Integrated predictive correction synchronous compensation low-station wafer under-lid SMIF system

Abstract

The application relates to the technical field of semiconductor wafer transmission equipment, in particular to a low-station wafer uncovering SMIF system integrated with predictive correction and synchronous compensation. The system is composed of a SMIF structure body, a bottom uncovering motion mechanism, a small-stroke transmission system and a general control module integrated with three types of control submodules; the uncovering synchronous control submodule is fused with generalized predictive control, a Luenberger observer and online learning, and can correct the synchronous deviation of a 6-inch wafer box uncovering descending double shaft in advance; the dynamic compensation control submodule adopts a fractional order PID combined with adaptive feedforward, and can suppress temperature and load multi-type disturbances in the cavity in layers; the wafer positioning mapping submodule collects the wafer edge through upper and lower symmetrical laser displacement sensors, and accurately solves the 6-inch wafer center coordinates in combination with extended Kalman filtering. The application can be adapted to compact low-station process production lines such as 6-inch wafer ALD and CMP.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer transport equipment technology, specifically to a low-position wafer under-covering SMIF system with integrated predictive correction and synchronous compensation. It can be adapted to 6-inch wafer cassettes and complete wafer under-covering and high-precision alignment operations in extremely limited low-position scenarios with vertical installation space of less than 50cm. It is suitable for low-position process production lines for small semiconductor chips, discrete devices, ALD, thin film deposition, etc. Background Technology

[0002] In the manufacturing process of small-sized semiconductor chips, the transfer and temporary storage processes of 6-inch wafers are generally equipped with SMIF (Standard Mechanical Interface) systems. The SMIF system relies on a sealed clean chamber to complete the sealing and opening of the wafer cassette and the precise picking and placing of wafers, preventing particulate contaminants from the outside atmosphere from adhering to the wafer surface. It is a core supporting equipment for ensuring process yield in the mass production processes of discrete devices, power chips, and small logic chips.

[0003] Currently, most SMIF equipment used in mass production adopts a top-opening structure, with the opening mechanism located above the wafer cassette. After considering the thickness of the mechanism body and the opening stroke, the overall vertical height of the machine is generally greater than 1.2m, making it unsuitable for low-station process equipment where the vertical distance between the wafer pick-and-place reference surface and the rack mounting base is ≤50cm. This type of low-station equipment is mostly used for compact process stations such as atomic layer deposition, chemical mechanical cleaning, extreme ultraviolet pre-alignment, and thin film deposition for 6-inch wafers. The overall miniaturization design of the equipment requires a significant reduction in the vertical assembly space of the wafer transport mechanism, which traditional top-opening SMIFs cannot meet.

[0004] To adapt to the limited installation space in low-position wafer handling areas, the industry is gradually developing wafer-side openable SMIF (Surface Mount Integrated Injection) solutions. Existing patents such as CN209374411U and CN117448778A only disclose a vacuum chamber top cover lifting mechanism, which only enables the opening and closing of the process chamber and lacks wafer box opening and lifting coordination control functions. CN121115430A discloses a side-lever unlocking SMIF, but it still does not adopt a bottom-opening structure. None of the aforementioned prior art documents disclose a bottom three-stage gear lever transmission configuration adapted to 6-inch wafer boxes, nor do they include supporting features such as opening axis-down axis coupling prediction and synchronization control, layered disturbance compensation, and dual-laser edge entity detection architecture. Therefore, they cannot solve core issues such as synchronization lag, thermal deformation positioning drift, and wafer alignment deviation in low-position wafer handling scenarios.

[0005] Even if some existing wafer under-cover technology is implemented, there are still three major industrialization defects for transporting 6-inch small wafer cassettes.

[0006] 1. Only fixed timing open-loop control is used, and no motion prediction model adapted to the opening angle-downward displacement coupling of the 6-inch wafer cell is established. The asynchronous synchronous motion can easily cause the cover to scratch the 6-inch wafer, resulting in particulate contamination or even wafer fragments.

[0007] 2. Without a layered dynamic error compensation system, the temperature deformation of the telescopic rod and vertical guide rod inside the narrow cavity is superimposed with the wafer loading fluctuation, which continuously amplifies the positioning deviation of the 6-inch wafer pick-and-place.

[0008] 3. Relying solely on servo encoders to indirectly estimate wafer positions, without using symmetrically arranged laser displacement sensors to directly capture the upper and lower edges of the 6-inch wafer, makes it impossible to fully fit the wafer contour and compensate for the warping of the 6-inch wafer itself and the alignment offset caused by the processing and assembly tolerances of the small wafer box.

[0009] Therefore, there is an urgent need in this field for a bottom-opening SMIF system with a vertical assembly thickness of ≤50cm, designed specifically for 6-inch wafer cassettes, and integrating high-precision dual-axis synchronous control, multi-disturbance layer compensation, and direct wafer edge detection functions. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of existing top-opening devices, such as excessive vertical dimensions, general bottom-opening solutions not being adapted to 6-inch wafer cassettes, insufficient synchronization accuracy, lack of layered error compensation, and lack of direct wafer positioning. It provides a low-position wafer bottom-opening SMIF system with integrated predictive correction and synchronous compensation, which can complete the smooth and coordinated opening of 6-inch wafer cassettes and high-precision wafer loading and unloading in a narrow vertical cavity within 50cm.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: It provides a low-position wafer under-covering SMIF system with integrated predictive correction and synchronous compensation, comprising: an SMIF structure body, and further comprising: a bottom cover-opening motion mechanism for applying driving force from the bottom of the wafer cassette to execute the cover-opening action of the wafer cassette; a short-stroke transmission system, cooperating with the bottom cover-opening motion mechanism, to drive the wafer cassette downwards along a short vertical stroke; and a central control module, internally integrating a cover-opening synchronous control submodule, a dynamic compensation control submodule, and a wafer positioning mapping submodule for transmitting control signals to each other; the cover-opening synchronous control submodule is configured to: pre-store the nonlinear mapping relationship between the cover-opening angle and the downward distance of the wafer cassette and construct a corresponding motion prediction model. During the synchronous operation of the opening action and the wafer cassette descent, the measured values ​​of the opening angle and descent distance are collected in real time, and the dual-axis synchronization deviation is calculated with the theoretical values ​​output by the motion prediction model. When the dual-axis synchronization deviation is greater than a preset threshold, a speed adjustment command is output to the bottom opening motion mechanism and the short-stroke transmission system. The dynamic compensation control submodule is configured to: collect the position feedback signals and load sensing signals of each axis in real time, and output the displacement compensation amount to the bottom opening motion mechanism and the short-stroke transmission system. The wafer positioning mapping submodule is configured to: collect wafer edge scanning data and calculate the wafer center coordinates when the wafer cassette descents to the preset position, and output a position fine-tuning command to the short-stroke transmission system based on the calculation results.

[0012] Furthermore, the lid-opening synchronization control submodule uses a generalized predictive control algorithm to construct a motion prediction model. The generalized predictive control algorithm pre-configures the prediction time domain and the control time domain, uses the coupling deviation of the lid-opening angle and the downward distance as performance evaluation indicators, and solves to obtain the optimal control law for the dual-axis motion. The generalized predictive control algorithm performs a rolling optimization operation, sets constraints on the deviation between the predicted output and the reference trajectory and the fluctuation amplitude of the control increment, and outputs the corresponding speed adjustment command for the dual axes based on the preset constraints.

[0013] Furthermore, the lid opening synchronization control submodule is equipped with a Luenberger state observer; the Luenberger state observer collects the position feedback signals and speed feedback signals of the lid opening axis and the downward axis, and performs real-time state observation of the unmodeled dynamic error of the dual-axis motion; when the detected dual-axis synchronization deviation exceeds the preset threshold, the Luenberger state observer outputs a state estimate based on the preset gain matrix, and generates a compensation torque command to correct the synchronization deviation based on the state estimate.

[0014] Furthermore, the lid opening synchronization control submodule is also equipped with an online learning mechanism, which is used to retrieve historical operating data of the equipment and iteratively update the model parameters corresponding to the nonlinear mapping relationship after each preset number of lid opening and downward cycles.

[0015] Furthermore, the dynamic compensation control submodule uses an improved fractional-order PID algorithm to calculate the displacement compensation amount. The improved fractional-order PID algorithm includes a proportional control term, an improved fractional-order integral operator, and an improved fractional-order differential operator. The improved fractional-order integral operator and the improved fractional-order differential operator are adapted and configured according to the overall load and mechanical deformation characteristics of the equipment.

[0016] Furthermore, the dynamic compensation control submodule integrates an adaptive feedforward compensation unit; the adaptive feedforward compensation unit constructs an inverse model of the motion system, and adopts a recursive least squares algorithm with a dynamic forgetting factor to identify the model parameters of the corresponding load disturbance and mechanical deformation online based on the disturbance signal generated by the operation of the equipment; the adaptive feedforward compensation unit generates a feedforward compensation amount, which is superimposed on the displacement compensation amount calculated by the improved fractional PID algorithm.

[0017] Furthermore, the wafer positioning and mapping submodule includes two laser displacement sensors arranged symmetrically at the top and bottom to synchronously emit detection beams to collect scanning data of the upper and lower edges of the wafer. The wafer positioning and mapping submodule uses an extended Kalman filter algorithm to denoise the scanning data of the upper and lower edges of the wafer, and fits the wafer contour based on the denoised upper and lower edge scanning data to calculate the wafer center coordinates.

[0018] Furthermore, the bottom opening mechanism is a three-stage gear lever transmission mechanism; the three-stage gear lever transmission mechanism includes a first servo motor, a main drive gear, an intermediate transmission gear, a lever execution gear, and a lever. The main drive gear, intermediate transmission gear, and lever execution gear mesh sequentially. The first servo motor drives the lever to complete the swinging action through the sequentially meshing gears. The top of the lever extends directly into the arc-shaped guide groove at the bottom of the wafer box for transmission, and the box lid is opened by applying force from the bottom.

[0019] Furthermore, the short-stroke transmission system includes a second servo motor, a telescopic rod, a support frame, a bracket, and a vertical guide rod. The vertical guide rod and the bracket are both fixed inside the SMIF structure body. The output end of the second servo motor is connected to the telescopic rod. The top of the telescopic rod is fixed to the support frame, and a loading platform for supporting the wafer cassette after opening is provided on the support frame. The bracket is fixed to the side wall of the support frame and slidably fitted outside the vertical guide rod. The vertical guide rod restricts the support frame to only produce vertical displacement. The second servo motor drives the telescopic rod to perform vertical telescopic movement, driving the support frame to achieve vertical short-stroke transport of the wafer cassette after opening along the vertical guide rod.

[0020] Furthermore, the short-stroke transmission system is also equipped with an absolute grating ruler, which is used to acquire the vertical position signal of the support frame in real time. The vertical position signal output by the absolute grating ruler is corrected by a thermal deformation error compensation algorithm.

[0021] Compared with the prior art, the present invention has the following beneficial effects.

[0022] 1. A predictive and corrective integrated dual-axis synchronous control architecture adapted to 6-inch wafer cassettes is constructed. A nonlinear motion prediction model is pre-established for the opening angle and the downward distance of the cassette. This architecture integrates generalized predictive control, a Luenberger state observer, and an online learning mechanism to collaboratively manage the dual-axis linkage process. It can compensate for motion synchronization lag issues in advance and adapt to different 6-inch wafer loading conditions. Compared to traditional fixed-timing open-loop control methods, this architecture improves the accuracy of dual-axis linkage synchronous control and reduces the process risk of the cassette cover scratching the wafer during the opening process.

[0023] 2. An improved fractional-order PID and adaptive feedforward composite compensation system adapted to the confined cavity was constructed. The adaptive feedforward unit can identify two types of disturbances online: wafer loading fluctuations and thermal deformation of the rods. Combined with the fractional-order PID output fusion compensation signal matched to the dynamic characteristics of the small transmission mechanism, this system can simultaneously suppress positioning offsets and mechanical resonances caused by various disturbances, ensuring the positioning stability of 6-inch wafers during long-term continuous transport.

[0024] 3. A dual-laser displacement sensor system, symmetrically arranged vertically, synchronously acquires data from both edges of the 6-inch wafer. Utilizing an extended Kalman filter algorithm, it fits the complete wafer contour, effectively offsetting alignment deviations caused by small wafer cassette processing and assembly tolerances, as well as the warping deformation of the 6-inch wafer itself. Compared to traditional positioning schemes relying solely on single-point acquisition, this solution significantly improves the accuracy of determining the wafer's geometric center coordinates. It eliminates the need for an additional independent wafer lateral translation actuator, reducing the number of mechanical parts and optimizing the internal layout of the equipment.

[0025] 4. A compact three-stage gear bottom-opening mechanism is adopted, equipped with an absolute optical encoder. The absolute optical encoder can directly acquire thermal deformation displacement signals during the machine's operation, eliminating the need for the redundant structure of traditional double-layer shaft-end sensors. It can distinguish between two types of positional error sources: temperature drift and transmission backlash. Compared to traditional top-opening SMIF equipment, this mechanism occupies less vertical space, meeting the assembly size limitations of low-position equipment.

[0026] 5. The integrated control module combines three functional sub-modules: synchronous control, disturbance compensation, and wafer positioning. Its internal control algorithms and motion calibration models are adapted to the 6-inch wafer cassette design, eliminating the need for multi-specification wafer switching programs. It can be matched with various compact, low-station 6-inch wafer production lines, such as CMP cleaning, atomic layer deposition, EUV pre-alignment, and thin film deposition, reducing periodic manual calibration work during equipment commissioning and maintenance, and saving manpower and time for production line maintenance. Attached Figure Description

[0027] Figure 1 This is a front view of the low-position wafer undercap SMIF system integrating predictive correction and synchronous compensation according to the present invention.

[0028] Figure 2 This is a top view of the low-position wafer undercap SMIF system with integrated predictive correction and synchronous compensation according to the present invention.

[0029] Figure 3 This is a top view of the bottom opening mechanism of the present invention.

[0030] Figure 4 This is a schematic diagram of the internal structure of the low-position wafer undercap SMIF system with integrated predictive correction and synchronous compensation according to the present invention.

[0031] Figure 5 This is a structural block diagram of the overall control module of the present invention.

[0032] Reference numerals in the attached drawings: SMIF structure body 1, lever 2, first servo motor 3, main drive gear 4, intermediate transmission gear 5, lever actuation gear 6, cavity 7, second servo motor 8, telescopic rod 9, support frame 10, bracket 11, vertical guide rod 12, main control module 13, grating reading head 14, absolute grating ruler 15, laser displacement sensor 16, loading platform 17. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] Reference Appendix Figure 1-4 This invention provides a low-position wafer under-cap opening SMIF system with integrated predictive correction and synchronous compensation. The invention comprises an SMIF structure body 1, with the bottom cap opening motion mechanism, short-stroke transmission system, and main control module 13 all assembled and fixed inside the SMIF structure body 1. Spatially, the bottom cap opening motion mechanism is located on the inner bottom of the SMIF structure body 1, the short-stroke transmission system is vertically centered, and the main control module 13 is integrated into the electrical control box at the bottom of the SMIF structure body 1. The SMIF structure body 1 is used to complete the limiting and spatial arrangement of each component. The system as a whole consists of three main parts: the bottom cap opening motion mechanism, the short-stroke transmission system, and the main control module 13. The entire system is adaptable to 6-inch wafer cassette transport operations.

[0035] Reference Appendix Figure 3The bottom opening mechanism employs a three-stage gear and lever transmission structure, consisting of a first servo motor 3, a main drive gear 4, an intermediate transmission gear 5, a lever execution gear 6, and lever 2. The gears mesh sequentially, and the first servo motor 3 drives the lever 2 to reciprocate. The gap between the top of lever 2 and the R4 arc-shaped guide groove at the bottom of the 6-inch wafer cassette is controlled within 0.02–0.05 mm, ensuring a snug, slip-free transmission. All gears and lever tips are coated with a dust-free, anti-chip coating, suitable for the process environment of cavity 7. Nitrogen gas is continuously introduced into the cavity to maintain internal cleanliness and positive pressure, preventing dust contamination of the 6-inch wafer.

[0036] The short-stroke transmission system is arranged vertically along the SMIF structure body 1, and relies on the telescopic rod to drive the support frame and loading platform to lift and lower the 6-inch wafer box vertically. The main control module 13 is arranged in the electrical control box at the bottom of the SMIF structure body 1, and establishes wired signal transmission with the first servo motor 3, the second servo motor 8, the absolute grating ruler 15, and the laser displacement sensor 16 respectively.

[0037] Reference Appendix Figure 4 The power source for the short-stroke transmission system is the second servo motor 8, which is vertically fixed inside the SMIF structure body 1. The output end of the second servo motor 8 forms a transmission connection with the bottom end of the telescopic rod 9. The top end of the telescopic rod 9 can be rigidly connected to the bottom surface of the support frame 10 through a flange. The support frame 10 is equipped with a loading platform 17 for placing 6-inch wafer cassettes. The side wall of the support frame 10 is fixed with a bracket 11 by anti-loosening bolts. The bracket 11 is slidably fitted onto the outside of two parallel vertical guide rods 12. The upper and lower ends of the vertical guide rods 12 are fixed to the upper and lower mounting seats of the SMIF structure body 1 through locking flanges. The vertical guide rods 12 restrict the support frame 10 to only produce vertical displacement, and there is no lateral offset throughout the entire movement.

[0038] Reference Appendix Figure 4 The short-stroke transmission system is also equipped with an absolute grating ruler 15 for position acquisition. The grating ruler is vertically locked to the side wall inside the SMIF structure body 1. The grating reading head 14 is rigidly connected to the support frame 10 through anti-loosening bolts, which can directly acquire the overall vertical displacement of the support frame 10, reflecting the thermal deformation of the telescopic rod 9 and the vertical guide rod 12 caused by temperature changes. The SMIF structure body 1 is also equipped with three PT100 temperature sensing elements, which are respectively installed on the upper and lower mounting seats of the single vertical guide rod 12 and the base at the bottom of the equipment. The main control module 13 has a built-in thermal deformation error compensation algorithm. The system completes multi-step temperature calibration before leaving the factory and generates a temperature-thermal displacement mapping data table. It can synchronously read multiple temperature sampling signals at a fixed 10ms cycle, use a linear interpolation algorithm to correct the original grating reading, separate the measurement error caused by temperature drift, and output the corrected true vertical displacement. Long-term operation suppresses the cumulative temperature positioning deviation.

[0039] Reference Appendix Figure 5The main control module 13 has a built-in cover opening synchronization control submodule, dynamic compensation control submodule, and wafer positioning mapping submodule. The three types of submodules interact with control signals in real time to complete the entire process of dual-axis synchronous control, disturbance compensation, and wafer coordinate detection. After the system is powered on and initialized, the main control module loads a motion prediction model (i.e., a motion prediction model coupled with cover opening angle and downward displacement) specifically fitted to a 6-inch wafer cell as a reference for coordinated motion.

[0040] The lid-opening synchronization control submodule incorporates three types of program units: a generalized predictive control algorithm, a Luenberger state observer, and an online learning mechanism. After the system starts the synchronized lid-opening process, the lid-opening synchronization control submodule synchronously collects the measured values ​​of the lid-opening axis angle and the short-stroke downward axis displacement. It then inputs the two sets of measured values ​​into a pre-built motion prediction model, which outputs the standard theoretical angle and theoretical displacement corresponding to the current working condition. By comparing the difference between the measured values ​​and the theoretical values, the real-time dual-axis synchronization deviation is calculated.

[0041] The system pre-sets a synchronization deviation threshold (e.g., a threshold value of 0.02 mm). When the real-time synchronization deviation does not exceed the threshold, the cover-opening synchronization control submodule directly outputs small speed adjustment commands to the first servo motor 3 and the second servo motor 8 to complete flexible synchronization correction. If the synchronization deviation exceeds the threshold, the Luenberger observer is automatically activated to participate in the control. The gain matrix of the Luenberger observer is solved using the pole placement method. The closed-loop pole placement range of the system is [-100, -30]. The observation response speed precedes the motion deviation generation rate caused by gear and rod transmission. The system collects dual-axis position and speed signals in real time to identify unmodeled dynamic errors and outputs compensation torque commands to quickly converge the synchronization deviation, avoiding the risk of scratches when opening the 6-inch wafer cell.

[0042] The system is also equipped with a periodic online learning mechanism. For example, after 800 complete cycles of opening and descending the 6-inch wafer cell, it automatically retrieves all historical running data, refits the nonlinear mapping relationship, iteratively updates the model parameters, and compensates for model mismatch caused by gear wear and the expansion of the gap of the vertical guide rod 12 without stopping the machine for manual adjustment. If the parameter iteration convergence threshold is set to 0.001, the update stops when the difference between adjacent iteration parameters is less than the threshold, reducing the total control computing power consumption.

[0043] The generalized predictive control algorithm pre-divides the prediction time domain and the control time domain. For example, the system presets the trajectory deviation constraint range to ±0.02mm, and simultaneously limits the motion control increment amplitude. Specifically, the control increment amplitude for the cover opening axis is ±0.5rad / s, and the control increment amplitude for the downlink axis is ±0.1mm / s. 2Rolling optimization is performed in each discrete sampling period. If the calculation result exceeds the constraint range, a limiting speed command is output to avoid vibration and fragmentation of the 6-inch thin wafer due to sudden servo shock.

[0044] The dynamic compensation control submodule is divided into two independent operation branches: an improved fractional-order PID calculation unit and an adaptive feedforward compensation unit. The two compensation quantities are fused by fuzzy arbitration and then uniformly sent to the first servo motor 3 and the second servo motor 8 for correction.

[0045] The improved fractional-order PID algorithm integrates a proportional control term, an adjustable fractional-order integral operator, and an adjustable fractional-order derivative operator. These two types of fractional operators can independently match parameters for 6-inch wafers under no-load, full-load, and high / low temperature deformation conditions. The algorithm uses an Oustaloup filter to perform discrete approximation of the fractional operators, unlike idealized integer-order PID. It accurately captures the inherent fractional-order dynamic hysteresis and micro-deformation characteristics of the small gear and telescopic rod transmission system of this equipment, significantly reducing the residual positioning error of 6-inch wafers. Its advantages are fourfold: First, it synchronously suppresses multiple complex disturbances such as resonance, temperature drift, and sudden changes in 6-inch wafer loading; the fractional-order derivative quickly suppresses instantaneous impacts, and the fractional-order integral smoothly mitigates long-term thermal accumulation drift. Second, the integral and derivative terms are independently adjustable, eliminating the need for frequent manual tuning. Third, it exhibits excellent integral convergence performance in long-term mass production, continuously suppressing the cumulative positioning drift caused by continuous operation of the small feed box. Fourth, it matches the narrow nitrogen-cleaned chamber transmission layout of this equipment, weakening the gear meshing resonance peak and reducing the positioning fluctuation range.

[0046] An adaptive feedforward compensation unit constructs a second-order inverse model of the motion system adapted to 6-inch devices. This model is used to calculate the equivalent mechanism's rotational inertia and damping characteristics. It receives servo speed and acceleration commands and outputs disturbance cancellation feedforward components. This adaptive feedforward compensation unit incorporates a recursive least squares algorithm with a dynamically adjustable forgetting factor. It collects load and PT100 temperature signals in real time, identifies dynamic parameters corresponding to changes in 6-inch wafer loading, thermal elongation of components, and gear clearance fluctuations online, and updates the inverse model in real time. The forgetting factor ranges from 0.95 to 0.99. The system adaptively adjusts the forgetting factor based on the intensity of real-time disturbances. During severe disturbances, the forgetting factor is reduced, and the weight of real-time data is increased; during steady-state small disturbances, the forgetting factor is increased, and long-term operating data is retained. The recursive least squares algorithm performs three iterative operations in each sampling cycle: parameter estimation, gain calculation, and covariance update. After the parameter update is completed, the current motion command is input into the inverse model to calculate the feedforward compensation amount.

[0047] This dynamic compensation control submodule also includes a fuzzy logic arbitrator as the decision layer for compensation quantity fusion. The fuzzy logic arbitrator takes three types of state variables as input: the absolute value of the tracking error, the rate of change of the error, and the degree of control saturation. All variables are divided into three fuzzy intervals (large, medium, and small) using Gaussian membership functions. These three types of variables combine to form 27 sets of standardized inference rules (a typical rule example: when the tracking error is large and the error change is medium, the weighting coefficient is 0.7), with the weighting coefficient ranging from 0 to 1. Under high-disturbance conditions, the feedforward compensation weight is increased; under steady-state conditions, fractional-order PID closed-loop correction is the primary method. The fused total displacement compensation is layered to offset various measurable disturbances such as temperature, load, and resonance, as well as inherent residual errors in the system, fundamentally solving the positioning drift problem in the long-term continuous transport of 6-inch wafers. The initial values ​​of the process noise and measurement noise covariance matrices are pre-calibrated before shipment for filtering iteration calculations.

[0048] Reference Appendix Figure 4 The wafer positioning and mapping submodule is equipped with two laser displacement sensors arranged symmetrically vertically. These two laser displacement sensors are fixed inside cavity 7 on the SMIF structure body 1. The two laser displacement sensors synchronously emit detection beams to collect scanning data from the upper and lower edges of the 6-inch wafer, respectively. The two laser displacement sensors share the same synchronous sampling clock, eliminating data offset caused by multi-channel timing differences. This wafer positioning and mapping submodule incorporates an extended Kalman filter algorithm, cyclically performing two main computational stages—state prediction and measurement update—in each sampling cycle.

[0049] During the state prediction phase, the horizontal and vertical coordinates of the 6-inch wafer after correction in the previous cycle are retrieved. Based on the system state transition equation, the estimated coordinates of the wafer at the current sampling time that have not been corrected by the sensor are deduced. The corresponding error covariance matrix is ​​updated synchronously, and the process noise caused by equipment transmission and ambient airflow is quantified through the matrix.

[0050] During the measurement update phase, the scanning data of the upper and lower edges of the 6-inch wafer, which are synchronously acquired by two sets of lasers, are imported. The Kalman gain is calculated to balance the weight of the predicted coordinates and the actual measured data. The predicted coordinates are corrected by using the Kalman gain. The optimal geometric center coordinates of the 6-inch wafer are solved by integrating theoretical motion laws and actual measured information. The error covariance matrix corresponding to the corrected coordinates is updated synchronously. This filters out nonlinear noise caused by dust obstruction, servo start-stop impact, and airflow in the cavity, and eliminates invalid interference sampling points in the point cloud.

[0051] After the filtering operation is completed, the wafer positioning and mapping submodule fits the complete wafer outline based on the scan data of the upper and lower edges of the 6-inch wafer after noise reduction, and calculates the true center coordinates of the wafer. The difference between the measured center coordinates and the 6-inch standard process reference coordinates stored in the equipment is calculated to calculate the vertical height offset of the wafer, and the corresponding fine adjustment command is output to the second servo motor 8 to drive the telescopic rod 9 to move the support frame 10 vertically up and down, compensate for the height deviation, eliminate the robot arm alignment offset caused by the warping of the 6-inch wafer itself and the assembly tolerance of the small 6-inch wafer box positioning slot, and provide a precise spatial positioning reference for the 6-inch wafer picking process.

[0052] The present invention will now be described in detail with reference to specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of protection. The technical features in the embodiments can be combined with each other.

[0053] This embodiment is specifically designed for atomic layer deposition low-station process equipment for 6-inch wafer cassettes. The vertical distance between the wafer pick-and-place reference surface and the rack mounting bottom surface is 40cm, and the vertical assembly size of the whole machine is strictly limited. The mechanical structure, hardware selection, control parameters, and whole machine operation process adapted to 6-inch small wafer cassettes are described in detail below.

[0054] The power source for the bottom opening mechanism is a compact DC servo motor 3 with a rated torque of 0.28 N·m, arranged laterally to reduce vertical space occupation. The main drive gear 4 has a module of 0.6 and 18 teeth, the intermediate double transmission gear has 45 large teeth and 22 small teeth, and the lever actuation gear 6 has a module of 1.0 and 28 teeth. The entire gear transmission ratio matches the opening load characteristics of the 6-inch small wafer cassette. The top of the lever 2 is adapted to the R4mm arc-shaped guide groove at the bottom of the 6-inch wafer cassette, and the gap between the lever and the guide groove is 0.02~0.05mm, with no sliding friction. The maximum opening swing angle of the mechanism is 105°, and the time for a single complete opening action is 1.0s. The start-stop angular acceleration is reasonably matched to the protection requirements of the 6-inch thin wafer. Each gear is equipped with angular contact bearings to bear the composite load. A harmonic reducer and flexible coupling are added to the motor input end to buffer the start-stop impact, and the operating noise is less than 35dB.

[0055] The power component of the short-stroke transmission system is a high-precision second servo motor 8 with a rated power of 75W. The second servo motor 8 is vertically fixed to the inner side wall of the SMIF structure body 1, and its output end is connected to the telescopic rod 9. The top flange of the telescopic rod is rigidly connected to the support frame 10. The loading platform 17 on the support frame is specifically used to support the 6-inch wafer cassette. The side wall bracket of the support frame is slidably fitted onto the outside of a single vertical guide rod 12. The vertical guide rod has a diameter of 10mm and a UP precision level. The fluctuation of sliding friction is less than 5% throughout the entire stroke, and there is no crawling or jamming phenomenon.

[0056] Position and temperature measurement configuration: The absolute grating ruler 15 reading head is fixed to the side of the support frame 10 with anti-loosening, and the grating resolution is 0.2μm, directly acquiring the overall vertical displacement of the 6-inch wafer cell; the equipment is equipped with three PT100 temperature sensing elements, which are respectively installed on the upper and lower mounting seats of a single vertical guide rod and the bottom base of the equipment; the equipment is factory-calibrated with multi-step temperature, generating a dedicated 6-inch equipment temperature-thermal displacement mapping data table; the system has a fixed 10ms temperature sampling period, uses a linear interpolation algorithm to correct the original grating reading, and separates the temperature drift error, without the need for an additional drive encoder to assist in acquisition, and the thermally induced displacement drift can be controlled within 0.002mm in the full temperature range of 18℃~28℃.

[0057] The lid opening synchronization control submodule uses a digital signal processor as its computing core, with a system discrete sampling period of 0.4ms. The generalized predictive control configuration has 6 steps in the prediction time domain and 2 steps in the control time domain. The whole machine is calibrated with a dedicated motion prediction model for the lid opening angle-downward displacement coupling of the 6-inch wafer cell, and the theoretical synchronization error for the entire stroke is less than 0.01mm. It is equipped with a 300Hz bandwidth Luenberger state observer and uses the pole placement method to tune the gain matrix, which can predict the motion lag caused by gear backlash in advance and output compensation torque. The online learning mechanism automatically starts after every 800 complete 6-inch wafer cell lid opening and downward cycles, retrieves historical deviation datasets to iteratively update the mapping model, and the model correction amplitude is less than 0.3% after the equipment has accumulated one million runs, which greatly reduces the frequency of manual calibration.

[0058] The dynamic compensation control submodule uses an Oustaloup filter to achieve a fractional operator discrete approximation. The improved fractional integral order is 0.65 and the derivative order is 0.55. Compared with integer-order PID, it widens the system phase margin and suppresses the 120Hz resonance peak of the 6-inch small transmission mechanism. The forgetting factor of the adaptive feedforward unit is fixed at 0.97. Under the sudden change of 6-inch wafer loading from 0 to 25 wafers, the load dynamic parameters are identified within 7ms. After the feedforward compensation component and the fractional-order PID closed-loop output are fuzzy-weighted and fused, the total displacement compensation is synchronously sent to the first servo motor 3 and the second servo motor 8. This layered cancellation of various disturbances such as load changes, thermal deformation of rods, and mechanical resonance prevents the cumulative drift of 6-inch wafer positioning caused by long-term continuous operation.

[0059] The wafer positioning and mapping submodule is equipped with two sets of symmetrically arranged laser displacement sensors 16, with a laser wavelength of 650nm, a single-unit detection resolution of 0.1μm, and a scanning frequency of 10kHz. When the support frame carries the 6-inch wafer cassette down to the inspection station, the two sets of sensors synchronously emit detection beams to collect two-dimensional point clouds of the upper and lower edges of the 6-inch wafer, respectively. The two sets of sensors share a synchronous sampling clock to eliminate dual-channel timing deviation. The submodule has a built-in extended Kalman filter algorithm to filter out nonlinear noise caused by nitrogen dust in the cavity, circulating airflow, and servo start-stop vibration. Based on the noise-reduced point clouds of the two edges, the complete 6-inch wafer outline is fitted, and the wafer geometric center calculation accuracy is ±0.004mm. The difference between the measured wafer center and the 6-inch dedicated process benchmark is calculated to solve the vertical height offset and send fine-tuning instructions to the second servo motor. After the robot arm completes the pick-up and put-down action of the 6-inch wafer, the positioning error can be controlled within 0.006mm.

[0060] The complete operation process of the entire machine involved in this embodiment includes: In the standby state of the equipment, the 6-inch wafer cassette is placed on the loading platform 17 of the small stroke transmission system support frame, the bottom cover opening lever 2 is kept at zero position, and the top of the lever is in contact with the arc-shaped guide groove at the bottom of the 6-inch wafer cassette to complete the pre-positioning. After the equipment receives the wafer pick-up trigger command, the cover opening synchronous control submodule retrieves the motion prediction model of the 6-inch wafer cassette's exclusive cover opening angle-downward displacement coupling, and synchronously sends coordinated motion control commands to the first servo motor 3 and the second servo motor 8; during the entire operation of the equipment, the Luenberger observer identifies unmodeled dynamic errors such as gear transmission backlash in real time, and the dynamic compensation control submodule continuously outputs layered displacement compensation to offset various positioning disturbances caused by temperature deformation, 6-inch wafer load changes, and mechanical resonance.

[0061] Two sets of symmetrical laser displacement sensors are arranged inside the cavity 7 in the detection bracket. When the support frame carries the 6-inch wafer cassette down to the detection station, the bottom opening mechanism has fully opened the cassette cover, exposing the upper and lower edges of the 6-inch wafer completely without any cassette wall obstruction. The wafer positioning mapping submodule synchronously starts the laser sensors to collect the point cloud of the upper and lower edges of the wafer. After noise reduction by extended Kalman filtering, the complete outline of the wafer is fitted and the center coordinates are calculated. The vertical height offset is calculated, and a fine-tuning command is issued to correct the vertical height of the support frame. After the height correction is completed, the bottom opening motion mechanism and the small stroke transmission system continuously and synchronously feed to the robot arm pick-up and drop-off station. The geometry of the 6-inch wafer is precisely aligned with the preset process benchmark, and the external robot arm performs the wafer pick-up operation. After a single wafer pick-up operation is completed, the system generates a reverse collaborative motion trajectory. Two servo motors synchronously drive the mechanism to reset, the cassette cover to close, and the whole machine returns to the initial zero position, waiting for the next operation command.

[0062] The equipment monitors four key operating parameters in real time throughout the entire process: dual-axis synchronization deviation, laser displacement sensor signal status, cavity nitrogen ambient temperature, and servo load torque. When any fault is triggered, such as synchronization deviation exceeding limits, laser signal loss, temperature deviation of 18-28℃, or motor overload, the system immediately locks both servo motors and stores the fault log. After manual reset to zero, the system automatically verifies the synchronization deviation of the 6-inch wafer cassette's dedicated motion model. If the deviation exceeds the threshold, a single model parameter correction is performed. Only after the correction is completed can the system switch to automatic loop mode, effectively avoiding problems such as 6-inch thin wafer impacts, mechanism jamming, and motor overload damage.

[0063] In this embodiment, all mechanical dimensions, transmission ratios, control algorithms, and calibration models are designed specifically for 6-inch wafer cassettes, eliminating the need for pre-reserved parameters for multi-size switching. Only minor adjustments to servo power, gear parameters, and travel limits are required to adapt to other low-level processes such as chemical mechanical cleaning, extreme ultraviolet pre-alignment, and thin film deposition. The entire system operates stably for extended periods within a nitrogen-cleaned chamber at 18℃ to 28℃, relying on a thermal deformation compensation algorithm and fractional-order PID controller to suppress 6-inch wafer positioning offsets caused by temperature fluctuations.

[0064] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered within the scope of protection of the present invention.

Claims

1. A low-position wafer under-capping SMIF system integrating predictive correction and synchronous compensation, including: The SMIF structure body is characterized by further comprising: The bottom opening mechanism is used to apply driving force from the bottom of the wafer cassette to perform the opening action of the wafer cassette cover; The short-stroke transmission system, in conjunction with the bottom cover opening mechanism, drives the wafer cassette to descend vertically in a short stroke. The main control module integrates a cover opening synchronization control submodule, a dynamic compensation control submodule, and a wafer positioning mapping submodule for transmitting control signals to each other. The lid opening synchronization control submodule is configured as follows: pre-store the nonlinear mapping relationship between the lid opening angle and the wafer cell downward distance and construct the corresponding motion prediction model; during the synchronous operation phase of the lid opening action and the wafer cell downward movement, collect the measured values ​​of the lid opening angle and the downward distance in real time, and calculate the dual-axis synchronization deviation with the theoretical values ​​output by the motion prediction model; when the dual-axis synchronization deviation is greater than the preset threshold, output speed adjustment commands to the bottom lid opening motion mechanism and the small stroke transmission system. The dynamic compensation control submodule is configured to: collect position feedback signals and load sensing signals of each axis in real time, and output displacement compensation to the bottom cover opening motion mechanism and the small stroke transmission system. The wafer positioning and mapping submodule is configured to: collect wafer edge scanning data and calculate wafer center coordinates when the wafer cassette moves to a preset position, and output position fine-tuning instructions to the small-stroke transmission system based on the calculation results.

2. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 1, characterized in that, The lid-opening synchronization control submodule uses a generalized predictive control algorithm to construct a motion prediction model; The generalized predictive control algorithm pre-configures the prediction time domain and the control time domain, and uses the coupling deviation of the opening angle and the downward distance as performance evaluation indicators to solve for the optimal control law of dual-axis motion. The generalized predictive control algorithm performs a rolling optimization operation, sets constraints on the deviation between the predicted output and the reference trajectory and the fluctuation range of the control increment, and outputs speed adjustment commands corresponding to the two axes based on the preset constraints.

3. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 2, characterized in that, The lid opening synchronization control submodule is equipped with a Luenberger state observer. The Luenberger state observer collects position and velocity feedback signals from the opening axis and the downward axis to perform real-time state observation of the unmodeled dynamic error of the dual-axis motion. When the detected dual-axis synchronization deviation exceeds a preset threshold, the Luenberger state observer outputs a state estimate based on a preset gain matrix and generates a compensation torque command to correct the synchronization deviation based on the state estimate.

4. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 3, characterized in that, The lid-opening synchronization control submodule is also equipped with an online learning mechanism, which is used to retrieve historical operating data of the equipment and iteratively update the model parameters corresponding to the nonlinear mapping relationship after each preset number of lid-opening downward cycles.

5. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 3, characterized in that, The dynamic compensation control submodule uses an improved fractional-order PID algorithm to calculate the displacement compensation amount; The improved fractional-order PID algorithm includes a proportional control term, an improved fractional-order integral operator, and an improved fractional-order differential operator. The improved fractional-order integral operator and the improved fractional-order differential operator are adapted and configured according to the overall load and mechanical deformation characteristics of the equipment.

6. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 5, characterized in that, The dynamic compensation control submodule integrates an adaptive feedforward compensation unit. The adaptive feedforward compensation unit constructs an inverse model of the motion system. The adaptive feedforward compensation unit adopts a recursive least squares algorithm with a dynamic forgetting factor to identify the model parameters corresponding to load disturbance and mechanical deformation online based on the disturbance signal generated by the operation of the equipment. The adaptive feedforward compensation unit generates a feedforward compensation amount, which is then superimposed on the displacement compensation amount calculated by the improved fractional-order PID algorithm.

7. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 1, characterized in that, The wafer positioning and mapping submodule includes two laser displacement sensors arranged symmetrically at the top and bottom, which are used to synchronously emit detection beams to collect scanning data of the upper and lower edges of the wafer; The wafer positioning and mapping submodule uses an extended Kalman filter algorithm to denoise the scanning data of the upper and lower edges of the wafer, and fits the wafer contour based on the denoised upper and lower edge scanning data to calculate the wafer center coordinates.

8. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 1, characterized in that, The bottom opening mechanism is a three-stage gear lever transmission mechanism; The three-stage gear lever transmission mechanism includes a first servo motor, a main drive gear, an intermediate transmission gear, a lever execution gear, and a lever. The main drive gear, the intermediate transmission gear, and the lever execution gear mesh sequentially. The first servo motor drives the lever to complete the swinging action through the sequentially meshing gears. The top of the lever extends directly into the arc-shaped guide groove at the bottom of the wafer cassette for transmission. The cassette cover is opened by applying force from the bottom.

9. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 1, characterized in that, The short-stroke transmission system includes a second servo motor, a telescopic rod, a support frame, a bracket, and a vertical guide rod. The vertical guide rod and the bracket are both fixed inside the SMIF structure. The output end of the second servo motor is connected to the telescopic rod. The top of the telescopic rod is fixed to the support frame, which is equipped with a loading platform for supporting the wafer cassette after the cover is opened. The bracket is fixed to the side wall of the support frame and slidably fitted outside the vertical guide rod. The vertical guide rod restricts the support frame to only produce vertical displacement. The second servo motor drives the telescopic rod to perform vertical telescopic movement, thereby driving the support frame to achieve vertical short-stroke transport of the wafer cassette after the cover is opened along the vertical guide rod.

10. The integrated predictive correction and synchronous compensation low-position wafer under-cap SMIF system according to claim 9, characterized in that, The short-stroke transmission system is also equipped with an absolute grating ruler, which is used to acquire the vertical position signal of the support frame in real time. The vertical position signal output by the absolute grating ruler is corrected by a thermal deformation error compensation algorithm.

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