Optical system for use in stage control
View Patent ↗Imprint lithography benefits from precise alignment between a template and a substrate during imprinting. A moiré signal resulting from indicia on the template and the substrate are acquired by a system comprising a line-scan camera and a digital micromirror device (DMD) which provides a high bandwidth, low-latency signal. Once acquired, the moiré signal may be used directly to align the template and the substrate without need for discrete position/angle encoders.
1. A method of aligning a template and a substrate, the method comprising:
scanning the substrate through the template with a digital micromirror device (DMD), wherein the substrate and the template have corresponding features;
measuring a moiré signal resulting from interaction of light between the features on the substrate and the template; and
determining a misalignment based on the measured moiré signal,
wherein the DMD directs light from an area on the substrate, the template, or both to a detector element.
2. The method of claim 1 further comprising adjusting alignment between the substrate and the template in response to the determined misalignment.
3. The method of claim 1 wherein the DMD directs light from a plurality of non-contiguous areas on the substrate to a plurality of detector elements such that each of the non-contiguous areas corresponds to one detector element.
4. The method of claim 1 wherein the alignment comprises moving the template or the substrate or both in a plane comprising two orthogonal axes, rotating about an axis orthogonal to the plane, or both.
5. An imprint lithography system, the system comprising:
a template configured to render an imprint and comprising alignment indicia;
a substrate configurable to replicate the imprint and comprising alignment indicia;
an illuminator configured to illuminate the template and the substrate;
a detector; and
a digital micro-mirror device comprising a plurality of individually addressable micro-mirrors configurable to reflect at least a portion of light from the template and the substrate to the detector, wherein the light comprises a moiré pattern resulting from an interaction between the alignment indicia of the template and the alignment indicia of the substrate.
6. The system of claim 5 wherein the detector comprises a plurality of detection elements and light from each of a plurality of non-contiguous areas on the template, or the substrate, or both is directed to separate detection elements.
7. The system of claim 5 wherein the moiré pattern is used as an in situ measurement of a relative alignment error between the template and the substrate.
8. The system of claim 5 wherein the substrate is substantially transparent to the light.
9. The system of claim 5 further comprising:
an alignment controller configured to output displacement information and a current position based on the moiré pattern of a stage upon which the substrate is mounted; and
a stage controller configured to accept the alignment controller output and control the stage.