Standard sample stages of Electron Microscopes are not very precise in positioning. Often the user likes to have something more precise, e.g. for automatic Wafer Probing or sample alignment during e-beam lithography, perhaps after years of using the SEM. The exchange of the sample stage is expensive, perhaps impossible. But adding Nanorobotics modules is easy: Just place them onto the existing sample stage, and we will add a feedthrough and configured cables. The following turnkey solution ist sold by Raith GmbH Dortmund, Germany, using our Nanorbotics stages in any kind of SEM chamber that can be used for e-beam Lithography:

"XY-positioning and stitching improvements for conventional SEM based lithography solutions by piezoelectric sub-stage assembly" *
Raith GmbH Dortmund, Germany:

Introduction:
Conventional SEM stages are lacking the precision for certain lithography procedures; while conventional step and repeat of single exposure fields do not require better stage performance, advanced lithography techniques which for example employ the so-called stitching technique, cannot be executed with sufficient success. Typically a repeatability of a few micrometers is insufficient for precise exposure field size calibration as well as for the stitching technique by subsequent exposure of adjacent exposure fields.

Functionality:
The two axes piezoelectric sub-stage assembly has been optimised for the use in SEM based EBL applications. It will be installed as a reversible sub-stage assembly on top of the original SEM stage. High precision encoders enable the individual single sub-stage positioning axes to attain a reproducibility of about 100 nm. Two axes repeatability is in the range of a few 100 nm and suitable for Mix & Match tasks.

Piezo electric sub-stage assembly in a FE SEM

The sub-stage enables stitching with typically sub micron accuracy (mean + 2 Sigma). The sub-stage assembly is controlled via proprietary Raith software drivers, to ensure an optimum integration level into the ELPHY Lithography Suite.

Four exposure fields with stitched patterns demonstrating sub micron stitching accuracy - red dotted line indicates exposure field boundary

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* The upper text is an extract of an application note, published by Raith August 2004.