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Impact of Vibration on Advanced Immersion Lithography

lithography pattern without stacis

Without STACIS®
Best pattern obtained on either the elastomer or rigid version of original pedestal.

lithography pattern with stacis

Pattern achieved with STACIS active vibration isolation.

The 45 nanometer line-width test patterns shown were produced with an advanced Immersion Lithography System manufactured by Amphibian Systems and installed at SEMATECH in Austin, Texas. Variation between the images is due to the effect of seismic vibration on the photolithography process. The images shown were obtained using a scanning electron microscope.

sematech application 1
sematech application 2

The tool was initially installed on a steel and concrete plinth with a steel support structure which incorporated commercial elastomer vibration isolation pads. This pedestal did not achieve the tool’s specified vibration criteria and pattern quality was poor.

In an attempt to reduce vibration, the elastomer pads were effectively shorted out with metal shims leading to a more rigid, non-resonant structure but this resulted in little improvement. The vibration criteria were not met with either version of the pedestal and pattern quality remained poor.

The plinth support structure was removed and retrofitted with a STACIS® Active Piezoelectric Vibration Cancellation System. The STACIS mounts were placed directly beneath the existing plinth. Supporting the tool on STACIS resulted in a dramatic reduction of overall seismic vibration levels and achievement of the manufacturer’s floor vibration specification. More importantly, STACIS provided a dramatic improvement in pattern quality.

sematech application measurements with and without stacis active vibration isolation

Vibration measurements with different configurations. Tool specification: 0.125 mils/s RMS. Vertical axis data shown.
Green: Elastomer isolation
White: Shorted elastomer isolation
Blue: STACIS isolation

*Photos, images, and vibration data courtesy of Sematech.

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