Servo motor driven pressure control and cushion system for semiconductor wafer polishing

Abstract

The application discloses a servo electric cylinder driving pressure control and buffer system for semiconductor wafer grinding, relates to the technical field of semiconductor manufacturing equipment, and comprises a servo electric cylinder main body, a composite bearing supporting module, a pressure detection module, a dynamic buffer module, a hydraulic supply module and a central control module. The composite bearing supporting module provides support for a driving shaft. A dynamic pressure bearing assembly and a static pressure bearing assembly are arranged alternately in the axial direction in a bearing seat inner hole to form an integrated support structure. The pressure detection module is used for real-time detection of the actual grinding pressure of a grinding head. The dynamic buffer module is used for dynamically adjusting the buffer stiffness according to the grinding pressure change. The hydraulic supply module detects the oil pressure of a main oil way. The central control module adjusts the servo motor output torque and the pressure regulating valve opening degree, and controls the buffer stiffness simultaneously. The vibration suppression and operation reliability problems in the rotating equipment are solved. The two bearing technologies are integrated and cooperatively designed, and the function complementation and performance multiplication are realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing equipment technology, and more specifically, to a servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding. Background Technology

[0002] In semiconductor wafer manufacturing, the polishing process is one of the key steps determining the surface flatness, roughness, and dimensional accuracy of the wafer. As semiconductor technology advances towards higher aspect ratios and smaller linewidths, the precision requirements for wafer polishing have reached the nanometer level. This necessitates that the drive and pressure control systems of polishing equipment possess extremely high control accuracy, operational stability, and anti-interference capabilities. Currently, the pressure drive and buffer systems of semiconductor wafer polishing equipment mostly adopt a structure of "servo electric cylinder + single bearing support," where the bearing, as the core supporting component, directly affects the system's pressure control accuracy and operational stability. Existing bearing solutions are mainly divided into two categories: hydrodynamic bearings and hydrostatic bearings, but both have significant limitations.

[0003] Existing technologies have several shortcomings: while hydrodynamic bearings have a relatively simple structure, they are extremely sensitive to assembly precision under various dimensional conditions, and the conditions for forming a stable load-bearing oil film are demanding; hydrostatic bearings, although providing excellent static stiffness and damping characteristics, rely on external hydraulic systems, resulting in complex structures, high maintenance costs, and the risk of single-point failures. Therefore, to address the issues of insufficient vibration suppression, low reliability, and unadjustable buffering characteristics of existing single-bearing solutions, there is an urgent need to develop a pressure control and buffering system based on composite bearing integration technology to meet the extreme requirements of nanoscale wafer grinding.

[0004] To address the above problems, this invention proposes a solution. Summary of the Invention

[0005] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding. By developing a pressure control and buffering system based on composite bearing integration technology, the problems mentioned in the background art are solved.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding includes a servo electric cylinder body, a composite bearing support module, a pressure detection module, a dynamic buffering module, a hydraulic supply module, and a central control module. The main body of the servo electric cylinder includes a servo motor, a ball screw, a drive shaft, and a grinding head connecting seat; The composite bearing support module provides support for the drive shaft, including a bearing housing, a hydrodynamic bearing assembly, and a hydrostatic bearing assembly. The hydrodynamic bearing assembly and the hydrostatic bearing assembly are arranged alternately in the axial direction within the bearing housing bore to form an integrated composite support structure. The pressure detection module is used to detect the actual grinding pressure of the grinding head in real time; The dynamic buffer module includes a buffer cylinder, a buffer piston, and an elastic adjustment component. The elastic adjustment component is disposed in a sealed cavity and is used to dynamically adjust the buffer stiffness according to the change of grinding pressure. The hydraulic supply module includes a hydraulic pump, a relief valve, a pressure regulating valve, an accumulator, and an oil pressure sensor. The oil pressure sensor detects the main oil circuit pressure in real time and feeds it back to the central control module. The central control module is used to adjust the output torque of the servo motor and the opening of the pressure regulating valve according to the deviation between the preset grinding pressure and the actual grinding pressure, while controlling the buffer stiffness of the elastic adjustment component to achieve coordinated control of pressure and vibration.

[0007] In a preferred embodiment, the servo motor drives the drive shaft to perform linear reciprocating motion via a ball screw, and the end of the drive shaft is connected to the wafer grinding head via a grinding head connector to transmit stable grinding pressure to the grinding head.

[0008] In a preferred embodiment, an annular gap is formed between the inner hole of the bearing housing and the drive shaft, serving as an oil film receiving cavity; The hydrodynamic bearing assembly includes multiple hydrodynamic oil grooves evenly opened along the circumference of the inner hole of the bearing housing. The hydrodynamic oil grooves adopt a bidirectional spiral groove structure to ensure that a stable hydrodynamic effect can be generated during the extension and retraction of the drive shaft. The hydrostatic bearing assembly includes multiple hydrostatic oil chambers evenly spaced along the circumference of the bearing housing's inner hole. These hydrostatic oil chambers are connected to the hydraulic supply module via oil circuits to generate a stable hydrostatic effect.

[0009] In a preferred embodiment, the process of real-time detection of the actual grinding pressure of the grinding head is as follows: During the grinding process, the pressure generated by the contact between the grinding head and the wafer directly acts on the sensor detection surface, and the piezoelectric sensor converts the pressure signal into a corresponding weak voltage signal. The weak voltage signal is transmitted to the signal conditioning module via a shielded cable and preprocessed sequentially. The preprocessed digital pressure signal is transmitted to the central control module. After receiving the signal, the control module substitutes it into the preset linear calibration formula, subtracts the zero-point offset voltage, and calculates the actual grinding pressure. Based on the preset temperature compensation coefficient and the real-time data from the built-in temperature sensor of the connector, the pressure value is temperature compensated to obtain the actual grinding pressure after temperature compensation. The actual grinding pressure after temperature compensation is then transmitted to the central control module for verification.

[0010] In a preferred embodiment, the actual grinding pressure, after temperature compensation, is transmitted to the central control module for verification as follows: The actual grinding pressure after temperature compensation is transmitted to the central control module. The central control module compares the pressure values ​​of two adjacent acquisitions in real time, calculates the pressure fluctuation, and if the pressure fluctuation is greater than the preset threshold, it is judged as an abnormal fluctuation, the data set is immediately marked and a second acquisition verification is initiated. If abnormal fluctuations are observed in three consecutive data acquisitions, or if the pressure value exceeds the preset safety range, the central control module will immediately issue an alarm signal and suspend the grinding process to avoid wafer damage or equipment failure. Abnormal pressure data will be recorded simultaneously for subsequent process optimization and troubleshooting.

[0011] In a preferred embodiment, the dynamic buffer module is disposed between the drive shaft and the grinding head connecting seat, and includes a buffer cylinder, a buffer piston, and an elastic adjustment component. The buffer cylinder is fixedly connected to the drive shaft, and the buffer piston is fixedly connected to the grinding head connecting seat. The buffer piston extends into the buffer cylinder to form a sealed cavity, ensuring that the initial pressure of the sealed cavity is standard atmospheric pressure. The elastic adjustment component is disposed in the sealed cavity, and the coil lead is connected to the current drive unit of the central control module to dynamically adjust the buffer stiffness according to the change of grinding pressure.

[0012] In a preferred embodiment, the process of dynamically adjusting the buffer stiffness according to changes in grinding pressure is as follows: When the grinding head is not in contact with the wafer, the initial position of the displacement sensor is recorded, 0A current is input to the excitation coil, and the initial stiffness of the elastic body is calibrated through a static loading experiment to ensure that the piston does not deviate under no pressure. The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module. The displacement sensor synchronously collects the real-time position of the piston and calculates the piston displacement by combining it with the initial position. If the pressure deviation is greater than the preset deviation threshold and the piston displacement is less than the displacement threshold, the stiffness adjustment process will be initiated. The pressure deviation is converted into an impact load by combining it with the effective piston area. To ensure that the piston displacement does not exceed the limit under the impact load, the target stiffness must satisfy the load-displacement constraint relationship. Combining the initial stiffness of the elastic body, the final total target stiffness to be output is calculated using the following formula: ; In the formula, It is the overall target stiffness. It is the initial stiffness of the elastic body. It's a pressure deviation. It is the effective area of ​​the piston. Displacement threshold; When the total target stiffness calculated by the formula exceeds the upper limit of the adjustable range of the elastic body stiffness, that is, when the buffer adjustment cannot meet the displacement constraint, the servo motor performs pressure compensation.

[0013] In a preferred embodiment, the output torque of the servo motor and the opening of the pressure regulating valve are adjusted according to the deviation between the preset grinding pressure and the actual grinding pressure, as follows: The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module. The voltage adjustment is calculated using a PID algorithm. Obtain the maximum output torque of the servo motor, and control the maximum output voltage and maximum opening. A linear proportional conversion formula is used to convert the voltage adjustment amount into the servo motor torque adjustment amount and the opening adjustment amount, thereby adjusting the servo motor output torque and the opening of the pressure regulating valve.

[0014] In a preferred embodiment, the process of calculating the voltage adjustment using a PID algorithm is as follows: The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module. The PID calculation unit built into the central control module performs proportional, integral, and derivative calculations on the deviation signal. The results of the three stages of calculation are summed to obtain the total PID control output, as shown in the following formula: ; In the formula, This is the total control output. It is the deviation amplification ratio factor. It's a pressure deviation. It is the integration time constant. It is the differential time constant.

[0015] In a preferred embodiment, the process of controlling the buffer stiffness of the elastic adjustment component is as follows: Based on the current-stiffness linear response characteristics of electromagnetic rheoelastic bodies, the required excitation current is deduced from the total target stiffness using the following formula: ; In the formula, for The target current of the excitation coil at any given time. It is the overall target stiffness. It is the initial stiffness of the elastic body. It is the current-stiffness linearity coefficient.

[0016] The technical effects and advantages of the servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding of the present invention are as follows: 1. This invention, through the innovative design of a composite bearing support module, integrates multi-size fluid shaft planar dynamic pressure bearings and fluid planar hydrostatic bearings, achieving synergistic operation and functional complementarity of the two bearing technologies. When the servo electric cylinder is operating normally and the hydraulic supply module is working stably, the hydrostatic oil film generated by the hydrostatic bearing assembly and the dynamic oil film generated by the dynamic pressure bearing assembly superimpose to form a high-strength composite oil film with extremely high stiffness and damping characteristics. This composite oil film effectively isolates and attenuates wide-frequency mechanical vibrations generated by transmission mechanisms such as servo motors and ball screws, ensuring smooth operation of the drive shaft and thus guaranteeing the stability of the grinding pressure. In the event of equipment start-up, shutdown, or unexpected failure of the hydrostatic system, the dynamic pressure bearing assembly can independently provide support force, avoiding direct contact and friction between the drive shaft and the bearing housing. This ensures the continuous and safe operation of the rotating mechanism (ball screw) and the linear drive mechanism (drive shaft), significantly improving the system's fault tolerance and operational reliability, and solving the technical bottleneck of existing single-bearing solutions.

[0017] 2. By precisely designing the structural parameters of the dynamic pressure oil groove and the static pressure oil chamber, and combining the derived calculation formulas for oil film thickness and load-bearing capacity, this invention can optimize the performance of the composite oil film according to the specific process requirements of semiconductor wafer grinding. This enables the total load-bearing capacity and stiffness of the composite bearing support module to meet the requirements of different grinding pressures and different wafer materials, further improving the accuracy of pressure control. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all 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.

[0020] Example 1, Figure 1 This invention presents a servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding. It includes a servo electric cylinder body, a composite bearing support module, a pressure detection module, a dynamic buffering module, a hydraulic supply module, and a central control module.

[0021] The servo electric cylinder body is the core execution unit for transmitting grinding pressure. Its performance directly determines the stability and control accuracy of the grinding pressure. Specifically, it includes a servo motor, a ball screw, a drive shaft, and a grinding head connector. The servo motor drives the drive shaft to perform linear reciprocating motion through the ball screw. The end of the drive shaft is connected to the wafer grinding head through the grinding head connector to transmit stable grinding pressure to the grinding head.

[0022] The composite bearing support module provides support for the drive shaft, including a bearing housing, a hydrodynamic bearing assembly, and a hydrostatic bearing assembly. The hydrodynamic bearing assembly and the hydrostatic bearing assembly are arranged alternately in the axial direction within the bearing housing bore to form an integrated composite support structure. The composite bearing support module is sleeved on the outside of the drive shaft, providing high-precision and high-stability support for the drive shaft. It includes a bearing housing, a hydrodynamic bearing assembly, and a hydrostatic bearing assembly. An annular gap is formed between the inner hole of the bearing housing and the drive shaft, serving as an oil film receiving cavity. The hydrodynamic bearing assembly includes multiple hydrodynamic oil grooves evenly spaced along the circumference of the inner hole of the bearing housing. The hydrodynamic oil grooves adopt a bidirectional spiral groove structure to ensure a stable hydrodynamic pressure effect during the extension and retraction of the drive shaft. The hydrostatic bearing assembly includes multiple hydrostatic oil chambers evenly spaced along the circumference of the inner hole of the bearing housing. The hydrostatic oil chambers are connected to the hydraulic supply module through oil circuits to generate a stable hydrostatic pressure effect. The hydrodynamic oil grooves and hydrostatic oil chambers are arranged alternately along the axial direction of the inner hole of the bearing housing, forming an integrated composite support structure, realizing the functional complementarity of the two bearing technologies.

[0023] The pressure detection module includes a pressure sensor, which is used to detect the actual grinding pressure of the grinding head in real time and transmit it to the central control module; The pressure detection module includes a high-precision pressure sensor built into the grinding head connector to detect the actual grinding pressure of the grinding head in real time. The process is as follows: During the grinding process, the pressure generated by the contact between the grinding head and the wafer directly acts on the sensor detection surface, and the piezoelectric sensor converts the pressure signal into a corresponding weak voltage signal. The weak voltage signal is transmitted to the signal conditioning module via a shielded cable and undergoes the following preprocessing steps: Differential amplification: amplifying the mV-level signal to the V-level (meeting the AD conversion requirements of the central control module); Low-pass filtering: filtering out high-frequency noise (frequency > 100Hz) such as drive shaft vibration and motor electromagnetic interference; AD conversion: converting the analog weak voltage signal into a digital voltage signal (sampling accuracy 16 bits). The preprocessed digital pressure signal is transmitted to the central control module via an RS485 bus. After receiving the signal, the control module substitutes it into a preset linear calibration formula, subtracts the zero-point offset voltage, and calculates the actual grinding pressure. The calculation formula is as follows:

[0024] In the formula, yes The grinding pressure after linear calibration and zero-point subtraction; These are linear calibration coefficients, obtained through calibration fitting using standard weights. yes The digital output value of the pressure sensor after AD conversion, with a 16-bit sampling range of 0~65535; This is the digital output value corresponding to the zero-point offset, obtained through actual measurement during the calibration phase; It is a linear correction term that compensates for fitting errors, and its value is typically set to [value missing]. N.

[0025] It should be noted that the sensor simulates the output voltage. With digital output value satisfy: ( The reference voltage for the AD converter is... (Sampling bit depth); combined with linear calibration relationship ( (For analog zero-point offset voltage), substitute into The conversion formula ultimately yields the direct calculation formula for digital quantities (avoiding analog quantity conversion errors). Based on a preset temperature compensation coefficient and real-time data from the built-in temperature sensor in the connector, the pressure value is compensated for temperature to further improve detection accuracy. The temperature compensation calculation formula is as follows:

[0026] In the formula, yes The actual grinding pressure after temperature compensation at all times; This is the temperature coefficient of the pressure sensor, provided by the sensor datasheet; the value used in this solution is... (Right now ); yes The real-time temperature of the grinding head connector is detected by the built-in NTC temperature sensor; This is the calibration reference temperature, the default value. ; The piezoelectric coefficient of a piezoelectric sensor changes with temperature, causing a shift in the output signal under the same pressure. The amount of this shift is related to the temperature deviation. The relationship is linear; when the temperature is higher than At that time, the sensor output signal is too large and needs to be adjusted by a coefficient. Correct pressure value; temperature below At that time, the output signal was too small, and the pressure value was slightly increased after correction; The actual grinding pressure after temperature compensation is transmitted to the central control module. The central control module compares the pressure values ​​of two adjacent acquisitions in real time, calculates the pressure fluctuation, and if the pressure fluctuation is greater than the preset threshold, it is judged as an abnormal fluctuation, the data set is immediately marked and a second acquisition verification is initiated. If abnormal fluctuations are observed in three consecutive data acquisitions, or if the pressure value exceeds the preset safety range (e.g., >500N or <0N), the central control module will immediately issue an alarm signal and suspend the grinding process to avoid wafer damage or equipment failure. Abnormal pressure data (including timestamps and temperature values) will be recorded simultaneously for subsequent process optimization and troubleshooting.

[0027] The dynamic buffer module includes a buffer cylinder, a buffer piston, and an elastic adjustment component. The buffer cylinder is fixedly connected to the drive shaft, and the buffer piston is fixedly connected to the grinding head connecting seat. The buffer piston extends into the buffer cylinder to form a sealed cavity. The elastic adjustment component is set in the sealed cavity and is used to dynamically adjust the buffer stiffness according to the change of grinding pressure. The dynamic buffer module is located between the drive shaft and the grinding head connection seat. It includes a buffer cylinder, a buffer piston, and an elastic adjustment component. The buffer cylinder is fixedly connected to the drive shaft, and the buffer piston is fixedly connected to the grinding head connection seat. The buffer piston extends into the buffer cylinder to form a sealed cavity, ensuring that the initial pressure of the sealed cavity is standard atmospheric pressure. The elastic adjustment component is located in the sealed cavity, and the coil lead is connected to the current drive unit of the central control module to dynamically adjust the buffer stiffness according to the change of grinding pressure. When the grinding head is not in contact with the wafer, the initial position of the displacement sensor is recorded, 0A current is input to the excitation coil, and the initial stiffness of the elastic body is calibrated through a static loading experiment to ensure that the piston does not deviate under no pressure. The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module; the displacement sensor synchronously collects the real-time position of the piston and calculates the piston displacement by combining it with the initial position. If the pressure deviation is greater than the preset deviation threshold and the piston displacement is less than the displacement threshold, the stiffness adjustment process is initiated; if the piston displacement is greater than or equal to the displacement threshold, the servo motor pressure compensation is directly triggered to avoid excessive piston displacement. The pressure deviation is converted into an impact load by combining it with the effective piston area. To ensure that the piston displacement does not exceed the limit under the impact load, the target stiffness must satisfy the load-displacement constraint relationship. Combining the initial stiffness of the elastic body, the final total target stiffness to be output is calculated using the following formula:

[0028] In the formula, It is the overall target stiffness. It is the initial stiffness of the elastic body. It's a pressure deviation. It is the effective area of ​​the piston. Displacement threshold; When the total target stiffness calculated by the formula exceeds the upper limit of the adjustable range of the elastic body stiffness, the servo motor performs pressure compensation.

[0029] It should be noted that when the displacement is close to the displacement threshold, the damping stiffness is increased first to suppress it; when the damping adjustment cannot meet the displacement constraint, the servo motor performs pressure compensation, and the central control module adjusts the output torque of the servo motor and the opening of the pressure regulating valve.

[0030] The hydraulic supply module includes a hydraulic pump, a relief valve, a pressure regulating valve, an accumulator, and an oil pressure sensor. The hydraulic pump is connected to the static pressure chamber through the main oil circuit. The relief valve is connected in parallel to the main oil circuit to stabilize the system oil pressure. The pressure regulating valve is used to regulate the oil pressure input to the static pressure chamber. The accumulator is used to absorb pressure pulsations in the hydraulic system. The oil pressure sensor detects the oil pressure in the main oil circuit in real time and feeds it back to the central control module. The central control module issues a start command, the hydraulic pump starts, the relief valve opens, the pressure regulating valve receives the initial command and sets the opening degree to 50%, the pressurized oil enters the static pressure oil chamber, and a static pressure oil film is initially established. The oil pressure sensor detects the main oil circuit oil pressure in real time and obtains the effective value after filtering high-frequency noise. The hydraulic pump output oil pressure has periodic pulsations (pulsation rate ≤ ±0.5MPa). The accumulator absorbs the pulsations through the expansion and contraction of the bladder. After the accumulator stabilizes the pressure, the main oil circuit oil pressure pulsation is ≤ ±0.05MPa, ensuring the stability of the static pressure oil film thickness.

[0031] The central control module receives detection signals from the pressure sensor and the oil pressure sensor. Based on the deviation between the preset grinding pressure and the actual grinding pressure, it adjusts the output torque of the servo motor and the opening of the pressure regulating valve, while controlling the buffer stiffness of the elastic adjustment component to achieve coordinated control of pressure and vibration.

[0032] The central control module is electrically connected to the servo motor, pressure sensor, pressure regulating valve, and elastic adjustment component. The process of adjusting the servo motor output torque and the pressure regulating valve opening based on the deviation between the preset grinding pressure and the actual grinding pressure is as follows: The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module. The PID calculation unit built into the central control module performs proportional (P), integral (I), and derivative (D) calculations on the deviation signal. Proportional component: directly affects the current deviation enlarge The rapid response pressure deviation is calculated using the following formula: ; Integration stage: The deviation signal is integrated from system startup time 0 to the current time t, and then multiplied by a coefficient. This is used to eliminate static pressure error, and the formula is: ; Differential element: the rate of change of the deviation signal Perform the calculation, multiply by the coefficient It is used to predict pressure change trends and suppress pressure overshoot. The formula is: ; The results of the above three steps are summed to obtain the total PID control output. Its physical meaning is "the amount of control voltage adjustment to be applied", with the unit being V, and the formula is as follows: ; In the formula, For voltage adjustment amount, It is the deviation amplification ratio factor. It's a pressure deviation. It is the integration time constant. It is the differential time constant.

[0033] Obtain the maximum output torque of the servo motor, and control the maximum output voltage and maximum opening. The voltage adjustment is converted into the servo motor torque adjustment using a linear proportional conversion formula. The formula is: In the formula This is the maximum torque of the servo motor. To control the maximum output voltage; The grinding pressure is directly corrected by adjusting the torque to change the drive shaft feed speed. It is a positive value. A positive value indicates that the motor torque needs to be increased, the drive shaft feed speed needs to be increased, and the grinding pressure needs to be increased. like It is a negative value. A negative value indicates that the motor torque needs to be reduced, the drive shaft feed speed needs to be slowed down, and the grinding pressure needs to be reduced.

[0034] Similarly, a linear proportional conversion formula is used to convert the voltage adjustment amount into the opening adjustment amount. The pressure regulating valve opening adjustment amount is In the formula To adjust the maximum opening of the valve, By adjusting the oil pressure to change the stiffness of the composite oil film, pressure fluctuations can be indirectly suppressed. It is a positive value. A positive value indicates that the valve opening needs to be increased, which raises the oil pressure entering the hydrostatic chamber and improves the stiffness of the composite oil film; if... It is a negative value. A negative value indicates that the opening of the regulating valve needs to be reduced, the oil pressure entering the static pressure oil chamber decreases, and the stiffness of the composite oil film decreases.

[0035] The process of controlling the buffer stiffness of the elastic adjustment component is as follows: Based on the current-stiffness linear response characteristics of electromagnetic rheoelastic bodies, the required excitation current is deduced from the total target stiffness using the following formula:

[0036] In the formula, for The target current of the excitation coil at any given time. It is the overall target stiffness. It is the initial stiffness of the elastic body. It is the current-stiffness linearity coefficient.

[0037] It should be noted that the central control module outputs a corresponding current signal to drive the excitation coil to generate a magnetic field. The density of the ferromagnetic particle chain inside the electromagnetic rheo-elastic body increases with the increase of current, and the stiffness is simultaneously increased to the target value, thus achieving rapid absorption of impact loads.

[0038] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0039] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0040] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0041] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0042] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0043] In conclusion, 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 servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding, characterized in that, It includes the main body of the servo electric cylinder, the composite bearing support module, the pressure detection module, the dynamic buffer module, the hydraulic supply module, and the central control module; The main body of the servo electric cylinder includes a servo motor, a ball screw, a drive shaft, and a grinding head connecting seat; The composite bearing support module provides support for the drive shaft, including a bearing housing, a hydrodynamic bearing assembly, and a hydrostatic bearing assembly. The hydrodynamic bearing assembly and the hydrostatic bearing assembly are arranged alternately in the axial direction within the bearing housing bore to form an integrated composite support structure. The pressure detection module is used to detect the actual grinding pressure of the grinding head in real time; The dynamic buffer module includes a buffer cylinder, a buffer piston, and an elastic adjustment component. The elastic adjustment component is disposed in a sealed cavity and is used to dynamically adjust the buffer stiffness according to the change of grinding pressure. The hydraulic supply module includes a hydraulic pump, a relief valve, a pressure regulating valve, an accumulator, and an oil pressure sensor. The oil pressure sensor detects the main oil circuit pressure in real time and feeds it back to the central control module. The central control module is used to adjust the output torque of the servo motor and the opening of the pressure regulating valve according to the deviation between the preset grinding pressure and the actual grinding pressure, while controlling the buffer stiffness of the elastic adjustment component to achieve coordinated control of pressure and vibration.

2. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 1, characterized in that, The servo motor drives the drive shaft to perform linear reciprocating motion via a ball screw. The end of the drive shaft is connected to the wafer grinding head via a grinding head connector to transmit stable grinding pressure to the grinding head.

3. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 2, characterized in that, An annular gap is formed between the inner hole of the bearing housing and the drive shaft, which serves as an oil film accommodating cavity. The hydrodynamic bearing assembly includes multiple hydrodynamic oil grooves evenly opened along the circumference of the inner hole of the bearing housing. The hydrodynamic oil grooves adopt a bidirectional spiral groove structure to ensure that a stable hydrodynamic effect can be generated during the extension and retraction of the drive shaft. The hydrostatic bearing assembly includes multiple hydrostatic oil chambers evenly spaced along the circumference of the bearing housing's inner hole. These hydrostatic oil chambers are connected to the hydraulic supply module via oil circuits to generate a stable hydrostatic effect.

4. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 3, characterized in that, The process of real-time detection of the actual grinding pressure of the grinding head is as follows: During the grinding process, the pressure generated by the contact between the grinding head and the wafer directly acts on the sensor detection surface, and the piezoelectric sensor converts the pressure signal into a corresponding weak voltage signal. The weak voltage signal is transmitted to the signal conditioning module via a shielded cable and preprocessed sequentially. The preprocessed digital pressure signal is transmitted to the central control module. After receiving the signal, the control module substitutes it into the preset linear calibration formula, subtracts the zero-point offset voltage, and calculates the actual grinding pressure. Based on the preset temperature compensation coefficient and the real-time data from the built-in temperature sensor of the connector, the pressure value is temperature compensated to obtain the actual grinding pressure after temperature compensation. The actual grinding pressure after temperature compensation is then transmitted to the central control module for verification.

5. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 4, characterized in that, The actual grinding pressure, after temperature compensation, is transmitted to the central control module for verification. The process is as follows: The actual grinding pressure after temperature compensation is transmitted to the central control module. The central control module compares the pressure values ​​of two adjacent acquisitions in real time, calculates the pressure fluctuation, and if the pressure fluctuation is greater than the preset threshold, it is judged as an abnormal fluctuation, the data set is immediately marked and a second acquisition verification is initiated. If abnormal fluctuations are observed in three consecutive data acquisitions, or if the pressure value exceeds the preset safety range, the central control module will immediately issue an alarm signal and suspend the grinding process to avoid wafer damage or equipment failure. Abnormal pressure data will be recorded simultaneously for subsequent process optimization and troubleshooting.

6. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 5, characterized in that, The dynamic buffer module is located between the drive shaft and the grinding head connecting seat, and includes a buffer cylinder, a buffer piston, and an elastic adjustment component. The buffer cylinder is fixedly connected to the drive shaft, and the buffer piston is fixedly connected to the grinding head connecting seat. The buffer piston extends into the buffer cylinder to form a sealed cavity, ensuring that the initial pressure of the sealed cavity is standard atmospheric pressure. The elastic adjustment component is located in the sealed cavity, and the coil lead is connected to the current drive unit of the central control module to dynamically adjust the buffer stiffness according to the change of grinding pressure.

7. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 6, characterized in that, The process of dynamically adjusting the buffer stiffness according to changes in grinding pressure is as follows: When the grinding head is not in contact with the wafer, the initial position of the displacement sensor is recorded, 0A current is input to the excitation coil, and the initial stiffness of the elastic body is calibrated through a static loading experiment to ensure that the piston does not deviate under no pressure. The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module. The displacement sensor synchronously collects the real-time position of the piston and calculates the piston displacement by combining it with the initial position. If the pressure deviation is greater than the preset deviation threshold and the piston displacement is less than the displacement threshold, the stiffness adjustment process will be initiated. The pressure deviation is converted into an impact load by combining it with the effective piston area. To ensure that the piston displacement does not exceed the limit under the impact load, the target stiffness must satisfy the load-displacement constraint relationship. Combining the initial stiffness of the elastic body, the final total target stiffness to be output is calculated using the following formula: ； In the formula, It is the overall target stiffness. It is the initial stiffness of the elastic body. It's a pressure deviation. It is the effective area of ​​the piston. Displacement threshold; When the total target stiffness calculated by the formula exceeds the upper limit of the adjustable range of the elastic body stiffness, that is, when the buffer adjustment cannot meet the displacement constraint, the servo motor performs pressure compensation.

8. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 7, characterized in that, Based on the deviation between the preset grinding pressure and the actual grinding pressure, adjust the output torque of the servo motor and the opening of the pressure regulating valve, as follows: The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module. The voltage adjustment is calculated using a PID algorithm. Obtain the maximum output torque of the servo motor, and control the maximum output voltage and maximum opening. A linear proportional conversion formula is used to convert the voltage adjustment amount into the servo motor torque adjustment amount and the opening adjustment amount, thereby adjusting the servo motor output torque and the opening of the pressure regulating valve.

9. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 8, characterized in that, The process of calculating the voltage adjustment using the PID algorithm is as follows: The pressure deviation is obtained by subtracting the preset grinding pressure from the actual grinding pressure output in real time by the pressure detection module. The PID calculation unit built into the central control module performs proportional, integral, and derivative calculations on the deviation signal. The results of the three stages of calculation are summed to obtain the total PID control output, as shown in the following formula: ； In the formula, This is the total control output. It is the deviation amplification ratio factor. It's a pressure deviation. It is the integration time constant. It is the differential time constant.

10. The servo electric cylinder drive pressure control and buffering system for semiconductor wafer grinding according to claim 9, characterized in that, The process of controlling the buffer stiffness of the elastic adjustment component is as follows: Based on the current-stiffness linear response characteristics of electromagnetic rheoelastic bodies, the required excitation current is deduced from the total target stiffness using the following formula: ； In the formula, for The target current of the excitation coil at any given time. It is the overall target stiffness. It is the initial stiffness of the elastic body. It is the current-stiffness linearity coefficient.

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