Wafer processing equipment

Abstract

The present invention provides a wafer processing apparatus that can reduce particles on the wafer. [Solution] The wafer processing apparatus 1 comprises a chamber 11 for performing a predetermined process using a supercritical fluid on a wafer 2 housed in an internal storage space 22c, a first plate 24a disposed within the storage space 22c and adjusted to a first temperature, a second plate 25a disposed below the first plate 24a in the storage space 22c and adjusted to a second temperature, and an opening / closing means for opening and closing the chamber 11. Particles on the wafer 2 located between the first plate 24a and the second plate 25a in the storage space 22c are moved by thermophoresis corresponding to the temperature gradient between the first plate 24a and the second plate 25a caused by the difference between the first and second temperatures. In this way, particles on the wafer 2 can be reduced.

Description

Technical Field

[0001] The present invention relates to a wafer processing apparatus that performs a predetermined process on a wafer using a supercritical fluid.

Background Art

[0002] In recent years, the miniaturization of patterns formed on the surface of wafers has progressed, and the aspect ratio has been increasing. Therefore, if a processing liquid such as an organic solvent used for cleaning the pattern or the like is dried while remaining on the surface, there arises a problem that the pattern collapses due to the surface tension of the processing liquid. To solve such a problem, a supercritical fluid may be used for a process such as drying to remove the processing liquid from the surface of the substrate (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a process using a supercritical fluid, there has been a desire to reduce particles on the wafer.

[0005] The present invention has been made in view of the above situation, and an object thereof is to provide a wafer processing apparatus capable of reducing particles on a wafer in a process using a supercritical fluid.

Means for Solving the Problems

[0006] To achieve the above objective, a wafer processing apparatus according to one aspect of the present invention comprises a chamber for performing a predetermined process using a supercritical fluid on a wafer housed in an internal storage space, a first plate disposed within the storage space and adjusted to a first temperature, a second plate disposed below the first plate in the storage space and adjusted to a second temperature, and an opening and closing means for opening and closing the chamber, thereby moving particles on the wafer located between the first and second plates in the storage space by thermophoresis corresponding to the temperature gradient between the first and second plates caused by the difference between the first and second temperatures. With this configuration, particles on the wafer can be moved towards the plate with the lower temperature between the first and second plates using thermophoresis, thereby reducing the amount of particles on the wafer.

[0007] Furthermore, in a wafer processing apparatus according to one aspect of the present invention, the lower of the first and second temperatures may be the temperature at which the supercritical fluid in the containment space becomes liquid. This configuration allows for the efficient removal of particles from the containment space using a liquid with a higher viscosity than a supercritical fluid.

[0008] Furthermore, in a wafer processing apparatus according to one aspect of the present invention, the first temperature may be lower than the second temperature. With this configuration, particles on the wafer can be moved from the second plate side to the first plate side by thermophoresis.

[0009] Furthermore, in a wafer processing apparatus according to one aspect of the present invention, the chamber may have an outlet near the first plate in the containment space for discharging fluid from the containment space. This configuration allows particles that have moved to the first plate side to be efficiently discharged from the containment space.

[0010] Furthermore, in a wafer processing apparatus according to one aspect of the present invention, the second temperature may be lower than the first temperature. With this configuration, particles on the wafer can be moved from the first plate side to the second plate side by thermophoresis.

[0011] Furthermore, in a wafer processing apparatus according to one aspect of the present invention, the chamber may have an outlet near the second plate in the containment space for discharging fluid from the containment space. This configuration allows for efficient removal of particles that have moved to the second plate side from the containment space.

[0012] Furthermore, in a wafer processing apparatus according to one aspect of the present invention, during a predetermined process on a wafer housed in a storage space, the state in which the first temperature is lower than the second temperature and the state in which the second temperature is lower than the first temperature may be reversed. This configuration allows for the reduction of particles on both sides of the wafer. [Effects of the Invention]

[0013] According to one aspect of the present invention, a wafer processing apparatus can reduce particles on a wafer using thermophoresis. [Brief explanation of the drawing]

[0014] [Figure 1] A partially cutaway perspective view showing the configuration of a wafer processing apparatus according to an embodiment of the present invention. [Figure 2] Cross-sectional view showing the longitudinal section of the chamber of the wafer processing apparatus according to the same embodiment. [Figure 3] A schematic diagram illustrating particle movement using thermophoresis in the same embodiment. [Modes for carrying out the invention]

[0015] Hereinafter, the wafer processing apparatus according to the present invention will be described using embodiments. In the following embodiments, components denoted by the same reference numerals are the same or corresponding, and repeated descriptions may be omitted. The wafer processing apparatus according to the present embodiment reduces particles on a wafer using thermophoresis.

[0016] FIG. 1 is a partially cut-away perspective view showing the configuration of a wafer processing apparatus 1 according to the present embodiment. FIG. 2 is a cross-sectional view showing a longitudinal section of a chamber 11 of the wafer processing apparatus 1. In FIG. 2, a state where the chamber 11 is closed is shown. FIG. 3 is a schematic diagram for explaining the movement of particles 3 on a wafer 2 using thermophoresis.

[0017] The wafer processing apparatus 1 according to the present embodiment includes a chamber 11 for performing a predetermined process using a supercritical fluid on a wafer 2 housed in an internal accommodation space 22c, an opening / closing means 12 for opening and closing the chamber 11, a first temperature adjusting means 24 having a first plate 24a, and a second temperature adjusting means 25 having a second plate 25a. The first plate 24a disposed inside the chamber 11 is adjusted to a first temperature, and the second plate disposed inside the chamber 11 is adjusted to a second temperature. The first and second temperatures are different. In the present embodiment, the case where the first temperature is lower than the second temperature will be mainly described, and the case where it is not will be described later. Due to the temperature gradient between the first plate 24a and the second plate 25a caused by the difference between the first and second temperatures in the accommodation space 22c, a thermophoretic force acts on the particles on the wafer 2, and the particles on the wafer 2 move to the lower temperature side, and the particles on the wafer 2 are reduced.

[0018] In the containment space 22c within the chamber 11, a predetermined process using a supercritical fluid is performed on the wafer 2. In this embodiment, the case where the predetermined process is a drying process of the wafer 2 using a supercritical fluid will be mainly described, but other processes, such as a cleaning process or a cleaning and drying process using a supercritical fluid, may also be performed on the wafer 2. The drying process of the wafer 2 is performed, for example, by removing a processing liquid such as an organic solvent remaining on the surface of the wafer 2 by replacing it with a supercritical fluid, and then drying the supercritical fluid. When a process using a supercritical fluid is performed in the containment space 22c of the chamber 11, the temperature and pressure of the containment space 22c exceed the critical point. Therefore, the predetermined process using a supercritical fluid is usually performed at a pressure higher than atmospheric pressure, i.e., under pressurized conditions. In this embodiment, the case where the fluid used for the process is carbon dioxide, i.e., a supercritical fluid of carbon dioxide, will be mainly described, but other supercritical fluids may also be used.

[0019] The chamber 11 may have, for example, an upper unit 21 and a lower unit 22. The upper unit 21 and the lower unit 22 face each other, and together they may form a storage space 22c for accommodating the wafer 2. The storage space 22c is usually a roughly cylindrical space. If the volume of the storage space 22c is large, the time required to increase the pressure to bring the fluid to a supercritical state will be longer, so it is preferable that the volume of the storage space 22c be small. In this embodiment, the case in which the storage space 22c is formed on the lower unit 22 side will be mainly described. As shown in Figure 2, the upper unit 21 and the lower unit 22 may each be provided with cylindrical holes 21e and 22e that extend in the vertical direction. The holes 21e and 22e may be used to mount a first temperature adjustment means 24 and a second temperature adjustment means 25, respectively.

[0020] As shown in FIG. 2, the lower unit 22 may be provided with a fluid injection path 221 and a discharge path 222. In the present embodiment, in a plan view, the fluid inlet is provided on the peripheral side of the accommodation space 22c, and the fluid outlet is provided on the peripheral side facing the inlet of the accommodation space 22c and around the hole 22e. However, these are merely examples, and the arrangements of the inlet, the outlet, the injection path 221, and the discharge path 222 may be different from these. For example, the injection path 221 may be provided to inject fluid from the upper surface side of the wafer 2. Also, for example, the injection path 221 and the discharge path 222 may be provided on the lateral side (side surface) of the accommodation space 22c within a range that does not interfere with the clamp 41 described later. Note that the fluid injection path 221 and the discharge path 222 are preferably provided in the fixed-side unit rather than the movable-side unit.

[0021] The upper unit 21 and the lower unit 22 are preferably made of a pressure-resistant material. The material may be, for example, stainless steel or the like. Also, a treatment for forming a passivation film for preventing the generation of particles or a DLC treatment for hardening may be performed on the surface thereof.

[0022] The chamber 11 may have a seal portion 23 for sealing between the upper unit 21 and the lower unit 22 when the chamber 11 is closed. The seal portion 23 is an annular member and may be disposed at the annular edge portion of the opening of the accommodation space 22c in the lower unit 22 or at the portion of the upper unit 21 facing the edge portion. The seal portion 23 may be attached, for example, to the lower end side of the upper unit 21 as shown in FIG. 2. The seal portion 23 may have a substantially U-shaped cross section. In that case, when the chamber 11 is closed and the fluid in the accommodation space 22c attempts to flow out through the seal portion 23, the pressure in the inner portion of the substantially U-shaped cross section increases, improving the sealing property, and effectively preventing the outflow of the fluid in the accommodation space 22c. The seal portion 23 may be made of, for example, a fluororesin such as polytetrafluoroethylene or a material such as silicon.

[0023] The opening / closing means 12 may open and close the chamber 11 by, for example, moving at least one of the upper unit 21 and the lower unit 22 in the vertical direction. The upper unit 21 and the lower unit 22 may be closed by the opening / closing means 12 and fitted together to form a housing space 22c for processing the wafer 2. Furthermore, the airtightness of the housing space 22c is enhanced by the seal portion 23, and the upper seal portion 21d and lower seal portion 22d, which will be described later. In this embodiment, the opening / closing means 12 is an air cylinder fixed to the base 15, and the upper unit 21 is moved in the vertical direction by moving the four corners of the rectangular top plate 16 in the vertical direction at the same timing relative to the base 15. Note that some of the opening / closing means 12 are omitted in Figure 1.

[0024] The opening / closing mechanism 12 may be composed of a solenoid other than an air cylinder, a rotary drive mechanism for driving a rack and pinion and pinion, or a rotary drive mechanism for rotating a ball screw and screw shaft. In addition, the opening / closing mechanism 12 may be provided at one to three of the four corners of the top plate 16, and guide members may be provided at the other locations to guide the top portion of the top plate 16 in the vertical direction. In this embodiment, the case in which the opening / closing mechanism 12 moves the upper unit 21 in the vertical direction will be described, but this is not required. The opening / closing mechanism 12 may move the lower unit 22 in the vertical direction, or both the upper unit 21 and the lower unit 22 may be moved in opposite directions in the vertical direction.

[0025] The first temperature control means 24 may have a first plate 24a extending horizontally in the housing space 22c and a cylindrical support portion 24b connected to the upper surface of the first plate 24a. The first plate 24a may be, for example, disc-shaped. One end of the support portion 24b may be fixed near the center of the disc-shaped first plate 24a such that the plane of the first plate 24a and the central axis of the cylindrical shape of the support portion 24b are perpendicular to each other. The first plate 24a and the support portion 24b may be, for example, integrally constructed or independent members. The first temperature control means 24 may be attached to the upper unit 21 by inserting the support portion 24b of the first temperature control means 24 into a cylindrical hole 21e provided in the upper unit 21. The support portion 24b may be entirely cylindrical, or at least a part of it may be cylindrical. In this embodiment, we will mainly describe the case where the support portion 24b is composed of multiple cylindrical portions with different radii, as shown in Figure 2. The same applies to the support portion 25b, which will be described later.

[0026] As shown in Figure 2, there may or may not be a horizontally extending gap through which fluid can flow between the upper surface of the first plate 24a of the first temperature control means 24 and the lower surface of the upper unit 21. In the former case, the first temperature control means 24 may be attached to the upper unit 21 such that there is a predetermined vertical gap between the upper surface of the first plate 24a and the lower surface of the upper unit 21.

[0027] The second temperature adjustment means 25 may have a second plate 25a extending horizontally in the housing space 22c and a cylindrical support portion 25b connected to the lower surface of the second plate 25a. The second temperature adjustment means 25 is the same as the first temperature adjustment means 24 except that the temperatures of the first plate 24a and the second plate 25a are different and their orientation is reversed, so a detailed explanation is omitted. The second temperature adjustment means 25 is attached to the lower unit 22 by inserting the support portion 25b of the second temperature adjustment means 25 into a cylindrical hole 22e provided in the lower unit 22.

[0028] As shown in Figure 2, there may or may not be a horizontally extending gap through which fluid can flow between the lower surface of the second plate 25a of the second temperature adjustment means 25 and the upper surface of the lower unit 22. For example, if an outlet is provided on the lower side of the second plate 25a of the second temperature adjustment means 25, it is preferable that such a gap exists.

[0029] The first plate 24a is adjusted to a first temperature, and the second plate 25a is adjusted to a second temperature. Note that the first and second temperatures are different, and as described above, this embodiment mainly describes the case where the first temperature is lower than the second temperature. Of the first plate 24a and the second plate 25a, the one adjusted to the lower temperature may, for example, have a flow passage through which a cooling medium flows, and may be cooled by the flow of the cooling medium through that passage. Of the first plate 24a and the second plate 25a, the one adjusted to the higher temperature may, for example, have a flow passage through which a heating medium flows, and may be heated by the flow of the heating medium through that passage, or may be heated by an electric heating means such as an electric heating wire such as a nichrome wire or a ceramic heater. The cooling medium and the heating medium may be, for example, a liquid medium. Also, the medium may be water as an example. Furthermore, the first plate 24a and the second plate 25a may be made of a material with high thermal conductivity, for example. The material with high thermal conductivity may be a metal such as stainless steel.

[0030] Furthermore, if a cooling medium is used to cool the first plate 24a, the wafer processing apparatus 1 may further include, for example, a heat exchanger (not shown) for cooling the cooling medium discharged from the flow passage of the first plate 24a, and a pump (not shown) for circulating the cooling medium, and the cooling medium cooled by the heat exchanger may be returned to the flow passage of the first plate 24a by the pump. The same may apply when a cooling medium is used to cool the second plate 25a.

[0031] Furthermore, if a heating medium is used to heat the second plate 25a, the wafer processing apparatus 1 may further include, for example, a heat exchanger (not shown) for heating the heating medium discharged from the flow passage of the second plate 25a, and a pump (not shown) for circulating the heating medium, and the heating medium heated by the heat exchanger may be returned to the flow passage of the second plate 25a by the pump. The same may apply when a heating medium is used to heat the first plate 24a.

[0032] Thermophoresis is a phenomenon that occurs when a temperature gradient exists around a particle. The particle receives greater momentum from molecules on the higher temperature side than from molecules on the lower temperature side, resulting in the particle moving from the higher temperature side to the lower temperature side. The force acting on the particle due to this thermophoresis is sometimes called thermophoretic force.

[0033] If the temperature of the first plate 24a is lower than the temperature of the second plate 25a, the particles present on the upper surface of the wafer 2 will move upward due to thermophoresis corresponding to the temperature gradient between the two. In such a situation, as shown in Figure 3, if the fluid is flowing in the containment space 22c as indicated by the leftward arrow, the particles 3 removed from the upper surface of the wafer 2 will move in the upper left direction. For example, in Figure 3, if there is a fluid outlet to the left of the first plate 24a, the particles 3 may be discharged to the outside of the containment space 22c through that outlet. As an example, as shown in Figure 2, if the chamber 11 has an outlet 224 for discharging fluid from the containment space 22c near the first plate 24a in the containment space 22c, and the fluid is flowing from right to left in the containment space 22c, the particles 3 removed from the upper surface of the wafer 2 may be discharged through the outlet 224. Furthermore, the statement that the chamber 11 has an outlet 224 near the first plate 24a means, for example, that the distance from the outlet 224 to the first plate 24a is shorter than the distance from the outlet 224 to the second plate 24a. The distance from the outlet 224 to the first plate 24a or the second plate 25a may be, for example, the shortest distance between them.

[0034] A large temperature gradient between the first plate 24a and the second plate 25a is preferable. Therefore, the temperature difference between the first and second plates is preferably 40°C or more, more preferably 50°C or more, even more preferably 60°C or more, and even more preferably 80°C or more. For example, the higher of the two temperatures may be 80°C and the lower of the two temperatures may be 0°C. Another example is that the higher of the two temperatures may be 60°C and the lower of the two temperatures may be 0°C.

[0035] Furthermore, the lower of the first and second temperatures may be, for example, a temperature lower than the critical temperature at which the supercritical fluid in the containment space 22c becomes liquid. Even in this case, it is preferable that the area around the wafer 2 is a supercritical fluid. In the case of a carbon dioxide supercritical fluid, the lower of the first and second temperatures may be a temperature lower than the critical temperature of 31.1°C. For example, the lower temperature may be 30°C or lower, 20°C or lower, 10°C or lower, or 0°C or lower. In this way, by setting the lower of the first and second temperatures to the temperature at which the supercritical fluid becomes liquid, particles that have moved to the plate side at the lower temperature can be efficiently discharged by a liquid with a higher viscosity than the supercritical fluid.

[0036] Furthermore, it is preferable that the higher of the first and second temperatures is a temperature higher than the critical temperature, which is the temperature at which the supercritical fluid in the containment space 22c is maintained. For example, the plate with the higher of the first and second temperatures may be used to heat the fluid in the containment space 22c to make it a supercritical fluid. In the case of a supercritical fluid of carbon dioxide, it is preferable that the higher of the first and second temperatures is a temperature higher than the critical temperature of 31.1°C. For example, the higher temperature may be, for example, 40°C or higher, 50°C or higher, 60°C or higher, or 80°C or higher.

[0037] The upper seal portion 21d may seal the space between the support portion 24b of the first temperature adjustment means 24 and the hole portion 21e of the upper unit 21. The lower seal portion 22d may seal the space between the support portion 25b of the second temperature adjustment means 25 and the hole portion 22e of the lower unit 22. The upper seal portion 21d prevents fluid leakage from between the support portion 24b and the hole portion 21e, and the lower seal portion 22d prevents fluid leakage from between the support portion 25b and the hole portion 22e, thereby maintaining an airtight seal in the containment space 22c. The upper seal portion 21d and the lower seal portion 22d may be the same as the seal portion 23.

[0038] The first temperature adjustment means 24 and the second temperature adjustment means 25 may be removed, for example, for maintenance. When they are attached and detached in this way, particles are likely to be generated at the contact points between the first temperature adjustment means 24 and the second temperature adjustment means 25 and the chamber 11, more specifically at the upper seal portion 21d and the lower seal portion 22d. It is preferable that such particles be discharged so as not to diffuse into the wafer 2. As a method for discharging the generated particles, for example, the method described in Japanese Patent Application Publication No. 2002-324777 or Japanese Patent Application Publication No. 2007-036109 may be used.

[0039] The lower surface of the first plate 24a may be provided with, for example, a plurality of wafer support portions 21a that support the wafer 2 being fed in horizontally. Therefore, when the wafer 2 is fed in, the wafer 2 may be positioned below the first plate 24a, as shown in Figure 2. The wafer support portions 21a may, for example, have a substantially L-shaped cross-section, as shown in Figure 2, and support the peripheral edge of the fed wafer 2 at the tip portion that extends horizontally.

[0040] The wafer processing apparatus 1 may have a clamp 41 that tightens the periphery of the chamber 11 when the chamber 11 is closed, i.e., when the upper unit 21 and the lower unit 22 are fitted together in the vertical direction and the internal storage space 22c is kept airtight. The clamp 41 may be fixed to the upper surface of the stage 42. A slide rail 43 is fixed to the base 15, and a slide guide 44 may be slidably provided on the slide rail 43. The slide guide 44 is fixed to the stage 42, which may allow the clamp 41 to move in the longitudinal direction of the slide rail 43. The movement of the clamp 41, i.e., the movement of the stage 42, may be achieved using a drive means (not shown). The drive means may be, for example, an air cylinder or solenoid, a rack and pinion and a rotational drive means for driving the pinion, a ball screw and a rotational drive means for rotating the screw shaft, etc. The clamp 41 moves between the locked position and the released position of the chamber 11 by the drive means. In this embodiment, we will mainly describe the case in which the upper unit 21 and lower unit 22 of the chamber 11 are locked by three clamps 41, as shown in Figure 1. However, the number of clamps 41 may be, for example, two or four or more. The movement of the multiple clamps 41 between the locked position and the released position may be performed independently or in conjunction with each other.

[0041] Next, the operation of the wafer processing apparatus 1 according to this embodiment will be described in detail. In this specific example, as described above, the first temperature of the first plate 24a is lower than the second temperature of the second plate 25a.

[0042] First, with the upper unit 21 and lower unit 22 of the wafer processing apparatus 1 separated vertically, the wafer 2, which has been cleaned by the cleaning apparatus in the previous process using a cleaning agent such as IPA (isopropyl alcohol), is transported by the hand of the transport robot and brought onto the lower side of the first plate 24a. The brought-in wafer 2 is then supported by the wafer support section 21a.

[0043] Next, the top plate 16 is lowered by the opening / closing mechanism 12, thereby closing the chamber 11. Also, the stage 42 is moved toward the axis of the chamber 11, and the upper unit 21 and the lower unit 22 are locked by the clamp 41 (Figure 2).

[0044] Subsequently, an injection valve connected to the carbon dioxide injection channel 221 is opened, and carbon dioxide is injected into the containment space 22c of the chamber 11. The carbon dioxide is pressurized using a boosting mechanism, such as a pressure pump, and then injected into the containment space 22c. The injected carbon dioxide is also heated by a second plate 25a, which is adjusted to a second temperature.

[0045] When the injected carbon dioxide reaches a critical state when the pressure in the containment space 22c exceeds the critical pressure of 7.38 MPa and the temperature exceeds the critical temperature of 31.1°C, it enters a supercritical state, and the IPA and other substances on wafer 2 are dissolved in the supercritical carbon dioxide.

[0046] Furthermore, after the fluid in the containment space 22c becomes a supercritical fluid, the first plate 24a is adjusted to a first temperature, creating a temperature gradient between the first plate 24a and the second plate 25a. As a result, particles adhering to the upper surface of the wafer 2 move towards the first plate 24a.

[0047] When the pressure of the supercritical carbon dioxide (supercritical fluid) in the containment space 22c exceeds a certain value, the supercritical fluid is gradually discharged by the discharge valve (pressure regulating valve) connected to the discharge passage 222 while maintaining the pressure in the containment space 22c. In accordance with the discharge of this fluid, particles removed from the wafer 2 by thermophoresis are discharged from the discharge port 224, etc. In addition, the supercritical fluid in which IPA and other substances that were attached to the wafer 2 have dissolved is also discharged, and the IPA and other substances are removed from the wafer 2 in the containment space 22c.

[0048] Furthermore, it is preferable that the containment space 22c be maintained at a pressure and temperature at which carbon dioxide reaches a supercritical state, at least until the discharge of IPA, etc., is completed. For example, it is preferable that the pressure of the containment space 22c be maintained at 7.4 to 15 MPa and the temperature be maintained at 31 to 50°C by the second plate 25a.

[0049] As carbon dioxide continues to be injected into the containment space 22c, the injection of supercritical carbon dioxide fluid and the discharge of fluids containing IPA and particles occur in parallel. Once the discharge of fluids containing IPA is complete, the injection valve is closed, the containment space 22c is depressurized by the discharge valve, and the supercritical fluid is discharged after undergoing a phase change to gas. After that, the discharge valve is closed. The containment space 22c may be kept at 31-50°C, or the heating may be stopped. Whether the discharge of IPA has been completed may be confirmed, for example, by detecting IPA in the containment space 22c using a sensor that detects IPA. The sensor that detects IPA may be, for example, an alcohol detection sensor.

[0050] Subsequently, each clamp 41 is moved to the release position. The top plate 16 is raised by the opening / closing means 12, opening the chamber 11 and separating the upper unit 21 and the lower unit 22. The wafer 2, dried using the supercritical fluid, is then unloaded by the hand of the transport robot. The above process may then be repeated. The timing and other controls for the above series of processes may be performed by control means (not shown).

[0051] Next, we will describe experimental examples using the wafer processing apparatus 1 according to this embodiment. In these experimental examples, we conducted an experiment in which the first plate 24a was cooled to 0°C and the second plate 25a was heated to 60°C (hereinafter referred to as "Experimental Example 1"), and an experiment in which the first plate 24a and the second plate 25a were each heated to 60°C (hereinafter referred to as "Experimental Example 2"). In Experimental Examples 1 and 2, a 12-inch wafer 2 was placed in a containment space 22c where the injected carbon dioxide was in a supercritical state for a predetermined time, and the number of particles with a particle size of 42 nm on the wafer 2 thereafter was compared. As a result, the number of particles with a particle size of 42 nm present on the wafer 2 after Experimental Example 1 was approximately 52% of the number of particles with a particle size of 42 nm present on the wafer 2 after Experimental Example 2. Therefore, by using thermophoresis, approximately 48% of the 42 nm particle size particles on wafer 2 were removed, confirming that thermophoresis is effective in reducing particles.

[0052] As described above, according to the wafer processing apparatus 1 of this embodiment, particles on the wafer 2 can be reduced by moving particles on the wafer 2, which are placed between the first plate 24a and the second plate 25a in the containment space 22c, through thermophoresis in accordance with the temperature gradient between the first plate 24a and the second plate 25a.

[0053] Note that Figure 2 shows a case where the wafer 2 is supported by a wafer support portion 21a below the first plate 24a, but this is not required. The wafer 2 may, for example, be placed on a second plate 25a, or supported by one or more wafer support portions provided on the upper surface of the second plate 25a. When the wafer 2 is placed on the second plate 25a or supported by wafer support portions provided on the upper surface of the second plate 25a, for example, when the wafer 2 is housed in the accommodation space 22c of the chamber 11, the wafer 2 may first be supported by a wafer support portion 21a provided below the first plate 24a, and then transferred from the wafer support portion 21a to the upper surface of the second plate 25a, or to a wafer support portion provided on the upper surface thereof. For details on such a transfer of the wafer 2, please refer to, for example, Patent Document 1.

[0054] Furthermore, although this embodiment mainly describes the case where the first temperature is lower than the second temperature, this is not necessarily the case. The second temperature may also be lower than the first temperature. In this case, for example, the first plate 24a may be heated and the second plate 25a may be cooled. With such a configuration, particles on the lower surface side of the wafer 2 can be reduced by thermophoresis according to the first and second temperatures. In this case, the chamber 11 may have an outlet near the second plate 25a in the containment space 22c for discharging fluid from the containment space 22c. This is to efficiently discharge particles that have moved to the second plate 25a side by thermophoresis.

[0055] Here, if the wafer 2 is supported by a wafer support portion 21a provided on the lower side of the first plate 24a, or if the wafer 2 is supported by a wafer support portion provided on the upper side of the second plate 25a and there is a gap between the upper surface of the second plate 25a and the lower surface of the wafer 2, the first temperature may be lower than the second temperature, or the second temperature may be lower than the first temperature.

[0056] On the other hand, if the wafer 2 is supported by a wafer support provided on the upper surface side of the second plate 25a and there is no gap between the upper surface of the second plate 25a and the lower surface of the wafer 2, or if the wafer 2 is placed on the upper surface of the second plate 25a and there is no gap between the upper surface of the second plate 25a and the lower surface of the wafer 2, then it is preferable that the first temperature be lower than the second temperature. In this case, even if the second temperature is lower than the first temperature, the particles on the lower surface side of the wafer 2 cannot move.

[0057] Furthermore, although this embodiment mainly describes the case where the first plate 24a is supported by the support portion 24b, this is not required. The first plate 24a may be supported by other configurations as long as it is placed in the containment space 22c and adjusted to a first temperature. The same applies to the second plate 25a. The second plate 25a may be supported by other configurations as long as it is placed below the first plate 24a in the containment space 22c and adjusted to a second temperature.

[0058] Furthermore, although this embodiment mainly describes the case in which the chamber 11 is composed of an upper unit 21 and a lower unit 22, it is not limited to this configuration. The chamber 11 is not limited to such a configuration as long as it can perform a predetermined processing using a supercritical fluid on the wafer 2 housed in the internal housing space 22c. For example, the chamber may house the wafer in the housing space by sliding a tray on which the wafer is placed horizontally. For such a chamber, please refer to, for example, Japanese Patent Application Publication No. 2013-033962. In this case, the opening and closing means may, for example, slide the tray on which the wafer is placed horizontally. Even in such a case, by arranging a first plate adjusted to a first temperature above the wafer and a second plate adjusted to a second temperature below the wafer in the housing space, particles on the wafer can be reduced by thermophoresis according to the temperature gradient between the first and second plates caused by the difference between the first and second temperatures.

[0059] Furthermore, although this embodiment mainly describes the case where either the first temperature is lower than the second temperature or the second temperature is lower than the first temperature, this is not required. In the wafer processing apparatus 1, during a predetermined process on the wafer 2 housed in the storage space 22c, the state in which the first temperature is lower than the second temperature and the state in which the second temperature is lower than the first temperature may be reversed. By doing so, for example, when the first temperature is lower than the second temperature, particles adhering to the upper surface of the wafer 2 can be reduced, and when the second temperature is lower than the first temperature, particles adhering to the lower surface of the wafer 2 can be reduced. In this case, it is preferable that the wafer 2 is supported in the storage space 22c such that there are gaps on both the upper and lower sides. Also, the number of times the state in which the first temperature is lower than the second temperature and the state in which the second temperature is lower than the first temperature are reversed is not limited. For example, both states may be reversed only once, or they may be reversed multiple times.

[0060] Furthermore, in this embodiment, the case in which the fluid flows mainly from right to left in Figure 2, that is, the case in which the fluid flows mainly linearly from the inlet to the outlet 224 of the injection passage 222, has been described. However, it goes without saying that the fluid flow in the containment space 22c may be other than that. For example, in a plan view, the fluid may flow radially in the radial direction of the wafer 2 from the center of the wafer 2 contained in the containment space 22c toward the periphery.

[0061] Furthermore, although this embodiment describes a case where the first plate 24 and the second plate 25a do not rotate, this is not required. At least one of the first plate 24 and the second plate 25a may rotate. This rotation may be, for example, rotation around the central axis of the support parts 24b and 25b, which are provided to be rotatable by a rotary bearing. For information on the mechanism for rotating the first and second temperature adjustment means 24 and 25, please refer to, for example, the above-mentioned Patent Document 2.

[0062] Furthermore, the embodiments described above are illustrative examples for specifically carrying out the present invention and do not limit the technical scope of the present invention. The technical scope of the present invention is indicated by the claims rather than by the description of the embodiments, and modifications within the literal scope and equivalent meaning of the claims are intended. [Explanation of symbols]

[0063] 1. Wafer processing equipment 2 wafers 11 Chambers 12 Opening and closing means 24a First plate 25a Second plate

Claims

1. A chamber for performing a predetermined process using a supercritical fluid on a wafer housed in an internal containment space, A first plate is placed within the aforementioned containment space and is adjusted to a first temperature, A second plate is positioned below the first plate within the aforementioned containment space and is adjusted to a second temperature. The chamber comprises an opening and closing means for opening and closing the chamber, A wafer processing apparatus that moves particles on a wafer placed between the first and second plates in the containment space by thermophoresis corresponding to a temperature gradient between the first and second plates caused by the temperature difference between the first and second plates.

2. The wafer processing apparatus according to claim 1, wherein the lower of the first and second temperatures is the temperature at which the supercritical fluid in the containment space becomes liquid.

3. The wafer processing apparatus according to claim 1 or claim 2, wherein the first temperature is lower than the second temperature.

4. The wafer processing apparatus according to claim 3, wherein the chamber has an outlet for discharging fluid from the containment space near the first plate in the containment space.

5. The wafer processing apparatus according to claim 1 or claim 2, wherein the second temperature is lower than the first temperature.

6. The wafer processing apparatus according to claim 5, wherein the chamber has an outlet for discharging fluid from the containment space near the second plate in the containment space.

7. A wafer processing apparatus according to claim 1 or claim 2, wherein during a predetermined process on a wafer housed in the storage space, the state in which the first temperature is lower than the second temperature is reversed, and the state in which the second temperature is lower than the first temperature is reversed.

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