PlanarHD Two-Axis Air-Bearing Direct-Drive Linear Stage

Description

Design Features

• Maximize throughput with 2 m/s scan velocity and 5g acceleration
• Faster turnaround and minimized settling times
• Active yaw control
• Linear encoder or laser interferometer feedback
• Travel to 1.2 m by 1.2 m

Aerotech has a long history of engineering and manufacturing the world’s highest performance motion systems to directly address our customers’ key application requirements. 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 Planar_HD “high dynamic” air-bearing motion platform.

Planar_HD Design Features

The Planar_HD air-bearing stage has been designed specifically to maximize throughput by providing up to 2 m/s scan velocity and 5g 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 Planar_HD 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 Planar_HD 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 Planar_HD 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 Planar_HD 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 Planar_HD also includes both air and water cooling thermal management options.

Advanced Control Architecture

The Planar_HD 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 Planar_HD 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.