Slit Valve Servo Control for Vibration Reduction
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Solution Overview
Problem
Conventional pneumatic slit valve control methodologies lack real-time knowledge of the gate's position during its full stroke and cannot adjust the motion profile, leading to undesirable vibrations, particle generation, and wafer defects due to hard stops when the gate reaches its end position at high velocity.
Innovation Solution
A servo-control system with a proportional pneumatic valve and continuous position sensor is used to control the slit valve, allowing real-time monitoring and adjustment of the gate's position and motion profile, enabling smooth acceleration, deceleration, and force adjustment throughout the stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional pneumatic actuators with full stroke actuation are used, then the gate can transition between open and closed positions, but the gate hits a hard stop at high velocity causing vibrations and particle generation
Solution Approach 1:
The patent applies dynamics by transitioning from a static full-stroke actuation system to a dynamic servo-controlled system. The gate velocity is continuously adjusted during motion, allowing acceleration at the start and deceleration before reaching the closed position. This dynamic control eliminates hard stops and high-velocity impacts that cause vibrations and particle generation, while maintaining efficient gate transition.
Solution Approach 2:
The patent changes the velocity parameter throughout the gate stroke rather than maintaining constant speed. The servo controller modifies the pneumatic pressure parameters in real-time, reducing pressure near the end of the stroke to decelerate the gate. This parameter change approach allows the gate to reach the closed position smoothly at low velocity, eliminating harmful vibrations and particle generation while preserving fast transition capability.
2Measurement precision
If discrete sensors at end positions are used, then the gate position can be detected at open and closed states, but there is no knowledge of the gate's whereabouts during motion
Solution Approach 1:
The patent implements feedback by using a continuous position sensor that provides real-time position information throughout the gate stroke, not just at end positions. This continuous feedback is fed to the servo controller, which uses it to adjust pneumatic pressure and control gate velocity. The feedback mechanism eliminates information loss during motion, enabling precise knowledge of gate whereabouts at any moment for optimized motion control.
Solution Approach 2:
The patent substitutes the mechanical discrete sensor system with an electronic continuous sensing system. Instead of relying on mechanical switches or discrete sensors that only detect end positions, the system uses electronic position sensing (such as potentiometers, encoders, or other electronic position detection devices) that provide continuous electrical signals corresponding to gate position. This substitution enables seamless position information acquisition throughout the entire stroke.
3Extent of automation
If a servo-control system with continuous position sensing is implemented, then real-time motion control is achieved, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the servo-control system to perform multiple functions through a single integrated controller. The servo controller simultaneously manages position sensing, velocity calculation, pressure modulation, and safety monitoring. This multi-functionality reduces the need for separate dedicated components for each control function, thereby limiting the increase in device complexity while achieving comprehensive real-time motion control.
Solution Approach 2:
The patent uses an intermediary approach by introducing a servo controller as a mediating device between the pneumatic actuator and the gate. This intermediary component translates desired gate position commands into appropriate pneumatic pressure signals, handling the complexity of real-time control calculations and pressure modulation. By centralizing control logic in this intermediary servo controller, the system achieves sophisticated motion control without distributing complexity across multiple separate components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides real-time control over the slit valve's motion, reducing vibrations and particle generation by ensuring a clean and easy stop at the end position, improving the precision and efficiency of wafer processing systems.
Implementation Method 1
The actuators can be pneumatic actuators that include one or more pistons for moving the gate from an open position to a closed position and vice versa
Data Source
AI summary
Disclosed are a slit valve apparatus and a method for controlling a slit valve. The slit valve apparatus includes a slit valve assembly and a servo-control system in communication with the slit valve assembly. The slit valve assembly includes at least one gate able to transition between an open position and a closed position, at least one pneumatic actuator, at least one proportional pneumatic valve including a plurality of controllers, and a continuous position sensor. The servo-control system includes a centralized controller that generates a control signal and adjusts the movement of the at least one gate based on the position trajectory for the gate, a linear position measurement of the gate from the continuous position sensor, and fluid pressure/flow measurements from the plurality of controllers.