Active Vibration Isolation with Feedforward Control
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Solution Overview
Problem
Vibration isolation systems in the semiconductor industry face challenges in minimizing the impact of mass-induced and other disturbances on sensitive equipment, such as lithography devices, due to movements of positioning units during acceleration and deceleration, which cause spurious vibrations that can disrupt the operational state of these devices.
Innovation Solution
An active vibration isolation system with feedforward control is implemented, using a combination of low-stiffness springs and dampers, along with a control unit that detects predictable mass-induced forces and air pressure fluctuations, and applies counteracting forces to maintain the original vibrational state by sending pre-calculated or experimentally determined signals to the vibration isolation system in coordination with the movements of the positioning unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active vibration damping is applied to counterbalance mass-induced forces, then spurious vibrations are reduced, but the system complexity increases due to additional sensors, actuators, and control mechanisms
Solution Approach 1:
The system measures positioning unit movements once and pre-calculates all necessary counteracting forces in advance. By storing these pre-calculated compensation signals in memory, the system avoids the need for complex real-time calculation and continuous sensing during vibration events, thereby reducing system complexity while still achieving effective spurious vibration reduction.
Solution Approach 2:
The system creates a model or copy of the expected mass-induced forces based on predicted positioning unit movements. By using this copied force profile to generate counteracting signals, the system simplifies the control mechanism while maintaining effectiveness in reducing spurious vibrations, as it relies on the force model rather than complex real-time sensing and calculation.
2Productivity
If the positioning unit moves the substrate repeatedly for inspection or processing, then productivity is improved, but recurring spurious vibrations are generated during acceleration and deceleration phases
Solution Approach 1:
The system pre-calculates counteracting forces for each expected positioning unit movement cycle and stores them in memory. When the positioning unit performs repetitive substrate movements, the control unit retrieves the appropriate pre-calculated compensation signals and applies them in time coordination with each movement cycle. This allows continuous high-speed substrate processing while effectively suppressing recurring spurious vibrations through advance preparation of compensation signals.
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 approach effectively suppresses spurious vibrations, ensuring that the vibrational state of the inspection or processing unit remains unchanged, thereby enhancing the stability and sensitivity of semiconductor equipment operations.
Implementation Method 1
Spring systems are used for vibration isolation of the examination or processing unit
Implementation Method 2
If vibrations in the range of the resonance frequency of the unit can occur in a specific application, the spring systems are supplemented by dampers
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Vibration isolation system with disturbance force application for compensating mass-induced or other disturbance forces, which occur, for example, when replacing a substrate in an immersion lithography system in the semiconductor industry. The active vibration isolation system (2) comprises actuator means (3, 8) for applying counterforces to compensate for the disturbance forces, sensor means (41, 51) for measuring these disturbance forces, and control means (4, 5) for transmitting suitable signals to the actuator means (3, 8).