Supercritical wafer cleaning / drying medium recovery method and system

Abstract

The invention relates to the technical field of wafer processing, provides a supercritical wafer cleaning / drying medium recovery method and system, and can realize continuous recovery of a high-purity cleaning / drying medium. The supercritical wafer cleaning / drying medium recovery method comprises the following steps: a cleaning / drying step: dissolving and taking away an organic solvent attached to a wafer by using a supercritical cleaning / drying medium to obtain a mixed medium carrying the organic solvent; and a pressure reduction step of reducing the pressure of the mixed medium to a first pressure after the cleaning / drying step. And an adsorption step: after the decompression step, heating the decompressed mixed medium to a first temperature to obtain a gaseous mixed medium, contacting the gaseous mixed medium with the organic solvent adsorbent in the adsorber, adsorbing and enriching the organic solvent in the mixed medium by the organic solvent adsorbent, and separating the organic solvent from the cleaning / drying medium.

Description

Technical Field

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

[0002] Semiconductor wafers are one of the most important materials in the semiconductor industry, and have high requirements for their surface cleanliness. In the semiconductor wafer processing technology, in order to ensure the effective removal of solvents on the wafer surface and maintain the cleanliness of the wafer surface, the cleaning and drying of the wafer surface are indispensable processes. Some supercritical media have the characteristic of zero surface tension, which can more smoothly penetrate into the pore structure on the wafer surface and achieve efficient removal of solvents.

[0003] The existing supercritical medium cleaning and drying processes usually use supercritical cleaning / drying medium as a "one-time" consumable. However, the consumption of supercritical cleaning / drying medium is large during the cleaning and drying processes, resulting in too high costs for wafer cleaning / drying. Further, due to the possible mutual solubility of solvents and cleaning / drying medium to a certain extent in a specific temperature and / or pressure environment, it is difficult to separate and recover the cleaning / drying medium through some simple separation methods (such as gas-liquid separation, liquid-liquid separation, etc.), often resulting in a large amount of solvent impurities remaining in the recovered cleaning / drying medium and low purity.

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

[0005] In view of the above problems, the present invention provides a method and system for recovering supercritical wafer cleaning / drying medium, which can continuously recover high-purity cleaning / drying medium.

[0006] The first aspect of the present invention provides a method for recovering supercritical wafer cleaning / drying medium, including the following steps:

[0007] Cleaning / drying step: using supercritical cleaning / drying medium to dissolve and carry away the organic solvents attached to the wafer, obtaining a mixed medium carrying organic solvents.

[0008] Pressure reduction step: after the cleaning / drying step, reducing the pressure of the mixed medium to a first pressure.

[0009] Adsorption step: after the pressure reduction step, heating the pressure-reduced mixed medium to a first temperature to obtain a gaseous mixed medium, and contacting the gaseous mixed medium with an organic solvent adsorbent in an adsorber. The organic solvents in the mixed medium are adsorbed and enriched by the organic solvent adsorbent and separated from the cleaning / drying medium.

[0010] According to this technical solution, the organic solvents used in the wafer processing are generally organic solvents that are relatively soluble in the supercritical cleaning / drying medium (such as alcohol, ketone, and ester organic solvents), and it is difficult to separate them from the supercritical cleaning / drying medium. The organic solvent adsorbent is a material with high porosity, which can adsorb and analyze the organic solvent gas on the surface or pores through adsorption. Thus, by reducing the pressure and raising the temperature of the mixed medium of the organic solvent and the cleaning / drying medium to the gaseous mixed medium at the first pressure and the first temperature, and blowing the gaseous mixed medium through the organic solvent adsorbent, the adsorption of the organic solvent can be achieved. During the entire adsorption process, the cleaning / drying medium will not be blocked or enriched, and the organic solvent adsorbent has high selectivity for the organic solvent, so the loss of the cleaning / drying medium in the separation is reduced. In addition, by adsorbing the organic solvent with the organic solvent adsorbent, the gaseous cleaning / drying medium can be continuously separated from the organic solvent, and the high-purity cleaning / drying medium can flow out continuously, thereby realizing the recovery of the high-purity cleaning / drying medium.

[0011] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery method further includes the following steps:

[0012] Adsorber switching step: Determine whether the organic solvent adsorbent in the first adsorber has reached the adsorption threshold. If so, switch the adsorber in the adsorption step from the first adsorber to the second adsorber.

[0013] Desorption step: After the adsorber switching step, raise the temperature of the organic solvent adsorbent in the first adsorber to the second temperature. The organic solvent is desorbed from the organic solvent adsorbent in the first adsorber and then discharged from the first adsorber and flows into the organic solvent collection port.

[0014] According to this technical solution, through the adsorber switching step, when the organic solvent adsorbent in the first adsorber is about to reach the adsorption equilibrium, the adsorption step can be switched to the second adsorber to continue. At the same time, in the desorption step, the temperature of the organic solvent adsorbent in the first adsorber is raised to change the adsorption equilibrium of the organic solvent adsorbent in the first adsorber, prompting the desorption of the organic solvent adsorbent in the organic solvent adsorbent in the first adsorber, ensuring that the separation of the cleaning / drying medium can continue, and improving the separation and recovery efficiency of the cleaning / drying medium.

[0015] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery method further includes the following step: purification step, removing the organic solvent adsorbent particles in the cleaning / drying medium separated in the adsorption step.

[0016] According to this technical solution, since the organic solvent adsorbent in the adsorption step may escape during the adsorption / desorption process, removing the organic solvent adsorbent from the cleaning / drying medium obtained after the separation in the adsorption step can obtain a cleaning / drying medium with higher purity.

[0017] 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.

[0018] According to this technical solution, the surface tension of supercritical carbon dioxide is 0, and it can quickly dissolve organic solvents. Moreover, 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 extremely high porosity, high adsorption rate for organic solvents, and can adsorb almost all the organic solvent gases of alcohols, ketones, and esters mixed therein while not affecting the passage of carbon dioxide gas.

[0019] 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.

[0020] According to this technical solution, when the pressure of the carbon dioxide and organic solvent mixed medium is in the range of 3 - 9 MPa and the temperature is in the range of 30 - 90 °C, carbon dioxide is in a subcritical gaseous state. At this time, carbon dioxide and organic solvents are almost immiscible, and the organic solvent adsorbent has a very high adsorption equilibrium concentration for gaseous organic solvents. Thus, the organic solvent adsorbent can almost completely separate and adsorb the gaseous organic solvents in the mixed medium passing through the organic solvent adsorbent, and at the same time, the separated high-purity gaseous carbon dioxide can quickly flow out continuously through the organic solvent adsorbent. Then, by raising the temperature to 150 - 300 °C, the adsorption equilibrium concentration of the organic solvent adsorbent for organic solvents is reduced, promoting the desorption of organic solvents from the organic solvent adsorbent. And 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 organic solvents, the desorbed organic solvents can still be recycled through the organic solvent collection port.

[0021] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery method further includes the following steps:

[0022] Gas supply step, pressurizing and heating the gaseous cleaning / drying medium separated in the adsorption step and / or the external medium supplied by an external gas source to obtain a supercritical cleaning / drying medium for supplying the supercritical cleaning / drying medium used in the cleaning / drying step.

[0023] Pressure adjustment step: The gaseous cleaning / drying medium obtained in the adsorption step is pressurized and transported, and the pressure of the pressurized cleaning / drying medium is adjusted to be the same as the pressure of the external medium before the gas supply step.

[0024] According to this technical solution, since some of the cleaning / drying medium will remain on the wafer surface, there will be a certain loss of the cleaning / drying medium in the cycle. Therefore, by mixing the external gas source with the gaseous cleaning / drying medium obtained in the adsorption step for gas supply, it is possible to achieve the recycling of the cleaning / drying medium and supplement the loss of the cleaning / drying medium in the cycle, and maintain the amount of the supercritical medium used for cleaning / drying in the cleaning / drying step after multiple cycles.

[0025] Furthermore, the cleaning / drying medium obtained in the adsorption step is in a low-pressure gaseous state and has a slow flow rate. By the pressure adjustment step, the flow rate of the cleaning / drying medium is pressurized and promoted, and then the pressure before the gas supply step is adjusted to be the same as the pressure of the external gas source through pressure adjustment, which can make the pressure of the gaseous cleaning / drying medium entering the gas supply step stable. Among them, the external medium stored in the external gas source can be a gaseous or liquid medium.

[0026] The second aspect of the present invention provides a supercritical wafer cleaning / drying medium recovery system, including: a cleaning / drying device with a wafer built-in, which is used to dissolve and carry away the organic solvents attached to the wafer by using the supercritical cleaning / drying medium to obtain a mixed medium carrying the organic solvents; a first pressure reducing valve connected to the outlet of the cleaning / drying device, which is used to reduce the pressure of the mixed medium to a first pressure; an adsorption / desorption unit with an organic solvent adsorbent built-in, connected to the outlet of the first pressure reducing valve. The adsorption / desorption unit has a first heating device, which is used to heat the mixed medium entering the adsorption / desorption unit to a first temperature to obtain a gaseous mixed medium. The gaseous mixed medium contacts the organic solvent adsorbent, and the organic solvents in the mixed medium are adsorbed and enriched by the organic solvent adsorbent and separated from the cleaning / drying medium.

[0027] As a preferred technical solution, the adsorption / desorption unit includes: a plurality of adsorbers and a first heating device. The plurality of adsorbers are built-in with organic solvent adsorbents, and the plurality of adsorbers are arranged in parallel. The inlets of the plurality of adsorbers are connected to the outlet of the first pressure reducing valve, and the solvent outlets of the plurality of adsorbers are connected to an organic solvent collection port. The first heating device is arranged 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, and the second temperature is higher than the first temperature.

[0028] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery system further includes: a purifier connected to the medium outlet of the plurality of adsorbers, which is used to remove the organic solvent adsorbent particles in the cleaning / drying medium.

[0029] As a preferred technical solution, the supercritical wafer cleaning / drying medium recovery system further includes:

[0030] A gas supply unit, which is connected to the medium outlet of the adsorption / desorption unit and the inlet of the cleaning / drying equipment, and is used to pressurize and heat up the cleaning / drying medium flowing out of the adsorption / desorption unit to obtain a supercritical cleaning / drying medium for supply to the cleaning / drying equipment. An external gas source, the outlet of which is connected to the inlet of the gas supply unit. A pressure adjustment device, which is connected to the medium outlet of the adsorption / desorption unit and the inlet of the external gas source, and the pressure adjustment device includes a compressor and a second pressure reducing valve connected in sequence along the fluid flow direction. Description of the Drawings

[0031] Figure 1 is a flowchart of a supercritical wafer cleaning / drying medium recovery method provided by an embodiment of the present invention;

[0032] Figure 2 is a concentration line graph of isopropanol organic solvent in the NaY molecular sieve adsorbing mixed medium provided by an embodiment of the present invention;

[0033] Figure 3 is a schematic structural diagram of a supercritical wafer cleaning / drying medium recovery system applicable to an embodiment of the present invention;

[0034] Figure 4 is a flowchart of another supercritical wafer cleaning / drying medium recovery method provided by an embodiment of the present invention;

[0035] Figure 5 is a schematic structural diagram of another supercritical wafer cleaning / drying medium recovery system applicable to an embodiment of the present invention.

[0036] Description of the Reference Numerals

[0037] 100 - adsorption / desorption unit; 200 - gas supply unit;

[0038] 1 - external gas source; 2 - booster pump; 3 - second heating device; 4 - cleaning / drying equipment; 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 - vent port; 13 - organic solvent collection port. Detailed Embodiments

[0039] Combined with the following specific embodiments and drawings, the present invention will be further described in detail. The implementation of the present invention is not limited to the following embodiments, and various deformations, transformations, combinations, and improvements within the technical concept of the present invention adopted by those skilled in the art all fall within the protection scope of the present invention.

[0040] First Embodiment

[0041] Figure 1 A method for recovering a supercritical wafer cleaning / drying medium provided by the first embodiment of the present invention includes the following steps:

[0042] Cleaning / drying step S1: Using a supercritical cleaning / drying medium to dissolve and carry away the organic solvents attached to the wafer, obtaining a mixed medium carrying the organic solvents.

[0043] Pressure reduction step S2: After the cleaning / drying step S1, reducing the pressure of the mixed medium to a first pressure.

[0044] Adsorption step S3: After the pressure reduction step S2, heating the pressure-reduced mixed medium to a first temperature to obtain a gaseous mixed medium. The gaseous mixed medium contacts an organic solvent adsorbent in an adsorber, and the organic solvents in the mixed medium are adsorbed and enriched by the organic solvent adsorbent, separating from the cleaning / drying medium.

[0045] Adsorber switching step S4: Judging whether the organic solvent adsorbent in the first adsorber reaches the adsorption threshold. If so, switching the adsorber in the adsorption step S3 from the first adsorber to the second adsorber.

[0046] Desorption step S5: After the adsorber switching step S4, heating the organic solvent adsorbent in the first adsorber to a second temperature. The organic solvents are desorbed from the organic solvent adsorbent in the first adsorber and discharged from the first adsorber, flowing into an organic solvent collection port.

[0047] Purification step S6: Removing the organic solvent adsorbent particles in the cleaning / drying medium separated in the adsorption step S3.

[0048] It should be noted that the "organic solvent adsorbent" in the present invention can be any adsorbent with high selectivity for organic solvents. Preferably, an activated carbon adsorbent or a molecular sieve adsorbent with a pore diameter in the range of 0.7 nm - 0.9 nm is selected. For example, when the cleaning / drying medium is carbon dioxide and the organic solvent is isopropyl alcohol (IPA), NaY molecular sieve can be selected as the organic solvent adsorbent. The NaY molecular sieve has a very high adsorption rate for gaseous organic solvents. As Figure 2 shown, when the gaseous mixed medium passes through the NaY molecular sieve, the concentration of isopropyl alcohol in the gaseous mixed medium rapidly decreases to a position infinitely close to 0, that is, almost all of the isopropyl alcohol is adsorbed and enriched by the NaY molecular sieve, and it will not affect the normal passage of carbon dioxide gas, thus realizing the separation of gaseous carbon dioxide and gaseous isopropyl alcohol.

[0049] The cleaning / drying medium in the supercritical state can be any medium that can dissolve the organic solvent on the surface of the wafer. Preferably, the cleaning / drying medium is carbon dioxide. The surface tension of supercritical carbon dioxide is 0, which can dissolve the organic solvent well and remove the solvent residue on the surface of the wafer.

[0050] Among them, the organic solvent can undergo the adsorption and desorption processes with the organic solvent adsorbent under specific adsorption environment parameters (an environment composed of one or a combination of factors such as specific pressure, temperature, atmosphere, etc.). In this embodiment, preferably, the adsorption and desorption processes of the organic solvent are controlled by controlling the pressure and temperature. Specifically, the adsorption step S3 is carried out at the first pressure and the first temperature, and the desorption step S5 is carried out at the first pressure and the second temperature. The second temperature is higher than the first pressure. Further 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, the carbon dioxide in the mixed medium is in the subcritical gaseous state and is almost immiscible with the gaseous organic solvent, and it is very easy to separate from the carbon dioxide. At this time, the organic solvent adsorbent has a high adsorption equilibrium concentration for the gaseous organic solvent, so that the organic solvent adsorbent can almost completely separate and adsorb the gaseous organic solvent in the mixed medium, which can reduce the loss of the cleaning / drying medium in the separation and can continuously separate and recover the high-purity cleaning / drying medium. And at the first pressure and the second temperature, the adsorption equilibrium concentration of the organic solvent adsorbent for the organic solvent decreases, which promotes the desorption of the organic solvent from the organic solvent adsorbent. Therefore, by maintaining the pressure and adjusting the temperature, the separation of the cleaning / drying medium in the mixed medium and the adsorption process of the organic solvent can be realized, making the separation and recovery process more flexible and controllable.

[0051] Figure 3 This is a supercritical wafer cleaning / drying medium recovery system provided by this embodiment, which is applicable to the above-mentioned supercritical wafer cleaning / drying medium recovery method. As Figure 3 shown, the supercritical wafer cleaning / drying medium recovery system includes a flow path formed by sequentially connecting a cleaning / drying device 4, a first pressure reducing valve 5, an adsorption / desorption unit 100, and a purifier 9.

[0052] Among them, the cleaning / drying device 4 is a specific place for completing wafer cleaning or drying. For example, the cleaning / drying device 4 can be formed as a cleaning tank with openings at both ends, and a wafer mounting structure is arranged in the tank. The supercritical cleaning / drying medium can flow into the cleaning tank from one 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.

[0053] The first pressure reducing valve 5 is connected to the outlet of the cleaning / drying device 4. The first pressure reducing valve 5 is a component with the function of reducing the pressure of the flowing working medium, including but not limited to a pressure reducing valve that can control the outlet pressure to be constant in the traditional sense, and a needle valve with a throttling function.

[0054] The adsorption / desorption unit 100 is connected to the outlet of the first pressure reducing valve 5. The adsorption / desorption unit 100 includes an adsorber and a first heating device 6. Among them, the adsorber is internally provided with an organic solvent adsorbent. Preferably, the adsorption / desorption unit has a first adsorber 7 and a second adsorber 8 arranged in parallel. The first heating device 6 is arranged around the first adsorber 7 and the second adsorber 8. The first heating device 6 is a component with the function of heating the flowing working medium, including but not limited to electric heating, fuel heating, and a device for performing flowing heat exchange with a second medium.

[0055] The purifier 9 is connected to 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 desorbed gaseous cleaning / drying medium and filter the residual organic solvent adsorbent therein.

[0056] Specifically, the cleaning / drying device executes the cleaning / drying step S1. The supercritical cleaning / drying medium enters the cleaning / drying device 4 with a wafer placed inside, cleans and takes away the solvent on the wafer surface, and obtains a mixed medium carrying the solvent. Then, the pressure reducing step S2 is executed. The mixed medium flowing out of the cleaning / drying device first enters the first pressure reducing valve 5. After the supercritical cleaning / drying medium is depressurized by the first pressure reducing valve 5, it reaches the first pressure of 3 - 9 MPa at the outlet of the first pressure reducing valve 5. Subsequently, the adsorption step S3 is executed. The mixed medium at the first pressure is introduced into the adsorption / desorption unit 100. The first heating device 6 in the adsorption / desorption unit 100 heats the mixed medium so that the mixed medium reaches the 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 contacts the organic solvent adsorbent. The organic solvent is adsorbed by the organic solvent adsorbent. At the same time, 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, and removes the escaped adsorbent particles, thereby completing the separation of the high-purity cleaning / drying medium.

[0057] After continuously performing the adsorption step S3 for a period of time, the adsorption bed switching step S4 is executed to determine whether the organic solvent adsorbent in the first adsorber 7 reaches the adsorption threshold. Here, the adsorption threshold can 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 herein. If the organic solvent adsorbent in the first adsorber 7 reaches the adsorption threshold, the adsorber in the adsorption step S3 is switched to the second adsorber 8. While the second adsorber 8 performs the adsorption step S3, the first adsorber 7 performs the desorption step S5, and the temperature of the first adsorber 7 is increased to the second temperature of 150 - 300 °C by 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 solvent outlet of the first adsorber 7 through the organic solvent collection port 13.

[0058] In the above manner, during the entire adsorption process, the cleaning / drying medium will not be blocked or enriched, and the organic solvent adsorbent has high selectivity for organic solvents and can almost completely adsorb all the organic solvents in the mixed medium. Therefore, while ensuring the high purity of the cleaning / drying medium separation, the loss of the cleaning / drying medium in the separation is reduced.

[0059] In addition, by adsorbing organic solvents with the organic solvent adsorbent and switching the first adsorber 7 and the second adsorber 8 through the adsorber switching step S4, the adsorption and desorption processes can be carried out simultaneously in the first adsorber 7 and the second adsorber 8, improving the separation efficiency of the cleaning / drying medium and enabling the continuous outflow of the high-purity cleaning / drying medium, thereby realizing the continuous recovery of the high-purity cleaning / drying medium.

[0060] Second Embodiment

[0061] Among them, preferably, Figure 3 The flowchart of another supercritical wafer cleaning / drying medium recovery method provided by this embodiment is shown in. As Figure 3 shown, the supercritical wafer cleaning / drying medium recovery method further includes:

[0062] The gas supply step S7, in which the gaseous cleaning / drying medium separated in the adsorption step S3 and / or the external medium supplied by the external gas source are pressurized and heated to obtain a supercritical cleaning / drying medium for supplying the supercritical cleaning / drying medium used in the cleaning / drying step S1.

[0063] The pressure adjustment step S8, in which the gaseous cleaning / drying medium obtained in the adsorption step S3 is pressurized and transported, and the pressure of the pressurized cleaning / drying medium is adjusted to be the same as the pressure of the external medium before the gas supply step S7.

[0064] Correspondingly,Figure 4 The structural schematic diagram of a preferred supercritical wafer cleaning / drying medium recovery system is shown. As Figure 4 shown, the supercritical wafer cleaning / drying medium recovery system further includes: a gas supply unit 200, an external gas source 1, and a pressure adjustment device (including a compressor 10 and a second pressure reducing valve 11 connected in sequence). Among them, 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, and is used to pressurize and heat up the cleaning / drying medium flowing out of the medium outlet of the adsorption / desorption unit 100 to obtain a supercritical cleaning / drying medium for supply to the cleaning / drying device 4 for use. The outlet of the external gas source 1 communicates with the inlet of the gas supply unit 200; the compressor 10 in the pressure adjustment 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.

[0065] Among them, as Figure 5 shown, the gas supply unit 200 can be a combined unit of a booster pump 2 and a second heating device 3. The booster pump 2 is a device that can pressurize and output a fluid working medium, and its forms include but are not limited to positive displacement pumps and reciprocating pumps.

[0066] The external gas source 1 refers to a gas source in a broad sense, which can input gaseous or liquid working media 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 some other embodiments, the external gas source 1 can also be a gas supply system composed of a storage tank and its affiliated cooling equipment.

[0067] The pressure adjustment device is a combined unit of a compressor 10 and a second pressure reducing valve 11. The compressor 10 is a device that can increase the pressure of a gaseous medium, and its forms include but are not limited to centrifugal compressors and axial compressors. 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 by the external gas source 1.

[0068] In this embodiment, the medium loss in the system is supplemented by the external gas source 1, so that the continuous circulation of the system can be maintained. Further, the pressure increase by the compressor 10 can promote the working medium to flow backward at an accelerated speed, and the second pressure reducing valve 11 can control the outlet pressure of the pressure adjustment device to be equal to the outlet pressure of the external gas source 1, so that the medium at the outlet of the pressure adjustment device can be mixed with the medium of the external gas source isobarically and then enter the gas supply unit 200 to maintain the stable and safe operation of the system.

[0069] Specifically, starting from the external gas source 1, the gas supply step S7 is executed. The external gas source 1 supplies the cleaning / drying medium into the system. The cleaning / drying medium is boosted in pressure by the booster pump 2 and heated by the second heating device 3 to reach the supercritical state of high temperature and high pressure. Then, steps S1 - S6 are sequentially executed in the same order as in the first embodiment. After that, the pressure adjustment step S8 is executed. The high-purity gaseous cleaning / drying medium flowing out of the purifier 9 flows through the compressor 10 and the second pressure reducing valve 11. The low-pressure gaseous medium flows slowly. After being boosted in pressure by the compressor, it can push the medium to flow rapidly, and is reduced in pressure to the same pressure as the external gas source 1 by the second pressure reducing valve 11, so that the medium stably enters the external gas source 1, mixes with the external medium provided by the external gas source 1, and then the gas supply step S7 is cyclically executed again.

[0070] In other preferred embodiments of the present invention, the supercritical wafer cleaning / drying medium recovery system further includes a vent port 12, which can be arranged on any section of the pipeline of the system for venting the medium in special or emergency situations.

[0071] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recovering supercritical wafer cleaning / drying medium, characterized in that, It includes the following steps: A cleaning / drying step, in which a supercritical cleaning / drying medium is used to dissolve and carry away the organic solvents attached to the wafer, obtaining a mixed medium carrying the organic solvents; A pressure reduction step, after the cleaning / drying step, reducing the pressure of the mixed medium to a first pressure; An adsorption step, after the pressure reduction step, heating the depressurized mixed medium to a first temperature to obtain a gaseous mixed medium, the gaseous mixed medium contacts with an organic solvent adsorbent in an adsorber, and the organic solvents in the mixed medium are adsorbed and enriched by the organic solvent adsorbent, separating from the cleaning / drying medium.

2. The method for recovering supercritical wafer cleaning / drying medium according to claim 1, characterized in that, It further includes the following steps: An adsorber switching step, judging whether the organic solvent adsorbent in the first adsorber reaches the adsorption threshold, if so, switching the adsorber in the adsorption step from the first adsorber to the second adsorber; A desorption step, after the adsorber switching step, heating the organic solvent adsorbent in the first adsorber to a second temperature, the organic solvents are desorbed from the organic solvent adsorbent in the first adsorber and discharged from the first adsorber, and flow into an organic solvent collection port.

3. The method for recovering supercritical wafer cleaning / drying medium according to claim 1, characterized in that, It further includes the following steps: A purification step, removing the organic solvent adsorbent particles in the cleaning / drying medium separated in the adsorption step.

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

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

6. The method for recovering supercritical wafer cleaning / drying medium according to claim 1, characterized in that, It further includes the following steps: A gas supply step, pressurizing and heating the gaseous cleaning / drying medium separated in the adsorption step and / or an external medium supplied by an external gas source to obtain a supercritical cleaning / drying medium, to supply the supercritical cleaning / drying medium used in the cleaning / drying step; A pressure adjustment step, 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.

7. A system for recovering supercritical wafer cleaning / drying medium, characterized in that, It includes: A cleaning / drying device, with a wafer built-in, for using a supercritical cleaning / drying medium to dissolve and carry away the organic solvents attached to the wafer, obtaining a mixed medium carrying the organic solvents; A first pressure reducing valve, connected to the outlet of the cleaning / drying device, for reducing the pressure of the mixed medium to a first pressure; An adsorption / desorption unit, with the organic solvent adsorbent built-in, connected to 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 a first temperature to obtain a gaseous mixed medium, the gaseous mixed medium contacts with the organic solvent adsorbent, and the organic solvents in the mixed medium are adsorbed and enriched by the organic solvent adsorbent, separating from the cleaning / drying medium.

8. The system for recovering supercritical wafer cleaning / drying medium according to claim 7, characterized in that, The adsorption / desorption unit includes: Multiple adsorbers, with the organic solvent adsorbent built therein, the multiple adsorbers are arranged in parallel, the inlets of the multiple adsorbers are communicated with the outlet of the first pressure reducing valve, and the solvent outlets of the multiple adsorbers are communicated with the organic solvent collection port; The first heating device, arranged around the multiple adsorbers, is used to control the temperature of the multiple adsorbers to a first temperature or a second temperature, and the second temperature is higher than the first temperature.

9. The system for recovering supercritical wafer cleaning / drying medium according to claim 8, characterized in that, It further includes: A purifier, communicated with the medium outlets of the multiple adsorbers, is used to remove the organic solvent adsorbent particles in the cleaning / drying medium.

10. The system for recovering supercritical wafer cleaning / drying medium according to claim 9, characterized in that, It further includes: A gas supply unit, the gas supply unit is communicated with the medium outlet of the adsorption / desorption unit and the inlet of the cleaning / drying device, and the gas supply unit includes a booster pump and a second heating device; An external gas source, the outlet of the external gas source is communicated with the inlet of the gas supply unit; A pressure adjustment device, communicated with the medium outlet of the adsorption / desorption 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.

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