Wafer surface cleaning method based on overflow and air flow purging collaborative liquid film settlement

Abstract

The application discloses a wafer surface cleaning process based on overflow and airflow blowing cooperation liquid film settlement, which comprises a soaking step and a drying step. One aspect of the application is based on the settlement of the overflow seat, the cleaning liquid is overflowed and discharged with the height of the airflow nozzle and the cleaning liquid surface being always consistent, and then the first and second airflows are simultaneously blown and cooperated to make the liquid level surface of the interface and the wafer surface keep vertical and form full coverage and liquid film not affected by liquid level fluctuation, reduce the tension formed by the liquid surface, and reduce the occurrence rate of the liquid surface climbing along the wafer surface, and cooperate with the coverage formed by the airflow to realize the traceless drying of the wafer surface without defects. The overflow mode adopted in the other aspect not only abandons the conventional utilization of the gravity of water as the driving force to control the water surface to drop, but also keeps the same drop of the overflow surface and the cleaning liquid surface, and eliminates the liquid surface fluctuation caused by the water level difference change.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor processing, and particularly relates to a wafer surface cleaning method based on overflow and airflow blowing cooperation liquid film settlement. BACKGROUND

[0002] In the semiconductor industry, after a wafer wet method, the wafer method surface residual chemical agent usually needs to be cleaned and dried to ensure that the wafer method surface chemical agent is clean and the particle quantity after drying meets the requirements of subsequent methods.

[0003] At present, the traditional cleaning process is: (1) soaking; (2) drying, wherein the wafer is loaded on a carrier, and the carrier is immersed in a cleaning tank containing a cleaning liquid to complete the soaking; and the drying means mainly includes high-purity nitrogen drying and Malan Goni drying. However, in the above drying process, the following technical defects exist:

[0004] 1. High-purity nitrogen drying is mainly based on the unloading of the soaking liquid, and the exposed wafer part is blown dry by high-purity nitrogen. Although it seems simple and efficient, when the gas acts on the wafer surface with large water droplets, the water droplets will splash, causing the already dried position to introduce water droplets again, and after being dried again, water marks will be formed. The water marks are very difficult to clean, and if not cleaned deeply, the wafer will be scrapped.

[0005] 2. In the drying method based on the Malan Goni principle, when two liquids with different surface tensions contact, the surface liquid film (also known as IPA liquid film or isopropyl alcohol liquid film) flows from the area with low surface tension to the area with high surface tension. At the same time, as the liquid level drops during cleaning liquid discharge, the water flow converges to the middle. Therefore, the liquid film remains in contact with the wafer surface, and the liquid film volatilizes with the contact liquid film on the exposed wafer to achieve mark-free drying. However, in actual operation, the liquid level drop speed changes 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 an angle, thus greatly increasing the probability of water marks on the wafer surface. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide an improved wafer surface cleaning method based on overflow and airflow blowing cooperation liquid film settlement.

[0007] To solve the above technical problems, the present application adopts the following technical solutions:

[0008] A wafer surface cleaning method based on overflow and airflow blowing cooperation liquid film settlement, comprising a soaking step and a drying step, wherein the soaking step submerges a carrier loaded with a wafer in a cleaning tank containing a cleaning liquid, and the drying step comprises:

[0009] S1, liquid level drop

[0010] The downward extension of the overflow seat installed movably in the cleaning tank extends into the cleaning liquid, when the overflow port and the cleaning liquid surface 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;

[0011] S2, liquid film formation

[0012] With the settlement of the overflow seat, the wafer surface is gradually exposed above the liquid level and forms an interface and an exposed part between the liquid level, and based on the airflow nozzle fixedly installed above the overflow seat, the airflow nozzle sprays airflow including first airflow obliquely blowing from top to bottom to the interface and second airflow above the first airflow and blowing to the exposed part, wherein the airflow is gasified from liquid and volatile, the first and second airflow simultaneously sweeps and cooperates to make the liquid level of the interface and the wafer surface keep vertical, and the liquid film layer forms an overall coverage from the interface to the overflow port;

[0013] S3, traceless drying

[0014] With the gradual increase of the area of the exposed part, the second airflow covers the entire exposed part to form air drying under the continuous assistance of the liquid film layer, and the gas volatilization of the wafer surface carries away the surface residual water droplets to realize traceless drying.

[0015] Preferably, in step S1, the overflow seat forms a gap extending along the horizontal direction from the side of the wafer, and an overflow surface is formed based on the bottom of the gap. In short, the conventional method of using the gravity of water as the driving force to control the water level drop is abandoned, and at the same time the overflow surface keeps the same difference with the cleaning liquid surface, eliminating the liquid level fluctuation caused by the change of water level difference (or, based on the stable drop of water surface, eliminating the influence of water surface fluctuation).

[0016] According to one specific implementation and preferred aspect of the present application, an inner extension plate is formed extending from the bottom of the gap to the overflow seat, and an overflow dam is formed extending upward at the inner end of the inner extension plate, wherein a plurality of dam openings are formed on the overflow dam, and with the settlement of the overflow dam, the cleaning liquid overflows from the dam openings to the overflow seat. The inward movement of the overflow dam increases the span of the liquid film layer, reduces the probability of liquid level fluctuation of the interface caused by the change of liquid level formed by overflow, and at the same time, during the settlement process of the overflow dam, the height of the airflow nozzle and the cleaning liquid surface is kept consistent at all times, thereby keeping the whole method stable and reliable.

[0017] Preferably, the inlet and outlet ends of each dam are rounded to transition smoothly. Overflow is smooth, and backflow of cleaning liquid due to movement of the liquid film layer is avoided, reducing the probability of liquid surface fluctuation.

[0018] In some embodiments, the plurality of dams are arranged equidistantly side by side on the overflow dam; further, each dam has the same length, width, and height. Based on the blocking formed by the dam body and the flow splitting by the dam, the rate of change of the cleaning liquid level caused by overflow can be effectively controlled, which is more conducive to the formation of the liquid film layer.

[0019] According to another specific implementation and preferred aspect of the present application, the overflow device used includes an overflow seat with an overflow cavity and an overflow port, a liquid discharge pipeline connected to the liquid outlet of the overflow seat, and a power assembly driving the upward and downward movement of the overflow seat, wherein the liquid discharge pipeline can expand and contract synchronously with the lifting of the overflow seat. Based on the sinking of the overflow seat and the expansion and contraction of the liquid discharge pipeline, the overflow amount of cleaning liquid can be effectively controlled by controlling the sinking speed, thereby meeting the cleaning needs.

[0020] Preferably, the overflow cavity gradually decreases from top to bottom, the liquid outlet is located at the bottom of the overflow cavity, and the liquid discharge pipeline is a telescopic pipe. Based on the design of the overflow cavity, the cleaning liquid overflowed is more quickly discharged, and the position and telescopic change of the telescopic pipe meet the liquid discharge needs.

[0021] Further, the bottom of the overflow cavity is inclined upward and downward, the liquid outlet is located at the lower end of the inclination, and the telescopic pipe is located directly below the liquid outlet. Based on the converging layout, the overflow discharge is accelerated.

[0022] According to another specific implementation and preferred aspect of the present application, in step S2, the liquid film layer thickness gradually decreases from the junction to the overflow port. Based on the contact formed by the airflow, the gradually thinned liquid film layer covers the entire liquid surface to eliminate the water surface fluctuation caused by overflow.

[0023] Preferably, the gas sprayed by the airflow nozzle is isopropyl alcohol gas, and the liquid film layer is isopropyl alcohol liquid film. Here, the volatile 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 reduced, which is conducive to the stable formation of the Marangoni effect.

[0024] According to another specific implementation and preferred aspect of the present application, the flow rate of the first airflow is greater than the flow rate of the second airflow. Based on the condition that the height of the airflow nozzle and the cleaning liquid surface is unchanged, the required liquid film layer is formed with the assistance of airflows of different positions and angles and flow rates.

[0025] Briefly, the gas sprayed by the nozzle can directly act on the liquid surface, and the effective span can cover the entire intersection between the wafer surface and the water surface, thereby forming a complete and continuous liquid film. In the normal state, the water will have a climbing phenomenon at the intersection between the liquid surface and the wafer surface due to the presence of surface tension when the liquid level drops. The liquid film has the effect of changing the surface tension of the water, reducing the surface tension, and greatly reducing the climbing phenomenon. This ensures that the wafer surface passing through will not leave too much water due to the climbing phenomenon when the liquid level drops.

[0026] Preferably, in step S2, the gas flow 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 communicating with the air inlet cavity, the upper cavity sprays the second gas flow, and the lower cavity sprays the first gas flow. The two gas flows not only have different flow rates, but also have different positions and angles, so that the contact belt formed based on the liquid film layer can remove the water droplets on the wafer surface in the covered gas flow sweeping to achieve traceless drying.

[0027] Further, the volume of the lower cavity is smaller than the volume of the upper cavity; and / or, the volume of the upper cavity is 1.5-5 times the volume of the lower cavity. Based on the volume difference of the upper and lower cavities, the flow rates of the first and second gas flows are controlled, so as to accurately control the air-drying gas flow blowing to the wafer surface and ensure the formation of the required liquid film layer on the clean liquid surface.

[0028] In some specific embodiments, the air outlet ends of the upper cavity and the lower cavity are located above the side of the overflow port; the air outlet end of the upper cavity extends along the horizontal direction, and the sprayed second gas flow is perpendicular to the wafer cleaning surface; the air outlet end of the lower cavity is inclined from top to bottom, and the sprayed first gas flow intersects the wafer cleaning surface and the liquid level surface, respectively. By using vertical and intersecting gas flows and based on the difference in flow rate, on the one hand, the required liquid film layer is formed, and on the other hand, full coverage is formed to avoid the splashing of water droplets to cause secondary drying marks.

[0029] Further, the air outlet ends of the upper cavity and the lower cavity are arranged in alignment. Further, the air outlet end of the lower cavity 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 gas flows cannot cooperate due to the air outlet ends, and by the position layout of the air outlet ends, especially the air outlet end of the lower cavity, it is the key to form a comprehensive liquid film.

[0030] In addition, the wafer has a front surface and a back surface, wherein the front surface and the back surface correspond to a set of cleaning units, the carrier and the wafer divide the cleaning tank into two opposite and bottom-communicating front cleaning area and back cleaning area, wherein each set of cleaning units comprises an overflow seat and an air flow nozzle, and the front surface and the back surface of the wafer are synchronously cleaned by the synchronous settlement of the two overflow seats and the synchronous air flow of the two air flow nozzles. Based on the barrier formed by the wafer and the carrier, the cleaning tank is divided into zones, which can not only synchronously clean the front surface and the back surface, but also form a relatively balanced overflow surface without pressure difference and air flow interference, thereby efficiently and high-quality synchronously cleaning the front surface and the back surface of the wafer.

[0031] Thanks to the implementation of the above technical solutions, the present application has the following advantages compared with the prior art:

[0032] In the drying process of the existing wafer cleaning, if high-purity nitrogen is used for drying, it is mainly based on the unloading of the soaking liquid, and the exposed wafer is dried by blowing high-purity nitrogen. On the surface, it is simple and efficient, but when the gas acts on the position of the wafer surface with large water droplets, it will cause the water droplets to splash, causing the already dried position to introduce water droplets again, and after being dried again, water marks will be formed. It is very difficult to clean, and if not cleaned deeply, it will cause the wafer to be scrapped. If the drying method based on the Marangoni principle is used, it mainly uses two liquids with different surface tensions to contact, and the 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 converges to the middle. Therefore, the liquid film keeps in contact with the wafer surface, and as the wafer is exposed to the liquid film, the residual water droplets on the surface are taken away by the evaporation of the liquid film, realizing mark-free drying. However, in actual operation, the speed of liquid level drop changes with pressure, so the probability of liquid level fluctuation increases greatly. Based on the liquid level fluctuation, the cleaning liquid is easy to climb up along the wafer surface to be cleaned and form an angle, so the probability of water marks on the wafer surface increases greatly, and so on. The wafer surface cleaning method based on overflow and air flow blowing cooperates with liquid film settlement is designed as a whole, and the shortcomings and defects of the prior art are ingeniously solved. After using the wafer cleaning method, first, the carrier loaded with the wafer is immersed in the cleaning tank containing the cleaning liquid. Second, the overflow seat movably installed in the cleaning tank is immersed in the cleaning liquid. When the overflow port and 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. Then, as the overflow seat settles, the wafer surface gradually exposes above the liquid level and forms an interface and an exposed part between the liquid level. At the same time, the air flow nozzle fixedly installed above the overflow seat works. The air flow of the air flow nozzle includes the first air flow obliquely blowing from top to bottom to the interface, and the second air flow above the first air flow blowing to the exposed part. The air flow is formed by the gasification of the liquid and is easy to evaporate. The first and second air flows blow and cooperate to make the liquid level of the interface and the wafer surface keep vertical, and form an overall covering liquid film layer from the interface to the overflow port. Finally, as the area of the exposed part gradually increases, the second air flow covers the whole exposed part to form air drying under the continuous assistance of the liquid film layer, and the gas evaporation of the wafer surface takes away the residual water droplets on the surface to realize mark-free drying. Therefore, on the one hand, based on the settlement of the overflow seat, the height of the air flow nozzle and the cleaning liquid surface is kept consistent and unchanged to overflow and discharge the cleaning liquid. The first and second air flows blow and cooperate to make the liquid level of the interface and the wafer surface keep vertical and form a fully covering liquid film that is not affected by the liquid level fluctuation, reduce the tension formed by the liquid level, and reduce the occurrence rate of the liquid level climbing along the wafer surface. At the same time, cooperate with the coverage formed by the air flow to realize the mark-free drying of the wafer surface without defects.The overflow mode adopted in another aspect, in combination 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 surface drop, but also keeps the overflow surface and the cleaning liquid surface at the same drop, eliminating the liquid surface fluctuation caused by water level difference changes. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Structure schematic diagram of wafer surface cleaning equipment of the present application (partially exploded);

[0034] Figure 2 Structure schematic diagram of the present application; Figure 1

[0035] Figure 3 Structure schematic diagram of the present application; Figure 2

[0036] Figure 4 Structure schematic diagram of the present application; Figure 1

[0037] Figure 5 Structure schematic diagram of the present application; Figure 4

[0038] Figure 6 Structure schematic diagram of the present application; Figure 5

[0039] Figure 7 Structure schematic diagram of the present application; Figure 4

[0040] Figure 8 Structure schematic diagram of the present application; Figure 7

[0041] Wherein: 1, cleaning tank;

[0042] 2, carrier;

[0043] 3, cleaning unit; 30, overflow device; 300, overflow seat; q, overflow cavity; k, overflow port; 301, liquid discharge pipeline; 302, power assembly; 303, inner extension plate; 304, overflow dam; a, dam port; 31, air flow nozzle; 310, air inlet cavity; 311, air outlet cavity; s1, upper cavity; s2, lower cavity;

[0044] 4, cleaning liquid recovery tank;

[0045] w, wafer. DETAILED DESCRIPTION

[0046] ​​​​​​​In order to make the above objectives, features and advantages of the present application more clear and understandable, the detailed description of the embodiments of the present application is made below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in many different ways from what is described herein, and should not be construed as being limited to the embodiments set forth herein, but should be understood to include all possible embodiments that can be made within the scope of the present application.

[0047] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore should not be construed or implied to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present application.

[0048] In addition, the terms "first", "second", "third", etc. are only used for descriptive purpose and should not be construed or implied to indicate or imply relative importance or implicitly indicate the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0049] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be the internal communication or interaction relationship of two elements, unless otherwise specifically defined. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0050] In the present application, unless otherwise specifically defined and limited, the first feature "on" or "under" the second feature can be direct contact between the first and second features, or indirect contact between the first and second features through intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0051] It is to be understood that when an element such as a layer, region or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element or intervening elements can be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements present. It will be understood that, when a term is used in the singular herein, it is also intended that the term be used in the plural, and vice versa, as appropriate. The terminology used herein, such as "vertical," "horizontal," "upper," "lower," "left," "right," and the like, is only used for the purpose of illustration and not as a limitation.

[0052] As shown in FIG. 1, the wafer surface cleaning method based on overflow and air flow blowing cooperation liquid film settlement of the present embodiment adopts a cleaning device including 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. A wafer w is installed in the carrier 2, and the carrier 2 is inserted into the cleaning tank 1. The cleaning unit 3 has two groups with respect to the surface of the wafer w, and the two groups of cleaning units 3 move synchronously to clean the front and back surfaces of the wafer w synchronously. Figures 1 to 8 Specifically, each group of cleaning units 3 includes an overflow device 30 and an air flow nozzle 31. The overflow device 30 includes an overflow seat 300 having an overflow cavity q and an overflow port k, a liquid discharge pipeline 301 connected to the liquid outlet of the overflow seat 300, and a power assembly 302 driving the overflow seat 300 to move up and down. The liquid discharge pipeline 301 can expand and contract synchronously with the overflow seat 300. By controlling the settlement speed based on the settlement of the overflow seat 300 and the expansion and contraction of the liquid discharge pipeline 301, the overflow amount of the cleaning liquid can be effectively controlled, thereby meeting the cleaning needs.

[0053] The overflow seat 300 is formed with a gap extending along the horizontal direction from the side of the wafer, and an overflow surface is formed at the bottom of the gap. In short, the conventional method of using the gravity of water as a driving force to control the water surface to drop is abandoned, and the overflow surface and the cleaning liquid surface maintain the same drop, thereby eliminating the liquid surface fluctuation caused by the change of the water level difference (or, based on the stable drop of the water surface, the influence of the liquid surface fluctuation is eliminated). An inner extension plate 303 is formed inside the overflow seat 300 from the bottom of the gap, and an overflow dam 304 is formed upward at the inner end of the inner extension plate 303. A plurality of dam openings a are formed in the overflow dam 304, and the cleaning liquid overflows from the dam openings a to the overflow seat 300 as the overflow dam 304 settles. The inner movement of the overflow dam increases the span of the liquid film layer, reduces the probability of liquid surface fluctuation at the junction caused by the change of the liquid surface formed by overflow, and maintains the height of the air flow nozzle and the cleaning liquid surface consistent during the settlement of the overflow dam, thereby maintaining the stability and reliability of the whole method.

[0054]

[0055] ​In some embodiments, the inlet and outlet ends of each dam opening a are rounded. Overflow is smooth, and backflow of cleaning liquid due to movement of the liquid film layer is reduced, reducing the probability of liquid surface floating. Multiple dam openings a are arranged equidistantly side by side on the overflow dam 304; further, each dam opening a has the same length, width, and height. Based on the blocking formed by the dam body and the flow splitting based on the dam opening, the rate of change of the cleaning liquid level caused by overflow can be effectively controlled, which is more conducive to the formation of the liquid film layer.

[0056] In this example, the overflow cavity q gradually decreases from top to bottom, the liquid outlet is located at the bottom of the overflow cavity q, and the drainage pipeline 301 is a telescopic pipe. Based on the design of the overflow cavity q, the cleaning liquid can quickly overflow, and the position and telescopic change of the telescopic pipe meet the drainage needs. Further, the bottom of the overflow cavity q is inclined upward and downward, the liquid outlet is located at the lower end of the inclination, and the telescopic pipe is located directly below the liquid outlet. Based on the confluence layout, the overflow discharge is accelerated.

[0057] 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 which are respectively connected with the air inlet cavity 310, the upper cavity s1 sprays the second air flow, and the lower cavity s2 sprays the first air flow. The two air flows not only have flow differences, but also have position and angle differences, so that the contact belt formed based on the liquid film layer can remove the water droplets on the wafer surface in the covered air flow blowing to achieve traceless drying. Further, 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 the volume difference of the upper and lower cavities, the control of the flow of the first and second air flows is realized, so as to accurately control the air-drying air flow blowing to the wafer surface and ensure 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 located above the overflow port; the air outlet end of the upper cavity s1 extends along the horizontal direction, and the direction of the sprayed second air flow is perpendicular to the wafer cleaning surface; the air outlet end of the lower cavity s2 is inclined from top to bottom, and the sprayed first air flow intersects the wafer cleaning surface and the liquid level surface, respectively. By using the vertical and intersecting air flows and based on the flow difference, on the one hand, the required liquid film layer is formed, and on the other hand, full coverage is formed to avoid the splashing of water droplets to cause secondary drying marks. The air outlet ends of the upper cavity s1 and the lower cavity s2 are arranged in alignment, and further, the air outlet end of the lower cavity s2 is located above the middle part of the liquid film layer. Based on the alignment of the air outlet ends, it is ensured that the two air flows cannot cooperate due to the air outlet ends, and by the position layout of the air outlet ends, especially the air outlet end of the lower cavity, the key to forming a fully covered liquid film is formed. As for the cooperation between the first and second air flows, the following is mainly embodied: 1. Both of them blow at the same time, and decompose and deflect to form a covered liquid film layer, and the liquid film layer gradually thins; 2. Make full use of the deflection of the second air flow to maintain downward coverage, so that the drying environment is the same, and there is no possibility of secondary drying, and also avoids excessive blowing to cause damage to the wafer (because IPA in excess will cause damage to the wafer surface).

[0058] In summary, the wafer is taken as an example for single-side cleaning of the front or back surface, and the specific implementation process is as follows:

[0059] (1) soaking step, the carrier loaded with the wafer is immersed in the cleaning tank containing the cleaning liquid;

[0060] (2) drying step, comprising: S1, liquid level drop, which is downwardly inserted into the cleaning liquid by the overflow seat installed in the cleaning tank, when the overflow port and 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 flows back to the cleaning liquid recovery tank; S2, the formation of liquid film, with the settlement of the overflow seat, the wafer surface is gradually exposed above the liquid level and forms an interface and an exposed part between the liquid level, and based on the air flow nozzle fixedly installed above the overflow seat, the air flow nozzle sprays air flow including first air flow obliquely blowing from top to bottom to the interface, and second air flow above the first air flow and blowing to the exposed part, wherein the air flow is formed by gasification of liquid and is volatile, the first and second air flows are swept and cooperated at the same time to make the liquid level of the interface and the wafer surface keep vertical, and the liquid film layer is formed from the interface to the overflow port, which is isopropyl alcohol liquid film (IPA liquid film), and the liquid film layer thickness gradually decreases from the interface to the overflow port; S3, traceless drying, with the gradual increase of the area of the exposed part, under the continuous assistance of the liquid film layer, the second air flow covers the whole exposed part to form air drying, and the gas volatilization on the wafer surface carries away the surface residual water droplets to realize traceless drying.

[0061] Specifically, the flow rate of the first air flow is greater than that of the second air flow. Under the condition that the height of the air flow nozzle and the cleaning liquid surface is unchanged, the required liquid film layer is formed by the air flow with different positions and angles and flow rates. In short, the gas sprayed by the nozzle can directly act on the liquid surface, and the effective span can cover the whole wafer surface and the water surface intersection, thereby forming a complete and continuous liquid film. At the same time, under the normal state, because of the existence of surface tension, when the liquid level drops, the liquid surface and the wafer surface intersection will appear a climbing phenomenon. The liquid film has the effect of changing the surface tension of water, reduces the surface tension, and makes the climbing phenomenon weaken a lot, so that the wafer surface passing through the liquid level drop will not be left with too much water due to the climbing phenomenon. The gas sprayed by the air flow nozzle 31 is isopropyl alcohol gas, and the liquid film layer is isopropyl alcohol liquid film. Here, the volatile nature 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 reduced, which is conducive to the stable formation of the Marangoni effect.

[0062] In addition, the present application can also implement the synchronous cleaning of the front and back surfaces of the wafer, and the specific implementation process is as follows:

[0063] (1) soaking step, the carrier loaded with the wafer is immersed in the cleaning tank containing the cleaning liquid, the cleaning tank is relatively separated by the wafer and the carrier, and the front cleaning area and the back cleaning area are connected at the bottom;

[0064] (2) drying step, comprising: S1, liquid level drop, which is synchronized downwardly into the cleaning liquid by two overflow seats installed in the cleaning tank, when the overflow port and 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 returns to the cleaning liquid recovery tank; S2, the formation of liquid film, with the settlement of the overflow seat, the wafer surface is gradually exposed above the liquid level and forms an interface and an exposed part between the liquid level, and each airflow nozzle is operated based on the fixed installation above the overflow seat, the airflow of each airflow nozzle includes the first airflow obliquely blowing from top to bottom to the interface, and the second airflow blowing to the exposed part above the first airflow, wherein the airflow is gasified from liquid and volatile, the first and second airflow simultaneously sweep and cooperate to make the liquid level of the interface and the wafer surface keep vertical, and the liquid film layer is formed from the interface to the overflow port, which is isopropyl alcohol liquid film (IPA liquid film), and the liquid film layer thickness gradually decreases from the interface to the overflow port, the airflow between the front cleaning area and the back cleaning area is separated and does not interfere with each other; S3, traceless drying, with the gradual increase of the area of the exposed part, under the continuous assistance of the liquid film layer, the second airflow covers the whole exposed part to form air drying, and the gas volatilization of the wafer surface carries away the surface residual water droplets to realize traceless drying.

[0065] In summary, after the wafer cleaning method is adopted, firstly, the carrier loaded with the wafer is immersed in the cleaning tank containing the cleaning liquid; secondly, the downward extension of the overflow seat movably installed in the cleaning tank is immersed in the cleaning liquid, when the liquid level difference is formed between the overflow port and the cleaning liquid surface, the cleaning liquid flows into the overflow seat, and the cleaning liquid is discharged from the cleaning tank based on the overflow seat; then, with the settlement of the overflow seat, the wafer surface is gradually exposed above the liquid level surface and forms an interface and an exposed part between the liquid level surface, and the airflow nozzle fixedly installed above the overflow seat is operated at the same time, the airflow jetted by the airflow nozzle includes the first airflow obliquely blown from top to bottom to the interface and the second airflow above the first airflow and blown to the exposed part, wherein the airflow is formed by the gasification of the liquid and is volatile, the first and second airflows are swept and cooperated at the same time to make the liquid level surface of the interface keep vertical to the wafer surface, and the liquid film layer is formed to integrally cover the interface from the interface to the overflow port; finally, with the gradual increase of the area of the exposed part, the second airflow covers the whole exposed part to form air drying under the continuous assistance of the liquid film layer, and the gas volatilization on the wafer surface carries away the surface residual water droplets to realize the traceless drying, therefore, on the one hand, based on the settlement of the overflow seat, the cleaning liquid is overflowed and discharged with the height of the airflow nozzle and the cleaning liquid surface kept consistent and unchanged, then the first and second airflows are swept and cooperated at the same time to make the liquid level surface of the interface keep vertical to the wafer surface and form the liquid film which is fully covered and is not affected by the liquid level fluctuation, the tension formed by the liquid surface is reduced, the occurrence rate of the liquid surface climbing along the wafer surface is reduced, and the covering formed by the airflow is matched to realize the traceless drying of the wafer surface without defects; on the other hand, the overflow mode adopted is matched with the obstruction formed by the surface liquid film, not only the gravity of water is used as the driving to control the water surface to drop in the conventional way, but also the same difference is kept between the overflow surface and the cleaning liquid surface to eliminate the liquid level fluctuation caused by the change of the water level difference; on the third hand, the span of the liquid film layer is increased based on the inward movement of the overflow dam to reduce the probability of the liquid surface fluctuation of the interface caused by the change of the liquid surface formed by the overflow, and the height of the airflow nozzle and the cleaning liquid surface is kept consistent during the settlement process of the overflow dam, so that the stability of the whole method is kept; on the fourth hand, the inlet and outlet ends of each dam port are circularly transitioned, the overflow is smooth, the backflow of the cleaning liquid caused by the movement of the liquid film layer is reduced, the probability of the liquid surface fluctuation is reduced, a plurality of dam ports are arranged on the overflow dam at equal intervals, the length, width and height of each dam port are the same, the obstruction formed by the dam body and the shunt based on the dam port can effectively control the change rate of the cleaning liquid level caused by the overflow, and are more conducive to the formation of the liquid film layer; on the fifth hand, the overflow amount of the cleaning liquid can be effectively controlled by controlling the settlement speed based on the settlement and discharge pipeline of the overflow seat, so that the cleaning needs are met; the overflow cavity is designed based on the modeling design, which is more conducive to the rapid overflow of the cleaning liquid, and the position and telescopic change of the telescopic pipe meet the discharge needs.The sixth aspect forms a liquid film layer with gradually decreasing thickness from the intersection to the overflow port, based on the contact formed by the airflow, the gradually thinning liquid film layer covers the entire liquid surface to eliminate the water surface fluctuation caused by overflow, the gas sprayed by the airflow nozzle is isopropyl alcohol gas, and the liquid film layer is isopropyl alcohol liquid film. Here, the volatile nature of isopropyl alcohol (IPA) is used to replace the cleaning liquid remaining 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 reduced, which is conducive to the stable formation of the Marangoni effect. The seventh aspect is that the flow rate of the first airflow is greater than the flow rate of the second airflow. Based on the condition that the height of the airflow nozzle and the cleaning liquid surface is constant, the required liquid film layer is formed with the assistance of airflows from different positions and angles. The gas sprayed by the nozzle can directly act on the liquid surface, and the effective span can cover the entire wafer surface and the intersection with the water surface, thereby forming a complete and continuous liquid film. At the same time, under normal conditions, due to the existence of surface tension, when the liquid level drops, the intersection between the liquid surface and the wafer surface will appear a climbing phenomenon. The liquid film has the effect of changing the surface tension of the water, reducing the surface tension, and greatly reducing the climbing phenomenon. This ensures that the wafer surface passing through the liquid level will not be left with too much water due to the climbing phenomenon. As for the cooperation between the first and second airflows, both of them are blown at the same time, and the liquid film layer is formed by decomposing and deflection. The liquid film layer gradually thins. Make full use of the deflection of the second airflow to keep covering downward, so that the drying environment is the same, and the possibility of secondary drying does not occur. Moreover, it also avoids the damage to the wafer caused by excessive blowing (because excessive IPA will cause damage to the wafer surface). The eighth aspect is that the two airflows not only have different flow rates, but also have different positions and angles. Therefore, in the process of covering the airflow blowing, the liquid film layer formed by the contact carries away the water droplets on the wafer surface to achieve traceless drying. At the same time, based on the volume difference between the upper and lower cavities, the flow rates of the first and second airflows are controlled, so as to accurately control the air-drying airflow blown to the wafer surface and ensure the formation of the required liquid film layer on the cleaning liquid surface. In addition, the vertical and intersecting airflows are adopted, and based on the difference in flow rate, on the one hand, the required liquid film layer is formed, and on the other hand, the entire coverage is formed to avoid the splashing of water droplets to cause secondary drying marks. The ninth aspect is based on the alignment of the gas outlet end to ensure that the two airflows cannot cooperate due to the gas outlet end. Moreover, through the position layout of the airflow end, especially the gas outlet end of the lower cavity, the key to forming a comprehensive liquid film is formed. The tenth aspect is based on the layout of the two cleaning units. The barrier formed by the wafer and the carrier divides the cleaning tank into zones. Not only can the front and back surfaces be cleaned synchronously, but the partition overflow surface formed is relatively balanced, without pressure difference and interference between airflows, so as to efficiently and high-quality clean the front and back surfaces of the wafer synchronously. At the same time, single-sided cleaning of the wafer can also be implemented.

[0066] The above has made the detailed description to the application, its purpose is in order to let the person who is familiar with this field technology can understand the content of the application and implements, and cannot limit the protection scope of the application with this, all according to the spirit of the application of equivalent change or modification, should be covered in the protection scope of the application.

Claims

1. A wafer surface cleaning method based on overflow and air flow purge cooperative liquid film deposition, comprising a soaking step and a drying step, wherein the soaking step submerges a carrier loaded with wafers in a cleaning tank containing a cleaning liquid, characterized in that, The drying step comprises: S1, liquid level drop The downward extension of the overflow seat installed in the cleaning tank into the cleaning liquid, when the overflow port and the cleaning liquid form a liquid level difference, the cleaning liquid flows into the overflow seat, and the cleaning liquid is discharged from the overflow seat; S2, liquid film forming With the settlement of the overflow seat, the wafer surface is gradually exposed above the liquid level and forms an interface and an exposed part between the liquid level, and based on the fixed installation of the air flow nozzle above the overflow seat, the air flow nozzle sprays air flow including the first air flow obliquely from top to bottom to the interface, the second air flow above the first air flow and blowing to the exposed part, wherein the air flow is gasified from liquid and volatile, the first and second air flows are swept and cooperated to make the liquid level of the interface and the wafer surface keep vertical, and the liquid film layer is formed from the interface to the overflow port, and the thickness of the liquid film layer from the interface to the overflow port gradually decreases; S3, no trace drying With the gradual increase of the area of the exposed part, the second air flow covers the whole exposed part to form air drying under the continuous assistance of the liquid film layer, and the gas volatilization of the wafer surface carries away the surface residual water droplets to realize no trace drying.

2. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 1, wherein, In step S1, the overflow seat forms a gap extending along the horizontal direction from the side of the wafer, and an overflow surface is formed at the bottom of the gap.

3. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 2, characterized in that, An inner extension plate is formed extending into the overflow seat from the bottom of the gap, and an overflow dam is formed extending upward at the inner end of the inner extension plate, wherein a plurality of dam openings are formed on the overflow dam, and with the settlement of the overflow dam, the cleaning liquid overflows from the dam openings to the overflow seat.

4. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 3, wherein, The inlet and outlet ends of each dam opening are rounded.

5. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 3, characterized in that, The plurality of dam openings are arranged equidistantly on the overflow dam.

6. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 3, wherein, Each dam opening has the same length, width and height.

7. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to any one of claims 1 to 6, characterized in that, The overflow device used comprises an overflow seat with an overflow cavity and an overflow port, a liquid discharge pipeline connected to the liquid outlet of the overflow seat, and a power assembly driving the upward and downward movement of the overflow seat, wherein the liquid discharge pipeline can be expanded and contracted synchronously with the lifting of the overflow seat.

8. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 7, wherein, The overflow cavity gradually decreases from top to bottom, and the liquid outlet is located at the bottom of the overflow cavity. The liquid discharge pipeline is a telescopic pipe.

9. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 8, wherein, The bottom of the overflow cavity is arranged obliquely upward and downward, and the liquid outlet is located at the lower end of the oblique part. The telescopic pipe is located directly below the liquid outlet.

10. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 1, wherein, In step S2, the gas sprayed by the air flow nozzle is isopropyl alcohol gas, and the liquid film layer is isopropyl alcohol liquid film.

11. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 1, wherein, The flow rate of the first air flow is greater than that of the second air flow.

12. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 1, wherein, The air flow nozzle has an air inlet cavity and an air outlet cavity, wherein the air outlet cavity comprises an upper cavity and a lower cavity which are in communication with the air inlet cavity, respectively, the upper cavity sprays the second air flow, and the lower cavity sprays the first air flow.

13. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 12, wherein, The volume of the lower cavity is smaller than that of the upper cavity.

14. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 13, wherein, The volume of the upper cavity is 1.5-5 times that of the lower cavity.

15. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 12, wherein, The air outlet ends of the upper cavity and the lower cavity are located above the side of the overflow port; the air outlet end of the upper cavity extends along the horizontal direction, and the direction of the sprayed second air flow is perpendicular to the wafer cleaning surface; the air outlet end of the lower cavity is inclined from top to bottom, and the sprayed first air flow intersects the wafer cleaning surface and the liquid level, respectively.

16. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 15, wherein, The air outlet ends of the upper cavity and the lower cavity are arranged in alignment upward and downward.

17. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition of claim 15, wherein, The air outlet end of the lower cavity is located above the middle of the liquid film layer.

18. The wafer surface cleaning method based on overflow and gas flow purge collaborative liquid film deposition according to claim 1, wherein, The wafer has a front surface and a back surface, wherein the front surface and the back surface correspond to a set of cleaning units, the carrier and the wafer divide the cleaning tank into two opposite and bottom-communicating front cleaning area and back cleaning area, wherein each set of cleaning units comprises an overflow seat and an air flow nozzle, and the front surface and the back surface of the wafer are synchronously cleaned by the synchronous settlement of the two overflow seats and the simultaneous air injection of the two air flow nozzles.

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