Wafer surface cleaning process based on cooperation of overflow and airflow purging and liquid film sedimentation

Abstract

The invention discloses a wafer surface cleaning process based on cooperation of overflow and airflow purging and liquid film sedimentation. The wafer surface cleaning process comprises a soaking step and a drying step. On the one hand, on the basis of sedimentation of the overflow seat, cleaning liquid overflows and is discharged while the heights of the airflow nozzles and the cleaning liquid level are kept consistent all the time, and then the first airflow and the second airflow blow and cooperate at the same time, so that the liquid level surface of the junction part is kept perpendicular to the surface of the wafer, and a liquid film which fully covers and is not influenced by liquid level fluctuation is formed; the tension formed by the liquid level is reduced, the occurrence rate that the liquid level climbs along the surface of the wafer is reduced, and meanwhile, coverage is formed in cooperation with airflow, so that defect-free traceless drying of the surface of the wafer is achieved; and on the other hand, the adopted overflow mode is matched with hindrance formed by a surface liquid film, the conventional mode that the gravity of water is used as a drive to control the water surface to descend is abandoned, the same fall is kept between the overflow surface and the cleaning liquid surface, and liquid surface fluctuation caused by water head change is eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor processing, and in particular relates to a wafer surface cleaning process based on liquid film deposition in collaboration with overflow and airflow blowing. Background Art

[0002] In the semiconductor industry, after the wet process of the wafer, it is usually necessary to clean and dry the residual chemicals on the wafer process surface to ensure that the chemicals on the wafer process surface are clean and the number of particles after drying meets the requirements of subsequent processes.

[0003] Currently, the traditional cleaning process is: (1) soaking; (2) drying, in which the wafer is loaded onto a carrier and immersed in a cleaning tank containing a cleaning solution to complete the soaking; and the drying methods mainly include high-purity nitrogen drying and Marangoni drying. However, in the above drying process, there are the following technical defects: 1. High-purity nitrogen drying is used, which is mainly based on the unloading of the soaking liquid. The exposed part of the wafer is blown and dried with high-purity nitrogen. Although it seems simple and efficient, when the gas acts on the location where there are large water droplets on the wafer surface, it will cause water droplets to splash, causing water droplets to be reintroduced into the dried location. After drying again, water marks will be formed. These water marks are very difficult to clean. If deep chemical liquid cleaning is not performed, the wafer will be scrapped. 2. The drying method based on the Marangoni principle mainly utilizes the contact between two liquids with different surface tensions. The surface liquid film (also known as IPA liquid film or isopropyl alcohol liquid film) keeps flowing from the area with low surface tension to the area with high surface tension. At the same time, during the discharge of the cleaning liquid, as the liquid level drops, the water flow is kept converging in the middle. Therefore, the liquid film remains in contact with the wafer surface, and as the wafer is exposed, the contacted liquid film evaporates and carries away the residual water droplets on the surface, achieving traceless drying. However, in actual operation, the speed of liquid level drop varies with the change of pressure, which greatly increases the probability of liquid level fluctuation. Due to liquid level fluctuation, the cleaning liquid easily climbs upward along the surface of the wafer to be cleaned and forms a slope angle. Therefore, the probability of water marks forming on the wafer surface is also greatly increased. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an improved wafer surface cleaning process based on liquid film deposition in collaboration with overflow and airflow blowing.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: A wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge includes a soaking step and a drying step, wherein the soaking step immerses a carrier loaded with wafers in a cleaning tank containing a cleaning liquid, and the drying step includes: S1, liquid level drops The overflow seat movably installed in the cleaning tank descends and penetrates into the cleaning liquid. When a liquid level difference is formed between the overflow port and the liquid surface of the cleaning liquid, the cleaning liquid flows into the overflow seat and is discharged from the cleaning tank based on the overflow seat. S2. Liquid film formation As the overflow seat settles, the wafer surface gradually becomes exposed above the liquid level, forming an interface and an exposed portion with the liquid level. Simultaneously, an airflow nozzle fixedly mounted above the overflow seat operates. The airflow ejected by the airflow nozzle includes a first airflow blowing obliquely from top to bottom toward the interface, and a second airflow located above the first airflow and blowing toward the exposed portion. The airflow is formed by vaporizing liquid and is volatile. The first and second airflows simultaneously sweep and cooperate to keep the liquid level at the interface perpendicular to the wafer surface, and form a liquid film layer that covers the entire surface from the interface to the overflow port. S3, seamless drying As the area of the exposed part gradually increases, with the continuous assistance of the liquid film layer, the second airflow covers the entire exposed part to form air drying, and the gas on the surface of the wafer evaporates to carry away the residual water droplets on the surface to achieve seamless drying.

[0006] Preferably, in step S1, the overflow seat forms a notch extending horizontally from the side of the wafer, with the overflow surface formed at the bottom of the notch. In short, this method, which abandons the conventional method of using gravity to drive the water level downward, maintains the same height difference between the overflow surface and the cleaning liquid level, eliminating liquid level fluctuations caused by water level differences (or, alternatively, eliminating the impact of water level fluctuations by steadily descending the water level).

[0007] According to one specific embodiment and preferred aspect of the present invention, an inner extension plate extends from the bottom of the notch into the overflow seat, and an overflow dam extends upward from the inner end of the inner extension plate. The overflow dam is provided with multiple dam openings. As the overflow dam settles, the cleaning liquid overflows from the dam openings into the overflow seat. The inward movement of the overflow dam increases the span of the liquid film layer, reducing the probability of the liquid surface floating at the interface caused by the overflow. At the same time, during the sedimentation of the overflow dam, the height of the airflow nozzle and the cleaning liquid level are maintained at a constant level, thereby maintaining the stability and reliability of the entire process.

[0008] Preferably, the inlet and outlet ends of each dam port are rounded to ensure smooth overflow, prevent backflow of the cleaning liquid due to the movement of the liquid film layer, and reduce the probability of liquid surface floating.

[0009] In some embodiments, multiple weirs are arranged side by side, spaced evenly apart, on the overflow dam. Furthermore, each weir has the same length, width, and height. The blocking provided by the dam and the diversion provided by the weirs effectively control the rate of change in the cleaning liquid level caused by overflow, further facilitating the formation of a liquid film.

[0010] According to another specific embodiment and preferred aspect of the present invention, the overflow device includes an overflow seat having an overflow chamber and an overflow outlet, a drainage pipeline connected to the liquid outlet of the overflow seat, and a power assembly for driving the overflow seat up and down. The drainage pipeline can be expanded and contracted synchronously with the rise and fall of the overflow seat. Based on the sedimentation of the overflow seat and the expansion and contraction of the drainage pipeline, the overflow rate of the cleaning liquid can be effectively controlled by controlling the sedimentation rate, thereby meeting cleaning requirements.

[0011] Preferably, the overflow chamber gradually becomes smaller from top to bottom, the liquid outlet is located at the bottom of the overflow chamber, and the drainage pipeline is a telescopic tube. Based on the shape design of the overflow chamber, it is more conducive to the rapid overflow of the overflow cleaning liquid, and the position and extension of the telescopic tube can be changed to meet the drainage needs.

[0012] Furthermore, the bottom of the overflow chamber is tilted up and down, the liquid outlet is located at the lower end of the tilt, and the telescopic tube is located directly below the liquid outlet. Based on the converging layout, overflow discharge is accelerated.

[0013] According to another specific embodiment and preferred aspect of the present invention, in step S2, the thickness of the liquid film layer gradually decreases from the interface toward the overflow port. Based on the contact formed by the airflow, a gradually thinning liquid film layer is formed to cover the entire liquid surface, thereby eliminating the water surface fluctuation caused by the overflow.

[0014] Preferably, the gas ejected from the airflow nozzle is isopropyl alcohol (IPA), and the liquid film is an IPA liquid film. The volatility of IPA is utilized to displace residual cleaning liquid on the wafer surface, enhancing drying efficiency. Simultaneously, the resulting IPA liquid film covering the cleaning liquid surface reduces the surface tension of the cleaning liquid, facilitating the stable formation of the Marangoni effect.

[0015] According to another specific embodiment and preferred aspect of the present invention, the flow rate of the first airflow is greater than the flow rate of the second airflow. Under the working condition that the height between the airflow nozzle and the cleaning liquid surface remains unchanged, the required liquid film layer is formed by the assistance of airflows at different positions, angles and flow rates.

[0016] In short, the gas ejected from the nozzle can directly act on the liquid surface, and the effective span can cover the entire intersection of the wafer surface and the water surface, thereby forming a complete and continuous liquid film. At the same time, water under normal conditions, due to the existence of surface tension, will show a climbing phenomenon at the intersection of the liquid surface and the wafer surface when the liquid level drops. The liquid film has the effect of changing the surface tension of water, reducing its surface tension, so that the climbing phenomenon is greatly weakened. This ensures that when the liquid level drops, the wafer surface passing through will not retain too much water due to the climbing phenomenon.

[0017] Preferably, in step S2, the airflow nozzle has an air inlet cavity and an air outlet cavity, wherein the air outlet cavity includes an upper cavity and a lower cavity respectively connected to the air inlet cavity, the upper cavity ejecting the second airflow, and the lower cavity ejecting the first airflow. The two airflows differ not only in flow rate but also in position and angle. Therefore, during the covering airflow purge, the liquid film layer forms a contact layer to remove water droplets from the wafer surface, thereby achieving seamless drying.

[0018] Furthermore, the volume of the lower chamber is smaller than that of the upper chamber; and / or the volume of the upper chamber is 1.5 to 5 times that of the lower chamber. By controlling the volume difference between the upper and lower chambers, the flow rates of the first and second airflows can be controlled, thereby precisely controlling the drying airflow directed toward the wafer surface and ensuring the desired liquid film layer is formed on the cleaning liquid surface.

[0019] In some specific embodiments, the outlets of both the upper and lower chambers are located above and to the side of the overflow port. The outlet of the upper chamber extends horizontally, with the secondary airflow ejected perpendicular to the wafer cleaning surface. The outlet of the lower chamber is tilted from top to bottom, with the primary airflow ejected intersecting the wafer cleaning surface and the liquid level, respectively. By employing perpendicular and intersecting airflows, and by varying the flow rates, the desired liquid film layer is formed while achieving complete coverage to prevent secondary drying marks caused by splashing water droplets.

[0020] Furthermore, the outlet ends of the upper and lower cavities are aligned vertically. Furthermore, the outlet end of the lower cavity is positioned above the middle of the liquid film layer. This alignment of the outlet ends ensures that the two airflows do not become incompatible due to the presence of gaps in the outlet ends. Furthermore, the key is to ensure that the positioning of the airflow ends, especially the outlet end of the lower cavity, forms a fully covered liquid film.

[0021] Furthermore, the wafer has a front side and a back side, each of which corresponds to a set of cleaning units. The carrier and wafer separate the cleaning tank into two relatively separate, bottom-connected front and back cleaning areas. Each cleaning unit group includes an overflow seat and an airflow nozzle. The two overflow seats descend synchronously, and the two airflow nozzles simultaneously eject gas, simultaneously cleaning the front and back sides of the wafer. Based on the barrier formed by the wafer and the carrier, the cleaning tank is divided into zones, which not only enables simultaneous cleaning of the front and back sides, but also forms relatively balanced overflow surfaces in the zones, eliminating pressure differences and interference between airflows, thereby achieving efficient and high-quality simultaneous cleaning of the front and back sides of the wafer.

[0022] Due to the implementation of the above technical solution, the present invention has the following advantages compared with the prior art: In the existing wafer cleaning drying process, if high-purity nitrogen is used for drying, it is mainly based on the unloading of the immersion liquid, and the exposed part of the wafer is blown and dried with high-purity nitrogen. On the surface, although it is simple and efficient, when the gas acts on the location where there are large water droplets on the wafer surface, it will cause water droplets to splash, causing water droplets to be reintroduced into the dried location, and water marks will be formed after being blown dry again. The water marks are very difficult to clean. If deep chemical liquid cleaning is not performed, the wafer will be scrapped. If the drying method is based on the Marangoni principle, it mainly utilizes the contact of two liquids with different surface tensions, based on the surface liquid film (also known as IPA liquid film or isopropyl alcohol liquid film) to keep flowing from the area with low surface tension to the area with high surface tension. At the same time, in the discharge of the cleaning liquid, as the liquid level drops, the water flow is kept converging to the middle. Therefore, the liquid film remains in contact with the wafer surface, and as the wafer is exposed, the contacted liquid film evaporates and is carried away. The residual water droplets on the surface are removed to achieve traceless drying; however, in actual operation, the speed of liquid level drop varies with the change of pressure, which greatly increases the probability of liquid level fluctuation. Based on the liquid level fluctuation, the cleaning liquid easily climbs up along the wafer surface to be cleaned and forms a slope angle. Therefore, the probability of water marks forming on the wafer surface is also greatly increased, etc. The present invention comprehensively designs a wafer surface cleaning process based on the liquid film sedimentation of the cooperation of overflow and air flow blowing, which cleverly solves the shortcomings and defects of the existing technology. After adopting the wafer cleaning process, first, the carrier loaded with wafers is immersed in the cleaning tank containing cleaning liquid; secondly, the overflow seat movably installed in the cleaning tank descends and penetrates into the cleaning liquid. When a liquid level difference is formed between the overflow port and the liquid surface of the cleaning liquid, the cleaning liquid flows into the overflow seat, and the cleaning liquid is discharged from the cleaning tank based on the overflow seat; then, as the overflow seat settles, The surface of the wafer is gradually exposed above the liquid level and an interface and an exposed portion are formed between the liquid level and the wafer. At the same time, the airflow nozzle fixedly installed above the overflow seat works. The airflow ejected by the airflow nozzle includes a first airflow blowing obliquely from top to bottom to the interface, and a second airflow located above the first airflow and blowing to the exposed portion. The airflow is formed by vaporization of liquid and is volatile. The first and second airflows blow and cooperate simultaneously to keep the liquid level at the interface perpendicular to the wafer surface, and form a liquid film layer covering the entirety from the interface to the overflow port. Finally, as the area of the exposed portion gradually increases, with the continuous assistance of the liquid film layer, The second airflow covers the entire exposed portion to achieve air drying, and the volatilization of the gas on the wafer surface carries away the residual water droplets on the surface to achieve seamless drying. Therefore, on the one hand, the present invention is based on the sedimentation of the overflow seat, and the height of the airflow nozzle and the cleaning liquid level is kept consistent to discharge the cleaning liquid overflow. Then, the first and second airflows are simultaneously purged and cooperated to make the liquid level surface at the junction perpendicular to the wafer surface and form a liquid film that fully covers and is not affected by liquid level fluctuations, thereby reducing the tension formed by the liquid surface and the incidence of the liquid surface climbing along the wafer surface. At the same time, the coverage formed by the airflow is coordinated to achieve defect-free and seamless drying of the wafer surface.On the other hand, the overflow method adopted, combined with the obstruction formed by the surface liquid film, not only abandons the conventional use of water gravity as a driving force to control the water level drop, but also maintains the same height difference between the overflow surface and the clean liquid surface, eliminating the liquid level fluctuation caused by the change of water level difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a wafer surface cleaning device according to the present invention (partially exploded); Figure 2 for Figure 1 A half-section diagram of Figure 3 for Figure 2 A schematic diagram of the structure at center A; Figure 4 for Figure 1 Schematic diagram of the structure of the cleaning unit; Figure 5 for Figure 4 Schematic diagram of the local structure omitted; Figure 6 for Figure 5 A magnified schematic diagram of the structure at point B in the middle; Figure 7 for Figure 4 Schematic diagram of the structure of the overflow seat and the air flow nozzle; Figure 8 for Figure 7 A half-section diagram of Among them: 1. Cleaning tank; 2. Vehicle; 3. Cleaning unit; 30. Overflow device; 300. Overflow seat; q. Overflow chamber; k. Overflow port; 301. Drain pipe; 302. Power assembly; 303. Inner extension plate; 304. Overflow dam; a. Dam port; 31. Air flow nozzle; 310. Air inlet chamber; 311. Air outlet chamber; s1. Upper chamber; s2. Lower chamber; 4. Cleaning liquid recovery tank; w. wafer. DETAILED DESCRIPTION

[0024] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0025] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0027] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0028] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0029] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0030] like Figures 1 to 8 As shown, the wafer surface cleaning process of this embodiment is based on overflow and airflow blowing collaborative liquid film sedimentation, and the cleaning equipment used includes a cleaning tank 1, a carrier 2 movably installed on the cleaning tank 1, a cleaning unit 3 installed in the cleaning tank 1 and a cleaning liquid recovery tank 4, wherein the wafer w is installed in the carrier 2, and the carrier 2 is inserted into the cleaning tank 1 up and down, and there are two groups of cleaning units 3 based on the surface of the wafer w, and the two groups of cleaning units 3 move synchronously to implement synchronous cleaning of the front and back sides of the wafer w.

[0031] Specifically, each cleaning unit 3 includes an overflow device 30 and an airflow nozzle 31. The overflow device 30 includes an overflow seat 300 having an overflow chamber q and an overflow port k, a drainage pipe 301 connected to the liquid outlet of the overflow seat 300, and a power assembly 302 that drives the overflow seat 300 up and down. The drainage pipe 301 can be expanded and contracted synchronously with the rise and fall of the overflow seat 300. Based on the sedimentation of the overflow seat 300 and the expansion and contraction of the drainage pipe 301, the overflow rate of the cleaning liquid can be effectively controlled by controlling the sedimentation speed, thereby meeting cleaning needs.

[0032] The overflow seat 300 has a notch extending horizontally from the side of the wafer, with an overflow surface formed at the bottom of the notch. In short, this system abandons the conventional method of using gravity to control the water level, while maintaining a consistent height difference between the overflow surface and the cleaning liquid level, eliminating liquid level fluctuations caused by varying water levels (or, alternatively, eliminating the effects of water level fluctuations by steadily descending the water level). An inner plate 303 extends from the bottom of the notch into the overflow seat 300. An overflow dam 304 extends upward from the inner end of the inner plate 303. Multiple weir openings a are defined on the overflow dam 304. As the overflow dam 304 descends, the cleaning liquid overflows from the weir openings a into the overflow seat 300. This inward movement of the overflow dam increases the span of the liquid film layer, reducing the probability of liquid level fluctuations at the interface caused by overflow. Furthermore, as the overflow dam descends, the height of the airflow nozzle and the cleaning liquid level remain consistent, thus maintaining a stable and reliable process.

[0033] In some embodiments, the inlet and outlet ends of each weir a have rounded corners. This ensures smooth overflow, preventing backflow of cleaning liquid due to the movement of the liquid film, and reducing the likelihood of liquid surface fluctuations. Multiple weirs a are evenly spaced and arranged side by side on the overflow dam 304; furthermore, each weir a has identical length, width, and height. The obstruction created by the dam body and the diversion provided by the weirs effectively control the rate of change in the cleaning liquid level caused by overflow, further facilitating the formation of a liquid film.

[0034] In this example, the overflow chamber q tapers downward, with the outlet located at its bottom. The drain line 301 is a telescopic tube. The design of the overflow chamber q facilitates the rapid escape of overflow cleaning liquid, while the position and extension of the telescopic tube adjust to meet drainage needs. Furthermore, the bottom of the overflow chamber q is tilted vertically, with the outlet located at the lower end of the tilt, and the telescopic tube positioned directly below the outlet. This convergent layout expedites overflow discharge.

[0035] The air flow nozzle 31 is fixedly installed above the overflow seat 300. Specifically, the air flow nozzle 31 has an air inlet cavity 310 and an air outlet cavity 311, wherein the air outlet cavity 311 includes an upper cavity s1 and a lower cavity s2 respectively connected to the air inlet cavity 310, the upper cavity s1 sprays out the second air flow, and the lower cavity s2 sprays out the first air flow. The two air flows not only have flow rate differences, but also position and angle differences. Therefore, they can meet the requirements of the contact formed by the liquid film layer in the covering air flow purge to carry away the water droplets on the wafer surface to achieve traceless drying. Furthermore, the volume of the lower cavity s2 is smaller than the volume of the upper cavity s1, and the volume of the upper cavity is 3 times the volume of the lower cavity. Based on controlling the volume difference between the upper and lower cavities, the control of the flow rate of the first and second air flows is achieved, thereby accurately controlling the air drying air flow blown to the wafer surface and ensuring the formation of the required liquid film layer on the cleaning liquid surface. The air outlet ends of the upper cavity s1 and the lower cavity s2 are both located above and to the side of the overflow port; the air outlet end of the upper cavity s1 extends in the horizontal direction, and the direction of the ejected second airflow is perpendicular to the wafer cleaning surface; the air outlet end of the lower cavity s2 is inclined from top to bottom, and the ejected first airflow intersects with the wafer cleaning surface and the liquid level surface, respectively. Vertical and intersecting airflows are used, and based on the difference in flow rates, on the one hand, the required liquid film layer is formed, and on the other hand, full coverage is formed to avoid the occurrence of secondary drying marks caused by the splashing of water droplets. The air outlet ends of the upper cavity s1 and the lower cavity s2 are aligned vertically, and further, the air outlet end of the lower cavity s2 is located above the middle of the liquid film layer. Based on the alignment of the air outlet ends, it is ensured that the two airflows will not be unable to cooperate due to the airflow formed by the air outlet ends, and the key is to form a fully covered liquid film through the position layout of the airflow ends, especially the air outlet end of the lower cavity. As for the cooperation between the first and second airflows, it is mainly reflected as follows: 1. The two airflows are purged at the same time, and the decomposition and deflection cooperate to form a covering liquid film layer, and the liquid film layer gradually becomes thinner; 2. The deflection of the second airflow is fully utilized to maintain downward coverage, so that the drying environment is the same, there is no possibility of secondary drying, and excessive purging causing damage to the wafer is avoided (because excessive IPA will damage the wafer surface).

[0036] In summary, this embodiment takes the front side or back side of the wafer W as an example for single-side cleaning, and the specific implementation process is as follows: (1) a soaking step in which the carrier loaded with the wafer is immersed in a cleaning tank containing a cleaning solution; (2) Drying step, which includes: S1, liquid level drop, which is caused by the overflow seat movably installed in the cleaning tank to go deep into the cleaning liquid. When the overflow port and the liquid surface of the cleaning liquid form a liquid level difference, the cleaning liquid flows into the overflow seat, and the cleaning liquid is discharged from the cleaning tank based on the overflow seat and returned to the cleaning liquid recovery tank; S2, the formation of the liquid film, which is formed as the overflow seat settles. The surface of the wafer is gradually exposed above the liquid level and forms an interface and an exposed portion with the liquid level. At the same time, it works based on an airflow nozzle fixedly installed above the overflow seat. The airflow ejected by the airflow nozzle includes a first airflow blowing obliquely from top to bottom to the interface, and a second airflow located above the first airflow and blowing to the exposed portion. The airflow is formed by vaporization of liquid and is volatile. The first and second airflows simultaneously sweep and cooperate to keep the liquid level at the interface perpendicular to the wafer surface, and form a liquid film layer covering the entirety from the interface to the overflow port. The liquid film layer is an isopropyl alcohol liquid film (IPA liquid film), and the thickness of the liquid film layer formed from the interface to the overflow port gradually decreases; S3, traceless drying, as the area of the exposed portion gradually increases, with the continuous assistance of the liquid film layer, the second airflow covers the entire exposed portion to form air drying, and the gas on the wafer surface evaporates and carries away the residual water droplets on the surface to achieve traceless drying.

[0037] Specifically, the flow rate of the first airflow is greater than the flow rate of the second airflow. Under the operating condition where the height between the airflow nozzle and the cleaning liquid level remains constant, airflows at different positions, angles, and flow rates assist in forming the desired liquid film layer. Simply put, the gas ejected from the nozzle directly impacts the liquid surface, effectively covering the entire intersection of the wafer surface and the water surface, thereby forming a complete, continuous liquid film. Furthermore, due to surface tension, water normally slopes at the intersection of the liquid surface and the wafer surface as the liquid level drops. The liquid film modifies the surface tension of the water, reducing it and significantly reducing this slope. This ensures that excess water remains on the wafer surface as the liquid level drops due to this slope. The gas ejected from airflow nozzle 31 is isopropyl alcohol, and the liquid film layer is an isopropyl alcohol film. The volatility of isopropyl alcohol (IPA) is utilized to displace residual cleaning liquid on the wafer surface, enhancing the drying effect. Furthermore, the resulting isopropyl alcohol film covering the cleaning liquid surface reduces the surface tension of the cleaning liquid, facilitating the stable formation of the Marangoni effect.

[0038] In addition, the present application can also implement simultaneous cleaning of the front and back sides of the wafer, and the specific implementation process is as follows: (1) A soaking step in which the carrier loaded with wafers is immersed in a cleaning tank containing a cleaning solution, wherein the cleaning tank is relatively separated by the wafers and the carrier, and the front cleaning area and the back cleaning area are connected at the bottom; (2) Drying step, which includes: S1, the liquid level drops, which is synchronized by two overflow seats movably installed in the cleaning tank. The liquid flows downward into the cleaning liquid. When a level difference is formed between the overflow port and the cleaning liquid surface, the cleaning liquid flows into the overflow seat, and the overflow seat discharges the cleaning liquid from the cleaning tank and returns to the cleaning liquid recovery tank. S2, the formation of the liquid film, which is formed as the overflow seat settles. The surface of the wafer is gradually exposed above the liquid level and forms an interface and an exposed portion with the liquid level. At the same time, each airflow nozzle fixedly installed above the overflow seat works separately. The airflow ejected by each airflow nozzle includes a first airflow blowing obliquely from top to bottom to the interface, and a second airflow located above the first airflow and blowing to the exposed portion. The airflow is formed by vaporization of liquid and is volatile. The first and second airflows simultaneously sweep and cooperate to make the liquid level surface at the interface remain perpendicular to the wafer surface, and form a liquid film layer covering the entirety from the interface to the overflow port. The liquid film layer is an isopropyl alcohol liquid film (IPA liquid film), and the thickness of the liquid film layer formed from the interface to the overflow port gradually decreases. The airflows formed by the front cleaning area and the back cleaning area are separated and do not interfere with each other; S3, traceless drying, as the area of the exposed portion gradually increases, with the continuous assistance of the liquid film layer, the second airflow covers the entire exposed portion to form air drying, and the gas on the wafer surface evaporates and carries away the residual water droplets on the surface to achieve traceless drying.

[0039] In summary, after adopting the wafer cleaning process, first, the carrier loaded with wafers is immersed in a cleaning tank containing cleaning liquid; secondly, the overflow seat movably installed in the cleaning tank descends and penetrates into the cleaning liquid. When a liquid level difference is formed between the overflow port and the liquid surface of the cleaning liquid, the cleaning liquid flows into the overflow seat, and the cleaning liquid is discharged from the cleaning tank based on the overflow seat; then, as the overflow seat settles, the wafer surface is gradually exposed above the liquid level surface and a junction and an exposed portion are formed between the liquid level surface, and at the same time, an airflow nozzle fixedly installed above the overflow seat works. The airflow ejected by the airflow nozzle includes a first airflow obliquely blown from top to bottom to the junction portion, and a second airflow located above the first airflow and blown to the exposed portion, wherein the airflow is formed by vaporization of liquid and is volatile. The first and second airflows simultaneously sweep and cooperate to make the liquid level surface at the junction portion remain perpendicular to the wafer surface, and form an overall covering liquid film layer from the junction portion to the overflow port; finally, as the area of the exposed portion gradually increases, with the continuous assistance of the liquid film layer, the second airflow nozzle The flow covers the entire exposed part to form air drying, and the volatilization of the gas on the surface of the wafer takes away the residual water droplets on the surface to achieve traceless drying. Therefore, on the one hand, based on the sedimentation of the overflow seat, the height of the airflow nozzle and the cleaning liquid level is kept consistent to discharge the overflow of the cleaning liquid, and then the first and second airflows are purged and cooperated at the same time to make the liquid level surface at the junction perpendicular to the wafer surface and form a liquid film that is fully covered and not affected by liquid level fluctuations, thereby reducing the tension formed by the liquid surface and the incidence of the liquid surface climbing along the wafer surface, and at the same time cooperating with the coverage formed by the airflow to achieve defect-free traceless drying of the wafer surface; on the other hand, the The overflow method used, combined with the obstruction formed by the surface liquid film, not only abandons the conventional use of water gravity as a drive to control the water level to drop, but also maintains the same height difference between the overflow surface and the clean liquid surface, eliminating the liquid level fluctuation caused by the change of water level difference; thirdly, based on the inward movement of the overflow dam, the span of the liquid film layer is increased, and the probability of the liquid surface floating at the junction caused by the liquid level change formed by the overflow is reduced. At the same time, during the sedimentation process of the overflow dam, the height of the air flow nozzle and the clean liquid surface is kept consistent, thereby maintaining the stability of the entire process; fourthly, the inlet and outlet ends of each dam mouth are rounded, and the overflow is smooth, which will not be affected by the movement of the liquid film layer This causes the cleaning liquid to reflux, reducing the probability of liquid level floating. Multiple weirs are arranged side by side on the overflow weir at equal intervals, and each weir has the same length, width, and height. Based on the obstruction formed by the dam body and the diversion based on the weir, the rate of change of the cleaning liquid level caused by overflow can be effectively controlled, which is more conducive to the formation of a liquid film layer. Fifthly, based on the sedimentation of the overflow seat and the expansion and contraction of the drainage pipe, the overflow rate of the cleaning liquid can be effectively controlled by controlling the sedimentation rate, thereby meeting the cleaning needs. Based on the design of the overflow chamber, it is more conducive to the rapid overflow of the overflow cleaning liquid, and the position and expansion and contraction of the telescopic tube can be changed to meet the drainage needs.In the sixth aspect, the thickness of the liquid film layer formed from the interface to the overflow port gradually decreases. Based on the contact formed by the airflow, a gradually thinning liquid film layer is formed to cover the entire liquid surface to eliminate the water surface fluctuations caused by the overflow. The gas ejected from the airflow nozzle is isopropyl alcohol gas, and the liquid film layer is an isopropyl alcohol liquid film. Here, the volatility of isopropyl alcohol (IPA) is used to replace the residual cleaning liquid on the wafer surface to improve the drying effect; at the same time, based on the isopropyl alcohol liquid film formed to cover the cleaning liquid surface, the surface tension of the cleaning liquid is weakened, which is conducive to the stable formation of the Marangoni effect; in the seventh aspect, the flow rate of the first airflow is greater than the flow rate of the second airflow. Based on the working condition that the height of the airflow nozzle and the cleaning liquid surface remains unchanged, the cleaning effect is improved by different positions, angles, and flow rates. With the help of airflow, the required liquid film layer is formed. The gas ejected from the nozzle can directly act on the liquid surface, and the effective span can cover the entire junction of the wafer surface and the water surface, thereby forming a complete and continuous liquid film. At the same time, water in a normal state, due to the existence of surface tension, will have a climbing phenomenon at the junction of the liquid surface and the wafer surface when the liquid level drops. The liquid film has the effect of changing the surface tension of water, reducing its surface tension, so that the climbing phenomenon is greatly weakened. This ensures that the wafer surface passing by when the liquid level drops will not have too much water remaining due to the climbing phenomenon. As for the cooperation between the first and second airflows, the two are purged at the same time, and decomposed and deflected to form a covering liquid film layer, and the liquid film layer gradually becomes thinner; make full use of the second airflow The deflection keeps covering downward, so that the drying environment is the same, there is no possibility of secondary drying, and it also avoids damage to the wafer caused by excessive purging (because excessive IPA will damage the wafer surface); the eighth aspect is that the two airflows not only have differences in flow rate, but also in position and angle. Therefore, in the covering airflow purging, the water droplets on the wafer surface are taken away based on the contact formed by the liquid film layer to achieve traceless drying. At the same time, based on controlling the volume difference between the upper and lower cavities, the flow rate of the first and second airflows is controlled, thereby accurately controlling the dry airflow blowing to the wafer surface and ensuring that the required liquid film layer is formed on the cleaning liquid surface. In addition, vertical and intersecting airflows are used, and based on the difference in flow rate, on the one hand The required liquid film layer is formed, while full coverage is achieved to prevent secondary drying marks caused by water droplet splashing. Ninth, the alignment of the air outlet ends ensures that the two airflows do not become incompatible due to airflow divisions at the outlet ends. Furthermore, the key is to achieve full liquid film coverage through the positioning of the airflow ends, especially the outlet end of the lower chamber. Tenth, the layout of the two cleaning units, with the barrier formed by the wafer and carrier, divides the cleaning tank into zones. This not only enables simultaneous front- and back-side cleaning, but also creates relatively balanced overflow surfaces in the zones, eliminating pressure differences and airflow interference. This allows for efficient and high-quality simultaneous cleaning of the front and back sides of the wafer, while also enabling single-side cleaning of the wafer.

[0040] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge, comprising a soaking step and a drying step, wherein the soaking step immerses a carrier loaded with wafers in a cleaning tank containing a cleaning liquid, characterized in that: The drying steps include: S1, liquid level drops The overflow seat movably installed in the cleaning tank descends and penetrates into the cleaning liquid. When a liquid level difference is formed between the overflow port and the liquid surface of the cleaning liquid, the cleaning liquid flows into the overflow seat and is discharged from the cleaning tank based on the overflow seat. S2. Liquid film formation As the overflow seat settles, the wafer surface gradually becomes exposed above the liquid level, forming an interface and an exposed portion with the liquid level. Simultaneously, an airflow nozzle fixedly mounted above the overflow seat operates. The airflow ejected by the airflow nozzle includes a first airflow blowing obliquely from top to bottom toward the interface, and a second airflow located above the first airflow and blowing toward the exposed portion. The airflow is formed by vaporizing liquid and is volatile. The first and second airflows simultaneously sweep and cooperate to keep the liquid level at the interface perpendicular to the wafer surface, and form a liquid film layer that covers the entire surface from the interface to the overflow port. S3, seamless drying As the area of the exposed part gradually increases, with the continuous assistance of the liquid film layer, the second airflow covers the entire exposed part to form air drying, and the gas on the surface of the wafer evaporates to carry away the residual water droplets on the surface to achieve seamless drying.

2. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 1, characterized in that: In step S1 , a notch extending in a horizontal direction is formed in the overflow seat toward the side of the wafer, and an overflow surface is formed based on the bottom of the notch.

3. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 2, characterized in that: An inner extension plate extends from the bottom of the notch into the overflow seat, and an overflow dam extends upward from the inner end of the inner extension plate, wherein a plurality of dam openings are opened on the overflow dam. As the overflow dam settles, the cleaning liquid overflows from the dam openings to the overflow seat.

4. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 3 is characterized in that: The inlet and outlet ends of each dam mouth are rounded transition.

5. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 3, characterized in that: The plurality of weir openings are arranged side by side on the overflow dam at equal intervals; and / or the weir openings have the same length, width and height.

6. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to any one of claims 1 to 5, characterized in that: The overflow device used includes an overflow seat with an overflow cavity and an overflow port, a discharge pipe connected to the liquid outlet of the overflow seat, and a power component that drives the overflow seat to move up and down, wherein the discharge pipe can expand and contract synchronously with the rise and fall of the overflow seat.

7. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 6, characterized in that: The overflow cavity gradually becomes smaller from top to bottom, the liquid outlet is located at the bottom of the overflow cavity, and the liquid discharge pipeline is a telescopic tube.

8. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 7, characterized in that: The bottom of the overflow cavity is tilted up and down, the liquid outlet is located at the lower end of the tilt, and the telescopic tube is located directly below the liquid outlet.

9. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 1, characterized in that: In step S2, the thickness of the liquid film layer gradually decreases from the boundary portion toward the overflow port.

10. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 1, characterized in that: In step S2, the gas ejected from the air flow nozzle is isopropyl alcohol gas, and the liquid film layer is an isopropyl alcohol liquid film.

11. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 1, characterized in that: The flow rate of the first airflow is greater than the flow rate of the second airflow; and / or, the airflow nozzle has an air inlet cavity and an air outlet cavity, wherein the air outlet cavity includes an upper cavity and a lower cavity respectively connected to the air inlet cavity, the upper cavity ejects the second airflow, and the lower cavity ejects the first airflow.

12. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 11, characterized in that: The volume of the lower cavity is smaller than that of the upper cavity; and / or the volume of the upper cavity is 1.5 to 5 times the volume of the lower cavity.

13. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 11, characterized in that: The air outlet ends of the upper cavity and the lower cavity are both located above and to the side of the overflow port; the air outlet end of the upper cavity extends in a horizontal direction, and the direction of the ejected second airflow is perpendicular to the wafer cleaning surface; the air outlet end of the lower cavity is inclined from top to bottom, and the ejected first airflow intersects with the wafer cleaning surface and the liquid level surface respectively.

14. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 13, characterized in that: The gas outlet ends of the upper cavity and the lower cavity are aligned vertically; and / or the gas outlet end of the lower cavity is located above the middle of the liquid film layer.

15. The wafer surface cleaning process based on liquid film deposition in cooperation with overflow and airflow purge according to claim 1, characterized in that: The wafer has a front side and a back side, each of which corresponds to a group of cleaning units. The carrier and the wafer separate the cleaning tank into two relatively separated front cleaning area and back cleaning area that are connected at the bottom. Each group of cleaning units includes an overflow seat and an air flow nozzle. The two overflow seats sink synchronously and the two air flow nozzles spray gas simultaneously to clean the front and back sides of the wafer synchronously.

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