Asymmetric fluid-structure dynamics in nanoscale imprint lithography

template and the wafer. As a part of the research for this thesis, an active stagetest bed is being developed. The motion capability of the active stage system isbased on the ideal Revolute Prismatic Ball (RPB) stage. The RPB platform hasbeen thoroughly analyzed [Johnson 1999].The systems that make up this test bed are 1) a wafer stage assembly, 2)template orientation stages 3) a micro-fluidic etch barrier dispensing system, 4) ahigh-resolution actuation system, 5) a gap sensing/orientation measurementsystem, and 6) a force measurement system. Each system must be designed orpurchased as a modular component so that design modifications can beimplemented or customized within reasonable costs and time constraints. Thefollowing discussion will provide some insight into the design requirements of thesubsystems relevant to this research. The details of the gap sensing theory andimplementation are given in chapter 4. A complete discussion of the entire activestage project is beyond the scope of this thesis, as the active stage test bed iscurrently in its infancy stage.3.2.1 Wafer Stage AssemblyThe wafer stage must bring the wafer substrate to within the motion rangeof the DC Mike motor and hold the wafer in place during imprinting. The waferchuck must hold the wafer with minimal distortion by providing a uniformpressure across the backside of the wafer. Current wafer manufacturers providewafers with low frequency height variations across their diameter. Using a flatvacuum wafer chuck with uniform pressure across the supporting surface canminimize these oscillations. Figure 3.1 shows the current embodiment of thewafer stage assembly. Air solenoids lift the wafer to within the motion range ofthe actuation system.43