozzle F2, which is discharging IPA, reaches directly above the center of the substrate W, the surface nozzle F2 is stopped at that position, and at almost the same time, the discharge of the water-repellent agent from the surface nozzle F4 is stopped. The surface nozzle F4, which has stopped discharging the water-repellent agent, and the arm L that supports it are moved to the home position and left there waiting.
[0072] Furthermore, even in this switching process (water-repellent agent → IPA), as long as the state in which the surface of the substrate W is covered with a liquid film is maintained, it is not necessary to strictly define the timing of the start of IPA discharge from the surface nozzle F2 and the timing of the stop of water-repellent agent discharge from the surface nozzle F4. The timing of the start of IPA discharge may be advanced, or the timing of the stop of water-repellent agent discharge may be delayed.
[0073] [IPA liquid film formation process (IPA replacement process)] By continuing to discharge IPA from the surface nozzle F2 for a predetermined time, starting from the point when the surface nozzle F2 dispensing IPA reaches directly above the center of the substrate W, the entire surface of the substrate W is covered with a liquid IPA film, and any water-repellent agent present on the surface of the substrate W (including the inside of recesses in the patterns formed on the surface) is replaced by IPA. Note that a back surface cleaning process is performed on the back surface of the substrate W while at least the IPA liquid film formation process (liquid film formation process) is being carried out; this will be described later.
[0074] [IPA film thickness adjustment process] Next, while continuing to discharge IPA from the surface nozzle F2 located directly above the center of the substrate W, the rotation speed of the substrate W is reduced from, for example, 1000 rpm to a lower speed, for example, 300-700 rpm (see Figure 4K). Then, the rotation speed of the substrate is reduced to an extremely low final rotation speed, for example, 30 rpm, and the discharge of IPA from the surface nozzle F2 is stopped (see Figure 4L). By appropriately adjusting the final rotation speed, the thickness of the IPA paddle (liquid film) remaining on the surface of the substrate W can be adjusted. Finally, the rotation of the substrate W is stopped. With this, the series of processes performed by the liquid treatment unit 100 is completed. As a result, the pattern on the surface of the substrate W is protected by the protective liquid, IPA.
[0075] The substrate W on which the IPA paddles are formed is removed from the liquid treatment unit 100 by the transport device 16 and transported to the supercritical drying unit 200, where the substrate W is subjected to the supercritical drying treatment described above.
[0076] [Backside cleaning process (cleaning process)] The back surface cleaning process is performed at least during the execution of the IPA liquid film formation process. If the water-repellent agent supplied to the surface of the substrate W in the water-repellent treatment process flows to the back surface of the substrate W and dries (including becoming semi-dried) in the area indicated by the dashed line in Figure 5, for example, during supercritical drying, it may dissolve into the supercritical fluid (CO2, or a mixture of CO2 and IPA), potentially causing particles. In other words, in the pressurization process of the supercritical drying process described above, the CO2 discharged from the first discharge section 221 into the lower space 211B of the processing container 211 passes through the through hole 218, flows along the back surface of the substrate W, and flows into the upper space 211A after passing near the peripheral edge of the back surface of the substrate W. If substances derived from the water-repellent agent adhere to the peripheral edge of the back surface of the substrate W, these substances will dissolve into the CO2, causing particles. Furthermore, during the supercritical drying process, some of the CO2 flowing near the surface of the substrate W flows into the gap between the upper surface of the plate 215 and the back surface of the substrate W through the gap between the peripheral edge of the substrate W and the plate 215 of the tray 212. When a substance derived from the water-repellent agent attached to the peripheral edge of the back surface of the substrate W comes into contact with this flow of CO2, the substance dissolves into the CO2, causing particles. To prevent the generation of particles due to the above mechanism, a back surface cleaning process is performed to remove the water-repellent agent that has spread to the back surface of the substrate W. The back surface cleaning process will be described below.
[0077] The back surface cleaning process can be performed by supplying a cleaning solution, such as IPA, to the center of the back surface of a rotating substrate W. The cleaning solution is indicated by the reference numeral CL in Figures 4I and 4J. The cleaning solution supplied to the center of the back surface of the substrate W flows toward the periphery of the back surface due to centrifugal force, so that the entire back surface is covered with the cleaning solution. By continuing this state for a predetermined time, the back surface of the substrate W is cleaned, and in particular, water-repellent agents (or deposits derived from water-repellent agents) attached to the periphery of the back surface are removed. It is preferable that the temperature of the cleaning solution be in the medium temperature range between 20°C and 75°C. This increases the efficiency of removing water-repellent agents (in this case, silylaters).
[0078] In the back surface cleaning process, it is preferable that the flow rate of cleaning solution supplied to the back surface of the substrate W be smaller than the flow rate of IPA (protective solution) supplied to the front surface of the substrate W at the same time. This prevents the cleaning solution from flowing from the back surface to the front surface. Since the cleaning solution may contain contaminants, for example, those originating from deposits on the back surface, it is preferable to prevent the cleaning solution supplied to the back surface from flowing to the front surface from the viewpoint of preventing contamination of the surface of the substrate W.
[0079] The end of the back surface cleaning process is when the water-repellent agent that has spread to the back surface has been completely or almost completely removed (end condition 1), and there is no longer any possibility of the water-repellent agent spreading from the surface to the back surface of the substrate W (end condition 2). End condition 2 is equivalent to the water-repellent agent on the surface of the substrate W being completely or almost completely replaced by IPA. Note that "almost completely" means that even if a minute amount of water-repellent agent remains, its effect on particle generation during supercritical drying is negligible.
[0080] The time required from the start of the IPA liquid film formation process (the end of the switching process (water repellent → IPA)), that is, the time when the surface nozzle F2 dispensing IPA is positioned directly above the center of the substrate W (hereinafter, for simplicity, also referred to as "time T1") until the water repellent on the surface of the substrate W is substantially completely replaced by IPA (hereinafter, also referred to as "replacement time") is, for example, 20 seconds (this varies depending on the processing conditions). In this case, termination condition 2 is met 20 seconds after time T1.
[0081] The time required for the water-repellent agent that has seeped to the back surface to be completely or almost completely removed (hereinafter also referred to as the "back surface cleaning time") is at most about the same as the "replacement time". Therefore, the back surface cleaning process and the switching process (water-repellent agent → IPA) may be started and ended at the same time. In other words, if the back surface cleaning process is started at time T1, the back surface cleaning process may be stopped (ended) at the end of the IPA liquid film formation process (IPA replacement process) (20 seconds after time T1).
[0082] The back surface cleaning process may be started before time T1, for example, simultaneously with the start of the switching process (water repellent → IPA) or in the middle of the switching process (water repellent → IPA). By starting the back surface cleaning process earlier, the removal of the water repellent adhering to the back surface of the substrate W (especially its peripheral area) can be completed earlier, and the back surface cleaning process can be completed earlier. If the back surface drying is required, even after the IPA liquid film formation process (IPA replacement process) is completed, it is necessary to wait until the back surface is dry before proceeding to the IPA film thickness adjustment process, which is performed at a low rotation speed. For this reason, in some cases (for example, when the cleaning solution is DIW), the IPA liquid film formation process (IPA replacement process) may have to be unnecessarily extended, which can lead to problems such as an unnecessarily increased amount of IPA supplied to the surface of the substrate W and longer processing time (leading to a decrease in throughput). By starting the back surface cleaning process earlier, these problems can be solved.
[0083] It might seem that if the back surface cleaning process is completed before the IPA liquid film formation process (IPA replacement process) is finished, residual water-repellent agent on the surface of the substrate will seep to the back surface and contaminate it. However, this does not actually happen in practice. In practice, the processing time is extended to ensure that the water-repellent agent does not end up in the IPA paddle. In other words, the processing time is set to the time required to completely replace the water-repellent agent with IPA (replacement time) plus a safety margin. This means that at the end of the replacement time, the IPA on the surface of the substrate W contains no water-repellent agent at all, or only a very small amount. Even if such IPA seeps to the back surface, it will not cause any practical problems to the condition of the back surface. In other words, the back surface cleaning process can be completed at the latest by the start of the safety margin time. Therefore, it is acceptable to start the back surface cleaning process at least by the safety margin time.
[0084] Figures 4I and 4J show an example in which IPA was discharged as a cleaning solution from the back nozzle B2 during the switching process (water repellent → IPA).
[0085] When the discharge of IPA from the back nozzle B2 is stopped while the substrate W is rotating, the cleaning solution on the back of the substrate W is shaken off, and the back surface dries. If a sufficiently dry back surface is desired, after the back surface cleaning process is completed (i.e., after the discharge of cleaning solution from the back nozzle B2 is stopped), the substrate W can be rotated at a relatively high speed (e.g., 1000 rpm) for a predetermined time (e.g., about 10 seconds if the cleaning solution is IPA).
[0086] In most cases, no problems occur even if IPA adheres to the back surface of the substrate W, when it is removed from the liquid treatment unit, transferred to the supercritical treatment unit, and subjected to supercritical treatment. In fact, it may even be helpful in maintaining the IPA paddles in the treatment container of the supercritical treatment unit. For this reason, after stopping the discharge of IPA from the back surface nozzle B2, the rotation speed of the substrate W may be immediately reduced to adjust the IPA film thickness without allowing time for the back surface to dry.
[0087] The cleaning solution (CL) used in the back surface cleaning process is not limited to IPA; other cleaning solutions, such as DIW, may also be used. In this case, the cleaning solution should be discharged from the back surface nozzle L1. DIW also has roughly the same performance as IPA in removing deposits derived from water-repellent agents. However, if supercritical drying is performed with DIW adhering to the back surface of the substrate W, problems will occur in the supercritical drying results (pattern collapse, particle generation). Therefore, it is necessary to thoroughly dry the back surface before removing the substrate W from the liquid treatment unit. Drying should be done in the same way as when using IPA as the cleaning solution: after the back surface cleaning process is completed (i.e., after the discharge of DIW from the back surface nozzle B1 is stopped), the substrate W should be rotated at a relatively high speed (e.g., 1000 rpm) for a predetermined time. Drying the DIW on the back surface takes longer than drying IPA (e.g., about 40 seconds at 1000 rpm). Furthermore, to accelerate the drying of the DIW on the back side, a drying gas (nitrogen gas) may be sprayed onto the back side of the substrate W.
[0088] DIW is less expensive than IPA, offering the advantage of reduced equipment running costs. On the other hand, IPA is more volatile than DIW, which has the advantage of shortening the drying time required for the back surface. The decision of whether to use DIW or IPA as the cleaning solution for the back surface should be made considering these trade-offs. Note that some water-repellent agents can cause problems when in contact with moisture, so in the case of such water-repellent agents, it is desirable to use IPA as the cleaning solution. A mixture of DIW and IPA can also be used as the cleaning solution (CL) in the back surface cleaning process.
[0089] [experiment] Using the liquid treatment unit 100 and the supercritical drying unit 200, a test was conducted to compare the amount of particles produced by performing liquid treatment and supercritical drying on a substrate using the following four methods. <Processing Method 1 (Example)> DIW pre-wetting → chemical cleaning process (HF cleaning) → rinsing process (DIW rinse) → IPA substitution process (DIW → IPA) → switching process (IPA → water repellent) → water repellency treatment process → switching process (water repellent → IPA) → IPA film formation process (IPA substitution process) → spin drying process (supercritical drying is not used for final drying) <Processing Method 2 (Comparative Example 1)> DIW pre-wetting → chemical cleaning process (HF cleaning) → rinsing process (DIW rinse) → IPA replacement process (DIW → IPA) (no drying gas supplied to the back surface at this time) → switching process (IPA → water repellent) → water repellency treatment process → switching process (water repellent → IPA) → IPA liquid film formation process (IPA replacement process) (back surface cleaning process not performed at this time) → IPA film thickness adjustment process → supercritical drying of the substrate on which IPA paddles have been formed <Processing Method 3 (Comparative Example 2)> DIW pre-wetting → chemical cleaning process (HF cleaning) → rinsing process (DIW rinse) → IPA replacement process (DIW → IPA) (during this time, drying gas is supplied to the back surface) → switching process (IPA → water repellent) → water repellency treatment process → switching process (water repellent → IPA) → IPA liquid film formation process (IPA replacement process) (during this time, the back surface cleaning process is not performed) → IPA film thickness adjustment process → supercritical drying of the substrate on which the IPA paddles have been formed. <Processing Method 4 (Example)> DIW pre-wetting → chemical cleaning process (HF cleaning) → rinsing process (DIW rinse) → IPA replacement process (DIW → IPA) (during this time, drying gas is supplied to the back surface) → switching process (IPA → water repellent) → water repellency treatment process → switching process (water repellent → IPA) → IPA liquid film formation process (IPA replacement process) (during this time, the back surface cleaning process is performed) → IPA film thickness adjustment process → supercritical drying of the substrate on which the IPA paddles have been formed.
[0090] When the increase in the number of particles larger than 19 nm before and after processing was investigated for each substrate W, the results were 205 for processing method 1, 4301 for processing method 2, 2168 for processing method 3, and 286 for processing method 4. In processing methods 2 and 3, the particles were significantly biased to one side, which is thought to be due to reasons such as the fact that CO2 does not flow evenly in the gap between the peripheral edge of the substrate W and the plate 215 of the tray 212 in the supercritical drying apparatus (see the explanation at the beginning of the back surface cleaning process).
[0091] From the above test results, it can be seen that when water-repellent treatment is performed and supercritical drying is carried out, the number of particles increases significantly without back surface cleaning (treatment methods 2 and 3) (the estimated mechanism is as described above). However, it was confirmed that when back surface cleaning is performed (treatment method 4), the increase in particles decreases to roughly the same level as treatment method 1. Needless to say, treatment method 4, which uses supercritical drying, is overwhelmingly advantageous over treatment method 1, which uses spin drying, from the viewpoint of suppressing pattern collapse. Furthermore, by comparing treatment methods 2 and 3, it can be seen that the increase in particles can be suppressed by supplying drying gas to the back surface during the IPA substitution process (DIW → IPA).
[0092] As described above, according to the above embodiment, by performing an IPA liquid film formation process (IPA replacement process) on the surface of the substrate W and a back surface cleaning process, the amount of particles after supercritical drying can be significantly reduced.
[0093] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.
[0094] The substrate is not limited to semiconductor wafers, but may also be other types of substrates used in the manufacture of semiconductor devices, such as glass substrates or ceramic substrates.
[0095] The protective solution is not limited to IPA; an organic solvent with high affinity for water-repellent agents, high affinity for supercritical fluids used in supercritical drying, and low surface tension, such as HFE (hydrofluoroether) or a mixture of IPA and HFE, can be used instead of IPA.
[0096] In the embodiment described above, the steps prior to the first IPA substitution step (DIW → IPA) can be arbitrarily changed. For example, two or more chemical treatments may be performed before the first IPA substitution step.
[0097] The purpose of the back surface cleaning step may be other than the removal of water-repellent agents or substances derived from water-repellent agents. For example, if residues or reaction products of chemical solutions are attached to the peripheral edges of the back surface of the substrate, these can cause particles during supercritical drying, so the back surface cleaning step may be performed for the purpose of removing such substances. In other words, the back surface cleaning step can be performed for the purpose of removing deposits that may be generated on the back surface of the substrate as a result of treatment with a treatment solution (which is not limited to water-repellent agents but may be chemical solutions such as HF) performed prior to the IPA liquid film formation step.
Claims
1. A water-repellent step of supplying a water-repellent agent to the surface of a substrate to make the surface of the substrate water-repellent, and a liquid film forming step of supplying a protective liquid to the surface of the substrate after the water-repellent step to protect a pattern to form a liquid film of the protective liquid that covers the surface of the substrate, After the liquid film formation step, the substrate is brought into the processing container in a substrate loading step, with the protective liquid film formed on the substrate. After the substrate loading step, a substrate drying step is performed in which pressurized processing fluid is supplied to the processing container, maintaining the pressure inside the processing container at a pressure that allows the processing fluid to maintain a supercritical state, while supplying pressurized processing fluid to the processing container to replace the protective liquid on the substrate with the processing fluid, and then the processing fluid is discharged from the processing container to dry the substrate. The process includes supplying a cleaning solution to the back surface of the substrate for cleaning the back surface of the substrate, The aforementioned back surface cleaning step is performed at least while the aforementioned liquid film formation step is being carried out. When switching from the water-repellent process to the liquid film formation process, the supply of the protective liquid to the substrate surface is started before the supply of the water-repellent agent to the substrate surface is stopped, and at this time, the water-repellent agent and the protective liquid are supplied to the substrate surface simultaneously. The supply of the cleaning liquid in the back surface cleaning process is started when the water-repellent agent and the protective liquid are simultaneously supplied to the surface of the substrate. The back surface cleaning step is completed when the water-repellent agent that has moved from the surface of the substrate to the back surface of the substrate is removed from the back surface of the substrate, and the water-repellent agent that was on the surface of the substrate is replaced by the protective liquid. Substrate processing method.
2. The substrate processing method according to claim 1, wherein the cleaning solution is one of pure water, IPA, and a mixture of pure water and IPA.
3. The substrate processing method according to claim 1, wherein the cleaning solution is IPA and the protective solution is also IPA.
4. The substrate processing method according to claim 2 or 3, wherein the temperature of the cleaning solution supplied to the back surface of the substrate is 20°C to 75°C.
5. The substrate processing method according to claim 1, wherein when the liquid film formation step is performed on the surface of the substrate and the back surface cleaning step is performed on the back surface of the substrate, the flow rate of the protective liquid supplied to the surface is equal to or greater than the flow rate of the cleaning liquid supplied to the back surface.
6. The substrate processing method according to claim 1, wherein the protective liquid is supplied to the center of the surface of the rotating substrate, and the cleaning liquid is supplied to a position away from the center of the back surface of the rotating substrate, and at a position such that the cleaning liquid, after being applied to the back surface, spreads and reaches the center of the back surface of the substrate.
7. A substrate processing apparatus, At least one liquid processing unit, At least one supercritical drying unit, Equipped with, The aforementioned liquid processing unit is A substrate holding and rotating mechanism that holds the substrate in a horizontal position and rotates it around a vertical axis, A processing fluid supply unit comprising: at least one surface nozzle capable of supplying at least a water-repellent agent and a protective liquid to the surface of a substrate held and rotated by the substrate holding and rotating mechanism; at least one back nozzle capable of supplying at least a cleaning liquid to the back surface of the substrate held and rotated by the substrate holding and rotating mechanism; and a processing fluid supply mechanism that supplies the liquid necessary for processing to the at least one surface nozzle and the at least one back nozzle; It includes, The substrate processing apparatus further comprises a control unit that controls the operation of the liquid processing unit and the supercritical drying unit to cause the substrate processing apparatus to perform the substrate processing method described in claim 1.
8. A computer-readable storage medium storing a computer program that, when executed by a computer constituting the control unit of a substrate processing apparatus, causes the computer to control the substrate processing apparatus and execute the substrate processing method described in claim 1.