Lithography Positioning Actuator With Shorted Conductor for High Bandwidth
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Solution Overview
Problem
Existing electromagnetic positioning systems in lithographic apparatuses face limitations in achievable bandwidth due to increased impedance and phase lag at higher frequencies, requiring higher driving voltages and resulting in motor driver dissipation and reduced dynamic performance.
Innovation Solution
Incorporating a further electric conductor, such as a non-ferromagnetic material like copper or aluminum, magnetically coupled to the coil assembly, which provides a short circuit path for inductive currents, reducing impedance and maintaining the coil magnetic field at higher frequencies, thus enhancing bandwidth and reducing amplifier dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electromagnetic actuator with coil assembly and magnet assembly is used for positioning, then positioning function is achieved, but impedance increases with frequency leading to limited bandwidth
Solution Approach 1:
A non-ferromagnetic electrically conductive material is introduced as an intermediary component between the coil assembly and magnet assembly. This intermediate conductor provides a short circuit path for inductive currents, reducing the overall impedance of the actuator at higher frequencies and enabling higher bandwidth operation without excessive energy loss.
2Speed
If higher driving voltage is applied to overcome increased impedance at high frequency, then actuation at higher frequency is achieved, but motor driver dissipation increases
Solution Approach 1:
The inductive currents that previously caused harmful impedance increases and energy dissipation are converted into a beneficial effect. By providing a controlled short circuit path through the non-ferromagnetic conductor, these inductive currents now reduce the overall impedance and improve the actuator's high-frequency response, transforming a harmful phenomenon into a useful mechanism for enhancing bandwidth.
3Speed
If electromagnetic actuator operates at higher frequency, then faster positioning is achieved, but phase lag increases reducing positioning precision
Solution Approach 1:
The electrical parameters of the actuator are modified by introducing the non-ferromagnetic conductive material. This changes the impedance characteristics and phase response of the actuator, reducing phase lag at higher frequencies and enabling faster positioning while maintaining precision through improved electrical parameter optimization.
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
The solution effectively increases the bandwidth of the positioning system, reduces high-frequency impedance, and minimizes phase lag, enabling faster and more precise positioning with reduced energy dissipation in the motor driver.
Implementation Method 1
The coil assembly, when driven by a drive current, generates a magnetic field, the drive current interacts with a magnetic field provided by the magnet assembly, as may result in a force between the coil assembly and the magnet assembly
Implementation Method 2
the drive current interacts with a magnetic field provided by the magnet assembly, as may result in a force between the coil assembly and the magnet assembly
Implementation Method 3
the further electric conductor is magnetically coupled to the coil of the coil assembly and forms a short circuit path for an inductive electrical current induced in the further electric conductor as a result of an actuator current in the coil
Implementation Method 4
forms a short circuit path for an inductive electrical current induced in the further electric conductor
Data Source
Figure 1
Figure 2A~4B
Figure 4C~5
AI summary
A positioning system to position a structure comprises an actuator and a control unit to control the actuator in response to a position setpoint received by the control unit. The actuator comprises a magnet assembly comprises a magnet configured to provide a magnetic flux, and a coil assembly, wherein the coil assembly and the magnet assembly are movable relative to each other, the coil assembly comprising a coil, an actuation of the coil by a drive current providing for a force between the magnet assembly and the coil assembly. The magnet assembly comprises a further electric conductor, the further electric conductor comprising a non-ferromagnetic electrically conductive material, wherein the further electric conductor is magnetically coupled to the coil of the coil assembly and forms a short circuit path for an inductive electrical current induced in the further electric conductor as a result of an actuator current in the coil.