Supercritical wafer cleaning / drying medium recovery method and system

Abstract

To provide a supercritical wafer cleaning / drying medium recovery method and system that enables the continuous separation and recovery of high-purity cleaning / drying media in the field of wafer processing.SOLUTION: A method includes a cleaning / drying step of dissolving and removing an organic solvent attached on a wafer by a cleaning / drying medium in a supercritical state to obtain a mixed medium carrying the organic solvent, a depressurization step of reducing the pressure of the mixed medium to first pressure after the cleaning / drying step, and an adsorption step of heating the depressurized mixed medium to first temperature after the depressurization step to obtain a gaseous mixed medium, bringing the gaseous mixed medium into contact with an organic solvent adsorbent in an adsorber, and causing the organic solvent in the mixed medium to be adsorbed and concentrated by the organic solvent adsorbent and separated from the cleaning / drying medium.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the field of wafer processing, and specifically, to a method and system for recovering a supercritical wafer cleaning / drying medium.

Background Art

[0002] Semiconductor wafers are the most important materials in the semiconductor industry, and the requirements for their surface cleanliness are quite strict. In the semiconductor wafer processing process, wafer surface cleaning and drying are essential processes to effectively remove the solvents on the wafer surface and keep the wafer surface clean. On the other hand, some supercritical media have the characteristic that their surface tension is zero, so they can smoothly enter the pore structure on the wafer surface and achieve efficient removal of solvents.

[0003] In the conventional cleaning and drying process using supercritical media, usually, the supercritical cleaning / drying medium is used as a "disposable" consumable. However, due to the large consumption of the supercritical cleaning / drying medium in the cleaning and drying process, the cost of wafer cleaning / drying becomes very high. Furthermore, under a specific temperature and / or pressure environment, there is a possibility that the solvent and the cleaning / drying medium are somewhat miscible, so it is difficult to separate and recover the cleaning / drying medium by simple separation means (such as gas-liquid separation or liquid-liquid separation), and often a large amount of solvent impurities remain in the recovered cleaning / drying medium, which may result in low purity.

[0004] Therefore, in this field, there is an urgent need for a high-purity supercritical wafer cleaning / drying medium recovery process to reduce the cleaning and drying costs of semiconductor wafers.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above points, the present invention provides a method and system for recovering a supercritical wafer cleaning / drying medium that can achieve continuous separation and recovery of a high-purity cleaning / drying medium.

Means for Solving the Problem

[0006] The first aspect of the present invention is a method for recovering a supercritical wafer cleaning / drying medium, comprising: a cleaning / drying step of dissolving and removing an organic solvent adhering to a wafer with a supercritical cleaning / drying medium to obtain a mixed medium carrying the organic solvent; a depressurizing step of depressurizing the pressure of the mixed medium to a first pressure after the cleaning / drying step; an adsorption step of heating the depressurized mixed medium to a first temperature after the depressurizing step to obtain a gaseous mixed medium, bringing the gaseous mixed medium into contact with an organic solvent adsorbent in an adsorber, adsorbing and concentrating the organic solvent in the mixed medium on the organic solvent adsorbent, and separating it from the cleaning / drying medium. A method for recovering a supercritical wafer cleaning / drying medium is provided.

[0007] According to this technical solution, the organic solvent used in the wafer processing process is generally an organic solvent (such as alcohol, ketone, and ester-based organic solvents) that is relatively soluble in the supercritical cleaning / drying medium and is difficult to separate from the supercritical cleaning / drying medium. However, the organic solvent adsorbent is a material with high porosity and can adsorb the organic solvent gas on the surface or pores by the adsorption action. Thus, by depressurizing the mixed medium of the organic solvent and the cleaning / drying medium to the first pressure, heating it to the first temperature to form a gaseous mixed medium, and spraying the gaseous mixed medium onto the organic solvent adsorbent, the adsorption of the organic solvent can be realized. Throughout the adsorption process, the cleaning / drying medium is not blocked or concentrated, and the organic solvent adsorbent has high selectivity for the organic solvent, so the loss in the separation of the cleaning / drying medium is reduced. In addition, due to the adsorption of the organic solvent by the organic solvent adsorbent, the gaseous cleaning / drying medium and the organic solvent can be continuously separated, and a high-purity cleaning / drying medium can be continuously discharged, realizing the recovery of the high-purity cleaning / drying medium.

[0008] As a preferred technical solution, the method for recovering a supercritical wafer cleaning / drying medium further comprises: Determine whether the organic solvent adsorbent in the first adsorber has reached the adsorption threshold. If it has reached, an adsorber switching step of switching the adsorber in the adsorption step from the first adsorber to the second adsorber, After the adsorber switching step, heat up the organic solvent adsorbent in the first adsorber to a second temperature. After the organic solvent desorbs from the organic solvent adsorbent in the first adsorber, it is discharged from the first adsorber and flows into the organic solvent collection port, including a desorption step.

[0009] According to this technical solution, through the adsorber switching step, immediately before the organic solvent adsorbent in the first adsorber reaches the adsorption equilibrium, the adsorption step is switched to the second adsorber and continuously performed. At the same time, in the desorption step, the organic solvent adsorbent in the first adsorber is heated up, and by changing the adsorption equilibrium of the organic solvent adsorbent in the first adsorber, the desorption of the organic solvent in the organic solvent adsorbent in the first adsorber is promoted, ensuring that the separation of the cleaning / drying medium can be continuously carried out, and it is possible to improve the separation and recovery efficiency of the cleaning / drying medium.

[0010] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery method further includes a purification step of removing the organic solvent adsorbent pellets in the cleaning / drying medium separated in the adsorption step.

[0011] According to this technical solution, since the organic solvent adsorbent in the adsorption step may deviate during the adsorption / desorption process, by removing the organic solvent adsorbent in the cleaning / drying medium separated in the adsorption step, a higher purity cleaning / drying medium can be obtained.

[0012] As a preferred technical solution, the organic solvent adsorbent is an activated carbon adsorbent or a molecular sieve adsorbent with a pore diameter in the range of 0.7 nm - 0.9 nm, and the cleaning / drying medium is carbon dioxide.

[0013] According to this technical solution, the surface tension of supercritical carbon dioxide becomes zero, and the organic solvent can be rapidly dissolved. In addition, both the activated carbon adsorbent and the molecular sieve adsorbent with a pore diameter in the range of 0.7 nm - 0.9 nm have very high porosity, a high adsorption rate of the organic solvent, and can adsorb almost all of the alcohol, ketone, and ester-based organic solvent gases mixed therein without affecting the passage of carbon dioxide gas.

[0014] As a preferred technical solution, the first pressure is 3 - 9 MPa, the first temperature is 30 - 90 °C, and the second temperature is 150 - 300 °C.

[0015] According to this technical solution, when the pressure of the mixed medium of carbon dioxide and the organic solvent is within the range of 3 - 9 MPa and the temperature is within the range of 30 - 90 °C, carbon dioxide becomes a subcritical gas state. At this time, carbon dioxide and the organic solvent are almost immiscible, and the organic solvent adsorbent shows a very high adsorption equilibrium concentration for the gaseous organic solvent. Therefore, the organic solvent adsorbent can almost completely separate and adsorb the gaseous organic solvent in the mixed medium passing through the organic solvent adsorbent, and the separated high-purity gaseous carbon dioxide can rapidly pass through the organic solvent adsorbent and continuously flow out. Then, by further heating to 150 - 300 °C, the adsorption equilibrium concentration of the organic solvent adsorbent for the organic solvent is reduced, and the desorption of the organic solvent from the organic solvent adsorbent is promoted. In addition, since the activated carbon adsorbent and the molecular sieve adsorbent with a pore diameter in the range of 0.7 nm - 0.9 nm do not chemically react with the organic solvent, the desorbed organic solvent can be recovered through the organic solvent collection port and reused.

[0016] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery method further includes a gas supply step of supplying the supercritical cleaning / drying medium used in the cleaning / drying step by pressurizing and heating the gaseous cleaning / drying medium separated in the adsorption step and / or the external medium supplied from an external gas source to obtain a supercritical cleaning / drying medium, Pressurize and transport the gaseous cleaning / drying medium obtained in the suction step, and include a pressure adjustment step of adjusting the pressure of the pressurized cleaning / drying medium to be the same as the pressure of the external medium before the gas supply step.

[0017] According to this technical solution, since a part of the cleaning / drying medium remains on the wafer surface, there is a certain degree of loss of the cleaning / drying medium during the cycle. However, by mixing the external gas source and the gaseous cleaning / drying medium obtained in the suction step to supply gas, the cycle utilization of the cleaning / drying medium and the replenishment of the loss of the cleaning / drying medium during the cycle are realized, and the amount of the supercritical state medium used for cleaning / drying in the cleaning / drying step after multiple cycles can be maintained.

[0018] Furthermore, the cleaning / drying medium obtained in the suction step is in a low-pressure gaseous state and has a slow flow rate. Therefore, after accelerating the flow rate of the cleaning / drying medium by pressurization in the pressure adjustment step, by making the pressure before executing the gas supply step equal to the pressure of the external gas source through pressure adjustment, the pressure of the gaseous cleaning / drying medium entering the gas supply step can be stabilized. Here, the external medium stored in the external gas source may be a gaseous or liquid medium.

[0019] The second aspect of the present invention provides a supercritical wafer cleaning / drying medium recovery system including a cleaning / drying device for dissolving and removing the organic solvent adhered to the wafer by a supercritical state cleaning / drying medium with a wafer built-in to obtain a mixed medium carrying the organic solvent, a first pressure reducing valve communicating with the outlet of the cleaning / drying device for reducing the pressure of the mixed medium to the first pressure, and an adsorption / desorption unit with an organic solvent adsorbent built-in and communicating with the outlet of the first pressure reducing valve. The adsorption / desorption unit has a first heating device for heating the mixed medium entering the adsorption / desorption unit to the first temperature to obtain a gaseous mixed medium. The gaseous mixed medium contacts the organic solvent adsorbent, and the organic solvent in the mixed medium is adsorbed and concentrated by the organic solvent adsorbent and separated from the cleaning / drying medium.

[0020] As a preferred technical solution, the adsorption / desorption unit includes a plurality of adsorbers with an organic solvent adsorbent built therein and a first heating device. The plurality of adsorbers are provided in parallel, the inlets of the plurality of adsorbers communicate with the outlet of the first pressure reducing valve, and an organic solvent collection port communicates with the solvent outlets of the plurality of adsorbers. The first heating device is provided around the plurality of adsorbers and is used to control the temperature of the plurality of adsorbers to a first temperature or a second temperature higher than the first temperature.

[0021] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery system further includes a purifier that communicates with the medium outlets of the plurality of adsorbers and removes the organic solvent adsorbent pellets in the cleaning / drying medium.

[0022] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery system further includes a gas supply unit that communicates with the medium outlet of the adsorption / desorption unit and the inlet of the cleaning / drying device, pressurizes and heats the cleaning / drying medium flowing out from the adsorption / desorption unit to obtain a supercritical cleaning / drying medium for use in the cleaning / drying device, an external gas source whose outlet communicates with the inlet of the gas supply unit, and a pressure adjustment device that communicates with the medium outlet of the adsorption / desorption unit and the inlet of the external gas source and includes a compressor and a second pressure reducing valve that communicate in sequence along the fluid flow direction.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying out the Invention

[0024] Hereinafter, the present invention will be described in more detail with reference to specific examples and drawings. The realization of the present invention is not limited to the following embodiments, and various deformations, substitutions, combinations, and improvements under the technical idea of the present invention adopted within the knowledge scope of those skilled in the art all belong to the protection scope of the present invention.

[0025] First Embodiment As shown in FIG. 1, the first embodiment of the present invention is a supercritical wafer cleaning / drying medium recovery method, comprising: a cleaning / drying step S1 of dissolving and removing the organic solvent adhered to the wafer with a cleaning / drying medium in a supercritical state to obtain a mixed medium carrying the organic solvent; a depressurization step S2 of depressurizing the pressure of the mixed medium to a first pressure after the cleaning / drying step S1; an adsorption step S3 of heating the depressurized mixed medium to a first temperature after the depressurization step S2 to obtain a gaseous mixed medium, contacting the gaseous mixed medium with an organic solvent adsorbent in an adsorber, adsorbing and concentrating the organic solvent in the mixed medium by the organic solvent adsorbent, and separating it from the cleaning / drying medium; an adsorber switching step S4 of determining whether the organic solvent adsorbent in the first adsorber has reached an adsorption threshold, and if so, switching the adsorber in the adsorption step S3 from the first adsorber to the second adsorber; a desorption step S5 of heating the organic solvent adsorbent in the first adsorber to a second temperature after the adsorber switching step S4, discharging the organic solvent after desorbing from the organic solvent adsorbent in the first adsorber, and flowing it into an organic solvent collection port; and a purification step S6 of removing the organic solvent adsorbent pellets in the cleaning / drying medium separated in the adsorption step S3.

[0026] In addition, the "organic solvent adsorbent" in the present invention may be any adsorbent that highly selectively adsorbs organic solvents. Preferably, an activated carbon adsorbent or a molecular sieve adsorbent with a pore diameter in the range of 0.7 nm to 0.9 nm may be selected. For example, when the cleaning / drying medium is carbon dioxide and the organic solvent is isopropanol (IPA), a NaY molecular sieve may be selected as the organic solvent adsorbent. The NaY molecular sieve has a very high adsorption rate for gaseous organic solvents. As shown in Figure 2, when the gaseous mixed medium passes through the NaY molecular sieve, the concentration of isopropanol in the gaseous mixed medium rapidly decreases to almost zero, that is, most of the isopropanol is adsorbed and concentrated by the NaY molecular sieve without affecting the normal passage of carbon dioxide gas, realizing the separation of gaseous carbon dioxide and gaseous isopropanol.

[0027] The cleaning / drying medium in the supercritical state may be any medium that can dissolve the organic solvent on the wafer surface. Preferably, the cleaning / drying medium is carbon dioxide. The surface tension of supercritical carbon dioxide is 0, whereby the organic solvent can be dissolved well and the solvent residue on the wafer surface can be removed.

[0028] Here, the organic solvent can adsorb and desorb with the organic solvent adsorbent under specific adsorption environment parameters (an environment combining one or more elements such as specific pressure, temperature, atmosphere, etc.). In this embodiment, preferably, the progress of adsorption and desorption of the organic solvent is controlled by controlling the pressure and temperature. Specifically, the adsorption step S3 is performed at the first pressure and the first temperature, and the desorption step S5 is performed at the first pressure and the second temperature. The second temperature is higher than the first temperature. More preferably, the first pressure in the adsorption step S3 is 3 - 9 MPa, the first temperature is 30 - 90 °C, and the second temperature in the desorption step S5 is 150 - 300 °C. At the first pressure and the first temperature, carbon dioxide in the mixed medium is in a subcritical gas state, hardly compatible with the gaseous organic solvent, and is easily separated from the carbon dioxide. In this case, the organic solvent adsorbent has a high adsorption equilibrium concentration for the gaseous organic solvent, thereby making it easier to almost completely separate and adsorb the gaseous organic solvent in the mixed medium with the organic solvent adsorbent, reducing the loss of the cleaning / drying medium in the separation, and continuously separating and recovering a high-purity cleaning / drying medium. On the other hand, at the first pressure and the second temperature, the adsorption equilibrium concentration of the organic solvent adsorbent for the organic solvent decreases, and the desorption of the organic solvent from the organic solvent adsorbent is promoted. By only maintaining the pressure and adjusting the temperature, the separation of the cleaning / drying medium and the adsorption of the organic solvent in the mixed medium can be realized, and the separation and recovery process can be controlled more flexibly.

[0029] Figure 3 shows a supercritical wafer cleaning / drying medium recovery system applied to the above-mentioned supercritical wafer cleaning / drying medium recovery method according to this embodiment. As shown in Figure 3, the supercritical wafer cleaning / drying medium recovery system includes a flow path in which a cleaning / drying device 4, a first pressure reducing valve 5, an adsorption / desorption unit 100, and a purifier 9 are sequentially connected.

[0030] Here, the cleaning / drying device 4 is a specific location where the cleaning or drying of the wafer is completed. For example, the cleaning / drying device 4 is formed as a cleaning tank with openings at both ends, and a wafer mounting structure is provided inside the tank. The cleaning / drying medium in the supercritical state flows into the cleaning tank from one end opening of the cleaning tank, flows over the surface of the wafer mounted in the tank, and then may be configured to flow out from the other end of the cleaning tank.

[0031] The first pressure reducing valve 5 communicating with the outlet of the cleaning / drying device 4 is a component having the function of reducing the pressure of the flowing medium, and includes a pressure reducing valve that can control the outlet pressure to be constant in the conventional sense and a needle valve having a throttling function, but is not limited thereto.

[0032] The adsorption / desorption unit 100 communicates with the outlet of the first pressure reducing valve 5. The adsorption / desorption unit 100 includes an adsorber and a first heating device 6, and an organic solvent adsorbent is built into the adsorber. Preferably, the adsorption / desorption unit has a first adsorber 7 and a second adsorber 8 provided in parallel. The first heating device 6 is provided around the first adsorber 7 and the second adsorber 8, and is a component having the function of raising the temperature of the flowing medium, and includes devices for electric heating, fuel heating, and fluid heat exchange with a second medium, but is not limited thereto.

[0033] The purifier 9 communicates with the medium outlets of the first adsorber 7 and the second adsorber 8 of the adsorption / desorption unit 100, and is used to purify the gaseous cleaning / drying medium after desorption and filter the remaining organic solvent adsorbent.

[0034] Specifically, the cleaning / drying device executes the cleaning / drying step S1. The cleaning / drying medium in the supercritical state enters the cleaning / drying device 4 containing the wafer, cleans and removes the solvent on the wafer surface to obtain a mixed medium carrying the solvent. Next, the pressure reduction step S2 is executed. The mixed medium flowing out of the cleaning / drying device first enters the first pressure reducing valve 5. The cleaning / drying medium in the supercritical state is depressurized by the first pressure reducing valve 5 and then reaches a first pressure of 3 - 9 MPa at the outlet of the first pressure reducing valve 5. Thereafter, the adsorption step S3 is executed. The mixed medium at the first pressure is introduced into the adsorption / desorption unit 100, and the mixed medium is heated by the first heating device 6 in the adsorption / desorption unit 100 to reach a first temperature of 30 - 90 °C. The gaseous mixed medium at the first pressure and the first temperature is introduced into the first adsorber 7 and brought into contact with the organic solvent adsorbent. The organic solvent is adsorbed by the organic solvent adsorbent, and the cleaning / drying medium continuously passes through the organic solvent adsorbent. Finally, the purification step S6 is executed. The cleaning / drying medium flows into the purifier 9 from the medium outlet of the first adsorber 7 or the second adsorber 8, filters the cleaning / drying medium separated in the adsorption step S3, removes the deviated adsorbent pellets, and completes the separation of the high-purity cleaning / drying medium.

[0035] After continuously executing the adsorption step S3 for a certain period of time, the adsorber switching step S4 is executed to determine whether the organic solvent adsorbent in the first adsorber 7 has reached the adsorption threshold. The adsorption threshold here may be the adsorption saturation amount of the organic solvent adsorbent in the first adsorber 7, or the adsorption amount when the adsorption rate of the organic solvent adsorbent decreases, and is not limited here. If the organic solvent adsorbent in the first adsorber 7 has reached the adsorption threshold, the adsorber in the adsorption step S3 is switched to the second adsorber 8. While the second adsorber 8 executes the adsorption step S3, the first adsorber 7 executes the desorption step S5, and the temperature of the first adsorber 7 is raised to a second temperature of 150 - 300 °C using the first heating device 6. At this time, the adsorption equilibrium concentration of the organic solvent adsorbent in the first adsorber 7 decreases, and after the organic solvent is desorbed, it flows out from the organic solvent collection port 13 through the solvent outlet of the first adsorber 7.

[0036] As described above, throughout the adsorption process, the cleaning / drying medium is not blocked or concentrated, and the organic solvent adsorbent has high selectivity for the organic solvent, and can adsorb almost all of the organic solvent in the mixed medium. Therefore, while ensuring high purity of the separation of the cleaning / drying medium, the loss in the separation of the cleaning / drying medium is reduced.

[0037] In addition, due to the adsorption of the organic solvent by the organic solvent adsorbent, and further by switching between the first adsorber 7 and the second adsorber 8 in the adsorber switching step S4, adsorption and desorption can be carried out simultaneously in the first adsorber 7 and the second adsorber 8, improving the separation efficiency of the cleaning / drying medium, maintaining a continuous outflow of high-purity cleaning / drying medium, and realizing a continuous recovery of high-purity cleaning / drying medium.

[0038] Second Embodiment Preferably, FIG. 4 shows a flowchart of another supercritical wafer cleaning / drying medium recovery method according to this embodiment. As shown in FIG. 4, the supercritical wafer cleaning / drying medium recovery method further includes a gas supply step S7 of obtaining a supercritical cleaning / drying medium by pressurizing and heating the gaseous cleaning / drying medium separated in the adsorption step S3 and / or an external medium supplied from an external gas source, and supplying the supercritical cleaning / drying medium used in the cleaning / drying step S1, and a pressure adjustment step S8 of pressurizing and transporting the gaseous cleaning / drying medium obtained in the adsorption step S3, and adjusting the pressure of the pressurized cleaning / drying medium to be the same as the pressure of the external medium before the gas supply step S7.

[0039] Accordingly, FIG. 5 is a schematic structural diagram of a preferred supercritical wafer cleaning / drying medium recovery system. As shown in FIG. 5, the supercritical wafer cleaning / drying medium recovery system further includes a gas supply unit 200, an external gas source 1, and a pressure regulating device (including a compressor 10 and a second pressure reducing valve 11 connected in sequence). The gas supply unit 200 communicates with the medium outlet of the adsorption / desorption unit 100 and the inlet of the cleaning / drying device 4, pressurizes and heats the cleaning / drying medium flowing out from the medium outlet of the adsorption / desorption unit 100 to obtain a supercritical state cleaning / drying medium, and supplies it for use in the cleaning / drying device 4. The outlet of the external gas source 1 communicates with the inlet of the gas supply unit 200. The compressor 10 in the pressure regulating device communicates with the outlet of the adsorption / desorption unit, and the second pressure reducing valve 11 communicates with the inlet of the external gas source 1.

[0040] Here, as shown in FIG. 5, the gas supply unit 200 may be a unit combining a booster pump 2 and a second heating device 3. The booster pump 2 is a device capable of boosting and outputting a fluid working medium, and its form includes, but is not limited to, a positive displacement pump and a reciprocating pump.

[0041] The external gas source 1 is a gas source in a broad sense, and can supply a gas or liquid working medium to the supercritical wafer cleaning / drying medium recovery system. In some embodiments, the external gas source 1 may be a gas supply passage formed by connecting a gas cylinder group and a chiller, or in other embodiments, the external gas source 1 may be a gas supply system composed of a storage tank and its attached cooling device. The pressure regulating device is a unit combining a compressor 10 and a second pressure reducing valve 11. The compressor 10 is a device capable of realizing the pressure boost of a gaseous medium, and its form includes, but is not limited to, a centrifugal compressor and an axial flow compressor. The outlet pressure of the compressor 10 is slightly higher than the starting pressure of the second pressure reducing valve 11, and the outlet pressure of the second pressure reducing valve 11 is the same as the pressure of the external medium supplied from the external gas source 1.

[0042] In this embodiment, by replenishing the medium loss in the system with the external gas source 1, the continuous circulating operation of the system is maintained. Furthermore, the acceleration of the working medium is promoted by the pressure increase by the compressor 10, and the backward flow is facilitated. The second pressure reducing valve 11 controls the outlet pressure of the pressure regulating device to match the outlet pressure of the external gas source 1, so that the medium at the outlet of the pressure regulating device is mixed with the medium of the external gas source at the same pressure and then supplied to the gas supply unit 200, and the stable and safe operation of the system can be maintained.

[0043] Specifically, starting from the external gas source 1, the gas supply step S7 is executed, and the cleaning / drying medium is supplied from the external gas source 1 into the system. The cleaning / drying medium is pressurized by the booster pump 2 and heated by the second heating device 3 to reach a supercritical state of high temperature and high pressure. Then, steps S1 - S6 are sequentially executed in the same procedure as in the first embodiment. Subsequently, the pressure adjustment step S8 is executed. The high-purity gaseous cleaning / drying medium flowing out from the purifier 9 flows through the compressor 10 and the second pressure reducing valve 11. The flow of the low-pressure gaseous medium is gentle, but after being pressurized by the compressor, the rapid flow of the medium is promoted. In the second pressure reducing valve 11, the pressure is reduced to the same pressure as that of the external gas source 1, the medium stably enters the external gas source 1, is mixed with the external medium supplied from the external gas source 1, and then the gas supply step S7 is cyclically executed again.

[0044] In another preferred embodiment of the present invention, the supercritical wafer cleaning / drying medium recovery system further includes a blowdown valve 12 provided in any pipeline of the system for blowdown of the medium in special or emergency situations.

[0045] The above are only preferred embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention are all included in the protection scope of the present invention.

Explanation of Reference Numerals

[0046] 100 Adsorption / Desorption Unit 200 Gas supply unit 1 External gas source 2 Booster pump 3 Second heating device 4 Cleaning / drying device 5 First pressure reducing valve 6 First heating device 7 First adsorber 8 Second adsorber 9 Purifier 10 Compressor 11 Second pressure reducing valve 12 Blowdown valve 13 Organic solvent collection port.

Claims

1. 1. A supercritical wafer cleaning / drying medium recovery method comprising: a cleaning / drying step of dissolving and removing the organic solvent adhering to the wafer by a cleaning / drying medium in a supercritical state to obtain a mixed medium carrying the organic solvent; a depressurization step of reducing the pressure of the mixed medium to a first pressure after the washing / drying step; an adsorption step in which, after the depressurization step, the depressurized mixed medium is heated to a first temperature to obtain a gaseous mixed medium, the gaseous mixed medium is contacted with an organic solvent adsorbent in an adsorber, the organic solvent in the mixed medium is adsorbed and concentrated by the organic solvent adsorbent, and the mixed medium is separated from the washing / drying medium; 2. A method for recovering a supercritical wafer cleaning / drying medium comprising:

2. an adsorber switching step of determining whether the organic solvent adsorbent in a first adsorber has reached an adsorption threshold, and if so, switching the adsorber in the adsorption step from the first adsorber to a second adsorber; a desorption step in which, after the adsorber switching step, the organic solvent adsorbent in the first adsorber is heated to a second temperature, and the organic solvent is desorbed from the organic solvent adsorbent in the first adsorber, and then discharged from the first adsorber and flows into an organic solvent collection port; 2. The method of claim 1, further comprising:

3. 2. The method of claim 1, further comprising a purification step of removing organic solvent adsorbent pellets in the cleaning / drying medium separated in the adsorption step.

4. 3. The method for recovering a supercritical wafer cleaning / drying medium according to claim 2, wherein the organic solvent adsorbent is an activated carbon adsorbent or a molecular sieve adsorbent having a pore size in the range of 0.7 nm-0.9 nm, and the cleaning / drying medium is carbon dioxide.

5. 5. The method for recovering a supercritical wafer cleaning / drying medium according to claim 4, wherein the first pressure is 3-9 MPa, the first temperature is 30-90° C., and the second temperature is 150-300° C.

6. a gas supply step of supplying the cleaning / drying medium in a supercritical state to be used in the cleaning / drying step by pressurizing and heating the gaseous cleaning / drying medium separated in the adsorption step and / or an external medium supplied from an external gas source to obtain the cleaning / drying medium in a supercritical state; a pressure adjusting step of pressurizing and transporting the gaseous cleaning / drying medium obtained in the adsorption step, and adjusting the pressure of the pressurized cleaning / drying medium to be the same as the pressure of the external medium before the gas supply step; 2. The method of claim 1, further comprising:

7. 1. A supercritical wafer cleaning / drying media recovery system comprising: a cleaning / drying device having a wafer housed therein, for dissolving and removing an organic solvent adhering to the wafer with a cleaning / drying medium in a supercritical state to obtain a mixed medium carrying the organic solvent; a first pressure reducing valve in communication with an outlet of the cleaning / drying appliance for reducing the pressure of the mixed medium to a first pressure; and an adsorption / desorption unit having the organic solvent adsorbent built therein and communicating with an outlet of the first pressure reducing valve, the adsorption / desorption unit having a first heating device for heating the mixed medium that has entered the adsorption / desorption unit to a first temperature to obtain a gaseous mixed medium, the gaseous mixed medium coming into contact with the organic solvent adsorbent, the organic solvent in the mixed medium being adsorbed by the organic solvent adsorbent and concentrated, and separated from the cleaning / drying medium.

8. the adsorption / desorption unit includes a plurality of adsorbers each having the organic solvent adsorbent built therein and the first heating device; a plurality of the adsorbents are provided in parallel, inlets of the plurality of the adsorbents are connected to the outlet of the first pressure reducing valve, and solvent outlets of the plurality of the adsorbents are connected to an organic solvent collection port; 8. The supercritical wafer cleaning / drying medium recovery system of claim 7, wherein the first heating device is provided around the plurality of adsorbents and is used to control the temperatures of the plurality of adsorbents to a first temperature or a second temperature higher than the first temperature.

9. 10. The supercritical wafer cleaning / drying medium recovery system of claim 8, further comprising a purifier communicating with the media outlets of the plurality of adsorbers for removing organic solvent adsorbent pellets in the cleaning / drying medium.

10. a gas supply unit communicating with a medium outlet of the adsorption / desorption unit and an inlet of a cleaning / drying device, the gas supply unit including a booster pump and a second heating device; an external gas source having an outlet communicating with an inlet of the gas supply unit; 10. The supercritical wafer cleaning / drying medium recovery system of claim 9, further comprising: a pressure regulating device having a compressor and a second pressure reducing valve, the pressure regulating device being connected to the medium outlet of the adsorption / desorption unit and the inlet of the external gas source ...

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