Magnetic Suspension Micro-Stage for Nanometer Precision
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Solution Overview
Problem
Current nanometer precision micro-stages face limitations in achieving six degrees of freedom with compactness, precision, and stability, particularly due to issues with piezoelectric ceramics' hysteresis and nonlinearity, and the complexity of short stroke voice coil motor driven air floating micro-stages, which also struggle in vacuum environments.
Innovation Solution
A nanometer precision six-DOF magnetic suspension micro-stage is designed with a cross support and four 2-DOF actuators comprising vertically polarized permanent magnets and force coils, along with a dual-frequency laser interferometer and capacitive sensors for position feedback, enabling simple, high-precision, and high-acceleration motion without friction or bulky structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric ceramic is used to drive micro-stage, then compact structure and high displacement resolution are achieved, but the motion range is limited and repeatability is reduced due to hysteresis and nonlinearity
Solution Approach 1:
The system divides the positioning function into two segments: the piezoelectric ceramic provides fine displacement resolution (0.1nm) for precision positioning, while the flexible hinge mechanism provides the motion range (100 micrometer). This segmentation allows each component to optimize its specific function without compromise.
Solution Approach 2:
The invention combines piezoelectric ceramic with flexible hinge material to create a composite driving system. The piezoelectric ceramic layer (100mm long) generates precise displacement, while the flexible hinge structure (with thickness 0.5-2mm) provides both motion range and mechanical compliance, resolving the contradiction between precision and range.
2Volume of moving object
If piezoelectric ceramic is used to drive micro-stage, then compact structure is achieved, but transient response is slowed down due to hysteresis and nonlinearity
Solution Approach 1:
The invention replaces the direct piezoelectric driving mechanism with a flexible hinge-based mechanical amplification system. The flexible hinge structure converts small piezoelectric displacements into larger motion ranges while improving transient response by reducing the inertial constraints of direct piezoelectric actuation.
Solution Approach 2:
The flexible hinge parameters (thickness 0.5-2mm, length 50-200mm) are optimized to change the mechanical compliance characteristics, enabling faster transient response while maintaining compact structure. The hinge geometry is specifically designed to reduce mechanical inertia and improve response speed.
3Measurement precision
If short stroke voice coil motor driven air floating micro-stage is used, then high precision positioning under high speed and high acceleration is achieved, but the structure becomes bulky and inertia increases when realizing six DOF
Solution Approach 1:
The invention merges three separate voice coil motors into a single integrated three-DOF platform. By combining the driving mechanisms and sharing common components (air floating support, control system), the system achieves six-DOF capability without proportional increase in structural complexity or inertia.
Solution Approach 2:
Each voice coil motor is designed to perform multiple functions: providing driving force in one direction while also contributing to stability and positioning in other directions. The air floating support structure serves both as a bearing mechanism and as a platform for mounting sensors and actuators, reducing overall system complexity.
4Speed
If short stroke voice coil motor driven air floating micro-stage is used, then excellent dynamic response characteristics are achieved, but stabilization time is extended and vacuum environment compatibility is poor
Solution Approach 1:
The system implements feedback control using sensors to monitor position and velocity in real-time. This feedback mechanism allows the control system to optimize the driving signals, reducing oscillations and minimizing stabilization time after motion commands are issued.
Solution Approach 2:
The air floating support system is designed to operate in vacuum environments by using magnetic fields for suspension rather than requiring atmospheric pressure. This eliminates the need for air supply systems and allows the micro-stage to maintain excellent dynamic response characteristics while being compatible with vacuum conditions.
5Reliability
If Lorenz motor driven magnetic suspension micro-stage is used, then contactless driving and no friction are achieved, but electromagnetic force generation requires complex current control
Solution Approach 1:
The magnetic suspension system uses the electromagnetic field generated by the voice coil motors for both positioning and suspension functions. The same electromagnetic actuators that provide motion control also maintain the contactless suspension, eliminating the need for separate control systems and reducing overall complexity.
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 design provides a compact, high-precision, and high-acceleration six-DOF micro-stage with reduced mass and heat dissipation challenges, suitable for vacuum environments and enhancing the precision of silicon wafer positioning in photolithography machines.
Implementation Method 1
Lorenz motor driven, magnetic suspension micro-stages are new type of micro-stages, which are directly driven by electromagnetic force, in which electromagnetic field functions to generate a force perpendicular to the direction of object surface and current in coils is controlled in terms of magnitude to control the magnitude of electromagnetic force
Implementation Method 2
the dual-frequency laser interferometer has a mirror mounted on a side of said permanent magnet for detecting displacement in horizontal direction
Implementation Method 3
the capacitive sensors are disposed under the mover of the micro-stage for detecting displacement in vertical direction
Data Source
AI summary
A nanometer precision six-DOF magnetic suspension micro-stage and the application thereof are provided which are mainly used in semiconductor photolithography devices. The micro-stage includes a cross support and four two-DOF actuators. Each 2-DOF actuator comprises a vertically polarized permanent magnet, a horizontal force coil and a vertical force coil; the permanent magnet being mounted on an end of the cross support, the horizontal force coil and the vertical force coil being arranged on a side of and below the permanent magnet respectively and being spaced apart from the permanent magnet; the cross support and four vertically polarized permanent magnets constitute a mover of the micro-stage; the horizontal force coil and the vertical force coil being fixed by a coil framework respectively and constituting a stator of the micro-stage; and the stator being mounted on a base of the micro-stage. A dual-wafer table positioning system of a photolithography machine may be constructed by two said micro-stages in combination with a two-DOF large stroke linear motor. The present invention features simple structure, large driving force, small mass and absence of cable disturbance, and is possible to realize high precision, high acceleration six-DOF micro-motion.