Wafer cleaning device and method based on micro-nano bubble transient cavitation and steady cavitation

Abstract

The application provides a wafer cleaning device and method based on micro-nano bubble transient cavitation and steady cavitation, which comprises a cleaning tank, a micro-nano bubble generating device, a micro-nano bubble generating device gas outlet pipe and a micro-nano bubble generating device liquid inlet pipe. The micro-nano bubble generating device is used for generating micro-nano bubbles, and the main body of the micro-nano bubble generating device is arranged below the cleaning tank. The micro-nano bubble generating device gas outlet pipe is connected with the micro-nano bubble generating device and the cleaning tank, and is arranged below the wafer. The micro-nano bubble generating device liquid inlet pipe is arranged at the bottom of the cleaning tank. An ultrasonic wave emitting device is arranged on the side of the cleaning tank and is used for emitting ultrasonic waves to ultrasonically excite micro-nano bubbles between the wafers. The micro-nano bubbles generate steady cavitation or transient cavitation, and micro-jets are generated to clean the wafers. A control system is arranged below the cleaning tank and is used for controlling the whole cleaning process. The cleaning device and method can significantly improve the accuracy and reliability of the wafer cleaning process.

Description

Technical Field

[0001] This invention relates to the field of acoustic cavitation, and more particularly to a wafer cleaning method for transient and steady-state cavitation of micro-nano bubbles. Background Technology

[0002] Ultrasonic cavitation is a phenomenon unique to ultrasonic waves propagating in liquids. The cavitation effect mainly occurs below 1 MHz. When using high-frequency ultrasonic cleaning above 1 MHz, the cleaning mechanism is not ultrasonic cavitation, but rather the flushing effect of high-frequency pressure waves. The cavitation process is extremely short-lived. During this process, tiny bubbles within the liquid, the cavitation nuclei, vibrate, grow, and continuously accumulate energy under the influence of the ultrasonic field. When the energy reaches a certain threshold, the cavitation bubbles collapse and close rapidly. Tiny bubbles in liquids under the influence of ultrasonic waves can be categorized into steady-state cavitation and transient cavitation.

[0003] When transient cavitation bubbles collapse, they generate outward-spreading shock waves, forming microjets that impact the wall and particles on it. This disrupts the adhesion between the particles and the wall, causing them to detach and achieving a cleaning effect. Steady-state cavitation bubbles continuously expand and contract, making them difficult to collapse. The surrounding liquid flows outward with the expansion of the cavitation bubbles and inward with their compression. Eventually, the flow of the surrounding liquid stabilizes; this phenomenon is called microfluidics. Microfluidics can create shear stress in the surrounding liquid, thereby disrupting the contact between the particles and the wall, achieving a cleaning effect.

[0004] Current ultrasonic cleaning technologies for wafers primarily utilize ultrasonic waves in the 20kHz-100kHz range. The cleaning process removes contaminants from the object's surface through cavitation generated in the liquid. However, in cleaning precision components such as semiconductor devices and optical precision parts, traditional ultrasonic cleaning is insufficient for thoroughly cleaning complex structures due to the microstructures on the device surface. To address this issue, some cleaning equipment uses ultrasonic waves with frequencies higher than 400kHz. When these waves propagate in the liquid, they create a very thin acoustic boundary layer with a large velocity gradient near the surface of the component being cleaned. Impurity particles are detached from the device surface due to the oscillation effect of the liquid, enabling the removal of micron- and submicron-sized impurity particles, achieving an ultra-precision cleaning process. However, acoustic cavitation requires a certain energy input, and the energy conversion and transmission efficiency of existing ultrasonic cleaning equipment is relatively low, resulting in low cleaning efficiency. The simultaneous generation of numerous bubbles can also inhibit cleaning due to their interaction. Insufficient bubble stability can cause bubbles to collapse prematurely under the influence of ultrasonic waves, further reducing the cleaning effect. This invention utilizes a micro-nano bubble generator to produce bubble bundles of controllable size and rate, which easily induces acoustic cavitation, providing another method for the study of ultrasonic cleaning. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a wafer ultrasonic cleaning device and method based on transient and steady-state cavitation of micro-nano bubbles.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A wafer cleaning apparatus based on transient and steady-state cavitation of micro / nano bubbles, the cleaning apparatus comprising: Cleaning tank; A micro-nano bubble generator is provided, comprising a micro-nano bubble generator, a micro-nano bubble generator outlet pipe, and a micro-nano bubble generator liquid inlet pipe. The micro-nano bubble generator is used to generate micro-nano bubbles, and its main body is located below the cleaning tank. The micro-nano bubble generator outlet pipe connects the micro-nano bubble generator and the cleaning tank and is located below the wafer. The micro-nano bubble generator liquid inlet pipe is located at the bottom of the cleaning tank. An ultrasonic transmitter is installed on the side of the cleaning tank to emit ultrasonic waves, which excite the micro- and nano-bubbles between the wafers. The micro- and nano-bubbles generate steady-state cavitation or transient cavitation, which generates micro-jets to clean the wafers. The control system, located below the cleaning tank, receives instructions and controls the entire cleaning process, including the operating status of the ultrasonic transmitter and the micro-nano bubble generator.

[0007] Furthermore, the micro-nano bubble generating device includes a micro-nano bubble liquid inlet device, a micro-nano bubble air inlet device, and a bubble bundle generating device, forming a parallel microchannel and bubble flow mode to generate micro-nano bubbles with controllable size and adjustable quantity. The micro-nano bubbles move to the wafer surface and generate acoustic cavitation.

[0008] Furthermore, the micro-nano bubble liquid inlet device includes multiple liquid inlets, wherein each liquid inlet of the previous stage is connected to two liquid inlets of the next stage, and the micro-nano bubble air inlet device includes multiple air inlets, wherein each air inlet of the previous stage is connected to two air inlets of the next stage.

[0009] Furthermore, the bubble bundle generating device includes a bubble bundle generating liquid inlet one, a bubble bundle generating liquid inlet two, a bubble bundle generating air inlet one, and a bubble bundle. The bubble bundle generating liquid inlet one and the bubble bundle generating liquid inlet two are symmetrically arranged with the bubble bundle generating air inlet one as the axis of symmetry. Both the bubble bundle generating liquid inlet one and the bubble bundle generating liquid inlet two are connected to the last stage liquid inlet of the micro-nano bubble liquid inlet device, and the bubble bundle generating air inlet one is connected to the last stage liquid inlet of the micro-nano bubble air inlet device.

[0010] Furthermore, flexible material membranes are respectively provided on both sides of the bubble bundle generating air inlet and between the bubble bundle generating liquid inlet and the bubble bundle generating liquid inlet, and the flexible material membranes are symmetrically arranged with the bubble bundle generating air inlet as the axis of symmetry.

[0011] Furthermore, it also includes a detection system installed on the other side of the tank-type cleaning tank to detect the temperature, water level, and gas content of the cleaning fluid.

[0012] Furthermore, a first side electrode and a second side electrode are respectively provided on both sides of the cleaning tank, which control the micro-nano bubbles.

[0013] On the other hand, the present invention provides a cleaning method for a wafer cleaning apparatus based on transient and steady-state cavitation of micro-nano bubbles, comprising the following steps: Step 1: Prepare the cleaning environment, check the sealing of the cleaning tank and preheat the cleaning tank to the set temperature; Step 2: Place the wafer into the cleaning tank and secure it, start the control system and perform a self-test; Step 3: Activate and preheat the Wiener bubble generator to generate micro-nano bubbles that enter the cleaning tank for pretreatment of the wafer. The detection system detects whether the gas content and temperature of the cleaning tank meet the standards. If they do not meet the standards, the parameters of the micro-nano bubble generator are adjusted. If they meet the standards, the ultrasonic transmitter is activated. Step 4: Start the ultrasonic generator and adjust the frequency to 20-50 kHz to generate transient cavitation to clean the wafer. The detection system monitors the liquid particle content in real time. If it meets the standard, switch to the 400-700 kHz high-frequency ultrasonic cleaning stage. If it does not meet the standard, continue the low-frequency ultrasonic cleaning stage until the particle content meets the standard. Step 5: After switching to the 400-700 high-frequency ultrasonic cleaning stage, reduce the speed at which the micro-nano bubble generator produces bubbles to generate a steady-state cavitation phenomenon to clean the wafer. Determine if the time exceeds the set time. If so, shut down all cleaning devices, perform a safety check, and record the cleaning data and parameters. Otherwise, continue cleaning using the high-frequency steady-state cavitation phenomenon.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses a designed device, a micro-nano bubble generator, to generate micro-nano bubbles for acoustic cavitation, which changes the traditional ultrasonic cleaning process that relies on steam bubbles generated by ultrasound for acoustic cavitation. 2. The present invention uses a wide outlet channel and a sudden doubling of channel depth after the flow-gathering nozzle to introduce a sudden pressure drop to generate a large number of microbubbles, generating a number of bubbles that can meet the requirements of acoustic cavitation; 3. In the parallel microchannel of the micro-nano bubble generator of the present invention, the gas and liquid inlets combine to generate steady-state controllable micro-nano bubbles. The gas inlet and liquid inlet can be adjusted in the forward direction to increase the flow rate of the gas and liquid, or in the reverse direction to decrease the flow rate of the gas and liquid.

[0015] 4. In this invention, the sound waves can better penetrate the gaps between wafers during propagation, increasing the contact area between the sound waves and the wafers, thereby improving the effect of acoustic cavitation.

[0016] 5. This invention produces a radius of 10-20. Micro- and nano-bubbles of controllable size enable selective transient and steady-state cavitation.

[0017] 6. The device designed in this invention utilizes the powerful impact pressure generated by the collapse of bubbles under transient cavitation. This pressure causes dirt adhering to objects to detach and disperse in the liquid, thus achieving ultrasonic cleaning. Under steady-state cavitation, the micro-shocks generated by bubble vibration can emulsify oily dirt, causing it to detach from the object and enter the cleaning solution, allowing it to fall off on its own and enhancing the cleaning effect.

[0018] 7. Whether the bubble in this invention can vibrate and eventually collapse under the influence of a sound field depends on the sound wave frequency and the resonant frequency of the bubble's motion. Transient cavitation and steady-state cavitation can be selected by adjusting the sound wave frequency.

[0019] 8. The transient cavitation of this invention can generate intense liquid flow and high-intensity shock waves, which is effective for removing dirt or particles adhering to semiconductor surfaces. The collapse of bubbles formed during cavitation generates minute explosive forces and creates localized high-temperature and high-pressure impact zones in the liquid, thereby effectively removing dirt.

[0020] 9. In this invention, during steady-state cavitation, the cavitation bubbles continuously contract and expand without rupturing, creating shear stress in the liquid, which cleans particulate matter and contaminants on the wafer. By adjusting the first and second side electrodes of the cleaning tank, a pulsed electric field can be used to more precisely control the behavior of the bubbles while reducing energy consumption. This promotes the concentration of micro- and nano-bubbles in specific areas of the cleaning tank, enhancing the cleaning effect in those areas.

[0021] 10. Through the design of the device, larger bubbles can provide a stronger acoustic cavitation effect. The more energy they store, the stronger the microjet is generated when the bubble collapses, resulting in higher cleaning capacity. However, this may cause scratches and damage to the surface of the cleaned parts.

[0022] 11. This invention, by adjusting the ultrasonic transmitter, can control the time ratio of transient cavitation and steady-state cavitation generated by ultrasonic waves in a liquid, thereby achieving an effective wafer cleaning process. This method can improve the cleaning effect while reducing cavitation damage to the wafer, thus protecting the wafer's integrity. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a system framework diagram of a wafer cleaning apparatus provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the tank-type ultrasonic cleaning device used in an embodiment of the present invention; Figure 3 This refers to the parallel microchannels used in embodiments of the present invention to generate micro- and nano-bubbles; Figure 4 This refers to the bubble flow production mode used in the embodiments of the present invention; Figure 5 This is a top view schematic diagram of the tank-type ultrasonic cleaning device used in an embodiment of the present invention; Figure 6 This is a schematic diagram of a trough-type ultrasonic cleaning process.

[0025] The components include: 1. Cleaning tank; 2. Ultrasonic transmitting device; 3. Detection system; 4. Micro / nano bubble generator; 41. Micro / nano bubble liquid inlet device; 411. Second-stage liquid inlet 1; 412. Third-stage liquid inlet 1; 413. Third-stage liquid inlet 2; 414. First-stage liquid inlet; 415. Third-stage liquid inlet 3; 416. Third-stage liquid inlet 4; 417. Second-stage liquid inlet 2; 42. Micro / nano bubble air inlet device; 421. Second-stage air inlet 1; 422. First-stage air inlet; 423. Second-stage air inlet 2; 43. Bubble bundle generator; 431. Bubble bundle generating liquid inlet 1; 432. Bubble bundle generating liquid inlet 2; 433. Bubble bundle generating air inlet 1; 434. Bubble bundle; 5. Control system; 6. Wafer; 7. Micro / nano bubble generator outlet pipe; 8. Micro / nano bubble generator inlet pipe. 9. Side electrode one of the cleaning tank; 10. Side electrode two of the cleaning tank. Specific implementation methods The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1 like Figure 1As shown, this invention discloses a wafer cleaning apparatus based on transient and steady-state cavitation of micro-nano bubbles. The apparatus includes a cleaning tank 1, an ultrasonic transmitting device 2, a detection system 3, a micro-nano bubble generating device 5, a wafer 6, an exhaust pipe 7 for the micro-nano bubble generating device, a liquid inlet pipe 8 for the micro-nano bubble generating device, a first side electrode 9 for the cleaning tank, and a second side electrode 10 for the cleaning tank.

[0027] like Figure 2 The schematic diagram of the tank-type ultrasonic cleaning device shows a cleaning tank 1, which provides an environment for ultrasonic cleaning of wafer 6. The wafer 6 is placed inside the cleaning tank, and its complex surface is filled with micro- and nano-bubbles. A micro- and nano-bubble generator 4 is used to generate micro- and nano-bubbles. Its main body is located below the cleaning tank 1. An outlet pipe 7 is located below the wafer 6, and a liquid inlet pipe 8 is located at the bottom of the cleaning tank 1. An ultrasonic transmitter 2 is used to emit ultrasonic waves to excite the micro- and nano-bubbles between the wafers 6, causing steady-state or transient cavitation and generating micro-jets that clean the wafer. This transmitter is located on the side of the cleaning tank 1. A detection system 3 for detecting the temperature, water level, and gas content of the cleaning solution is located on the other side of the cleaning tank 1. In this embodiment, a micro-nano bubble generator 4 is used to generate controllable and stable bubbles for acoustic cavitation. The generated micro-nano bubbles enter the cleaning solution from the bottom of the cleaning tank 1 and are pretreated with the wafer, so that the complex microstructure on the surface of the wafer 6 is filled with micro-nano bubbles. Due to their small size, they can appear in various places on the wafer 6.

[0028] like Figure 3 The parallel microchannels shown generate micro- and nano-bubbles. To achieve a large number of controllable and stable micro- and nano-bubbles, the size of the micro- and nano-bubbles can be adjusted by the flow rate ratio of the gas phase and the continuous phase when using a flow focusing structure. The micro- and nano-bubble generating device 4 includes a micro- and nano-bubble liquid inlet device 41, a micro- and nano-bubble gas inlet device 42, and a bubble bundle generating device 43, forming parallel microchannels and a bubble flow pattern to generate micro- and nano-bubbles with controllable size and adjustable quantity. The micro- and nano-bubbles move to the wafer surface and generate acoustic cavitation.

[0029] The micro / nano bubble liquid inlet device 41 includes multiple liquid inlets, with each stage of liquid inlet connected to two subsequent stages. The air inlet device 42 includes multiple air inlets, with each stage of air inlet connected to two subsequent stages. The bubble bundle generating device 43 includes a bubble bundle generating liquid inlet 431, a bubble bundle generating liquid inlet 432, a bubble bundle generating air inlet 433, and a bubble bundle 434. The bubble bundle generating liquid inlet 431 and the bubble bundle generating liquid inlet 432 are symmetrically arranged about the bubble bundle generating air inlet 433. Both the bubble bundle generating liquid inlet 431 and the bubble bundle generating liquid inlet 432 are connected to the last stage liquid inlet of the micro / nano bubble liquid inlet device 41, and the bubble bundle generating air inlet 433 is connected to the last stage liquid inlet of the air inlet device 42.

[0030] A large number of microbubbles are generated by introducing a sudden pressure drop through a wide outlet channel and a sudden doubling of the channel depth after the flow focusing nozzle. This invention uses micro-nanobubbles to generate acoustic cavitation, overcoming the problem of poor bubble size uniformity in traditional ultrasonic and mechanical stirring. In this embodiment, the micro-nanobubble liquid inlet device 41 includes three-stage liquid inlets: a second-stage liquid inlet 411; a third-stage liquid inlet 412; a third-stage liquid inlet 413; a first-stage liquid inlet 414; a third-stage liquid inlet 415; a third-stage liquid inlet 416; and a second-stage liquid inlet 417. By using the first-stage air inlet, second-stage air inlet, first-stage liquid inlet, second-stage liquid inlet, and third-stage liquid inlet in the parallel microchannel structure, the flow rate and size of the bubbles can be further precisely adjusted. The first-stage air inlet and first-stage liquid inlet have a stable flow rate, while the second-stage air inlet, second-stage liquid inlet, and third-stage liquid inlet can adjust the flow rate according to the number of bubble bundles generated. Each stage of air and liquid inlet exists independently. Under the influence of an electric field, the charged properties of micro- and nano-bubbles allow them to be affected by the electric field force, thus achieving directional alignment of the bubbles. By adjusting the direction and intensity of the electric field, the distribution and arrangement of bubbles on the surface of the object being cleaned can be controlled, allowing them to cover the surface more evenly and improving the uniformity and efficiency of cleaning.

[0031] Figure 4The diagram illustrates the generation mode of micro / nanobubbles. The aforementioned micro / nanobubble generation method includes a bubble bundle generating inlet 431, a bubble bundle generating inlet 432, a bubble bundle generating air inlet 433, and a bubble bundle 434. Using a bubble flow mode, a large number of micro / nanobubbles are generated by introducing a sudden pressure drop through a wide outlet channel and a sudden doubling of the channel depth after the flow focusing nozzle, for acoustic cavitation cleaning. Flexible material membranes are respectively installed on both sides of the bubble bundle generating air inlet 433 between it and the bubble bundle generating inlets 431 and 432. These flexible material membranes are symmetrically arranged about the bubble bundle generating air inlet 433 as an axis of symmetry. The flexible material on both sides of the air inlet 433 allows for adjustment of the opening size by applying force, thus controlling the size of the generated micro / nanobubbles. By controlling the flow rate and size of the generated micro / nanobubbles, the contact time between the bubbles and the surface of the object being cleaned can be extended, increasing the thoroughness and efficiency of the cleaning. The introduction of an electric field can further stabilize the micro / nanobubbles, reducing bubble merging and collapse.

[0032] More specifically, microbubbles and nanobubbles possess a large specific surface area, which can increase the mass transfer rate at the gas-liquid interface and improve mass transfer efficiency. Furthermore, microbubbles and nanobubbles have a long residence time, allowing them to remain active in liquids for extended periods. The generated microbubbles and nanobubbles are more easily activated in an ultrasonic field, resulting in acoustic cavitation and strong physical and chemical effects. The high activity of microbubbles and nanobubbles can generate higher temperatures and pressures, further promoting acoustic cavitation. An electric field can influence ion movement and chemical reaction rates in liquids. During ultrasonic cleaning, the electric field can promote chemical reactions between microbubbles and the surface of the object being cleaned, such as redox reactions, thereby accelerating the decomposition and removal of contaminants and improving cleaning efficiency.

[0033] The ultrasonic transmitter 2 is positioned to allow sound waves to better penetrate the gaps between wafers during propagation, increasing the contact area between the sound waves and the wafers, thereby improving the acoustic cavitation effect. Under a suitable electric field, micro- and nano-bubbles may collapse more rapidly, generating stronger impact forces and releasing more energy. This energy release helps to more thoroughly remove dirt and impurities adhering to the surface of objects, improving cleaning efficiency.

[0034] This invention utilizes an ultrasonic transmitting device 2, installed on the side of the cleaning tank. The emitted sound waves propagate between the wafers 6, facilitating acoustic cavitation. Cavitation bubbles in the liquid vibrate under the influence of the sound field. When the sound pressure or intensity reaches a certain level, the bubbles rapidly expand and then suddenly collapse. During transient cavitation, the collected energy is diffused as shock waves, generating high temperature and pressure around the bubbles. This continuously produces instantaneous micro-jet streams that impact the object's surface. This phenomenon often occurs near the interface between solid and liquid, where contaminants detach from the object's surface under the powerful impact. The micro- and nano-bubbles dispersed in the cleaning liquid are ubiquitous; even the smallest gap between contaminants and objects allows the cavitation-generated micro-jet streams to impact and detach the contaminants.

[0035] Ultrasonic transmitter 2 emits sound waves that act on micro- and nano-bubbles within the complex structure of the wafer, causing transient cavitation and generating high-speed microjets that impact contaminants on wafer 6. Tiny particles on these contaminants are detached and enter the cleaning solution, achieving a cleaning effect. Steady-state cavitation then generates low-speed microflows that impact contaminants on wafer 6. Repeated impacts of these lower-speed microflows not only allow tiny particles to detach directly from wafer 6 but also prevent damage to its surface.

[0036] The ultrasonic transmitter 2 emits low-frequency sound waves that act on micro- and nano-bubbles, causing transient cavitation. As the sound waves propagate in the cleaning fluid, they generate strong pressure changes, leading to the rapid enlargement, growth, and collapse of the micro- and nano-bubbles, forming outward micro-jets. This process, known as transient cavitation, generates high-speed micro-jets that perform the cleaning action. The emitted higher-frequency sound waves act on the micro- and nano-bubbles, causing steady-state cavitation. The surrounding liquid flows outward as the micro- and nano-bubbles expand and inward as they compress, forming lower-level micro-flows that also contribute to the cleaning effect.

[0037] In the parallel microchannels of the micro / nano bubble generator 4, the micro / nano bubble liquid inlet device 41 and the micro / nano bubble air inlet device 42 combine to generate steady-state controllable micro / nano bubbles. The micro / nano bubble liquid inlet device 41 and the micro / nano bubble air inlet device 42 can be adjusted in a positive direction to increase the flow rate of the gas and liquid, or in a negative direction to decrease the flow rate of the gas and liquid. After the generated micro / nano bubbles are pre-treated with the wafer 6 for a period of time, allowing the micro / nano bubbles to fully penetrate the complex structure of the wafer, the frequency and time variation are adjusted by the ultrasonic transmitter 2 to regulate the ratio of transient cavitation to steady-state cavitation time. This improves the cleaning effect while effectively reducing cavitation damage to the wafer.

[0038] like Figure 5 As shown, by adjusting the first electrode 9 and the second electrode 10 on the side of the cleaning tank, the behavior of bubbles can be more precisely controlled using a pulsed electric field, while reducing energy consumption. This promotes the concentration of micro- and nano-bubbles in specific areas of the cleaning tank, enhancing the cleaning effect in those areas.

[0039] Example 2 like Figure 6 As shown, this embodiment provides a wafer cleaning method based on transient and steady-state cavitation of micro / nano bubbles, including the following steps: Step 1: Prepare the cleaning environment, check the sealing of the cleaning tank and preheat the cleaning tank to the set temperature; Step 2: Place the wafer into the cleaning tank and secure it, start the control system and perform a self-test; Step 3: Activate and preheat the Wiener bubble generator to generate micro-nano bubbles that enter the cleaning tank for pretreatment of the wafer. The detection system detects whether the gas content and temperature of the cleaning tank meet the standards. If they do not meet the standards, the parameters of the micro-nano bubble generator are adjusted. If they meet the standards, the ultrasonic transmitter is activated. Step 4: Start the ultrasonic generator and adjust the frequency to 20-50 kHz to generate transient cavitation to clean the wafer. The detection system monitors the liquid particle content in real time. If it meets the standard, switch to the 400-700 kHz high-frequency ultrasonic cleaning stage. If it does not meet the standard, continue the low-frequency ultrasonic cleaning stage until the particle content meets the standard. Step 5: After switching to the 400-700 high-frequency ultrasonic cleaning stage, reduce the speed at which the micro-nano bubble generator produces bubbles to generate a steady-state cavitation phenomenon to clean the wafer. Determine if the time exceeds the set time. If so, shut down all cleaning devices, perform a safety check, and record the cleaning data and parameters. Otherwise, continue cleaning using the high-frequency steady-state cavitation phenomenon.

[0040] Acoustic cavitation resonant frequency f a The relationship between the initial radius R0 and the initial radius is expressed as follows: (1) Wherein, the initial radius of the micro / nano bubble is R0, and P0 is the hydrostatic pressure of the liquid. The surface tension of the bubble, The surface tension coefficient of the liquid. For the density of the liquid, is the specific heat ratio of the gas.

[0041] The above equation expresses the relationship between the resonant frequency and the initial bubble radius of the ultrasonic vapor bubble. It shows that when the driving sound wave frequency is less than the resonant frequency, the bubble will collapse after repeated oscillations; when the driving sound wave frequency is greater than the resonant frequency, the bubble will continue to undergo a series of complex oscillation processes, but will not collapse.

[0042] The expression for the change of bubble radius as a function of time in an incompressible infinitely large liquid micro- or nano-bubble in an ultrasonic field is as follows: (2) Among them, P VThe vapor pressure inside the bubble is P, and the ultrasonic sound pressure is P. A R is the bubble radius that varies with time.

[0043] The above expression for the change of bubble radius with time in an ultrasonic field can be used to study the influence of different initial micro- and nano-bubble radii on the bubble motion process in an ultrasonic field.

[0044] The expression for the rising velocity of micro / nano bubbles is as follows: (3) in It's speed. It is the acceleration due to gravity. The density of the liquid, The density of the gas, Let be the radius of the bubble. The viscosity of the liquid is denoted by ν. The smaller the bubble, the slower its rising speed, resulting in a longer residence time in the liquid phase. This makes it easier for the bubble to enter the complex structure of the wafer, thus improving cleanliness.

[0045] In this embodiment, transient cavitation of bubbles is generated under an ultrasonic field; the collapse of bubbles under transient cavitation will generate a strong impact pressure, which can cause dirt adhering to the object to detach from the object and disperse in the liquid, thereby achieving the effect of ultrasonic cleaning.

[0046] The aforementioned transient cavitation can generate intense liquid flow and high-intensity shock waves, which can be used to remove dirt or particles adhering to semiconductor surfaces. The collapse of bubbles formed during cavitation generates tiny explosive forces and creates localized high-temperature and high-pressure impact zones in the liquid, thereby effectively removing dirt.

[0047] This invention utilizes the acoustic cavitation resonant frequency f a The relationship equation between the initial radius R0 and the transient and steady-state cavitation phenomena are derived from the relationship curve between the initial radius and the resonant frequency of micro-nano bubbles in the ultrasonic field of liquid solution. When the initial bubble radius is constant, transient cavitation occurs when the transmission drive frequency of the ultrasonic transmitter is less than the resonant frequency, and steady-state cavitation occurs when the transmission drive frequency is greater than the resonant frequency.

[0048] In this embodiment, steady-state cavitation is generated under an ultrasonic field. The steady-state cavitation bubbles continuously undergo a series of complex oscillation processes without collapsing. Further, the steady-state cavitation phenomenon is explained: the micro-waves generated by the bubble vibrations under steady-state cavitation can emulsify oily contaminants, causing them to detach from the object in the cleaning solution, allowing them to fall off on their own. This also accelerates the mixing of the object and contaminants, enhancing the cleaning effect.

[0049] Under the above conditions, whether a bubble can vibrate and eventually collapse under the influence of a sound field depends on the sound wave frequency and the resonant frequency of the bubble's motion. Transient cavitation and steady-state cavitation can be selected by adjusting the sound wave frequency.

[0050] The above formulas allow for the investigation of acoustic cavitation at different sound frequencies, as well as the study of acoustic cavitation phenomena caused by different micro / nano bubble radii. Larger bubbles provide a stronger acoustic cavitation effect; the more energy they store, the stronger the microjets generated when they collapse, resulting in higher cleaning capabilities. However, this may lead to scratches and damage to the surface of the cleaned parts. Therefore, cleaning parameters need to be adjusted according to specific requirements.

[0051] By adjusting the ultrasonic transmitter, the time ratio of transient and steady-state cavitation generated by ultrasound in the liquid can be controlled, thereby achieving an effective wafer cleaning process. During the cleaning process, the micro-nano bubble generator operates first, filling the area around the wafer in the cleaning tank with micro-nano bubbles. Then, the ultrasonic transmitter is activated, operating at a low frequency. At this point, transient cavitation from the micro-nano bubbles cleans large particles on the wafer. Once the turbidity in the cleaning solution slowly decreases, the generation rate of the micro-nano bubbles is reduced while the ultrasonic transmitter operates at a high frequency. Steady-state cavitation then occurs in the cleaning tank, cleaning the tiny particles on the wafer. This method can improve cleaning efficiency while reducing cavitation damage to the wafer, thus protecting its integrity.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wafer cleaning device based on transient and steady-state cavitation of micro / nano bubbles, characterized in that, The cleaning device includes: Cleaning tank (1); The micro-nano bubble generator includes a micro-nano bubble generator (4), a micro-nano bubble generator outlet pipe (7), and a micro-nano bubble generator inlet pipe (8). The micro-nano bubble generator (4) is used to generate micro-nano bubbles, and its main body is set below the cleaning tank (1). The micro-nano bubble generator outlet pipe (7) connects the micro-nano bubble generator (4) and the cleaning tank (1), and it is set below the wafer (6). The micro-nano bubble generator inlet pipe (8) is set at the bottom of the cleaning tank (1). An ultrasonic transmitting device (2) is set on the side of the cleaning tank (1) to emit ultrasonic waves to excite the micro-nano bubbles between the wafers (6). The micro-nano bubbles generate steady-state cavitation or transient cavitation, and generate micro-jets to clean the wafers. The detection system (3) is installed on the other side of the tank cleaning tank (1) and is used to detect the temperature, water level and gas content of the cleaning fluid; The control system (5), which is located below the cleaning tank (1), receives instructions and controls the entire cleaning process, including the working status of the ultrasonic transmitter (2) and the micro-nano bubble generator (4); the device is configured to: start the ultrasonic generator, adjust the frequency to 20-50 kHz to generate transient cavitation to clean the wafer, and the detection system detects the liquid particle content in real time. If the standard is met, it switches to the 400-700 kHz high-frequency ultrasonic cleaning stage and reduces the speed at which the micro-nano bubble generator generates bubbles in order to generate steady-state cavitation to clean the wafer.

2. The wafer cleaning apparatus based on transient and steady-state cavitation of micro / nano bubbles as described in claim 1, characterized in that: The micro-nano bubble generating device (4) includes a micro-nano bubble liquid inlet device (41), a micro-nano bubble air inlet device (42), and a bubble bundle generating device (43), forming a parallel microchannel and bubble flow mode to generate micro-nano bubbles with controllable size and adjustable quantity. The micro-nano bubbles move to the wafer surface and generate acoustic cavitation.

3. The wafer cleaning apparatus based on transient and steady-state cavitation of micro / nano bubbles as described in claim 2, characterized in that: The micro-nano bubble liquid inlet device (41) includes multiple liquid inlets, wherein each liquid inlet is connected to two lower liquid inlets. The micro-nano bubble air inlet device (42) includes multiple air inlets, wherein each air inlet is connected to two lower air inlets.

4. The wafer cleaning apparatus based on transient and steady-state cavitation of micro / nano bubbles as described in claim 3, characterized in that: The bubble bundle generating device (43) includes a bubble bundle generating liquid inlet one (431), a bubble bundle generating liquid inlet two (432), a bubble bundle generating air inlet one (433), and a bubble bundle (434). The bubble bundle generating liquid inlet one (431) and the bubble bundle generating liquid inlet two (432) are symmetrically arranged with the bubble bundle generating air inlet one (433) as the axis of symmetry. The bubble bundle generating liquid inlet one (431) and the bubble bundle generating liquid inlet two (432) are both connected to the last stage liquid inlet of the micro-nano bubble liquid inlet device (41). The bubble bundle generating air inlet one (433) is connected to the last stage liquid inlet of the micro-nano bubble air inlet device (42).

5. The wafer cleaning apparatus based on transient and steady-state cavitation of micro / nano bubbles as described in claim 4, characterized in that: Flexible material membranes are respectively provided on both sides of the bubble bundle generating air inlet (433) and between the bubble bundle generating liquid inlet (431) and the bubble bundle generating liquid inlet (432). The flexible material membranes are symmetrically arranged with the bubble bundle generating air inlet (433) as the axis of symmetry.

6. The wafer cleaning apparatus based on transient and steady-state cavitation of micro / nano bubbles as described in claim 1, characterized in that: The cleaning tank (1) is provided with a cleaning tank side electrode one (9) and a cleaning tank side electrode two (10) on both sides, and the cleaning tank side electrode one (9) and the cleaning tank side electrode two (10) control the micro-nano bubbles.

7. The cleaning method of the wafer cleaning apparatus based on transient and steady-state cavitation of micro / nano bubbles as described in any one of claims 5 or 6, characterized in that: Includes the following steps: Step 1: Prepare the cleaning environment, check the sealing of the cleaning tank and preheat the cleaning tank to the set temperature; Step 2: Place the wafer into the cleaning tank and secure it, start the control system and perform a self-test; Step 3: Activate and preheat the Wiener bubble generator to generate micro-nano bubbles that enter the cleaning tank for pretreatment of the wafer. The detection system detects whether the gas content and temperature of the cleaning tank meet the standards. If they do not meet the standards, the parameters of the micro-nano bubble generator are adjusted. If they meet the standards, the ultrasonic transmitter is activated. Step 4: Start the ultrasonic generator and adjust the frequency to 20-50 kHz to generate transient cavitation to clean the wafer. The detection system monitors the liquid particle content in real time. If it meets the standard, switch to the 400-700 kHz high-frequency ultrasonic cleaning stage. If it does not meet the standard, continue the low-frequency ultrasonic cleaning stage until the particle content meets the standard. Step 5: After switching to the 400-700 kHz high-frequency ultrasonic cleaning stage, reduce the speed at which the micro-nano bubble generator produces bubbles to generate a steady-state cavitation phenomenon to clean the wafer. Determine if the time exceeds the set time. If so, shut down all cleaning devices, perform a safety check, and record the cleaning data and parameters. Otherwise, continue cleaning using the high-frequency steady-state cavitation phenomenon.

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