JP2012243776A - Substrate processing apparatus, substrate processing method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate processing apparatus, etc. which can restrict reduction in the capability of removing a liquid by using a treatment fluid and also can remove the liquid sticking to the substrate surface.SOLUTION: In a processing vessel 1, a liquid used to prevent the surface of a substrate W from drying is put into contact with a treatment fluid at high pressure in a supercritical or a subcritical state to remove the drying purpose liquid. In this liquid removal process, a booster pump 2 supplies the treatment fluid to the processing vessel 1 via a supply line 51 and puts it into a treatment fluid atmosphere at high pressure. Next, the fluid inside the processing vessel 1 is circulated to a circulation line 53 by a circulation pump 3 which is larger in a delivery flow rate than that of the booster pump 2, and the fluid inside the processing vessel 1, thereafter, is discharged from a discharge line 52.

Description

  The present invention relates to a technique for removing a liquid attached to a surface of a substrate using a processing fluid in a supercritical state or a subcritical state.

  In the manufacturing process of a semiconductor device in which a laminated structure of an integrated circuit is formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer), which is a substrate, fine dust or a natural oxide film on the wafer surface is removed by a cleaning liquid such as a chemical liquid. A liquid processing step is provided for processing the wafer surface using a liquid.

  However, with the high integration of semiconductor devices, a phenomenon called so-called pattern collapse has become a problem when removing liquid adhering to the wafer surface in such a liquid processing step. For example, when the liquid that remains on the wafer surface is dried, the liquid that remains on the left and right of the projections and recesses that form the pattern is dried unevenly, for example, and the surface that pulls the projections to the left and right. This is a phenomenon in which the balance of tension collapses and the convex part falls down in the direction in which a large amount of liquid remains.

  As a technique for removing the liquid adhering to the wafer surface while suppressing the occurrence of such pattern collapse, a method using a processing fluid in a supercritical state or a subcritical state (hereinafter collectively referred to as a high pressure state) is known. The high-pressure fluid has a smaller viscosity than the liquid and has a high ability to extract the liquid, and there is no interface between the high-pressure fluid and the liquid or gas in an equilibrium state. Therefore, when the liquid adhering to the wafer surface is replaced with the processing fluid, and then the state of the processing fluid is changed to a gas, the liquid can be dried without being affected by the surface tension.

  The inventors have developed and commercialized a technique for removing the liquid on the wafer surface using such a processing fluid. However, even if the liquid on the wafer surface and the processing fluid are brought into contact with each other, the liquid in the processing fluid It has been found that when the concentration becomes saturated, the ability to remove the liquid decreases.

  Here, Patent Document 1 describes a method of drying a substrate by substituting liquid carbon dioxide for a rinsing liquid adhering to a pattern formed on a substrate and evaporating the carbon dioxide after making it supercritical. ing. In this method, while maintaining the carbon dioxide in a liquid state, the pressure in the reaction chamber in which the substrate is disposed is changed, and the carbon dioxide in the reaction chamber is stirred to promote the replacement of the rinse liquid with carbon dioxide. However, in general, a pump with a high discharge pressure has a small flow rate (for example, the discharge flow rate of the pressure pump in Patent Document 1 is about 100 milliliters / minute), and sufficient replacement of the rinsing liquid with carbon dioxide is possible even if pressure fluctuations are used. There is a high possibility that it cannot be shortened.

JP 2004-1558591 A: Claim 1, paragraphs 0030 to 0036, FIG.

  The present invention has been made under such a background, and a substrate processing apparatus, a substrate processing method, and this method capable of removing a liquid adhering to the surface of a substrate with a processing fluid in a relatively short time. An object of the present invention is to provide a storage medium that stores information.

The substrate processing apparatus according to the present invention performs a process of removing the drying preventing liquid by bringing a processing fluid in a supercritical state or a subcritical state into contact with the drying preventing liquid on the substrate surface. A processing container,
A booster pump provided in a supply line for supplying a processing fluid to the processing container, and a processing fluid atmosphere in a high-pressure state in the processing container;
A circulation line for circulating the fluid in the processing vessel;
A circulation pump provided in the circulation line and having a larger discharge flow rate than the booster pump;
A pressure reducing valve for reducing the pressure in the processing container is provided, and a discharge line for discharging the fluid in the processing container;
Control in which the inside of the processing container is set to a high-pressure processing fluid atmosphere, and then the control signal is output so that the fluid in the processing container is discharged from the discharge line after the fluid in the processing container is circulated through the circulation line. And a section.

The substrate processing apparatus may have the following features.
(A) An opening / closing valve is provided in the circulation line, and the control unit circulates the fluid in the processing container to the circulation line, then closes the opening / closing valve, and then supplies the processing fluid from the supply line. The fluid is withdrawn from the discharge line while maintaining the high pressure processing fluid atmosphere in the processing vessel, and then the supply of the processing fluid from the supply line is stopped and the fluid in the processing vessel is discharged from the discharge line. To output a control signal.
(B) The circulation pump is a centrifugal pump, an axial pump or a turbine pump.
(C) The circulation pump includes an impeller that rotates around a rotation shaft to send out a fluid, and a rotation drive unit that rotates the rotation shaft.
(D) The circulation pump is provided in the rotation drive unit, and includes a ball bearing that holds the rotation shaft, a bearing casing that houses the rotation shaft and the ball bearing, and communicates with a pump casing that houses the impeller. The bearing casing is connected to an extraction line for extracting a part of the fluid flowing from the pump casing into the bearing casing.
(E) A branch line branched from the supply line is connected to the circulation pump, and fluid is extracted from the extraction line while supplying a processing fluid from the branch line to the circulation pump.
(F) The fluid is extracted from the extraction line while supplying the processing fluid from the supply line to the processing container.
(G) The booster pump is a syringe pump or a diaphragm pump.
(H) A heating unit for heating the fluid discharged from the processing container to a temperature equal to or higher than the boiling point of the drying preventing liquid.
(I) A density meter that measures the density of the fluid in the processing container or the circulation line is provided, and the control unit is configured such that the density of the fluid is replaced with the processing fluid in the drying prevention liquid in the processing container. After the density reaches a predetermined density, the fluid in the processing container is discharged from the discharge line.

  Since the present invention circulates the fluid in the processing container using a circulation pump having a larger discharge flow rate than the booster pump that supplies the processing fluid to the processing container, the flow of the fluid in the processing container is disturbed and the processing fluid And the liquid on the substrate surface can be promoted. As a result, the processing fluid is agitated and the liquid extracted into the processing fluid is less likely to be saturated, and the liquid on the substrate surface can be removed in a relatively short time.

It is explanatory drawing which shows the structure of the wafer processing apparatus concerning embodiment. It is an external appearance perspective view of the processing container provided in the said wafer processing apparatus. It is a flowchart which shows the flow of operation | movement of the said wafer processing apparatus. It is a 1st operation explanatory view of the wafer processing device. It is 2nd operation | movement explanatory drawing of the said wafer processing apparatus. It is a 3rd operation explanatory view of the wafer processing device. It is a flowchart which shows the flow of operation | movement of the wafer processing apparatus concerning other embodiment. It is operation | movement explanatory drawing of the wafer processing apparatus concerning the said other embodiment. It is explanatory drawing which shows the density change of the fluid in a processing container when operating a circulation pump.

  As an embodiment of the present invention, a configuration of a wafer processing apparatus (substrate processing apparatus) that removes a liquid for preventing drying adhered to the surface of a wafer W will be described with reference to FIG. The wafer processing apparatus includes a processing container 1 that performs a process of removing a liquid for preventing drying adhered to the surface of a wafer W using a high-pressure processing fluid, and a booster pump that supplies the processing fluid to the processing container 1 2, a circulation line 53 provided with a circulation pump 3 for extracting the fluid in the processing container 1 and returning it to the processing container 1 again, and discharging the fluid in the processing container 1. , And a discharge line 52 provided with a pressure reducing valve 521 for reducing the pressure in the processing container 1.

  As shown in FIG. 2, the processing container 1 includes a housing-like container main body 11 in which an opening 12 for loading and unloading a wafer W is formed, a holding plate 16 that holds the wafer W to be processed horizontally, A lid member 15 that supports the holding plate 16 and seals the opening 12 when the wafer W is loaded into the container body 11 is provided.

The container main body 11 is a container in which a processing space of about 200 to 10000 cm ³ capable of accommodating a wafer W having a diameter of 300 mm, for example, is formed, and the supply line 51 and the circulation line 53 on the resupply side ( A supply port 13 connected to the discharge side of the circulation pump 3 and a discharge port 14 connected to the discharge line 52 and the extraction side of the circulation line 53 (the suction side of the circulation pump 3). In addition, the processing container 1 is pressed against the internal pressure received from the high-pressure processing fluid supplied into the processing space, and the lid member 15 is pressed against the container body 11 to seal the processing space (not shown). A mechanism is provided. Further, a heat insulating material, a tape heater, or the like may be provided on the surface of the container body 11 so that the processing fluid supplied into the processing space can maintain a temperature in a supercritical state or a subcritical state.

  A supply line 51 connected to the supply port 13 of the processing container 1 (container body 11) is connected to the processing fluid supply unit 4 via an on-off valve 511, a filter 512, and a booster pump 2, as shown in FIG. It is connected. The on-off valve 511 opens and closes when the processing fluid is supplied to and stopped from the processing container 1, and the filter 512 removes particles contained in the processing fluid supplied to the processing container 1.

  When the processing fluid supplied from the processing fluid supply unit 4 is a gas, the booster pump 2 boosts the processing fluid to a pressure at which a high pressure state (supercritical state or subcritical state) is reached. Further, when a high-pressure processing fluid is supplied from the processing fluid supply unit 4, the processing fluid can be sent out so that the high-pressure state is maintained in the processing container 1. As the booster pump 2 having such a capability, a syringe pump or a diaphragm pump having a high discharge pressure is generally employed, and the discharge flow rate is, for example, 0.1 L in the range of 0.01 to 1 L / min. The discharge flow rate is smaller than that of the circulation pump 3 described later.

A processing fluid for removing the liquid is supplied from the processing fluid supply unit 4 in contact with the liquid on the surface of the wafer W. The processing fluid supply unit 4 of the present example is, for example, carbon dioxide (CO ₂ : critical temperature 31 ° C., critical pressure 7.4 MPa (absolute pressure)) in a high-pressure gas state or a high-pressure state (supercritical state or subcritical state). It is configured as a cylinder or tank for storage. When CO ₂ supplied from the processing fluid supply unit 4 is a high-pressure gas, the pressure and temperature are increased by the adiabatic compression of the CO _{2 by the} booster pump 2, resulting in a high-pressure state. It is supplied to the processing container 1. Further, when CO ₂ is in a high pressure state, the processing fluid is supplied to the processing container 1 so that this pressure is maintained in the processing container 1.

  On the other hand, the discharge line 52 connected to the discharge port 14 of the processing container 1 (container body 11) is connected to a processing fluid recovery unit (not shown), and the fluid in the processing container 1 (from the processing fluid and the surface of the wafer W). The removed liquid) is discharged. The discharge line 52 is provided with a pressure reducing valve 521. The pressure reducing valve 521 depressurizes the pressure of the processing container 1, and for example, opens the opening based on a detected value of a pressure gauge (not shown) provided in the processing container 1. By adjusting the pressure, the pressure in the processing container 1 can be maintained at a high pressure (a critical pressure of the processing fluid or a subcritical pressure).

  In the wafer processing apparatus having the above-described configuration, the booster pump 2 provided in the supply line 51 has a relatively small discharge flow rate of about 0.01 to 1 L / min as described above. Therefore, even if the processing fluid is continuously supplied from the supply line 51 to the processing container 1 while discharging the fluid in the processing container 1 from the discharge line 52, the processing fluid is, for example, on the surface of the wafer W having a diameter of about 300 mm. The flow is likely to be in a laminar state.

  If the flow of the processing fluid is in a laminar flow state on the surface of the wafer W, the fluid hardly flows in a direction perpendicular to the surface of the wafer W, so that the processing fluid is hardly stirred and flows in the vicinity of the surface of the wafer W. Only fluids can contribute to liquid removal. As a result, if the processing fluid in the vicinity of the surface of the wafer W from which the liquid has been extracted becomes saturated, it is considered that the ability of the processing fluid to remove the liquid decreases. Therefore, in this case, only a part of the processing fluid supplied to the processing container 1 is involved in the processing for removing the liquid on the surface of the wafer W.

  Therefore, the wafer processing apparatus of the present embodiment disturbs the flow of the fluid in the processing container 1 and promotes the mixing of the fluid, thereby bringing a large amount of processing fluid into contact with the liquid on the surface of the wafer W, so that the liquid The structure which can suppress the fall of the removal capability of is provided. Hereinafter, the contents of the configuration will be described.

  As a configuration for promoting the mixing of the fluid in the processing container 1, the wafer processing apparatus of this example is provided with a circulation line 53 for extracting the fluid in the processing container 1 and returning it to the processing container 1 again. The circulation line 53 is provided with a circulation pump 3 having a larger discharge flow rate than the booster pump 2 described above. As shown in FIG. 1, the circulation line 53 of this example branches from the discharge line 52 on the extraction side, while the return side merges with the supply line 51. The circulation line 53 opens and closes in order from the extraction side. A valve 531, a circulation pump 3, a line mixer 533, and an on-off valve 532 are interposed.

  The on-off valves 531 and 532 serve to disconnect or connect the circulation line 53 to the processing container 1, and the fluid in the processing container 1 is circulated when connected, while the circulation is stopped when disconnected. The

  For example, a centrifugal pump is used as the circulation pump 3, and the centrifugal pump rotates to feed the fluid in the circulation line 53 toward the processing container 1, and a rotating shaft 32 that rotates the impeller 31. , And a rotation drive unit 36 that rotationally drives the rotation shaft 32. The impeller 31 is accommodated in the pump casing 33, and the suction port of the pump casing 33 is connected to the extraction side piping of the circulation line 53, while the discharge port of the pump casing 33 is connected to the return side piping of the circulation line 53. It is connected.

  The rotary shaft 32 is accommodated in a bearing casing 34 that communicates with the pump casing 33 through a narrow gap, and via a ball bearing 35 so as to be rotatable around the rotary shaft in the bearing casing 34. Is held. The rotation drive unit 36 can rotate the bearing casing 34 from the outside of the space in which the rotation shaft 32 is accommodated, and the rotation shaft 32 and the rotation drive unit 36 constitute a canned motor.

  The centrifugal pump that rotates the impeller 31 and sends out the fluid has a small head but a large discharge flow rate as compared with the booster pump 2 including a syringe pump and a diaphragm pump. For this reason, it is possible to circulate a large flow rate of fluid in the circulation line 53 as compared with the supply from the supply line 51, thereby disturbing the flow in the processing container 1 and promoting the mixing of the processing fluid and the liquid. can do. In this example, the discharge flow rate of the circulation pump 3 is, for example, 20 L / min in the range of 5 to 60 L / min.

  Here, since the ball bearing 35 holding the rotating shaft 32 is in direct contact with the rotating rotating shaft 32, these members may rub against each other and particles may be generated. Since the internal spaces of the bearing casing 34 and the pump casing 33 communicate with each other as described above, when a fluid containing particles flows into the pump casing 33, the particles are sent out to the processing container 1 and the wafer W There is a risk of sticking to.

Therefore, an extraction line 55 for extracting the fluid in the bearing casing 34 together with particles to the outside is connected to the bearing casing 34 of this example. Thereby, part of the fluid that has flowed into the pump casing 33 flows to the extraction line 55 through the space in the bearing casing 34, so that the flow of particles generated in the bearing casing 34 into the pump casing 33 can be suppressed. . 551 shown in FIG. 1 is a flow rate adjusting valve that adjusts the flow rate of the fluid extracted from the bearing casing 34.
Reference numeral 533 provided in the branch line 54 on the discharge side of the circulation pump 3 is a line mixer for promoting mixing of the fluid (processing fluid and liquid removed from the wafer W) flowing in the branch line 54.

  Further, the circulation pump 3 extracts a part of the processing fluid flowing from the booster pump 2 to the processing container 1 and supplies the processing fluid to the pump casing 33, so that the fluid in the bearing casing 34 including the particles flows toward the pump casing 33. A branch line 54 is connected to prevent backflow. The branch line 54 is supplied in the vicinity of the communication portion between the pump casing 33 and the bearing casing 34. In the figure, reference numeral 541 denotes a flow rate adjusting valve for adjusting the flow rate of the processing fluid flowing through the branch line 54. For example, a processing fluid of about 0.5 L / min in the range of 0.1 to 1 L / min is extracted from the supply line 51. And supplied to the circulation pump 3. As the circulation pump, a pump having a relatively low head and a large flow rate such as an axial flow pump and a turbine pump is used in addition to a centrifugal pump.

  The wafer processing apparatus having the configuration described above includes a control unit 6. The control unit 6 includes a computer including a CPU and a storage unit (not shown), and is connected to the processing container 1, the booster pump 2, the circulation pump 3, and various valves 511, 521, 531, 532, 541, and 551. The storage unit of the control unit 6 is operated by the wafer processing apparatus, that is, after the wafer W whose surface is wet with the liquid for preventing drying is carried into the processing container 1, the liquid is removed by the processing fluid, and the wafer W is removed. A program in which a group of steps (commands) for control related to the operation until extraction is assembled is recorded. This program is stored in a storage medium such as a hard disk, a compact disk, a magnetic optical disk, or a memory card, and installed in the computer therefrom.

  The operation of the wafer processing apparatus will be described below with reference to the flowchart of FIG. 3 and the operation diagrams of FIGS. When liquid processing for removing minute dust and natural oxide film on the surface of the wafer W is completed in the upstream processing liquid processing apparatus, a liquid for preventing drying such as IPA (IsoPropyl Alcohol) is supplied to the surface of the wafer W, The wafer W is transferred to the wafer transfer arm and transferred to the wafer processing apparatus (start).

  Next, the wafer W is transferred to a lifting pin (not shown) and placed on the holding plate 16 of the processing container 1, and then the wafer W is loaded into the container body 11 through the opening 12 (step S101). The container 1 is sealed (step S102). After that, as shown in FIG. 4, the on-off valve 511 of the supply line 51 is opened and the booster pump 2 is operated to supply the processing fluid to the processing container 1, so that the inside of the processing container 1 is in a high pressure state (supercritical state or The pressure is increased to a critical pressure) (step S103). In FIGS. 6 to 8, the valves 511, 521, 531, 532, 541, and 551 are denoted by “O” when they are open, and “S” when they are closed.

  When the inside of the processing vessel 1 becomes a high-pressure processing fluid atmosphere in this way, the on-off valves 531 and 532 of the circulation line 53 are opened and the circulation pump 3 is operated to circulate the fluid in the processing vessel 1 (FIG. 5). At this time, the flow regulating valve 541 of the branch line 54 is opened to supply the processing fluid before use to the pump casing 33, and the extraction fluid 55 is balanced with the processing fluid supplied from the supply line 51 and the branch line 54. Remove the amount of fluid.

  As a result, while the supply of the processing fluid from the booster pump 2 is continued, the operation of circulating the fluid in the processing container 1 by the booster pump 2 is executed (step S105). By circulating the fluid in the processing container 1 by the circulation pump 3 having a large discharge amount, the flow of the fluid in the processing container 1 can be disturbed to promote mixing of the processing fluid and the liquid for preventing drying. As a result, it is possible to prevent the processing fluid in the vicinity of the surface of the wafer W from being saturated with the drying preventing liquid, and to suppress a decrease in the ability to remove the liquid.

Further, while extracting a predetermined amount of processing fluid (mixed fluid of high-pressure CO ₂ and anti-drying liquid (IPA)) from the extraction line 55, the processing fluid (high-pressure state) is extracted from the supply line 51 and the branch line 54. Since CO ₂ ) is supplied, the concentration of IPA in the processing fluid circulating through the circulation line 53 gradually decreases as shown in the experimental results (FIG. 9) described later. As will be described later, FIG. 9 shows that the circulation pump 3 is operated while supplying high-pressure CO ₂ to the processing vessel 1 to circulate the CO ₂ through the circulation line 53 connected to the processing vessel 1. Is a result of measuring the density change of the fluid flowing through the circulation line 53 by supplying a pulse.

  As shown in FIG. 9, the density change of the fluid flowing through the circulation line 53 largely fluctuates (amplitude) at the initial stage, and then this fluctuation is reduced and gradually decreases. It is experimentally confirmed that the time when this variation is settled (denoted as point T in FIG. 9) is the time when the liquid for preventing drying on the surface of the wafer W is replaced with the processing fluid in the actual processing. doing. At this time, the operation may be performed by disconnecting the circulation line 53, depressurizing the processing container 1 to discharge the fluid, and taking out the dried wafer W. In this case, the extracted IPA is condensed in the processing fluid. As a result, the wafer W may be attached again. Therefore, it is desirable to continue the circulation until the total amount of IPA contained in the processing fluid circulating through the circulation line 53 becomes a sufficiently low value. Since the circulation pump 3 has a larger discharge flow rate than the booster pump 2 as described above, even if a time for continuing the circulation of the processing fluid after the replacement is added, the replacement and discharge of the processing fluid are performed compared with the case where the circulation is not performed. It has been confirmed that the time required for (decompression) can be shortened.

  When the preset time sufficient to remove the liquid for preventing drying on the surface of the wafer W elapses in this manner, the booster pump 2 and the circulation pump 3 are stopped, and supply and circulation of the processing fluid are stopped (step S106). Then, as shown in FIG. 6, the on-off valves 511, 531, and 532 on the supply line 51 and the circulation line 53 side are closed, while the pressure reducing valve 521 on the discharge line 52 is opened to discharge the fluid in the processing container 1 to atmospheric pressure. The pressure is reduced (step S107). As a result, the liquid extracted into the processing fluid is discharged out of the processing container 1 together with the processing fluid, the surface liquid is removed, and a dry wafer W is obtained.

At this time, for example, a heating unit such as a tape heater is provided in the processing container 1, and the temperature of the fluid flowing through the processing container 1 or the circulation line 52 (the processing fluid and the mixed fluid for preventing drying) is set to the boiling point of the drying preventing liquid ( In the case of IPA, it may be heated to 82.4 ° C. or higher. Thereby, condensation of the liquid for preventing drying at the time of discharging the processing fluid and reattachment to the wafer W can be prevented, and occurrence of pattern collapse due to reattachment can be prevented.
When the pressure in the processing container 1 drops to atmospheric pressure, the holding plate 16 is moved to carry out the wafer W (Step S108), and the wafer W is transferred to an external transfer arm to finish the processing (End).

  The wafer processing apparatus according to the present embodiment has the following effects. Since the fluid in the processing container 1 is circulated using the circulation pump 3 having a discharge flow rate larger than that of the booster pump 2 that supplies the processing fluid to the processing container 1, the flow of the fluid in the processing container 1 is disturbed for processing. Mixing of the fluid and the liquid on the surface of the wafer W can be promoted. As a result, the processing fluid is agitated and the liquid extracted into the processing fluid is less likely to be saturated, and the liquid on the surface of the wafer W can be removed in a relatively short time.

  7 and 8 show another example of the operation of the wafer processing apparatus described with reference to FIGS. 3 and 4 to 6. In this example, after the operation of flowing the fluid in the processing container 1 through the circulation line 53 to promote mixing of the processing fluid and the liquid is performed, the circulation is stopped and the circulation line 53 is separated from the processing container 1 (FIG. 7). Step S106A), and then, while continuing to supply the processing fluid from the supply line 51, the opening of the pressure reducing valve 521 is adjusted so that the inside of the processing container 1 is maintained in a high-pressure processing atmosphere. The operation of extracting the fluid (step S106B in FIG. 7, FIG. 8) is added.

  After the processing fluid in the processing container 1 and the liquid on the surface of the wafer W are sufficiently mixed, the processing fluid is not mixed so much with the processing fluid supplied from the supply line 51, and the processing container 1 is in a laminar flow state. The liquid can be efficiently extracted from the processing container 1 by pushing the liquid from the inside. Therefore, as shown in an embodiment described later, the timing at which the liquid for preventing drying on the wafer W is replaced with the processing fluid is grasped in advance, and the circulation line 53 is disconnected in accordance with this timing, and the discharge line 52 is removed. By extracting the fluid, the concentration of the liquid for preventing drying in the processing container 1 can be reduced in a relatively short time as compared with the case of extracting the fluid in the processing container 1 while circulating the circulation line 53.

  Further, when the mixed fluid in the processing container 1 is pushed out in a laminar flow state in this way, the amount of the processing fluid consumed to push out the mixed fluid can be reduced. Further, since the circulation line 53 is disconnected from the processing container 1, it is not necessary to replace the circulation line 53 or the space in the pump casing 33 of the circulation pump 3 with the processing fluid supplied from the supply line 51. The amount of processing fluid used can be reduced. However, disconnecting the circulation line 53 from the processing container 1 is not an essential condition. For example, after the circulation pump 3 is stopped, the pressure reducing valve 521 of the discharge line 52 is opened to replace the inside of the processing container 1 with the processing fluid. May be.

  Thus, when the operation of replacing the inside of the processing container 1 with the processing fluid for the preset time in the state shown in FIG. 8 is performed, the supply of the processing fluid from the supply line 51 is stopped (step S106C in FIG. 7). The operation of discharging the fluid in the processing container 1 and reducing the pressure to atmospheric pressure (step S107) and then unloading the wafer W (step S108) is the same as the flowchart of FIG.

  Here, the time for circulating the fluid in the processing container 1 to the circulation line 53 is the timing at which the processing fluid in the processing container 1 and the liquid for preventing drying are sufficiently mixed, and the fluid in the processing container 1 is supplied. The timing of replacement with a new processing fluid supplied from the line 51 may be grasped in advance by a preliminary experiment or the like. Further, for example, the density meter 534 (shown in FIG. 1) is installed in the processing container 1 or the circulation line 53, and the above timing is monitored while monitoring the density change of the fluid flowing through these regions via the control unit 6 or the like. You may know.

  Here, for example, if there is a magnetic fluid seal capable of separating the pump casing 33 of the circulation pump 3 and the bearing casing 34 even under a high-pressure atmosphere, the extraction line 55 may not be provided. The provision of the branch line 54 is not an essential requirement, and may be adopted according to the amount of particles mixed in from the bearing casing 34.

  Further, in each of the above-described embodiments, while the processing fluid is continuously supplied from the supply line 51, the fluid is circulated through the circulation line 53 or the fluid is extracted from the discharge line 52 to process the inside of the processing container 1. An example has been described in which the liquid is mixed and replaced with a fluid, and the liquid adhering to the wafer W is discharged, and then the pressure is reduced to atmospheric pressure. However, for example, if a sufficient amount of processing fluid is supplied to the processing container 1 and the processing container 1 is returned to atmospheric pressure, the liquid extracted into the processing fluid does not recondense on the surface of the wafer W. Supply of the processing fluid from the supply line 51 and continuous extraction of the fluid from the extraction line 55 and the discharge line 52 are not essential requirements.

  For example, after supplying the processing fluid from the supply line 51, the supply is stopped, and then the circulation pump 3 is operated and only the circulation by the circulation line 53 is performed. Then, the processing container 1 is depressurized to the atmospheric pressure, and the liquid is supplied. The removed wafer W may be obtained. At this time, the atmosphere in the processing container 1 may be heated to prevent recondensation of the liquid.

In addition, the processing fluid supplied to the processing container 1 is not limited to a fluid in a gas state or a high-pressure state (supercritical state or subcritical state) such as CO ₂ . For example, a liquid processing fluid such as IPA or HFE (Hydro Fluoro Ether) may be supplied. At this time, the processing container 1 may be heated when the processing fluid does not reach a high pressure state only by increasing the pressure by the boosting pump 2.
Further, the liquid for preventing drying of the surface of the wafer W is not limited to IPA, and may be HFE or water.

(Experiment)
While supplying CO ₂ at 0.5 L / min from the booster pump 2 to the wafer processing apparatus shown in FIG. 1, the circulation pump 3 is operated and the fluid in the processing container 1 is circulated to the circulation line 53 at 20 L / min. I let you. A change in the density of the fluid flowing through the circulation line 53 was measured by supplying 20 mL of IPA pulsed into the processing container 1. The volume of the processing space in the processing container 1 is 1000 cm ³ , the temperature of the processing container 1 is 58 ° C., and the pressure is 15 MPa (gauge pressure).

  The result of the experiment is shown in FIG. According to the figure, the fluid density fluctuates greatly at the beginning when the IPA is supplied, but this density fluctuation gradually attenuates and becomes a gradual density change in about one minute. Therefore, if the circulation of the fluid is stopped at this timing and switched to the discharge from the discharge line 52, the flow in the processing container 1 becomes a laminar flow, and the processing fluid mixed with IPA is pushed out, thereby discharging the fluid. It is considered that the density change of the fluid flowing through the line 52 rapidly decreases as indicated by a broken line.

W Wafer 1 Processing vessel 2 Booster pump 3 Circulating pump 31 Impeller 32 Rotating shaft 33 Pump casing 34 Bearing casing 35 Ball bearing 36 Rotation drive unit 4 Processing fluid supply unit 51 Supply line 52 Discharge line 521 Pressure reducing valve 53 Circulation line 54 Branch line 55 Extraction line 6 Control section

Claims (14)

A treatment container in which a treatment fluid in a supercritical state or a subcritical state is brought into contact with a liquid for preventing drying on the substrate surface to remove the drying preventing liquid; and
A booster pump provided in a supply line for supplying a processing fluid to the processing container, and a processing fluid atmosphere in a high-pressure state in the processing container;
A circulation line for circulating the fluid in the processing vessel;
A circulation pump provided in the circulation line and having a larger discharge flow rate than the booster pump;
A pressure reducing valve for reducing the pressure in the processing container is provided, and a discharge line for discharging the fluid in the processing container;
Control in which the inside of the processing container is set to a high-pressure processing fluid atmosphere, and then the control signal is output so that the fluid in the processing container is discharged from the discharge line after the fluid in the processing container is circulated through the circulation line. And a substrate processing apparatus. The circulation line is provided with an on-off valve,
The controller circulates the fluid in the processing container to a circulation line, then closes the on-off valve, and then supplies the processing fluid from the supply line to bring the processing container into a high-pressure processing fluid atmosphere. 2. The control signal is output so that the fluid is extracted from the discharge line while maintaining, and then the supply of the processing fluid from the supply line is stopped and the fluid in the processing container is discharged from the discharge line. 2. The substrate processing apparatus according to 1.   The substrate processing apparatus according to claim 1, wherein the circulation pump is a centrifugal pump, an axial pump, or a turbine pump.   3. The substrate processing apparatus according to claim 1, wherein the circulation pump includes an impeller that rotates around a rotation shaft to send out a fluid, and a rotation drive unit that rotates the rotation shaft. The circulation pump includes a ball bearing that is provided in the rotation drive unit and holds the rotation shaft, and a bearing casing that houses the rotation shaft and the ball bearing and communicates with a pump casing that houses the impeller. ,
The substrate processing apparatus according to claim 4, wherein an extraction line for extracting a part of the fluid that has flowed from the pump casing into the bearing casing is connected to the bearing casing.   6. A branch line branched from the supply line and connected to the circulation pump is provided, and fluid is extracted from the extraction line while supplying a processing fluid from the branch line to the circulation pump. 2. The substrate processing apparatus according to 1.   The substrate processing apparatus according to claim 5, wherein the fluid is extracted from the extraction line while supplying a processing fluid from the supply line to the processing container.   The substrate processing apparatus according to claim 1, wherein the booster pump is a syringe pump or a diaphragm pump.   9. The substrate processing according to claim 1, further comprising a heating unit that heats the fluid discharged from the processing container to a temperature equal to or higher than a boiling point of the drying preventing liquid. apparatus. A density meter for measuring the density of the fluid in the processing vessel or circulation line;
The control unit discharges the fluid in the processing container from the discharge line after the density of the fluid has reached a predetermined density indicating that the drying prevention liquid in the processing container has been replaced with the processing fluid. The substrate processing apparatus according to claim 1, wherein the substrate processing apparatus is a substrate processing apparatus. A substrate processing method for removing a liquid for preventing drying by bringing a processing fluid in a supercritical state or a subcritical state into contact with a liquid for preventing drying on a substrate surface in a processing container. ,
Supplying a processing fluid to a processing container from a supply line provided with a booster pump, and setting the inside of the processing container to a high-pressure processing fluid atmosphere;
Next, circulating the fluid in the processing container to a circulation line provided with a circulation pump having a larger discharge flow rate than the booster pump;
And a step of discharging the fluid in the processing container from a discharge line connected to the processing container and provided with a pressure reducing valve for reducing the pressure in the processing container. Method. Circulating the fluid in the processing vessel to a circulation line, and then stopping the circulation;
Next, supplying a processing fluid from the supply line and extracting the fluid from the discharge line while maintaining the inside of the processing container in a high-pressure processing fluid atmosphere;
The substrate processing method according to claim 11, further comprising: stopping the supply of the processing fluid from the supply line and discharging the fluid in the processing container from the discharge line.   The substrate processing method according to claim 11, comprising a step of heating the fluid discharged from the processing container in the step of discharging the fluid to a temperature equal to or higher than a boiling point of the drying preventing liquid. . A computer program used in a substrate processing apparatus in which a processing fluid in a supercritical state or a subcritical state is brought into contact with a liquid for preventing drying on a substrate surface to remove the drying preventing liquid. A storage medium storing
14. A storage medium characterized in that the program includes steps for executing the substrate processing method according to any one of claims 11 to 13.

Images