Drying method using supercritical fluid as drying medium

Abstract

The application discloses a drying method using supercritical fluid as a drying medium, and a drying system comprises a drying chamber, a plurality of fluid pipes are arranged on the bottom wall of the drying chamber and extend into the drying chamber, a flow guide structure is arranged on the top wall of the drying chamber, the drying chamber is provided with a drying cavity, the flow guide structure is communicated with the drying cavity, an annular nozzle and a bearing table are arranged in the middle part of the drying cavity, the bearing table is suitable for bearing a to-be-dried element, the annular nozzle is communicated with the plurality of fluid pipes respectively, the annular nozzle is suitable for being arranged around the to-be-dried element, and the bearing table is located directly below the flow guide structure. In this way, the surface drying of the to-be-dried element is more uniform.

Description

Technical Field

[0001] This invention relates to the field of supercritical drying technology, and more specifically to a drying method using supercritical fluid as the drying medium. Background Technology

[0002] In recent years, new technologies have emerged to address the challenges of non-destructive cleaning and drying of nanoscale deep trenches. In non-destructive cleaning, technologies such as submicron-level atomized two-fluid cleaning, low-temperature aerosol cleaning, and polymer film cleaning have been applied to the development of non-destructive cleaning processes for wafers at higher technology nodes. In non-destructive drying, technologies such as solvent (isopropanol, acetone, etc.) vapor-assisted drying, sublimation drying, surface modification-assisted drying, and supercritical fluid drying have also been applied to the development of non-destructive drying processes for wafers at higher technology nodes. Sublimation drying can reduce the surface tension of traditional drying methods by 10%, surface modification-assisted drying can reduce it by 40%, acetone vapor-assisted drying can effectively reduce it by 60%, and supercritical fluid drying is a truly surface tension-free drying technology, thus it is widely used in wafer drying.

[0003] Existing supercritical fluid drying devices have two purging methods, such as... Figure 1 As shown, the first purging method uses supercritical fluid to blow the wafer surface from one side to the other to dry the wafer. However, this purging method has a problem: the velocity distribution of the supercritical fluid in the purging direction is uneven, resulting in uneven drying; for example... Figure 2 As shown, the second purging method is to use supercritical fluid to vertically blow the wafer surface from top to bottom to dry the wafer. However, this purging method has the following problems: when the supercritical fluid blows the wafer surface, the flow velocity at the center is relatively large, which poses a risk of impacting the wafer. In addition, the purging velocity of the supercritical fluid from the center to the edge of the wafer is still unevenly distributed, resulting in uneven drying.

[0004] In view of the above shortcomings, it is necessary to design a drying method using supercritical fluid as the drying medium. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is that the supercritical fluid drying device in the prior art has an uneven drying process, and thus provides a drying method using supercritical fluid as the drying medium.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A drying system using supercritical fluid as the drying medium includes a drying chamber, a plurality of fluid pipes installed on the bottom wall of the drying chamber, a flow guiding structure provided on the top wall of the drying chamber, a drying cavity formed within the drying chamber, the flow guiding structure and the fluid pipes being connected to the drying cavity, an annular nozzle and a support platform provided in the middle of the drying cavity, the support platform being located directly below the flow guiding structure and adapted to support the element to be dried, the annular nozzle being connected to the plurality of fluid pipes respectively, and the annular nozzle being adapted to surround the element to be dried.

[0008] Furthermore, the centerline of the flow guiding structure coincides with the centerline of the annular nozzle, and the center of the element to be dried is adapted to coincide with the center of the annular nozzle.

[0009] Furthermore, the annular nozzle has a notch, so that the annular nozzle surrounds the element to be dried at a 270° to 320° angle.

[0010] Furthermore, the flow guiding structure includes an umbrella-shaped flow guiding hood located within the drying chamber, and a flow guiding pipe communicating with the flow guiding hood and penetrating the top wall of the drying chamber.

[0011] Furthermore, a pressure-boosting nozzle is installed on the bottom wall of the drying chamber, a through hole is provided on the bottom surface of the support platform, and a baffle plate is provided inside the drying chamber. The baffle plate is located between the pressure-boosting nozzle and the through hole to prevent the supercritical fluid ejected from the pressure-boosting nozzle from impacting the element to be dried.

[0012] Furthermore, two pressure-reducing outlet groups are provided on the top wall of the drying chamber, the center line of the flow guiding structure coincides with the center line of the drying chamber, and the two pressure-reducing outlet groups are symmetrically arranged about the flow guiding structure.

[0013] Furthermore, it also includes a supercritical fluid supply pipeline and a supercritical fluid purification structure disposed on the supercritical fluid supply pipeline. In the flow direction of the supercritical fluid, the pressure boosting nozzle and the fluid pipeline are both located downstream of the supercritical fluid purification structure and are respectively connected to the supercritical fluid supply pipeline.

[0014] The technical solution of this invention has the following advantages:

[0015] 1. The drying system using supercritical fluid as the drying medium provided by this invention has multiple fluid pipes installed on the bottom wall of the drying chamber and a flow guiding structure on the top wall of the drying chamber. A drying chamber is formed inside the drying chamber, and the flow guiding structure and fluid pipes are connected to the drying chamber. An annular nozzle and a support platform are provided in the middle of the drying chamber. The support platform is located directly below the flow guiding structure and is suitable for supporting the element to be dried. The annular nozzle is connected to the multiple fluid pipes respectively and is suitable for surrounding the element to be dried. In this way, the supercritical fluid entering the annular nozzle from the fluid pipes will be distributed along the circumference of the element to be dried and blown from the edge of the element to be dried towards the center. At the same time, the supercritical fluid is continuously discharged from the flow guiding structure located above the element to be dried, so that the supercritical fluid on the surface of the element to be dried exhibits a velocity distribution with a slightly higher velocity at the edge and a slightly lower velocity at the center. This is consistent with the distribution of the liquid film on the surface of the element to be dried, which is thicker at the edge and thinner at the center due to surface tension. Therefore, it is beneficial to the uniformity and consistency of drying on the surface of the element to be dried.

[0016] 2. The drying system provided by the present invention, which uses supercritical fluid as the drying medium, has a centerline of the flow guiding structure that coincides with the centerline of the annular nozzle, and the center of the element to be dried is adapted to coincide with the center of the annular nozzle. This further adapts the flow velocity distribution of the supercritical fluid on the surface of the element to be dried to the morphology of the liquid film on the surface of the element to be dried, thereby further improving the uniformity of drying.

[0017] 3. The drying system using supercritical fluid as the drying medium provided by the present invention is further equipped with a pressure-boosting nozzle on the bottom wall of the drying chamber, a through hole on the bottom surface of the support platform, and a baffle plate inside the drying chamber. The baffle plate is located between the pressure-boosting nozzle and the through hole to prevent the supercritical fluid ejected from the pressure-boosting nozzle from impacting the element to be dried. In this way, the element to be dried can be prevented from being blown away by the supercritical fluid and moving its position, thus affecting the distribution of the liquid film on the surface of the element to be dried and protecting the pattern on the surface of the element to be dried.

[0018] 4. The drying system using supercritical fluid as the drying medium provided by the present invention has two sets of pressure-reducing outlets on the top wall of the drying chamber. The center line of the flow guiding structure coincides with the center line of the drying chamber. The two sets of pressure-reducing outlets are symmetrically arranged about the flow guiding structure. In this way, the uniformity of the flow field in the drying chamber can be improved, and the distribution of the liquid film on the surface of the element to be dried can be avoided, so as to protect the pattern on the surface of the element to be dried.

[0019] 5. The drying system using supercritical fluid as the drying medium provided by the present invention further includes a supercritical fluid supply pipeline and a supercritical fluid purification structure disposed on the supercritical fluid supply pipeline. In the flow direction of the supercritical fluid, the pressure boosting nozzle and the fluid pipeline are both located downstream of the supercritical fluid purification structure and are respectively connected to the supercritical fluid supply pipeline. In this way, organic impurities and water contained in the supercritical fluid entering the drying chamber can be removed, thereby avoiding the formation of organic particle residues on the element to be dried by organic impurities and avoiding the presence of water from affecting the drying effect.

[0020] A drying method using a supercritical fluid as the drying medium, the drying method comprising the following steps:

[0021] Place the element to be dried: Place the element to be dried on the support platform in the drying chamber, so that the center of the element to be dried coincides with the center of the annular nozzle, and the center line of the annular nozzle coincides with the center line of the flow guiding structure;

[0022] Purging stage: The pressure reducing outlet group and the pressure boosting nozzle are in the open state, and the flow guiding structure and fluid pipeline are in the closed state. Supercritical fluid is injected into the drying chamber through the pressure boosting nozzle for a continuous purging time to purge the nitrogen or air in the drying chamber.

[0023] Pressure boosting and holding stage: includes pressure boosting stage and pressure holding stage, continuous pressure boosting and holding time. In the pressure boosting stage, the pressure reducing outlet group is closed, and the supercritical fluid is continued to be injected into the drying chamber through the pressure boosting nozzle until the pressure in the drying chamber reaches the holding pressure. Then the pressure boosting nozzle is closed, and the process enters the pressure holding stage.

[0024] Purging stage: The fluid pipeline and flow guiding structure are in the open state. Supercritical fluid is introduced into the annular nozzle through the fluid pipeline. The flow rate of the fluid pipeline and flow guiding structure is adjusted according to the temperature and pressure signals in the drying chamber monitored by the chamber pressure sensor and the chamber temperature sensor, respectively. The pressure in the drying chamber is alternately reduced and increased above the critical pressure of the supercritical fluid to form a periodically changing purging flow field between the annular nozzle and the flow guiding structure to purge the surface of the element to be dried. After the purging time, the liquid film on the element to be dried is completely dissolved.

[0025] Pressure relief and discharge stage: The fluid pipeline is closed, while the pressure reducing outlet group and the flow guiding structure are both open, and pressure is released at a uniform speed.

[0026] Furthermore, during the pressure increase and holding stage, the temperature inside the drying chamber is 31°C to 200°C, and the holding pressure is 7MPa to 20MPa.

[0027] Furthermore, during the venting stage and the pressurization and pressure holding stage, the flow rate of the pressurizing nozzle (44) is the same, ranging from 0.5 kg / min to 2 kg / min, and / or, during the purging stage, the flow rate difference between the supercritical fluid in the fluid pipeline and the flow guide structure is from 0.5 kg / min to 1 kg / min, and / or, during the pressure relief and discharge stage, the total discharge flow rate of the supercritical fluid via the pressure reducing outlet group and the flow guide structure is from 0.5 kg / min to 1 kg / min.

[0028] Furthermore, during the venting stage and / or the pressurization and pressure holding stage, the density of the supercritical fluid in the inlet section of the supercritical fluid supply pipeline is 400 kg / m³. 3 Up to 800kg / m 3 And / or, during the purging phase, the density of the supercritical fluid in the inlet section of the supercritical fluid supply pipeline is 200 kg / m³. 3 Up to 600kg / m 3 The inlet section is adjacent to the drying chamber.

[0029] 1. The drying method using supercritical fluid as the drying medium provided by the present invention can improve the drying uniformity of the surface of the component to be dried.

[0030] 2. The drying method using supercritical fluid as a drying medium provided by the present invention, in the pressure relief and discharge stage, the total discharge flow rate of supercritical fluid through the pressure reducing outlet group and the flow guiding structure is 0.5 kg / min to 1 kg / min. In this way, the supercritical fluid can be directly converted from the supercritical state to the gaseous state for discharge, avoiding the risk of the supercritical fluid entering the liquid state due to its adiabatic expansion process during discharge, which would increase the risk of the pattern on the surface of the element to be dried collapsing. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the purging flow field formed by supercritical fluid on the wafer surface in the first purging method of the prior art.

[0033] Figure 2 This is a schematic diagram of the purging flow field formed by supercritical fluid on the wafer surface in the second purging method in the prior art.

[0034] Figure 3This is a schematic diagram of the drying system using supercritical fluid as the drying medium in this invention.

[0035] Figure 4 This is a perspective view of the drying chamber in the drying system using supercritical fluid as the drying medium in this invention.

[0036] Figure 5 This is a schematic diagram of the external structure of the drying chamber in the drying system using supercritical fluid as the drying medium in this invention.

[0037] Figure 6 This is a perspective view of the drying chamber in the drying system using supercritical fluid as the drying medium in this invention.

[0038] Figure 7 This is a cross-sectional view of the drying chamber in the drying system using supercritical fluid as the drying medium in this invention.

[0039] Figure 8 This is a schematic diagram of the pressure changes within the drying chamber during the drying process of the drying system using supercritical fluid as the drying medium in this invention.

[0040] Figure 9 This is a schematic diagram illustrating the smooth flow of supercritical fluid on the wafer surface during the drying method using supercritical fluid as the drying medium in this invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1. Supercritical fluid gas source; 2. Supercritical fluid preparation device; 3. Supercritical fluid supply pipeline; 30. Inlet section; 31. First on / off valve; 32. First temperature sensor; 33. First throttling component; 34. Second on / off valve; 35. Supercritical fluid purification structure; 36. Chamber inlet on / off valve; 37. Annular nozzle on / off valve; 38. Pressure boosting nozzle on / off valve; 4. Drying chamber; 4a. Process passage; 4b. Maintenance passage; 4c. Guide rail; 4d. First sealing mechanism; 4e. Cylinder; 4f. Second sealing mechanism; 4g. Vacuum machinery 40. Arm; 41. Chamber temperature sensor; 42. Chamber pressure sensor; 43. Drying chamber; 44. Fluid pipeline; 45. Pressure boosting nozzle; 46. Support platform; 47. Through hole; 48. Annular nozzle; 49. Notch; 40. Baffle plate; 41. Flow guiding structure; 42. Flow guide shroud; 43. Flow guide pipe; 44. Pressure reducing outlet group; 5. Nitrogen purging self-cleaning pipeline; 6. Bypass pipeline; 7. Escape pipeline; 8. Discharge pipeline; 81. Discharge on / off valve; 82. Overflow valve; 83. Third on / off valve; 84. Flow meter; 9. Element to be dried. Detailed Implementation

[0043] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Example

[0048] like Figures 3 to 9 As shown, this embodiment provides a drying system using supercritical fluid as the drying medium to dry the isopropanol liquid film (or acetone liquid film) on the surface of a wafer. Of course, it can also be used to dry other components. For ease of explanation, the components that need to be dried, such as wafers, are referred to as components to be dried 9.

[0049] like Figure 3 As shown, the drying system includes a supercritical fluid gas source 1, a supercritical fluid preparation device 2, a supercritical fluid supply pipeline 3, a drying chamber 4, a chamber temperature sensor 40, a chamber pressure sensor 41, an isopropanol concentration monitoring device (not shown), a nitrogen purging self-cleaning pipeline 5, a bypass pipeline 6, an escape pipeline 7, and an exhaust pipeline 8.

[0050] In this embodiment, as Figure 3As shown, the supercritical fluid supply pipeline 3 is sequentially equipped with a first on / off valve 31, a first temperature sensor 32, a first throttling component 33, a second on / off valve 34, a supercritical fluid purification structure 35, and a chamber inlet on / off valve 36. The section of the supercritical fluid supply pipeline 3 adjacent to the drying chamber 4 is defined as the inlet section 30. The escape pipeline 7 connects to the first throttling component 33 and the second on / off valve 34 on the supercritical fluid supply pipeline 3, providing an escape path for a portion of the supercritical fluid. One end of the nitrogen purging self-cleaning pipeline 5 is connected to a nitrogen source, and the other end... The supercritical fluid purification structure 35 is connected to the supercritical fluid supply pipeline 3 and the chamber inlet on / off valve 36; the discharge pipeline 8 is used to discharge the gas in the drying chamber 42 through the discharge on / off valve 81, overflow valve 82, third on / off valve 83, flow meter 84, etc.; one end of the bypass pipeline 6 is connected between the first throttling component 33 and the second on / off valve 34 on the supercritical fluid supply pipeline 3, and the other end is connected between the third on / off valve 83 and the flow meter 84 on the discharge pipeline 8, so as to provide a discharge path for part of the supercritical fluid through the flow meter 84. In this embodiment, the supercritical fluid purification structure 35 is formed by two to five filters connected in parallel. The reason for choosing the parallel method is, on the one hand, to ensure the filtration effect, and on the other hand, to ensure that the filtration task can still be completed when one of the filters is under maintenance.

[0051] like Figure 4 and Figure 5 As shown, the design pressure of the drying chamber 4 is 20 MPa, and guide rails 4c are respectively provided on two opposite sides outside the drying chamber 4. The two ends of the drying chamber 4 are connected to form a process channel 4a and a maintenance channel 4b, respectively. The process channel 4a is for wafer entry and exit and is sealed by a first sealing mechanism 4d, which is driven by a cylinder 4e to slide laterally along the aforementioned guide rail 4c. The maintenance channel 4b is sealed by a second sealing mechanism 4f, which is only manually opened when troubleshooting machine malfunctions or performing maintenance. Sealing elements are provided between the first sealing mechanism 4d and the second sealing mechanism 4f and the drying chamber 42, and the sealing elements will come into contact with the supercritical fluid. In order to reduce the dissolution of impurities into the supercritical fluid, sealing materials with high cleanliness and stable physical properties must be selected, including but not limited to fluorine-free resin, fluorine-free rubber, or metal springs. The main body of the drying chamber 4 is made of 316 or 304 stainless steel. The inner wall of the drying chamber 4 is preferably treated with electropolishing, chemical processing, or heat treatment to increase the Cr content and form a Cr2O3 oxide film, thereby increasing the stability of the inner wall and reducing contamination of the supercritical fluid by impurities and metals. Heating resistance wires are embedded in the inner wall of the drying chamber 4, and the outside of the drying chamber 4 is wrapped with insulating material for heat preservation.

[0052] like Figure 4 , Figure 6 and Figure 7As shown, the drying chamber 4 is hollow, and a drying chamber 42 is formed inside it.

[0053] Multiple fluid pipes 43 extending into the drying chamber 42 are installed on the bottom wall of the drying chamber 4, and a pressure-boosting nozzle 44 is also installed on the bottom wall of the drying chamber 4. In the flow direction of the supercritical fluid, the pressure-boosting nozzle 44 and the fluid pipes 43 are both located downstream of the supercritical fluid purification structure 35 and the chamber inlet on / off valve 36, and are respectively connected to the inlet section 30. A support platform 45, an annular nozzle 46, and a baffle plate 47 are provided in the middle of the drying chamber 42. The element 9 to be dried is placed on the support platform 45, which has a through hole 451 in the middle and is located directly above the pressure-boosting nozzle 44. The annular nozzle 46 is connected to the multiple fluid pipes 43 respectively, and a notch 461 is opened on the annular nozzle 46 so that the annular nozzle 46 is arranged around the element 9 to be dried at 270° to 320°, the center of the annular nozzle 46 coincides with the center of the element 9 to be dried, and the annular nozzle 46 is circular. The notch 461 provides a space for the vacuum robotic arm 4g to pick up the element 9 to be dried and place it on the support stage 45. In this embodiment, the baffle 47 is circular with a radius of 100mm to 250mm and a distance of 5mm to 20mm from the wafer. Of course, when the element 9 to be dried is a non-wafer type, the size of the baffle 47 and the distance between it and the element 9 to be dried may be different. No specific limitation is made here. It can be set according to actual needs, as long as the baffle 47 can block the supercritical fluid sprayed by the boost nozzle 44 onto the element 9 to be dried.

[0054] In one embodiment, the support platform 45, the annular nozzle 46 and the fluid pipeline 43 are connected as one unit, with the bottom wall of the annular nozzle 46 serving as the support platform 45. The baffle plate 47 is located between the boost nozzle 44 and the element to be dried 9 to block the supercritical fluid ejected from the boost nozzle 44 and prevent it from impacting the element to be dried 9.

[0055] In another embodiment, the support platform 45 and the annular nozzle 46 are each formed. The annular nozzle 46 is arranged around the element 9 to be dried placed on the support platform 45. The baffle 47 is still located between the boost nozzle 44 and the element 9 to be dried, and is suitable for blocking the supercritical fluid ejected from the boost nozzle 44 to avoid impacting the element 9 to be dried.

[0056] A flow guiding structure 48 is provided on the top wall of the drying chamber 4, and two pressure-reducing outlet groups 49 are also provided on the top wall of the drying chamber 4. The two pressure-reducing outlet groups 49 are symmetrically arranged about the flow guiding structure 48, and each pressure-reducing outlet group 49 includes multiple pressure-reducing outlets arranged along the same straight line. The flow guiding structure 48 includes a flow guiding hood 481 in the shape of an umbrella and located in the drying chamber 42, and a flow guiding pipe 482 communicating with the flow guiding hood 481 and penetrating the top wall of the drying chamber 4. The flow guiding hood 481 is conical, and the opening angle of the flow guiding hood 481 is 150° to 175°. In this way, while ensuring the flow guiding effect, the height of the drying chamber 4 can be reduced. In this embodiment, the center line of the flow guiding structure 48 coincides with the center line of the annular nozzle 46, and the center line of the flow guiding structure 48 coincides with the center line of the drying chamber 4. The two pressure-reducing outlet groups 49 are symmetrically arranged about the flow guiding structure 48.

[0057] The following describes a drying method for drying a wafer using the supercritical fluid as the drying medium provided in this embodiment, taking the element 9 to be dried as a wafer as an example:

[0058] Wafer introduction stage: Before introducing the wafer, if the drying chamber 42 is in the stage where the previous wafer has finished drying, the pressure relief outlet and the flow guiding structure 48 are opened to reduce the pressure in the drying chamber 42 to atmospheric pressure. Once the pressure in the drying chamber 42 has dropped to atmospheric pressure, the cylinder 4e is activated to drive the first sealing mechanism 4d to move laterally along the guide rail 4c, opening the first sealing mechanism 4d. The vacuum robotic arm 4g removes the previous wafer that has finished drying and puts it back into the wafer cassette. The next wafer filled with liquid isopropanol is placed on the support stage 45, and the center of the wafer is aligned with the center of the annular nozzle 46. The first sealing mechanism 4d is then closed, completing the wafer introduction step. If the drying chamber 42 is in the standby nitrogen purging stage, the purging is stopped and the pressure in the drying chamber 42 is allowed to drop to atmospheric pressure before the wafer is placed on the support stage 45.

[0059] Emptying stage: Adjust the density of the supercritical fluid in inlet section 30 to 400 kg / m³. 3 Up to 800kg / m 3 (Preferred value: 500 kg / m) 3 Up to 600kg / m 3The temperature inside the drying chamber 42 is maintained at 31°C to 200°C (preferably 80°C to 150°C). The pressure-boosting nozzle 44 and the pressure-reducing outlet are open, while the flow-guiding structure 48 and the fluid pipeline 43 are closed. The pressure-boosting nozzle 44 continuously injects supercritical fluid into the drying chamber 42 at a flow rate of 0.5 kg / min to 2 kg / min (preferably 1 kg / min to 1.2 kg / min) for a specified duration. This ensures that any residual N2 or air inside the drying chamber 42 is completely discharged through the pressure-reducing outlet group 49. Since the centerline of the flow-guiding structure 48 is aligned with the drying chamber... The center lines of chamber 4 coincide, and the two pressure-reducing outlet groups 49 are symmetrically arranged about the flow guiding structure 48. Therefore, the flow field during the nitrogen or air emission process is relatively balanced, so as to reduce the influence on the distribution of isopropanol liquid film on the wafer surface. The venting time here is 15s to 60s (preferably 15s to 25s). Of course, before the supercritical fluid enters the pressure boosting nozzle 44, it needs to be filtered by the supercritical fluid purification structure 35 to remove organic impurities and water in the supercritical fluid, thereby minimizing the amount of organic particles remaining on the wafer after drying and avoiding the influence of water on the drying effect.

[0060] Pressure boosting and holding stage: Continue to adjust the supercritical fluid density in inlet section 30 to 400 kg / m³. 3 Up to 800kg / m 3 (Preferred value: 500 kg / m) 3 Up to 600kg / m 3 The pressure increase and holding time is 40 seconds to 90 seconds. The pressure increase and holding stage includes a pressure increase stage and a holding stage. After the residual N2 or air in the drying chamber 42 is exhausted and the pressure reduction outlet is closed, the pressure increase stage is entered first, which is defined as the Step 1 stage. Supercritical fluid is injected into the drying chamber 42 through the pressure increase nozzle 44 at the flow rate of the venting stage, so that the pressure in the drying chamber 42 is increased to the holding pressure, which is 7 MPa to 20 MPa (preferably 15 MPa to 18 MPa). Then the holding stage is entered, which is defined as the Step 2 stage. The pressure in the drying chamber 42 is maintained at the holding pressure for a period of time, which is 0 seconds to 30 seconds. The supercritical fluid dissolves the isopropanol on the wafer surface with the concentration difference as the main driving force. Of course, the supercritical fluid can also dissolve acetone.

[0061] Purging stage: Adjust the density of the supercritical fluid in inlet section 30 to 200 kg / m³. 3 Up to 600kg / m 3 (Preferred value is 200kg / m) 3 Up to 400kg / m 3This stage is the main process stage, defined as Step 3. In Step 3, the pressure boosting nozzle on / off valve 38 upstream of the pressure boosting nozzle 44 is closed, putting the pressure boosting nozzle 44 in a closed state. Based on the temperature and pressure signals within the drying chamber 42 monitored by the chamber temperature sensor 40 and chamber pressure sensor 41, the flow rates of the fluid pipeline 43 and the flow guiding structure 48 are adjusted. The flow rate difference of the supercritical fluid through the fluid pipeline 43 and the flow guiding structure 48 is 0.5 kg / min to 1 kg / min (preferably 0.5 kg / min to 0.75 kg / min), ensuring that the pressure within the drying chamber 42 remains within the supercritical range. The pressure is alternately decreased and increased above the critical pressure of the critical fluid. If the supercritical fluid is carbon dioxide, the critical pressure is 7.4 MPa. This creates a stable, periodically changing purging flow field between the annular nozzle 46 and the guide structure 48, purging the wafer surface and accelerating the uniform dissolution of isopropanol by the supercritical fluid. Furthermore, since the center of the annular nozzle 46 coincides with the center of the wafer, and the centerline of the annular nozzle 46 coincides with the centerline of the guide structure 48, the supercritical fluid ejected from the annular nozzle 46 can be distributed circumferentially along the wafer and blown from the edge of the wafer towards the center before exiting from the guide structure 48 located directly above the wafer. Figure 9 As shown in the figure, the fluid velocity is relatively consistent on any circle concentric with the wafer surface, and exhibits a velocity distribution with slightly higher velocity at the edges and slightly lower velocity at the center along the wafer radius. This is consistent with the distribution of the isopropanol liquid film on the wafer surface, which is thicker at the edges and thinner at the center due to surface tension. Therefore, it is beneficial to the uniformity and consistency of drying of the entire wafer surface. The purging time in this stage is 45s to 180s. After the isopropanol liquid film on the wafer surface is completely dissolved, the isopropanol concentration detection device (not shown) on the discharge pipeline 8 feeds back to the process endpoint, causing the first on / off valve 31, the second on / off valve 34 and the chamber inlet on / off valve 36 on the supercritical fluid supply pipeline 3 to close, and the annular nozzle on / off valve 37 to close, so that the fluid pipeline 43 is in a closed state.

[0062] Depressurization and discharge stage: This stage is defined as Step 4. Both the depressurization outlet and the flow guiding structure 48 are opened to start uniform depressurization. The total discharge flow rate of the supercritical fluid through the depressurization outlet group 49 and the flow guiding structure 48 is 1 kg / min to 2 kg / min (preferably 1.5 kg / min to 2 kg / min). At this total discharge flow rate, the supercritical fluid can be directly changed from the supercritical state to the gaseous state for discharge. This avoids the supercritical fluid in the drying chamber 42 from entering the liquid state due to the adiabatic expansion process during the discharge process, which would increase the risk of wafer surface pattern collapse.

[0063] The supercritical fluid drying system provided in this embodiment, through the flow field-controlled structural design of the drying chamber 4, the stable and efficient supercritical fluid pipeline system, and the supporting process parameters and drying methods, can achieve collapse-free ultra-clean drying of nanoscale trench structures with high aspect ratio and low mechanical strength on the wafer surface. It effectively improves the shortcomings of supercritical fluid drying technology, such as poor dissolution effect, easy organic particle residue, and uneven drying. It can further shorten the process time, improve the process stability, and increase the overall production capacity of the equipment.

[0064] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A drying method using supercritical fluid as the drying medium, characterized in that, The system includes a drying chamber (4), a drying chamber (4) with multiple fluid pipes (43) installed on the bottom wall of the drying chamber (4), a flow guiding structure (48) installed on the top wall of the drying chamber (4), a drying chamber (42) formed inside the drying chamber (4), the flow guiding structure (48) and the fluid pipes (43) being connected to the drying chamber (42), an annular nozzle (46) and a support platform (45) being provided in the middle of the drying chamber (42), the support platform (45) being located directly below the flow guiding structure (48), the support platform (45) being adapted to support the element (9) to be dried, the annular nozzle (46) being connected to the multiple fluid pipes (43) respectively, and the annular nozzle (46) being adapted to surround the element (9) to be dried; a pressure boosting nozzle (44) is also installed on the bottom wall of the drying chamber (4), and two pressure reducing outlet groups (49) are opened on the top wall of the drying chamber (4); The drying method is as follows: Place the element to be dried (9): Place the element to be dried (9) on the support platform (45) in the drying chamber (42) so that the center of the element to be dried (9) coincides with the center of the annular nozzle (46), and the center line of the annular nozzle (46) coincides with the center line of the flow guiding structure (48); Voiding stage: The pressure reducing outlet group (49) and the pressure boosting nozzle (44) are in the open state, and the flow guiding structure (48) and the fluid pipeline (43) are in the closed state. Supercritical fluid is injected into the drying chamber (42) through the pressure boosting nozzle (44) along the supercritical fluid supply pipeline (3) to vent the nitrogen or air in the drying chamber (42). Pressure boosting and holding stage: The duration of continuous pressure boosting and holding includes a pressure boosting stage and a pressure holding stage. In the pressure boosting stage, the pressure reducing outlet group (49) is closed, and the supercritical fluid is continued to be injected into the drying chamber (42) through the pressure boosting nozzle (44) so ​​that the pressure in the drying chamber (42) reaches the pressure holding pressure. Then, the pressure boosting nozzle (44) is closed, and the pressure holding stage begins. Purging stage: The fluid pipeline (43) and the flow guiding structure (48) are in the open state. Supercritical fluid is introduced into the annular nozzle (46) through the fluid pipeline (43). The flow rate of the fluid pipeline (43) and the flow guiding structure (48) is adjusted according to the temperature signal and pressure signal in the drying chamber monitored by the chamber temperature sensor (40) and the chamber pressure sensor (41) respectively. The pressure in the drying chamber (42) alternately decreases and increases above the critical pressure of the fluid, so as to form a periodically changing purging flow field between the annular nozzle (46) and the flow guiding structure (48) to purge the surface of the element to be dried (9). After the purging time, the liquid film on the element to be dried (9) is completely dissolved. Pressure relief stage: The fluid pipeline (43) is closed, and the pressure reducing outlet group (49) and the flow guiding structure (48) are both open, and pressure is released at a constant speed.

2. The drying method using supercritical fluid as the drying medium according to claim 1, characterized in that, The annular nozzle (46) has a notch (461) so that the annular nozzle (46) surrounds the element to be dried (9) at a distance of 270° to 320°.

3. The drying method using supercritical fluid as the drying medium according to claim 1, characterized in that, The flow guiding structure (48) includes an umbrella-shaped flow guiding hood (481) located in the drying chamber (42) and a flow guiding pipe (482) that communicates with the flow guiding hood (481) and penetrates the top wall of the drying chamber (4).

4. A drying method using a supercritical fluid as the drying medium according to any one of claims 1-3, characterized in that, The bottom surface of the support platform (45) is provided with a through hole (451), and the drying chamber (42) is also provided with a baffle plate (47). The baffle plate (47) is located between the pressure boosting nozzle (44) and the through hole (451) to block the supercritical fluid ejected from the pressure boosting nozzle (44) from impacting the element to be dried (9).

5. The drying method using supercritical fluid as the drying medium according to claim 4, characterized in that, The centerline of the flow guiding structure (48) coincides with the centerline of the drying chamber (4), and the two pressure reducing outlet groups (49) are symmetrically arranged about the flow guiding structure (48).

6. The drying method using supercritical fluid as the drying medium according to claim 4, characterized in that, It also includes a supercritical fluid supply pipeline (3) and a supercritical fluid purification structure (35) disposed on the supercritical fluid supply pipeline (3). In the flow direction of the supercritical fluid, the pressure boosting nozzle (44) and the fluid pipeline (43) are both located downstream of the supercritical fluid purification structure (35) and are respectively connected to the supercritical fluid supply pipeline (3).

7. The drying method using supercritical fluid as the drying medium according to claim 1, characterized in that, During the pressure increase and pressure holding stage, the temperature inside the drying chamber (42) is 31°C to 200°C, and the pressure holding pressure is 7MPa to 20MPa.

8. The drying method using supercritical fluid as the drying medium according to claim 1, characterized in that, During the venting phase and the pressurization and pressure holding phase, the flow rate of the pressurizing nozzle (44) is the same, ranging from 0.5 kg / min to 2 kg / min, and / or, during the purging phase, the flow rate difference between the supercritical fluid in the fluid pipeline (43) and the flow guiding structure (48) is 0.5 kg / min to 1 kg / min, and / or, during the pressure relief and discharge phase, the total discharge flow rate of the supercritical fluid via the pressure reducing outlet group (49) and the flow guiding structure (48) is 0.5 kg / min to 1 kg / min.

9. The drying method using supercritical fluid as the drying medium according to claim 1, characterized in that, During the venting phase and / or the pressurization and pressure holding phase, the density of the supercritical fluid in the inlet section (30) of the supercritical fluid supply pipeline (3) is 400 kg / m³. 3 Up to 800kg / m 3 And / or, during the purging phase, the density of the supercritical fluid in the inlet section (30) of the supercritical fluid supply line (3) is 200 kg / m³. 3 Up to 600kg / m 3 The inlet section (30) is adjacent to the drying chamber (4).

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