Substrate processing method and substrate processing apparatus
The substrate processing apparatus addresses cleanliness issues in supercritical drying by using a controlled fluid system and vacuum cleaning to remove contaminants, ensuring high cleanliness standards.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOKYO ELECTRON LTD
- Filing Date
- 2023-07-25
- Publication Date
- 2026-06-16
AI Technical Summary
Existing substrate drying methods using supercritical fluids do not adequately address the issue of cleanliness, as contaminants can adhere to the processing equipment during the drying process, potentially contaminating the substrate.
A substrate processing apparatus with a controlled fluid supply and discharge system, including a processing container, fluid supply units, and a control unit that performs vacuum cleaning to remove contaminants after the drying process, ensuring the substrate remains clean.
The apparatus improves the cleanliness of the substrate by effectively removing contaminants from the processing equipment, maintaining high cleanliness standards during the drying process.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus.
Background Art
[0002] In the manufacturing process of a semiconductor device that forms a stacked structure of an integrated circuit on the surface of a substrate such as a semiconductor wafer, liquid processing such as chemical solution cleaning or wet etching is performed. When removing liquids or the like adhering to the surface of the substrate by such liquid processing, in recent years, a drying method using a processing fluid in a supercritical state has been increasingly used.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
[0004] The present disclosure provides a technique capable of improving the cleanliness of a substrate after a drying process in a drying process of a substrate using a processing fluid in a supercritical state.
[0005] A substrate processing apparatus according to one embodiment of the present disclosure comprises a processing container capable of containing a substrate, a processing fluid supply unit for supplying a supercritical processing fluid to the processing container in order to perform supercritical drying on the substrate, a fluid discharge unit for discharging fluid from the processing container, the fluid discharge unit having a discharge channel connected to the processing container and an exhaust mechanism provided in the discharge channel, and a control unit that controls at least the processing fluid supply unit and the fluid discharge unit, wherein when no substrate is contained in the processing container, the control unit seals the processing container and prevents fluid from flowing into the processing container, and in this state operates the exhaust mechanism of the fluid discharge unit to evacuate the processing container, thereby reducing the pressure inside the processing container to a predetermined vacuum cleaning pressure and performing a vacuum cleaning process in which contaminants inside the processing container are vaporized and discharged from the processing container.
[0006] According to the embodiments described above, in a substrate drying process using a supercritical processing fluid, the cleanliness of the substrate after the drying process can be improved. [Brief explanation of the drawing]
[0007] [Figure 1] This is a diagram of the piping system of a supercritical drying apparatus according to one embodiment of the present disclosure. [Figure 2] This is a schematic cross-sectional view showing an example of the configuration of a substrate processing system incorporating a supercritical drying apparatus. [Figure 3A-3G] This diagram illustrates an example of a vacuum cleaning procedure performed in a substrate processing system incorporating multiple supercritical drying devices. [Figure 4] This is a diagram showing the main piping system, illustrating an example configuration in which the vacuum line is directly connected to the processing container. [Modes for carrying out the invention]
[0008] A supercritical processing apparatus 1 according to one embodiment of the present disclosure will be described with reference to the accompanying drawings. This supercritical processing apparatus can be used to perform a supercritical drying treatment in which a substrate on which a liquid (e.g., IPA) is attached to the surface is dried using a processing fluid in a supercritical state.
[0009] As shown in Figure 1, the supercritical processing apparatus 1 includes a supercritical processing unit 10 in which supercritical drying is performed internally. The supercritical processing unit 10 has a processing container 12 and a substrate holding tray 14 (hereinafter simply referred to as "tray 14") that holds the substrate within the processing container 12.
[0010] In one embodiment, the tray 14 has a lid portion 16 that closes an opening provided in the side wall of the processing container 12, and a horizontally extending substrate support plate (substrate holding portion) 18 (hereinafter simply referred to as "plate 18") connected to the lid portion 16. A substrate W is placed horizontally on the plate 18 with its surface (device forming surface) facing upward.
[0011] The tray 14 can move horizontally between a processing position (closed position) and a substrate transfer position (open position) by a tray movement mechanism (not shown). In the processing position, the plate 18 is located within the internal space of the processing container 12, and the lid 16 closes the opening in the side wall of the processing container 12 (as shown in Figure 1). In the substrate transfer position, the plate 18 is outside the processing container 12, and it is possible to transfer the substrate W between the plate 18 and a substrate transport arm (not shown). The direction of movement of the tray 14 is, for example, the left-right direction in Figure 1.
[0012] When the tray 14 is in the processing position, the plate 18 divides the internal space of the processing container 12 into an upper space 12A above the plate 18 where the substrate W is located 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 peripheral edge of the tray 14 in the processing position and the inner wall surface of the processing container 12, which serves as a passage connecting the upper space 12A and the lower space 12B. Furthermore, a through hole connecting the upper space 12A and the lower space 12B may be provided in the plate 18 near the lid 16.
[0013] As described above, if the internal space of the processing container 12 is divided into an upper space 12A and a lower space 12B, and a connecting passage is provided between the upper space 12A and the lower space 12B, then the tray 14 (plate 18) may be configured as a substrate mounting base (substrate holding part) fixed immovably inside the processing container 12. In this case, with the lid (not shown) provided on the processing container 12 open, a substrate transport arm (not shown) enters the container body, and the substrate is transferred between the substrate mounting base and the substrate transport arm.
[0014] The processing container 12 has a first fluid supply unit 21 and a second fluid supply unit 22 for receiving a pressurized processing fluid, in this embodiment, carbon dioxide in a supercritical state (hereinafter also referred to as "CO2" for simplicity) into the internal space of the processing container 12.
[0015] The first fluid supply unit 21 is located 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 formed by a through hole formed in the bottom wall of the processing container 12. The first fluid supply unit 21 may also be a nozzle body attached to the bottom wall of the processing container 12.
[0016] The second fluid supply unit 22 is positioned to the side of the substrate W, which is 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 container 12 or in its vicinity. The second fluid supply unit 22 supplies CO2 into the upper space 12A towards a region slightly above the substrate W.
[0017] The second fluid supply unit 22 can be configured with a plurality of discharge ports arranged horizontally (for example, vertically in the plane of the paper in Figure 1). More specifically, the second fluid supply unit 22 can be formed as a header consisting of a horizontally extending pipe-shaped member with a plurality of holes. Preferably, the second fluid supply unit 22 is configured to allow CO2 to flow along the upper surface (surface) of the substrate W, substantially evenly across the upper region of the substrate W, over the entire diameter of the substrate W.
[0018] The processing container 12 further includes a fluid discharge section 24 for discharging the processing fluid from the internal space of the processing container 12. The fluid discharge section 24 can be formed as a header consisting of a horizontally extending pipe-shaped member with multiple holes, similar to the second fluid supply section 22. The fluid discharge section 24 can be provided, for example, on the side wall (second side wall) opposite to the first side wall of the processing container 12 where the second fluid supply section 22 is provided, or in its vicinity.
[0019] The fluid discharge section 24 can be positioned at any location such that the CO2 supplied into the processing container 12 from the second fluid supply section 22 passes through the area above the substrate W on the plate 18 before being discharged from the fluid discharge section 24. That is, for example, the fluid discharge section 24 may be provided at the bottom of the processing container 12 near the second side wall. In this case, the CO2 flows through the area above the substrate W in the upper space 12A, then flows into the lower space 12B through a connecting passage (or a through hole formed in the plate 18) provided on the periphery of the plate 18, and is then discharged from the fluid discharge section 24.
[0020] Next, in the supercritical treatment apparatus, a supply / discharge system for supplying and discharging CO2 to and from the treatment vessel 12 will be described. In the piping system diagram shown in FIG. 1, the member indicated by T enclosed in a circle is a temperature sensor, and the member indicated by P enclosed in a circle is a pressure sensor. The member marked with OLF is an orifice (fixed throttle), which reduces the pressure of the CO2 flowing in the downstream piping to a desired value. The member indicated by SV enclosed in a square is a safety valve (relief valve), which prevents components of the supercritical treatment apparatus such as piping or the treatment vessel 12 from being damaged by an unexpected excessive pressure. The member marked with F is a filter, which removes contaminants such as particles contained in the CO2. The member marked with CV is a check valve (non-return valve). The member indicated by FV enclosed in a circle is a flowmeter. The member indicated by H enclosed in a square is a heater for temperature control of CO2. The members marked with reference numerals VN (N is a natural number) are on-off valves, and ten on-off valves V1 to V11 are depicted in FIG. 1.
[0021] The supercritical treatment apparatus 1 has a supercritical fluid supply device (treatment fluid supply section) 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 pressurizing pump, a heater, etc. The supercritical fluid supply device 30 has the ability to send out supercritical CO2 at a pressure equal to or higher than a supercritical state guarantee pressure (specifically, about 16 MPa) described later.
[0022] A main supply line 32 is connected to the supercritical fluid supply device 30. CO2 flows out from the supercritical fluid supply device 30 into the main supply line 32 in a supercritical state, but it can also become a gaseous state due to subsequent expansion or temperature change. In this specification, a member called a "line" can be constituted by a pipe (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 the first fluid supply portion 21 of the processing vessel 12. The second supply line 36 is connected to the second fluid supply portion 22 of the processing vessel 12.
[0024] A discharge line 38 is connected to the fluid discharge portion 24 of the processing vessel 12. A pressure regulating valve (back pressure valve) 40 is provided in the discharge line 38. By adjusting the opening degree of the pressure regulating valve 40, the primary side pressure of the pressure regulating valve 40 can be adjusted, and thus the pressure inside the processing vessel 12 can be adjusted.
[0025] Based on the deviation between the measured value (PV) and the set value (SV) of the pressure inside the processing vessel 12, the control unit 300 schematically shown in FIG. 1 feedback-controls the opening degree (specifically, the position of the valve body) of the pressure regulating valve 40 so that the pressure inside the processing vessel 12 is maintained at the set value. As the measured value of the pressure inside the processing vessel 12, for example, as shown in FIG. 1, the detection value of the pressure sensor with the reference sign PS provided between the on-off valve V3 of the discharge line 38 and the processing vessel 12 can be used. That is, the pressure inside the processing vessel 12 may be directly measured by a pressure sensor provided inside the processing vessel 12, or may be indirectly measured by a pressure sensor (PS) provided outside the processing vessel 12 (discharge line 38).
[0026] The control unit 300 is, for example, a computer and comprises an arithmetic unit 301 and a storage unit 302. The storage unit 302 stores programs that control various processes performed in the supercritical processing apparatus (or a substrate processing system including the supercritical processing apparatus). The arithmetic unit 301 controls the operation of the supercritical processing apparatus by reading and executing the programs stored in the storage unit 302. The programs may have been recorded on a storage medium readable by the computer and installed from that storage medium to the storage unit 302 of the control unit 300. Examples of storage mediums readable by the computer include hard disks (HDs), flexible disks (FDs), compact disks (CDs), magnetic optical disks (MOs), and memory cards.
[0027] At a branching point 42 set on the first supply line 34, a bypass line 44 branches off from 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] Upstream of the pressure regulating valve 40, at a branching point 48 set in the discharge line 38, the vacuum line 50 branches off from the discharge line 38. The downstream end of the vacuum line 50 is open to the discharge destination (normal operation discharge destination) of the supercritical treatment apparatus 1 during normal operation, for example, to the atmosphere outside the supercritical treatment apparatus, or connected to a factory exhaust duct.
[0029] At branching point 52 set in the discharge line 38, two vacuum lines 54 and 56 branch off from the discharge line 38. The downstream ends of the vacuum lines 54 and 56 rejoin the discharge line 38. The downstream end of the discharge line 38 can be connected to, for example, a factory exhaust duct (EXH). Alternatively, the downstream end of the discharge line 38 may be connected to the factory exhaust duct (EXH) via a fluid recovery device (not shown). Useful components (e.g., IPA (isopropyl alcohol)) contained in the CO2 recovered by the fluid recovery device are separated and reused as appropriate.
[0030] A purge gas supply line 62 is connected to a confluence point 60 set in the first supply line 34 between the branching point 42 and the processing container 12. Purge gas (e.g., nitrogen (N2) gas) can be supplied to the processing container 12 from a purge gas supply source 63 via the purge gas supply line 62. The purge gas supply source 63 may be provided as factory power for a semiconductor equipment manufacturing plant.
[0031] The exhaust line 66 branches off from branch point 64, which is set on the main supply line 32, just upstream of branch point 33.
[0032] At branching point 70 set in the discharge line 38, the vacuum line 71 branches off from the discharge line 38. At branching point 72 set in the vacuum line 71, the vacuum line 71 branches into a first sub-vacuum line 73 and a second sub-vacuum line 74. A first vacuum pump 75, which serves as the first exhaust device, is installed in the first sub-vacuum line 73. A second vacuum pump 76, which serves as the second exhaust device, is installed in the second sub-vacuum line 74.
[0033] The first vacuum pump 75 has a roughing function that reduces the pressure in the space to be depressurized (in this case, the internal space of the processing container 12) from atmospheric pressure to a pressure at which the second vacuum pump can operate. The second vacuum pump 76 has the function of reducing the pressure in the space to be depressurized to a desired processing pressure (vacuum cleaning pressure) after the pressure in the space to be depressurized has been reduced by the first vacuum pump 75. The first vacuum pump 75 is, for example, a rotary pump (RP), and the second vacuum pump 76 is, for example, a turbomolecular pump (TMP).
[0034] A first switching device 79 is provided to selectively connect the portion of the discharge line 38 upstream of the branching point 70 (towards the processing container 12) to either the portion of the discharge line 38 downstream of the branching point 70 (which corresponds to "downstream discharge line 38D" in Figures 3A to 3G) or the vacuum line 71. This first switching device 79 may be a three-way valve installed at the branching point 70. The first switching device 79 may be a combination of an on-off valve installed on the discharge line 38 near the branching point 70 and downstream of the branching point 70, and an on-off valve installed on the vacuum line 71 near the branching point 70. At least one of the existing on-off valves (e.g., V5 to V8) may be repurposed to realize the function of the first switching device 79. For the sake of simplicity in the drawings, the first switching device 79 is schematically represented by a box surrounding the branching point 70.
[0035] A second switching device 80 is provided to selectively connect the vacuum line 71 to either the first sub-vacuum line 73 or the second sub-vacuum line 74. The second switching device 80, like the first switching device 79, may be a single three-way valve, or it may be a combination of multiple on-off valves provided in the vicinity of the branching point 70 on the first sub-vacuum line 73 and the second sub-vacuum line 74, respectively. The second switching device 80 is also schematically represented by a box surrounding the branching point 72.
[0036] Next, we will briefly explain the substrate drying method performed using the supercritical fluid processing apparatus described above. Note that the substrate drying method described below is publicly known, and therefore only a brief explanation will be provided. For further details, please refer to, for example, the prior application of the applicant in this case: Japanese Patent Publication No. 2022-069237.
[0037] First, a substrate W with an IPA paddle (a liquid film of IPA) formed on its surface is placed on a tray 14 that has been pulled out of the processing container 12, and then the tray 14 is placed back into the processing container 12.
[0038] [Pressure Boosting Process] First, a pressurization process is performed. CO2 (carbon dioxide), which is the processing fluid, is supplied from the supercritical fluid supply device 30 to the processing container 12 via the main supply line 32, the first supply line 34, and the first fluid supply unit 21. For a while after the start of supply, the pressure inside the processing container 12 is low, so the CO2 flows into the processing container 12 in gaseous form and at a high flow rate. The incoming CO2 gas collides with the plate 18 and then spreads throughout the processing container 12. By continuing this state for a while, the pressure inside the processing container 12 increases. In the initial stages of this pressurization process, the flow rate of CO2 flowing into the processing container 12 can be suppressed by diverting a portion of the CO2 flowing in the main supply line 32 to the exhaust line 66, or by diverting a portion of the CO2 flowing in the first supply line 34 to the discharge line 38 via the bypass line 44.
[0039] When the pressure inside the processing container 12 exceeds the critical pressure of CO2 (approximately 8 MPa), the CO2 present inside the processing container 12 (CO2 not mixed with IPA) becomes supercritical. When the CO2 inside the processing container 12 becomes supercritical, the IPA on the substrate W begins to dissolve into the supercritical CO2. After the pressure inside the processing container 12 exceeds the critical pressure of CO2, the above pressurization process is continued until a pressure is reached that guarantees the CO2 inside the processing container 12 will remain in a supercritical state (supercritical state guarantee pressure), 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.
[0040] [Distribution process] When the pressure inside the processing vessel 12 reaches the supercritical state guarantee pressure, the supply of CO2 from the first fluid supply unit 21 to the processing vessel 12 is stopped, and instead, the supply of CO2 from the second fluid supply unit 22 to the processing vessel 12 is started. By feedback control of the opening degree of the pressure regulating valve 40, the pressure inside the processing vessel 12 is maintained at a predetermined pressure slightly higher than the supercritical state guarantee pressure.
[0041] Supercritical CO2 supplied from the second fluid supply unit 22 into the processing container 12 flows over the upper region of the substrate and is then discharged from the fluid discharge unit 24. At this time, a laminar flow of supercritical CO2 is formed inside the processing container 12, flowing approximately parallel to the surface of the substrate W. The IPA in the mixed fluid (IPA + CO2) on the surface of the substrate W, exposed to the laminar flow of supercritical CO2, is replaced by supercritical CO2. Ultimately, almost all of the IPA on the surface of the substrate W is replaced by supercritical CO2.
[0042] Once the replacement of IPA with supercritical CO2 is complete, the supply of CO2 to the processing container 12 is stopped, and the pressure in the processing container 12 is reduced to atmospheric pressure by connecting the discharge line 38 to the atmosphere. As a result, the supercritical CO2 that was in the pattern of the substrate W turns into a gas and separates from the pattern, and the gaseous CO2 is discharged from the processing container 12. With this, the drying of the substrate W is completed. The dried substrate W is then removed from the processing container 12.
[0043] When the supercritical drying process described above is repeated, contaminants adhere to the surface of the components facing the atmosphere of the processing container 12 (for example, the inner wall surface of the processing container 12, the surface of the tray 14, etc., in areas where the flow velocity of the processing fluid is slow). Examples of contaminants include those derived from organic matter (e.g., higher fatty acids) dissolved in the IPA paddle on the surface of the substrate W, those derived from moisture flowing into the processing container 12 when the tray 14 is opened and closed, and those derived from substances adhering to the substrate W (for example, chemical components that adhered to the back surface of the substrate W during the liquid treatment, which is a pretreatment for the supercritical drying process). Such contaminants may detach from the surface of the components during the supercritical drying process and contaminate the substrate W. Below, a vacuum cleaning process to clean the inside of the processing container 12 in order to prevent contamination of the substrate W will be described.
[0044] With no substrate W contained in the processing container 12, the tray 14 is positioned in the processing position, i.e., the closed position, and the inside of the processing container 12 is sealed. In this state, at least the on / off valves V1, V2, V4, and V11 are closed, so that no fluid flows into the processing container 12. In addition, the first switching device 79 connects the processing container 12 to the vacuum line 71, and the second switching device 80 connects the vacuum line 71 to the first sub-vacuum line 73.
[0045] In this state, the first vacuum pump 75 (i.e., rotary pump RP) is driven, thereby evacuating the inside of the processing container 12 to a first pressure (e.g., a medium vacuum of about 1 Pa). Next, the second switching device 80 connects the vacuum line 71 and the second sub-vacuum line 74, and the second vacuum pump 76 (i.e., turbomolecular pump TMP) is driven. As a result, the inside of the processing container 12 is reduced to a second pressure lower than the first pressure (e.g., 1 × 10⁻⁶). -5 The vacuum is drawn down to a high vacuum of approximately Pa.
[0046] As a result, the aforementioned contaminants evaporate (vaporize) and detach from the surface to which they were attached. Since the inside of the processing container 12 is sucked by the second vacuum pump 76, the contaminants are discharged from the processing container 12 through the discharge line 38, the vacuum line 71, and the second sub-vacuum line 74. By continuing this state for a predetermined time, the surface to which the contaminants were attached is cleaned.
[0047] Furthermore, even while the processing container 12 is being evacuated by the first vacuum pump 75, easily evaporable contaminants detach from the surface to which they were attached and are discharged from the processing container 12. While the processing container 12 is being evacuated by the second vacuum pump 76, substances that do not evaporate at the vacuum level achieved by the first vacuum pump 75 are removed.
[0048] The processing container 12 is equipped with a heater H (schematically shown in Figure 1). The heater H is either embedded in the wall of the processing container or attached to the surface of the wall. This heater H is used for temperature control to maintain the CO2 in a supercritical state during the supercritical drying process. By operating this heater H, evaporation can be promoted, and the efficiency of contaminant removal can be increased. In this case, a vacuum bake cleaning process is performed.
[0049] The processing pressure and temperature (pressure and temperature inside the processing container 12) during the vacuum cleaning process (vacuum bake cleaning process) can be determined by referring to the vapor pressure diagram of the contaminant to be removed (for example, the vapor pressure diagram of COX). The processing pressure and temperature should be such that the most difficult-to-remove substance among the adhering substances (contaminants) that can be removed by the vacuum cleaning process (vacuum bake cleaning process) is reliably removed within the desired processing time. For example, 100°C, 1 × 10⁻⁶ -5Processing conditions such as Pa are given as examples, and under these conditions, most of the problematic adhering substances can be removed in the processing container 12 of the supercritical drying apparatus. The higher the temperature and lower the pressure, further away from the vapor pressure diagram of the contaminants to be removed, the shorter the cleaning time can be. However, since high temperature and low pressure increase the energy cost of the vacuum cleaning process (vacuum bake cleaning process), an appropriate vacuum cleaning process should be determined according to the required vacuum cleaning time. Note that the vacuum cleaning process (vacuum bake cleaning process) can be performed immediately after the supercritical drying process of the substrate W is completed and the substrate W is removed, and in this case, the temperature of the processing container 12 is sufficiently high due to residual heat even without operating the heater H. For this reason, it may be possible to perform the process at a higher pressure (lower vacuum).
[0050] Once the vacuum cleaning process (or vacuum bake cleaning process) is complete, the supercritical fluid processing apparatus is returned to the standby state for normal processing. That is, the vacuum of the processing vessel 12 is stopped and the pressure inside the processing vessel 12 is returned to atmospheric pressure. An example of this procedure is described below. First, the first vacuum pump 75 and the second vacuum pump 76 are stopped, and the first switching device 79 disconnects the part of the discharge line 38 upstream of the branching point 70 from the vacuum line 71, and connects the part upstream of the branching point 70 to the part downstream. The on-off valves V1, V2, V3, V4, V9, V10, and V11 are kept closed. The state of the on-off valves V5, V6, V7, and V8 is arbitrary. From this state, in order to return the pressure inside the processing vessel 12 to atmospheric pressure, the on-off valve V11 is opened and nitrogen gas as purge gas is supplied from the purge gas supply source 63 into the processing vessel 12 via the purge gas supply line 62, the first supply line 34, and the first fluid supply unit 21.
[0051] Preferably, the nitrogen gas supplied from the purge gas supply source 63 as a factory power source is purified in an inert gas purification device (purification device) before being supplied to the purge gas supply line 62. This prevents the processing container 12 from being contaminated by impurities contained in the purge gas after the vacuum cleaning treatment described later.
[0052] When the pressure inside the processing container 12, as detected by the pressure sensor PS located in the discharge line 38 near the processing container 12, reaches atmospheric pressure, the on-off valve V11 may be closed to stop the supply of nitrogen gas as a purge gas. Alternatively, the on-off valve V3 may be opened (in this case, for example, the on-off valve V8 is opened) while continuing to supply nitrogen gas, allowing the nitrogen gas to pass through the processing container 12. If the tray 14 is moved to the open position immediately after the pressure inside the processing container 12 reaches atmospheric pressure to load the substrate W into the processing container 12, the supply of nitrogen gas may be continued without opening the on-off valve V3. By doing so, the nitrogen gas that has flowed into the processing container 12 will flow out from the opening for loading and unloading the substrate in the processing container 12, thereby preventing moisture-containing air from flowing into the processing container 12. In this case, the supply of nitrogen gas can be stopped, for example, when the tray 14 on which the substrate W is placed moves to the closed position. The above explanation regarding the opening and closing of the on-off valve V3 will be referenced later in the explanation with reference to Figure 3E.
[0053] Furthermore, if the pressure inside the processing container 12 is lower than atmospheric pressure after the vacuum cleaning process is completed, and the inside of the processing container 12 is connected to a space with, for example, an atmospheric environment, there is a risk that air will flow into the processing container 12. In particular, if the on-off valve V3 of the discharge line 38 is opened, for example, gas (for example, air) in the discharge line 38 downstream of the on-off valve V3 may flow back into the processing container 12, and particles in the discharge line 38 may flow into the processing container 12 along with the air. To prevent such a situation, when connecting the internal space of the processing container 12 to an atmosphere with a higher pressure (for example, an atmospheric environment), it is preferable to set the pressure inside the processing container 12 to atmospheric pressure or higher.
[0054] Instead of the nitrogen gas mentioned above, CO2 supplied from the supercritical fluid supply device 30 may be used as the purge gas. In this case, instead of opening valve V11, valves V9 and V1 or V2 may be opened.
[0055] The vacuum cleaning process may be performed, for example, after the processing of one lot of substrates W is completed, or after a predetermined number of substrates W have been processed. The frequency of the vacuum cleaning process is not limited to these and can be determined as appropriate according to the processing schedule of the supercritical processing unit 10.
[0056] As shown in Figure 2, the supercritical fluid processing apparatus 1 described above can be incorporated into, for example, the substrate processing system (substrate processing apparatus) 400 shown in Figure 2. The substrate processing system 400 will be briefly described below.
[0057] The substrate processing system 400 includes an input / output station 102 and a processing station 103.
[0058] The loading / unloading station 102 includes a load port 111 and a transport block 112. Multiple carriers C are placed on the load port 111. Each carrier C accommodates multiple substrates W (e.g., semiconductor wafers) in a horizontal position with vertical spacing between them.
[0059] The transport block 112 is equipped with a transport device 113 and a transfer unit 114. The transfer unit 114 has an unprocessed substrate placement section for temporarily placing one or more unprocessed substrates W (substrates W before processing at the processing station 103) and a processed substrate placement section for temporarily placing one or more processed substrates W (substrates W that have been processed at the processing station 103). The transport device 113 can transport substrates W between any carrier C placed on the load port 111 and the transfer unit 114.
[0060] The processing station 103 comprises a transport block 104 and a pair of processing blocks 105 located on either side of the transport block 4 in the Y direction. Each processing block 105 is equipped with a liquid processing unit 200, a supercritical processing unit 10, and a processing fluid supply cabinet 119. In this embodiment, the liquid processing unit 200 and the supercritical processing unit 10 are single-wafer processing units. The processing fluid necessary for processing is supplied to the liquid processing unit 200 and the supercritical processing unit 10 from the processing fluid supply cabinet 119.
[0061] The transport block 104 comprises a transport area 115 and a transport device 116 located within the transport area 115. The transport device 116 can transport the substrate W between the transfer unit 114, any liquid processing unit 200, and any supercritical processing unit 10.
[0062] Each processing block 105 has a multilayer (e.g., three-layer) structure. In this case, each layer is provided with one liquid processing unit 200, one supercritical processing unit 10, and one processing fluid supply cabinet 119. In this case, one transport device 116 may have access to the liquid processing units 200 and supercritical processing units 10 of all layers.
[0063] The overall operation of the substrate processing system 400 is controlled by the control unit (control device) 300 (see Figure 1) described above.
[0064] Next, we will briefly explain the transport flow of the substrate W in the substrate processing system 400 described above.
[0065] An external transport robot (not shown) places a carrier C containing unprocessed substrates W onto the load port 111. A transport device 113 removes one substrate W from the carrier C and carries it into the transfer unit 114. A transport device 116 removes the substrate W from the transfer unit 114 and carries it into the liquid processing unit 200.
[0066] A liquid treatment consisting of multiple steps is performed within the liquid treatment unit 200. The liquid treatment unit 200 is a single-wafer rotary liquid treatment unit, well known, for example, in the field of semiconductor manufacturing equipment. In the liquid treatment unit 200, liquid treatment is performed on the substrate W by supplying a treatment liquid to the surface of the substrate W, which is held and rotated by a spin chuck. The liquid treatment includes, for example, a chemical treatment step, a rinsing step, an IPA replacement step, and an IPA paddle formation step. In the chemical treatment step, a chemical solution for cleaning or wet etching the surface of the substrate is supplied; in the rinsing step, for example, DIW is supplied as a rinsing solution; in the IPA replacement step, the rinsing solution is replaced with IPA; and in the IPA paddle formation step, an IPA paddle of a desired thickness is formed. As long as a liquid film of IPA (also called an IPA paddle) of a predetermined thickness is formed on the surface of the substrate W in the final step, the steps prior to that are arbitrary.
[0067] Next, the substrate W, on which IPA paddles have been formed on its surface, is removed from the liquid treatment unit 200 by the transport device 116 and transported to the supercritical treatment unit 10. In the supercritical treatment unit 10, the substrate W is dried using supercritical drying technology according to the procedure described above. After that, the transport device 116 removes the dried substrate W from the supercritical treatment unit 10 and transports it to the transfer unit 114. The transport device 13 removes this substrate W from the transfer unit 114 and places it back into the original carrier C placed on the load port 111. This completes the series of processes for one substrate.
[0068] The substrate processing system 400 includes one first vacuum pump 75 and one second vacuum pump 76, which are shared by multiple supercritical processing units 10. The first vacuum pump 75 and the second vacuum pump 76 can be housed, for example, in a pump chamber 120 between processing fluid supply cabinets 119.
[0069] Next, referring to Figures 3A to 3G, we will explain only the parts of the operation of the multiple supercritical processing units 10 and the first vacuum pump 75 and second vacuum pump 76 that are involved in vacuuming the processing vessel 12 of each supercritical processing unit 10. Figures 3A to 3G schematically show the main parts of the downstream piping configuration of the processing vessel 12 (SCC1 to SCC3) of the supercritical processing unit 10. Also, in Figures 3A to 3G, for the sake of simplifying the drawings, it is shown as if one first vacuum pump 75 and one second vacuum pump 76 are shared by three supercritical processing units 10 (processing vessel 12), but the basic operation is the same even if the number of supercritical processing units 10 increases.
[0070] As shown in Figure 3A, the discharge line 38 connected to the processing container 12 of each supercritical processing unit 10, the vacuum line 71 branching from there, and the first sub-vacuum line 73 and second sub-vacuum line 74 branching from there are provided in the same manner as shown in Figure 1. In the embodiment shown in Figure 3A, multiple first sub-vacuum lines 73 merge to form a first combined vacuum line 73M, and a first vacuum pump (RP) 75 is provided in this first combined vacuum line 73M. Also, multiple second sub-vacuum lines 74 merge to form a second combined vacuum line 74M, and a second vacuum pump (TMP) 76 is provided in this first combined vacuum line 74M. An example of operation of this configuration will be described below. For the sake of simplicity, in the following explanation, the portion of the discharge line 38 upstream of the branching point 70 (first switching device 79) will be referred to as the upstream discharge line 38U, and the portion of the discharge line 38 downstream of the branching point 70 (first switching device 79) will be referred to as the downstream discharge line 38D.
[0071] In Figures 3A to 3G, among the lines 71, 73, 74, 73M, and 74M, the parts indicated by thin solid lines represent atmospheric pressure or pressure higher than atmospheric pressure, which changes depending on the pressure inside the processing container 12; the shaded parts represent medium vacuum (pressure of about 1 Pa); and the parts indicated by thick solid lines represent high vacuum (1 × 10⁻⁶). -5This means the pressure is approximately Pa.
[0072] Figure 3A shows the case where all supercritical processing units 10 are in normal operation. In this case, the first vacuum pump 75 and one second vacuum pump 76 are operating, all vacuum lines 71 and the first sub-vacuum line 73 are at medium vacuum, and all second sub-vacuum lines 74 are at high vacuum.
[0073] Starting from the state shown in Figure 3A, the normal operation of one supercritical processing unit 10 (hereinafter also referred to as "unit SCC1") is stopped, and the supercritical processing unit 10 is subjected to vacuum cleaning. First, the substrate W is removed from the processing container 12 of unit SCC1, and then the tray 14 is moved to the closed position to seal the processing container 12.
[0074] Next, the first switching device 79 corresponding to unit SCC1 is switched to connect the processing container 12 of unit SCC1 to the first vacuum pump (RP) 75. As a result, the processing container 12 and the upstream discharge line 38U associated with unit SCC1 are reduced to a medium vacuum (see Figure 3B). Immediately before the switching of the first switching device 79, the three vacuum lines 71, the three first sub-vacuum lines 73, and the first merging vacuum line 73M are in a medium vacuum state. In other words, a space with a certain volume is already in a medium vacuum state. Therefore, compared to the case where this is not the case, the time required to reduce the processing container 12 and the upstream discharge line 38U associated with unit SCC1 to a medium vacuum can be shortened.
[0075] Next, from the state shown in Figure 3B, the second switching device 80 corresponding to unit SCC1 is switched to connect the processing container 12 of unit SCC1 to the second vacuum pump (TMP) 76. As a result, the processing container 12, the upstream discharge line 38U, and the vacuum line 71 associated with unit SCC1 are reduced to a high vacuum (see Figure 3C). Immediately before the switching of the second switching device 80, the three second sub-vacuum lines 74 and the second merging vacuum line 74M are in a high vacuum state. In other words, a space with a certain volume is already in a high vacuum. Therefore, compared to the case where this is not the case, the time required to reduce the processing container 12, the upstream discharge line 38U, and the vacuum line 71 associated with unit SCC1 to a high vacuum can be shortened.
[0076] By maintaining the state shown in Figure 3C for a predetermined time, the inside of the processing container 12 of unit SCC1 is cleaned according to the principle described above. At this time, as explained above, the cleaning efficiency can be improved by heating the processing container 12 with a heater attached to the processing container 12. Generally, the processing container 12 of the supercritical processing unit 10 is made of a relatively large metal block and is kept at a relatively high temperature during normal operation in order to maintain the supercritical state of the processing fluid. Therefore, unless the operation of the supercritical processing unit 10 is stopped for a relatively long period of time, the temperature of the processing container 12 will not drop significantly. Consequently, it is not always necessary to operate the heater attached to the processing container 12 during the vacuum cleaning process.
[0077] Once the cleaning of the inside of the processing container 12 of unit SCC1 is complete, it is acceptable to leave it in the state shown in Figure 3C until the next scheduled time for processing of the substrate W in unit SCC1. Maintaining a vacuum inside the processing container 12 of unit SCC1 ensures that the inside of the processing container 12 remains clean.
[0078] Next, when the time for processing substrate W in unit SCC1 arrives, the second switching device 80 corresponding to unit SCC1 is switched as shown in Figure 3D to connect the first vacuum pump (RP) 75 to the vacuum line 71. Then, although not shown in Figure 3D, the on-off valve V3 of the discharge line 38 (38U) is closed as explained earlier with reference to Figure 1. Next, nitrogen gas, for example, is supplied as a purge gas into the processing container 12 to return the processing container 12 to atmospheric pressure, and the first switching device 79 corresponding to SCC1 is switched to connect the processing container 12 of unit SCC1 to the downstream discharge line 38D. After that, the on-off valve V3 of the discharge line 38 (38U) can be opened at an appropriate time. If the on-off valve V3 is opened immediately after returning the processing container 12 to atmospheric pressure, the state shown in Figure 3E will be obtained. For the opening and closing of the on-off valve V3 at this time, please refer to the explanation given earlier with reference to Figure 1.
[0079] The above explanation described the case where only one of the multiple supercritical processing units 10 (SCC1) is vacuum cleaned. However, the same procedure can be used when vacuum cleaning multiple supercritical processing units 10. In other words, starting from the state shown in Figure 3A, the two supercritical processing units 10 (SCC2 and SCC3) can be vacuum cleaned by sequentially changing the first switching device 79 and the second switching device 80 to the states shown in Figures 3F and 3G.
[0080] In the above embodiment, a vacuum line 71 branched from the discharge line 38 used during normal supercritical drying was used to evacuate the processing container 12 of the supercritical processing unit 10, but the embodiment is not limited to this. For example, as shown in Figure 4, a vacuum line 71 may be provided separately from the discharge line 38, and this vacuum line 71 may be directly connected to the processing container 12, and this vacuum line 71 may be branched into a first sub-vacuum line 73 and a second sub-vacuum line 74. The on-off valve V12 provided on the vacuum line 71 is kept closed during normal operation of the supercritical processing unit 10. The on-off valve V12 is opened when vacuum cleaning is performed, and closed when the vacuum cleaning is completed, after which nitrogen purging is performed to return the inside of the processing container to atmospheric pressure. When vacuum cleaning is being performed, the on-off valve V3 of the discharge line 38 (not shown in Figure 4; see Figure 1) is kept closed and opened as needed when the vacuum cleaning is completed.
[0081] It is also possible to connect the vacuum line (71) for the vacuum cleaning process to the lines for supplying the supercritical fluid to the processing vessel 12 (e.g., supply lines 34, 36, etc.). However, if done so, there is a possibility that gases originating from contaminants generated during the vacuum cleaning process may flow into lines upstream of the processing vessel 12 with respect to the fluid flow direction during the supercritical drying process. For this reason, it is preferable to connect the vacuum line (71) to lines downstream of the processing vessel 12 with respect to the fluid flow direction during the supercritical drying process (e.g., lines 38, 50, etc.).
[0082] If the processing temperature for vacuum cleaning (vacuum bake cleaning) is increased (for example, to 200°C or higher), a certain degree of cleaning effect can be expected even in a medium vacuum. In this case, for example, if the first vacuum pump 75 is a rotary pump capable of achieving a medium vacuum of about 1 Pa, it is not necessary to provide a second vacuum pump 76 to achieve a high vacuum. When performing vacuum cleaning (vacuum bake cleaning) at a high processing temperature (for example, to 200°C or higher) as described above, it is preferable to set the pressure inside the processing container 12 to a pressure of, for example, 1 Pa or less. When performing vacuum cleaning (vacuum bake cleaning) at a low processing temperature (for example, room temperature to about 100°C), the pressure inside the processing container 12 should be, for example, 1 × 10⁻⁶ -2 It is preferable to use a pressure of Pa or less.
[0083] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.
[0084] The substrate is not limited to semiconductor wafers, but may also be other types of substrates used in the manufacture of semiconductor devices, such as glass substrates or ceramic substrates. [Explanation of Symbols]
[0085] 12 Processing container 30 Processing fluid supply unit 38, 71, 73, 74 Discharge channel 75,76 Ejection mechanism 300 Control Unit
Claims
1. A processing container capable of housing a substrate, A processing fluid supply unit supplies a processing fluid in a supercritical state to the processing container in order to perform supercritical drying on the substrate, A fluid discharge unit for discharging fluid from the processing container, comprising a discharge channel connected to the processing container and an exhaust mechanism provided in the discharge channel, A heater for heating the aforementioned processing container, A control unit that controls at least the processing fluid supply unit and the fluid discharge unit, Equipped with, The control unit, when the processing container does not contain a substrate, seals the processing container and prevents fluid from flowing into it, and in this state operates the exhaust mechanism of the fluid discharge unit to create a vacuum in the processing container, thereby reducing the pressure inside the processing container to a predetermined vacuum cleaning pressure, and performing a vacuum cleaning process to vaporize contaminants inside the processing container and discharge them from the processing container. When the control unit performs supercritical drying on the substrate in the processing container, it heats the processing container to a predetermined temperature using the heater, and supplies a supercritical processing fluid to the processing container using the processing fluid supply unit. The control unit performs the vacuum cleaning process immediately after the supercritical drying process is completed and the substrate is removed from the processing container, utilizing the residual heat of the processing container that was heated during the supercritical drying process. Circuit board processing equipment.
2. The substrate processing apparatus according to claim 1, wherein the control unit heats the processing container with the heater when performing the vacuum cleaning process to promote the vaporization of contaminants in the processing container.
3. The substrate processing apparatus according to claim 1, wherein the exhaust mechanism of the fluid discharge section includes a first exhaust device and a second exhaust device, the first exhaust device has a roughing function that reduces the pressure inside the processing container from normal pressure to a pressure at which the second exhaust device can operate, and the second exhaust device has a function that reduces the pressure inside the processing container to the vacuum cleaning pressure after the pressure inside the processing container has been reduced by the first exhaust device.
4. The substrate processing apparatus according to claim 3, wherein the first exhaust device is a rotary pump and the second exhaust device is a turbomolecular pump.
5. The discharge channel has a discharge line connected to the processing container and for discharging the processing fluid from the processing container to the discharge destination during normal operation, and a vacuum line branching off from the discharge line at a first branching point, and the exhaust mechanism is in communication with the processing container via the vacuum line, The substrate processing apparatus according to claim 1, further comprising a first switching device for switching between a normal exhaust state in which the fluid flowing down the discharge line flows down to the normal operation discharge destination without flowing into the vacuum line, and a cleaning exhaust state in which the fluid flowing down the discharge line flows into the vacuum line without flowing into the normal operation discharge destination.
6. The aforementioned vacuum line branches into a first sub-vacuum line and a second sub-vacuum line at the second branching point. The exhaust mechanism includes a first exhaust device and a second exhaust device, the first exhaust device having a roughing function that reduces the pressure inside the processing container from normal pressure to an operating pressure that enables the second exhaust device to operate, and the second exhaust device having a function that reduces the pressure inside the processing container to the vacuum cleaning pressure after the pressure inside the processing container has been reduced by the first exhaust device. The first exhaust device is provided in the first sub-vacuum line, and the second exhaust device is provided in the second sub-vacuum line. The substrate processing apparatus according to claim 5, further comprising a second switching device for switching between a first state in which the fluid flowing down the vacuum line flows into the first sub-vacuum line without flowing into the second sub-vacuum line, and a second state in which the fluid flowing down the vacuum line flows into the second sub-vacuum line without flowing into the first sub-vacuum line.
7. The substrate processing apparatus includes a plurality of processing containers, and one first exhaust device and one second exhaust device shared for vacuuming the plurality of processing containers. Each of the processing containers is connected to the discharge channel, the vacuum line, the first sub-vacuum line, and the second sub-vacuum line; therefore, the substrate processing apparatus is provided with a plurality of first sub-vacuum lines and a plurality of second sub-vacuum lines. The downstream ends of the plurality of first sub-vacuum lines merge to form a first combined vacuum line, and the one first exhaust device is provided in the first combined vacuum line. The downstream ends of the plurality of second sub-vacuum lines merge to form a second combined vacuum line, and the one second exhaust device is provided in the second combined vacuum line. The substrate processing apparatus according to claim 6.
8. The control unit, During normal operation of the substrate processing apparatus, By controlling the first exhaust device, the second exhaust device, the first switching device, and the second switching device, the fluid flowing down the discharge line is maintained in a normal exhaust state, flowing down to the normal operation discharge destination without flowing into the vacuum line, and all of the first sub-vacuum lines and the first combined vacuum line are maintained at the operable pressure, and all of the second sub-vacuum lines and the second combined vacuum line are maintained at the vacuum cleaning pressure. When a vacuum cleaning process is performed in at least one of the plurality of processing containers, By controlling the first exhaust device, the second exhaust device, the first switching device, and the second switching device, The first exhaust device is connected to the processing container in which the vacuum cleaning process is performed, and the inside of the processing container is brought to the operating pressure via the discharge line, the vacuum line, and the first sub-vacuum line corresponding to the processing container. Subsequently, the second exhaust device is connected to the processing container in which the vacuum cleaning process is performed, and the inside of the processing container is subjected to the vacuum cleaning pressure via the discharge line, the vacuum line, and the first sub-vacuum line corresponding to the processing container. The substrate processing apparatus according to claim 7.
9. The system further includes a purge gas supply unit that supplies purge gas to the aforementioned processing container. The substrate processing apparatus according to claim 1, wherein the control unit supplies purge gas to the processing container from a gas supply unit, which is provided separately from the processing fluid supply unit, in order to return the pressure inside the processing container to atmospheric pressure after the completion of the vacuum cleaning process.
10. The substrate processing apparatus according to claim 9, wherein the purge gas is nitrogen gas.
11. The substrate processing apparatus according to claim 1, wherein the control unit causes the processing fluid supply unit to supply the processing fluid to the processing container in order to return the pressure inside the processing container to atmospheric pressure after the completion of the vacuum cleaning process.
12. A substrate processing apparatus comprising a processing container capable of containing a substrate, a heater for heating the processing container, and a processing fluid supply unit for supplying a supercritical processing fluid to the processing container in order to perform supercritical drying on the substrate, wherein the processing container is heated to a predetermined temperature by the heater, and a supercritical processing fluid is supplied to the processing container by the processing fluid supply unit to perform supercritical drying on the substrate within the processing container, a cleaning method for cleaning the inside of the processing container, The system includes a vacuum cleaning process, which is performed by sealing the processing container and preventing fluid from flowing into it when no substrate is contained in the processing container, and then reducing the pressure inside the processing container to a predetermined vacuum cleaning pressure by evacuating the processing container, thereby vaporizing contaminants inside the processing container and discharging them from the processing container. The vacuum cleaning process is a cleaning method in which the process is performed immediately after the supercritical drying process is completed and the substrate is removed from the processing container, utilizing the residual heat of the processing container that was heated during the supercritical drying process.
13. The vacuuming of the processing container is performed using a first exhaust device and a second exhaust device. The first exhaust device performs roughing to reduce the pressure inside the processing container from atmospheric pressure to a pressure at which the second exhaust device can operate. The cleaning method according to claim 12, wherein the second exhaust device then reduces the pressure inside the processing container to the vacuum cleaning pressure.
14. The cleaning method according to claim 12, wherein the vacuum cleaning process is performed while the processing container is heated by a heater.