Substrate processing apparatus and substrate processing method

Abstract

To reduce a particle level of a substrate after supercritical drying.SOLUTION: A control part of a substrate processing apparatus, executes: a first step of supplying a processing fluid to a processing container via a first supply line and a first fluid discharge part in a first period when a supply of the processing fluid to the processing container is started, a pressure in the processing container is increased, and the processing fluid in the processing container becomes a supercritical state; a second step of supplying the processing fluid to the processing container via a second supply line and a second fluid discharge part at a flow rate that is larger than a flow rate of the processing fluid supplied to the first fluid discharge part in the first step, in a second period after the processing fluid in the processing container becomes the supercritical state; and a density adjusting step of reducing a difference between a density of the processing fluid existing in a region on an upstream side from a second opening and closing valve of the second supply line and a density of the processing fluid existing in the processing container, than a predetermined threshold value by a density adjusting mechanism before the termination of the first step and before the start of the second step.SELECTED DRAWING: Figure 6C

Description

[Technical field]

[0001] The present disclosure relates to a substrate processing apparatus and a substrate processing method. [Background technology]

[0002] In the manufacture of semiconductor devices in which a laminated structure of integrated circuits is formed on the surface of a substrate such as a semiconductor wafer, liquid processing such as chemical cleaning or wet etching is performed. In order to more reliably prevent the collapse of patterns that have become increasingly fine in recent years, a drying method using a processing fluid in a supercritical state has recently been used in the drying step, which is the final step of liquid processing (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication WO2023 / 013435 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides techniques that can reduce particle levels on substrates after supercritical drying. [Means for solving the problem]

[0005] According to an embodiment of the present disclosure, a processing vessel in which a substrate is processed using a processing fluid in a supercritical state, a processing fluid supply unit that supplies the processing fluid to the processing vessel, and a control unit, the processing fluid supply unit including a first fluid discharge unit that discharges the processing fluid into the processing vessel, a first step of controlling the substrate processing apparatus to supply the processing fluid to the first fluid discharge section through the first supply line by opening the first on-off valve and closing the second on-off valve at least during a first period from when the supply of the processing fluid to the processing vessel is started until the pressure in the processing vessel increases and the processing fluid in the processing vessel reaches a supercritical state, the first step of controlling the substrate processing apparatus to supply the processing fluid to the first fluid discharge section through the first supply line by opening the first on-off valve and closing the second on-off valve at least during a first period from when the supply of the processing fluid to the processing vessel is started until the pressure in the processing vessel increases and the processing fluid in the processing vessel reaches a supercritical state, and a second step of supplying the processing fluid to the second fluid discharge section via the second supply line at a flow rate greater than a flow rate of the processing fluid supplied from the first supply line to the first fluid discharge section during the first period by closing the first on-off valve and opening the second on-off valve during a second period after the processing fluid in the processing vessel has reached a supercritical state; and a density adjusting step of reducing a difference between an in-line density, defined as a density of the processing fluid present in a region upstream of the second on-off valve of the second supply line, and an in-container density, defined as a density of the processing fluid present in the processing vessel, to less than a predetermined threshold value by the density adjusting mechanism after the first supply period ends and before the second supply period begins. Effect of the Invention

[0006] According to the above embodiment of the present disclosure, particle levels of the substrate after supercritical drying can be reduced. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of a substrate processing system according to an embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of a liquid processing unit incorporated in the substrate processing system of FIG. [Diagram 3] FIG. 3 is a schematic vertical sectional view showing an example of the configuration of a supercritical drying unit incorporated in the substrate processing system of FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of the supercritical drying unit taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a piping diagram showing an example of a supply / discharge system connected to the processing vessel of the supercritical drying unit shown in FIGS. [Figure 6A-E] 6A to 6E are diagrams showing an example of the state of the supply / discharge system in each step of the supercritical drying treatment. [Figure 7] 1 is a graph showing an example of a density adjusting step (depressurizing step) and a pressure change before and after the step. [Figure 8] FIG. 13 is a piping diagram according to a modified embodiment. [Figure 9] FIG. 11 is a piping diagram according to another modified embodiment. [Figure 10] FIG. 11 is a schematic vertical sectional view showing a modified embodiment of the supercritical drying unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, with reference to the attached drawings, an embodiment of the substrate processing method and substrate processing apparatus disclosed in the present application will be described in detail. Note that the present disclosure is not limited to the following embodiment. It should be noted that the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, and the like may differ from reality. Furthermore, there may be parts in which the dimensional relationship and ratio differ between the drawings.

[0009] <Outline of the substrate processing system> First, a schematic configuration of a substrate processing system 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing a schematic configuration of a substrate processing system 1 according to an embodiment. In the following, to clarify the positional relationship, an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other are defined, and the positive direction of the Z-axis is defined as the vertical upward direction.

[0010] 1, the substrate processing system 1 includes a loading / unloading station 2 and a processing station 3. The substrate processing system 1 is an example of a substrate processing apparatus. The loading / unloading station 2 and the processing station 3 are provided adjacent to each other.

[0011] The loading / unloading station 2 includes a carrier placement section 11 and a transport section 12. A plurality of carriers C, each of which horizontally accommodates a plurality of semiconductor wafers W (hereinafter, referred to as "wafers W"), are placed on the carrier placement section 11. The wafers W are an example of a substrate.

[0012] The transfer section 12 is provided adjacent to the carrier placement section 11, and includes therein a substrate transfer device 13 and a transfer section 14. The substrate transfer device 13 includes a wafer holding mechanism that holds the wafer W. The substrate transfer device 13 is capable of moving in the horizontal and vertical directions and rotating about a vertical axis, and transfers the wafer W between the carrier C and the transfer section 14 using the wafer holding mechanism.

[0013] Processing station 3 is provided adjacent to transport section 12. Processing station 3 includes a transport section 15, a plurality of liquid processing units 16, and a plurality of supercritical drying units 17. The plurality of liquid processing units 16 and the plurality of supercritical drying units 17 are provided side by side on both sides of transport section 15. The arrangement and number of liquid processing units 16 and supercritical drying units 17 are not limited to those shown in FIG.

[0014] The transfer section 15 includes therein a substrate transfer device 18. The substrate transfer device 18 includes a wafer holding mechanism that holds the wafer W. The substrate transfer device 18 is capable of moving in the horizontal and vertical directions and rotating about a vertical axis, and transfers the wafer W between the delivery section 14, the liquid processing unit 16, and the supercritical drying unit 17 using the wafer holding mechanism.

[0015] The liquid processing unit 16 performs a series of liquid processes (such as wet etching and cleaning using chemicals, and rinsing) on ​​the wafer W, and then performs a protective liquid film forming process to form a protective liquid film such as IPA as a final process. An example of the configuration of the liquid processing unit 16 will be described later.

[0016] The supercritical drying unit 17 performs a supercritical drying process on the wafer W on whose surface the protective liquid film has been formed by the liquid processing unit 16. An example of the configuration of the supercritical drying unit 17 will be described later.

[0017] The substrate processing system 1 further includes a control device 4. The control device 4 is, for example, a computer, and includes a control unit 19 and a storage unit 20.

[0018] The control unit 19 includes a microcomputer and various circuits having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), input / output ports, etc. The CPU of the microcomputer realizes the control described below by reading and executing a program stored in the ROM.

[0019] Such a program may be recorded on a computer-readable recording medium and installed from the recording medium into the storage unit 20 of the control device 4. Examples of computer-readable recording media include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnet optical disk (MO), and a memory card.

[0020] The storage unit 20 is realized by, for example, a semiconductor memory element such as a RAM or a flash memory, or a storage device such as a hard disk or an optical disk.

[0021] In the substrate processing system 1 configured as described above, first, the substrate transfer device 13 in the loading / unloading station 2 removes the wafer W from the carrier C placed on the carrier placement part 11, and places the removed wafer W on the delivery part 14. The wafer W placed on the delivery part 14 is then removed from the delivery part 14 by the substrate transfer device 18 in the processing station 3, and carried into the liquid processing unit 16.

[0022] The wafer W carried into the liquid processing unit 16 is subjected to a predetermined liquid processing by the liquid processing unit 16, and then carried out from the liquid processing unit 16 by the substrate transfer device 18 in a state in which a protective liquid film of IPA or the like is formed on the surface of the wafer W. The wafer W carried out from the liquid processing unit 16 is carried into the supercritical drying unit 17 by the substrate transfer device 18, and is subjected to a supercritical drying process by the supercritical drying unit 17.

[0023] The wafer W subjected to substrate processing in the supercritical drying unit 17 is carried out from the supercritical drying unit 17 by the substrate transfer device 18, and placed on the delivery section 14. Then, the processed wafer W placed on the delivery section 14 is returned to the carrier C of the carrier placement section 11 by the substrate transfer device 13.

[0024] <Configuration of liquid processing unit> Next, the configuration of liquid processing unit 16 will be described with reference to Fig. 2. Liquid processing unit 16 is configured as a single-wafer type liquid processing unit. Liquid processing unit 16 itself can have a known configuration, and an example will be briefly described below.

[0025] 2, liquid processing unit 16 has a wafer holding mechanism 24 disposed in an outer chamber 23 that forms a processing space. Wafer holding mechanism 24 is configured to hold wafer W in a horizontal position and rotate it around a vertical axis.

[0026] In liquid processing unit 16, processing liquids (chemical liquid, rinse liquid, IPA, etc.) required for liquid processing are sequentially supplied from nozzle 26a positioned above wafer W which is supported and rotated by nozzle arm 26, thereby performing liquid processing on the surface (device formation surface) of wafer W. Although only one nozzle arm 26 and one nozzle 26a are shown in Fig. 2, any number of these may be provided.

[0027] In the final step of the liquid processing, IPA is supplied from a nozzle (26a) for supplying IPA (protective liquid) onto the surface of the wafer W, and the liquid (usually DIW as a rinsing liquid) that had been covering the surface of the wafer W until then is replaced with IPA. Thereafter, the flow rate of IPA supplied from the nozzle and the rotation speed of the wafer W are adjusted to adjust the thickness of the IPA liquid film covering the surface of the wafer W, and then the discharge of IPA from the nozzle and the rotation of the wafer W are stopped. As a result, the surface of the wafer W is covered with a protective liquid film of the desired thickness.

[0028] Currently, IPA (isopropyl alcohol) is often used as the processing liquid (protective liquid) for forming the protective liquid film. As the protective liquid, a mixture of a low-hydric alcohol other than IPA (e.g., ethanol, methanol, etc.) and a liquid with a different polarity from the low-hydric alcohol can also be used. The protective liquid is a liquid that has a high affinity with CO2 (carbon dioxide), which is used as a processing fluid in the supercritical drying process.

[0029] <Configuration of supercritical drying unit>

[0030] Next, the configuration of the supercritical drying unit 17 will be described with reference to Figures 3 to 5. This supercritical drying unit 17 is used for performing a supercritical drying process in which a substrate having a protective liquid film (here, IPA) formed on its surface is dried by using a processing fluid in a supercritical state.

[0031] As shown in FIGS. 3 and 4, the supercritical drying unit 17 includes a processing vessel 311 and a substrate holding tray 312 (hereinafter simply referred to as “tray 312”) that holds a wafer W in the processing vessel 311.

[0032] The tray 312 has a lid 313 that closes an opening 311C provided in a sidewall of the processing vessel 311, and a substrate holder 314 that extends in the horizontal direction and is integrally connected to the lid 313. The substrate holder 314 has a plate 315 and a plurality of support pins 316 provided on an upper surface of the plate 315. The wafer W is placed in a horizontal position on the support pins 316 with its front surface (the surface on which a device or a pattern is formed) facing upward. When the wafer W is placed on the support pins 116, a gap 17 is formed between the upper surface of the plate 15 and the lower surface (rear surface) of the wafer W.

[0033] The plate 315 is formed with a plurality of through holes 318 that vertically penetrate the plate 315. The plurality of through holes 318 serve to provide fluid communication between the upper and lower spaces of the plate 315, and also serve to allow lift pins (not shown) that mediate the transfer of the wafer W between the substrate transfer device 18 (see FIG. 1) and the plate 315 to pass through.

[0034] The tray 312 can be moved in the horizontal direction (Y direction) between a closed position and an open position by a tray moving mechanism 312M, which is shown diagrammatically in Fig. 3. In the closed position of the tray 312, the substrate holding part 314 is located within the internal space of the processing vessel 311, and the lid part 313 closes the opening in the side wall of the processing vessel 311. In the open position of the tray 312, the substrate holding part 314 is located outside the processing vessel 311 (see Fig. 1), and the wafer W can be transferred between the substrate holding part 314 and a substrate transfer arm (not shown) via a lift pin (not shown).

[0035] When the tray 312 is in the closed position (see FIGS. 3 and 4), the internal space of the processing vessel 311 is divided by the plate 315 into an upper space 311A ​​(in which the wafer W is placed) above the plate 315 and a lower space 311B below the plate 315. However, the upper space 311A ​​and the lower space 311B are not completely separated. The upper space 311A ​​and the lower space 311B are in fluid communication with each other via the through-holes 318 described above and via a gap between the periphery of the plate 315 and the inner wall surface of the processing vessel 111.

[0036] The processing vessel 311 is provided with a first fluid discharge part 321 and a second fluid discharge part 322. The first fluid discharge part 321 and the second fluid discharge part 322 discharge the processing fluid (carbon dioxide (hereinafter, for convenience, also referred to as "CO2") in this example) supplied from a supply source 230 of a supercritical fluid (processing fluid in a supercritical state) into the internal space of the processing vessel 311.

[0037] The first fluid discharge part 321 is provided below the plate 315 of the tray 312 in the closed position. The first fluid discharge part 321 discharges CO2 (processing fluid) into the lower space 311B toward the lower surface of the plate 315 (upward). The first fluid discharge part 321 can be configured by a through hole formed in the bottom wall of the processing vessel 311. The first fluid discharge part 321 may be a nozzle body attached to the bottom wall of the processing vessel 311.

[0038] The second fluid discharge part 322 is provided to be located to the side (position advanced in the positive Y direction) of the wafer W placed on the substrate holding part 314 of the tray 312 in the closed position. The second fluid discharge part 322 supplies CO2 into the upper space 311A. In the illustrated embodiment, the second fluid discharge part 322 is provided on the side wall of the processing vessel 311 opposite to the lid part 313.

[0039] In the illustrated embodiment, the second fluid discharge portion 322 is formed as a so-called "bar nozzle." In detail, the second fluid discharge portion 322 is formed by drilling a plurality of discharge ports 322b in a pipe 322a extending in the width direction (X direction) of the wafer W. The plurality of discharge ports 322b are arranged, for example, at equal intervals in the X direction. Each discharge port 322b discharges CO2 into the upper space 311A ​​horizontally or slightly diagonally downward toward the opening 313.

[0040] The configuration of the second fluid discharge part 322 is not limited to the above. The second fluid discharge part 322 may have any configuration as long as it can discharge supercritical CO2 so that a laminar flow of supercritical CO2 flowing in one direction (Y direction in FIG. 4) from one side of the wafer W to the other side of the wafer is formed near the surface of the wafer W, and the flow rate of supercritical CO2 is approximately uniform over the entire area of ​​the wafer. For this reason, the second fluid discharge part 322 is often configured similarly to the one shown in the figure. The second fluid discharge part 322 may be formed by drilling holes extending in the X direction inside an elongated block body extending in the X direction, and drilling a plurality of discharge ports extending in the Y direction in communication with the holes in the block body. Whatever the configuration, some space (the internal space of the pipe 322a in the illustrated example) exists immediately upstream of the discharge port of the second fluid discharge part 322. This disclosure will discuss in detail later on techniques for suppressing particles resulting from contaminants that have entered or accumulated in this (internal) space.

[0041] The processing vessel 311 is further provided with a fluid discharge part 324 that discharges the processing fluid from the internal space of the processing vessel 311. The fluid discharge part 324 may have substantially the same configuration as the second fluid discharge part 322. Like the second fluid discharge part 322, the fluid discharge part 324 can be formed by drilling a plurality of discharge ports 324b in a pipe 324a extending in the horizontal direction. The plurality of discharge ports 324b are arranged at equal intervals in the X direction, for example. Each discharge port 324b faces upward and toward the elongated hole 319 of the plate 315.

[0042] In the illustrated embodiment, the fluid discharge portion 324 is provided in a recess formed in the bottom wall of the processing vessel 311 near the opening 311C. As shown by arrow F in FIG. 3, CO2 flows through a region above the wafer W in the upper space 311A, then flows into the lower space 311B through a communication passage provided in the peripheral portion of the plate 315 (or through hole 319 formed in the plate 315), and is then discharged from the fluid discharge portion 324.

[0043] The arrangement of the second fluid discharge part 322 and the fluid discharge part 324 is not limited to that shown in the figure, and they can be arranged at any position as long as the CO2 supplied from the second fluid discharge part 322 into the processing vessel 311 passes through an area above substantially the entire surface of the wafer W in a substantially horizontal direction and then is discharged from the fluid discharge part 324.

[0044] The supercritical processing unit 17 is provided with a locking mechanism 325 for maintaining the tray 312 in a closed position even when the inside of the processing vessel 311 becomes highly pressurized. The locking mechanism 325 has a bar-shaped locking member 325C that is raised and lowered by a lifting mechanism 325B within a guide hole 325A formed in the processing vessel 311.

[0045] Next, a supply / discharge system for supplying and discharging carbon dioxide (hereinafter, also referred to as "CO2" for the sake of simplicity) to and from the treatment vessel 311 of the supercritical drying unit 17 will be described with reference to FIG.

[0046] In the piping diagram shown in Figure 5, the component indicated by a T in a square is a temperature sensor. The temperature sensors are given a reference code in the format of "T + 3 digits" to distinguish them from each other. The component indicated by a P in a circle is a pressure sensor. Each pressure sensor is given a reference code in the format of "P + 3 digits" to distinguish them from each other. The component indicated by the code OLF is an orifice (fixed throttle) that reduces the pressure of the CO2 that flows through it. The component indicated by the code F is a filter that removes contaminants such as particles contained in the CO2. The component indicated by the code CV is a check valve. The component indicated by the code FM is a flow meter. The component indicated by the code H in a square is a heater for adjusting the temperature of the CO2. The component indicated by the code AV + 3 digits is an opening and closing valve.

[0047] The supercritical processing apparatus includes a supercritical fluid supplying apparatus 230. In this embodiment, the supercritical fluid is CO2 in a supercritical state (hereinafter, also referred to as "supercritical CO2"). The supercritical fluid supplying apparatus 230 has a well-known configuration including, for example, a carbon dioxide gas cylinder, a pressure pump, a heater, and the like. The supercritical fluid supplying apparatus 230 has a capability of delivering supercritical CO2 at a pressure, for example, about 20 MPa, that can reliably increase the pressure inside the processing vessel 311 to a supercritical state guarantee pressure (specifically, for example, about 16 MPa) described below.

[0048] A main supply line 232 is connected to the supercritical fluid supply device 230. CO2 flows out of the supercritical fluid supply device 230 in a supercritical state into the main supply line 232, but may become gaseous due to subsequent expansion (pressure drop) or temperature change. In this specification, a member called a "line" may be composed of a pipe (piping member).

[0049] The main supply line 232 branches into a first supply line 234 and a second supply line 236 at a branch point 233. The first supply line 234 is connected to a first fluid discharge part 321 of the processing vessel 311.

[0050] The second supply line 236 is connected to the second fluid discharge part 322 of the processing vessel 311. When the second fluid discharge part 322 is formed of a horizontally extending pipe 322a having a plurality of holes 322b as shown in Figures 3 and 4, the second supply line 236 branches downstream of the branch point 233 into two second branch supply lines 236A and 236B. The downstream ends of the second branch supply lines 236A and 236B are connected to both ends of the pipe 322a (indicated by reference numerals 323A and 323B in Figure 4).

[0051] A discharge line 238 is connected to the fluid discharge part 324 of the processing vessel 311. When the fluid discharge part 324 is formed of a horizontally extending tube with a plurality of holes drilled therein, similar to the second fluid discharge part 322, the second fluid discharge part 322 is composed of branch discharge lines 238A, 238B connected to both ends of this tube. These branch discharge lines 238A, 238B join together to form a single discharge line 238.

[0052] The exhaust line 238 is provided with a pressure regulating valve 240. By adjusting the opening degree of the pressure regulating valve 240, the primary pressure of the pressure regulating valve 240 can be adjusted, and therefore the pressure inside the processing vessel 311 can be adjusted. A valve designed as a back pressure valve (BPV) can be used as the pressure regulating valve 240.

[0053] 1 feedback-controls the opening degree of the pressure regulating valve 240 based on the deviation between the measured value (PV) and the set value (SV) of the pressure in the processing vessel 311 so that the pressure in the processing vessel 311 is maintained at the set value. A pressure sensor PS203 provided between the processing vessel 311 and the on-off valve AV207 provided in the exhaust line 238 (branch exhaust line 238A) can detect a pressure substantially equal to the pressure in the processing vessel 311. Therefore, in the feedback control, the detection value of the pressure sensor PS203 may be used as the measured value (PV). The pressure in the processing vessel 311 may be directly measured by a pressure sensor provided in the processing vessel 311.

[0054] A bypass line 244 branches off from the first supply line 234 at a branch point 242 provided on the first supply line 234. The bypass line 244 is connected to the discharge line 238 at a junction point 246 provided on the discharge line 238. The junction point 246 is located upstream of the pressure regulating valve 240.

[0055] A branch exhaust line 250 branches off from exhaust line 238 at a branch point 248 set in exhaust line 238 upstream of pressure regulating valve 240. The downstream end of branch exhaust line 250 is, for example, open to the atmospheric space outside the supercritical processing apparatus or connected to a factory exhaust duct.

[0056] At a branch point 252 set in the discharge line 238, two branch discharge lines 254, 256 branch off from the discharge line 238. The downstream ends of the branch discharge lines 254, 256 merge with the discharge line 238 again. The downstream end of the discharge line 238 is connected to, for example, a fluid recovery device (not shown). Useful components (for example, IPA (isopropyl alcohol)) contained in the CO2 recovered by the fluid recovery device are appropriately separated and reused.

[0057] A purge gas supply line 262 is connected to a junction 260 set in the first supply line 234 between the branch point 242 and the processing vessel 311. A purge gas (e.g., nitrogen gas) can be supplied to the processing vessel 311 through the purge gas supply line 262.

[0058] An exhaust line 266 branches off from a branch point 264 located on the main supply line 232 immediately upstream of the branch point 233 .

[0059] Next, one embodiment of a drying method (substrate processing method) performed using the above-mentioned supercritical processing apparatus will be described with reference to Figures 6A to 6E. The drying method described below is automatically performed under the control of the controller 4 based on a processing recipe and a control program stored in the storage unit 19 of the controller 4.

[0060] In Figs. 6A to 6E, the on-off valves filled in black are in a closed state, and the on-off valves not filled in are in an open state, and the lines through which high-pressure CO2 exists are indicated by thick solid lines.

[0061] [Delivery process] The wafer W, which has been subjected to liquid processing by liquid processing unit 16 and on whose surface a protective liquid film of IPA has been formed, is placed on plate 315 of tray 314 waiting at the substrate transfer position by substrate transfer device 18 shown in Fig. 1. When tray 314 on which wafer W is placed moves to the processing position, a sealed processing space is formed in processing vessel 311, and wafer W is positioned within the processing space.

[0062] [Pressure increase process (first process)] Next, a boosting process is performed, which includes an initial deceleration boosting stage and a normal boosting stage following the deceleration boosting stage.

[0063] The on-off valve AV213 may be normally closed during the pressurization and circulation process and may be open during the depressurization process. The on-off valve AV213 may be normally closed from the start of the pressurization process to the end of the depressurization process, or may be open at an appropriate timing as necessary. When the on-off valve AV213 is open, exhaust can be performed without passing through the pressure adjustment valve 240, so that the exhaust or depressurization time can be shortened. The on-off valve AV206 is also opened only when purging the inside of the processing vessel 311. In the following description, it is assumed that the on-off valve AV206 and the on-off valve V213 are normally closed during processing of the wafer W.

[0064] <Deceleration boost stage> First, as shown in FIG. 2A, the on-off valves AV204, AV205, AV211, and AV212 are closed, and the on-off valves AV201, AV202, AV203, AV209, and AV210 are opened. In this deceleration pressure increase stage, the pressure regulating valve 240 may be fixed to an appropriate opening, for example, the same opening as the initial opening in the circulation process described later. A part of the CO2 sent in a supercritical state from the supercritical fluid supply device 230 to the main supply line 232 is discharged from the exhaust line 266, and the remaining part of the CO2 flows into the first supply line 234, and a part of it flows into the processing vessel 311 through the first fluid discharge part 321. In addition, a part of the CO2 flowing through the first supply line 234 does not go to the processing vessel 311, but flows into the exhaust line 238 through the bypass line 244, and after flowing through the exhaust line 238, it is discarded in the factory exhaust duct or recovered for reuse.

[0065] Immediately after the start of the deceleration pressure increase stage, the pressure of CO2 delivered in a supercritical state from the supercritical fluid supply device 230 drops significantly when it flows into the processing vessel 311, which has a relatively large volume and is in a normal pressure state. That is, at the beginning of the introduction of CO2 into the processing vessel 311, the pressure of CO2 in the processing vessel 311 is lower than the critical pressure (about 8 MPa), so that CO2 is in a gaseous state. Since the difference between the pressure in the first supply line 234 and the pressure in the processing vessel 311, which is in a normal pressure state, is very large, CO2 flows into the processing vessel 311 at a high flow rate immediately after the start of the deceleration pressure increase stage. If CO2 (especially CO2 in a gaseous state at a high speed) collides with the wafer W or flows near the wafer W, the puddle of IPA on the peripheral portion of the wafer W may collapse (local evaporation or fluctuation), which may cause the pattern to collapse.

[0066] In this embodiment, in the deceleration pressure increase stage, i.e., in the early stage of introduction of CO2 into the processing vessel 311, a part of CO2 flowing through the main supply line 232 is released to the exhaust line 266 (release operation A), and a part of CO2 flowing through the first supply line 234 is released to the bypass line 244 (release operation B). This prevents CO2 from flowing into the processing vessel 311 at a high flow rate.

[0067] Furthermore, in this embodiment, since the orifice (OLF) is provided in the first supply line 234, the flow rate of CO2 flowing from the first fluid discharge part 321 into the processing vessel 311 is lower than that in the case where there is no orifice, so that the pattern collapse due to the above mechanism can be suppressed.

[0068] The pattern collapse due to the above mechanism can occur only in the initial stage of introduction of CO2 into the processing vessel 112. This is because the flow rate of CO2 flowing into the processing vessel 112 via the first fluid discharge part 121 decreases as the internal pressure of the processing vessel 112 increases. Therefore, it is sufficient to perform the deceleration pressure increase stage for a relatively short period of time, for example, about 10 to 20 seconds. Also, it is not necessary to perform the relief operations A and B throughout the entire period of the deceleration pressure increase stage, and relief operation A may be stopped first. Also, the opening / closing valve AV210 of the exhaust line 238 may be closed during the deceleration pressure increase stage.

[0069] <Normal boost stage> Next, as shown in Fig. 6B, the on-off valves AV202 and AV210 are also closed. This switching can be performed, for example, when the pressure inside the processing vessel 311 (e.g., the detection value of the pressure sensor PS203) exceeds a predetermined threshold. Alternatively, the switching can be performed when a predetermined time (e.g., about 10 seconds as described above) has elapsed since the start of the deceleration pressure increase stage. In this normal pressure increase stage, it is preferable to fix the aperture of the pressure adjustment valve 240 to the initial aperture in the flow process described below in order to smoothly transition to the flow process described below.

[0070] With the switching of the on-off valves, the CO2 flowing from the bypass line 244 to the exhaust line 238 and being exhausted through the exhaust line 238 is blocked by the on-off valves AV210 to AV212. In addition, the line 250 is also closed by the on-off valve V213 in the closed state. Therefore, the lines 244, 238, 250, 254, and 256 are filled with CO2, and the pressure in the lines increases. Then, the flow rate of CO2 flowing from the first supply line 234 to the bypass line 244 also decreases, and the pressure in the processing vessel 112 increases at a higher pressure increase speed than in the deceleration pressure increase stage.

[0071] When the pressure inside the processing vessel 311 exceeds the critical pressure of CO2 (approximately 8 MPa), the CO2 (CO2 not mixed with IPA) present inside the processing vessel 311 becomes supercritical. When the CO2 inside the processing vessel 312 becomes supercritical, the IPA on the wafer W starts to dissolve into the CO2 in the supercritical state.

[0072] After the pressure in the process vessel 112 exceeds the critical pressure of CO2, the normal pressure increase stage is continued until the pressure reaches a predetermined target pressure. In this embodiment, the target pressure is set to 16 MPa, which is a pressure that ensures that CO2 in the process vessel 112 is maintained in a supercritical state (hereinafter, for convenience, also referred to as a "supercritical state guarantee pressure") regardless of the IPA concentration and temperature in the mixed fluid (CO2+IPA) on the wafer W.

[0073] [Depressurization process (density adjustment process)] When it is confirmed by a pressure sensor (e.g., pressure sensor PS203 in FIG. 5) that the pressure inside the processing vessel 12 has reached the supercritical state guaranteed pressure, as shown in FIG. 6C, all other on-off valves are closed, and the on-off valve AV202 is opened for a short time (e.g., about one second) to temporarily reduce the pressure in the area upstream of the on-off valves AV204, AV205 of the second branch supply lines 136A, 136B and the area communicating therewith (areas indicated by thick dashed lines). The technical significance of this depressurization process will be described in detail later.

[0074] [Distribution process (2nd process)] Next, as shown in FIG. 6D, the on-off valve AV202 is closed, the on-off valves AV201, AV204, AV205, AV207, AV208, and AV210 are opened, and an appropriate initial opening command signal is given to the pressure regulating valve 240, and the opening control of the pressure regulating valve 240 is switched to feedback control, and the flow process is started. The above-mentioned "initial opening" may be, for example, the same opening as the opening when the pressure in the processing vessel 311 is stable at the above-mentioned supercritical state guarantee pressure during the flow process. It is preferable to open the on-off valve AV210 simultaneously with the opening of the on-off valves AV207 and AV208, or slightly after the opening of the on-off valves AV207 and AV208. With the above-mentioned switching, CO2 is supplied into the processing vessel 311 through the second supply line 236, the second branch supply lines 236A and 236B, and the second fluid discharge part 322.

[0075] In the circulation process, while the pressure inside the processing vessel 311 is maintained at the above-mentioned supercritical state guarantee pressure (16 MPa) by feedback control of the pressure regulating valve 240, the supercritical CO2 supplied from the second fluid discharge part 322 into the processing vessel 311 flows in the region above the substrate, and is then discharged from the fluid discharge part 324. At this time, a laminar flow of supercritical CO2 flowing approximately parallel to the surface of the wafer W is formed inside the processing vessel 311. The IPA in the mixed fluid (IPA+CO2) on the surface of the wafer W exposed to the laminar flow of supercritical CO2 is replaced with supercritical CO2. Eventually, almost all of the IPA on the surface of the wafer W is replaced with supercritical CO2.

[0076] The mixed fluid consisting of IPA and supercritical CO2 discharged from the fluid discharge part 324 is collected after flowing through the discharge line 238. The IPA contained in the mixed fluid can be separated and reused. In the circulation process, the on-off valves AV211 and AV212 may be opened or closed depending on the desired flow rate, etc.

[0077] [Discharge process] When the replacement of IPA with supercritical CO2 is completed, as shown in FIG. 6E, the on-off valves AV204 and AV205 are closed to stop the supply of supercritical CO2 to the processing vessel 311, and the set pressure of the processing vessel 311 is lowered to normal pressure. At this time, the on-off valve AV209 of the bypass line 244 may be opened. As a result, the opening degree of the pressure adjustment valve 240 is significantly increased (for example, fully opened), and the pressure in the processing vessel 311 is lowered to normal pressure. As a result, the supercritical CO2 in the pattern of the wafer W becomes gas and is released from the pattern, and the gaseous CO2 is discharged from the processing vessel 311 (see the thick dashed line). Instead of lowering the set pressure of the processing vessel 311 to normal pressure, the control unit 4 may give a command signal to the pressure adjustment valve 240 to increase the opening degree of the pressure adjustment valve 240. In the discharge process, the set pressure of the processing vessel 311 may be lowered to normal pressure in stages. The drying of the wafer W is completed as described above.

[0078] [Export process] Plate 315 of tray 314 on which dried wafer W is placed moves out of processing vessel 311 to the substrate transfer position. Wafer W is taken out of plate 315 by substrate transfer device 18 (FIG. 1) and carried out from supercritical drying unit 17. This completes the supercritical drying process for one wafer.

[0079] [Detailed explanation of the depressurization process] Next, the depressurization process (see FIG. 6C) performed between the pressurization process and the circulation process will be described in detail. As shown in FIG. 6B, immediately before the end of the pressurization process (normal pressurization stage), CO2 flows from the main supply line 232 through the first supply line 234 to the processing vessel 311, and since the first supply line 234 is provided with an orifice OLF (for convenience of explanation, this orifice is also called "orifice OLF1"), a pressure drop occurs at the orifice OLF1. That is, the pressure in the region upstream of the orifice OLF1 (pressure in the line) is higher than the pressure in the processing vessel 311 (pressure in the vessel). When the flow of CO2 through the orifice OLF1 stops, the pressure difference between the upstream region and the downstream region of the orifice OLF1 gradually decreases, but does not immediately become zero. The pressure in the region upstream of the orifice OLF1 is slightly lower than, for example, 20 MPa, which is the CO2 delivery pressure of the supercritical fluid supply device 230. At this time, the pressure detected by the pressure sensor PS201 is about 19 MPa (see also the graph in FIG. 7). On the other hand, the pressure in the downstream region of the orifice OLF1 is almost equal to the target pressure (16 MPa) of the processing vessel.

[0080] The IPA liquid film on the wafer W may contain (or dissolve) contaminants. The contaminants may be those that have been attached to the wafer W before processing in the liquid processing unit 16, those that have been attached in the liquid processing unit 16, those that have been attached during transportation, and the like. During the pressure increase process, the IPA containing or dissolving contaminants is detached from the IPA liquid film on the wafer W, floats in the processing vessel 311, and enters the inner space of the pipe 322a of the second fluid discharge part 322 (the pressure in this space is approximately normal pressure at the start of the pressure increase process). Furthermore, by repeatedly processing the wafer W in the processing vessel 311, the contaminants adhere to and accumulate on the inner wall of the pipe 322a. The accumulation of contaminants on the inner wall of the pipe 322a is unavoidable. During the pressure increase process, CO2 supplied to the processing vessel 311 also enters the inside of the pipe 322a. When the internal pressure of the tube 322a increases in the later stage of the pressure increase step and CO2 reaches a critical state inside the tube 322a, at least a portion of the contaminants present inside the tube 322a dissolves in the CO2.

[0081] The amount of contaminants that dissolve in supercritical CO2 increases as the density of supercritical CO2 increases (i.e., as the pressure of supercritical CO2 increases). Therefore, the solubility of the contaminants present inside the tube 322a in supercritical CO2 reaches a maximum in the final stage of the pressure increase process.

[0082] Here, assume that the pressure increase process is shifted to the circulation process without performing the depressurization process. In this case, when the on-off valves AV204 and AV205 are opened, the supercritical CO2 at high pressure (for example, about 18 to 19 MPa) on the upstream side flows into the pipe 322a at a pressure almost the same as the pressure in the treatment vessel 311 (for example, about 16 MPa). This causes the CO2 pressure (i.e., CO2 density) in the pipe 322a to rise suddenly, and some of the contaminants in the pipe 322a that were not dissolved in the supercritical CO2 until then dissolve ("additional dissolution") and are discharged into the treatment vessel 311. Furthermore, due to the large pressure difference (about 2 to 3 MPa) between the pipe 322a and the treatment vessel 311, CO2 is vigorously sprayed from the discharge port 322b of the pipe 322a. At this time, the contaminants in the pipe 322a are easily discharged into the pipe 322a together with CO2.

[0083] In the period immediately after the start of discharge from the pipe 322a, the high-pressure CO2 in the pipe 322a is discharged into the low-pressure processing vessel 311, so that the pressure of CO2 drops suddenly, and the solubility of the contaminants in CO2 decreases accordingly, and the contaminants dissolved in CO2 precipitate. The precipitated contaminants may adhere to the wafer W and contaminate the wafer W. Incidentally, after the start of the circulation process, when CO2 passes through the processing vessel 311 and flows stably at a relatively large flow rate, the pressure in the main supply line 232 decreases (see lines PS201-1 and PS201-2 in FIG. 7), and the large pressure difference between the internal space of the processing vessel 311 and the internal space of the pipe 322a is eliminated. In other words, the above problem can occur only in the early stage of the circulation process.

[0084] The above problem can be solved by carrying out the above-mentioned depressurization process. First, by carrying out the depressurization process, the above-mentioned "additional dissolution" is less likely to occur. Since the difference between the pressure in the processing vessel 311 and the pressure in the pipe 322a becomes small near the start of CO2 discharge, CO2 is prevented from being sprayed vigorously from the discharge port 322b, and also, precipitation of contaminants from the CO2 discharged from the pipe 322a into the processing vessel 311 is less likely to occur. Therefore, the possibility of the wafer W being contaminated is reduced.

[0085] The depressurization process is performed so that the pressure in the upstream region immediately adjacent to the on-off valves AV204 and AV205 is 2 MPa or less, preferably 1 MPa or less, higher than the pressure in the processing vessel 311 as a result of the depressurization process. As described above, when the boost target pressure is set to 16 MPa, the depressurization process can be performed so that the pressure in the upstream region immediately adjacent to the on-off valves AV204 and AV205 is, for example, about 17 MPa to 18 MPa. Note that, since a backflow of CO2 occurs, the pressure in the upstream region immediately adjacent to the on-off valves AV204 and AV205 cannot be made lower than the pressure in the processing vessel 311.

[0086] The depressurization process may be terminated when the detection value of a pressure sensor (e.g., pressure sensor P201 (see FIG. 1)) in an area upstream of the on-off valves AV204, AV205 becomes lower than a predetermined value. Alternatively, a pressure sensor (e.g., pressure sensor P205 shown by a dashed line in FIG. 5) may be provided at a position closer to the on-off valves AV204, AV205 than the pressure sensor P201, and the depressurization process may be terminated when the detection value of the pressure sensor becomes lower than a predetermined value (e.g., 17 MPa).

[0087] The graph in FIG. 7 shows an example of the transition of the detection value of the pressure sensor PS201 (corresponding to the pressure upstream of the on-off valves AV204 and AV205) before and after the depressurization process, and the transition of the detection value of the pressure sensor PS203 (corresponding to the pressure inside the processing vessel 311). The vertical axis of the graph is the detection pressure of the pressure sensor (unit: MPa), and the horizontal axis is time (5 seconds are shown in the graph). Lines PS201-1 and PS203-1 show the transition of the detection values ​​of the pressure sensors PS201 and PS203, respectively, when the depressurization process is not performed (comparative example). Lines PS201-2 and PS203-2 show the transition of the detection values ​​of the pressure sensors PS201 and PS203, respectively, when the depressurization process is performed (embodiment). In the graph, the period of about 1 second sandwiched between two vertical chain lines shows the period during which the depressurization process is performed (period during which the on-off valve AV202 is open). In addition, in Fig. 7, the period to the left of section PR corresponds to the end of the pressurization process (normal pressurization stage), and the period to the right of section PR corresponds to the beginning of the circulation process. From the graph in Fig. 7, it can be seen that by performing the depressurization process for about 1 second, the pressure on the upstream side of the on-off valves AV204 and AV205 decreases by about 2 MPa.

[0088] According to the above embodiment, by carrying out the depressurization process, the amount of particles present on the surface of the wafer W after the supercritical drying process can be significantly reduced. Experiments have confirmed that by carrying out the depressurization process, the amount of particles larger than 19 nm can be reduced by several hundreds (the number ratio can be reduced to about 1 / 3 to 1 / 4) compared to when the depressurization process is not carried out. Note that when CO2 is supplied using a bar nozzle in the flow process, particles are often generated in a concentrated manner on one side (left or right) of the wafer W, but it has been confirmed that such biased generation of particles does not occur.

[0089] [First modified embodiment of the depressurization process and the pressurization process] In the above embodiment, the pressure increasing step is continued until the pressure inside the processing vessel 311 reaches the supercritical state guarantee pressure (16 MPa), and then the flowing step is started, but the present invention is not limited to this.

[0090] That is, the normal pressure increase stage of the pressure increase process may be composed of a first normal pressure increase stage (first step) in which the pressure in the processing vessel 311 is increased to an appropriate pressure higher than the critical pressure (about 8 MPa) and lower than the supercritical state guarantee pressure (16 MPa) while supplying CO2 into the processing vessel 311 through the first supply line 234 and the first fluid discharge part 321, and then a second normal pressure increase stage (second step) in which the pressure in the processing vessel 311 is increased to the supercritical state guarantee pressure while supplying CO2 into the processing vessel 311 through the second supply line 236 and the second fluid discharge part 322. A depressurization process (density adjustment process) may be performed between the first normal pressure increase stage and the second normal pressure increase stage. The state of each opening and closing valve in the first normal pressure increase stage may be the same as that in the normal pressure increase stage in the above-mentioned embodiment. Moreover, the state of each on-off valve in the second normal pressurization stage may be the same as that in the normal pressurization stage in the above-mentioned embodiment, except that the on-off valve AV203 is closed and AV204 and AV205 are open. The depressurization step can be performed in the same procedure as the depressurization step in the above-mentioned embodiment (which is performed between the pressurization step and the circulation step). The depressurization step in this modified embodiment can also be performed so that the pressure in the area immediately upstream of the on-off valves AV204 and AV205 is higher than the pressure in the processing vessel 311 by 2 MPa or less, preferably 1 MPa or less.

[0091] As described above, when the normal pressurization stage of the pressurization process is divided into a first normal pressurization stage (first step) and a second normal pressurization stage (second step) and a depressurization process (density adjustment process) is performed between the first normal pressurization stage and the second normal pressurization stage, after the end of the second normal pressurization stage (after the supercritical state guaranteed pressure is reached), the discharge of CO2 from the treatment vessel 311 via the fluid discharge part 324 may be started, and the process may be shifted to the circulation process.

[0092] As described above, the particle reduction effect can be enhanced by switching the discharge part that discharges CO2 into the processing vessel 311 from the first fluid discharge part 321 to the second fluid discharge part 322 early and performing the depressurization process (density adjustment process) at the time of switching. That is, since the pressure in the processing vessel 311 is relatively low when the discharge from the second fluid discharge part 322 starts, the pressure in the second fluid discharge part 322 (bar nozzle) is also low. Therefore, dissolution of contaminants in the second fluid discharge part 322 is suppressed, so that the contaminants contained in the CO2 discharged from the second fluid discharge part 322 can be reduced. In addition, the pressure increase process can be performed in a short time by supplying CO2 into the processing vessel 311 from the second fluid discharge part 322 that can discharge CO2 at a relatively large flow rate after the pressure in the processing vessel 311 exceeds the critical pressure.

[0093] [Second modified embodiment of the depressurization process and the pressurization process] The density of supercritical CO2 also varies depending on temperature, and the higher the temperature, the lower the density of supercritical CO2. Therefore, instead of or in addition to the depressurization process, the supercritical CO2 present in the upstream region of the on-off valves AV204 and AV205 may be heated by a heater at the timing of performing the above-mentioned depressurization process. As a result, the temperature of the supercritical CO2 flowing into the pipe 322a immediately after the start of the pressure increase process becomes higher than the temperature of the supercritical CO2 present in the processing vessel 311. In other words, the density of the supercritical CO2 flowing into the pipe 322a immediately after the start of the pressure increase process becomes lower than the density of the supercritical CO2 present in the processing vessel 311. As described above, the solubility of the contaminant is positively correlated with the density of the solvent (supercritical CO2), so that the wafer contamination caused by the above mechanism can be suppressed. Since the density of supercritical CO2 is inversely proportional to absolute temperature, in the practical temperature range for supercritical drying (approximately 80 to 120°C), changing the pressure has a greater particle suppression effect. However, it is possible to obtain a particle suppression effect by adjusting the density only by adjusting the temperature of supercritical CO2. It is also possible to adjust the density by releasing the pressure in addition to adjusting the temperature of supercritical CO2, thereby enhancing the particle suppression effect.

[0094] In carrying out the second modified embodiment, it is preferable that the temperature of CO2 flowing into the processing vessel 311 through the first supply line 234 and the temperature of CO2 flowing into the processing vessel 311 through the second supply line 236 are independently adjustable. For this reason, instead of providing the heater H in the main supply line 232 as shown in FIG. 8, it is preferable to provide the heater H in each of the first supply line 234 and the second supply line 236 branched from the main supply line 232. Alternatively, as shown in FIG. 9, instead of branching the first supply line 234 and the second supply line 236 from the main supply line 232, the first supply line 234 and the second supply line 236 may be provided independently of each other, and the heater H may be provided in each of the first supply line 234 and the second supply line 236. In this case, the first supply line 234 and the second supply line 236 may be provided with a supercritical fluid supply device.

[0095] Since it is preferable to adjust the temperature of the CO2 present in a position close to the on-off valves AV204, AV205, a heater of the pipe-wrapped type such as a ribbon heater or a heater of the pipe-embedded type may be provided in the pipe immediately upstream of the on-off valves AV204, AV205. Also, a buffer tank equipped with a heater may be provided in the pipe immediately upstream of the on-off valves AV204, AV205, and CO2 heated in the buffer tank may be sent out immediately after the on-off valves AV204, AV205 are opened.

[0096] In the piping system diagrams according to the modified embodiment shown in FIGS. 8 and 9, when density adjustment is performed only by temperature adjustment, the exhaust line 233 and the on-off valve AV203 do not need to be provided.

[0097] When density adjustment is performed only by depressurization, the piping configurations shown in Figs. 8 and 9 can also be used.

[0098] The configuration of the processing vessel 311 is not limited to those shown in FIGS. 3 and 4, and may be, for example, the configuration shown in FIG. 10. In the modified embodiment of FIG. 10, the components having the same last three digits as those shown in FIGS. 3 and 4 have the same functions. The supply / discharge system connected to the processing vessel 1311 of FIG. 10 may be the one shown in FIGS. 5, 8, and 9. The modified embodiment shown in FIG. 10 operates as follows. That is, in the pressure increasing step, CO2 is supplied into the processing vessel 1311 through the first supply line 234 and the first fluid discharge part 1321. CO2 immediately after being discharged from the first fluid discharge part 1321 collides with the baffle plate 1340 and does not flow directly toward the wafer W. In the flowing step, CO2 is supplied into the processing vessel 1311 through the second supply line 234 and the second fluid discharge part 1322. The second fluid discharge part 1322 is provided above the wafer W held in a horizontal position by the wafer holder 1321, and discharges CO2 toward the surface of the wafer W. This CO2 is discharged from the processing vessel 1311 via the fluid discharge portion 1324.

[0099] In the modified embodiment shown in FIG. 10, by carrying out a depressurization process (density adjustment process) when switching from the pressurization process (or the first process) to the circulation process (or the second process), it is possible to reduce particles by the same mechanism as described above.

[0100] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0101] The disclosed embodiments should be considered to be illustrative and not restrictive in all respects. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0102] W substrate (wafer) 311 Processing vessel 4. Control Unit 321 First fluid discharge section 322 Second fluid discharge section 234 First Supply Line 236 Second Supply Line AV203 First opening and closing valve AV204, AV205 Second opening and closing valve 266 (exhaust line), AV202 (on-off valve), H (heater) Density adjustment mechanism

Claims

1. a processing vessel in which a substrate is processed using a processing fluid in a supercritical state; a processing fluid supply unit for supplying a processing fluid to the processing vessel; A control unit; Equipped with The processing fluid supply unit includes: a first fluid discharge unit configured to discharge the processing fluid into the processing vessel; a second fluid discharge unit that discharges the processing fluid into the processing vessel; a first supply line that supplies the processing fluid to the first fluid discharge portion; a first on-off valve provided in the first supply line; a second supply line that supplies the processing fluid to the second fluid discharge portion; a second on-off valve provided in the second supply line; a density adjusting mechanism that adjusts the density of the treatment fluid located upstream of the second on-off valve of the second supply line; It has The control unit controls the substrate processing apparatus. a first step of supplying the processing fluid to the first fluid discharge section through the first supply line with the first on-off valve in an open state and the second on-off valve in a closed state during at least a first period from when the supply of the processing fluid to the processing vessel is started until the pressure in the processing vessel increases and the processing fluid in the processing vessel reaches a supercritical state; a second step of supplying the processing fluid to the second fluid discharge portion through the second supply line at a flow rate greater than a flow rate of the processing fluid supplied from the first supply line to the first fluid discharge portion during at least a second period after the processing fluid in the processing vessel has reached a supercritical state by closing the first on-off valve and opening the second on-off valve; a density adjusting step of adjusting, by the density adjusting mechanism after the first step is completed and before the second step is started, a difference between an in-line density, defined as a density of the processing fluid present in a region upstream of the second on-off valve of the second supply line, and an in-vessel density, defined as a density of the processing fluid present in the processing vessel, to be smaller than a predetermined threshold value; The substrate processing apparatus is configured to perform the steps of:

2. the density adjustment mechanism includes a pressure adjustment mechanism, 2. The substrate processing apparatus of claim 1, wherein the control unit is configured, in the density adjustment process, to use the pressure adjustment mechanism to reduce a difference between an in-line pressure, defined as the pressure of the processing fluid present in a region upstream of the second on-off valve of the second supply line, and an in-container pressure, defined as the pressure of the processing fluid present in the processing container, to a predetermined threshold value, thereby reducing a difference between the in-line density and the in-container density to a predetermined threshold value.

3. 3. The substrate processing apparatus of claim 2, wherein the control unit is configured to open the second opening / closing valve and start the second process when, in the density adjustment process, the line pressure is greater than the container pressure and the difference between the line pressure and the container pressure is less than 2 MPa.

4. The pressure adjustment mechanism includes: a gas vent line connected to a region of the second supply line upstream of the second on-off valve; a gas venting on-off valve provided in the gas venting line; Including, 4. The substrate processing apparatus of claim 3, wherein the control unit is configured to, in the density adjustment process, close the first and second on-off valves and open the gas vent on-off valve to reduce the pressure in the line, thereby making the pressure in the line greater than the pressure in the container and making a difference between the pressure in the line and the pressure in the container less than 2 MPa.

5. a main supply line connected to a source of processing fluid in a supercritical state; Further equipped with the first supply line and the second supply line are lines branching off from the main supply line at a branch point set on the main supply line, 5. The substrate processing apparatus of claim 4, wherein the degassing line is connected to the main supply line at a position upstream of the branch point, or is connected to the second supply line between the branch point and the second on-off valve.

6. 5. The substrate processing apparatus of claim 4, wherein the first supply line and the second supply line are connected to a supply source of a processing fluid in a supercritical state, and the degassing line is connected to the second supply line at a position upstream of the second opening / closing valve.

7. the density adjustment mechanism includes a temperature adjustment mechanism, 2. The substrate processing apparatus of claim 1, wherein the control unit is configured, in the density adjustment process, to use the temperature adjustment mechanism to reduce a difference between an in-line temperature, defined as the temperature of the processing fluid present in a region upstream of the second on-off valve of the second supply line, and an in-container temperature, defined as the temperature of the processing fluid present in the processing container, to a predetermined threshold value, thereby reducing a difference between the in-line density and the in-container density to a predetermined threshold value.

8. The substrate processing apparatus according to claim 7 , wherein the temperature adjustment mechanism includes a heater provided in an area of ​​the second supply line upstream of the second on-off valve.

9. 2. The substrate processing apparatus of claim 1, wherein the control unit is configured to terminate the first process when the pressure in the processing vessel reaches a first pressure higher than a critical pressure of the processing fluid, then perform the density adjustment process, then perform the second process, and in the second process, increase the pressure in the processing vessel to a second pressure higher than the first pressure.

10. a substrate holder that holds the substrate having a liquid film formed on its surface horizontally in the processing vessel with the surface facing upward; the first fluid discharge unit is provided to discharge the processing fluid into the processing vessel from below the substrate held by the substrate holding unit, the second fluid discharge unit is configured to discharge the processing fluid into the processing vessel from a side of the substrate held by the substrate holding unit. The substrate processing apparatus according to claim 1 .

11. a processing vessel in which a substrate is processed using a processing fluid in a supercritical state; a processing fluid supply unit for supplying a processing fluid to the processing vessel; A control unit; Equipped with The processing fluid supply unit includes: a first fluid discharge unit configured to discharge the processing fluid into the processing vessel; a second fluid discharge unit that discharges the processing fluid into the processing vessel; a first supply line that supplies the processing fluid to the first fluid discharge portion; a first on-off valve provided in the first supply line; a second supply line that supplies the processing fluid to the second fluid discharge portion; a second on-off valve provided in the second supply line; a density adjusting mechanism that adjusts the density of the treatment fluid located upstream of the second on-off valve of the second supply line; A substrate processing method using a substrate processing apparatus, comprising: a first step of supplying the processing fluid to the first fluid discharge section through the first supply line with the first on-off valve in an open state and the second on-off valve in a closed state during at least a first period from when the supply of the processing fluid to the processing vessel is started until the pressure in the processing vessel increases and the processing fluid in the processing vessel reaches a supercritical state; a second step of supplying the processing fluid to the second fluid discharge portion through the second supply line at a flow rate greater than a flow rate of the processing fluid supplied from the first supply line to the first fluid discharge portion during at least a second period after the processing fluid in the processing vessel has reached a supercritical state by closing the first on-off valve and opening the second on-off valve; a density adjusting step of adjusting, by the density adjusting mechanism after the first step is completed and before the second step is started, a difference between an in-line density, defined as a density of the processing fluid present in a region upstream of the second on-off valve of the second supply line, and an in-vessel density, defined as a density of the processing fluid present in the processing vessel, to be smaller than a predetermined threshold value; A substrate processing method comprising:

12. the density adjustment mechanism includes a pressure adjustment mechanism, The substrate processing method of claim 11, wherein the density adjustment process reduces the difference between an in-line pressure, defined as the pressure of the processing fluid present in a region upstream of the second on-off valve of the second supply line, and an in-container pressure, defined as the pressure of the processing fluid present in the processing container, to a predetermined threshold value by the pressure adjustment mechanism, thereby reducing the difference between the in-line density and the in-container density to a predetermined threshold value.

13. 13. The substrate processing method according to claim 12, wherein the second step is started by opening the second on-off valve when the density adjustment step causes the line pressure to be greater than the container pressure and the difference between the line pressure and the container pressure to be less than 2 MPa.

14. The pressure adjustment mechanism includes: a gas vent line connected to a region of the second supply line upstream of the second on-off valve; a gas venting on-off valve provided in the gas venting line; Including, 14. The substrate processing apparatus of claim 13, wherein the density adjustment step comprises opening the gas vent valve to reduce the pressure in the line while keeping the first and second on-off valves closed, thereby making the pressure in the line greater than the pressure in the container and making a difference between the pressure in the line and the pressure in the container less than 2 MPa.

15. The substrate processing apparatus further comprises a main supply line connected to a source of processing fluid in a supercritical state; the first supply line and the second supply line are lines branching off from the main supply line at a branch point set on the main supply line, 15. The substrate processing method of claim 14, wherein the degassing line is connected to the main supply line at a position upstream of the branch point, or is connected to the second supply line between the branch point and the second on-off valve.

16. 15. The substrate processing method of claim 14, wherein the first supply line and the second supply line are connected to a supply source of a processing fluid in a supercritical state, and the degassing line is connected to the second supply line at a position upstream of the second opening / closing valve.

17. the density adjustment mechanism includes a temperature adjustment mechanism, 12. The substrate processing method of claim 11, wherein the density adjustment process reduces the difference between an in-line temperature, defined as the temperature of the processing fluid present in a region upstream of the second on-off valve of the second supply line, and an in-container temperature, defined as the temperature of the processing fluid present in the processing container, to a predetermined threshold value by the temperature adjustment mechanism, thereby reducing the difference between the in-line density and the in-container density to a predetermined threshold value.

18. 18. The substrate processing method according to claim 17, wherein the temperature adjustment mechanism includes a heater provided in an area of ​​the second supply line upstream of the second on-off valve.

19. 12. The substrate processing method according to claim 11, wherein the first step is terminated when the pressure in the processing vessel becomes a first pressure higher than a critical pressure of the processing fluid, the density adjustment step is then performed, and the second step is then performed, and in the second step, the pressure in the processing vessel is increased to a second pressure higher than the first pressure.

20. the substrate processing apparatus further includes a substrate holder configured to horizontally hold the substrate, the substrate having a liquid film formed on its surface, in the processing chamber with the surface facing upward; the first fluid discharge unit is provided to discharge the processing fluid into the processing vessel from below the substrate held by the substrate holding unit, the second fluid discharge unit is configured to discharge the processing fluid into the processing vessel from a side of the substrate held by the substrate holding unit. The method of claim 11.

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