Supercritical wafer cleaning / drying medium recovery method and system

Abstract

The present invention provides a supercritical wafer cleaning / drying medium recovery method and system, capable of separating, recovering, and recycling supercritical medium. The method includes the following steps: a cleaning / drying step, in which a supercritical medium is used to dissolve and remove the solvent on the wafer; a separation step, in which the supercritical medium obtained in the cleaning / drying step is converted into a gaseous medium, and the gaseous medium is separated from the solvent by gas-liquid separation; and a gas supply step, in which the gaseous medium is pressurized and heated to obtain a supercritical medium, which is then supplied to the supercritical medium used in the cleaning / drying step.

Description

Technical Field

[0001] The present invention relates to the field of wafer processing technology, and in particular to a supercritical wafer cleaning / drying medium recovery method and system. Background Art

[0002] Semiconductor wafers are a crucial material in the semiconductor industry, and their surface cleanliness is highly demanding. Cleaning and drying the wafer surface are essential processes in semiconductor wafer processing to ensure effective removal of solvents and maintain a clean surface. Certain supercritical media possess zero surface tension, allowing them to penetrate more easily into the pores of the wafer surface, achieving efficient solvent removal.

[0003] Existing supercritical medium cleaning and drying processes usually use supercritical medium as a "disposable" consumable. However, the consumption of supercritical medium during the cleaning and drying process is large, resulting in excessively high costs for wafer cleaning / drying. Therefore, the field urgently needs an effective supercritical wafer cleaning / drying medium recovery process to reduce the cleaning and drying costs of semiconductor wafers. Summary of the Invention

[0004] In response to the above problems, the present invention provides a supercritical wafer cleaning / drying medium recovery method and system, which can realize the separation, recovery and recycling of supercritical medium.

[0005] A first aspect of the present invention provides a method for recovering a supercritical wafer cleaning / drying medium, comprising the following steps:

[0006] In the cleaning / drying step, a supercritical medium is used to dissolve and remove the solvent on the wafer; in the separation step, the supercritical medium obtained in the cleaning / drying step is converted into a gaseous medium, and the gaseous medium and the solvent are separated into gas and liquid; in the gas supply step, the gaseous medium is pressurized and heated to obtain a supercritical medium to supply the supercritical medium used in the cleaning / drying step.

[0007] According to this technical solution, the solvent used in the wafer processing process is generally an organic solvent that is relatively soluble in the supercritical medium but is almost insoluble in the gaseous medium. Therefore, after the supercritical medium carrying the solvent after cleaning / drying is converted into a gaseous medium in the separation step, the solvent originally dissolved in the supercritical medium will precipitate as a liquid. The liquid solvent will completely separate from the gaseous medium and settle during the separation step. As a result, the separated gaseous medium is highly pure and can be recovered after being pressurized and heated in the gas supply step, thus achieving the recycling of the wafer cleaning / drying medium.

[0008] It should be noted that the "solvent" in the present invention refers to the impure liquid mainly composed of organic solvents attached to the surface of the wafer, which may be mixed with organic matter, impurity particles, etc. generated during the wafer processing process, and does not specifically refer to a pure solvent.

[0009] As a preferred technical solution, the separation step includes the following sub-steps: a decompression step, reducing the pressure of the mixture of the supercritical medium and the solvent after the cleaning / drying step to obtain a mixed solution; a heating step, heating the mixed solution to obtain a gaseous medium and a liquid solvent; and a gas-liquid separation step, separating the gaseous medium from the liquid solvent.

[0010] According to this technical solution, after the supercritical medium carries out the solvent in the cleaning / drying step, it is first decompressed to a subcritical state in a decompression step. However, due to the throttling and cooling effect, the temperature of the cleaning / drying medium will decrease after the decompression step, and the cleaning / drying medium will be liquefied. At this time, the mixture of the solvent and the cleaning / drying medium is in an immiscible liquid state, and the liquid-liquid separation is difficult and difficult to separate completely. Therefore, a heating step is performed after the decompression step to heat the mixed solution so that the cleaning / drying medium absorbs heat and vaporizes. At this time, the solvent is still in a high-density liquid state and will be dispersed in the gaseous medium in the form of droplets or mist. The gaseous medium can be completely separated from the solvent through the precipitation of the liquid solvent in the gas-liquid separation step, thereby ensuring the purity of the medium after multiple cycles.

[0011] As a preferred technical solution, the supercritical medium is supercritical carbon dioxide, the pressure of the mixed solution in the decompression step is 1-5 MPa, the temperature is less than 20°C, and the temperature of the gaseous carbon dioxide in the heating step is 0-30°C.

[0012] According to this technical solution, the surface tension of supercritical carbon dioxide is 0, and it can quickly dissolve organic matter and remove residues by gasification without leaving any water marks. When the pressure of supercritical carbon dioxide is reduced from the critical state to 1-5MPa, carbon dioxide is in a subcritical state. At this time, the solvent and carbon dioxide are immiscible. However, due to the throttling and cooling effect, the temperature of carbon dioxide is reduced to -50℃ to 20℃, and liquid carbon dioxide and solvent will mix to form an immiscible mixed solution. After that, the heating step is performed, and the liquid carbon dioxide is completely gasified at a temperature of 0-30℃, thereby achieving complete separation of the medium and the solvent.

[0013] As a preferred technical solution, in the gas supply step, the gaseous medium and / or the external medium supplied by the external gas source is pressurized and heated to obtain a supercritical medium.

[0014] According to this technical solution, some medium will remain on the wafer surface, resulting in a certain amount of medium loss during the cycle. Therefore, an external gas source is used to mix the gaseous medium separated in the separation step to supply a mixed gas. This can compensate for the medium loss during the cycle and maintain the amount of supercritical medium used for cleaning / drying in the cleaning / drying steps after multiple cycles. The external medium stored in the external gas source can be a gaseous or liquid medium.

[0015] As a preferred technical solution, after the separation step and before the gas supply step, the method further includes:

[0016] The pressure adjustment step is to pressurize and transport the gaseous medium obtained in the separation step, and to adjust the pressure of the pressurized gaseous medium to be the same as the pressure of the external medium before the gas supply step.

[0017] According to this technical solution, since the cleaning / drying medium after the separation step is in a low-pressure state and flows slowly, the flow rate of the medium can be pushed by pressurizing it in the pressure adjustment step, and then the pressure is adjusted again to make the pressure before executing the gas supply step the same as the pressure of the external gas source, so that the pressure of the gaseous medium entering the gas supply step is stable.

[0018] The second aspect of the present invention also provides a supercritical wafer cleaning / drying medium recovery system, which includes: a cleaning / drying unit with a built-in wafer, which is used to use a supercritical medium to dissolve and remove the solvent attached to the wafer; a separation unit connected to the outlet of the cleaning / drying unit, which is used to convert the supercritical medium flowing out of the cleaning / drying unit into a gaseous medium, and perform gas-liquid separation between the gaseous medium and the solvent; and a gas supply unit connected to the outlet of the separation unit and the inlet of the cleaning / drying unit, which is used to pressurize and heat the gaseous medium flowing out of the separation unit to obtain a supercritical medium to supply the supercritical medium to the cleaning / drying unit.

[0019] According to this technical solution, the cleaning / drying medium circulates in the supercritical wafer cleaning / drying medium recovery system. Starting from the cleaning / drying unit, the cleaning / drying medium flows in the cleaning / drying unit and takes away the solvent on the wafer surface. The cleaning / drying medium carrying the solvent is converted into a mixture of gaseous medium and liquid solvent in the separation unit, and the gaseous medium is recovered by gas-liquid separation. The separated gaseous medium flows into the gas supply unit, and after being heated and pressurized to a supercritical state, it is injected into the cleaning / drying unit for the next cycle, thereby realizing continuous cleaning of the wafer and recycling of the cleaning / drying medium.

[0020] As a preferred technical solution, the separation unit includes: a first pressure-reducing valve connected to the outlet of the cleaning / drying unit, used to reduce the pressure of the mixture flowing out of the cleaning / drying unit to obtain a mixed solution; a first heating device connected to the outlet of the first pressure-reducing valve, used to heat the mixed solution flowing out of the first pressure-reducing valve to obtain a gaseous medium and a liquid solvent; a gas-liquid separation device connected to the outlet of the first heating device and the inlet of the gas supply unit, used to perform gas-liquid separation on the gaseous medium and the liquid solvent flowing out of the first heating device.

[0021] According to this technical solution, the supercritical medium in the mixture flowing out of the cleaning / drying unit is converted into a gaseous medium through the first pressure reducing valve and the first heating device, thereby realizing the phase separation of the medium and the solvent, and then the complete separation of the medium and the solvent can be simply achieved through the gas-liquid separation device.

[0022] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery system further includes an external gas source, the outlet of the external gas source being connected to the inlet of the gas supply unit.

[0023] According to this technical solution, the medium loss in the system is supplemented by an external gas source, thereby maintaining the continuous operation of the system.

[0024] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery system also includes a pressure adjustment device connecting the outlet of the separation unit and the inlet of the external gas source. The pressure adjustment device includes a compressor and a second pressure reducing valve connected in sequence along the fluid flow direction.

[0025] According to this technical solution, since the gas medium after separation is in a low-pressure state and flows slowly, the pressure increase by the compressor can push the working medium to accelerate its backward flow. The second pressure reducing valve can control the outlet pressure of the pressure regulating device to be equal to the outlet pressure of the external gas source, so that the medium at the outlet of the pressure regulating device can be mixed with the medium of the external gas source at equal pressure and then enter the gas supply unit, maintaining stable and safe operation of the system.

[0026] As a preferred technical solution, the air supply unit includes a booster pump and a second heating device which are sequentially connected along the fluid flow direction.

[0027] According to this technical solution, the combined action of the booster pump and the second heating device can enable the medium to quickly reach a supercritical state, thereby achieving circulation of the medium in the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of a supercritical wafer cleaning / drying medium recovery method provided by an embodiment of the present invention;

[0029] Figure 2Schematic diagram of a supercritical wafer cleaning / drying medium recovery system applicable to an embodiment of the present invention;

[0030] Figure 3 is a flow chart of a more preferred supercritical wafer cleaning / drying medium recovery method provided by an embodiment of the present invention;

[0031] Figure 4 It is a structural schematic diagram of a supercritical wafer cleaning / drying medium recovery system provided in an embodiment of the present invention.

[0032] Description of the accompanying drawings:

[0033] 100, 4-cleaning / drying unit; 200-separation unit; 300-air supply unit; 400-pressure adjustment device; 1-external air source; 2-boosting pump; 3-second heating device; 5-first pressure reducing valve; 6-first heating device; 7-gas-liquid separation device; 8-compressor; 9-second pressure reducing valve; 10-vent; 11-solvent collection port. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail with reference to the following specific embodiments and accompanying drawings. The implementation of the present invention is not limited to the following embodiments, and various modifications, variations, combinations, and improvements based on the technical concept of the present invention adopted within the knowledge of those skilled in the art fall within the scope of protection of the present invention.

[0035] First embodiment

[0036] Figure 1 This is a flow chart of a supercritical wafer cleaning / drying medium recovery method provided by the first embodiment of the present invention. Figure 1 As shown, the supercritical wafer cleaning / drying medium recovery method provided in this embodiment includes the following steps:

[0037] In the cleaning / drying step S1, a supercritical medium is used to dissolve and remove the solvent on the wafer; in the separation step S2, the supercritical medium obtained in the cleaning / drying step is converted into a gaseous medium, and the gaseous medium and the solvent are separated by gas-liquid separation; in the gas supply step S3, the gaseous medium is pressurized and heated to obtain a supercritical medium to supply the supercritical medium used in the cleaning / drying step S1.

[0038] It should be noted that in this embodiment, "solvent" refers to the impure liquid mainly composed of organic solvents attached to the surface of the wafer, which may be mixed with organic matter, impurity particles, etc. generated during the wafer processing process, and does not specifically refer to a pure solvent.

[0039] Specifically, the supercritical wafer cleaning / drying medium recovery method provided in this embodiment is a medium circulation process that can continuously clean wafers. Correspondingly, the supercritical wafer cleaning / drying medium recovery system provided in this embodiment that is suitable for the supercritical wafer cleaning / drying medium recovery method is also a closed-loop circulation system. Figure 2 FIG. 1 shows a schematic structural diagram of a supercritical wafer cleaning / drying medium recovery system applicable to this embodiment, as shown in FIG. Figure 2 As shown, the system includes a circulation loop in which a cleaning / drying unit 100, a separation unit 200 and an air supply unit 300 are connected in sequence.

[0040] Among them, the cleaning / drying unit 100 has a built-in wafer, which is used to use a supercritical medium to dissolve and remove the solvent attached to the wafer; the separation unit 200 is connected to the outlet of the cleaning / drying unit 100, and is used to convert the supercritical medium flowing out of the cleaning / drying unit 100 into a gaseous medium, and perform gas-liquid separation between the gaseous medium and the solvent; the gas supply unit 300 is connected to the outlet of the separation unit 200 and the inlet of the cleaning / drying unit 100, and is used to pressurize and heat the medium flowing out of the separation unit 200 to obtain a supercritical medium for supplying to the cleaning / drying unit 100.

[0041] Combine Figure 1 and Figure 2 From the perspective of the above, the cleaning / drying medium circulates in the supercritical wafer cleaning / drying medium recovery system. Starting from the cleaning / drying unit 100, the cleaning / drying medium flows in the cleaning / drying unit 100 and takes away the solvent on the wafer surface. The cleaning / drying medium carrying the solvent is converted into a mixture of gaseous medium and liquid solvent in the separation unit 200, and the gaseous medium is recovered by gas-liquid separation. The separated gaseous medium flows into the gas supply unit 300, and after being heated and pressurized to a supercritical state, it is injected into the cleaning / drying unit 100 for the next cycle.

[0042] In this embodiment, the solvent used in the wafer processing process is generally an organic solvent that is relatively soluble in the supercritical medium, but is almost insoluble in the gaseous medium. Therefore, after the supercritical medium carrying the solvent after cleaning / drying is converted into a gaseous medium in separation step S2, the solvent originally dissolved in the supercritical medium will precipitate as a liquid. The liquid solvent will completely separate from the gaseous medium and settle in separation step S2. As a result, the separated gaseous medium has high purity and can be recovered after pressurization and heating in gas supply step S3, realizing the recycling of the wafer cleaning / drying medium.

[0043] Figure 3 is a flow chart of a more preferred supercritical wafer cleaning / drying medium recovery method provided by this embodiment, such as Figure 3As shown, the separation step S2 includes the following sub-steps: a decompression step S21, reducing the pressure of the mixture of the supercritical medium and the solvent after the cleaning / drying step to obtain a mixed solution; a heating step S22, heating the mixed solution to obtain a gaseous medium and a liquid solvent; and a gas-liquid separation step S23, performing gas-liquid separation on the gaseous medium and the liquid solvent.

[0044] The cleaning medium in this embodiment can be any fluid medium capable of achieving supercritical cleaning. Preferably, the supercritical medium is supercritical carbon dioxide. Supercritical carbon dioxide has a surface tension of zero and can rapidly dissolve organic matter and remove residues by vaporization without leaving any water marks.

[0045] More preferably, the pressure of the mixed solution in the decompression step is 1-5 MPa, the temperature is less than 20° C., and the temperature of the gaseous carbon dioxide in the heating step S32 is 0-30° C. When the pressure of supercritical carbon dioxide is reduced from the critical state to 1-5 MPa, the carbon dioxide is in a subcritical state. At this time, the solvent and carbon dioxide are immiscible. However, due to the throttling and cooling effect, the temperature of the carbon dioxide is reduced to -50°C to 20°C. The lower the pressure of the carbon dioxide after decompression, the lower the temperature. For example, when the supercritical carbon dioxide is decompressed to 1 MPa, the temperature can be as low as -50°C. At this time, the temperature of the carbon dioxide is extremely low and is in a liquid state. Conversely, when the pressure of the carbon dioxide after decompression is higher, the temperature is also higher. For example, when the supercritical carbon dioxide is decompressed to 5 MPa, the temperature is around 10-20°C. However, since the carbon dioxide pressure is relatively high at this time, it is also in a liquid state or a gas-liquid mixed state. The liquid carbon dioxide and the solvent are mixed to form an immiscible mixed solution. Then, in the heating step S32, the liquid carbon dioxide is heated to 0-30°C. For carbon dioxide with a lower pressure after decompression, it only needs to be heated to a lower temperature to be completely gasified. For carbon dioxide with a higher pressure, it needs to be heated to around 30°C to be completely gasified.

[0046] As a preferred example, in the separation step S2, the supercritical carbon dioxide carrying the solvent is first subjected to a decompression step S21, and the pressure of the supercritical carbon dioxide is reduced to 1-5 MPa, entering a subcritical state, and due to the throttling and cooling effect, the temperature of the subcritical carbon dioxide after the decompression step S21 is lower than 20°C. At this time, the liquid carbon dioxide and the solvent are in an immiscible liquid mixed state, and the liquid-liquid separation is difficult and difficult to separate completely, so a heating step S22 is performed after the decompression step S21 to heat the mixed solution to 0-30°C to completely vaporize the cleaning / drying medium. At this time, the solvent is still in a high-density liquid state and will be dispersed in the gaseous medium in the form of droplets or mist; finally, in the gas-liquid separation step S23, the gaseous carbon dioxide and the precipitated solvent are subjected to gas-liquid separation, thereby achieving complete separation of carbon dioxide and solvent, and ensuring the purity of the carbon dioxide medium in multiple cycles.

[0047] Since some of the medium will remain on the wafer surface during the cleaning / drying step S1, a certain amount of medium loss will occur during each cycle. To address this, preferably, during the gas supply step S3, the gaseous medium and / or the external medium supplied by the external gas source are pressurized and heated to obtain a supercritical medium. This allows the use of a mixed gas supply from the external gas source and the gaseous medium separated in the separation step S2 to compensate for the medium loss during the cycle and maintain the amount of supercritical medium used for cleaning / drying in the cleaning / drying step S1 after multiple cycles.

[0048] The external medium stored in the external gas source may be a gaseous medium or a liquid medium. Preferably, the external medium in the external gas source is a liquid medium, so that more medium can be stored in the same volume, and the liquid medium has a higher pressure, which is more conducive to conversion into a supercritical medium in the subsequent gas supply step S3.

[0049] It is worth mentioning that since the cleaning / drying medium after separation step S2 is at a low pressure and flows slowly, and to ensure that the cleaning / drying medium can be mixed at the same pressure before gas supply step S3, preferably, after separation step S2 and before gas supply step S3, a pressure adjustment step S30 is further included to pressurize and transport the gaseous medium obtained in separation step S2, and to adjust the pressure of the pressurized gaseous medium to the same pressure as the external medium before gas supply step S3. Pressure adjustment step S30 can promote the flow rate of the medium, and at the same time, the pressure of S3 before gas supply step S3 is the same as the pressure of the external gas source, so that the pressure of the medium entering gas supply step S3 is stable.

[0050] Second embodiment

[0051] A more specific supercritical wafer cleaning / drying medium recovery system is provided in the second embodiment of the present invention, and based on the supercritical wafer cleaning / drying medium recovery system, the operation process of the supercritical wafer cleaning / drying medium recovery method in the first embodiment in the system is further explained.

[0052] Figure 4 Schematic diagram of the structure of the supercritical wafer cleaning / drying medium recovery system provided in this embodiment. Figure 4 As shown, the system includes a circulation loop formed by connecting an external gas source 1, a booster pump 2, a second heating device 3, a cleaning / drying unit 4, a first pressure reducing valve 5, a first heating device 6, a gas-liquid separation device 7, a compressor 8, and a second pressure reducing valve 9 in sequence.

[0053] Among them, the external gas source 1 refers to a gas source in a broad sense, which can input gaseous or liquid working medium into the supercritical wafer cleaning / drying medium recovery system. In some embodiments, the external gas source 1 can be a gas supply path formed by connecting a gas cylinder group and a chiller, or, in other embodiments, the external gas source 1 can also be a gas supply system composed of a storage tank and its auxiliary cooling equipment.

[0054] The combined unit of the booster pump 2 and the second heating device 3 is an air supply unit 300. The booster pump 2 is a device that can pressurize and output the liquid working medium, and its form includes but is not limited to a volumetric pump and a reciprocating pump. The second heating device 3 is a device that heats the flowing working medium, and its form includes but is not limited to electric heating and fuel heating.

[0055] The cleaning / drying unit 4 is a specific place where wafer cleaning or drying is completed. For example, the cleaning / drying unit 4 can be formed as a cleaning tank with openings at both ends, and a wafer mounting structure is provided in the tank. The cleaning / drying unit can flow into the cleaning tank from one end opening of the cleaning tank, flow through the surface of the wafer installed in the tank, and then flow out from the other end of the cleaning tank.

[0056] The combined unit of the first pressure-reducing valve 5, the first heating device 6, and the gas-liquid separation device 7 forms the separation unit 200. The first pressure-reducing valve 5 is a device that converts a fluid from high pressure to low pressure. Its forms include, but are not limited to, traditional pressure-reducing valves and, in a broader sense, pressure-reducing devices such as throttle valves. The outlet pressure of the first pressure-reducing valve 5 is 1 to 5 MPa; the outlet temperature of the first heating device 6 is 0 to 30°C. The gas-liquid separation device 7 is a device capable of achieving gas-liquid phase separation. Its forms include, but are not limited to, centrifugal gas-liquid separators, gravity sedimentation gas-liquid separators, and filter-type gas-liquid separators.

[0057] The combination of the compressor 8 and the second pressure reducing valve 9 is a pressure regulating device 400, wherein the compressor 8 refers to a device capable of increasing the pressure of the gaseous medium, and its form includes but is not limited to a centrifugal compressor and an axial flow compressor; the outlet pressure of the second pressure reducing valve 9 is the same as the pressure of the external gas source 1.

[0058] Specifically, starting from the external gas source 1, the gas supply step S3 is executed, the external gas source 1 supplies the cleaning / drying medium 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 high temperature and high pressure supercritical state.

[0059] Afterwards, the supercritical medium flows into the cleaning / drying unit 4 to perform the cleaning / drying step S1 . The supercritical medium entering the cleaning / drying unit 4 with the wafer built therein cleans and removes the solvent on the surface of the wafer.

[0060] Next, the supercritical medium carrying the solvent flowing out of the cleaning / drying unit 4 first enters the first pressure reducing valve 5 and performs a pressure reducing step S21. The supercritical medium is reduced to 1-5 MPa by the first pressure reducing valve 5. At the same time, depending on the degree of pressure reduction, the temperature of the cleaning / drying medium is reduced to -50°C to 20°C. The supercritical medium is converted into a liquid medium and mixed with the liquid solvent to form a mixed solution. After the mixed solution flows out of the outlet of the first pressure reducing valve 5, it enters the first heating device 6 and performs a heating step S22. The liquid medium is heated to 0-30°C in the first heating device 6 and completely vaporized. At this time, the solvent carried inside the medium is still in a high-density liquid state and will be dispersed in the gaseous cleaning / drying medium in the form of droplets or mist. Then, a gas-liquid separation step S23 is performed. The gas-liquid mixture can be separated into a low-density and lightweight gaseous cleaning / drying medium in the upper part of the gas-liquid separation device 7, while the heavy liquid solvent will settle in the lower part of the gas-liquid separation device 7 and be discharged from the system.

[0061] Finally, the gaseous medium separated by the gas-liquid separation device 7 flows through the compressor 8 and the second pressure reducing valve 9, and the pressure adjustment step S3 is performed. The low-pressure gaseous medium flows slowly, but the pressure increase by the compressor 8 promotes the medium to flow rapidly. The outlet pressure of the second pressure reducing valve 9 is the same as the pressure of the external gas source 1, allowing the medium to stably enter the external gas source 1, mix with the external medium provided by the external gas source 1, and then perform the gas supply step S3 again.

[0062] In a preferred embodiment, the supercritical wafer cleaning / drying medium recovery system also includes a vent port 10 and a solvent collection port 11. The vent port 10 can be set on any section of the system pipeline for venting the medium under special or emergency conditions; the solvent collection port 11 is set at the outlet end of the gas-liquid separation device 7 for recovering the solvent after separation.

[0063] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A supercritical wafer cleaning / drying medium recovery method, characterized in that: The following steps are involved: A cleaning / drying step uses a supercritical medium to dissolve and remove the solvent attached to the wafer, wherein the supercritical medium is supercritical carbon dioxide and the solvent is an organic solvent that is easily soluble in the supercritical medium. a decompression step of reducing the pressure of the mixture of the supercritical medium and the solvent after the cleaning / drying step to obtain a mixed solution; wherein the pressure of the mixed solution in the decompression step is 1 to 5 MPa, the temperature is less than 20° C., and the carbon dioxide is in a subcritical state, at which point the carbon dioxide and the solvent are immiscible; a heating step of heating the mixed solution to obtain a gaseous medium and a liquid solvent, wherein the temperature of the gaseous medium in the heating step is 0 to 30° C.; a gas-liquid separation step, performing gas-liquid separation on the gaseous medium and the liquid solvent; a gas supply step of pressurizing and heating the gaseous medium obtained in the gas-liquid separation step and / or the external medium supplied from an external gas source to obtain the supercritical medium for use in the cleaning / drying step; A pressure adjustment step is to pressurize and transport the gaseous medium obtained in the gas-liquid separation step, and to adjust the pressure of the pressurized gaseous medium to be the same as the pressure of the external medium before the gas supply step.

2. A supercritical wafer cleaning / drying medium recovery system for executing the supercritical wafer cleaning / drying medium recovery method according to claim 1, characterized in that: include: A cleaning / drying unit, having a wafer built therein, for dissolving and removing the solvent attached to the wafer using a supercritical medium; a separation unit, connected to the outlet of the cleaning / drying unit, for converting the supercritical medium flowing out of the cleaning / drying unit into a gaseous medium and performing gas-liquid separation between the gaseous medium and the solvent; The separation unit comprises: a first pressure reducing valve, connected to the outlet of the cleaning / drying unit, for reducing the pressure of the mixture flowing out of the cleaning / drying unit to obtain a mixed solution; a first heating device, connected to the outlet of the first pressure reducing valve, for heating the mixed solution flowing out of the first pressure reducing valve to obtain the gaseous medium and the liquid solvent; a gas-liquid separation device, connected to the outlet of the first heating device, for performing gas-liquid separation on the gaseous medium and the liquid solvent flowing out of the first heating device; an air supply unit, the air supply unit being connected to the inlet of the cleaning / drying unit and being used for pressurizing and heating the gaseous medium to obtain the supercritical medium for supplying the cleaning / drying unit; an external air source, wherein an outlet of the external air source is connected to an inlet of the air supply unit; A pressure regulating device is connected to the gaseous medium outlet of the gas-liquid separation device and the inlet of the external gas source. The pressure regulating device includes a compressor and a second pressure reducing valve connected in sequence along the fluid flow direction.

3. The supercritical wafer cleaning / drying medium recovery system according to claim 2, wherein: The air supply unit includes a booster pump and a second heating device which are sequentially connected along a fluid flow direction.

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