Smart

Motion

SmartMotion technology was developed to provide a solution to avoid stitching errors through stitch-free exposure on the fly.

Introduction

Some lithography applications, especially the writing of optical devices such as waveguides or gratings, are extremely sensitive to minimal unsteadiness or roughness within the pattern. Even the tiniest hint of a noticeable stitch field border can cause significant degradation in device performance. Despite the use of a highly precise laser stage and sophisticated write field corrections, very small stitching and transition errors at write field boundaries cannot be completely eliminated.

Writing continuously with (sub) nanometer precision requires very accurate and smooth mechanical motion

Key features

Benefits for applications

Applicable with two different writing modes (FBMS / MBMS) in our electron beam lithography and FIB systems

Writing of large photonic devices as optical waveguides

Stitch-free FBMS exposure paths can be several millimeters to centimeters long, while maintaining lateral dimensions from below 20 nm to some micrometers with minimum line edge roughness and high
uniformity.

Ideal for periodic patterns fabrication

MBMS supports patterning strip-shaped periodic structures such as gratings and lattices with ultrafine pitch adjustment. Optical devices like elongated Bragg gratings or photonic crystal waveguides benefit from the absence of classical stitching boundaries in this writing mode.

Fully integrated into Nanosuite software

Both exposure modes are supported by the Nanosuite Software and fully compatible with the built-in GDSII / CAD file editor.

Efficiency

Throughput of large area patterning can be increased, as acceleration and settling times are avoided due to the continuous process and movement of the stage.

How it works

Precision in motion: Achieving (sub) nanometer writing accuracy

Successful writing with continuously moving stage down to (sub) nanometer precision requires very accurate and smooth mechanical motion, extremely fast path calculations, as well as instant corrections of any following error. Therefore, a laser stage based on RAITH’s UltraPositioning technology is combined with a very fast motion controller specifically developed for this purpose. The motion controller calculates a two-dimensional, continuous trajectory with stable velocity and drives the stage in closed-loop control based on interferometer feedback.

Highly accurate linear bearings and a special drive chain ensure very smooth and continuous movement of the laser stage and the sample. Disturbances and deviations that cannot be mechanically corrected in time due to the inertia of the stage are instantly compensated by beam deflection, called beam tracking. This is realized by a direct interface between the motion controller and pattern generator, which is also used for patterning synchronization.

Advanced beam tracking for enhanced patterning control

Beam Tracking continuously superposes further beam deflections depending on the dedicated exposure mode.

FBMS: Fixed Beam and Moving Stage

In FBMS mode, the width of the path is defined by dynamic beam expansion. The beam remains virtually stationary while the stage underneath follows arbitrary shaped paths of the desired patterns.

MBMS: Modulated Beam and Moving Stage

For MBMS exposures, the stage is driving straight paths and a feedforward correction is applied to the pattering. The (repetitive periodic) beam movement is defined such that the combination of patterning and synchronized continuous movement of the laser interferometer stage results in the designed periodic structures. The MBMS implementation allows excellent pitch control by means of stage velocity control in combination with beam deflection.