A liquid tension control method for improving wafer drying efficiency

Abstract

This invention relates to a liquid tension control method for improving wafer drying efficiency, comprising: First, placing a wafer cassette connected to a oscillating mechanism into a drying tank, loading wafers into the cassette, and ensuring the drying tank and its dome are sealed together, with a small amount of gas evacuated; Second, injecting room-temperature nitrogen gas through the dome and injecting ultrapure water into the drying tank to wet the wafer surface; Third, after the wafer surface is wetted, performing the following operations: S1: Injecting a mixture of isopropanol and heated nitrogen gas into the drying tank using a dedicated integrated module, while simultaneously discharging ultrapure water at a controlled rate from the bottom of the drying tank; S2: During the ultrapure water discharge, operating the oscillating mechanism to carry the wafer in a planetary oscillation, accelerating the removal of water molecules from the wafer; Fourth, repeating the wafer drying process. This invention utilizes planetary arc-shaped oscillation drying technology to accelerate the removal of residual moisture from the wafer surface, achieving rapid wafer drying through effective control of liquid tension.

Description

Technical Field

[0001] This invention relates to the semiconductor field, and in particular to a liquid tension control method for improving wafer drying efficiency during the wafer drying process. Background Technology

[0002] In semiconductor wafer cleaning, drying technology is indispensable, and different wafer drying technologies have been developed for different wafer products. Wafer drying is the final step in the wet cleaning process, requiring effective removal of residual moisture from the wafer surface and control over surface cleanliness. Continuous optimization and efficiency improvement of drying methods are crucial aspects that wafer cleaning equipment and technology development must pay special attention to. Various methods are used in wafer drying processes, and achieving effective batch drying within a specified time affects the overall batch size and efficiency of the wafer cleaning process. Therefore, establishing an efficient wafer drying method is a particularly important aspect of current wafer wet cleaning technology development.

[0003] In the prior art, utility model patent CN204257600U discloses a cleaning tank for cleaning semiconductor wafers. During the cleaning process, it utilizes an external magnetic field to change the surface tension of the liquid. A surface tension meter monitors the liquid's surface tension value in real time and feeds the monitoring information back to a magnetizing device to control the magnetic field strength, maintaining it at a preset value. Ultimately, this stabilizes the water's surface tension at the required level, meeting the process requirements of wafer manufacturing. However, this technology requires a specially designed magnetizing device to generate the magnetic field within the cleaning tank, and its operation is complex and cumbersome. Maintaining stable water surface tension necessitates real-time control of the magnetic field strength, which increases the operational difficulty and may even affect the cleaning and drying efficiency. Therefore, there is an urgent need for a simpler and faster method to control liquid tension and improve wafer drying efficiency. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a liquid tension control method to improve wafer drying efficiency during the wafer drying process. The proposed liquid tension control method effectively controls liquid tension, achieving rapid detachment of water molecules from the wafer through comprehensive control, thus completing the rapid drying of the wafer.

[0005] To achieve the above-mentioned objectives, the technical solution provided by this invention patent is as follows:

[0006] A liquid tension control method to improve wafer drying efficiency involves using a planetary arc-shaped oscillating drying technique during the gas phase replacement process of isopropanol and nitrogen to remove residual moisture from the wafer surface. The method includes the following steps:

[0007] The first step is to load multiple wafers into the wafer box, place the wafer box on the swing mechanism, and put the swing mechanism carrying the wafers into the drying tank; merge the dome of the drying equipment with the drying tank, and maintain the airtightness of the merged chamber, and evacuate the trace amount of gas in the chamber.

[0008] The second step is to inject ultrapure water into the drying tank and simultaneously inject room temperature nitrogen gas through the dome of the top cover, so that the surface of the ultrapure water injected into the drying tank exceeds the top of the wafer to wet the surface of the wafer. During the wetting process, room temperature nitrogen gas is continuously injected into the drying tank.

[0009] Third, after the ultrapure water has completely wetted the surface of the wafer, stop the injection of nitrogen gas at room temperature and perform the following operations:

[0010] S1: Using a dedicated integrated module, a mixture of isopropanol and heated nitrogen is injected into the drying tank from the dome of the top cover, and the ultrapure water in the drying tank is discharged from the bottom at a controlled rate.

[0011] S2: As the ultrapure water level continues to drop, the oscillating mechanism described above carries the wafers in a planetary oscillation during the ultrapure water discharge process, causing each wafer to produce an arc-shaped periodic small-angle motion. During the oscillation, a stretching phenomenon occurs at the contact point between the ultrapure water level and the wafer surface. The tension T1 of the ultrapure water liquid phase is increased by the stretching, while the surface tension T2 formed by the isopropanol gas phase and the ultrapure water liquid phase is decreased by the stretching. The isopropanol liquid film is stretched and thinned by the tension and oscillation. The ultrapure water film is stretched and thinned, and the water molecules in the thinned water film move laterally faster. The liquid tension control makes the water molecules on the wafer detach faster.

[0012] The fourth step involves operating the oscillating mechanism to continuously oscillate the wafer cassette until the ultrapure water is discharged to a level below the wafer cassette, completing the first stage of drying. Check if repeated cleaning and drying are necessary. If so, repeat steps two and three to perform the second and subsequent stages of drying until the wafer drying is complete.

[0013] In the third step, the wafer cassette, driven by the oscillating mechanism, performs a regular oscillating motion within the drying tank, causing the wafers arranged inside the wafer cassette to oscillate regularly, reciprocating symmetrically within an inclined angle with the center of the wafer as the axis.

[0014] In a further structural design, the swinging mechanism includes a drive motor, a sliding rail, a sliding block, a shaft-connected rail, and an L-shaped swing arm. The sliding rail is arranged parallel to the shaft-connected rail and is located above the shaft-connected rail. The sliding block is slidably mounted on the sliding rail. The drive motor drives the sliding block to reciprocate on the sliding rail to function as a linear robot. At least two L-shaped swing arms are provided. Each L-shaped swing arm includes a first arm and a second arm arranged in parallel. The upper part of the first arm has a sliding groove along its length. A sliding wheel is correspondingly mounted on the sliding block and installed in the sliding groove. The lower end of the first arm is axially mounted to the connection point on the shaft-connected rail. The lower end of the second arm has a wafer cassette support area.

[0015] In a further structural design, the linear robot moves back and forth, driving the L-shaped swing arm to rotate with its axis fixed, forming an arc-shaped oscillation pattern with its axis fixed.

[0016] In the third step of the wafer oscillation process described above, the tilted wafer experiences downward flow of water molecules, causing the liquid level to slowly drop. The isopropanol and hot nitrogen mixture follows closely behind. The oscillation widens the interface angle between the water molecules, resulting in an angle greater than 90 degrees between the wafer surface and the liquid surface. This makes it easier for water molecules to peel off the wafer surface. The reciprocating operation accelerates the peeling speed and enhances the peeling effect. During the wafer oscillation process, the upper part of the wafer is a dry area, and the lower part is a wetted area. At the junction of the liquid surface and the wafer, a thicker water film is generated in the dry area due to the Marangoni effect. The surface tension of the isopropanol gas phase and the ultrapure water liquid phase is T2, while the surface tension of the DIW liquid phase is T1. During oscillation, the isopropanol liquid film is stretched and thinned by the tension and oscillation. The water molecules within the stretched water film move laterally more quickly, accelerating the detachment of water molecules.

[0017] In a further structural design, the movement and positioning method of the swing mechanism is as follows:

[0018] When the L-shaped swing arm rotates with its axis fixed during forward and backward movement, the linear robot is equipped with three positioning sensors to detect the corresponding swing position during reciprocating forward and backward movement:

[0019] The position swinging towards the front is defined as A0, the position of the center stationary normal is defined as A1, and the position swinging towards the rear is defined as A2.

[0020] During wafer oscillation, the oscillation action corresponds to the phase, and the position of the center stationary normal is located at point A1. The relative phase angle between the wafer oscillation and the phase is 0 degrees.

[0021] The position of the wafer swinging towards the front is defined as A0, and the corresponding relative phase angle of the wafer swing is +θ degrees, where 2° < θ < 15°.

[0022] The position of the back-end swing is defined as A2, and the corresponding relative phase angle of the wafer swing is -θ degrees, where 2° < θ < 15°.

[0023] In a further structural design, the isopropanol and heated nitrogen mixture in the third step is made of a dedicated integrated module, which is transmitted to the dome of the upper cover and sprayed downwards into the drying tank. Isopropanol and water molecules evaporate in the gas phase and move upwards, while water molecules move downwards under the control of tension. Ultrapure water is injected and discharged from the bottom of the drying tank.

[0024] In a further structural design, the dedicated integrated module structure includes an isopropanol inlet pipeline, a circulating ultrapure water inlet pipeline, a circulating ultrapure water outlet pipeline, a heating nitrogen inlet pipeline, a mixing tank, and a mixed gas-liquid coexistence liquid outlet pipeline. The mixing tank structure includes an outer shell and a mixing tank. The outer shell is a box-shaped structure with a tank door panel, and at least one mixing tank is located inside the outer shell. An isopropanol inlet port is located near the bottom of the front side wall of the outer shell, which connects to the isopropanol inlet pipeline. An ultrapure water inlet port and an ultrapure water outlet port are located on one side wall of the outer shell, respectively connecting to the circulating ultrapure water inlet pipeline and the circulating ultrapure water outlet pipeline. A heating nitrogen inlet port is located on the rear side wall of the outer shell, which connects to the heating nitrogen inlet pipeline. A mixed gas-liquid coexistence liquid outlet port is also located on the rear side wall of the outer shell. The output port is connected to one end of the mixed gas-liquid coexisting liquid output pipeline, and the other end of the mixed gas-liquid coexisting liquid output pipeline is connected to the dome of the upper cover to transport the isopropanol and heated nitrogen mixture into the drying tank. The mixing tank is cylindrical in shape and has a three-layer structure inside, including a vortex mixing channel, a buffer reflux tank, and a hot water bath area. The vortex mixing channel is an inverted conical cavity set in the center of the mixing tank. The tank inlet is located at the center of the bottom of the mixing tank, and the tank outlet is located at the center of the top of the mixing tank. The tank inlet is connected to the isopropanol input port to receive isopropanol input into the vortex mixing channel. The buffer reflux tank inside the mixing tank is connected to the heated nitrogen input port to receive heated nitrogen. The hot water bath area inside the mixing tank is connected to the ultrapure water input port and ultrapure water output port to receive circulating ultrapure water. The tank outlet is connected to the mixed gas-liquid coexisting liquid output port.

[0025] The liquid tension control method of the present invention, which can improve the efficiency of wafer drying, also involves a safety control method for the supply of a mixture of isopropanol and hot nitrogen: determining the required target for controlling the mixed nitrogen gas / isopropanol mixture--→ confirming and controlling the isopropanol supply--→ confirming exhaust control--→ confirming cleanliness detection control--→ performing mixing confirmation control--→ corresponding drying action execution output confirmation--→ executing drying output.

[0026] In the liquid tension control method of this invention that can improve wafer drying efficiency, when the liquid surface rises and falls during the arc-shaped oscillation drying process, it is necessary to control the temperature of the isopropanol liquid. If it is at room temperature, it is controlled at 25 degrees Celsius, which is set as isopropanol room temperature control. If it is at high temperature, it is controlled at 60 degrees Celsius (controlling close to the critical state). The nitrogen gas temperature is controlled at 30 degrees Celsius if it is at room temperature, which is set as nitrogen room temperature control. If it is at high temperature, it is controlled at 120 degrees Celsius. Stable control is achieved by heating at high temperatures.

[0027] Based on the above technical solution, the ship pressure pipeline chemical refueling system of the present invention has achieved the following technical effects through practical application:

[0028] 1. The liquid tension control method of this invention, which improves wafer drying efficiency, achieves liquid tension control through two simultaneous operations, thereby efficiently completing the wafer drying process. Firstly, a dedicated integrated module is used to input isopropanol and heated nitrogen gas, thereby increasing the temperature and purity of the isopropanol. The low liquid tension of high-purity isopropanol accelerates the removal of moisture from the wafer. Secondly, a oscillating mechanism is used to create a small-angle oscillation of the wafer, causing a regular change in the angle between the ultrapure water and the wafer. This alters the liquid tension at both ends of the interface and thins the ultrapure water film adhering to the wafer, accelerating the removal of water molecules from the wafer surface and significantly improving drying efficiency.

[0029] 2. In the liquid tension control method of the present invention that can improve the drying efficiency of wafers, when the oscillating mechanism drives the wafer cassette to oscillate, the oscillating wafer tilts, water molecules flow downwards, causing the ultrapure water liquid level to drop slowly, and the mixture of isopropanol and hot nitrogen follows the ultrapure water liquid level to drop. The water molecule interface angle is widened by the oscillation, so that the angle between the wafer surface and the liquid surface is greater than 90 degrees, making the water film tightly attached to the wafer surface thinner, and making it easier for water molecules in the water film to peel off the wafer surface. Through the reciprocating oscillation operation, the peeling speed of water molecules on the wafer surface is accelerated, thereby enhancing the peeling effect.

[0030] 3. The liquid tension control method of the present invention improves the drying speed of wafer products during the drying process by improving and optimizing the drying airflow path, thereby improving the drying efficiency. By modifying the path of isopropanol and hot nitrogen airflow, a combined effect is achieved, thereby improving the drying efficiency and achieving the optimal drying efficiency ratio in the same amount of time.

[0031] 4. In the liquid tension control method of the present invention, a dedicated integrated module is designed to provide isopropanol and heated nitrogen. By constructing a mixed liquid pressurization, the diffusion and distribution capability of IPA / N2 is improved, thereby enhancing the drying capability in Marangoni and improving the ability of tension to remove water molecules and refine the distribution of organic solvents on the wafer surface. Specifically, in the integrated module, the heating control and temperature holding special component connected to the mixing tank module and the heated nitrogen source component work together to increase the control efficiency of heated nitrogen, and stably achieve comprehensive heating and auxiliary heat preservation of nitrogen. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the wafer drying process in a liquid tension control method for improving wafer drying efficiency according to the present invention.

[0033] Figure 2 This is a schematic diagram of the placement of the wafer box in the drying equipment in a liquid tension control method that can improve wafer drying efficiency according to the present invention.

[0034] Figure 3 This is a schematic diagram of the initial state of the drying process in a liquid tension control method for improving wafer drying efficiency according to the present invention.

[0035] Figure 4 This is a schematic diagram of the intermediate state of the drying process in the liquid tension control method for improving wafer drying efficiency according to the present invention.

[0036] Figure 5 This is a schematic diagram of the final state of the drying process in a liquid tension control method for improving wafer drying efficiency according to the present invention.

[0037] Figure 6 This is a schematic diagram of the installation state of the oscillating device and the wafer cassette in a liquid tension control method that can improve wafer drying efficiency according to the present invention.

[0038] Figure 7 This is a schematic diagram of the oscillating device in a liquid tension control method for improving wafer drying efficiency according to the present invention.

[0039] Figure 8 This is a schematic diagram of the oscillation state of the wafer cassette in a liquid tension control method that can improve wafer drying efficiency according to the present invention.

[0040] Figure 9This is a schematic diagram illustrating different states of a wafer when it oscillates in a wafer cassette, as described in the liquid tension control method of this invention, which can improve wafer drying efficiency.

[0041] Figure 10 This is a schematic diagram of the connection between the liquid surface and the wafer in a wafer oscillating and tilting state in a liquid tension control method that can improve wafer drying efficiency according to the present invention.

[0042] Figure 11 This is a schematic diagram illustrating the liquid tension change under wafer oscillation and tilting conditions in a liquid tension control method that can improve wafer drying efficiency according to the present invention.

[0043] Figure 12 This is a schematic diagram illustrating the principle of increased water flow due to changes in liquid tension in a liquid tension control method for improving wafer drying efficiency according to the present invention.

[0044] Figure 13 This is a schematic diagram of the structure and piping connection of a dedicated integrated module in a liquid tension control method for improving wafer drying efficiency according to the present invention. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, so as to more clearly understand its structure and operation, but this should not be construed as limiting the scope of protection of the present invention.

[0046] This invention relates to a drying technology that can be integrated into batch wafer wet cleaning equipment, focusing on a transformation of the process principle involved in drying wafers. The drying process of this invention further optimizes the method by which the organic solvent isopropanol (IPA) carries away residual moisture from the wafer surface during the gas-phase replacement process of nitrogen (N2). This drying method corresponds to the traditional Marangoni wafer drying technology, employing a two-phase misalignment movement of isopropanol solvent and water molecules to achieve tension diffusion and vertical lifting effects. Utilizing the tension difference between water molecules and isopropanol molecules, moisture is detached from the wafer surface.

[0047] like Figure 1 As shown, the method of the present invention is a technical optimization based on Marangoni wafer drying technology. Its purpose is to remove residual moisture from the wafer surface using isopropanol (IPA) through a planetary arc-shaped oscillating drying technique during the wafer drying process, when the organic solvent isopropanol and heated nitrogen gas phase replace the ultrapure water liquid phase. The method of the present invention is applied in wafer drying equipment and specifically includes the following steps:

[0048] The first step involves loading multiple wafers into a wafer cassette, placing the cassette on a swing mechanism, and then inserting the swing mechanism carrying the wafer cassette into the drying tank. The top dome of the drying equipment is then joined to the drying tank, maintaining a tight seal. Any remaining trace gases within the tank are evacuated. This step achieves simultaneous cleaning and drying of multiple wafers by placing them together in the wafer cassette, thus improving efficiency. The wafer cassette is positioned on a dedicated swing mechanism, which extends partially into the drying tank, creating a micro-vacuum environment within the tank. This ensures that the wafer cleaning and drying process takes place in a relatively closed and safe environment.

[0049] The second step involves injecting ultrapure water into the drying tank while simultaneously injecting room-temperature nitrogen gas through the dome of the top cover. This ensures the ultrapure water level in the tank exceeds the top edge of the wafer, wetting the wafer surface. During this wetting process, room-temperature nitrogen gas is continuously injected into the drying tank. This step minimizes the oxygen content within the drying tank, thereby reducing the impact of oxidation on the wafer surface.

[0050] Third, after the ultrapure water has completely wetted the surface of the wafer, stop the injection of nitrogen gas at room temperature and perform the following operations:

[0051] S1: Using a dedicated integrated module, a mixture of isopropanol and heated nitrogen is injected into the drying tank from the dome of the top cover, and the ultrapure water in the drying tank is discharged from the bottom at a controlled rate.

[0052] S2: As the ultrapure water level continues to drop, the oscillating mechanism described above, during the ultrapure water discharge process, carries the wafers to form a planetary oscillation, causing each wafer to produce an arc-shaped periodic small-angle motion. During the oscillation, a stretching phenomenon occurs at the contact point between the ultrapure water level and the wafer surface. The surface tension T1 of the ultrapure water phase is increased by the stretching, while the surface tension T2 formed by the isopropanol gas phase and the ultrapure water phase is decreased by the stretching. The isopropanol liquid film is stretched and thinned by the tension and oscillation. The ultrapure water film is also stretched and thinned. Water molecules in the thinner water film move laterally faster. Liquid tension control causes water molecules on the wafer to detach more quickly.

[0053] This step, as the core of liquid tension control, promotes the detachment of residual water molecules from the wafer surface through two aspects: First, the injection of a heated nitrogen and isopropanol (IPA) mixture maximally purifies the isopropanol, thereby reducing the liquid tension at the interface between isopropanol and ultrapure water, and the heating of nitrogen further evaporates the water molecules. Second, during the descent of the ultrapure water level, the wafer is continuously and periodically oscillated by the oscillating mechanism. This stretches and thins the water film at the interface between the ultrapure water and the wafer. Under the influence of liquid tension, water molecules in the thinned water film on the wafer accelerate towards the ultrapure water surface, thus accelerating their detachment from the wafer surface. This comprehensive control of liquid tension achieves the overall effect of accelerating wafer drying.

[0054] The fourth step involves operating the oscillating mechanism to continuously oscillate the wafer cassette until the ultrapure water is discharged to a level below the wafer cassette, completing the first stage of drying. Check if repeated cleaning and drying are necessary. If so, repeat steps two and three to perform the second and subsequent stages of drying until the wafer drying is complete.

[0055] In the liquid tension control method of the present invention that can improve wafer drying efficiency, such as Figure 3 , Figure 4 and Figure 5 As shown, during the drying process, through Figure 2 At point A, a mixture of isopropanol and heated nitrogen (1) is injected into the drying tank. This mixture is sprayed downwards, causing isopropanol and water molecules (gas phase 2) to evaporate and move upwards, while water molecules (liquid phase 3) move downwards under surface tension. Figure 2 In the diagram, B represents the liquid discharged from the bottom of the drying tank (4), which primarily consists of ultrapure water. For example... Figure 2 As shown in the figure, during the liquid discharge process, the wafer cassette performs a regular oscillating motion driven by the oscillating mechanism, causing the wafers arranged inside the wafer cassette to oscillate regularly, reciprocating symmetrically within an inclined angle about the wafer center as an axis. The specific motion is as follows: Figure 7 and Figure 8 As shown.

[0056] The aforementioned isopropanol and heated nitrogen mixture is made by a dedicated integrated module. The dedicated integrated module prepares and transports the isopropanol and heated nitrogen mixture to the dome of the upper cover, and then sprays it downward into the drying tank. In the drying tank, isopropanol and water molecules evaporate in the gas phase and move upward, while water molecules move downward under the control of tension. The liquid containing ultrapure water is injected and discharged from the bottom of the drying tank.

[0057] like Figure 13As shown, the aforementioned dedicated integrated module structure includes an isopropanol input pipeline 16, a circulating ultrapure water input pipeline, a circulating ultrapure water output pipeline, a heating nitrogen input pipeline 17, a mixing tank 15, and a mixed gas-liquid coexisting liquid output pipeline 18. The mixing tank 15 includes an outer shell and a mixing tank. The outer shell is a box-shaped structure with a tank door panel, and at least one mixing tank is located inside the outer shell. An isopropanol input port is located near the bottom of the front side wall of the outer shell, which is connected to the isopropanol input pipeline 16. An ultrapure water input port and an ultrapure water output port are located on one side wall of the outer shell, which are respectively connected to the circulating ultrapure water input pipeline and the circulating ultrapure water output pipeline. A heating nitrogen input port is provided on the rear side wall of the housing, which is connected to the heating nitrogen input pipeline 17. A mixed gas-liquid coexistence body output port is also provided on the rear side wall of the housing, which is connected to one end of the mixed gas-liquid coexistence liquid output pipeline 18. The other end of the mixed gas-liquid coexistence liquid output pipeline 18 is connected to the dome 13 of the upper cover to deliver the mixture of isopropanol and heating nitrogen into the drying tank 12. The swing mechanism 14 carries a wafer cassette and places the wafer cassette inside the drying tank 12. The mixing tank is cylindrical in shape and has a three-layer structure inside, including a vortex mixing channel, a buffer reflux tank, and a hot water bath area. The vortex mixing channel is an inverted conical cavity located at the center of the mixing tank. The tank inlet is located at the center of the bottom of the mixing tank, and the tank outlet is located at the center of the top of the mixing tank. The tank inlet is connected to the isopropanol input port to receive isopropanol input into the vortex mixing channel. The buffer reflux tank is connected above the heating nitrogen input port to receive heating nitrogen. The hot water bath area is connected to the ultrapure water input port and ultrapure water output port to receive circulating ultrapure water. The tank outlet is connected to the output port of the mixed gas-liquid coexistence.

[0058] In the liquid tension control method of this invention that can improve wafer drying efficiency, during the wafer oscillation process, water molecules flow downwards on the tilted wafer, causing the liquid surface to slowly drop. The mixture of isopropanol and hot nitrogen follows the liquid surface downwards. The water molecule interface angle is widened by the oscillation, making the angle between the wafer surface and the liquid surface greater than 90 degrees. Water molecules are more easily peeled off the wafer surface. The reciprocating operation accelerates the peeling speed of water molecules on the wafer surface and enhances the peeling effect. The principle is as follows: Figure 9 , Figure 10 and Figure 11As shown, during the wafer oscillation process, the upper part of the wafer is a dry area, and the lower part is a wetted area. At the junction of the liquid surface and the wafer, a thicker water film is formed in the dry area due to the Marangoni effect. The surface tension of the isopropanol (IPA) vapor phase and the ultrapure water (DIW) liquid phase is T2, and the surface tension of the ultrapure water (DIW) liquid phase is T1. During oscillation, the isopropanol liquid film is stretched and thinned by the tension and oscillation. The water molecules within the stretched water film move laterally more quickly, accelerating the detachment of water molecules. Figure 12 As shown.

[0059] In the liquid tension control method of the present invention that can improve wafer drying efficiency, such as Figure 6 and Figure 7 As shown, the oscillation motion of the wafer cassette D carrying the wafers is achieved by a dedicated oscillation mechanism C. The oscillation mechanism C includes a drive motor 5, a sliding rail 6, a sliding block 7, a shaft-connected rail 8, and an L-shaped swing arm 9. The sliding rail 6 is parallel to the shaft-connected rail 8 and is located above the shaft-connected rail 8. The sliding block 7 is slidably mounted on the sliding rail 6. The drive motor 5 drives the sliding block 7 to reciprocate on the sliding rail 6 to function as a linear robot. At least two L-shaped swing arms 9 are provided, each including a first arm and a second arm arranged in parallel. The upper part of the first arm has a sliding groove 10 along its length, and a corresponding sliding wheel is mounted on the sliding block within the sliding groove 10. The lower end of the first arm is axially mounted to a connection point on the shaft-connected rail, and the lower end of the second arm has a wafer cassette carrying area 11.

[0060] The wafer cassette, carrying the wafers, performs a regular oscillating motion driven by the oscillating mechanism C. A linear robot moves back and forth, driving an L-shaped swing arm to rotate around a fixed axis, forming a fixed-axis arc-shaped oscillation configuration. The reciprocating back-and-forth movement of the linear robot drives the L-shaped swing arm in an arc-shaped oscillation motion pattern. The movement and positioning method of the oscillation mechanism is as follows:

[0061] When the L-shaped swing arm rotates with its axis fixed during forward and backward movement, the linear robot is equipped with three positioning sensors to detect the corresponding swing position during reciprocating forward and backward movement:

[0062] The position swinging towards the front is defined as A0, the position of the center stationary normal is defined as A1, and the position swinging towards the rear is defined as A2.

[0063] When a wafer oscillates, it performs an oscillation motion corresponding to the phase. The position of the center stationary normal is located at point A1, and the relative phase angle between the wafer oscillations is 0 degrees.

[0064] The position of the wafer swinging towards the front is defined as A0, and the corresponding relative phase angle of the wafer swing is +θ degrees, where 2° < θ < 15°.

[0065] The position of the back-end swing is defined as A2, and the corresponding relative phase angle of the wafer swing is -θ degrees, where 2° < θ < 15°.

[0066] In selecting the oscillation angle θ, if the oscillation amplitude is less than 2°, it will not reduce the water film thickness and thus increase the liquid tension. If the oscillation amplitude is greater than 15°, it will cause the wafers to wobble or even move, leading to collisions and damage. In practical applications, a feasible oscillation amplitude angle θ is ±2.54 degrees, thus achieving the optimal drying effect.

[0067] The liquid tension control method of the present invention, which can improve the efficiency of wafer drying, also involves a safety control method for the supply of a mixture of isopropanol and hot nitrogen: determining the required target for controlling the mixed nitrogen gas / isopropanol mixture--→ confirming and controlling the isopropanol supply--→ confirming exhaust control--→ confirming cleanliness detection control--→ performing mixing confirmation control--→ corresponding drying action execution output confirmation--→ executing drying output.

[0068] In the liquid tension control method of this invention that can improve wafer drying efficiency, when the liquid surface rises and falls during the arc-shaped oscillation drying process, it is necessary to control the temperature of the isopropanol liquid. If it is at room temperature, it is controlled at 25 degrees Celsius, which is set as isopropanol room temperature control. If it is at high temperature, it is controlled at 60 degrees Celsius (controlling close to the critical state). The nitrogen gas temperature is controlled at 30 degrees Celsius if it is at room temperature, which is set as nitrogen room temperature control. If it is at high temperature, it is controlled at 120 degrees Celsius. Stable control is achieved by heating at high temperatures.

[0069] This invention provides a liquid tension control method to improve wafer drying efficiency. This method improves the drying efficiency by optimizing the airflow path, thereby enhancing the effective drying of wafer products. Through path modification of isopropanol and hot nitrogen gas flow, a combined effect is achieved, resulting in a perfect relative value between drying efficiency and time. The method enhances the diffusion and distribution capabilities of IPA / N2 by constructing a mixed liquid pressurization system on the wafer drying equipment, thereby strengthening the Marangoni drying capability and improving the ability of tension-removed water molecules to distribute the refined organic solvent on the wafer surface. Furthermore, the special temperature-holding component for heating control connected to the mixing tank module works in conjunction with the heated nitrogen source component to increase the control efficiency of the heated nitrogen.

Claims

1. A liquid tension control method for improving wafer drying efficiency, characterized in that, The method includes the following steps: The first step is to load multiple wafers into a wafer box, place the wafer box on a swing mechanism, and put the swing mechanism carrying the wafers into a drying tank; then, merge the dome of the drying equipment with the drying tank, maintain the airtightness of the merged chamber, and evacuate the trace amount of gas inside the chamber. The second step is to inject ultrapure water into the drying tank and simultaneously inject room temperature nitrogen gas through the dome of the top cover, so that the surface of the ultrapure water injected into the drying tank exceeds the top of the wafer to wet the surface of the wafer. During the wetting process, room temperature nitrogen gas is continuously injected into the drying tank. Third, after the ultrapure water has completely wetted the surface of the wafer, stop the injection of nitrogen gas at room temperature and perform the following operations: S1: Using an integrated module, a mixture of isopropanol and heated nitrogen is injected into the drying tank from the top dome, and the ultrapure water in the drying tank is discharged from the bottom at a controlled rate. S2: As the ultrapure water level continues to drop, the oscillating mechanism described above carries the wafers in a planetary oscillation during the ultrapure water discharge process, causing each wafer to produce an arc-shaped periodic small-angle motion. During the oscillation, a stretching phenomenon occurs at the contact point between the ultrapure water level and the wafer surface. The surface tension T1 of the ultrapure water phase is increased by the stretching, while the surface tension T2 formed by the isopropanol gas phase and the ultrapure water phase is decreased by the stretching. The isopropanol liquid film is stretched and thinned by the tension and oscillation. The ultrapure water film is stretched and thinned, and the water molecules in the thinned water film move laterally faster. Controlling the liquid tension causes the water molecules on the wafer to detach more quickly. The fourth step involves operating the oscillating mechanism to continuously oscillate the wafer cassette until the ultrapure water is discharged to a level below the bottom of the wafer cassette, completing the first stage of drying. Check if the cleaning and drying process needs to be repeated. If so, repeat steps two and three to perform the second and subsequent stages of drying until the wafer drying is complete. In the third step, the integrated module structure includes an isopropanol input pipeline, a circulating ultrapure water input pipeline, a circulating ultrapure water output pipeline, a heating nitrogen input pipeline, a mixing tank, and a mixed gas-liquid coexisting liquid output pipeline. The mixing tank structure includes an outer shell and a mixing tank. The outer shell is a box-shaped structure with a tank door panel, and at least one mixing tank is provided inside the outer shell. The front side wall of the outer casing has an isopropanol inlet port near the bottom, which is connected to the isopropanol inlet pipeline. An ultrapure water inlet port and an ultrapure water outlet port are located on one side wall of the outer casing, respectively connected to the circulating ultrapure water inlet pipeline and the circulating ultrapure water outlet pipeline. A heated nitrogen inlet port is located on the rear side wall of the outer casing, which is connected to the heated nitrogen inlet pipeline. A mixed gas-liquid coexistence liquid outlet port is also located on the rear side wall of the outer casing, connected to one end of a mixed gas-liquid coexistence liquid outlet pipeline. The other end of the mixed gas-liquid coexistence liquid outlet pipeline is connected to the dome of the upper cover to transport the mixture of isopropanol and heated nitrogen into the drying tank. The mixing tank is cylindrical in shape and has a three-layer structure inside, including a vortex mixing channel, a buffer reflux tank, and a hot water bath area. The vortex mixing channel is an inverted conical cavity located at the center of the mixing tank. The tank inlet is located at the center of the bottom of the mixing tank, and the tank outlet is located at the center of the top of the mixing tank. The tank inlet is connected to the isopropanol input port to receive isopropanol input into the vortex mixing channel. The buffer reflux tank is connected above the heating nitrogen input port to receive heating nitrogen. The hot water bath area is connected to the ultrapure water input port and ultrapure water output port to receive circulating ultrapure water. The tank outlet is connected to the output port of the mixed gas-liquid coexistence.

2. The liquid tension control method for improving wafer drying efficiency according to claim 1, characterized in that, In the third step, the wafer cassette, driven by the oscillating mechanism, performs a regular oscillating motion within the drying tank, causing the wafers arranged inside the wafer cassette to oscillate regularly. During the oscillation, the wafers reciprocate symmetrically within an inclined angle with the center of the wafer as the axis.

3. The liquid tension control method for improving wafer drying efficiency according to claim 2, characterized in that, The swinging mechanism includes a drive motor, a sliding rail, a sliding block, a shaft-connected rail, and an L-shaped swing arm. The sliding rail is arranged parallel to the shaft-connected rail and is located above the shaft-connected rail. The sliding block is slidably mounted on the sliding rail. The drive motor drives the sliding block to reciprocate on the sliding rail to function as a linear robot. At least two L-shaped swing arms are provided. Each L-shaped swing arm includes a first arm and a second arm arranged in parallel. The upper part of the first arm has a sliding groove along its length. A sliding wheel is correspondingly mounted on the sliding block and installed in the sliding groove. The lower end of the first arm is axially mounted to the connection point on the shaft-connected rail. The lower end of the second arm has a wafer cassette support area.

4. The liquid tension control method for improving wafer drying efficiency according to claim 3, characterized in that, The linear robot moves back and forth, driving the L-shaped swing arm to rotate with a fixed axis, forming an arc-shaped swinging pattern with a fixed axis.

5. A liquid tension control method for improving wafer drying efficiency according to claim 4, characterized in that, The movement and positioning method of the swing mechanism is as follows: When the L-shaped swing arm rotates with its axis fixed during forward and backward movement, the linear robot is equipped with three positioning sensors to detect the corresponding swing position during reciprocating forward and backward movement. When a wafer oscillates, it oscillates in a corresponding phase. The position of the center stationary normal is located at A1, and the relative phase angle between the wafer oscillations is 0 degrees. The position of the wafer swinging towards the front end is defined as A0, and the corresponding relative phase angle of the wafer swing is +θ degrees, where 2° < θ < 15°; The position of the back-end swing is designated as A2, and the corresponding relative phase angle of the wafer swing is -θ degrees, where 2° < θ < 15°.

6. The liquid tension control method for improving wafer drying efficiency according to claim 1, characterized in that, In the third step, the mixture of isopropanol and heated nitrogen is made by an integrated module and transported to the dome of the upper cover and sprayed downwards into the drying tank. Isopropanol and water molecules evaporate in the gas phase and move upwards, while water molecules move downwards under the control of tension. Ultrapure water is injected and discharged from the bottom of the drying tank.

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