Evaluation of press-uniformity using a pressure sensitive film and calculation of wafer distortions caused by mold press in imprint lithography

Imprint lithography is expected to become a cost-effective technology for manufacturing future devices with nanometer structure (Chou et al, 1995). Not only high resolution but reliable patterning over a large area is crucial to make this technology practical in industrial use. However, there is little information on patterning quality in terms of critical dimension (CD) and pattern placement (PP) over all of the imprint area (Scheer et al, 1998), because CD and PP measurements of imprinted patterns in a large area are very difficult when those patterns consist of very fine structures with relatively small height. A new method using a pressure sensitive film that changes color corresponding to the strength of pressure is proposed to simply evaluate the uniformity of imprint pressure across an imprint area instead of measuring CD and/or height of imprinted patterns. In this presentation, deterioration factors of press-uniformity are investigated by measuring color density at multiple points of the pressed film and their mitigation factors are discussed. Simulation using a finite element method also clarifies that wafer distortions caused by an imprint pressure applied to the limited area of a wafer should not be considered negligible for accurate CD and PP control.