Aerotech's new Planar HD air bearing stage provides higher throughput performance at nanometre precision

Assembly Automation

ISSN: 0144-5154

Article publication date: 25 September 2009



(2009), "Aerotech's new Planar HD air bearing stage provides higher throughput performance at nanometre precision", Assembly Automation, Vol. 29 No. 4.



Emerald Group Publishing Limited

Copyright © 2009, Emerald Group Publishing Limited

Aerotech's new Planar HD air bearing stage provides higher throughput performance at nanometre precision

Aerotech's new PlanarHD air bearing stage provides higher throughput performance at nanometre precision

Article Type: New products From: Assembly Automation, Volume 29, Issue 4

New H-bridge gantry builds on a legacy of Aerotech air bearing stage designs to address the requirements of high-end equipment manufacturers for motion systems with improved throughput and increased precision

The new PlanarHD air bearing stage (Figure 1) from Aerotech features several design enhancements for increased throughput in ultra-high precision step-and-settle and scanning applications such as semiconductor processing and emerging MEMS/nano technologies. The 500×500 mm travel stage includes larger air bearing surfaces for significantly improved dynamic characteristics as well as higher power linear servo motors on both axes to deliver an impressive specification that includes a 2 m/s scan velocity and peak acceleration to 5 g – with a positioning resolution of up to 0.25 nm, repeatability to 50 nm and accuracy to ±300 nm.

Figure 1 The new PlanarHD air bearing stage from Aerotech

For Aerotech, this latest generation product follows a long history of motion systems design and manufacture that addresses the high-end equipment industry's unrelenting requirements for improved production times and finished component precision. It is estimated that the PlanarHD will yield a 50 per cent increase in throughput when compared to other manufacturers' stages that have a typical scan velocity of 500 mm/s and 0.5 g acceleration over a 300 mm constant travel range. The 500 mm travel range is also a future proof investment for 450 mm diameter wafer production.

The PlanarHD employs a low mass structural bearing design with a balanced air-on-air preload system for higher lateral, vertical and angular stiffness resulting in improved speed, acceleration and accuracy characteristics. Nominal payload is 5 kg to maintain dynamic specifications with an upper limit of 30 kg. The H-bridge design utilises dual air-bearings, dual linear motors and dual linear encoders on the step axis – and in conjunction with Aerotech's A3200 control system, a calibrated orthogonal/yaw control of 1 arc-sec is made possible for perfectly parallel scans or process swaths over the entire surface of a wafer.

The low profile H-bridge design employs the scan and step axes centrelines and all encoders at the same level, effectively co-locating the centre of mass, the force centre as well as the feedback centre. This ensures a high-dynamic capacity that combines with the optimised air bearing preload system for a 330 Hz first natural frequency and a high servo bandwidth. Furthermore, as all encoders are placed very close to the working plane, Abbe errors are minimised for improved stage precision.

Optional laser interferometer feed back is also available and the 500 mm travel range may be increased up to 1.2 m whilst still maintaining comparable performance and precision levels. As part of Aerotech's comprehensive engineered systems capability, the PlanarHD can be delivered with matching rotary and/or Z-axis stages and the aluminium/granite stage construction may be replaced with more exotic materials such as ceramics, invar, stainless and titanium for further improved performance.

The PlanarHD makes full use of Aerotech's BLM series brushless linear servomotors which feature an ironless forcer with zero cogging for extremely smooth motion and jitter-free in-position stability. BLM series linear motors generate the highest force per unit volume ratio of any competitive linear motor design and to further improve dynamic performance, both air and water cooling thermal management options are available.

The high throughput and ultra-high precision capability of the PlanarHD is completed with Aerotech's A3200 Digital Automation Platform and FireWire® networked Ndrive linear stage amplifiers. This decentralised and fully deterministic PC based motion and machine control system includes advanced features such as trajectory generation with multi-block look ahead to minimise geometry errors in tight profiles by speed/position regulation. Position synchronised output (PSO) is also available to maintain precise synchronisation between the exact real-time X and Y stage position and the customers' laser or light source, with the ability to dynamically modify pulse, power and firing characteristics during motion.

For further motion trajectory optimisation and where improved throughput performance of complex motion profiles is required, users can also call upon Aerotech's Motion Designer software which simplifies trajectory programming and reduces development timescales with analysis tools and iterative learning control algorithms that reduce following error and improve cycle times over multiple runs.

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