Long Stroke Planar Motion Technology

A magnetically-levitated planar motion technology capable of long stroke motion, high acceleration and high positioning accuracy.



There are a number of key technical advantages making this invention particularly suitable for next-generation lithography and factory automation applications:

  • 6 DOF: The stage can be actively controlled in 6-DOF motion.
  • Long stroke > 450mm in XY: The stroke is only limited by the stator coil area, which can be easily extended using printed-circuit board manufacturing technology.
  • No moving coils or coil-cooling cables attached to the stage.
  • Resolution <1 nm: The resolution is limited by the resolution of position feedback sensors. No positioning noise is introduced by stage heat or lines feeding the stage
  • Dual stage compatible: Multiple stages can be conveniently controlled to generate concurrent and independent motion.
  • High acceleration: 10 G peak acceleration is readily achievable in vacuum operation.
  • Positioning sensor selection flexibility: Both sub-micron resolution and sub-nanometer resolution can be achieved with suitable position sensors. Zero force coupling: There is no cross-talk force coupling among different sets of coils.
  • Zero fringing field effect: The unique coil and magnet design eliminate all the non-ideal boundary effect near the edge of magnets.
  • Invariant force distribution on movers: The force distribution on the mover is position independent.
  • Planar stroke scalability: The number of coils is proportional to the peripheral length of the stator coil array, not the area of the stator.
  • High overall filling factor: Unlike race-track coils, linear coil strips can be distributed on the stator surface side by side with the minimum gaps set by the PCB etching process.
  • Compatible with mass production: Coil arrays are manufactured using a commercial PCB manufacturing process, which can provide significant advantages in cost.

Technology Details

Figure 1 shows the concept of a moving magnet stage. Four one-dimensional Halbach magnet arrays (X1, Y2, X3, Y4) are attached to a mover, with a stationary set of straight coils underneath. The stator is made of alternating stacks of coils arranged orthogonally in the X and Y directions. Each coil can be individually energized. The coils with driven currents (active) are shown in solid colours, and inactive coils (no current) are dashed lines. The zones of active coils change dynamically with the mover position in the stator plane. Each magnet array interacts with its corresponding active coils to produce actuation forces.

Figure 1: Electromagnetic configuration of 6DOF direct drive stage.

Figure 2 shows the cross-section of the Y2 magnet array and Y2 active coils. The magnet array is comprised of a typical series of vertically and horizontally magnetized elements, generating a symmetric Halbach array. Interaction of the magnet field with current in the active Y-coils shown in blue will simultaneously generate a levitation force FZ2 and translation force FX2 on the Y2 magnet. Four magnets arrays generate all required forces for 6-DoF motion. Figure 2: Cross-section of Y2 magnet array, inactive Y-coils in grey, active Y2-coils in blue, and X-coils in pink. 

Figure 2: Cross-section of Y2 magnet array, inactive Y-coils in grey, active Y2-coils in blue, and X-coils in pink.

Market Opportunity 

UBC’s planar motion stage technology is well suited for applications requiring long strokes, high positioning accuracy and high acceleration. Potential applications include:

Lithography: UBC’s technology can deliver high wafer throughput in next generation lithography applications for 450mm+ wafers that require high wafer throughput and dual stages.

Factory Automation: UBC’s technology can deliver accurate positioning and high throughput in a large variety of demanding manufacturing applications that include fiber optics and semiconductors.