A wafer cleaning device and cleaning method based on megasonic waves

Abstract

The present invention discloses a wafer cleaning device and a cleaning method based on megasonic waves, which relate to the technical field of wafer pre-processing. The device includes a cleaning tank, on the top of which a transport track is arranged. A megasonic wave generator is installed inside the cleaning tank. A wafer transport rack is slidably arranged inside the transport track. A plurality of movable wafer bodies are clamped simultaneously at the bottom of the wafer transport rack. A detection camera is installed on the transport track. The detection camera is used to collect the oblique angle photos of the lithography surface of the wafer body, and the humidity data of the wafer body is identified based on the oblique angle photos of the lithography surface. Since the symmetric air-drying mechanism applies symmetric wind forces to the surface of the wafer body, when the wafer body is under the action of a large wind force, the acting forces on both sides of the wafer body will cancel each other out, ensuring that the wafer body will not deform, guaranteeing the safety of the wafer body, and while improving the air-drying efficiency of the wafer body, the wafer body is not likely to break.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer pre-processing, and particularly relates to a wafer cleaning device and a cleaning method based on megasonic waves. Background Art

[0002] A wafer refers to a silicon wafer used to fabricate silicon semiconductor circuits, and its raw material is silicon. High-purity polysilicon is dissolved and doped with a silicon crystal seed, and then slowly pulled out to form a cylindrical single-crystal silicon. After the silicon ingot is ground, polished, and sliced, a silicon wafer is formed, that is, a wafer. The cleanliness of the wafer surface directly affects the yield of chips. Therefore, the wafer needs to be specially cleaned before lithography;

[0003] Existing wafer cleaning devices, such as the wafer cleaning device disclosed in the Chinese patent application with the publication number CN111312631A and the device and method for cleaning wafers disclosed in the Chinese patent application with the publication number CN118800681A. When such wafer cleaning devices clean wafers, they often need to clamp the sides of the wafers, resulting in the lithography surface of the wafers being collided externally, thereby generating a risk of reducing the chip yield in wafer production and having poor safety. Summary of the Invention

[0004] In order to overcome the above technical problems, the purpose of the present invention is to provide a wafer cleaning device and a cleaning method based on megasonic waves, so as to solve the problem in the prior art that when a wafer cleaning device cleans a wafer, it needs to clamp the side of the wafer, resulting in the lithography surface of the wafer being collided externally, generating a risk of reducing the chip yield in wafer production.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] In the first aspect of the present invention, a wafer cleaning device based on megasonic waves is provided, including a cleaning tank, on the top of which a transport track is arranged. A megasonic wave generator is installed inside the cleaning tank. A wafer transport rack is slidably arranged inside the transport track. The bottom of the wafer transport rack simultaneously clamps a plurality of movable wafer bodies. A detection camera is installed on the transport track. The detection camera is used to collect the oblique-angle photos of the lithography surface of the wafer bodies, and based on the oblique-angle photos of the lithography surface, the humidity data of the wafer bodies is identified. A symmetric air-drying mechanism is arranged on one side of the cleaning tank. The wafer transport rack interleaves and confines the plurality of wafer bodies it clamps on the top surface of the symmetric air-drying mechanism. While the symmetric air-drying mechanism applies symmetric blowing to the surface of the wafer bodies, it makes the wafer bodies rotate along a vertical plane, and determines the time for the symmetric air-drying mechanism to apply symmetric blowing to the surface of the wafer bodies based on the humidity data.

[0007] As a further solution of the present invention: the wafer transport rack includes a moving rack, a lifting platform is installed on the bottom surface of the moving rack, and a plurality of clamping mechanisms are installed on the bottom surface of the lifting platform.

[0008] As a further solution of the present invention: the moving rack includes a rectangular frame, track sliders matching the transport track are fixedly connected to the positions near the transport track at both ends of the rectangular frame, vertical hydraulic cylinders are fixedly connected to the four corners of the top surface of the rectangular frame, and the bottom end of the hydraulic cylinder is connected with a telescopic rod.

[0009] As a further solution of the present invention: the lifting platform includes a rectangular platform, a plurality of groups of mounting seats are installed on the bottom surface of the rectangular platform, each group of mounting seats is directly installed with a threaded rod through a bearing, a moving seat is nested on the side surface of the threaded rod, and the end of the telescopic rod away from the hydraulic cylinder is fixedly connected to the top surface of the rectangular platform.

[0010] As a further solution of the present invention: the clamping mechanism includes an arc-shaped frame, a hydraulic cavity is opened inside the arc-shaped frame, arc-shaped arms are inserted at both ends of the arc-shaped frame, a movable pulley seat is fixedly connected to the end of the arc-shaped arm away from the arc-shaped frame, and at least one fixed pulley is installed on the bottom surface of the arc-shaped frame.

[0011] As a further solution of the present invention: the axle of the fixed pulley and the axle of the movable pulley seat are on the same circle.

[0012] As a further solution of the present invention: the pulleys in the fixed pulley and the movable pulley seat are both made of rubber.

[0013] As a further solution of the present invention: the symmetric air-drying mechanism includes an air-drying platform, an air-drying groove is opened on the top surface of the air-drying platform, a plurality of support seats are fixedly connected to the inner bottom surface of the air-drying groove, and a driving pulley is installed at the center position of the top surface of the support seat.

[0014] As a further solution of the present invention: rotating arms are installed at the center positions on both sides of the support seat, a ventilation groove is opened inside the rotating arm, a plurality of ventilation holes are evenly opened on one side of the rotating arm, the plurality of ventilation holes are communicated with the ventilation groove, a blower is arranged inside the air-drying platform, and the output end of the blower is communicated with the ventilation groove.

[0015] As a further solution of the present invention: the humidity data is the specific area fraction of water stains on the wafer body.

[0016] The second aspect of the present invention is to provide a wafer cleaning method based on megasonic waves. This wafer cleaning method is realized based on the above-mentioned wafer cleaning device based on megasonic waves, and includes the following steps:

[0017] S1: The wafer transport rack transports a group of wafer bodies into the cleaning tank and completely immerses the wafer bodies in the cleaning liquid inside the cleaning tank;

[0018] S2: Turn on the megasonic wave generator installed inside the cleaning tank, and perform megasonic wave cleaning on the wafer body inside the cleaning tank;

[0019] S3: The wafer transport rack takes out the cleaned wafer body from the inside of the cleaning tank and transports it to the top of the symmetric air drying mechanism through the transport track;

[0020] S4: The wafer transport rack adjusts a group of wafer bodies on the bottom surface from the overlapping state to the staggered and separated state, increasing the gap between the wafer bodies in this group;

[0021] S5: Use the detection camera to collect the oblique angle photos of the lithography surface of the wafer body, and identify the humidity data of the wafer body based on the oblique angle photos of the lithography surface;

[0022] S6: The wafer transport rack transports the wafer bodies in the staggered and separated state to the top surface of the symmetric air drying mechanism. The symmetric air drying mechanism applies symmetric blowing to the sides of the wafer bodies. The symmetric air drying mechanism simultaneously rotates the wafer bodies along the vertical direction, and determines the time for the symmetric air drying mechanism to apply symmetric blowing to the sides of the wafer bodies based on the humidity data;

[0023] S7: The wafer transport rack adjusts the wafer bodies in the staggered and separated state to the overlapping state, and then transports the wafer bodies in the overlapping state into the packing box.

[0024] 1. In the present invention, the wafer transport rack can stagger and limit a plurality of wafer bodies held on the top surface of the symmetric air drying mechanism, which will greatly increase the gap between the wafer bodies, facilitating the air drying treatment of the surface of the wafer bodies by the symmetric air drying mechanism. Since the symmetric air drying mechanism applies symmetric wind force to the surface of the wafer bodies, when the wafer bodies are under the action of a large wind force, the acting forces on both sides of the wafer bodies will cancel each other out, ensuring that the wafer bodies will not deform, guaranteeing the safety of the wafer bodies, and while improving the air drying efficiency of the wafer bodies, the wafer bodies are not easily broken.

[0025] 2. In the present invention, when the clamping mechanism needs to release the wafer body, turn on the oil cylinder arranged in the connecting block. The oil cylinder can absorb the hydraulic oil in the hydraulic cavity through the connecting block, causing the arc-shaped arm to automatically contract, so that the wafer body held by the clamping mechanism will freely detach. When the clamping mechanism needs to clamp the wafer body, the reverse operation is performed to make the arc-shaped arm automatically unfold. The wheel surfaces of the fixed pulley and the movable pulley seat are both concave surfaces, which fit with the arc-shaped end surface of the wafer body. During the entire process of the clamping mechanism transporting the wafer body, the clamping mechanism only contacts the end surface of the wafer body rather than the side surface, ensuring that the side surface of the wafer body will not be touched by external machinery, improving the protection effect of the wafer body. Description of the Drawings

[0026] The present invention will be further described below in conjunction with the accompanying drawings.

[0027] Figure 1 It is a schematic structural diagram of the left side of the wafer cleaning device based on megasonic waves of the present invention;

[0028] Figure 2 It is a schematic structural diagram of the right side of the wafer cleaning device based on megasonic waves of the present invention;

[0029] Figure 3 It is a schematic structural diagram of the wafer transport rack in the present invention;

[0030] Figure 4 It is a schematic structural diagram of the moving rack and the lifting table in the present invention;

[0031] Figure 5 It is a schematic structural diagram of the clamping mechanism in the present invention when the clamping state is released;

[0032] Figure 6 It is a schematic structural diagram of the clamping mechanism in the present invention when the clamping state is applied;

[0033] Figure 7 It is a schematic internal structure diagram of the clamping mechanism in the present invention;

[0034] Figure 8 It is a schematic structural diagram of the symmetric air drying mechanism in the present invention.

[0035] Description of the drawings: 1. Cleaning tank; 2. Transport track; 21. Column; 3. Wafer transport rack; 31. Moving rack; 311. Rectangular frame; 312. Track slider; 313. Hydraulic cylinder; 314. Telescopic rod; 32. Lifting table; 321. Rectangular table; 322. Mounting seat; 323. Threaded rod; 324. Moving seat; 33. Clamping mechanism; 331. Arc-shaped frame; 332. Connecting block; 333. Fixed pulley; 334. Arc-shaped arm; 335. Movable pulley seat; 336. Hydraulic cavity; 4. Symmetric air drying mechanism; 41. Air drying table; 42. Air drying groove; 43. Support seat; 44. Driving pulley; 45. Rotating arm; 5. Wafer body. Detailed implementation manners

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] Embodiment 1

[0038] As Figures 1 - 8As shown in the figure, the present invention discloses a wafer cleaning device based on megasonic waves, including a cleaning tank 1, on the top of which a transport track 2 is arranged, and a megasonic wave generator is installed inside the cleaning tank 1. It should be noted that four vertically arranged columns 21 are fixedly connected to the top surface of the cleaning tank 1, and the transport track 2 is horizontally installed on the four vertically arranged columns 21. The specifications and length of the transport track 2 are adaptively selected by those skilled in the art according to the pre-treatment site conditions of the wafer body 5. The transport track 2 can also be arc-shaped, as long as it can normally drive the wafer transport rack 3. Therefore, the driving method of the transport track 2 is not limited to electric control, pneumatic control or other mechanical driving methods. For example, the wafer transport rack 3 can be driven by a chain. The megasonic wave generator is a device specifically used to generate ultrasonic waves. The frequency of the megasonic wave generator is between 1 GHz and 1 THz. The specific frequency value is adaptively selected by those skilled in the art according to the cleaning time of the wafer body 5 and the cleaning temperature of the wafer body 5. The model of the megasonic wave generator, the number and installation position inside the cleaning tank 1 are adaptively selected by those skilled in the art. In theory, the megasonic wave generator can be installed at any position inside the cleaning tank 1. A wafer transport rack 3 is slidably arranged inside the transport track 2, and several movable wafer bodies 5 are clamped at the bottom of the wafer transport rack 3. It should be noted that multiple wafer bodies 5 can be clamped at the bottom of one wafer transport rack 3, and the multiple wafer bodies 5 are in a vertically overlapping state to ensure the cleaning efficiency of the cleaning tank 1 for the wafer bodies 5. A symmetric air drying mechanism 4 is arranged on one side of the cleaning tank 1. The wafer transport rack 3 staggers and confines several wafer bodies 5 it clamps on the top surface of the symmetric air drying mechanism 4. While the symmetric air drying mechanism 4 applies symmetric blowing to the surface of the wafer bodies 5, it makes the wafer bodies 5 rotate along the vertical plane. It should be noted that the wafer transport rack 3 can stagger and confine several wafer bodies 5 it clamps on the top surface of the symmetric air drying mechanism 4, which will greatly increase the gap between the wafer bodies 5 and facilitate the air drying treatment of the surface of the wafer bodies 5 by the symmetric air drying mechanism 4. A blower should be arranged inside the symmetric air drying mechanism 4, and the blower can apply wind force to the surface of the wafer bodies 5. In addition, it should be noted that a nitrogen cylinder is arranged inside the symmetric air drying mechanism 4, and the output end of the nitrogen cylinder is connected to the output end of the blower to ensure that the wind applied by the blower to the surface of the wafer bodies 5 is nitrogen. As an inert gas, nitrogen can improve the protection effect on the wafer bodies 5 while air drying the wafer bodies 5. Since the symmetric air drying mechanism 4 applies symmetric wind force to the surface of the wafer bodies 5, when the wafer bodies 5 are subjected to a large wind force, the acting forces on both sides of the wafer bodies 5 will cancel each other out, ensuring that the wafer bodies 5 will not deform and guaranteeing the safety of the wafer bodies 5. While improving the air drying efficiency of the wafer bodies 5, the wafer bodies 5 are not easily broken.

[0039] Embodiment 2

[0040] As Figures 1 to 8 shown, the wafer transport rack 3 includes a moving rack 31. A lifting platform 32 is installed on the bottom surface of the moving rack 31, and a plurality of clamping mechanisms 33 are installed on the bottom surface of the lifting platform 32. The moving rack 31 includes a rectangular frame 311. At positions near the transport track 2 at both ends of the rectangular frame 311, there are fixedly connected track sliders 312 that match the transport track 2. At the four corners of the top surface of the rectangular frame 311, there are fixedly connected vertically arranged hydraulic cylinders 313. The bottom end of the hydraulic cylinder 313 is connected with a telescopic rod 314. It should be noted that since the track sliders 312 that match the transport track 2 are fixedly connected at positions near the transport track 2 at both ends of the rectangular frame 311, the rectangular frame 311 can slide horizontally along the inner side of the transport track 2 through the cooperation of the track sliders 312 and the transport track 2. Additionally, it should be noted that the transport track 2 can normally drive the wafer transport rack 3. Therefore, the driving method of the transport track 2 is not limited to electric control, pneumatic control, or other mechanical driving methods. For example, the wafer transport rack 3 can be driven by a chain, or the wafer transport rack 3 can be driven by a lead screw and nut. The specific driving method is adaptively selected by those skilled in the art according to the actual situation of the transport track 2; the telescopic rod 314 can be composed of multiple nested hollow tubes. The main purpose is to control the height of the lifting platform 32 through the hydraulic cylinder 313 and the telescopic rod 314, and it can ensure that the lifting platform 32 can completely immerse the wafer body 5 in the cleaning liquid inside the cleaning tank 1. The cleaning liquid inside the cleaning tank 1 can be deionized water, which is specifically adaptively selected by those skilled in the art according to the requirements of the wafer body 5. The number of the clamping mechanisms 33 is the same as the number of the wafer bodies 5, that is, one clamping mechanism 33 clamps one wafer body 5. The clamping mechanisms 33 can restrict the wafer bodies 5 to be overlapped at equal intervals on the bottom surface of the lifting platform 32. In this way, the lifting platform 32 can drive the wafer bodies 5 through the clamping mechanisms 33 to realize the transfer of the wafer bodies 5.

[0041] The lifting table 32 includes a rectangular table 321. A number of groups of mounting seats 322 are installed on the bottom surface of the rectangular table 321. Each group of mounting seats 322 directly mounts a threaded rod 323 through a bearing. A moving seat 324 is nested on the side surface of the threaded rod 323. One end of the telescopic rod 314 away from the hydraulic cylinder 313 is fixedly connected to the top surface of the rectangular table 321. It should be noted that the mounting seats 322 are symmetrically arranged on the bottom surface of the rectangular table 321, and the threaded rod 323 at the bottom surface of the rectangular table 321 and the moving seat 324 on its side surface are alternately divided into two groups. Then, two driving mechanisms are arranged inside the rectangular table 321 to drive the moving seats 324 on the sides of the two groups of threaded rods 323 to both sides of the bottom surface of the rectangular table 321 respectively. The moving seats 324 in the same group can be fixedly connected by a long rod to ensure that the moving seats 324 in the same group can move synchronously. Then, a horizontal linear driving mechanism is arranged inside the rectangular table 321. The horizontal linear driving mechanism can be an electric push rod, a hydraulic push rod or a pneumatic push rod. By pushing the long rod through the output end of the horizontal linear driving mechanism, the moving seats 324 in the same group can be moved. The bottom surface of the moving seat 324 is fixedly connected to the top of the clamping mechanism 33. Therefore, the moving moving seat 324 can drive the clamping mechanism 33 to move synchronously;

[0042] When the wafer transport rack 3 needs to transport the wafer body 5 into the cleaning tank 1 for megasonic cleaning, multiple wafer bodies 5 need to be overlapped. Therefore, the two groups of moving seats 324 can be adjusted to be on the same straight line through the horizontal linear driving mechanism. In this way, the wafer bodies 5 corresponding to the two groups of moving seats 324 are also on the same straight line, that is, overlapped. At this time, when the lifting table 32 moves downward, the wafer body 5 can be driven to move downward through the clamping mechanism 33. By controlling the height of the downward movement of the lifting table 32, the wafer body 5 can be completely immersed in the cleaning liquid inside the cleaning tank 1;

[0043] When the wafer transport rack 3 needs to transport the wafer body 5 to the top of the symmetric air drying mechanism 4 for air drying operation, multiple wafer bodies 5 need to be staggered from each other. Therefore, the two groups of moving seats 324 can be adjusted to both sides of the bottom surface of the rectangular table 321 through the horizontal linear driving mechanism. At this time, the positions of multiple wafer bodies 5 will be staggered from each other, so that the gaps between multiple wafer bodies 5 will be greatly increased. Then, the symmetric air drying mechanism 4 can be used to perform the air drying operation on the wafer body 5.

[0044] The clamping mechanism 33 includes an arc-shaped frame 331. A hydraulic chamber 336 is provided inside the arc-shaped frame 331. Arc-shaped arms 334 that are movable are inserted at both ends of the arc-shaped frame 331. A movable pulley seat 335 is fixedly connected to the end of the arc-shaped arm 334 away from the arc-shaped frame 331. At least one fixed pulley 333 is installed on the bottom surface of the arc-shaped frame 331. The axle of the fixed pulley 333 and the axle of the movable pulley seat 335 are on the same circle. The pulleys in the fixed pulley 333 and the movable pulley seat 335 are both made of rubber. It should be noted that when the clamping mechanism 33 needs to release the wafer body 5, the oil cylinder provided in the connecting block 332 is opened. The oil cylinder can absorb the hydraulic oil in the hydraulic chamber 336 through the connecting block 332, causing the arc-shaped arms 334 to automatically contract. In this way, the wafer body 5 clamped by the clamping mechanism 33 will be freely detached. And during the automatic detachment process of the wafer body 5, the clamping mechanism 33 only contacts the end face of the wafer body 5 instead of the side face, ensuring that the side face of the wafer body 5 will not be touched by external machinery, improving the protection effect of the wafer body 5. When the clamping mechanism 33 needs to clamp the wafer body 5, the reverse operation is performed to make the arc-shaped arms 334 automatically expand. It should be noted that the arc-shaped arms 334 need to cover a length exceeding half of the circumference of the wafer body 5 to ensure that the wafer body 5 is fixed inside the clamping mechanism 33. The wheel surfaces of the fixed pulley 333 and the movable pulley seat 335 are both concave surfaces, which fit the arc-shaped end face of the wafer body 5. During the entire process of the clamping mechanism 33 transporting the wafer body 5, the clamping mechanism 33 will not contact the side face of the wafer body 5.

[0045] Embodiment 3

[0046] A detection camera (not shown in the drawings) is installed on the transport track 2. The detection camera is used to collect the oblique angle photos of the lithography surface of the wafer body 5, and identify the moisture data of the wafer body 5 based on the oblique angle photos of the lithography surface. The moisture data is the specific area fraction of the water stains on the wafer body 5. It should be noted that the detection camera is adaptively installed by those skilled in the art according to the transport track 2 and the oblique angle photos of the lithography surface to be photographed. In order to clearly photograph the oblique angle photos of the lithography surface of each wafer body 5, the detection camera needs to be movably installed on the transport track 2 and can move along the transverse direction of the moving frame 31 to ensure that the detection camera can photograph the oblique angle photos of the lithography surface of each wafer body 5. The wafer bodies 5 are numbered. Those skilled in the art pre-photograph the wafer bodies 5 through the detection camera, and select the photographing position and the number of photographing times of the detection camera according to the number of clear and complete oblique angle photos of the lithography surface in the photographed photos;

[0047] For example, when the number of clear and complete photos of the beveled photoetching surface in the photos taken by the detection camera is 5, the first shot can be taken at the wafer body 5 labeled 3, and the second shot can be taken at the wafer body 5 labeled 7 until all the beveled photoetching surface photos of the wafer body 5 are collected.

[0048] Then, perform grayscale processing on the beveled photoetching surface photos of the wafer body 5 to obtain beveled photoetching surface grayscale images;

[0049] Extract the feature regions in the beveled photoetching surface grayscale images, where the feature regions are the regions of the photoetching surface in the beveled photoetching surface grayscale images;

[0050] Divide the feature regions into n pixels, and those skilled in the art pre-collect the grayscale values of the n pixels of the feature regions without water stains 、 、…… ,and use 、 、…… as the comparison grayscale values;

[0051] Collect the grayscale values of the feature regions corresponding to the wafer body 5 、 、…… ;

[0052] Calculate the grayscale value variance σ of the feature regions corresponding to the wafer body 5. The calculation formula of σ is:

[0053] ;

[0054] When there is no water stain on the photoetching surface of the wafer body 5, then , at this time the grayscale value variance σ = 0. When the photoetching surface of the wafer body 5 is covered with water stains, the grayscale value variance σ of the feature regions corresponding to the wafer body 5 will reach the maximum value. Therefore, the grayscale value variance σ is directly proportional to the specific area fraction S of the water stains on the wafer body 5. Those skilled in the art use a computer to fit the mathematical relationship between the specific area fraction S and the grayscale value variance σ;

[0055] After collecting the beveled photoetching surface grayscale images of the wafer body 5 through the detection camera, calculate the grayscale value variance σ of the feature regions of the beveled photoetching surface grayscale images, and calculate the specific area fraction S corresponding to the grayscale value variance σ according to the mathematical relationship;

[0056] A fraction threshold of the specific surface area fraction S is preset by those skilled in the art. When the specific surface area fraction S is greater than or equal to the fraction threshold, the symmetric air-drying mechanism 4 adopts a long-time working mode. When the specific surface area fraction S is less than the fraction threshold, the symmetric air-drying mechanism 4 adopts a short-time working mode. Additionally, it should be noted that the long-time working mode and the short-time working mode of the symmetric air-drying mechanism 4 are adaptively selected by those skilled in the art according to the air-drying condition of the water stains on the lithography surface of the wafer body 5, ensuring that the water stains on the lithography surface of the wafer body 5 can be completely air-dried.

[0057] The symmetric air-drying mechanism 4 includes an air-drying table 41. An air-drying groove 42 is formed on the top surface of the air-drying table 41. A plurality of support seats 43 are fixedly connected to the inner bottom surface of the air-drying groove 42. A driving pulley 44 is installed at the central position of the top surface of the support seat 43.

[0058] Rotating arms 45 are installed at the central positions on both sides of the support seat 43. A ventilation groove is formed inside the rotating arm 45. A plurality of ventilation holes are evenly formed on one side of the rotating arm 45. The plurality of ventilation holes are all communicated with the ventilation groove. A blower is arranged inside the air-drying table 41. The output end of the blower is communicated with the ventilation groove. When air-drying the lithography surface of the wafer body 5, first use a detection camera to collect an oblique-angle photo of the lithography surface of the wafer body 5, then perform grayscale processing on the oblique-angle photo of the lithography surface to obtain an oblique-angle grayscale picture of the lithography surface, extract the feature region in the oblique-angle grayscale picture of the lithography surface, calculate the variance σ of the grayscale value of the feature region, and then use a mathematical relationship to calculate the specific surface area fraction S corresponding to the variance σ of the grayscale value. Compare the specific surface area fraction S with the fraction threshold. If the specific surface area fraction S is greater than or equal to the fraction threshold, the symmetric air-drying mechanism 4 adopts a long-time working mode. If the specific surface area fraction S is less than the fraction threshold, the symmetric air-drying mechanism 4 adopts a short-time working mode. When the symmetric air-drying mechanism 4 works, the wind conveyed by the blower can be conveyed to the side of the wafer body 5 through the ventilation holes and the ventilation groove to air-dry the side of the wafer body 5. Since the air-drying time of the symmetric air-drying mechanism 4 is adjusted by the specific surface area fraction S, the symmetric air-drying mechanism 4 can accurately air-dry the water stains on the lithography surface of the wafer body 5.

[0059] Embodiment 4

[0060] Different from Embodiment 3, a convolutional neural network (CNN) is used to identify the grade of the specific surface area fraction S of the water stains on the wafer body 5. For example, the grade of the specific surface area fraction S of the water stains on the wafer body 5 is divided into five grades, which are respectively:

[0061] The first grade: 0%≦S<20%, the second grade: 20%≦S<40%, the third grade: 40%≦S<60%, the fourth grade: 60%≦S<80% and the fifth grade: S≥80%;

[0062] The method for identifying the level of the specific area fraction S of water stains on the wafer body 5 by a convolutional neural network includes the following steps:

[0063] First, collect a historical training data set, which is a large number of oblique-angle photos of the lithography surface of the wafer body 5. The oblique-angle photos of the lithography surface of the wafer body 5 are collected by those skilled in the art during the process of using a megasonic-based wafer cleaning device. Specifically, the oblique-angle photos of the lithography surface of the wafer body 5 are collected through a detection camera. Additionally, it should be noted that the oblique-angle photos of the lithography surface of the wafer body 5 should preferably contain different amounts of water stains to improve the accuracy of convolutional neural network training;

[0064] Then, those skilled in the art label the levels of the oblique-angle photos of the lithography surface of the wafer body 5. Classification is based on the size of the specific area fraction S of water stains on the wafer body 5, and specifically, it can be divided into five levels;

[0065] Next, preprocess the oblique-angle photos of the lithography surface, including operations such as adjusting the image size, grayscale conversion, and normalization.

[0066] Select the VGGNet or ResNet convolutional neural network architecture, and then train the convolutional neural network model for identifying the level of the specific area fraction S of water stains on the wafer body 5. Update the parameters of the model through the backpropagation algorithm to enable the model to gradually learn the mapping relationship between the specific area fraction S of water stains and the five levels. During the training process, regularly evaluate the performance of the model on the validation set and observe indicators such as accuracy and recall to prevent overfitting of the model.

[0067] When the convolutional neural network model for identifying the level of the specific area fraction S of water stains on the lithography surface of the wafer body 5 is trained, the detection camera can be used to collect the oblique-angle photos of the lithography surface of the wafer body 5, and then the convolutional neural network model is used to identify the level of the corresponding specific area fraction S of the oblique-angle photo of the lithography surface. Since the level of the specific area fraction S is divided into five levels, the drying time of the symmetric air-drying mechanism 4 can also be divided into five levels. Specifically, those skilled in the art can make adaptive adjustments according to the working efficiency of the symmetric air-drying mechanism 4 to ensure that the symmetric air-drying mechanism 4 can completely dry the water stains on the lithography surface of the wafer body 5;

[0068] It should be noted that since the symmetric air-drying mechanism 4 adopts the same working mode, the drying time level of the symmetric air-drying mechanism 4 can be determined according to the maximum level of the specific area fraction S corresponding to the oblique-angle photo of the lithography surface;

[0069] It is also possible to label the rotating arms 45 on the symmetric air-drying mechanism 4, with the labels corresponding one-to-one to the labels of the wafer body 5. An electromagnetic valve is provided inside the ventilation groove corresponding to the rotating arm 45 to control the drying time of different rotating arms 45 for different wafer bodies 5 according to the electromagnetic valve;

[0070] For example, the inspection camera captures an oblique-angle photo of the lithography surface of the wafer body 5 numbered j, and through the convolutional neural network model, it is recognized that the level of the specific surface area fraction S of the oblique-angle photo of the lithography surface of the wafer body 5 numbered j is the third level. Then, the air-drying time of the rotating arm 45 numbered j should also be the third level, so as to accurately control the air-drying time of different wafer bodies 5.

[0071] Embodiment 5

[0072] As Figures 1 - 8 shown, the present invention discloses a wafer cleaning method based on megasonic waves. This wafer cleaning method is implemented based on the above-mentioned wafer cleaning device based on megasonic waves, and includes the following steps:

[0073] S1: The wafer transport rack 3 transports a group of wafer bodies 5 into the interior of the cleaning tank 1, and immerses the wafer bodies 5 completely in the cleaning liquid inside the cleaning tank 1. Four vertically arranged columns 21 are fixedly connected to the top surface of the cleaning tank 1, and the transport track 2 is horizontally installed on the four vertically arranged columns 21. The specifications and lengths of the transport track 2 are adaptively selected by those skilled in the art according to the pre-treatment site conditions of the wafer body 5. The transport track 2 can also be arc-shaped, as long as it can drive the wafer transport rack 3 normally. Therefore, the driving method of the transport track 2 is not limited to electric control, pneumatic control or other mechanical driving methods. For example, the wafer transport rack 3 is driven by a chain. Since the two ends of the rectangular frame 311 are fixedly connected with track sliders 312 matching the transport track 2 near the transport track 2, the rectangular frame 311 can slide horizontally along the inner side of the transport track 2 through the cooperation of the track sliders 312 and the transport track 2. In addition, it should be noted that as long as the transport track 2 can drive the wafer transport rack 3 normally, the driving method of the transport track 2 is not limited to electric control, pneumatic control or other mechanical driving methods. For example, the wafer transport rack 3 can be driven by a chain, or it can also be driven by a lead screw nut. The specific driving method is adaptively selected by those skilled in the art according to the actual situation of the transport track 2. The telescopic rod 314 can be composed of multiple nested hollow tubes. The main purpose is to control the height of the lifting platform 32 through the hydraulic cylinder 313 and the telescopic rod 314, so as to ensure that the lifting platform 32 can immerse the wafer body 5 completely in the cleaning liquid inside the cleaning tank 1. The cleaning liquid inside the cleaning tank 1 can be deionized water, which is specifically adaptively selected by those skilled in the art according to the requirements of the wafer body 5. The number of the clamping mechanisms 33 is the same as the number of the wafer bodies 5, that is, one clamping mechanism 33 clamps one wafer body 5. The clamping mechanism 33 can restrict the wafer bodies 5 to be overlapped at equal intervals on the bottom surface of the lifting platform 32. In this way, the lifting platform 32 can drive the wafer body 5 through the clamping mechanism 33 to realize the transfer of the wafer body 5;

[0074] S2: Turn on the megasonic wave generator installed inside the cleaning tank 1 to perform megasonic wave cleaning on the wafer body 5 inside the cleaning tank 1. The megasonic wave generator is a device specifically used to generate ultrasonic waves. The frequency of the megasonic wave generator is between 1 GHz and 1 THz. The specific frequency value is adaptively selected by those skilled in the art according to the cleaning time of the wafer body 5 and the cleaning temperature of the wafer body 5. The model of the megasonic wave generator, the number set inside the cleaning tank 1, and the installation position are adaptively selected by those skilled in the art. Theoretically, the megasonic wave generator can be installed at any position inside the cleaning tank 1;

[0075] S3: The wafer transport rack 3 takes out the cleaned wafer body 5 from inside the cleaning tank 1 and transports it to the top of the symmetric air drying mechanism 4 through the transport track 2;

[0076] S4: The wafer transport rack 3 adjusts a group of wafer bodies 5 on the bottom surface from an overlapping state to an interleaved and separated state, increasing the gap between the group of wafer bodies 5. When the wafer transport rack 3 needs to transport the wafer body 5 to the top of the symmetric air drying mechanism 4 for air drying operation, multiple wafer bodies 5 need to be staggered with each other. Therefore, the two sets of moving seats 324 can be adjusted to both sides of the bottom surface of the rectangular table 321 through the horizontal linear drive mechanism. At this time, the positions of multiple wafer bodies 5 will be staggered with each other, so that the gap between multiple wafer bodies 5 will be greatly increased. Then, the symmetric air drying mechanism 4 can be used to perform air drying operation on the wafer body 5;

[0077] S5: Use the detection camera to collect the oblique angle photos of the lithography surface of the wafer body 5, and identify the moisture data of the wafer body 5 based on the oblique angle photos of the lithography surface. The moisture data is the specific area fraction of the water stains on the wafer body 5. The determination method of the specific area fraction S is:

[0078] A detection camera (not shown in the attached figure) is installed on the transport track 2. The detection camera is used to collect the oblique angle photos of the lithography surface of the wafer body 5, and identify the moisture data of the wafer body 5 based on the oblique angle photos of the lithography surface. The moisture data is the specific area fraction of the water stains on the wafer body 5. It should be noted that the detection camera is adaptively installed by those skilled in the art according to the transport track 2 and the oblique angle photos of the lithography surface to be taken. In order to clearly take the oblique angle photos of the lithography surface of each wafer body 5, the detection camera needs to be movably installed on the transport track 2 and can move horizontally along the moving frame 31 to ensure that the detection camera can take the oblique angle photos of the lithography surface of each wafer body 5. Label the wafer body 5. Those skilled in the art pre-take photos of the wafer body 5 through the detection camera, and select the shooting position and shooting times of the detection camera according to the number of clear and complete oblique angle photos of the lithography surface in the taken photos;

[0079] For example, when the number of clear and complete photos of the beveled photolithography surface in the photos taken by the detection camera is 5, the first shot can be taken at the wafer body 5 labeled 3, and the second shot can be taken at the wafer body 5 labeled 7 until all the beveled photolithography surface photos of the wafer body 5 are collected.

[0080] Then, the photos of the beveled photolithography surface of the wafer body 5 are grayscaled to obtain beveled photolithography surface grayscale images;

[0081] Extract the feature regions in the beveled photolithography surface grayscale images, where the feature regions are the regions of the photolithography surface in the beveled photolithography surface grayscale images;

[0082] The feature regions are divided into n pixels, and those skilled in the art pre-collect the grayscale values of the n pixels of the feature regions without water stains 、 、…… , and use 、 、…… as the comparison grayscale values;

[0083] Collect the grayscale values of the feature regions corresponding to the wafer body 5 、 、…… ;

[0084] Calculate the variance σ of the grayscale values of the feature regions corresponding to the wafer body 5. The calculation formula of σ is:

[0085] ;

[0086] When there is no water stain on the photolithography surface of the wafer body 5, then , at this time the variance of grayscale values σ = 0. When the photolithography surface of the wafer body 5 is covered with water stains, the variance of grayscale values σ of the feature regions corresponding to the wafer body 5 will reach the maximum value. Therefore, the variance of grayscale values σ is proportional to the specific area fraction S of water stains on the wafer body 5. Those skilled in the art use a computer to fit the mathematical relationship between the specific area fraction S and the variance of grayscale values σ;

[0087] After the beveled photolithography surface grayscale images of the wafer body 5 are collected by the detection camera, calculate the variance σ of the grayscale values of the feature regions of the beveled photolithography surface grayscale images, and calculate the specific area fraction S corresponding to the variance of grayscale values σ according to the mathematical relationship;

[0088] S6: The wafer carrier 3 transports the wafer body 5 in an interleaved and separated state to the top surface of the symmetric air-drying mechanism 4. The symmetric air-drying mechanism 4 applies symmetric blowing to the side surfaces of the wafer body 5, and at the same time, the symmetric air-drying mechanism 4 rotates the wafer body 5 along the vertical direction. Since the symmetric air-drying mechanism 4 applies symmetric wind force to the surface of the wafer body 5, the air-drying time is determined by the humidity data. Specifically, first, a detection camera is used to collect the oblique-angle photo of the lithography surface of the wafer body 5, then the oblique-angle photo of the lithography surface is grayscale processed to obtain an oblique-angle grayscale image of the lithography surface. The feature area in the oblique-angle grayscale image of the lithography surface is extracted, the variance σ of the grayscale value of the feature area is calculated, and then the specific surface area fraction S corresponding to the variance σ of the grayscale value is calculated using a mathematical relationship. The specific surface area fraction S is compared with a fraction threshold. If the specific surface area fraction S is greater than or equal to the fraction threshold, the symmetric air-drying mechanism 4 adopts a long-time working mode. If the specific surface area fraction S is less than the fraction threshold, the symmetric air-drying mechanism 4 adopts a short-time working mode. When the symmetric air-drying mechanism 4 works, the wind force conveyed by the blower can be conveyed to the side surface of the wafer body 5 through the ventilation holes and ventilation grooves to air-dry the side surface of the wafer body 5. Since the air-drying time of the symmetric air-drying mechanism 4 is adjusted by the specific surface area fraction S, the symmetric air-drying mechanism 4 can accurately air-dry the water stains on the lithography surface of the wafer body 5;

[0089] Therefore, when the wafer body 5 is under the action of a large wind force, the acting forces on both sides of the wafer body 5 will cancel each other out, ensuring that the wafer body 5 will not deform, guaranteeing the safety of the wafer body 5, and while improving the air-drying efficiency of the wafer body 5, the wafer body 5 is not easily broken;

[0090] S6: The wafer carrier 3 adjusts the wafer body 5 in an interleaved and separated state to an overlapping state, and then transports the wafer body 5 in the overlapping state into a packing box, realizing the cleaning and packing of the wafer body 5.

[0091] The above has described a specific embodiment of the present invention in detail, but the content described is only a preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A wafer cleaning device based on megasonic waves, characterized in that: include: A cleaning box, the top of which is provided with a transport track, and a megasonic generator is installed inside the cleaning box; A wafer transport rack is slidably arranged on the inner side of the transport track, and the bottom of the wafer transport rack simultaneously clamps a plurality of movable wafer bodies; A detection camera is installed on the transport track, and is used to collect oblique angle photos of the photolithography surface of the wafer body, and identify moisture data of the wafer body based on the oblique angle photos of the photolithography surface; A symmetrical air-drying mechanism is arranged on one side of the cleaning box. The wafer transport rack staggers and restricts a plurality of wafer bodies clamped therein to the top surface of the symmetrical air-drying mechanism. The symmetrical air-drying mechanism applies symmetrical blowing to the surface of the wafer body while rotating the wafer body along a vertical plane. The time for the symmetrical air-drying mechanism to apply symmetrical blowing to the surface of the wafer body is determined based on the moisture data. The wafer transport rack comprises a mobile rack, a lifting platform is installed on the bottom surface of the mobile rack, and a plurality of clamping mechanisms are installed on the bottom surface of the lifting platform; The mobile frame comprises a rectangular frame, two ends of the rectangular frame are fixedly connected to track sliders matching the transport track, four corners of the top surface of the rectangular frame are fixedly connected to vertically arranged hydraulic cylinders, and the bottom end of the hydraulic cylinder is connected to a telescopic rod; The lifting platform comprises a rectangular platform, a plurality of groups of mounting seats are installed on the bottom surface of the rectangular platform, each group of mounting seats is directly installed with a threaded rod through a bearing, a movable seat is embedded on the side of the threaded rod, and an end of the telescopic rod away from the hydraulic cylinder is fixedly connected to the top surface of the rectangular platform; The clamping mechanism comprises an arc frame, a hydraulic cavity is provided inside the arc frame, movable arc arms are inserted at both ends of the arc frame, one end of the arc arm away from the arc frame is fixedly connected to a movable pulley seat, and at least one fixed pulley is installed on the bottom surface of the arc frame.

2. The wafer cleaning device based on megasonic waves according to claim 1, characterized in that: The wheel axle of the fixed pulley and the wheel axle of the movable pulley seat are on the same circle.

3. The wafer cleaning device based on megasonic waves according to claim 1, characterized in that: The fixed pulley and the pulleys in the movable pulley seat are both made of rubber.

4. The wafer cleaning device based on megasonic waves according to claim 1, characterized in that: The symmetrical air-drying mechanism comprises an air-drying table, the top surface of which is provided with an air-drying groove, the inner bottom surface of which is fixedly connected with a plurality of support seats, and a driving pulley is installed at the center position of the top surface of the support seat.

5. The wafer cleaning device based on megasonic waves according to claim 4, characterized in that: Rotating arms are installed at the center positions of both sides of the support seat, a ventilation groove is opened inside the rotating arms, a plurality of ventilation holes are evenly opened on one side of the rotating arms, and the plurality of ventilation holes are connected to the ventilation groove. A blower is arranged inside the air drying table, and the output end of the blower is connected to the ventilation groove.

6. The wafer cleaning device based on megasonic waves according to claim 1, characterized in that: The moisture data is the specific area fraction of water stains on the wafer body.

7. A wafer cleaning method based on megasonic waves, characterized in that: The wafer cleaning method is implemented based on the wafer cleaning device based on megasonic waves as described in any one of claims 1 to 6. The following steps are involved: S1: The wafer transport rack transports a group of wafer bodies to the inside of the cleaning box, and completely immerses the wafer bodies in the cleaning liquid inside the cleaning box; S2: Turn on the megasonic wave generator installed inside the cleaning box to perform megasonic wave cleaning on the wafer body inside the cleaning box; S3: The wafer transport rack takes out the cleaned wafer body from the inside of the cleaning box and transports it to the top of the symmetrical air-drying mechanism through the transport track; S4: The wafer transport rack adjusts a group of wafer bodies on the bottom surface from an overlapping state to a staggered separation state, so that the gap between the group of wafer bodies is increased; S5: using a detection camera to collect oblique angle photos of the photolithography surface of the wafer body, and identifying moisture data of the wafer body based on the oblique angle photos of the photolithography surface; S6: The wafer transport rack transports the wafer bodies in the staggered and separated state to the top surface of the symmetrical air-drying mechanism, and the symmetrical air-drying mechanism applies symmetrical blowing to the side surfaces of the wafer bodies. The symmetrical air-drying mechanism simultaneously rotates the wafer bodies in the vertical direction, and determines the time for the symmetrical air-drying mechanism to apply symmetrical blowing to the side surfaces of the wafer bodies based on the moisture data; S7: The wafer transport rack adjusts the wafer bodies in the staggered and separated state to an overlapping state, and then transports the wafer bodies in the overlapping state into a packing box.

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