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 in which a laminated structure of integrated circuits is formed on the surface of a substrate such as a semiconductor wafer (hereinafter referred to as a 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 the liquid processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-074103 A 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 a 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 for accommodating the substrate, a substrate holding section for holding the substrate horizontally with the surface facing upward in the processing vessel, a first supply line connected to a first fluid supply section provided in the processing vessel and supplying processing fluid into the processing vessel, a discharge line connected to a discharge section provided in the processing vessel and discharging the processing fluid from the processing vessel, a bypass line branching off from the first supply line at a first branch point set in the first supply line and 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 for opening and closing the bypass line. Effect 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 description of the drawings]

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

[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 a supercritical drying process.

[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 in the processing vessel 10.

[0010] In one embodiment, the tray 14 has a lid 16 that covers an opening provided in a side wall of the processing vessel 12, and a horizontally extending substrate support plate (substrate holder) 18 (hereinafter simply referred to as "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 the plate 18 is 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 in the internal space of the processing vessel 12, and the lid 16 closes the opening in the side wall of the processing vessel 12 (the state shown in FIG. 1). At the substrate transfer position, the plate 18 is outside the processing vessel 12, and the substrate W can be transferred 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 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 in which 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 is formed between the periphery of the tray 14 in the processing position and the inner wall surface of the processing vessel 12, serving as a communication passage connecting the upper space 12A and the lower space 12B. Furthermore, a through hole may be provided in the plate 18 near the lid 16 to connect 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 transport arm (not shown) enters the vessel body, and substrates are transferred between the substrate mounting table and the substrate transport 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 (hereinafter, for convenience, also referred to as "CO2") in a supercritical state.

[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 can be configured by a through hole formed in the bottom wall of the processing vessel 12. The first fluid supply unit 21 may 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 at the processing position. The second fluid supply unit 22 can be provided, for example, on one side wall (first side wall) of the processing vessel 12 or in its vicinity. 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 having 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 therein, similar to the second fluid supply unit 22. The fluid discharge unit 24 can be provided, for example, on the side wall (second side wall) opposite to the first side wall of the processing vessel 12 on which the second fluid supply unit 22 is provided, or in the vicinity thereof.

[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 passage 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, a supply / discharge system for supplying and discharging CO2 to and from the processing vessel 12 in the supercritical processing apparatus will be described. In the piping system diagram shown in FIG. 1, the member indicated by a circled T is a temperature sensor, and the member indicated by a circled P is a pressure sensor. The member indicated by the symbol OLF is an orifice (fixed throttle) that reduces the pressure of CO2 flowing in the downstream piping to a desired value. The member indicated by a squared SV is a safety valve (relief valve) that prevents damage to the piping or components of the supercritical processing apparatus such as the processing vessel 12 due to unexpected overpressure. The member indicated by the symbol F is a filter that removes contaminants such as particles contained in CO2. The member indicated by the symbol CV is a check valve (non-return valve). The member indicated by a circled FV is a flow meter. The member indicated by a squared H is a heater for adjusting the temperature of 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 has a supercritical fluid supplying apparatus 30. In this embodiment, the supercritical fluid is carbon dioxide in a supercritical state (hereinafter, also referred to as "supercritical CO2"). The supercritical fluid supplying apparatus 30 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 30 has the ability to deliver supercritical CO2 at a supercritical state guarantee pressure (specifically, about 16 MPa) described below or a pressure higher than that.

[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 in a supercritical state into the main supply line 32, but may become gaseous due to subsequent expansion or temperature change. In this specification, a member called a "line" may be composed of 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] A drain line 38 is connected to the fluid drain 24 of the processing vessel 12. A pressure regulating valve 40 is provided in the drain line 38. By adjusting the opening degree 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) 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, a detection value of a pressure sensor with 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 directly measured by a pressure sensor provided in the processing vessel 12, or may be indirectly measured 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 device (or a substrate processing system including the supercritical processing device). The arithmetic unit 101 controls the operation of the supercritical processing device by reading and executing the programs stored in the storage unit 102. The programs may be recorded in 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 magnet 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 provided on the first supply line 34. The bypass line 44 is connected to the discharge line 38 at a connection point 46 provided 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 atmospheric space outside the supercritical processing apparatus or connected to a factory exhaust duct.

[0029] At a branch point 52 set in the discharge line 38, two branch discharge lines 54, 56 branch off from the discharge line 38. The downstream ends of the branch discharge lines 54, 56 merge again with 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 appropriately separated 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 via the purge gas supply line 62.

[0031] An exhaust line 66 branches off from a branch point 64 located on 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-mentioned 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 filled in black are in the closed state, and the valves not filled in are in the open state. In Fig. 2A to 2D, the lines through which CO2 flows are shown by thick solid lines, and the lines through which CO2 is retained with a certain level of pressure are shown by thick dashed lines.

[0034] The horizontal axis of the graph in Fig. 3 is time, and the vertical axis is the internal pressure of the treatment vessel 12. On the horizontal axis of the graph in Fig. 3, "2A" corresponds to the decelerated pressurization stage of the pressurization process, "2B" corresponds to the normal pressurization stage of the pressurization 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 a puddle of IPA formed on its surface, is placed on the plate 18 of a tray 14 waiting at a substrate transfer position by a substrate transport arm (not shown). Note that this substrate W has been subjected to, for example, (1) chemical processing such as wet etching and chemical cleaning, (2) a rinsing process in which the chemical solution is washed away with a rinsing solution, and (3) an IPA replacement process in which the rinsing solution is replaced with IPA to form a puddle of IPA, in a single-wafer cleaning apparatus (not shown) in sequence. When the tray 14 on which the substrate W is placed is moved to the processing position, a sealed processing space is formed in the processing container 12, and the substrate W is positioned within the processing space.

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

[0037] In addition, from the start of the pressurization step to the end of the depressurization step, the on-off valve V9 is normally open, and the on-off valves V10 and V11 are normally closed, and no reference will be made to these on-off valves V9 to V11. In addition, the on-off valve V8 may be normally closed in the pressurization and circulation steps and open in the depressurization step. The 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 necessary. When the on-off valve V8 is opened, exhaust can be performed without passing through the pressure regulating valve 40, so that the exhaust or depressurization time can be shortened. In the following description, the on-off valve V8 is assumed to be normally closed.

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

[0039] In addition, by changing the aperture of the pressure regulating valve 40, 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. For this reason, the aperture in the deceleration and pressure increase stage may be different from the initial aperture in the circulation process described later.

[0040] 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 30 drops significantly when it flows into the processing vessel 12, which has a relatively large volume and is in a normal pressure state. That is, in the early stage 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., about 8 MPa), so that CO2 is in a gaseous state. Since the difference between the pressure in the first supply line 34 and the pressure in the processing vessel 12, which is in a normal pressure state, is very large, CO2 flows into the processing vessel 12 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 substrate W or flows near the substrate W, the puddle of IPA on the periphery of the substrate W may collapse (local evaporation or fluctuation), causing the pattern to collapse.

[0041] In this embodiment, since the orifice (OLF) is provided in the first supply line 34, the flow rate of CO2 flowing from the first fluid supply unit 21 into the processing vessel 12 is lower than that in the case where there is no orifice, so that the pattern collapse due to the above-mentioned mechanism can be suppressed.

[0042] In this embodiment, the CO2 that flows from the first fluid supply unit 21 into the processing vessel 12 collides with the plate 18 of the tray 14, and then bypasses the plate 18 and enters the upper space 12A in which 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, in the deceleration and pressure increase stage, i.e., in the early stage of introduction of CO2 into the processing vessel 12, a part of the CO2 flowing through the first supply line 34 is diverted to the bypass line 44, thereby further reducing the flow rate of CO2 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] If 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 as shown by the arrow in Fig. 2A. In this embodiment, in order to eliminate this possibility, a part 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 introduction of 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 supplying CO2 from the first supply line 34 to the processing vessel 12.

[0047] <Normal 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 value. Alternatively, the switching can be performed when a predetermined time (for example, about 10 seconds as mentioned 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 regulating valve 40 to the initial aperture in the flow process described later, in order to smoothly transition to the flow process described later.

[0048] With the switching of the on-off valves, the CO2 that had flowed from the bypass line 44 into the discharge line 38 and flowed through the discharge line 38 and the branch discharge lines 54 and 56 is stopped by the on-off valves V5 to V7. The on-off valve V8 is also closed, so that the line 50 is also closed. Therefore, the lines 44, 38, 50, 54, and 56 are filled with CO2, and the pressure in the 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 treatment vessel 12 increases at a higher pressure increase rate than in the deceleration 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 a supercritical state. When the CO2 inside the processing vessel 12 becomes a supercritical state, the IPA on the substrate W starts 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 above-mentioned normal pressure increase step is continued until the pressure reaches a pressure (supercritical state guarantee pressure) that guarantees that CO2 in the processing vessel 12 is maintained in a supercritical state, regardless of the IPA concentration and temperature in the mixed fluid (CO2+IPA) on the substrate W. The supercritical state guarantee pressure is approximately 16 MPa. When the pressure in the processing vessel 12 reaches the above-mentioned supercritical state guarantee pressure, pattern collapse due to local phase change (e.g., vaporization) of the mixed fluid on the surface of the substrate W no longer occurs. Note that such a local phase change occurs due to non-uniformity in the IPA concentration in the mixed fluid on the surface of the substrate W, and may occur particularly in an area exhibiting an IPA concentration that increases the critical temperature.

[0051] [Distribution process] When it is confirmed by the pressure sensor that the pressure inside the processing vessel 12 has reached the above-mentioned 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 regulating valve 40 is switched to feedback control, and the process proceeds to the circulation step (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] Since the on-off valves V5 to V8 were closed until immediately before the on-off valves were switched to open or closed, the pressures in the lines 44, 38, 50, 54, and 56 are generally at the supercritical state guarantee pressure. Of course, the pressure in the first supply line 34 is also generally at the supercritical state guarantee pressure. This makes it possible to prevent a temporary drop in pressure in the processing vessel 12 immediately after the on-off valve V3 is opened, and makes it possible to prevent or significantly suppress a rapid change in 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 is, for example, normal pressure immediately before the switching of the on-off valve, a portion of the CO2 in the supercritical state in the processing vessel 12 will suddenly flow out to the lines 44, 38, 50, 54, and 56 immediately after the on-off valve V3 is opened, causing the pressure in the processing vessel 12 to suddenly drop temporarily (for example, by about 1 MPa). This phenomenon is indicated by reference character Pd in ​​the graph of FIG. 4A. On the other hand, this phenomenon does not occur in this embodiment, and this is clear from the graph of FIG. 4B. If the pressure after the drop becomes smaller than the critical pressure of the mixed fluid (CO2+IPA), the pattern may collapse.

[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, causing an overshoot that exceeds the set value. This is undesirable from the viewpoint of control stability, but according to the present 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) in one (or multiple) circulation steps (a circulation step in processing another substrate W) immediately before the circulation step to be started (hereinafter also referred to as "stable opening degree"). This stable opening degree may be the average value of the valve opening degree in the last predetermined period (e.g., the last 10 seconds) of the circulation step, 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 table provided by the manufacturer of the pressure regulating valve 40 or by an operation test.

[0057] By determining the initial opening of the pressure regulating valve 40 as described above, it is possible to suppress fluctuations in the pressure inside the processing vessel 12 at the start of feedback control, and the control becomes stable. If an inappropriate initial opening is set, fluctuations in the pressure inside the processing vessel 12 occur immediately after the start of feedback control, making the control unstable (e.g., hunting occurs). In addition, by determining the initial opening of the pressure regulating valve 40 as described above, there is also the advantage that it is possible to deal with 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 body 401 is inserted into a tapered valve seat 402 that is complementary to the valve body 401. The actuator 403 moves the valve body 401 up and down, thereby changing the aperture of the pressure regulating valve 40. When the valve body 401 is displaced upward (downward), the gap between the outer circumferential surface of the valve body 401 and the inner circumferential surface of the valve seat 402 becomes larger (smaller), that is, the valve aperture becomes larger (smaller). When the valve aperture becomes larger (smaller), the flow of CO2 from the inlet port 404 to the outlet port 405 increases (decreases), and accordingly the internal pressure of the processing vessel 12 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) (this is a sensor of the manipulated variable (MV)) for detecting the position of the valve element 401.

[0060] The surfaces of the valve body 401 and the valve seat 402 facing each other wear with time of use. As the valve body wears, the actual valve opening (the gap between the valve body and the valve seat) for the same valve body position (the vertical position in the figure) gradually increases. Therefore, if the command value of the initial opening (the command value of the valve body position) at the start of the flow process for the pressure regulating valve 40 that has been used for a long time is made the same as that for a new pressure regulating valve 40, the actual initial opening (the gap between the valve body and the valve seat) of the pressure regulating valve 40 at the start of the flow process becomes excessive, and a problem may occur in which the pressure in the processing vessel 12 temporarily drops immediately after the start of feedback control. If this pressure drop falls below the above-mentioned supercritical state guarantee pressure, the pattern may collapse. In addition, a problem may occur in which the control is not stable 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 in the relatively recent past, 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 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 part 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. 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] When the replacement of IPA with supercritical CO2 is completed, 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 lowered to normal pressure (time t4 in FIG. 3). At this time, the on-off valve V4 of the bypass line 44 may be opened. As a result, the opening degree of the pressure adjustment valve 40 is significantly increased (for example, fully opened), and the pressure in the processing vessel 12 is lowered to normal pressure. As a result, the supercritical CO2 in the pattern of the substrate W becomes gas and is released from the pattern, and the gaseous CO2 is discharged from the processing vessel 12. Instead of lowering the set pressure of the processing vessel 12 to normal pressure, the control unit 100 may give a command signal to the pressure adjustment valve 40 to increase the opening degree of the pressure adjustment valve 40. In the discharge process, the set pressure of the processing vessel 12 may be lowered to normal pressure in stages. The drying of the substrate W is completed as described above.

[0065] [Export process] The plate 18 of the tray 14 on which the dried substrate W is placed moves to the substrate transfer position out of the processing vessel 12. The substrate W is taken out of the plate 18 by a substrate transport arm (not shown) and is accommodated 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 therefore only the pressurization process will be described. The second embodiment utilizes an exhaust line 66 and an on-off valve V10 that were not used in the first embodiment. Note that, in the second embodiment, as in the first embodiment, the on-off valve V9 is normally open and the on-off valve V11 is normally closed in the pressurization process. Also, the on-off valve V8 is normally closed.

[0067] <Deceleration boost stage> In the deceleration and boosting stage, as shown in FIG. 6A, the on-off valves V2, V3, V5 to V7 are closed, and the on-off valves V1, V4, and V10 are opened. In the deceleration and boosting stage, a part of the CO2 sent 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 part flows into the first supply line 34. The CO2 that flows into the exhaust line 66 is disposed of in the factory exhaust duct or is recovered for reuse. Since a part of the CO2 that has flowed 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 called a "relief line" in the sense that it releases excess processing fluid relative to the desired inflow flow rate of the processing fluid into the processing vessel 12 or the desired boosting rate of the processing vessel 12 in the deceleration and boosting 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 is further reduced.

[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 early stage of the deceleration pressure increase stage, in addition to releasing a part of the CO2 flowing through the main supply line 32 to the exhaust line 66, a part of the CO2 flowing into the first supply line 34 is released to the bypass line 44, so that the flow rate of CO2 flowing from the first supply line 34 into the processing vessel 12 can be kept quite low. Even after the internal pressure of the lines 44, 38, 50, 54, and 56 increases, a part of the CO2 flowing through the main supply line 32 is released to the exhaust line 66, so that the flow rate of CO2 flowing from the first supply line 34 into the processing vessel 12 continues to be kept low (although it becomes slightly higher). Note that FIG. 6A shows the state after the internal pressure of the lines 44, 38, 50, 54, and 56 increases. <Normal boost stage> Next, as shown in FIG. 6B, the on-off valve V10 is switched to a closed state to transition from the deceleration pressure increase stage to the normal pressure increase stage. As can be understood by comparing FIG. 2B and FIG. 6B, the flow / retention state of CO2 in the normal pressure increase stage in the second embodiment is the same as that in the normal pressure increase stage in the first embodiment. In the second embodiment, the transition from the deceleration pressure increase stage to the normal pressure increase stage can be performed, for example, when the detected value of the pressure in the treatment vessel 12 exceeds a predetermined threshold value, or alternatively, when a predetermined time (for example, about 10 seconds as described above) has elapsed since the start of the deceleration pressure increase stage. The transition from the normal pressure increase stage to the circulation process can be performed in the same procedure as in the first embodiment. In the second embodiment, as in the first embodiment, it is preferable to fix the opening degree of the pressure regulating valve 40 to the initial opening degree in the circulation process to be described later in order to smoothly transition to the circulation process to be 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 also differs from the first embodiment only in the pressurization process, and only the pressurization process will be described. The third embodiment also uses the exhaust line 66 and the on-off valve V10, which were not used in the first embodiment. Note that in the third embodiment, as in the first embodiment, the on-off valve V9 is normally open and the on-off valve V11 is normally closed in the pressurization process. Also, the on-off valve V8 is normally closed.

[0071] <Deceleration boost stage> In the deceleration pressure increase stage, as shown in FIG. 7A, the on-off valves V4 to V7 are closed, and the on-off valves V1 to V3 and V10 are opened. In the deceleration pressure increase stage, as in the second embodiment described above, a part of the CO2 sent 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 part flows into the first supply line 34. The CO2 that flows into the exhaust line 66 is either discarded in a factory exhaust duct or recovered for reuse. Since a part of the CO2 that has flowed through the main supply line 32 is released into the exhaust line 66, the flow rate of the CO2 that flows into the first supply line 34 and then into the processing vessel 12 is reduced. Therefore, the flow rate of the CO2 that flows into the processing vessel 12 from the first supply line 34 is kept quite low, and the rate of increase in the internal pressure of the processing vessel 12 is also kept low.

[0072] Since the on-off valve V3 is open, the CO2 that has flowed into the processing vessel 12 flows out to the exhaust line 38. Therefore, particles that have been stirred up by the CO2 that has flowed into the processing vessel 12 at the beginning of the deceleration and pressure increase stage are exhausted to the outside of the processing vessel 12. These particles are attached to the inner wall surface of the processing vessel 12 or the surface of the tray 14. The CO2 that has flowed into the exhaust line 38 is blocked at the on-off valves V5 to V8 that are in the closed state. In addition, since the on-off valve V4 is closed, the CO2 is blocked on both sides of the on-off valve V4. Therefore, the lines 44, 38, 50, 54, and 56 are filled with CO2. The internal pressure of the lines 44, 38, 50, 54, and 56 increases in a relatively short time.

[0073] As shown in FIG. 7B, at least one (or all) of the on-off valves V5 to V7 may be opened at least in the initial stage of the deceleration pressure increase stage in the third embodiment, and then the on-off valves V5 to V7 may be closed. When at least one of the on-off valves V5 to V7 is open, CO2 flows smoothly downstream through at least one of the lines 38, 54, and 56 (compared to the case where all of the on-off valves V5 to V7 are closed and the lines 38, 54, and 56 are blocked), which can promote the discharge of particles from the processing vessel 12 described above. At least one of the on-off valves V5 to V7 may be opened during the entire period of the deceleration pressure increase stage, and all of the on-off valves V5 to V7 may be closed at the same time as the transition to the normal pressure increase stage. In this case, it is preferable to keep the set pressure of the pressure regulating valve 40 as low as possible. This allows the CO2 that flows out of the treatment vessel 12 into the exhaust line 38 immediately after the start of the deceleration pressure increase phase (at this time, the primary pressure of the pressure regulating valve 40 is low) to easily pass through the pressure regulating valve 40. <Normal boost stage> Next, as shown in FIG. 7C, the on-off valves V3 and V10 are switched to the closed state to transition from the deceleration pressure increase stage to the normal pressure increase stage. If at least one of the on-off valves V5 to V7 is in the open state at the end of the deceleration pressure increase stage as shown in FIG. 7B, the open on-off valves (V5 to V7) are switched to the closed state. In the third embodiment, the transition from the deceleration pressure increase stage to the normal pressure increase stage can be performed, for example, when the detected pressure value in the treatment vessel 12 exceeds a predetermined threshold value, or when a predetermined time (for example, about 10 seconds as described above) has elapsed since the deceleration pressure increase stage. FIG. 7C differs from FIG. 2B in that the on-off valve V4 is in the closed state, but is the same as FIG. 2B in that the lines 44, 38, 50, 54, and 56 are filled with high-pressure CO2. Therefore, by switching the on-off valve V1 to the closed state from the state shown in FIG. 7C and switching the on-off valves V2, V5 to V7 to the open state, a smooth transition from the normal pressure increase stage (pressurization process) to the circulation process can be performed. 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 addition, in carrying out the third embodiment, the bypass line 44 and the on-off valve V4 are not necessarily required, and it is possible to omit the bypass line 44 and the on-off valve V4. Even without the bypass line 44, it is possible to prevent the pattern from collapsing by releasing a part of the CO2 flowing through the main supply line 32 into the exhaust line 66 during the deceleration and boosting stage.

[0075] The embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms 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 the manufacture of semiconductor devices, such as a glass substrate, a ceramic substrate, or the like.

[0077] In the above embodiment, the treatment vessel 12 is provided with two fluid supply units (21, 22), and these two fluid supply units are used in the pressurization step and the circulation 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 circulation 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 discharge line via the bypass line.

[0078] In this specification, for convenience of explanation, the names of the supply lines are distinguished as "main supply line 32", "first supply line 34" and "second supply line 36" with the branch point 33 as a boundary, but this is only for convenience of explanation and is not limited to this interpretation. For example, the main supply line 32 and the first supply line 34 can be regarded as a series of (first) supply lines (or main supply lines) connecting the supercritical fluid supply device 30 and the processing vessel 12, and the second supply line 36 can be regarded as branching off from the series of first supply lines (32+34) at the branch point 33. Other similar interpretations are also possible. In particular, the above points should be noted in the interpretation of 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 provided at the position shown in FIG. 1, and may be connected to a branch point set between the branch point 33 and the branch point 42 of the first supply line 34. [Explanation of symbols]

[0079] 12 Processing vessel 18 Substrate holder (plate) 21 1st fluid supply section 24 Fluid discharge part 34 First Supply Line 38 Discharge Line 42 First Turning Point 44 Bypass Line 46 Connection points V4 Bypass 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, comprising: a processing vessel for accommodating the substrate; a substrate holder configured to horizontally hold the substrate in the processing chamber with the surface facing upward; a first supply line connected to a first fluid supply unit provided in the processing vessel and configured to supply a processing fluid into the processing vessel; 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 bypass line that branches off from the first supply line at a first branch point set on the first supply line and is connected to the discharge line at a connection point set on the discharge line, and that enables 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; a bypass on-off valve that opens and closes the bypass line; a pressure regulating valve provided in the exhaust line to regulate a pressure in the processing vessel; Equipped with the connection point where the bypass line is connected to the exhaust line is set between the processing vessel and the pressure regulating valve, a first fluid supply unit provided in the processing vessel to discharge a processing fluid into the processing vessel toward a lower surface of the substrate holding unit that holds the substrate, the processing vessel further includes a second fluid supply unit configured to discharge a second fluid in a direction generally along a surface of the substrate toward an area above the substrate held by the substrate holder; the substrate processing apparatus further includes a main supply line connected to a processing fluid supply source that supplies a processing fluid in a supercritical state, the main supply line branches into the first supply line and a second supply line at a second branch point set on the main supply line, and the second supply line is connected to the second fluid supply unit; The substrate processing apparatus includes: a first on-off valve provided between the second branch point and the first branch point; a second on-off valve provided between the second branch point and the second fluid supply portion; A third on-off valve provided between the discharge portion and the connection point; A control unit for controlling an operation of the substrate processing apparatus; Further equipped with the control unit opens the first on-off valve and the bypass on-off valve during a first period, and sets the second on-off valve and the third on-off valve to a first state in which they are closed, thereby increasing the pressure in the processing vessel 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 first supply line; the control unit opens the second on-off valve and the third on-off valve and closes the first on-off valve and the bypass on-off valve in a second state during a second period following the first period, thereby supplying the processing fluid from the second supply line to the processing vessel and discharging the processing fluid from the discharge unit while maintaining a pressure in the processing vessel at a pressure equal to or higher than a critical pressure of the processing fluid, the control unit closes the one or more fourth on-off valves at least at the end of the first period, thereby filling at least a section of the discharge line from the third on-off valve to the fourth on-off valve with the treatment fluid flowing into the section from the bypass line, thereby increasing the pressure in the section; the control unit opens the one or more fourth on-off valves at least at the beginning of the first period, thereby allowing the processing fluid flowing from the bypass line to the discharge line to flow downstream of the one or more fourth on-off valves in the discharge line.

2. a pressure sensor for directly or indirectly detecting a pressure in the processing vessel; 2. The substrate processing apparatus of claim 1, wherein the control unit is configured to feedback-control an opening degree of the pressure adjustment valve during the second period based on a deviation between a set value of the pressure in the processing vessel and a pressure measured by the pressure sensor so that the pressure in the processing vessel becomes the set value.

3. the feedback control of the opening degree of the pressure regulating valve is performed by adjusting a position of a valve body of the pressure regulating valve by an actuator based on the deviation so that the pressure in the processing vessel becomes the set value; 3. The substrate processing apparatus of claim 2, wherein the control unit sets an initial position of the valve body of the pressure regulating valve at the start of the feedback control to a position of the valve body of the pressure regulating valve when the opening degree of the pressure regulating valve is stable during the second period in a substrate processing performed in the past.

4. The substrate processing apparatus according to claim 3 , wherein the previously performed substrate processing is a substrate processing performed immediately before the substrate processing currently being performed.

5. a relief line branching off from the first supply line at a branch point set on the first supply line upstream of the first branch point; an on-off valve provided in the relief line; Further equipped with 2. The substrate processing apparatus of claim 1, wherein when the control unit is increasing the pressure in the processing vessel by the processing fluid supplied from the first supply line to the processing vessel, the control unit opens the bypass opening / closing valve and the opening / closing valve of the relief line to discharge a portion of the processing fluid flowing through the first supply line toward the processing vessel to the relief line, and discharges another portion of the processing fluid flowing through the first supply line toward the processing vessel to the discharge line via the bypass line.

6. 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, comprising: a processing vessel for accommodating the substrate; a substrate holder configured to horizontally hold the substrate in the processing chamber with the surface facing upward; a first supply line connected to a first fluid supply unit provided in the processing vessel and configured to supply a processing fluid into the processing vessel; 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 bypass line that branches off from the first supply line at a first branch point set on the first supply line and is connected to the discharge line at a connection point set on the discharge line, and that enables 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; a bypass on-off valve that opens and closes the bypass line; a pressure regulating valve provided in the exhaust line downstream of the connection point for regulating a pressure in the processing vessel; an on-off valve provided in the discharge line between the discharge portion and the connection point; an on-off valve provided in the discharge line downstream of the pressure regulating valve; A control unit for controlling an operation of the substrate processing apparatus; Equipped with the control unit closes an on-off valve provided between the exhaust unit and the connection point and opens the on-off valve provided downstream of the bypass on-off valve and the pressure adjustment valve at least at an early stage of a pressure increase process in which the pressure in the processing vessel is increased by the processing fluid supplied from the first supply line to the processing vessel, thereby allowing a portion of the processing fluid flowing through the first supply line toward the processing vessel to flow downstream of the on-off valve via the bypass line, the connection point, the pressure adjustment valve and the on-off valve downstream of the pressure adjustment valve.

7. 7. The substrate processing apparatus according to claim 6, wherein the control unit closes the on-off valve provided downstream of the pressure adjustment valve at least at a final stage of the pressurization process, thereby filling at least a section of the discharge line between the on-off valve provided between the discharge unit and the connection point and the on-off valve provided downstream of the pressure adjustment valve with processing fluid flowing into the section from the bypass line, thereby increasing the pressure in the section.

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