Substrate processing apparatus and substrate processing method

Abstract

To surely suppress a destruction of a pattern formed on a surface of a substrate.SOLUTION: A substrate processing apparatus making a substrate onto which liquid is adhered onto a surface thereof dry by using treatment fluid in a supercritical state, comprises: a treatment container housing the substrate; a substrate holding part that horizontally holds the substrate by setting the surface to an upper direction in the treatment container; a first supply line that is connected to a first fluid supply part provided to the treatment container, and supplies the treatment fluid into the treatment container; an exhaust line that is connected to an exhaust part provided to the treatment container and exhausts the treatment fluid from the treatment container; a bypass line that is branched from the first supply line at a first branch point set to the first supply line, and is connected to the exhaust line at a connection point set to the exhaust line, and enable the exhaust of at least one part of the treatment fluid flowing in the first supply line to the exhaust line without passing through the treatment container; and a bypass switch valve that switches the bypass line.SELECTED DRAWING: Figure 1

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, which form a laminated structure of integrated circuits on the surface of a substrate such as a semiconductor wafer (hereinafter referred to as "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, drying methods using a processing fluid in a supercritical state have recently been used in the drying step, which is the final step of liquid processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-074103 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can more reliably prevent collapse of a pattern formed on the surface of a substrate. [Means for solving the problem]

[0005] One embodiment of a substrate processing apparatus is a substrate processing apparatus that dries a substrate having a liquid adhering to its surface using a processing fluid in a supercritical state, and includes: a processing vessel that accommodates the substrate; a substrate holder that holds the substrate horizontally in the processing vessel with the surface facing upward; a first supply line connected to a first fluid supply unit provided in the processing vessel and that supplies the processing fluid into the processing vessel; a discharge line connected to a discharge unit provided in the processing vessel and that discharges the processing fluid from the processing vessel; a bypass line that branches off from the first supply line at a first branch point set in the first supply line and is connected to the discharge line at a connection point set in the discharge line, allowing at least a portion of the processing fluid flowing through the first supply line to be discharged to the discharge line without passing through the processing vessel; and a bypass opening / closing valve that opens and closes the bypass line. [Effects of the Invention]

[0006] According to the above embodiment, it is possible to more reliably prevent the pattern formed on the surface of the substrate from collapsing. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a piping diagram showing a configuration of a supercritical processing apparatus as an embodiment of a substrate processing apparatus. [Figure 2A] FIG. 3 is a schematic diagram for explaining a deceleration pressure increase stage of the pressure increase step in the drying method according to the first embodiment. [Figure 2B] FIG. 3 is a schematic view for explaining a normal pressure increase stage in the pressure increase step in the drying method according to the first embodiment. [Figure 2C] FIG. 2 is a schematic diagram for explaining a circulation step in the drying method according to the first embodiment. [Figure 2D] FIG. 3 is a schematic view for explaining a discharging step in the drying method according to the first embodiment. [Figure 3] 10 is a graph showing an example of a change in pressure inside the processing container from a pressurization step to a discharge step. [Figure 4A]10 is a graph illustrating a pressure change in the processing container that may occur during a transition from a pressurization step to a circulation step. [Figure 4B] 10 is a graph illustrating a pressure change in the processing container that may occur during a transition from a pressurization step to a circulation step. [Figure 5] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of a pressure regulating valve. [Figure 6A] FIG. 10 is a schematic diagram illustrating a deceleration pressure increase stage in the pressure increase step in the drying method according to the second embodiment. [Figure 6B] FIG. 10 is a schematic diagram for explaining a normal pressure increase stage in the pressure increase step in the drying method according to the second embodiment. [Figure 7A] FIG. 11 is a schematic diagram for explaining a deceleration pressure increase stage of the pressure increase step in the drying method according to the third embodiment. [Figure 7B] FIG. 10 is a schematic view for explaining another aspect of the deceleration pressure increase stage in the pressure increase step in the drying method according to the third embodiment. [Figure 7C] FIG. 10 is a schematic view for explaining a normal pressure increase stage in the pressure increase step in the drying method according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A supercritical processing apparatus as an embodiment of a substrate processing apparatus will be described with reference to the accompanying drawings. This supercritical processing apparatus can be used to dry a substrate having a liquid (e.g., IPA) attached to its surface by using a processing fluid in a supercritical state to perform supercritical drying processing.

[0009] 1, the supercritical processing apparatus includes a processing unit 10 in which a supercritical drying process is performed. The processing unit 10 includes a processing vessel 12 and a substrate holding tray 14 (hereinafter simply referred to as "tray 14") that holds substrates within the processing vessel 10.

[0010] In one embodiment, the tray 14 has a lid 16 that covers an opening in the sidewall of the processing vessel 12, and a horizontally extending substrate support plate (substrate holder) 18 (hereinafter simply referred to as the "plate 18") connected to the lid 16. The substrate W is placed horizontally on the plate 18 with its front surface (device formation surface) facing upward. The plate 18 is, for example, rectangular or square. The area of ​​the plate 18 is larger than that of the substrate W, and when the substrate W is placed at a predetermined position on the plate 18 and viewed from directly below, the substrate W is completely covered by the plate 18.

[0011] The tray 14 can be moved horizontally between a processing position (closed position) and a substrate transfer position (open position) by a tray moving mechanism (not shown). At the processing position, the plate 18 is located within the interior space of the processing vessel 12, and the lid 16 closes the opening in the sidewall of the processing vessel 12 (the state shown in FIG. 1). At the substrate transfer position, the plate 18 is located outside the processing vessel 12, allowing the transfer of substrates W between the plate 18 and a substrate transport arm (not shown). The movement direction of the tray 14 is, for example, the left-right direction in FIG. 1. The movement direction of the tray 14 may also be perpendicular to the plane of FIG. 1, in which case the lid 16 can be provided on the rear or front side of the plate 18 in the figure.

[0012] When the tray 14 is in the processing position, the plate 18 divides the internal space of the processing vessel 12 into an upper space 12A above the plate 18, where the substrate W is present during processing, and a lower space 12B below the plate 18. However, the upper space 12A and the lower space 12B are not completely separated. A gap serving as a communication path connecting the upper space 12A and the lower space 12B is formed between the peripheral edge of the tray 14 in the processing position and the inner wall surface of the processing vessel 12. Furthermore, a through-hole may be provided in the plate 18 near the lid 16, connecting the upper space 12A and the lower space 12B.

[0013] As described above, if the internal space of processing vessel 12 is divided into upper space 12A and lower space 12B and a communication passage is provided to connect upper space 12A and lower space 12B, tray 14 (plate 18) may be configured as a substrate mounting table (substrate holder) that is immovably fixed inside processing vessel 12. In this case, with a lid (not shown) provided on processing vessel 12 open, a substrate transfer arm (not shown) enters the vessel body, and substrates are transferred between the substrate mounting table and the substrate transfer arm.

[0014] The processing vessel 12 has a first fluid supply part 21 and a second fluid supply part 22 for receiving a pressurized processing fluid into the internal space of the processing vessel 12, in this embodiment carbon dioxide in a supercritical state (hereinafter, for convenience, also referred to as "CO2").

[0015] The first fluid supply unit 21 is provided below the plate 18 of the tray 14 in the processing position. The first fluid supply unit 21 supplies CO2 into the lower space 12B toward the lower surface of the plate 18. The first fluid supply unit 21 may be configured as a through-hole formed in the bottom wall of the processing vessel 12. The first fluid supply unit 21 may also be a nozzle body attached to the bottom wall of the processing vessel 12.

[0016] The second fluid supply unit 22 is provided to be located to the side of the substrate W placed on the plate 18 of the tray 14 in the processing position. The second fluid supply unit 22 can be provided, for example, on or near one side wall (first side wall) of the processing vessel 12. The second fluid supply unit 22 supplies CO2 into the upper space 12A toward a region slightly above the substrate W.

[0017] The second fluid supply unit 22 can be configured with a plurality of outlets arranged in a horizontal direction (for example, a direction perpendicular to the plane of the paper in FIG. 1). More specifically, the second fluid supply unit 22 can be formed, for example, as a header made of a horizontally extending pipe-shaped member with a plurality of holes drilled therein. The second fluid supply unit 22 is preferably configured to be able to flow CO2 along the upper surface (front surface) of the substrate W, approximately evenly in the region above the substrate W over the entire diameter of the substrate W.

[0018] The processing vessel 12 further includes a fluid discharge unit 24 that discharges the processing fluid from the internal space of the processing vessel 12. The fluid discharge unit 24 can be formed as a header made of a horizontally extending pipe-shaped member having a plurality of holes, similar to the second fluid supply unit 22. The fluid discharge unit 24 can be provided, for example, on or near the side wall (second side wall) of the processing vessel 12 opposite to the first side wall on which the second fluid supply unit 22 is provided.

[0019] The fluid discharge unit 24 can be disposed at any position as long as the CO2 supplied from the second fluid supply unit 22 into the processing vessel 12 passes through the region above the substrate W on the plate 18 and is then discharged from the fluid discharge unit 24. That is, for example, the fluid discharge unit 24 may be provided at the bottom of the processing vessel 12 near the second side wall. In this case, the CO2 passes through the region above the substrate W in the upper space 12A, flows into the lower space 12B through a communication path provided at the periphery of the plate 18 (or a through-hole formed in the plate 18), and is then discharged from the fluid discharge unit 24.

[0020] Next, we will explain the supply / discharge system that supplies and discharges CO2 to and from the processing vessel 12 in the supercritical processing equipment. In the piping system diagram shown in Figure 1, the circled T indicates a temperature sensor, and the circled P indicates a pressure sensor. The OLF indicates an orifice (fixed throttle) that reduces the pressure of the CO2 flowing in the downstream piping to a desired value. The SV indicates a safety valve (relief valve) that prevents damage to the piping or the processing vessel 12 or other components of the supercritical processing equipment due to unexpected excessive pressure. The F indicates a filter that removes contaminants such as particles contained in the CO2. The CV indicates a check valve. The FV indicates a flow meter. The H indicates a heater that controls the temperature of the CO2. Members designated by reference symbol VN (N is a natural number) are on-off valves, and ten on-off valves V1 to V10 are depicted in FIG.

[0021] The supercritical processing apparatus includes a supercritical fluid supply device 30. In this embodiment, the supercritical fluid is carbon dioxide in a supercritical state (hereinafter also referred to as "supercritical CO2"). The supercritical fluid supply device 30 has a well-known configuration including, for example, a carbon dioxide gas cylinder, a pressure pump, a heater, etc. The supercritical fluid supply device 30 has the ability to deliver supercritical CO2 at a pressure equal to or higher than the supercritical state guarantee pressure (specifically, approximately 16 MPa) described below.

[0022] A main supply line 32 is connected to the supercritical fluid supply device 30. CO2 flows out of the supercritical fluid supply device 30 into the main supply line 32 in a supercritical state, but may become gaseous due to subsequent expansion or temperature changes. In this specification, a member referred to as a "line" may be constituted by a pipe (a piping member).

[0023] The main supply line 32 branches into a first supply line 34 and a second supply line 36 at a branch point 33. The first supply line 34 is connected to a first fluid supply unit 21 of the processing vessel 12. The second supply line 36 is connected to a second fluid supply unit 22 of the processing vessel 12.

[0024] An exhaust line 38 is connected to the fluid exhaust unit 24 of the processing vessel 12. A pressure regulating valve 40 is provided in the exhaust line 38. By adjusting the opening of the pressure regulating valve 40, the primary pressure of the pressure regulating valve 40 can be adjusted, and therefore the pressure inside the processing vessel 12 can be adjusted.

[0025] 1 feedback-controls the opening degree (specifically, the position of the valve element) of the pressure regulating valve 40 based on the deviation between the measured value (PV) and the set value (SV) of the pressure in the processing vessel 12 so that the pressure in the processing vessel 12 is maintained at the set value. As the measured value of the pressure in the processing vessel 12, for example, the value detected by a pressure sensor indicated by reference symbol PS provided between the on-off valve V3 of the exhaust line 38 and the processing vessel 12, as shown in FIG. 1, can be used. That is, the pressure in the processing vessel 12 may be measured directly by a pressure sensor provided in the processing vessel 12, or may be measured indirectly by a pressure sensor (PS) provided outside the processing vessel 12 (in the exhaust line 38).

[0026] The control unit 100 is, for example, a computer, and includes an arithmetic unit 101 and a storage unit 102. The storage unit 102 stores programs for controlling various processes executed in the supercritical processing apparatus (or a substrate processing system including the supercritical processing apparatus). The arithmetic unit 101 controls the operation of the supercritical processing apparatus by reading and executing the programs stored in the storage unit 102. The programs may be recorded on a computer-readable storage medium and installed from the storage medium into the storage unit 102 of the control unit 100. Examples of computer-readable storage media include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnetic optical disk (MO), and a memory card.

[0027] A bypass line 44 branches off from the first supply line 34 at a branch point 42 set on the first supply line 34. The bypass line 44 is connected to the discharge line 38 at a connection point 46 set on the discharge line 38. The connection point 46 is located upstream of the pressure regulating valve 40.

[0028] A branch discharge line 50 branches off from the discharge line 38 at a branch point 48 set in the discharge line 38 upstream of the pressure regulating valve 40. The downstream end of the branch discharge line 50 is, for example, open to the atmosphere outside the supercritical processing apparatus or connected to a factory exhaust duct.

[0029] Two branch discharge lines 54, 56 branch off from the discharge line 38 at a branch point 52 set in the discharge line 38. The downstream ends of the branch discharge lines 54, 56 merge back into the discharge line 38. The downstream end of the discharge line 38 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 separated as appropriate and reused.

[0030] A purge gas supply line 62 is connected to a junction 60 set in the first supply line 34 between the branch point 42 and the processing vessel 12. A purge gas can be supplied to the processing vessel 12 through the purge gas supply line 62.

[0031] An exhaust line 66 branches off from a branch point 64 set in the main supply line 32 immediately upstream of the branch point 33 .

[0032] First embodiment of drying method Next, a first embodiment of a drying method (substrate processing method) performed using the above-described supercritical processing apparatus will be described with reference to Figures 2A to 2D and also Figure 3. The drying method described below is automatically performed under the control of the control unit 100 based on a processing recipe and a control program stored in the storage unit 102.

[0033] 2A to 2D, the valves shaded in black are in the closed state, and the valves not shaded in are in the open state. In Figures 2A to 2D, the lines through which CO2 flows are shown by thick solid lines, and the lines through which CO2 remains under a certain pressure are shown by thick dashed lines.

[0034] The horizontal axis of the graph in Fig. 3 represents time, and the vertical axis represents the internal pressure of the treatment vessel 12. On the horizontal axis of the graph in Fig. 3, "2A" corresponds to the decelerated pressure increase stage of the pressure increase process, "2B" corresponds to the normal pressure increase stage of the pressure increase process, "2C" corresponds to the circulation process, and "2D" corresponds to the discharge process.

[0035] [Delivery process] A substrate W such as a semiconductor wafer, with the recesses of the pattern on its surface filled with IPA and with IPA puddles formed on its surface, is placed by a substrate transport arm (not shown) on the plate 18 of a tray 14 waiting at a substrate transfer position. Note that this substrate W has been sequentially subjected to, for example, (1) chemical processing such as wet etching or chemical cleaning, (2) a rinsing process in which the chemical solution is washed away with a rinsing solution, and (3) an IPA substitution process in which the rinsing solution is replaced with IPA to form IPA puddles, in a single-wafer cleaning apparatus (not shown). When the tray 14 with the substrate W placed thereon moves to the processing position, a sealed processing space is formed within the processing vessel 12, and the substrate W is positioned within the processing space.

[0036] [Pressure increase process] Next, a pressure-boosting process is performed, which includes an initial deceleration pressure-boosting stage and a normal pressure-boosting stage following the deceleration pressure-boosting stage.

[0037] Note that from the start of the pressurization step to the end of the depressurization step, on-off valve V9 is normally open, and on-off valves V10 and V11 are normally closed, and no reference will be made to these on-off valves V9 to V11. On-off valve V8 may be normally closed during the pressurization and circulation steps and open during the depressurization step. On-off valve V8 may be normally closed from the start of the pressurization step to the end of the depressurization step, or may be opened at an appropriate timing as needed. When on-off valve V8 is open, exhaust can be performed without passing through pressure regulating valve 40, thereby shortening the exhaust or depressurization time. Note that the following description will be given on the assumption that on-off valve V8 is normally closed.

[0038] <Deceleration boost stage> First, as shown in FIG. 2A, on-off valves V2 and V3 are closed, and on-off valves V1, V4 to V7 are opened (time t1 in FIG. 3). During this deceleration / pressure-boosting stage, the opening degree of pressure regulating valve 40 may be fixed, for example, to the initial opening degree in the circulation process described below. CO2 in a supercritical state sent from supercritical fluid supply device 30 to main supply line 32 flows into first supply line 34, and a portion of it (e.g., approximately 30 to 60%) flows into processing vessel 12 via first fluid supply unit 21. The remainder of the CO2 that has flowed through first supply line 34 does not flow into processing vessel 12 but flows through bypass line 44 into exhaust line 38. After flowing through exhaust line 38, it is either disposed of in a factory exhaust duct or recovered for reuse.

[0039] It is also possible to adjust the ratio of the flow rate of CO2 flowing into the treatment vessel 12 to the flow rate of CO2 flowing through the bypass line 44 by changing the aperture of the pressure regulating valve 40. Therefore, the aperture in the deceleration / pressurization stage may be different from the initial aperture in the circulation process described below.

[0040] Immediately after the start of the deceleration / pressure increase phase, the pressure of CO2 delivered in a supercritical state from the supercritical fluid supply device 30 drops significantly as it flows into the relatively large processing vessel 12, which is at atmospheric pressure. That is, at the beginning of the introduction of CO2 into the processing vessel 12, the pressure of CO2 in the processing vessel 12 is lower than the critical pressure (e.g., approximately 8 MPa), so the CO2 is in a gaseous state. Because the difference between the pressure in the first supply line 34 and the pressure in the processing vessel 12, which is at atmospheric pressure, is very large, CO2 flows into the processing vessel 12 at a high flow rate immediately after the start of the deceleration / pressure increase phase. If CO2 (especially CO2 in a gaseous state at a high rate) collides with the substrate W or flows near the substrate W, the IPA puddle at the peripheral edge of the substrate W may collapse (local evaporation or fluctuation), which may result in pattern collapse.

[0041] In this embodiment, since the orifice (OLF) is provided in the first supply line 34, the flow rate of CO2 when it flows from the first fluid supply unit 21 into the processing vessel 12 is lower than when there is no orifice, which makes it possible to suppress pattern collapse due to the above-mentioned mechanism.

[0042] In this embodiment, CO2 flowing from the first fluid supply unit 21 into the processing vessel 12 collides with the plate 18 of the tray 14, then bypasses the plate 18 and enters the upper space 12A where the substrate W is present (see the arrow in FIG. 2A). Therefore, when the gaseous CO2 reaches the vicinity of the substrate W, the flow rate of the CO2 is relatively low. This makes it possible to suppress pattern collapse due to the above-mentioned mechanism.

[0043] In addition to the above, in this embodiment, during the deceleration and pressure increase stage, i.e., the initial stage of CO introduction into the processing vessel 12, a portion of CO flowing through the first supply line 34 is vented to the bypass line 44, thereby further reducing the flow rate of CO flowing from the first fluid supply unit 21 into the processing vessel 12. This makes it possible to more reliably prevent pattern collapse due to the above mechanism.

[0044] 2A, when the flow rate of CO2 flowing from the first fluid supply unit 21 into the processing vessel 12 is high, the flow rate of CO2 may be high enough to cause pattern collapse due to the above-mentioned mechanism when the CO2 flows into the upper space 12A and reaches the vicinity of the peripheral edge of the substrate W. In this embodiment, to eliminate this possibility, a portion of the CO2 flowing through the first supply line 34 is diverted to the bypass line 44, thereby reducing the flow rate of CO2 flowing from the first fluid supply unit 21 into the processing vessel 12.

[0045] The pattern collapse due to the above mechanism can occur only in the initial stage of introducing CO2 into the processing vessel 12. This is because as the internal pressure of the processing vessel 12 increases, the flow rate of CO2 flowing into the processing vessel 12 via the first fluid supply unit 21 decreases. 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.

[0046] Another advantage of providing the deceleration pressure increase stage is that it is not necessary to extremely reduce the diameter of the orifice (OLF) of the first supply line 34. This makes it possible to shorten the pressure increase time when CO2 is supplied from the first supply line 34 to the processing vessel 12.

[0047] <Normal pressure boost stage> Next, as shown in FIG. 2B, the on-off valves V5 to V7 are closed (time t2 in FIG. 3). This switching can be performed, for example, when the detected pressure inside the processing vessel 12 exceeds a predetermined threshold. Alternatively, the switching can be performed when a predetermined time (e.g., the aforementioned approximately 10 seconds) has elapsed since the start of the deceleration pressure increase stage. During this normal pressure increase stage, it is preferable to fix the aperture of the pressure adjustment valve 40 to the initial aperture in the flow process, which will be described later, in order to smoothly transition to the flow process, which will be described later.

[0048] As the on-off valves are switched, the CO2 that had flowed from the bypass line 44 into the exhaust line 38 and through the exhaust line 38 and the branch exhaust lines 54 and 56 is blocked by the on-off valves V5 to V7. Furthermore, the line 50 is also closed by the on-off valve V8, which is in the closed state. Therefore, CO2 fills the lines 44, 38, 50, 54, and 56, and the pressure in those lines increases. Then, the flow rate of CO2 flowing from the first supply line 34 into the bypass line 44 also decreases, and the pressure in the processing vessel 12 increases at a higher rate than in the decelerated pressure increase stage.

[0049] When the pressure inside the processing vessel 12 exceeds the critical pressure of CO2 (approximately 8 MPa), the CO2 (CO2 not mixed with IPA) present inside the processing vessel 12 becomes supercritical. When the CO2 inside the processing vessel 12 becomes supercritical, the IPA on the substrate W begins to dissolve into the CO2 in the supercritical state.

[0050] After the pressure in the processing vessel 12 exceeds the critical pressure of CO2, the normal pressure increase step is continued until the pressure reaches a level that ensures that CO2 in the processing vessel 12 is maintained in a supercritical state (supercritical state guarantee pressure), regardless of the IPA concentration and temperature of the mixed fluid (CO2 + IPA) on the substrate W. The supercritical state guarantee pressure is approximately 16 MPa. Once the pressure in the processing vessel 12 reaches the supercritical state guarantee pressure, pattern collapse due to local phase changes (e.g., vaporization) of the mixed fluid within the surface of the substrate W no longer occurs. Note that such local phase changes occur due to non-uniform IPA concentration in the mixed fluid within the surface of the substrate W, and can occur particularly in areas exhibiting an IPA concentration that increases the critical temperature.

[0051] [Distribution process] When the pressure sensor confirms that the pressure inside the processing vessel 12 has reached the supercritical state guarantee pressure, as shown in Fig. 2C, the on-off valves V2, V3, V5 to V7 are opened, the on-off valves V1 and V4 are closed, the aperture control of the pressure adjustment valve 40 is switched to feedback control, and the flow process begins (time t3 in Fig. 3). It is preferable to open the on-off valves V5 to V7 simultaneously with or slightly after the on-off valve V3 is opened.

[0052] Because the on-off valves V5 to V8 were closed immediately before the on-off valves were switched, the pressures in the lines 44, 38, 50, 54, and 56 were approximately at the supercritical state-guaranteed pressure. Of course, the pressure in the first supply line 34 was also approximately at the supercritical state-guaranteed pressure. This prevents a temporary drop in the pressure in the processing vessel 12 immediately after the on-off valve V3 is opened, and prevents or significantly suppresses a sudden change in the pressure in the processing vessel 12 before and after the on-off valves are switched.

[0053] If the pressure in the lines 44, 38, 50, 54, and 56 were, for example, normal pressure immediately before the switching of the on-off valves, some of the CO2 in a supercritical state in the processing vessel 12 would suddenly flow out into the lines 44, 38, 50, 54, and 56 immediately after the on-off valve V3 was opened, causing a temporary and sudden drop in the pressure in the processing vessel 12 (for example, a drop of about 1 MPa). This phenomenon is indicated by reference character Pd in ​​the graph of FIG. 4A. However, this phenomenon does not occur in this embodiment, as is clear from the graph of FIG. 4B. If the pressure after the drop were to become lower than the critical pressure of the mixed fluid (CO2 + IPA), pattern collapse could occur.

[0054] As described above, if the pressure inside the processing vessel 12 temporarily drops, the pressure inside the processing vessel 12 may immediately rise due to feedback control, resulting in an overshoot that exceeds the set value. This is undesirable from the viewpoint of control stability, but according to this embodiment, such an event does not occur, or even if it does occur, it is negligibly small.

[0055] Furthermore, the control unit 100 sends a command to the pressure regulating valve 40 to maintain the opening at the initial opening (meaning the opening that the pressure regulating valve 40 should achieve at the start of the circulation process; the same applies below) until just before the circulation process starts (just before feedback control starts). Almost simultaneously with the start of the circulation process, the control unit 100 switches the opening adjustment of the pressure regulating valve 40 to feedback control. As a result, the opening of the pressure regulating valve 40 comes to be controlled by the above-mentioned feedback control based on the measurement value of the pressure sensor designated by the reference symbol PS.

[0056] The initial opening degree may be the opening degree of the pressure regulating valve 40 when the pressure inside the processing vessel 12 is stable at a set value (set pressure) during one (or multiple) circulation steps (a circulation step for processing another substrate W) immediately before the circulation step to be started (hereinafter also referred to as the "stable opening degree"). This stable opening degree may be the average value of the valve opening degree during the final predetermined period of the circulation step (e.g., the last 10 seconds), or may be the average value of the valve opening degree during the circulation step excluding the period immediately after the start of the circulation step. When a new (never used) pressure regulating valve 40 is used, the initial opening degree may be determined based on a specification sheet provided by the manufacturer of the pressure regulating valve 40 or by an operational test.

[0057] By determining the initial opening of the pressure regulating valve 40 as described above, fluctuations in the pressure inside the processing vessel 12 at the start of feedback control can be suppressed, resulting in stable control. If an inappropriate initial opening is set, fluctuations in the pressure inside the processing vessel 12 will occur immediately after the start of feedback control, resulting in unstable control (e.g., hunting). Furthermore, determining the initial opening of the pressure regulating valve 40 as described above has the advantage of being able to address deterioration of the pressure regulating valve 40 over time.

[0058] The above advantages will be described in detail below. An example of the structure of the pressure regulating valve 40 is shown in FIG. 5. A tapered valve element 401 is inserted into a tapered valve seat 402 that is complementary to the valve element 401. An actuator 403 moves the valve element 401 up and down, thereby changing the aperture of the pressure regulating valve 40. As the valve element 401 moves upward (downward), the gap between the outer circumferential surface of the valve element 401 and the inner circumferential surface of the valve seat 402 becomes larger (smaller), i.e., the valve aperture becomes larger (smaller). As the valve aperture becomes larger (smaller), the flow of CO2 from the inlet port 404 to the outlet port 405 increases (decreases), and as a result, the internal pressure of the processing vessel 12, which is connected to the inlet port via the exhaust line 38, decreases (increases).

[0059] The control unit 100 performs feedback control to change the position of the pressure regulating valve 40 by a certain distance (manipulated variable (MV)) based on the deviation between the measured value (PV) of the pressure in the processing vessel 12 and the set value (SV) so that the pressure in the processing vessel 12 is maintained at the set value. For this reason, the actuator 403 has a built-in valve position sensor (not shown) (which is a sensor for the manipulated variable (MV)) for detecting the position of the valve element 401.

[0060] The surfaces of the opposing valve element 401 and valve seat 402 wear over time. As a result of wear, the actual valve opening (the gap between the valve element and the valve seat) for the same valve element position (vertical position in the figure) gradually increases. Therefore, if the initial opening command value (valve element position command value) for a long-used pressure control valve 40 at the start of the flow process is set to the same value as for a new pressure control valve 40, the actual initial opening (the gap between the valve element and the valve seat) of the pressure control valve 40 at the start of the flow process will be excessively large, potentially causing a temporary drop in pressure inside the processing vessel 12 immediately after the start of feedback control. If this pressure drop falls below the supercritical state guarantee pressure described above, pattern collapse may occur. Furthermore, a problem of unstable control may occur immediately after the start of feedback control.

[0061] In contrast to this, in this embodiment, the position of the valve element 401 (detected by the valve position sensor) corresponding to the stable opening of the pressure regulating valve 40 in the circulation process carried out relatively recently, for example, immediately before, is stored, and this stored position of the valve element 401 is used as the initial position (initial opening) of the pressure regulating valve 40 in the circulation process to be carried out from now on. This makes it possible to solve the problems of the pressure drop and unstable pressure control immediately after the start of feedback control.

[0062] In the flow process, supercritical CO2 supplied from the second fluid supply unit 22 into the processing vessel 12 flows in the region above the substrate and is then discharged from the fluid discharge unit 24. At this time, a laminar flow of supercritical CO2 flowing approximately parallel to the surface of the substrate W is formed in the processing vessel 12. IPA in the mixed fluid (IPA+CO2) on the surface of the substrate W exposed to the laminar flow of supercritical CO2 is gradually replaced with supercritical CO2. Eventually, almost all of the IPA on the surface of the substrate W is replaced with supercritical CO2.

[0063] The mixed fluid consisting of IPA and supercritical CO2 discharged from the fluid discharge portion 24 flows through the discharge line 38 (and the branch discharge lines 54, 56) and is then recovered. The IPA contained in the mixed fluid can be separated and reused. Note that in the circulation process, the on-off valves V6, V7 may be opened or closed depending on the desired flow rate, etc.

[0064] [Discharge process] Once the replacement of IPA with supercritical CO2 is complete, as shown in FIG. 2D, the on-off valve V2 is closed to stop the supply of supercritical CO2 to the processing vessel 12, and the set pressure of the processing vessel 12 is reduced to atmospheric pressure (time t4 in FIG. 3). At this time, the on-off valve V4 on the bypass line 44 may be opened. This significantly increases the aperture of the pressure adjustment valve 40 (e.g., fully opens), and the pressure in the processing vessel 12 decreases to atmospheric pressure. Accordingly, the supercritical CO2 present within the pattern on the substrate W becomes gaseous and escapes from the pattern, and the gaseous CO2 is exhausted from the processing vessel 12. Instead of lowering the set pressure of the processing vessel 12 to atmospheric pressure, the control unit 100 may issue a command signal to the pressure adjustment valve 40 to increase its aperture. In the exhaust process, the set pressure of the processing vessel 12 may be gradually reduced to atmospheric pressure. This completes the drying of the substrate W.

[0065] [Export process] The plate 18 of the tray 14 carrying the dried substrate W moves out of the processing vessel 12 to the substrate transfer position. The substrate W is removed from the plate 18 by a substrate transport arm (not shown) and is placed in, for example, a substrate processing vessel (not shown).

[0066] Second embodiment of drying method Next, a second embodiment of the drying method will be described with reference to Figures 6A and 6B. The second embodiment differs from the first embodiment only in the pressurization process, and only the pressurization process will be described. The second embodiment utilizes an exhaust line 66 and an on-off valve V10, which were not used in the first embodiment. Note that in the second embodiment, as in the first embodiment, on-off valve V9 is normally open and on-off valve V11 is normally closed during the pressurization process. Also, on-off valve V8 is normally closed.

[0067] <Deceleration boost stage> During the deceleration / pressurization stage, as shown in FIG. 6A, the on-off valves V2, V3, V5-V7 are closed, and the on-off valves V1, V4, and V10 are open. During the deceleration / pressurization stage, a portion of the CO2 delivered in a supercritical state from the supercritical fluid supply device 30 to the main supply line 32 flows into the exhaust line 66, and the remaining portion flows into the first supply line 34. The CO2 that flows into the exhaust line 66 is either disposed of in the factory exhaust duct or recovered for reuse. Because a portion of the CO2 flowing through the main supply line 32 is released into the exhaust line 66, the flow rate of CO2 flowing into the first supply line 34 decreases. The exhaust line 66 is also referred to as a "relief line" because it releases excess processing fluid relative to the desired inflow flow rate of the processing fluid into the processing vessel 12 or the desired pressurization rate of the processing vessel 12 during the deceleration / pressurization stage.

[0068] The CO2 that has flowed into the first supply line 34 flows into the processing vessel 12 via the first fluid supply unit 21, and also flows into the bypass line 44. Since a portion of the CO2 flowing through the first supply line 34 is released into the bypass line 44, the flow rate of CO2 flowing from the first supply line 34 into the processing vessel 12 further decreases.

[0069] The CO2 that flows into the bypass line 44 is blocked at the on-off valves V5 to V8 because the on-off valves V5 to V8 are closed. That is, the lines 44, 38, 50, 54, and 56 are filled with CO2. Until the internal pressure of the lines 44, 38, 50, 54, and 56 increases, some of the CO2 that flows into the first supply line 34 escapes to the lines 38, 50, 54, and 56 via the bypass line 44. The internal pressure of the lines 44, 38, 50, 54, and 56 increases in a relatively short time, but until then, some of the CO2 that flows into the first supply line 34 escapes to the bypass line 44. Therefore, in the initial stage of the deceleration / pressure increase phase, a portion of the CO2 flowing through the main supply line 32 is vented to the exhaust line 66, and a portion of the CO2 flowing into the first supply line 34 is vented to the bypass line 44, thereby significantly reducing the flow rate of CO2 flowing from the first supply line 34 into the processing vessel 12. Even after the internal pressure of the lines 44, 38, 50, 54, and 56 increases, a portion of the CO2 flowing through the main supply line 32 is vented to the exhaust line 66, so the flow rate of CO2 flowing from the first supply line 34 into the processing vessel 12 continues to be reduced (although it increases slightly). Note that FIG. 6A shows the state after the internal pressure of the lines 44, 38, 50, 54, and 56 increases. <Normal pressure boost stage> Next, as shown in FIG. 6B, the on-off valve V10 is closed to transition from the deceleration pressurization stage to the normal pressurization stage. As can be seen by comparing FIGS. 2B and 6B, the flow / retention state of CO2 during the normal pressurization stage in the second embodiment is the same as that during the normal pressurization stage in the first embodiment. In the second embodiment, the transition from the deceleration pressurization stage to the normal pressurization stage can be performed, for example, when the detected pressure in the treatment vessel 12 exceeds a predetermined threshold. Alternatively, the transition can be performed when a predetermined time (e.g., approximately 10 seconds) has elapsed since the start of the deceleration pressurization stage. The transition from the normal pressurization stage to the circulating process can be performed in the same manner as in the first embodiment. In the second embodiment, as in the first embodiment, it is preferable to fix the aperture of the pressure regulating valve 40 to the initial aperture in the circulating process, described later, to ensure a smooth transition to the circulating process, described later.

[0070] Third embodiment of drying method Next, a third embodiment of the drying method will be described with reference to Figures 7A, 7B, and 7C. The third embodiment differs from the first embodiment only in the pressurization process, and only the pressurization process will be described. The third embodiment also utilizes the exhaust line 66 and on-off valve V10, which were not used in the first embodiment. Note that, in the third embodiment, as in the first embodiment, on-off valve V9 is normally open and on-off valve V11 is normally closed during the pressurization process. Furthermore, on-off valve V8 is normally closed.

[0071] <Deceleration boost stage> 7A, during the deceleration / pressure-up stage, the on-off valves V4 to V7 are closed, and the on-off valves V1 to V3 and V10 are open. During the deceleration / pressure-up stage, as in the second embodiment, a portion of the CO2 delivered in a supercritical state from the supercritical fluid supply device 30 to the main supply line 32 flows into the exhaust line 66, and the remaining portion flows into the first supply line 34. The CO2 that flows into the exhaust line 66 is either disposed of in the factory exhaust duct or recovered for reuse. Because a portion of the CO2 flowing through the main supply line 32 is released into the exhaust line 66, the flow rate of CO2 that flows into the first supply line 34 and then into the processing vessel 12 is reduced. Therefore, the flow rate of CO2 flowing into the processing vessel 12 from the first supply line 34 is kept significantly low, and the rate at which the internal pressure of the processing vessel 12 increases is also kept low.

[0072] Because the on-off valve V3 is open, the CO2 that flows into the processing vessel 12 flows out into the exhaust line 38. Therefore, particles that were stirred up by the CO2 that flowed into the processing vessel 12 at the beginning of the deceleration and pressure increase phase are exhausted outside the processing vessel 12. These particles were attached to the inner wall surface of the processing vessel 12 or the surface of the tray 14. The CO2 that flows into the exhaust line 38 is blocked by the on-off valves V5 to V8, which are closed. Furthermore, because the on-off valve V4 is closed, the CO2 is blocked on both sides of the on-off valve V4. Therefore, the CO2 fills the lines 44, 38, 50, 54, and 56. The internal pressure of the lines 44, 38, 50, 54, and 56 increases in a relatively short time.

[0073] As shown in FIG. 7B, in the third embodiment, at least one (or all) of the on-off valves V5-V7 may be opened at least initially during the deceleration pressure increase phase, and then closed. Opening at least one of the on-off valves V5-V7 allows CO2 to flow smoothly downstream through at least one of the lines 38, 54, and 56 (compared to when all of the on-off valves V5-V7 are closed and the lines 38, 54, and 56 are blocked), thereby facilitating the discharge of particles from the processing vessel 12. Alternatively, at least one of the on-off valves V5-V7 may be opened throughout the entire deceleration pressure increase phase, and then closed simultaneously with the transition to the normal pressure increase phase. In this case, it is preferable to keep the set pressure of the pressure adjustment valve 40 as low as possible. This allows CO 2 that flows out of the treatment vessel 12 into the discharge line 38 immediately after the start of the deceleration pressure increase stage (at this time, the primary pressure of the pressure adjustment valve 40 is low) to easily pass through the pressure adjustment valve 40. <Normal pressure boost stage> Next, as shown in FIG. 7C, the on-off valves V3 and V10 are closed to transition from the deceleration pressurization stage to the normal pressurization stage. If at least one of the on-off valves V5 to V7 is open at the end of the deceleration pressurization stage, as shown in FIG. 7B, the open on-off valves (V5 to V7) are closed. In the third embodiment, the transition from the deceleration pressurization stage to the normal pressurization stage can also be performed, for example, when the detected pressure in the processing vessel 12 exceeds a predetermined threshold value or when a predetermined time (e.g., approximately 10 seconds) has elapsed since the deceleration pressurization stage. FIG. 7C differs from FIG. 2B in that the on-off valve V4 is closed, but the lines 44, 38, 50, 54, and 56 are filled with high-pressure CO2, as in FIG. 2B. Therefore, by closing the on-off valve V1 from the state shown in FIG. 7C and opening the on-off valves V2, V5, and V7, a smooth transition from the normal pressurization stage (pressurization process) to the circulation process can be achieved. In the third embodiment, similarly to the first embodiment, in order to smoothly transition to the circulation process described later, it is preferable to fix the opening degree of the pressure regulating valve 40 to the initial opening degree in the circulation process described later.

[0074] In carrying out the third embodiment, the bypass line 44 and the on-off valve V4 are not necessarily required, and the bypass line 44 and the on-off valve V4 can be omitted. Even without the bypass line 44, it is possible to prevent the pattern from collapsing by releasing a portion of the CO2 that has flowed through the main supply line 32 into the exhaust line 66 during the deceleration and pressure increase stage.

[0075] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0076] The substrate W to be processed is not limited to a semiconductor wafer, but may be any other type of substrate used in manufacturing semiconductor devices, such as a glass substrate or a ceramic substrate.

[0077] In the above embodiment, two fluid supply units (21, 22) are provided in the treatment vessel 12, and these two fluid supply units are used separately in the pressurization step and the circulating step. This configuration and operation are preferable for the reasons described above, but are not limited to this. That is, for example, a single fluid supply unit may be provided in the treatment vessel 12, and both the pressurization step and the circulating step may be performed by supplying the treatment fluid to the treatment vessel via the single fluid supply unit. In this case, too, a bypass line may be provided in the supply line connected to the single fluid supply unit, and the deceleration and pressurization step may be performed while part of the treatment fluid (CO2) is released to the exhaust line via the bypass line.

[0078] For ease of explanation, the supply lines are referred to as the "main supply line 32," the "first supply line 34," and the "second supply line 36" at the branch point 33. However, this is for the sake of convenience and is not intended to be limiting. For example, the main supply line 32 and the first supply line 34 may be considered as a series of (first) supply lines (or main supply lines) connecting the supercritical fluid supply apparatus 30 and the processing vessel 12, and the second supply line 36 may be considered as branching off from the series of first supply lines (32+34) at the branch point 33. Other similar interpretations are also possible. The above points should be noted particularly when interpreting the second and third embodiments. In the second and third embodiments, the exhaust line 66, i.e., the relief line, is not limited to being located at the position shown in FIG. 1 . For example, the exhaust line 66 may be connected to a branch point located between the branch point 33 and the branch point 42 of the first supply line 34. [Explanation of symbols]

[0079] 12 Processing container 18 Substrate holder (plate) 21 First fluid supply section 24 Fluid discharge part 34 First Supply Line 38 Discharge Line 42 First Branch 44 Bypass Line 46 Connection Points V4 Bypass shutoff valve

Claims

1. 1. A substrate processing apparatus that dries a substrate having a liquid attached to its surface by using a processing fluid in a supercritical state, a processing vessel that accommodates the substrate; a substrate holder configured to horizontally hold the substrate with the surface facing upward in the processing chamber; a supply line for supplying a processing fluid into the processing vessel; a supply on-off valve provided in the supply line; a discharge line connected to a discharge part provided in the treatment vessel and configured to discharge a treatment fluid from the treatment vessel; a first discharge on-off valve provided in the discharge line; one or more second discharge on-off valves provided in the discharge line downstream of the first discharge on-off valve; a bypass line connecting the supply line and the discharge line, which allows at least a portion of the processing fluid flowing through the supply line to be discharged to the discharge line without passing through the processing vessel; a bypass on-off valve that opens and closes the bypass line; a pressure regulating valve provided in the discharge line to regulate the pressure inside the processing vessel; a control unit for controlling the operation of the substrate processing apparatus; Equipped with a connection point where the bypass line is connected to the exhaust line is set between the processing vessel and the pressure adjustment valve, the first exhaust on-off valve is provided between the connection point and the processing vessel, and the one or more second exhaust on-off valves are provided downstream of the pressure adjustment valve, the control unit opens the supply on-off valve and the bypass on-off valve and closes the first exhaust on-off valve in a first state during a first period, thereby increasing the pressure in the processing vessel to a pressure equal to or higher than the critical pressure of the processing fluid by using the processing fluid supplied to the processing vessel from the supply line; The control unit opens the one or more second discharge on-off valves at least at an early stage of the first period, thereby allowing the processing fluid that has flowed from the bypass line into the discharge line to flow downstream of the one or more second on-off valves in the discharge line. the control unit closes the one or more second exhaust on-off valves at least at the end of the first period, thereby filling at least a section of the exhaust line from the first exhaust on-off valve to the at least one second exhaust on-off valve with the treatment fluid flowing into that section from the bypass line, thereby increasing the pressure in that section. Substrate processing equipment.

2. The substrate processing apparatus of claim 1, wherein the control unit opens the supply on-off valve, the first exhaust on-off valve, and the one or more second exhaust on-off valves during a second period following the first period, and closes the bypass on-off valve in a second state, thereby maintaining the pressure in the processing vessel at a pressure equal to or higher than the critical pressure of the processing fluid, and allowing the processing fluid to be supplied from the supply line to the processing vessel and the processing fluid to be discharged from the discharge unit via the discharge line.

3. A substrate processing apparatus as described in claim 1, wherein the processing fluid flows into the processing vessel in a gaseous state at least at the beginning of the first period.

4. A substrate processing apparatus as described in claim 1, wherein the control unit opens the one or more second exhaust opening / closing valves before the pressure in the processing vessel rises to the critical pressure of the processing fluid.

5. A substrate processing apparatus as described in claim 1, wherein the rate at which the pressure rises in the processing vessel after closing the one or more second exhaust on-off valves is greater than the rate at which the pressure rises in the processing vessel before closing the one or more second exhaust on-off valves.

6. A substrate processing apparatus as described in claim 1, wherein an orifice is provided in the supply line.

7. The system further comprises a branch discharge line branching off from the discharge line upstream of the pressure regulating valve, and an on-off valve provided on the branch discharge line; 2. The substrate processing apparatus of claim 1, wherein the control unit opens the on-off valve of the branch exhaust line to exhaust air from the processing vessel through the branch exhaust line when depressurizing the processing vessel after completion of replacement of the liquid with the processing fluid in the processing vessel.

8. A substrate processing method for drying a substrate having a liquid adhering to its surface using a processing fluid in a supercritical state in a substrate processing apparatus, comprising: The substrate processing apparatus includes: a processing vessel that accommodates the substrate; a substrate holder configured to horizontally hold the substrate with the surface facing upward in the processing chamber; a supply line for supplying a processing fluid into the processing vessel; a supply on-off valve provided in the supply line; a discharge line connected to a discharge part provided in the treatment vessel and configured to discharge a treatment fluid from the treatment vessel; a first discharge on-off valve provided in the discharge line; one or more second discharge on-off valves provided in the discharge line downstream of the first discharge on-off valve; a bypass line connecting the supply line and the discharge line, which allows at least a portion of the processing fluid flowing through the supply line to be discharged to the discharge line without passing through the processing vessel; a bypass on-off valve that opens and closes the bypass line; a pressure regulating valve provided in the discharge line to regulate the pressure inside the processing vessel; a control unit for controlling the operation of the substrate processing apparatus; Equipped with a connection point where the bypass line is connected to the exhaust line is set between the processing vessel and the pressure adjustment valve, the first exhaust on-off valve is provided between the connection point and the processing vessel, and the one or more second exhaust on-off valves are provided downstream of the pressure adjustment valve, The substrate processing method includes: during a first period, the supply on-off valve and the bypass on-off valve are opened, and the first exhaust on-off valve is closed, so that a first state is established, and a pressure in the processing vessel is increased to a pressure equal to or higher than a critical pressure of the processing fluid by the processing fluid supplied to the processing vessel from the supply line; At least in an initial stage of the first period, the one or more second on-off valves are opened, thereby causing the treatment fluid that has flowed from the bypass line into the discharge line to flow downstream of the one or more second on-off valves in the discharge line; closing the one or more second on-off valves at least at the end of the first period, thereby filling at least a section of the discharge line from the first discharge on-off valve to the at least one second discharge on-off valve with the treatment fluid flowing into that section from the bypass line, thereby increasing the pressure in that section; A method for processing a substrate, comprising:

9. A substrate processing method as described in claim 8, wherein during a second period following the first period, the supply on-off valve, the first exhaust on-off valve, and the one or more second exhaust on-off valves are opened, and the bypass on-off valve is closed in a second state, so that the pressure inside the processing vessel is maintained at a pressure equal to or higher than the critical pressure of the processing fluid, and the processing fluid is supplied from the supply line to the processing vessel and discharged from the discharge section via the discharge line.

10. The substrate processing method of claim 8, wherein the processing fluid flows into the processing vessel in a gaseous state at least at the beginning of the first period.

11. A substrate processing method as described in claim 8, wherein the one or more second exhaust on-off valves are opened before the pressure in the processing vessel rises to the critical pressure of the processing fluid.

12. A substrate processing method as described in claim 8, wherein the rate at which the pressure rises in the processing vessel after closing the one or more second exhaust on-off valves is greater than the rate at which the pressure rises in the processing vessel before closing the one or more second exhaust on-off valves.

13. A substrate processing method as described in claim 8, wherein an orifice is provided in the supply line.

14. The substrate processing apparatus further comprises a branch discharge line branching off from the discharge line upstream of the pressure adjustment valve, and an opening / closing valve provided on the branch discharge line; 9. The substrate processing method according to claim 8, further comprising, when depressurizing the processing vessel after completion of replacement of the liquid with the processing fluid in the processing vessel, opening the on-off valve of the branch exhaust line to evacuate the processing vessel through the branch exhaust line.

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