Dual field nano precision overlay
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Currently, the imprint lithography steppers are designed to only pattern one field of 26 x 33 mm at a time. This choice is based on the desire to mix-and-match to the standard optical lithography tools whose field size is also 26 x 33 mm. Throughput can be increased if more than one field can be imprinted simultaneously. The problem with adding a field to the imprinting template is that each field has overlay errors associated with it that are created when the template is manufactured and when the corresponding prior field is manufactured on the wafer. The current process is able to correct these template and wafer overlay errors using a precision stage and actuators that elastically deform the template. The same method cannot be used when there are two fields because the fields are not independent and interact with each other. Correcting the errors in one of the fields tend to increase the error in the second field. vii In this thesis, a new control method has been created to account for the dependent motion. A new template concept was also created to try to limit the interaction between the two fields. The new control algorithm was tested in simulation to see if it could correct the current 1-field setup as well as the new concept of having more than one field on a template. The control algorithm was also used to test applications where the overlay errors in only one direction need to be corrected. The control algorithm was tested on a solid single field template, the baseline case, and was able to achieve 1.3 nm overlay, which is consistent with the current method. The algorithm was then tested on the dual field concepts. The range of alignment errors needed to get 5 nm overlay are too tight for current manufacturing but the compliant concept did have more relaxed ranges than the solid dual field template. With more research, the compliant template concept might be changed to allow for wider ranges. The tests with correction in only one direction had promising data that should be investigated further.