Aerotech has a long history of engineering and
manufacturing the world’s highest performance motion systems
to directly address our customers’ key application needs.
These efforts have helped to enable key technologies in a multitude
of industries including semiconductor, medical, and military/aerospace.
This extensive history and experience have culminated in the development
of the PlanarHD “high dynamic”
air-bearing motion platform. Every component and design feature
has been selected to provide the highest possible dynamic performance
for applications requiring extremely high throughput while maintaining
very tight geometric characteristics.
PlanarHD Design Features
The PlanarHD air-bearing stage
has been designed specifically to maximize throughput by providing
up to 2 m/s scan velocity and 5 g acceleration. The design utilizes
a highly engineered mechanical structure that increases air-bearing
stiffness and decreases moving mass. In addition, the locations
of the center of force and the center of mass have been optimized
to eliminate parasitic forces that can result in throughput reducing
error motions.
To further enhance stage performance, the PlanarHD
uses air-on-air lateral preload on both the X and Y axes. This
preload method uses opposing positive-pressure air films to balance
the bearing lift and preload forces. The dynamic bearing force
balancing method gives the PlanarHD
maximum stiffness, which provides faster turnaround and minimal
settling time.
Unlike monolithic L-designs that rely on only a single vacuum
preloaded gantry axis, the Aerotech gantry axis is a dual air-bearing
H-bridge design that incorporates dual linear motors and dual
linear encoders. This further improves turnaround performance
while providing the added benefit of orthogonality/yaw control.
Faster turns means higher throughput and smaller stage footprint,
while orthogonality control means that process swaths are parallel
over the entire wafer surface.
Feedback System
Both linear encoder and laser interferometer options are available.
The PlanarHD incorporates three
high-accuracy linear encoders, one for the bridge axis and two
for the gantry axis, as standard. Each encoder is mounted so that
the scale centerline is as close to the working plane as possible
to reduce Abbe errors. Both encoder materials and mounting methods
have been chosen to specifically address thermal-induced accuracy
errors.
Drive System
A key to PlanarHD performance
is the use of Aerotech’s BLM series brushless linear servomotors.
The BLM series linear motors utilize an ironless forcer that provides
zero cogging motion with no attractive forces, resulting in extremely
smooth motion. In addition, BLM series linear motors generate
the highest force per unit volume of any competitive motor design.
The PlanarHD also includes both
air and water cooling thermal management options.
Advanced Control Architecture
The PlanarHD is coupled to Aerotech’s
advanced Automation 3200 control system. The Automation 3200 is
a 100% digital system with high performance FireWire®
networked drives. The fully digital architecture makes it possible
to optimize the current, velocity, and position servo loops for
maximum performance. Advanced trajectory generation capabilities,
such as multi-block look-ahead, minimize geometry errors during
fast turnaround, while our Position Synchronized Laser Firing
Output (PSO) functionality automatically adjusts the laser pulse
frequency to match the stage speed to maintain optimal system
performance.
Aerotech's ETM (Enhanced Throughput Module) option helps improve the positioning performance of high-dynamic motion systems like the PlanarHD by directly measuring the unwanted motion of the machine base and communicating it back to the controller. By working in concert with the Dynamic Controls Toolbox and Aerotech controllers, the ETM significantly improves move-and-settle time and contouring performance, increases throughput of existing and new machines, and greatly reduces the effects of frame motion on the servo system.
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