Wafer rotary drying system based on pressure gradient and self-adaptive chamber pressure control process

Abstract

The invention relates to the technical field of semiconductor manufacturing equipment and process control, and discloses a wafer rotary drying system based on pressure gradient and a self-adaptive chamber pressure control process. The system comprises a drying chamber, a wafer clamping and rotating unit, a pressure regulation and control unit, a central processing unit and a heating and gas supply unit. The method comprises the following steps: loading a wafer to be processed on a vacuum chuck, performing high-speed dehydration treatment, and promoting removal of a liquid film through negative pressure flash evaporation; performing speed reduction transition treatment, and stably switching pressure through an S-shaped curve control strategy; and finally, drying treatment is conducted, and heating nitrogen is introduced to form a laminar flow field to thoroughly sweep residual liquid drops and particulate matter. According to the technical scheme, particle redeposition and water stain residue can be effectively inhibited, the wafer surface quality is remarkably improved, and the production yield is improved from 90% to 95%.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing equipment and process control technology, specifically relating to a wafer rotary drying system based on pressure gradient and an adaptive chamber pressure control process. Background Technology

[0002] In the wet process chain of semiconductor manufacturing, wafer spin drying is a critical final step after cleaning, and its quality directly determines the success or failure of subsequent processes such as photolithography and thin film deposition. An ideal drying process requires the complete removal of residual liquid film from the surface in a very short time, while avoiding defects such as particle redeposition, water stains, and surface oxidation. However, traditional spin drying systems generally employ a static pressure environment—either a constant negative pressure to accelerate evaporation or a slightly positive pressure to prevent contamination—this "one-size-fits-all" pressure strategy cannot match the dynamic evolution of the liquid film state during drying, leading to several unresolved process contradictions: In the high-speed dehydration stage, while a fixed negative pressure can assist centrifugal liquid removal, it easily causes uneven flash evaporation, resulting in droplet splashing and particle disturbance; during the transition period of decreasing rotation speed, the airflow within the chamber is turbulent, and without active pressure intervention, suspended particles are easily reattached to the wafer surface due to turbulent swirling; and in the final drying stage, while a static slightly positive pressure can isolate external contamination, it is difficult to create a directional airflow to efficiently remove residual droplets at the edges, especially for the deep trench areas of 3D structure wafers. The aforementioned issues collectively constrain the stringent requirements for ultra-clean surfaces in high-end manufacturing processes.

[0003] A search revealed that patent CN113130357B proposes a wafer drying system based on heated mixed gas. While it enhances evaporation efficiency through the synergistic effect of organic solvents and hot nitrogen, the chamber pressure remains constant throughout the process. It fails to consider the varying airflow dynamics requirements at different drying stages, resulting in an inability to suppress turbulence at the liquid film rupture critical point and a significantly increased risk of particle redeposition. Another patent, CN111739829B, utilizes the Marangoni effect for liquid film stripping. Although innovative in its physical mechanism, it still relies on a static pressure environment and lacks the ability to actively control the flow field inside the chamber. This makes it difficult to establish a stable exhaust path during the deceleration phase, limiting drying uniformity. Especially when processing 12-inch wafers, the drying rate difference between the edges and center is significant, easily leading to annular water stains.

[0004] The core limitation of the aforementioned technical solutions lies in treating pressure as an auxiliary parameter rather than an actively controlled variable, failing to establish a dynamic coupling relationship between pressure gradient and wafer rotation speed. In fact, the drying process is essentially a complex physical process involving the coupling of multiple fields of centrifugal force, surface tension, gas-phase shear force, and pressure gradient. A single pressure setting cannot achieve a balance between "efficient liquid removal" and "clean protection." Especially at advanced nodes, wafer surface feature sizes shrink to the nanometer scale, and even a single submicron particle can cause device failure. Therefore, an adaptive control strategy that can reconstruct the chamber pressure distribution in real time according to the process stage and precisely link it with rotational dynamics is urgently needed. Thus, this invention provides a wafer rotation drying system based on pressure gradients and an adaptive chamber pressure control process. By constructing a three-stage pressure-rotation speed synergistic curve of "high-speed dehydration - deceleration transition - final drying," and implementing a relay-style protection of negative pressure extraction and micro-positive pressure laminar flow sweeping at critical risk windows, it fundamentally solves the problems of particle redeposition and uneven drying, providing reliable support for high-yield semiconductor manufacturing. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a wafer rotary drying system based on pressure gradient and an adaptive chamber pressure control process, which can effectively solve the problems in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: On one hand, a wafer rotary drying system based on a pressure gradient, comprising the following components: a drying chamber for accommodating the wafer to be processed and providing a sealed process environment, the inner wall of which is made of electropolished stainless steel with a surface roughness Ra≤0.4μm; a wafer clamping and rotating unit for fixing the wafer and driving its rotation, including a spindle, a vacuum chuck, and a drive motor, the spindle achieving dynamic sealing through a vacuum rotary sealing flange; a pressure control unit for precisely controlling the internal pressure of the chamber, including a vacuum pump group, an inert gas mass flow controller, and a pressure sensor, the vacuum pump group employing a dry vortex pump and a Roots pump configured in series; a central processing unit for executing a preset pressure-speed coordinated control algorithm, built on an industrial-grade programmable logic controller, with multiple built-in process recipe databases; and a heating and gas supply unit for supplying heating inert gas to the chamber, including a nitrogen source, a heater, and a temperature controller, the heating power being adjustable within the range of 0.5kW to 3kW.

[0007] Preferably, the drying chamber has a cylindrical geometry with a diameter-to-height ratio of 2:1 to 3:1. An observation window and lighting system are provided at the top of the chamber, and a drainage channel and exhaust port are integrated at the bottom. The maximum spindle speed of the wafer clamping and rotating unit reaches 3000 rpm, with a speed control accuracy of ±10 rpm. The vacuum chuck adopts a multi-zone independent vacuum channel design, and the vacuum level of each zone can be independently monitored and controlled.

[0008] Furthermore, the vacuum pump unit of the pressure control unit has a continuously adjustable pumping speed ranging from 10 m³ / h to 100 m³ / h, achieving an ultimate vacuum of 1 × 10⁻⁶ m³ / h. -2 Pa; the mass flow controller has a flow control range of 0.1 L / min to 20 L / min and a control accuracy of ±1%FS; the pressure sensor adopts the piezoresistive principle, with a measurement range covering -15 kPa to +10 kPa and an accuracy class of 0.1.

[0009] Furthermore, the pressure-speed coordinated control algorithm of the central processing unit is built based on a three-stage process model. Its control cycle is 10ms. It receives speed feedback signals and pressure measurement values ​​in real time and outputs coordinated control commands for the vacuum pump and mass flow controller through a proportional-integral-derivative controller. The process recipe database stores a variety of pressure-speed curve combinations applicable to 4-inch to 12-inch wafers, including dedicated process parameters for planar devices and 3D structure wafers.

[0010] Preferably, the nitrogen purity of the heating and gas supply unit reaches 99.999%, and the dew point is below -70℃; the heater adopts an armored heating tube structure, the heating temperature is adjustable in the range of 25℃ to 100℃, and the temperature control accuracy is ±1℃; the gas delivery pipeline is covered with an insulation layer to ensure that the gas temperature fluctuation during transmission does not exceed ±2℃.

[0011] On the other hand, a wafer rotary drying adaptive chamber pressure control process based on pressure gradient includes the following steps: Step S110, loading the wafer to be processed onto the vacuum chuck in the drying chamber, initiating vacuum adsorption to ensure wafer fixation, initializing system parameters, and selecting the process formulation corresponding to the wafer size and surface structure; Step S120, performing the first stage of high-speed dehydration treatment, controlling the spindle to accelerate the wafer rotation speed from 0 to a set value within the range of 1500 rpm to 2000 rpm within 3 seconds, while simultaneously starting the vacuum pump to reduce the chamber pressure to a negative pressure state within the range of -10 kPa to -5 kPa within 5 seconds, maintaining this state for 15 seconds; Step S130, performing the second stage of deceleration transition. The process involves linearly reducing the wafer rotation speed from a high speed to a second speed within a range of 500 rpm to 1000 rpm within 10 seconds, while simultaneously coordinating the reduction of the vacuum pump speed and the activation of the mass flow controller to smoothly transition the chamber pressure from negative pressure to a slightly positive pressure state within the range of +1 kPa to +5 kPa; Step S140: Perform the third stage final drying process, maintaining the wafer rotation at the second speed and continuously introducing nitrogen gas heated to 60°C to 80°C, maintaining the slightly positive pressure state in the chamber for 10 to 30 seconds until the wafer surface is completely dry; Step S150: After the process is completed, perform chamber depressurization and wafer unloading operations, record process data through the central processing unit, and generate a test report.

[0012] Preferably, the negative pressure environment of the first stage of high-speed dehydration in step S120 lowers the boiling point of the liquid through a physical mechanism described by the Clausius-Clapeyron equation, promoting controlled flash evaporation of the liquid film. Its effect can be expressed as follows: Where P1 and P2 represent the saturated vapor pressures under normal and negative pressure conditions, respectively, and T1 and T2 are the corresponding boiling point temperatures, ΔH vap R is the enthalpy of vaporization of the liquid and R is the ideal gas constant; this mechanism enables the liquid film to be efficiently broken up and removed under the combined action of centrifugal force and pressure gradient.

[0013] Furthermore, in step S130, the pressure switching process of the second-stage deceleration transition adopts an S-curve control strategy, with the pressure change rate limited to within 1 kPa / s and 0.5 kPa / s at the beginning and end of the switching phases, respectively, to ensure a smooth transition of the airflow state; the speed reduction process simultaneously adopts a ramp deceleration mode, with acceleration controlled within the range of -100 rpm / s to -50 rpm / s, to avoid turbulence caused by sudden changes in speed.

[0014] Furthermore, the laminar flow field construction in the third stage final drying process of step S140 is based on a simplified form of the Navier-Stokes equations, and the stable airflow formed by introducing heated nitrogen under micro-positive pressure conditions satisfies: Where ρ is the gas density, v is the flow velocity vector, p is the pressure, and μ is the dynamic viscosity; this flow field forms a directional sweeping effect from the center of the wafer to the edge and then to the exhaust port, effectively removing residual droplets and particulate matter.

[0015] Preferably, when the process is adapted to 4-inch wafers, the first-stage rotation speed is set to 1500 rpm and the negative pressure value is -8 kPa; when adapted to 8-inch wafers, the first-stage rotation speed is increased to 1800 rpm and the negative pressure value is -7 kPa; when adapted to 12-inch wafers, the first-stage rotation speed reaches 2000 rpm and the negative pressure value is -5 kPa; for 3D structure wafers, the third-stage drying time is extended to 30 seconds and the nitrogen temperature is increased to 80°C to ensure thorough drying of the deep trench area.

[0016] Furthermore, the process has been validated in batches of 500 wafers. The average number of 19nm particles on the wafer surface using dynamic pressure regulation has been reduced to 20, a 30.8% reduction compared to 26 particles in fixed micro-positive pressure drying. The production yield has increased from 90% to 95%, and the process stability coefficient CpK has reached 1.67, meeting the stringent requirements of high-end processes for ultra-clean surfaces.

[0017] Compared with existing technologies, this invention has the following advantages: 1. By constructing a dynamic coupling relationship between pressure gradient and wafer rotation speed, negative pressure flash evaporation is used to enhance liquid film removal efficiency during the high-speed dehydration stage, pressure smooth switching is used to suppress turbulence generation during the deceleration transition stage, and micro-positive pressure laminar flow is used to achieve thorough sweeping during the final drying stage, reducing the risk of particle redeposition by more than 30%; 2. By adopting a coordinated control mode of vacuum pump and mass flow controller, precise and rapid pressure adjustment within the range of -10kPa to +5kPa is achieved, the pressure build-up time is shortened to less than 5 seconds, and the control accuracy reaches ±0.2kPa; 3. Through a programmable process recipe database, it can adapt to different sizes of wafers from 4 inches to 12 inches, as well as diverse surface features such as planar devices and 3D structures, and the process window is extended to a wide range of rotation speeds from 500rpm to 2000rpm and pressures from -10kPa to +5kPa; 4. Empirical data has verified that this invention reduces the average number of 19nm particles on the wafer surface from 26 in a fixed pressure process to 20, and increases the production yield from 90% to 95%, providing a reliable ultra-clean drying solution for high-end semiconductor manufacturing. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the wafer rotary drying system based on pressure gradient of the present invention;

[0019] Figure 2 yes Figure 1 Longitudinal sectional view of the sealed drying chamber shown

[0020] Figure 3 This is a schematic diagram of the overall technical solution architecture of the wafer rotary drying system and adaptive chamber pressure control process based on pressure gradient proposed in this invention.

[0021] Figure 4 This is a schematic diagram of the core principle framework of pressure-speed coordinated control and pressure gradient construction in this invention;

[0022] Figure 5 This is a logical flow diagram of the three-stage adaptive chamber pressure control process in this invention;

[0023] Figure 6 This is a schematic diagram illustrating the physical principle of negative pressure flash evaporation and liquid film removal during the high-speed dehydration stage in this invention.

[0024] Figure 7 This is a control strategy framework diagram for pressure smooth switching and turbulence suppression during the deceleration transition phase in this invention;

[0025] Figure 8 This is a schematic diagram illustrating the principle of micro-positive pressure layer flow field construction and directional sweeping effect in the final drying stage of this invention;

[0026] As shown in the attached diagram:

[0027] 1. Drying chamber; 2. Vacuum suction cup; 3. Main shaft; 4. Vacuum rotary sealing flange; 5. Pressure control unit; 6. Heating and gas supply unit; 7. Drive motor. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0029] Example 1

[0030] In the post-cleaning process of wafers in high-end semiconductor manufacturing plants, a pressure gradient-based wafer rotary drying system performs an ultra-clean drying process on 12-inch wafers that have undergone wet cleaning. The drying chamber 1 provides a sealed process environment; its inner walls are made of electropolished stainless steel with a surface roughness controlled below 0.4 micrometers to ensure no particle adsorption or gas retention. The wafer clamping and rotating unit secures the wafer to be processed via vacuum chucks 2, and the spindle 3 achieves dynamic sealing via a vacuum rotary sealing flange 4. The drive motor 7 precisely controls the wafer rotation under the command of the central processing unit. The pressure control unit 5 precisely regulates the internal pressure of the chamber through the coordinated action of a vacuum pump unit and an inert gas mass flow controller. The heating and gas supply unit 6 supplies high-purity nitrogen gas to the drying chamber 1, creating a stable hot gas flow environment.

[0031] See Figure 1-3The drying chamber features a cylindrical geometry with an optimized diameter-to-height ratio of 2.5:1, ensuring uniform airflow distribution while minimizing dead zone volume. An observation window and lighting system at the top of the chamber facilitate visual monitoring of the process, while integrated drainage channels and exhaust ports at the bottom ensure efficient removal of liquids and gases. The wafer clamping and rotation unit's spindle reaches a maximum speed of 3000 rpm with a speed control accuracy of ±10 rpm. The vacuum chuck employs a four-zone independent vacuum channel design, allowing independent monitoring and control of the vacuum level in each zone, ensuring stable wafer clamping during high-speed rotation.

[0032] The vacuum pump unit of the pressure control unit adopts a dry vortex pump and a Roots pump in series configuration, with a pumping speed continuously adjustable from 10 cubic meters per hour to 100 cubic meters per hour, and an ultimate vacuum of 1×10⁻⁶. -2 The mass flow controller has a flow control range of 0.1 L / min to 20 L / min and a control accuracy of ±1% of full scale. The pressure sensor uses the piezoresistive principle, with a measurement range covering -15 kPa to +10 kPa and an accuracy class of 0.1, providing a high-precision feedback signal for pressure control.

[0033] The central processing unit is built on an industrial-grade programmable logic controller (PLC) and executes a preset pressure-speed coordinated control algorithm. This algorithm is based on a three-stage process model, with a control cycle of 10 milliseconds. It receives speed feedback signals and pressure measurements in real time and outputs coordinated control commands for the vacuum pump and mass flow controller via a proportional-integral-derivative (PID) controller. The process recipe database stores various pressure-speed curve combinations applicable to 4-inch to 12-inch wafers, including dedicated process parameters for planar devices and 3D structure wafers.

[0034] The nitrogen in the heating and gas supply unit has a purity of 99.999% and a dew point below -70 degrees Celsius. The heater uses an armored heating tube structure, with adjustable heating power ranging from 0.5 kW to 3 kW and precise temperature control ranging from 25 degrees Celsius to 100 degrees Celsius, with a temperature control accuracy of ±1 degree Celsius. The gas delivery pipeline is covered with an insulation layer to ensure that the gas temperature fluctuation during transmission does not exceed ±2 degrees Celsius.

[0035] The drying process is executed according to the preset procedure: Step S110: The wafer to be processed is loaded onto the vacuum chuck in the drying chamber, vacuum adsorption is started to ensure the wafer is fixed, system parameters are initialized, and the process formula corresponding to the wafer size and surface structure is selected; Step S120: The first stage of high-speed dehydration is performed, controlling the spindle to accelerate the wafer speed from 0 to 2000 rpm within 3 seconds, while the vacuum pump is started to reduce the chamber pressure to a negative pressure of -5 kPa within 5 seconds, and maintain this state for 15 seconds; Step S130: The second stage of deceleration transition is performed, reducing the wafer speed within 10 seconds. The speed is linearly reduced from 2000 rpm to 800 rpm, while the vacuum pump speed is reduced and the mass flow controller is activated in coordination, so that the chamber pressure smoothly transitions from negative pressure to a slightly positive pressure of +3 kPa. Step S140 performs the third stage final drying process, maintaining the wafer at 800 rpm and continuously introducing nitrogen gas heated to 70 degrees Celsius to maintain the slightly positive pressure in the chamber for 20 seconds until the wafer surface is completely dry. Step S150 performs chamber depressurization and wafer unloading operations after the process is completed, and records the process data and generates a test report through the central processing unit.

[0036] See Figure 4 In step S120, the negative pressure environment of the first stage of high-speed dehydration lowers the liquid boiling point through a physical mechanism described by the Clausius-Clapeyron equation, promoting controlled flash evaporation of the liquid film. This mechanism enables the efficient breakup and removal of the liquid film under the synergistic effect of centrifugal force and pressure gradient, and its effect can be expressed as follows: Where P1 and P2 represent the saturated vapor pressures under normal and negative pressure conditions, respectively; T1 and T2 are the corresponding boiling point temperatures; ΔHvap is the enthalpy of vaporization of the liquid; and R is the ideal gas constant. In actual processes, when the chamber pressure drops to -5 kPa, the boiling point of deionized water decreases from 100 degrees Celsius to 45 degrees Celsius, significantly enhancing the evaporation efficiency of the liquid film.

[0037] In step S130, the pressure switching process during the second stage of the deceleration transition adopts an S-curve control strategy. The pressure change rate is limited to 1 kPa / s at the beginning of the switching phase and to within 0.5 kPa / s at the end, ensuring a smooth transition of the airflow state. The speed reduction process simultaneously employs a ramp deceleration mode, with acceleration controlled at -80 rpm / s to avoid turbulence caused by sudden changes in speed. The key to this stage is achieving a smooth transition from high-speed dehydration to low-speed drying, preventing particle redeposition due to drastic changes in the flow field.

[0038] See Figure 5 In step S140, the laminar flow field for the final drying process in the third stage is constructed based on a simplified form of the Navier-Stokes equations. Under slightly positive pressure conditions, the stable airflow formed by introducing heated nitrogen satisfies the following: Where ρ is the gas density, v is the velocity vector, p is the pressure, and μ is the dynamic viscosity. This flow field creates a directional sweeping effect from the wafer center to the edge and then to the exhaust port, effectively removing residual droplets and particles. In the actual process, the slightly positive pressure environment ensures that external contaminants cannot enter the chamber, while heating nitrogen accelerates the evaporation of residual moisture on the surface.

[0039] In practice, the sealing performance of the drying chamber is periodically verified using a helium mass spectrometer leak detector, and the leakage rate is controlled within 1×10⁻⁶. -9 Below Pa·m³ / s. The spindle dynamic balance level of the wafer clamping and rotating unit reaches G1.0, ensuring that the vibration amplitude is less than 2 micrometers during high-speed rotation. The lubricating oil of the vacuum pump unit is perfluoropolyether type, avoiding hydrocarbon pollution of the process environment.

[0040] The pressure build-up process of the pressure control unit is optimized through a feedforward-feedback composite control strategy. The feedforward controller calculates the theoretical pumping time based on the chamber volume and target pressure, and adjusts the vacuum pump speed in advance; the feedback controller makes fine adjustments based on real-time measurements from the pressure sensor. This control method shortens the pressure build-up time to less than 5 seconds, with a control accuracy of ±0.2 kPa.

[0041] The central processing unit's process recipe database dynamically adjusts parameters based on wafer characteristics. For planar device wafers, the first-stage rotation speed is set to 2000 rpm, and the negative pressure is -5 kPa. For 3D structure wafers, considering the drying difficulty of deep trench areas, the first-stage rotation speed is reduced to 1800 rpm, the negative pressure is adjusted to -7 kPa, the third-stage drying time is extended to 30 seconds, and the nitrogen temperature is increased to 80 degrees Celsius.

[0042] The gas purity of the heating and gas supply unit is continuously monitored by an online dew point meter, automatically switching to a backup nitrogen source when the dew point exceeds -70 degrees Celsius. The heater's power control employs pulse width modulation (PWM) technology, achieving precise temperature control by adjusting the duty cycle. The insulation thickness of the gas delivery pipeline has been optimized through thermodynamic calculations to ensure that, at an ambient temperature of 25 degrees Celsius, the temperature drop of 70 degrees Celsius nitrogen during transmission does not exceed 2 degrees Celsius.

[0043] Key parameters in the process are recorded and tracked in real time through the manufacturing execution system. Process parameters such as rotational speed, pressure, and temperature are sampled and stored at 100-millisecond intervals to form a complete process traceability file. When any parameter exceeds the control limit, the system immediately triggers an alarm and suspends the process, resuming operation after the anomaly is resolved.

[0044] After batch verification on 500 wafers, the average number of 19nm particles on the wafer surface using this process was reduced to 20, a 30.8% reduction compared to 26 particles in fixed micro-positive pressure drying. Production yield increased from 90% to 95%, and the process stability coefficient CpK reached 1.67, meeting the stringent requirements of high-end processes for ultra-clean surfaces. Particle distribution uniformity was measured using a laser particle counter; the difference in particle count between the wafer center and edge regions was less than 15%, indicating excellent uniformity in the drying process.

[0045] Example 2

[0046] In advanced packaging wafer manufacturing workshops, this system performs a special drying process for 8-inch through-silicon via (TSV) wafers. The drying chamber's process parameters are adjusted according to the 8-inch wafer size, with the diameter-to-height ratio optimized to 2.2:1. The maximum spindle speed of the wafer clamping and rotating unit is set to 2500 rpm, and the vacuum chuck employs a six-zone independent vacuum channel design to accommodate the uneven surface structure of TSV wafers.

[0047] The vacuum pump unit of the pressure control unit was adjusted to a pumping speed of 50 cubic meters per hour, and the mass flow controller's flow range was set to 0.5 liters per minute to 15 liters per minute. The pressure sensor's measurement range was adjusted to -12 kPa to +8 kPa, maintaining an accuracy class of 0.1. The central processing unit loaded a special process formula for through-silicon via (TSV) wafers, optimizing control parameters for the drying requirements of high aspect ratio TSV structures.

[0048] The nitrogen purity in the heating and gas supply unit has been increased to 99.9995%, with a dew point requirement below -75 degrees Celsius. The heater power has been adjusted to 2 kW, and the heating temperature range has been expanded to 30 to 90 degrees Celsius. A heat tracing system has been added to the gas delivery pipeline to ensure that high-purity nitrogen does not condense during transmission.

[0049] The drying process is adapted based on the standard procedure: In the first stage of high-speed dehydration in step S120, the wafer rotation speed is set to 1800 rpm, the chamber pressure drops to -7 kPa within 5 seconds, and the holding time is extended to 18 seconds to ensure effective removal of the liquid film in the vias; In the second stage of deceleration transition in step S130, the rotation speed is linearly reduced from 1800 rpm to 600 rpm, the transition time is extended to 12 seconds, and the pressure smoothly transitions from -7 kPa to +2 kPa to avoid capillary effects caused by sudden pressure changes in the via structure; In the third stage of final drying in step S140, the wafer is kept rotating at 600 rpm, nitrogen gas heated to 75 degrees Celsius is introduced, and the chamber is kept under a slight positive pressure for 25 seconds to ensure thorough drying of the deep vias.

[0050] In terms of process control, the negative pressure flash evaporation process in step S120 is optimized for the silicon via structure. By increasing the negative pressure value and extending the action time, the evaporation efficiency of the liquid film inside the via is enhanced. The pressure switching in step S130 adopts a dual-ramp control strategy. A fast switching mode is used in the range of -7 kPa to -3 kPa, with the rate of change set at 1.2 kPa / s; a slow switching mode is used in the range of -3 kPa to +2 kPa, with the rate of change reduced to 0.3 kPa / s, to ensure a smooth transition of airflow inside the via.

[0051] Step S140, the laminar flow field construction, is optimized for the characteristics of the through-silicon via (TSV) wafer. The flow rate of the introduced heated nitrogen gas is controlled at 0.5 m / s to form a stable laminar sweep. Computational fluid dynamics simulations verify that under this flow rate condition, the Reynolds number of the gas flow inside the TSV is less than 100, ensuring no turbulence is generated. The nitrogen temperature is precisely controlled at 75°C ± 1°C to ensure drying efficiency while avoiding thermal stress damage.

[0052] Process adaptability is achieved through multi-parameter collaborative optimization. For through-hole structures with different aspect ratios, the third-stage drying time is dynamically adjusted according to the through-hole depth: the drying time for through-holes with a depth less than 50 micrometers is set to 20 seconds, the drying time for through-holes with a depth of 50 to 100 micrometers is extended to 25 seconds, and the drying time for through-holes with a depth greater than 100 micrometers is further extended to 30 seconds. The nitrogen temperature is adjusted according to the through-hole diameter: 70 degrees Celsius nitrogen is used for through-holes with a diameter greater than 5 micrometers, 75 degrees Celsius nitrogen is used for through-holes with a diameter of 2 to 5 micrometers, and 80 degrees Celsius nitrogen is used for through-holes with a diameter less than 2 micrometers.

[0053] System performance was verified through both online monitoring and offline analysis. Online monitoring used an infrared thermal imager to measure the wafer surface temperature distribution in real time, ensuring that temperature uniformity was controlled within ±3 degrees Celsius during the drying process. Offline analysis used a scanning electron microscope to examine the drying status inside the vias, confirming the absence of liquid residue and particle contamination. After process verification on 300 silicon via wafers, the via drying integrity rate reached 99.5%, and the average number of surface particles was controlled to within 25, meeting the stringent requirements of advanced packaging processes.

[0054] The process data and quality management system are deeply integrated, with all process parameters, monitoring data, and analysis results automatically uploaded to a cloud database. Machine learning algorithms are used to analyze the correlation between process parameters and drying effects, continuously optimizing the control model. When process deviations are detected, the system automatically adjusts control parameters to achieve adaptive process optimization. Historical data traceability supports rapid identification of the causes of anomalies, providing data support for process improvement.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A wafer rotary drying system based on pressure gradient, characterized in that, The system includes the following components: The drying chamber (1) is used to contain the wafer to be processed and provide a closed process environment. Its inner wall is made of electropolished stainless steel with a surface roughness Ra≤0.4μm. The geometry of the drying chamber is cylindrical, and its diameter to height ratio is designed to be in the range of 2:1 to 3:

1. An observation window and lighting system are set at the top of the chamber, and a drainage channel and exhaust port are integrated at the bottom. The wafer clamping and rotating unit is used to fix the wafer and drive it to rotate. It includes a spindle (3), a vacuum chuck (2) and a drive motor (7). The spindle achieves dynamic sealing through a vacuum rotary sealing flange (4). The maximum speed of the spindle reaches 3000 rpm and the speed control accuracy is ±10 rpm. The vacuum chuck adopts a multi-zone independent vacuum channel design, and the vacuum degree of each zone can be independently monitored and controlled. The pressure control unit (5) is used to precisely control the internal pressure of the chamber. It includes a vacuum pump group, an inert gas mass flow controller, and a pressure sensor. The vacuum pump group adopts a dry vortex pump and a Roots pump in series configuration. The pumping speed of the vacuum pump group is continuously adjustable in the range of 10 m³ / h to 100 m³ / h, and the ultimate vacuum degree reaches 1×10⁻⁶ m³ / h. -2 Pa, the mass flow controller has a flow control range of 0.1 L / min to 20 L / min and a control accuracy of ±1%FS; the pressure sensor adopts the piezoresistive principle, with a measurement range covering -15 kPa to +10 kPa and an accuracy class of 0.

1. The central processing unit is used to execute a preset pressure-speed coordinated control algorithm, which is built on an industrial-grade programmable logic controller and has multiple process recipe databases built in. The pressure-speed coordinated control algorithm is built on a three-stage process model, with a control cycle of 10ms. It receives speed feedback signals and pressure measurement values ​​in real time, and outputs coordinated control commands for the vacuum pump and mass flow controller through a proportional-integral-derivative controller. The process recipe database stores a variety of pressure-speed curve combinations applicable to 4-inch to 12-inch wafers, including dedicated process parameters for planar devices and 3D structure wafers. The heating and gas supply unit (6) is used to supply inert gas for heating to the chamber. It includes a nitrogen source, a heater and a temperature controller. The heating power is adjustable from 0.5kW to 3kW. The nitrogen has a purity of 99.999% and a dew point below -70℃. The heater adopts an armored heating tube structure. The heating temperature is adjustable from 25℃ to 100℃. The temperature control accuracy is ±1℃. The gas delivery pipeline is covered with an insulation layer to ensure that the gas temperature fluctuates by no more than ±2℃ during transmission.

2. The wafer rotary drying system based on pressure gradient according to claim 1, characterized in that, The sealing performance of the drying chamber is periodically verified using a helium mass spectrometer leak detector, and the leakage rate is controlled within 1×10⁻⁶. -9 Pa·m³ / s or less; the spindle dynamic balance level of the wafer clamping and rotating unit reaches G1.0, ensuring that the vibration amplitude is less than 2μm during high-speed rotation; the lubricating oil of the vacuum pump group is perfluoropolyether type, avoiding hydrocarbon pollution of the process environment.

3. The wafer rotary drying system based on pressure gradient according to claim 1, characterized in that, The pressure build-up process of the pressure control unit is optimized through a feedforward-feedback composite control strategy. The feedforward controller calculates the theoretical pumping time based on the chamber volume and target pressure, and adjusts the vacuum pump speed in advance. The feedback controller makes fine adjustments based on the real-time measurement value of the pressure sensor. This control method shortens the pressure build-up time to less than 5 seconds and achieves a control accuracy of ±0.2 kPa.

4. The wafer rotary drying system based on pressure gradient according to claim 1, characterized in that, The process recipe database of the central processing unit dynamically adjusts parameters according to the characteristics of the wafer. For planar device wafers, the rotation speed in the first stage is set to 2000 rpm and the negative pressure value is -5 kPa. For 3D structure wafers, the rotation speed in the first stage is reduced to 1800 rpm and the negative pressure value is adjusted to -7 kPa. The drying time in the third stage is extended to 30 seconds and the nitrogen temperature is increased to 80°C.

5. The wafer rotary drying system based on pressure gradient according to claim 1, characterized in that, The gas purity of the heating and gas supply unit is continuously monitored by an online dew point meter. When the dew point is higher than -70℃, it automatically switches to the backup nitrogen source. The power control of the heater adopts pulse width modulation technology, and the temperature is precisely controlled by adjusting the duty cycle. The insulation layer thickness of the gas delivery pipeline has been optimized by thermodynamic calculations to ensure that the temperature drop of 70℃ nitrogen does not exceed 2℃ during transmission under ambient temperature of 25℃.

6. A wafer rotary drying adaptive chamber pressure control process based on pressure gradient, characterized in that, The method includes the following steps: Step S110: Load the wafer to be processed onto the vacuum chuck in the drying chamber, start vacuum adsorption to ensure the wafer is fixed, initialize system parameters and select the process formula corresponding to the wafer size and surface structure. Step S120: Perform the first stage of high-speed dehydration treatment. Control the spindle to accelerate the wafer speed from 0 to a set value in the range of 1500 rpm to 2000 rpm within 3 seconds. At the same time, start the vacuum pump to reduce the chamber pressure to a negative pressure state in the range of -10 kPa to -5 kPa within 5 seconds and maintain this state for 15 seconds. Step S130: Perform the second stage of speed reduction transition processing. Within 10 seconds, the wafer rotation speed is linearly reduced from the first high speed to the second speed in the range of 500 rpm to 1000 rpm. At the same time, the vacuum pump speed is reduced and the mass flow controller is turned on in coordination, so that the chamber pressure smoothly transitions from negative pressure to a slightly positive pressure state in the range of +1 kPa to +5 kPa. Step S140: Perform the third stage final drying process, keep the wafer rotating at the second rotation speed, continuously introduce nitrogen gas heated to 60°C to 80°C, maintain a slightly positive pressure in the chamber for 10 to 30 seconds, until the wafer surface is completely dry. Step S150: After the process is completed, chamber depressurization and wafer unloading operations are performed, and process data is recorded and a test report is generated through the central processing unit.

7. The adaptive chamber pressure control process for wafer rotary drying based on pressure gradient according to claim 6, characterized in that, The negative pressure environment of the first stage of high-speed dehydration in step S120 lowers the boiling point of the liquid through a physical mechanism described by the Clausius-Clapeyron equation, promoting controlled flash evaporation of the liquid film. Its effect can be expressed as follows: Where P1 and P2 represent the saturated vapor pressures under normal and negative pressure conditions, respectively, and T1 and T2 are the corresponding boiling point temperatures, ΔH vap R is the enthalpy of vaporization of the liquid and R is the ideal gas constant; this mechanism enables the liquid film to be efficiently broken up and removed under the combined action of centrifugal force and pressure gradient.

8. The adaptive chamber pressure control process for wafer rotary drying based on pressure gradient according to claim 6, characterized in that, In step S130, the pressure switching process of the second stage of deceleration transition adopts an S-curve control strategy. The pressure change rate is limited to within 1 kPa / s and 0.5 kPa / s at the beginning and end of the switching stage, respectively, to ensure a smooth transition of the airflow state. The speed reduction process adopts a ramp deceleration mode simultaneously, with the acceleration controlled within the range of -100 rpm / s to -50 rpm / s to avoid turbulence caused by sudden changes in speed.

9. The adaptive chamber pressure control process for wafer rotary drying based on pressure gradient according to claim 6, characterized in that, The laminar flow field construction in the third stage final drying process of step S140 is based on a simplified form of the Navier-Stokes equations. Under slightly positive pressure conditions, the stable airflow formed by introducing heated nitrogen satisfies the following: Where ρ is the gas density, v is the flow velocity vector, p is the pressure, and μ is the dynamic viscosity; this flow field forms a directional sweeping effect from the center of the wafer to the edge and then to the exhaust port, effectively removing residual droplets and particles.

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