Brushing device based on wafer thickness dynamic adjustment and control method thereof

Abstract

The invention relates to the technical field of semiconductors, discloses a scrubbing device based on wafer thickness dynamic adjustment and a control method of the scrubbing device, and aims to solve the technical problems that an existing single-chip wafer scrubbing device is prone to being scratched and abraded or low in cleaning efficiency and residual in particles when processing wafers with different thicknesses due to the fact that the relative height of a brush is fixed. The brushing device and the control method are characterized in that the brushing device comprises a supporting arm, a brushing disc assembly, a vertical movement mechanism, a rotary driving mechanism, a pressure sensing module and an integrated control system. The integrated control system receives pressure sensing feedback, precisely regulates and controls the vertical movement mechanism through PID closed-loop control, and achieves dynamic control over the contact pressure between the brush disc and the wafer. By means of the scheme, the risk of scratching can be eradicated, cleaning uniformity and thoroughness are guaranteed, the service life of the bristles is prolonged, and the yield and reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, and more specifically, relates to a brushing device and its control method based on dynamic adjustment of wafer thickness. Background Technology

[0002] In the complex processes of integrated circuit manufacturing, wafer cleaning technology plays a crucial role, as its cleanliness directly determines the performance, reliability, and even overall production yield of the final device. As semiconductor technology continues to advance towards the sub-nanometer scale and the large-scale application of advanced three-dimensional structures such as FinFET and 3D NAND becomes more prevalent, the standards for controlling various contaminants on the wafer surface, including microscopic particles, metal ions, and organic residues, are becoming increasingly stringent. Micro- and nano-level contamination, even at extremely low concentrations, can have catastrophic effects on device function, making efficient, uniform, and non-destructive wafer cleaning a key bottleneck restricting the development of cutting-edge processes.

[0003] For a considerable period, traditional batch cleaning equipment, such as tank cleaners, dominated semiconductor manufacturing due to their relatively high throughput and low unit cost. These machines typically achieve batch cleaning by simultaneously immersing multiple wafers in a chemical solution, combined with ultrasonic or megasonic wave assistance. Their design philosophy was to improve cleaning efficiency through economies of scale, effectively solving the problem of removing major contaminants from wafer surfaces within the technological context of the time. However, with the continuous shrinking of integrated circuit feature sizes and the dramatic increase in the demand for process control precision, the inherent limitations of batch cleaning solutions have gradually become apparent. Specifically, immersion cleaning struggles to ensure uniform chemical exchange and cleaning action at different locations on each wafer, resulting in insufficient cleaning uniformity. Simultaneously, sharing the cleaning solution among multiple wafers increases the risk of cross-contamination; contaminants detached from previous batches may re-adsorb onto the surfaces of subsequent wafers, which is unacceptable for advanced processes that pursue ultimate cleanliness. Furthermore, large-capacity cleaning tanks also imply significant chemical consumption, which is inconsistent with current trends in green manufacturing.

[0004] Against this backdrop, single-wafer cleaning machines have emerged and quickly become the mainstream cleaning solution for advanced semiconductor manufacturing. Single-wafer cleaning machines, through modular design, typically consist of multiple independent cleaning chambers. Precision robotic arms sequentially feed each wafer into different chambers for individual processing, such as spray cleaning or brushing. Compared to batch cleaning, single-wafer cleaning machines significantly improve the uniformity and controllability of cleaning, effectively avoiding cross-contamination and batch-to-batch contamination issues. They are particularly well-suited to meet the stringent requirements of single-wafer process control at 18nm and below nodes, achieving precise control over wafer surface particles, metal residues, and organic contaminants. A typical single-wafer cleaning process often includes a brush chamber and a spin-pin (SPIN) chamber: the wafer first undergoes mechanical contact in the brush chamber to remove larger particles and stubborn contaminants from its surface, and then enters the spin-pin chamber for chemical spraying and rinsing to remove chemical residues.

[0005] However, with the continuous development of related technologies and the increasingly stringent performance requirements of application scenarios, some inherent characteristics of the aforementioned technical solutions at the principle level have gradually revealed their limitations in addressing new challenges, especially the traditional brushing mechanism used in the brush chamber. Existing single-wafer cleaning machines typically use a relatively fixed-height PVA (polyvinyl alcohol) sponge brush to clean the wafer surface. This design, when processing wafers of standard thickness, effectively removes adhering particles by physically wiping the wafer surface thanks to the softness and absorbency of PVA material. The underlying reason is that this "fixed-height" design mode is fundamentally flawed because it struggles to adapt to the diversity and minute differences in wafer thickness in modern semiconductor manufacturing. In actual production lines, not only may wafers of different models or batches exhibit differences in nominal thickness, but even wafers from the same batch may show thickness deviations at the micrometer or even submicrometer level after undergoing front-end processes such as grinding, polishing, and epitaxial growth. Under these dynamically changing conditions, if the relative height of the brush remains constant, a series of chain reactions will inevitably occur: When the actual wafer thickness is greater than expected or the brush pressure is set too high, the fixed brush height will cause excessive contact pressure between the brush and the wafer surface. This will not only accelerate the wear of the PVA sponge bristles and shorten their service life, but more seriously, the excessive local pressure will cause the tiny particles adsorbed by the bristles themselves (existing PVA soft brushes generally have the risk of particle adsorption) to cause irreversible scratches or pitting on the wafer surface during the brushing process, acting like an abrasive. Especially for advanced process wafers containing precise three-dimensional structures, any surface damage may lead to device failure. Conversely, if the actual wafer thickness is less than expected, or the brush pressure is set insufficiently, the fixed-height brush may not be able to form effective and uniform contact with the wafer surface, resulting in insufficient cleaning force, greatly reduced cleaning efficiency, and failure to fully remove all attached particles, thus leaving potential contamination hazards. This rigid, non-adaptive brushing mechanism exposes the inherent limitations of existing technologies in terms of refined control when facing the combined demands of high precision, diversity, and high yield in semiconductor manufacturing. This fundamental mismatch has become a key bottleneck restricting the performance of single-wafer brush chambers in advanced processes.

[0006] Therefore, how to develop a new type of brushing device and its control method that can dynamically adapt the brush height according to wafers of different thicknesses and achieve precise pressure control, so as to overcome the problems of scratch risk and uneven cleaning efficiency caused by existing fixed-height brushes during the cleaning process, has become a key challenge and a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0007] To address the technical challenges of existing single-wafer wafer cleaning devices that suffer from excessive contact pressure leading to wafer scratches or brush wear due to the fixed relative height of the brushes when processing wafers of varying thicknesses, and insufficient contact pressure resulting in low cleaning efficiency and particle residue, this invention provides a cleaning device and its control method based on dynamic adjustment of wafer thickness. By integrating high-precision displacement control, real-time contact pressure sensing, and an intelligent closed-loop feedback mechanism, it aims to achieve precise and dynamic control of the contact pressure between the brush and the wafer surface, thereby effectively eliminating the risk of scratches, ensuring uniform and thorough cleaning, and optimizing brush bristle lifespan.

[0008] The wafer cleaning device disclosed in this invention includes a support arm, a brush assembly, a vertical motion mechanism, a rotary drive mechanism, a pressure sensing module, and an integrated control system. The support arm is designed as a high-rigidity structure to support and transmit vertical and rotary motion to the brush assembly. The support arm integrates power supply, signal transmission, and fluid delivery channels to achieve energy supply, data exchange, and precise delivery of cleaning fluid to the brush assembly.

[0009] The vertical motion mechanism includes a coarse-adjustment vertical motion unit and a fine-adjustment vertical motion unit. The coarse-adjustment vertical motion unit enables rapid, wide-range vertical lifting and lowering of the support arm and its supported brush assembly. For example, it can employ a pneumatic linear actuator, which drives a piston rod to move linearly along a preset guide rail using high-pressure gas, and is equipped with a travel limit switch or linear encoder to provide coarse position feedback. The fine-adjustment vertical motion unit works in series or parallel with the coarse-adjustment unit to achieve micron-level precise vertical displacement adjustment of the support arm and its supported brush assembly. Specifically, the fine-adjustment vertical motion unit can consist of a precision servo motor, a high-precision ball screw transmission mechanism, and a high-resolution linear encoder. The precision servo motor drives the ball screw to rotate through closed-loop control, thereby driving the support arm connected to the screw nut to perform precise vertical movement. The linear encoder provides real-time, sub-micron-level vertical position feedback, ensuring position control accuracy of ±0.5 microns. The vertical motion mechanism is integrally mounted on the frame structure of the cleaning machine, and the stability and sway-free operation of the support arm during vertical movement are ensured by precision guide rails (e.g., linear rolling guide rail pairs).

[0010] The rotary drive mechanism is connected to the support arm and is used to drive the brush assembly to rotate. The rotary drive mechanism includes a brushless DC servo motor, which is directly or via a low-backlash synchronous belt drive to the central shaft of the brush assembly. The brushless DC servo motor is equipped with a high-resolution incremental rotary encoder to provide real-time, precise speed and angle feedback, thereby achieving stepless precise control of the brush rotation speed within the range of 50 rpm to 1500 rpm, with a speed fluctuation range of less than ±1%. The rotary drive mechanism is designed to ensure smooth brush rotation at different speeds, without significant vibration or axial runout, to avoid introducing additional mechanical stress.

[0011] The brush assembly is mounted on the lower end of the support arm and directly connected to the output shaft of the rotary drive mechanism for brushing contact with the wafer surface. Specifically, the brush assembly includes a brush holder, a brush, and a pressure sensing module. The brush holder is made of high-strength, chemically resistant engineering plastic (e.g., polyetheretherketone (PEEK) or polytetrafluoroethylene (PTFE)), featuring a lightweight and high-rigidity design, and integrates a quick-installation and removal mechanism for the brush. The brush is made of polyvinyl alcohol (PVA) sponge material with a porosity ranging from 80% to 95%, an average pore size of 50 to 200 micrometers, and a Shore hardness ranging from Type A 20 to 40. The brush has an outer diameter ranging from 50 to 150 millimeters and a thickness ranging from 10 to 30 millimeters, and is formed using a special pressing process to create a porous, soft structure with good water absorption to reduce the risk of particle adsorption. The brush is replaceably fixed to the brush holder via snap-fit ​​or threaded connections, ensuring a secure connection between the brush and the holder.

[0012] The pressure sensing module is integrated inside the brush holder or on the connecting axis between the brush assembly and the support arm. Its core component is a high-resolution miniature piezoelectric force sensor or a strain gauge miniature load cell. The sensor directly or through a miniature force transmission rod contacts the base of the brush to accurately measure the contact pressure between the brush and the wafer surface in real time. The pressure sensing module has a measurement range of 0.1 Newtons to 10 Newtons, a resolution of up to 0.01 Newtons, and a refresh rate of no less than 1000 Hz, ensuring a rapid and sensitive response to pressure during brushing. The pressure sensing module communicates with the integrated control system via an RS485 digital cable through a shielded cable, ensuring interference resistance and reliability of data transmission. The sensor undergoes precise calibration before installation to eliminate temperature drift and creep effects, ensuring consistent measurement accuracy throughout the entire working cycle.

[0013] The integrated control system is the core component of this invention. It receives feedback signals from the pressure sensing module and precisely regulates the vertical motion mechanism according to a preset control strategy, thereby achieving closed-loop control of the contact pressure between the brush and the wafer. The integrated control system includes a main controller, a motion controller, a data acquisition module, and a cleaning recipe database.

[0014] The main controller is an industrial-grade programmable logic controller (PLC) or industrial computer (IPC), responsible for the process management, status monitoring, safety interlocking, and communication with the main control system of the cleaning machine for the entire brushing device. The motion controller is a multi-axis servo motion controller that communicates with the main controller at high speed via industrial Ethernet (e.g., EtherCAT or Profinet). The motion controller is responsible for receiving motion commands (including target contact pressure, brushing path, rotation speed, etc.) from the main controller and precisely controlling the servo motors of the vertical motion mechanism and the rotary drive mechanism based on real-time position / speed feedback from the linear encoder and rotary encoder.

[0015] The data acquisition module is connected to the pressure sensing module and is responsible for real-time acquisition and preprocessing of the digital output signal of the pressure sensor, including signal filtering, noise suppression and unit conversion, and transmitting the processed accurate pressure value to the motion controller at a high frame rate.

[0016] The cleaning recipe database stores brushing parameter sets corresponding to different wafer types (e.g., silicon wafers, compound semiconductor wafers), wafer thicknesses, process stages, and contaminant types. Each parameter set includes: target contact pressure (set to an accuracy of 0.05 Newtons), brush rotation speed, brushing path mode (e.g., spiral brushing, radial reciprocating brushing), cleaning fluid flow rate, brushing time, and brush life threshold. Before brushing begins, the main controller automatically retrieves the matching brushing parameter set from the cleaning recipe database based on the received wafer ID or process batch information.

[0017] The control method for the washing device is based on an advanced PID (Proportional-Integral-Derivative) closed-loop control algorithm. The specific implementation steps are as follows:

[0018] 1. Wafer Positioning and Pre-wetting: First, the wafer is gripped by a precision robotic arm and securely placed on the wafer support platform of the cleaning machine. Then, deionized water or pre-cleaning solution is sprayed onto the wafer surface through a spray system to pre-wet the wafer surface, reducing surface tension and preparing it for subsequent brushing.

[0019] 2. Coarse Brush Descending: The coarse vertical motion unit (e.g., a pneumatic linear actuator) of the vertical motion mechanism is activated, causing the support arm carrying the brush assembly to rapidly descend to a preset coarse height from the wafer surface. This height is pre-calibrated or provided by a cleaning recipe database, ensuring sufficient clearance between the brush and the wafer surface to avoid collision. The goal of this stage is to shorten the fine adjustment stroke and improve overall work efficiency.

[0020] 3. Precise Brush Proximity and Initial Contact Detection: The motion controller activates the precision servo motor of the finely tuned vertical motion unit, driving the brush assembly to move continuously downwards at extremely low speeds (e.g., 100 micrometers / second to 500 micrometers / second). During this descent, the pressure sensing module continuously monitors the real-time contact pressure between the brush and the wafer. Once the pressure sensor detects initial contact between the brush and the wafer surface (i.e., the contact pressure value reaches a preset small threshold, e.g., 0.05 Newtons to 0.1 Newtons, which is used to distinguish mechanical contact from environmental noise), the motion controller immediately records the vertical position of this point as the "zero-contact position".

[0021] 4. Contact pressure closed-loop control: After detecting initial contact, the motion controller retrieves the target contact pressure setpoint (P) of the current wafer from the cleaning recipe database. set ), and real-time contact pressure feedback values ​​(P) from the pressure sensing module. feedback The precise vertical displacement adjustment is calculated using the PID closed-loop control algorithm.

[0022] Proportional term (P): Based on the current pressure error (P) error = P set - P feedback The displacement is adjusted proportionally; the larger the error, the larger the adjustment. This provides a rapid response capability.

[0023] Integral term (I): Accumulates historical pressure errors, eliminates steady-state errors, and ensures that the final contact pressure accurately reaches the set value. This term corrects for small, persistent errors.

[0024] Differential term (D): Predicts future pressure change trends, suppresses overshoot and oscillations, and improves system stability. This term is sensitive to the rate of pressure change and provides a damping effect.

[0025] The motion controller sends the calculated vertical displacement adjustment amount to the servo motor driver of the fine-tuning vertical motion unit, driving the servo motor to drive the ball screw to perform micron-level fine adjustments until P... feedback Exact match P set The error remains within ±0.02 Newtons. The entire adjustment process is real-time and dynamic, with a response time of less than 50 milliseconds.

[0026] 5. Brush Rotation and Brushing Execution: While the contact pressure stabilizes at the target set value, the brushless DC servo motor of the rotary drive mechanism is activated, driving the brush assembly to rotate at a precise speed set in the cleaning formula database. Simultaneously, the cleaning fluid supply system, based on the formula parameters, delivers a precise flow rate of cleaning fluid (e.g., deionized water, diluted ammonia, or ozone water) to the contact area between the brush and the wafer through fluid channels inside the support arm. During the brushing process, the integrated control system continuously monitors and dynamically adjusts the vertical displacement to compensate for contact pressure fluctuations caused by factors such as brush wear, changes in liquid viscosity, or localized unevenness of the wafer, ensuring that the contact pressure remains constant and uniform throughout the entire brushing cycle.

[0027] 6. Optimized Brush Path and Composite Motion: To further improve cleaning uniformity, the motion controller can coordinate and fine-tune the vertical motion unit and the rotary drive mechanism according to instructions from the cleaning formula database to achieve composite motion of the brush disk. For example, while maintaining constant contact pressure, the brush disk can perform micro-reciprocating oscillations radially (oscillation amplitude can reach 2 mm to 5 mm, frequency can reach 2 Hz to 5 Hz), or move slowly along a specific spiral path to ensure that the brush can cover every area of ​​the wafer surface, especially the edge and center areas, thereby significantly improving cleaning uniformity. The realization of this composite motion relies on the high-precision synchronous control capability of the servo motor.

[0028] 7. Brush Lifting and Wafer Transfer: After the brushing cycle is complete, the integrated control system first instructs the fine-tuning vertical motion unit to lift the brush assembly at a controlled speed (e.g., 500 μm / s to 1000 μm / s) until the pressure sensor detects that the contact pressure has dropped to zero, indicating that the brush has completely detached from the wafer surface. Subsequently, the coarse-tuning vertical motion unit can further lift the brush assembly to a safe height. The brushed wafer is then picked up by a robotic arm and transferred to the next cleaning station (e.g., a spray chamber for rinsing and drying).

[0029] Compared with the prior art, the wafer brushing device and its control method provided by this invention have the following significant technical advancements and beneficial effects:

[0030] First, by introducing a real-time contact pressure sensing module and a high-precision vertical motion mechanism, combined with a PID closed-loop control algorithm, this invention achieves precise, dynamic, and closed-loop control of the contact pressure between the brush and the wafer surface. This completely solves the inherent defect of traditional fixed-height brushes that cannot adapt to minute differences in wafer thickness. Regardless of changes in wafer thickness, the system can automatically adjust the brush height to maintain the contact pressure within the set optimal range. This adaptive capability fundamentally eliminates wafer scratches and premature brush wear caused by excessive pressure, as well as incomplete cleaning caused by insufficient pressure, significantly improving cleaning yield and reliability.

[0031] Secondly, the precision servo motor and ball screw transmission mechanism employed in the fine-tuned vertical motion unit, combined with a high-resolution linear encoder, provide micron-level or even sub-micron-level precise displacement adjustment capabilities, ensuring the brush disk position accuracy under pressure closed-loop control. This allows the brush bristles to establish and disengage from the wafer surface in an extremely smooth and controlled manner, further reducing the risk of impact damage. Simultaneously, this high-precision displacement control also provides the hardware foundation for future development of more complex brushing trajectories and micro-area brushing strategies.

[0032] Furthermore, the integrated control system designed in this invention, especially its built-in cleaning formula database, enables the device to intelligently select and execute customized brushing parameter sets based on different wafer types, sizes, surface structures, and cleaning requirements. This formula-based intelligent management not only improves production flexibility and efficiency but also ensures optimal adaptability to different process requirements. The introduction of the PID control algorithm allows the system to respond quickly and stabilize at the target pressure point. Even when encountering local protrusions or depressions during brushing, it can maintain a constant contact force by instantly adjusting the bristle height, thereby ensuring the uniformity of cleaning.

[0033] Furthermore, this invention effectively reduces the risk of brush particles falling off by optimizing the brush material, porosity, and shape in the brush assembly and combining this with precise pressure control. By avoiding excessive mechanical stress, the lifespan of the brush is extended, reducing replacement frequency, thereby lowering operating costs and increasing equipment uptime.

[0034] Furthermore, this invention supports precise speed control of the brush disk and multi-dimensional composite motion modes, including radial oscillation or spiral path brushing. This combination of multiple motion modes allows the brush to cover the wafer surface more comprehensively and evenly, which is particularly crucial for cleaning wafers with complex three-dimensional structures (such as FinFET and 3D NAND). It can effectively remove contaminants inside recesses or high aspect ratio structures, achieving a level of cleanliness that is difficult to achieve with traditional brushing.

[0035] The beneficial effects of this invention are:

[0036] This invention achieves a significant breakthrough in contact pressure control for monolithic wafer cleaning devices through a combination of systematic structural innovation and intelligent control methods. It provides a forward-looking, high-performance solution for the increasingly stringent cleaning requirements in the semiconductor manufacturing industry, and has profound implications for improving production yield and device performance in advanced processes. This invention not only improves cleaning quality and efficiency but also optimizes consumable lifespan and reduces operating costs, aligning with the current development trend of green manufacturing and high-efficiency production in the semiconductor industry. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a wafer brushing device according to the present invention;

[0038] Figure 2 This is a schematic diagram of the brush assembly.

[0039] Figure 3 This is a schematic diagram of the vertical motion mechanism of the present invention;

[0040] Figure 4 This is a block diagram of the integrated control system of the present invention;

[0041] Figure 5 This is a flowchart of the control method of the present invention.

[0042] The attached figures are labeled as follows:

[0043] 100. Wafer brushing device; 101. Cleaning machine frame; 102. Wafer support platform; 103. Wafer; 104. Spray system; 105. Cleaning fluid supply system; 200. Support arm; 300. Brush assembly; 310. Brush holder; 320. Brush; 400. Vertical motion mechanism; 410. Coarse adjustment vertical motion unit; 420. Fine adjustment vertical motion unit; 421. Precision servo motor; 422. High-precision ball screw transmission mechanism; 423. High-resolution linear encoder; 500. Rotary drive mechanism; 510. Brushless DC servo motor; 520. High-resolution incremental rotary encoder; 600. Pressure sensing module; 610. Sensor; 700. Integrated control system; 710. Main controller; 720. Motion controller; 730. Data acquisition module; 740. Cleaning formula database. Detailed Implementation

[0044] like Figure 1-5As shown, this invention discloses a brushing device and its control method based on dynamic adjustment of wafer thickness. The aim is to significantly improve the uniformity and thoroughness of wafer cleaning and effectively extend the service life of the brushes by precisely controlling the contact pressure between the brush and the wafer surface, while simultaneously preventing damage to the wafer surface caused by improper mechanical contact pressure. The technical solution provided by this invention will be described in detail below with reference to the accompanying drawings to ensure that those skilled in the art can fully understand and implement the various technical features of this invention.

[0045] In a specific embodiment, such as Figure 1 As shown, the wafer brushing device 100 disclosed in this invention is integrated inside the cleaning machine frame 101. Its core function is to perform fine brushing on the wafers 103 placed on the wafer support stage 102. The entire brushing process is supplemented by a spray system 104 to provide pre-wetting and rinsing functions, and a cleaning fluid supply system 105 to accurately deliver the cleaning fluid to the brushing area.

[0046] In a preferred embodiment of the present invention, the support arm 200, as the structural backbone of the brushing device 100, is designed with high rigidity and lightweight considerations. It is typically made of high-strength aluminum alloy or stainless steel and precision-machined to ensure extremely low deformation under the dynamic load of the brush assembly 300 and during vertical movement. The support arm 200 has multiple integrally formed reinforcing ribs to enhance structural rigidity and a platform providing mounting surfaces for internal electronic modules. Crucially, it integrates multiple independent channels, including power cable channels for transmitting electricity, signal transmission channels for carrying control signals and sensor data, and fluid delivery channels for conveying high-purity cleaning fluid and deionized water. These channels are encapsulated with high-cleanliness materials to avoid introducing particulate or chemical contamination into the semiconductor cleaning environment. The fluid channels typically use smooth-walled, corrosion-resistant polytetrafluoroethylene (PTFE) or perfluoroethylene propylene (FEP) tubing and can be equipped with miniature flow sensors to achieve real-time monitoring and feedback control of the cleaning fluid flow, ensuring precise supply of the cleaning medium.

[0047] Furthermore, the vertical motion mechanism 400 is the core execution unit for dynamically adjusting the contact pressure between the brush and the wafer, and it is mounted on the precision guide rail of the cleaning machine frame 101. This mechanism employs high-precision linear rolling guide pairs, such as preload-adjustable ball linear guides or crossed roller linear guides, to ensure extremely high straightness and extremely low frictional resistance when the support arm 200 moves vertically. The vertical runout is strictly controlled within ±1 micrometer, thus avoiding any form of lateral sway or jitter during vertical movement and ensuring the parallelism between the brush and the wafer surface. Specifically, the vertical motion mechanism 400 includes a coarse-adjustment vertical motion unit 410 and a fine-adjustment vertical motion unit 420, which work together to achieve seamless transitions between rapid, wide-range movement and micrometer-level precise adjustment of the brush assembly 300.

[0048] Specifically, the coarse vertical motion unit 410 is used to achieve rapid, wide-range vertical lifting and lowering of the support arm 200 and the brush assembly 300 it carries. In one embodiment, it can employ a pneumatic linear actuator, which consists of a high-precision, low-friction cylinder. By precisely controlling the pressure and flow rate of the supplied gas, it drives the piston rod to move stably along a preset linear guide. To achieve coarse position feedback and stroke limitation, the pneumatic actuator is typically equipped with a magnetostrictive linear encoder or photoelectric encoder, providing a coarse position accuracy of approximately ±0.1 mm, and is equipped with inductive or mechanical stroke limit switches to ensure the safety and reliability of the movement range. This unit is mainly used for rapid positioning of the brush assembly 300 during wafer loading / unloading or large-scale cleaning area switching. Its maximum stroke can reach 200 mm to 300 mm, and its maximum operating speed can reach 200 mm / s to 500 mm / s.

[0049] The fine-tuning vertical motion unit 420 works in series or parallel with the coarse-tuning vertical motion unit 410. Its function is to achieve micron-level precise vertical displacement adjustment of the brush assembly 300, which is key to achieving precise contact pressure control. Specifically, the fine-tuning vertical motion unit 420 consists of a precision servo motor 421, a high-precision ball screw transmission mechanism 422, and a high-resolution linear encoder 423. The precision servo motor 421 is typically an AC synchronous servo motor with fast response and high positioning accuracy, with a rated power usually between 50 watts and 200 watts to provide sufficient torque to drive the ball screw. This motor receives pulse commands from the motion controller 720 through closed-loop control, driving the high-precision ball screw transmission mechanism 422 to rotate. The ball screw transmission mechanism 422 uses a ground or refinished ball screw with a lead accuracy of ISO 3 or higher. Preload between the nut and the screw eliminates backlash, ensuring transmission rigidity and positioning accuracy. The lead screw nut is securely connected to the support arm 200 via a high-rigidity connector, precisely converting rotary motion into vertical linear motion. A high-resolution linear encoder 423, such as an optical or magnetic scale, is directly mounted on the vertical movement path of the support arm 200, providing real-time, sub-micron-level vertical position feedback with a resolution of 0.1 to 0.5 microns, ensuring that the position control accuracy of the entire fine-tuning vertical motion mechanism 420 can reach ±0.5 microns or even higher. The stroke of this unit is typically in the range of 10 to 50 millimeters, with a minimum step size controllable to below 1 micron and a maximum adjustment speed of 5 to 10 millimeters per second to meet the response requirements of dynamic pressure regulation.

[0050] A rotary drive mechanism 500 is connected to the lower end of the support arm 200 and is used to drive the brush assembly 300 to rotate. The rotary drive mechanism 500 includes a high-performance brushless DC servo motor 510, which is widely used in precision rotary control applications due to its high efficiency, high speed stability, long lifespan, and lack of brush wear. This motor is typically connected directly to the central shaft of the brush assembly 300 via a precision coupling or a low-backlash synchronous belt drive. Direct drive minimizes transmission errors and vibrations, while synchronous belt drive provides flexible transmission within specific space constraints and effectively attenuates the motor's own high-frequency vibrations. The brushless DC servo motor 510 is equipped with a high-resolution incremental rotary encoder 520, typically with a resolution of 2500 lines / revolution to 10000 lines / revolution or even higher, to provide real-time, precise speed and angle feedback, thereby achieving stepless precise control of the brush rotation speed within the range of 50 rpm to 1500 rpm. To ensure uniformity during the cleaning process, the rotation speed fluctuation range is strictly controlled to less than ±1%, and even as low as ±0.5%. The design of the rotary drive mechanism 500 pays special attention to dynamic balance. All rotating parts are precisely dynamic balanced before assembly to ensure that the brush rotates smoothly at different speeds, without significant axial runout or radial vibration, thereby avoiding the introduction of additional mechanical stress or uneven cleaning onto the wafer surface.

[0051] The brush assembly 300 is the core component that directly contacts the wafer surface for cleaning, and its structural design is crucial to the cleaning effect and brush life. The brush assembly 300 is mounted at the lower end of the support arm 200 and precisely connected to the output shaft of the rotary drive mechanism 500 via a high-precision interface. Specifically, the brush assembly 300 includes a brush holder 310, a brush 320, and a pressure sensing module 600. The brush holder 310 is made of high-strength and chemically resistant engineering plastics, commonly including polyetheretherketone (PEEK) or polytetrafluoroethylene (PTFE). These materials possess excellent acid and alkali corrosion resistance, high temperature resistance, and mechanical strength, while also exhibiting low moisture absorption and low exudation characteristics, meeting the requirements of semiconductor cleanroom environments. The brush holder 310 employs a lightweight hollow structure to reduce moment of inertia and improve system response speed, while internal reinforcing ribs ensure high rigidity. Its surface is typically polished or treated with a special coating to further reduce particle adsorption. The brush holder 310 also integrates a quick-installation and removal mechanism for the brush 320. For example, it adopts a snap-on or screw-in design with a self-locking function, which allows operators to quickly and accurately replace the brush 320 without tools or with only simple tools, ensuring a stable connection between the brush and the holder and preventing loosening or eccentricity under high-speed rotation and dynamic contact pressure.

[0052] The brush 320 is the part that directly contacts the wafer surface for physical scrubbing, and its material and structural characteristics directly affect cleaning efficiency and the risk of wafer damage. The brush 320 is made of high-purity polyvinyl alcohol (PVA) sponge material, which has excellent hydrophilicity, elastic recovery, and an extremely low particle shedding rate. The porosity of the brush 320 is strictly controlled between 80% and 95%, with an average pore size of 50 micrometers to 200 micrometers. This ensures that the brush can form a soft, porous structure after absorbing water, effectively capturing and removing tiny particles from the wafer surface while reducing wear on the wafer surface. The Shore A hardness of the brush 320 ranges from 20 to 40, a moderate hardness that ensures sufficient mechanical scrubbing force without being too hard and causing wafer scratches. The outer diameter of the brush 320 ranges from 50 mm to 150 mm, and the thickness ranges from 10 mm to 30 mm; these dimensions can be customized according to wafer size and cleaning requirements. The brush 320 is formed into a porous, soft structure with good water absorption through a special pressing and cross-linking process. Furthermore, it undergoes multi-stage ultrapure water rinsing during production to ensure its initial cleanliness. The brush 320 can be replaced and fixed to the brush plate holder 310 via snap-fit ​​or threaded connection. This connection method is not only secure and reliable but also convenient and quick to replace, effectively reducing maintenance downtime.

[0053] The pressure sensing module 600 is a key component for achieving real-time contact pressure feedback, and its installation position is crucial to measurement accuracy. In a preferred embodiment, the pressure sensing module 600 is cleverly integrated inside the brush holder 310 near the base of the brush 320, or more precisely mounted on the axis connecting the brush assembly 300 and the support arm 200, to directly sense the contact force between the brush and the wafer. Its core component is a high-resolution miniature piezoelectric force sensor or strain gauge miniature load cell 610. These sensors are small in size but have extremely high measurement sensitivity and fast response. The sensor 610 makes direct or precision-machined miniature force transmission contact with the base of the brush 320, thereby enabling real-time and accurate measurement of the contact pressure between the brush 320 and the wafer surface. The measurement range of the pressure sensing module 600 is designed to be from 0.1 Newtons to 10 Newtons, which is sufficient to cover the typical contact pressure values ​​required for semiconductor cleaning. Its resolution can reach 0.01 Newtons, allowing the system to detect extremely small pressure changes. More importantly, its data refresh rate is no less than 1000 Hz, ensuring a rapid and sensitive response to pressure during the brushing process, providing high-bandwidth real-time data for subsequent closed-loop control. The pressure sensing module 600 communicates with the integrated control system 700 via RS485 digital communication through a shielded cable. This digital communication method provides excellent anti-interference capabilities and reliable data transmission performance, especially in environments where electromagnetic noise may be generated, such as motors and power supplies. To ensure consistent measurement accuracy throughout the entire working cycle, all sensors 610 undergo rigorous multi-point precision calibration before installation, and temperature compensation and creep effect elimination processing are performed to ensure measurement stability under different ambient temperatures and long-term operation. The sensor output data also undergoes internal filtering and noise reduction processing to provide a clean and reliable pressure feedback signal. The sensor 610 is fixed inside the brush plate bracket by a rigid isolation bracket, and a miniature ceramic force transmission rod is used for direct contact between the sensor and the brush base. The calibration process includes performing three-point calibration (0N, 5N, 10N) using standard weights at an ambient temperature of 20-25°C, and recording the temperature compensation coefficient.

[0054] The integrated control system 700 is the brain of this invention. It is responsible for receiving feedback signals from the pressure sensing module 600 and precisely regulating the vertical motion mechanism 400 and the rotary drive mechanism 500 according to a preset control strategy, thereby achieving dynamic, closed-loop control of the contact pressure between the brush and the wafer and precise coordination of the brushing motion. The integrated control system 700 includes a main controller 710, a motion controller 720, a data acquisition module 730, and a cleaning formula database 740.

[0055] The main controller 710, acting as an industrial-grade programmable logic controller (PLC) or industrial computer (IPC), undertakes the highest-level management and coordination functions of the entire brushing unit 100. Its operating system typically employs a real-time operating system (RTOS) or embedded Linux to ensure real-time response and stability. The main controller 710 is responsible for the process management of the entire brushing unit, the status monitoring of each subsystem, multiple safety interlocks (e.g., preventing large-scale vertical movement while the brushes are rotating at high speed), and communication with the main control system of the cleaning machine. Through an industrial Ethernet interface (e.g., Modbus TCP / IP or OPC UA), the main controller 710 can exchange data and receive commands with the factory's MES (Manufacturing Execution System) or SCADA (Supervisory Control and Data Acquisition) system, achieving seamless integration with the automated production line. The main controller 710 also integrates a logging function, recording parameters, pressure curves, and abnormal events for each cleaning cycle, providing data support for process optimization and fault diagnosis.

[0056] The motion controller 720 is the core of high-precision motion control. It typically employs a multi-axis servo motion controller and communicates with the main controller 710 via a high-speed, real-time industrial Ethernet protocol (e.g., EtherCAT or Profinet). The motion controller 720 receives motion commands from the main controller 710, including target contact pressure, brush path, and rotational speed. Based on real-time position and speed feedback from the high-resolution linear encoder 423 of the fine-tuning vertical motion mechanism 420 and the high-resolution incremental rotary encoder 520 of the rotary drive mechanism 500, the motion controller 720 utilizes its internal high-speed DSP (Digital Signal Processor) or FPGA (Field Programmable Gate Array) to perform complex motion control algorithm calculations. This precisely controls the current, frequency, and phase of the precision servo motor 421 in the vertical motion mechanism 400 and the brushless DC servo motor 510 in the rotary drive mechanism 500, thereby achieving precise control of the motor position, speed, and torque. The motion controller 720 features multi-axis synchronous interpolation, enabling precise coordination of the brush disk in vertical, rotational, and possibly radial or axial composite motion modes, ensuring smoothness and repeatability of the motion trajectory.

[0057] The data acquisition module 730 acts as a bridge between the pressure sensing module 600 and the motion controller 720. Its function is to acquire and preprocess the digital output signal of the pressure sensor 610 in real time. This module typically includes a high-precision analog-to-digital converter (ADC) to convert the sensor's analog signal into a digital signal. If the sensor itself outputs a digital signal (such as RS485), it is mainly responsible for parsing and verifying the data packets. The preprocessing steps include advanced digital filtering of the signal (e.g., Kalman filtering or moving average filtering) to eliminate environmental noise and the sensor's own minor fluctuations, and unit conversion to convert the raw sensor data into standard physical quantities (e.g., from millivolts to Newtons), ensuring that the motion controller 720 receives accurate, clean, and highly real-time pressure values. The data acquisition module 730 transmits the processed pressure values ​​to the motion controller 720 at a high frame rate (typically consistent with the refresh rate of the pressure sensing module, not less than 1000 Hz) to meet the real-time data requirements of the closed-loop control system.

[0058] The Cleaning Recipe Database 740 is a crucial component of intelligent cleaning management. It stores brushing parameter sets corresponding to different wafer types (e.g., silicon wafers, silicon carbide wafers, gallium arsenide wafers), wafer thicknesses (from 50-micron ultrathin wafers to standard wafers of several hundred microns), process stages (e.g., front-end cleaning, back-end cleaning, pre-packaging cleaning), and contaminant types (e.g., particles, metal contaminants, organic residues). Each parameter set has undergone extensive experimental verification and optimization to ensure optimal cleaning results and wafer yield. A typical parameter set includes: target contact pressure (set to an accuracy of 0.05 Newtons), brush rotation speed (accurate to 1 revolution / minute), brushing path mode (e.g., center-to-edge spiral brushing, radial reciprocating brushing, targeted fine cleaning), cleaning fluid type and flow rate, brushing time, and brush life thresholds. Before the brushing begins, the main controller 710 automatically retrieves the matching brushing parameter set from the cleaning recipe database 740 based on the received wafer ID or process batch information (usually issued through the MES system), thereby automating and intelligentizing the cleaning process, reducing manual intervention and potential errors. For example, for a silicon wafer with a thickness of 775±50 micrometers, the parameter set is: target contact pressure 2.50±0.02 Newtons, brush rotation speed 800 rpm, brushing path spiral (speed 0.5 mm / s), cleaning fluid SC-1 mixture (flow rate 500 ml / min), and brushing time 90 seconds.

[0059] The core of the wafer brushing device and its control method provided by this invention lies in an advanced PID (Proportional-Integral-Derivative) closed-loop control algorithm, which is applied to the dynamic adjustment of contact pressure. The specific implementation steps are as follows:

[0060] Before wafer cleaning, wafer positioning and pre-wetting are performed. Wafer 103 is precisely gripped by a precision robotic arm (not shown) and firmly placed in the center of the wafer support stage 102 of the cleaning machine, ensuring the wafer surface is level and accurately positioned. Subsequently, the spray system 104 is activated, uniformly spraying high-purity deionized water (DI water) or pre-cleaning solution (e.g., diluted ammonia) onto the surface of wafer 103 through high-purity nozzles, thoroughly pre-wetting the wafer surface. This step aims to reduce the hydrophobicity of the wafer surface, increase the uniformity of surface tension, allowing the brush to make smooth contact with lower resistance, and adequately prepare for the subsequent spreading and brushing of the cleaning solution, while also helping to remove larger, loose particles from the surface. The pre-wetting duration is typically set between 5 and 15 seconds to ensure the wafer surface is completely wetted.

[0061] Next comes the coarse descent of the brush assembly. The coarse adjustment vertical motion unit 410 of the vertical motion mechanism 400 (e.g., a pneumatic linear actuator) is activated, causing the support arm 200 to rapidly descend the brush assembly 300 at a relatively high speed (e.g., 100 mm / s to 200 mm / s). This descent continues until the brush assembly 300 reaches a preset coarse height from the surface of the wafer 103. This coarse height is typically precisely calibrated beforehand during equipment commissioning, or provided by the cleaning recipe database 740 based on the current wafer type and thickness, ensuring a minimum safety clearance of approximately 1 mm to 5 mm between the brush and the wafer surface to avoid collision. The primary goal of this stage is to efficiently shorten the stroke for fine adjustments, thereby significantly improving overall work efficiency. The speed and distance of the coarse descent are monitored by a safety interlock mechanism to prevent accidental collisions.

[0062] Subsequently, precise approach and initial contact detection of the brush disk are performed. During this stage, the motion controller 720 activates the precision servo motor 421 of the fine-tuned vertical motion unit 420, driving the brush disk assembly 300 to move downwards continuously at an extremely slow and controlled speed (e.g., 100 micrometers / second to 500 micrometers / second). As the brush disk assembly 300 descends, the pressure sensing module 600 continuously monitors the real-time contact pressure between the brush 320 and the wafer 103 at a high frequency (e.g., once per millisecond). Once the pressure sensor 610 detects initial contact between the brush 320 and the wafer surface, i.e., the contact pressure value reaches a preset small threshold (e.g., 0.05 Newtons to 0.1 Newtons, this threshold is rigorously determined experimentally to distinguish between actual mechanical contact between the brush and the wafer and minor fluctuations caused by environmental noise or airflow), the motion controller 720 immediately records the vertical position of this point as the "zero contact position" and stops the precise descent. This "zero contact position" is the reference point for all subsequent pressure control, and its accuracy directly affects the setting accuracy of the contact pressure.

[0063] Once the initial contact is accurately detected, the system immediately enters the contact pressure closed-loop control phase. The motion controller 720 retrieves the target contact pressure setpoint (P) for the current wafer from the cleaning formula database 740. set ), and real-time contact pressure feedback value (P) from pressure sensing module 600. feedback The precise vertical displacement adjustment is calculated using an advanced PID closed-loop control algorithm. The specific implementation details of the PID algorithm here include:

[0064] Proportional term (P): Based on the current pressure error (P) error = P set - P feedback The vertical displacement is adjusted instantaneously according to the ratio of the error. The larger the error, the larger the adjustment. This provides a rapid response capability, allowing the system to quickly approach the target pressure. Its gain coefficient K p The setting needs to balance response speed and stability; an excessively large K... p This could lead to system oscillations.

[0065] Integral term (I): Eliminates steady-state error by accumulating historical pressure errors. When small, persistent pressure deviations exist, the integral term accumulates continuously, generating a sustained adjustment to ensure that the final contact pressure reaches the set value accurately and without error. The gain coefficient K of the integral term... i The setting of K determines the speed at which steady-state errors are eliminated, but an excessively large K... i This may cause system overshoot.

[0066] The differential term (D) predicts future pressure change trends and adjusts accordingly based on the rate of pressure change, acting as a damper. This term is sensitive to the rate of pressure change, helping to suppress overshoot and oscillations, and improving system stability and response smoothness. The gain coefficient K of the differential term... d The settings need to be optimized based on the system's inertia and response characteristics.

[0067] The motion controller 720 sends the calculated vertical displacement adjustment amount to the servo motor driver of the fine-tuning vertical motion unit 420 in real time, driving the precision servo motor 421 to drive the high-precision ball screw transmission mechanism 422 to perform micron-level fine adjustments until P feedback Exact match P setThe error is maintained within ±0.02 Newtons. The entire adjustment process is real-time and dynamic, with the system response time strictly controlled to less than 50 milliseconds. This means the system can react to pressure fluctuations in a very short time, ensuring that the contact pressure remains constant and uniform during the washing process. PID parameter optimization typically employs the Ziegler-Nichols method or a model-predictive adaptive tuning algorithm to ensure optimal control performance under various operating conditions. For example, the gain coefficients can be set to Kp=0.5, Ki=0.1, Kd=0.05, or tuned using the Ziegler-Nichols method. The specific optimization process includes: applying a step input to the system under no-load conditions, measuring the response curve, and adjusting Kp, Ki, and Kd until the overshoot is <5% and the settling time is <100 milliseconds.

[0068] Once the contact pressure stabilizes at the target setpoint, the brush rotation and washing execution phase begins. The brushless DC servo motor 510 of the rotary drive mechanism 500 is activated, driving the brush assembly 300 to rotate at a precise speed set in the cleaning formula database 740. Precise speed control (e.g., 500 rpm ± 0.5%) is crucial for uniform cleaning. Simultaneously, the cleaning fluid supply system 105, based on the formula parameters, delivers a precise flow rate of cleaning fluid (e.g., ultrafiltered high-purity deionized water, diluted SC-1 or SC-2 cleaning fluid, or ozone-rich aqueous solution) to the contact area between the brush 320 and the wafer 103 via fluid channels within the support arm 200. The cleaning fluid flow rate is typically precisely controlled using a micro peristaltic pump or mass flow controller to ensure effective cleaning. Throughout the brushing process, the integrated control system 700 continuously monitors the feedback signal from the pressure sensing module 600 and dynamically adjusts the vertical displacement to compensate for contact pressure fluctuations caused by factors such as brush bristle wear, changes in cleaning fluid viscosity, local unevenness of the wafer, or system thermal expansion. This dynamic compensation mechanism ensures that the contact pressure remains constant and uniform throughout the brushing cycle, avoiding cleaning problems caused by excessive or insufficient local pressure.

[0069] To further improve cleaning uniformity, this invention also supports brushing path optimization and compound motion. The motion controller 720 can coordinate the fine-tuning vertical motion unit 420 and the rotary drive mechanism 500 according to instructions from the cleaning formula database 740 to achieve compound motion of the brush assembly 300. This compound motion is not just a single rotation, but can also superimpose multiple motion modes. For example, while maintaining constant contact pressure, the brush can perform a slight radial reciprocating oscillation. If this radial oscillation is achieved by controlling the fine-tuning vertical motion unit 420 to make slight movements in the horizontal direction, it should be further described how the fine-tuning vertical motion unit 420 possesses the ability to make slight movements in the horizontal direction, for example, by adding an XY plane motion platform or using a flexible hinge structure; if it is achieved by an independent radial motion mechanism (not shown), it is necessary to further describe the specific structure, working principle, and interface with the integrated control system (700) of this independent radial motion mechanism. The oscillation amplitude can typically reach 2 mm to 5 mm, and the oscillation frequency can reach 2 Hz to 5 Hz. Furthermore, the brush can also move slowly along a specific spiral path, gradually brushing from the center of the wafer to the edge, or from the edge to the center. This spiral path is achieved through precise interpolation control of the brush rotation and radial / vertical movement axes by the motion controller 720. This combination of multiple motion modes allows the brush 320 to cover the wafer 103 surface more comprehensively and evenly. Especially for wafers with complex three-dimensional structures (such as FinFET and 3D NAND), this composite motion can effectively remove contaminants from recesses or high-ratio structures, achieving a level of cleanliness that is difficult to achieve with traditional single-rotation brushing. The smoothness and precision of the composite motion rely on the high-precision synchronous control capability of the servo motor, ensuring coordinated movement of each axis without abrupt changes or jitter. The brush assembly 300 can be further connected to the rotary drive mechanism 500 via an XY plane motion platform integrated into the lower end of the support arm 200. The XY platform consists of two mutually perpendicular linear modules. Each module contains a miniature stepper motor or piezoelectric actuator and a corresponding displacement sensor, controlled by a motion controller 720. This allows the brush assembly 300 to achieve precise radial reciprocating oscillation or helical movement in the horizontal plane while maintaining vertical pressure control. The platform is designed for high rigidity and low friction, and uses high-cleanliness materials.

[0070] The composite motion control employs a linear interpolation algorithm. For example, the motion controller generates a radial displacement command S(t) = A·sin(2πft), where A is the amplitude (2-5mm) and f is the frequency (2-5Hz), and synchronizes it in real time with the rotation axis position θ(t). Path data is stored in the database in G-code format.

[0071] After the brushing cycle is completed, the brush assembly 300 enters the brush lifting and wafer transfer stage. The integrated control system 700 first instructs the fine-tuning vertical motion unit 420 to lift the brush assembly 300 at a controlled speed (e.g., 500 μm / s to 1000 μm / s). This lifting process continues until the pressure sensor 610 detects that the contact pressure has dropped to zero, indicating that the brush 320 has completely detached from the wafer surface and there is no residual contact force. Subsequently, the coarse-tuning vertical motion unit 410 can further lift the brush assembly 300 quickly to a safe height (e.g., 100 mm to 200 mm from the wafer surface) to facilitate subsequent wafer transfer. The brushed wafer 103 is picked up by a precision robotic arm and transferred to the next cleaning station in the cleaning machine (e.g., high-pressure rinsing and rotary drying in a spray chamber) or transferred to an external storage and transport cassette to await the next processing step. During the brush lifting process, the system also performs a brush self-cleaning procedure, which removes particles and residual chemicals adhering to the brush through high-speed rotation and spraying of cleaning fluid, preparing it for the next cleaning.

[0072] Example

[0073] This embodiment aims to verify the performance advantages of the "a brushing device and its control method based on dynamic adjustment of wafer thickness" disclosed in this invention in actual wafer cleaning.

[0074] Test subjects: A batch of 300 mm diameter silicon wafers with batch-to-batch thickness variations ranging from 775 μm ± 50 μm (i.e., 725 μm to 825 μm). The wafer surface had an oxide layer pre-prepared using a chemical vapor deposition (CVD) process and was subsequently contaminated by nanoscale silicon particles (silicon dioxide particles, average particle size 50 nm) and small amounts of organic matter (such as photoresist residue) during subsequent processes.

[0075] Cleaning objective: To reduce the number of particles larger than 0.0 nanometers on the wafer surface to less than 10 per wafer, and to effectively remove organic contaminants while ensuring that there are no new scratches or damages on the wafer surface.

[0076] Cleaning solution: a mixed solution of diluted ammonia (NH4OH) and hydrogen peroxide (H2O2) (SC-1 standard cleaning solution, volume ratio NH4OH:H2O2:DI Water = 1:1:50).

[0077] Brush material: PVA sponge brush, porosity 85%, average pore size 100 micrometers, Shore A hardness 30.

[0078] Setting parameters:

[0079] Target contact pressure (P) set ): 2.50 Newtons.

[0080] Brush rotation speed: 800 rpm.

[0081] The brushing path is spiraled outward from the center of the wafer at a speed of 0.5 mm / s to the edge, and then performs a radial reciprocating oscillation with a amplitude of 2 mm in the edge region at a frequency of 3 Hz.

[0082] Cleaning fluid flow rate: 500 ml / min.

[0083] Scrubbing time: 90 seconds.

[0084] Implementation process:

[0085] 1. The wafer is automatically transferred to the wafer support stage, and the spray system sprays DI water for pre-wetting for 10 seconds.

[0086] 2. The vertical motion unit is coarsely adjusted to quickly lower the brush to a distance of about 2 mm from the wafer surface.

[0087] 3. The vertical motion unit is finely adjusted to descend slowly at a speed of 200 micrometers per second, while the pressure sensing module continuously monitors. When the pressure sensor detects that the contact pressure reaches the initial contact threshold of 0.08 Newtons, this vertical position is recorded as the "zero contact position".

[0088] 4. The integrated control system initiates PID closed-loop control, dynamically adjusting the vertical position of the fine-tuning vertical motion unit based on real-time feedback from the pressure sensor module, stabilizing the contact pressure at the target value of 2.50 N ± 0.02 N within 50 milliseconds. Throughout the entire 90-second brushing process, the system continuously and dynamically adjusts to compensate for height differences caused by wafers of varying thicknesses and bristle wear, maintaining constant pressure.

[0089] 5. The brush plate rotates at a speed of 800 rpm and performs compound motion according to a preset spiral path, while precisely supplying SC-1 cleaning fluid.

[0090] 6. After brushing, the fine-tuning vertical motion unit raises the brush disk at a speed of 800 micrometers / second until the pressure reaches zero, and then the coarse-tuning unit raises it to a safe height. The wafer is then transferred to the subsequent rinsing and drying process.

[0091] Comparative Example

[0092] To highlight the advantages of this invention, this comparative example uses a common fixed-brush-height single-wafer cleaning device in the prior art for cleaning. The set height is preset according to the standard wafer thickness (775 micrometers). Other conditions are consistent with those in the above embodiments, including wafer type, initial contamination, cleaning solution, brush rotation speed, cleaning path, and cleaning time.

[0093] Fixed height setting: The brush height is set to the height that generates 2.50 Newtons of contact pressure on a standard 775-micron thick wafer.

[0094] Comparative process:

[0095] 1. Similar to the embodiment, after the wafer is pre-wetted, the brush disk descends to a preset fixed height. Due to batch variations of ±50 micrometers in wafer thickness, the actual contact pressure fluctuates with the wafer thickness. For example, for a wafer with a thickness of 725 micrometers, the actual contact pressure may be as high as 3.50 Newtons to 4.00 Newtons because the relative position of the brushes remains unchanged; while for a wafer with a thickness of 825 micrometers, the actual contact pressure may only be 1.50 Newtons to 1.80 Newtons.

[0096] 2. The brush plate starts to rotate and executes the brushing path, but due to the inability to dynamically adjust the contact pressure, the actual pressure difference on wafers of different thicknesses causes fluctuations in the cleaning effect.

[0097] 3. After cleaning, the brush plate is raised and the wafer is transferred.

[0098] Data Comparison

[0099] The table below compares the key performance indicators of this embodiment (using the technology of this invention) and the comparative example (using existing fixed height technology) in terms of cleaning effect, wafer damage, and brush life. All data are average statistical results after cleaning 100 wafers.

[0100]

[0101] Data Analysis:

[0102] The data above clearly demonstrates that the embodiments of this invention exhibit significant advantages in several key performance indicators. Regarding the number of residual particles larger than 100 nanometers, this invention achieves a significantly lower number of residual particles per wafer compared to the comparative example. This directly reflects the superior ability of dynamic pressure control to improve cleaning thoroughness. By precisely maintaining the contact pressure at the target value of 2.50 Newtons, the brush can contact the wafer surface with optimal mechanical conditions, effectively shearing and removing attached particles while avoiding low cleaning efficiency due to insufficient pressure. In the comparative example, the fixed height could not accommodate differences in wafer thickness, resulting in insufficient contact pressure on some wafers, thus failing to effectively remove particles and exhibiting a higher number of residual particles.

[0103] Regarding organic residue, the embodiments of the present invention also exhibit lower residue levels. Precise contact pressure ensures a consistently stable mechanical interaction between the brush and the wafer surface, which, combined with the chemical action of the cleaning solution, more efficiently breaks down and removes organic contaminants from the surface. In contrast, the wafers with insufficient contact pressure in the comparative examples showed poor organic residue removal.

[0104] Crucially, regarding the newly added surface scratch rate, this embodiment of the invention controls the scratch rate to an extremely low level of less than 0.01%, achieving near-zero scratch cleaning. This is thanks to the synergistic effect of the high-precision vertical motion mechanism and the PID closed-loop control algorithm. The system ensures that the brush establishes and releases contact with the wafer surface in a controlled and smooth manner, avoiding wafer scratches caused by excessive local pressure throughout the brushing process. In the comparative example, some wafers, due to their thinness, were subjected to contact pressure far exceeding the design limit, causing excessive friction between the brush and the wafer surface, thus introducing unacceptable scratches.

[0105] Regarding consumable lifespan, the effective lifespan of the brush is a crucial indicator for measuring operating costs. In this embodiment of the invention, the effective lifespan of the brush is significantly extended to over 500 brushes, which is twice or even more than that of the comparative model (150-250 brushes). This is directly attributed to the precise control of the brush contact pressure. During the brushing process, the brush avoids unnecessary excessive pressure wear and also avoids uneven local friction caused by insufficient pressure. The constant optimal contact pressure significantly reduces fatigue and wear of the brush material, thereby reducing the frequency of consumable replacement and operating costs.

[0106] Finally, the embodiments of the present invention demonstrate excellent performance in terms of cleaning yield and cleaning uniformity (measured by the standard deviation (RSD) of contamination distribution on the wafer surface). A cleaning yield of over 99.8% and a cleaning uniformity RSD of less than 2% indicate that the present invention can consistently provide high-quality cleaning results. Regardless of wafer thickness fluctuations, the system can adaptively adjust to ensure that each wafer receives consistent and thorough cleaning. In the comparative examples, due to inconsistent contact pressure, the cleaning effect varied significantly between different areas and even different batches of wafers, resulting in unsatisfactory cleaning yield and uniformity.

[0107] In summary, the wafer thickness-based dynamic adjustment cleaning device and its control method disclosed in this invention effectively solve the core technical challenges of unstable cleaning quality, wafer damage, and short consumable lifespan caused by wafer thickness differences in existing technologies through systematic innovation in structure and control strategies. The implementation of this technical solution not only significantly improves the precision, reliability, and efficiency of wafer cleaning in semiconductor manufacturing, but also provides strong technical support for improving yield and optimizing costs in advanced processes. It fully meets the stringent requirements of the current semiconductor industry for high cleanliness, high yield, and low operating costs, and has broad application prospects and profound economic and social benefits.

Claims

1. A brushing device (100) based on dynamic adjustment of wafer thickness, characterized in that, include: One support arm (200); A vertical motion mechanism (400) is connected to the support arm (200) to realize the vertical displacement of the support arm (200) and the brush assembly (300) it carries. The vertical motion mechanism (400) includes a coarse adjustment vertical motion unit (410) and a fine adjustment vertical motion unit (420). The fine adjustment vertical motion unit (420) is composed of a precision servo motor (421), a high-precision ball screw transmission mechanism (422), and a high-resolution linear encoder (423). Its position control accuracy reaches ±0.5 micrometers, and the minimum step size is controlled below 1 micrometer. A rotary drive mechanism (500) is connected to the support arm (200) for driving the brush assembly (300) to rotate; A brush assembly (300) is mounted on the lower end of the support arm (200) and connected to the rotary drive mechanism (500) for brushing contact with the surface of the wafer (103), the brush assembly (300) including a brush (320). A pressure sensing module (600) whose core component is a high-resolution miniature piezoelectric force sensor or a strain gauge miniature load cell (610), wherein the sensor has a measurement resolution of up to 0.01 Newtons and a refresh rate of not less than 1000 Hz. An integrated control system (700) includes a motion controller (720) that receives real-time feedback signals from the pressure sensing module (600) and uses a PID closed-loop control algorithm to precisely regulate the fine-tuning vertical motion unit (420), thereby achieving dynamic, closed-loop control of the contact pressure between the brush (320) and the surface of the wafer (103), so that the contact pressure is maintained at the target set value and the error is kept within ±0.02 Newtons, and the response time of the entire adjustment process is less than 50 milliseconds.

2. The scrubbing device (100) according to claim 1, characterized in that, The vertical motion mechanism (400) is mounted on the cleaning machine frame (101) and ensures the stability and no sway of the support arm (200) during vertical movement through a precision guide rail. The vertical motion mechanism (400) includes a coarse adjustment vertical motion unit (410) and a fine adjustment vertical motion unit (420). The coarse adjustment vertical motion unit (410) is used to realize the rapid and wide-range vertical lifting and lowering of the support arm (200) and the brush assembly (300) it carries. The fine adjustment vertical motion unit (420) works in series or in parallel with the coarse adjustment vertical motion unit (410) to realize the micron-level precise vertical displacement adjustment of the support arm (200) and the brush assembly (300) it carries.

3. The scrubbing device (100) according to claim 2, characterized in that, The coarse adjustment vertical motion unit (410) employs a pneumatic linear actuator, which drives the piston rod to move linearly along a preset guide rail by high-pressure gas, and is equipped with a stroke limit switch or linear encoder to provide coarse position feedback. The maximum stroke of the pneumatic linear actuator can reach 200 mm to 300 mm, and the maximum operating speed can reach 200 mm / s to 500 mm / s, which is used to shorten the fine adjustment stroke during the brushing process.

4. The scrubbing device (100) according to claim 2, characterized in that, The fine-tuning vertical motion unit (420) consists of a precision servo motor (421), a high-precision ball screw transmission mechanism (422), and a high-resolution linear encoder (423). The precision servo motor (421) drives the ball screw transmission mechanism (422) to rotate through closed-loop control, thereby driving the support arm (200) connected to the screw nut to perform precise vertical movement. The high-resolution linear encoder (423) is directly installed on the vertical movement path of the support arm (200) to provide real-time, submicron-level vertical position feedback, ensuring that the position control accuracy of the fine-tuning vertical motion unit (420) reaches ±0.5 microns. The minimum step size of the fine-tuning vertical motion unit (420) can be controlled below 1 micron, and the maximum adjustment speed can reach 5 mm / s to 10 mm / s.

5. The scrubbing device (100) according to claim 1, characterized in that, The core component of the pressure sensing module (600) is a high-resolution miniature piezoelectric force sensor or strain gauge miniature load cell (610). The sensor (610) is in direct contact with the base of the brush (320) or through a miniature force transmission rod. The pressure sensing module (600) has a measurement range of 0.1 Newton to 10 Newton, a resolution of up to 0.01 Newton, a refresh rate of not less than 1000 Hz, and RS485 digital communication with the integrated control system (700) via a shielded cable. It is also precisely calibrated before installation to eliminate temperature drift and creep effects.

6. The scrubbing device (100) according to claim 1, characterized in that, The integrated control system (700) includes a main controller (710), a motion controller (720), a data acquisition module (730), and a cleaning formula database (740). The main controller (710) is an industrial-grade programmable logic controller (PLC) or industrial computer (IPC), responsible for the process management, status monitoring, safety interlocking, and communication with the main control system of the cleaning machine of the entire scrubbing device (100). The motion controller (720) is a multi-axis servo motion controller, which communicates with the main controller (710) via... Industrial Ethernet enables high-speed communication, receiving motion commands and precisely controlling the servo motor (421) of the vertical motion mechanism (400) and the servo motor (510) of the rotary drive mechanism (500) based on real-time feedback; the data acquisition module (730) is connected to the pressure sensing module (600) and is responsible for real-time acquisition and preprocessing of the digital output signal of the pressure sensor; the cleaning formula database (740) stores a set of brushing parameters corresponding to different types of wafers, different wafer thicknesses, different process stages, and different types of contaminants.

7. The scrubbing device (100) according to claim 6, characterized in that, The motion controller (720) calculates the precise vertical displacement adjustment amount using a PID closed-loop control algorithm based on the real-time position / velocity feedback from the high-resolution linear encoder (423) and the high-resolution incremental rotary encoder (520), as well as the real-time precise pressure value from the data acquisition module (730). The adjustment amount is then sent to the servo motor driver of the fine-tuning vertical motion unit (420) to maintain the contact pressure between the brush assembly (300) and the wafer (103) at the target set value, with the error kept within ±0.02 Newtons. The response time of the entire adjustment process is less than 50 milliseconds.

8. The scrubbing device (100) according to claim 6, characterized in that, Each brushing parameter set stored in the cleaning recipe database (740) includes: target contact pressure (set value can be accurate to 0.05 Newtons), brush rotation speed (accurate to 1 revolution / minute), brushing path mode (e.g., spiral brushing, radial reciprocating brushing), cleaning fluid flow rate, brushing time, and brush life threshold; the main controller (710) automatically retrieves the matching brushing parameter set from the cleaning recipe database (740) according to the received wafer ID or process batch information.

9. The scrubbing device (100) according to claim 1, characterized in that, The brush assembly (300) includes a brush holder (310) and a brush (320); the brush holder (310) is made of polyetheretherketone (PEEK) or polytetrafluoroethylene (PTFE), and is lightweight and highly rigid, and integrates a quick-installation and disassembly mechanism for the brush (320); the brush (320) is made of polyvinyl alcohol (PVA) sponge material with a porosity ranging from 80% to 95%, an average pore size ranging from 50 micrometers to 200 micrometers, a Shore hardness ranging from Type A 20 to 40, an outer diameter ranging from 50 millimeters to 150 millimeters, and a thickness ranging from 10 millimeters to 30 millimeters, and is formed into a porous, soft structure with good water absorption by a special pressing process, and can be replacedly fixed to the brush holder (310) by snap-fit ​​or threaded connection.

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