In the fabrication of electronic devices, optical components, storage components, bioelectronic components and the like, not only higher performance and further miniaturization are demanded, but also a reduction of the manufacture cost is required at the same time. Under the circumstances, the nanoimprint lithography (NIL) is highlighted since it can reduce the cost of micropatterning as compared with the conventional lithography processes. In the NIL process, a topological pattern is formed by mechanical means. Specifically a mold having a desired topological pattern on the surface is pressed to a resin layer of given thickness on a recipient substrate for thereby transferring the topological pattern on the mold to the resin layer. See Patent Document 1. The resin layer to which the topological pattern has been transferred by pressing is cured whereby the shape of the resin layer is retained. The cure may be implemented typically by UV cure and heat cure modes. In either mode, it is important to press the mold-forming substrate and the resin layer-bearing recipient substrate together while maintaining parallelism between them and providing a uniform pressure within the contact plane. The mold-forming substrate to be provided with a topological pattern is required to have a high shape precision. See Patent Document 2.
Mold-forming substrates used in the NIL process have different outer shapes including rectangular shape of 65 mm squares or 152 mm squares, and circular shape having a diameter of 50 mm, 100 mm, 150 mm or 200 mm, with a choice being made in accordance with the intended application. On the other hand, a region of the mold-forming substrate which plays the substantial mold role and on which a topological or protrusion/depression pattern is to be formed often has a smaller area (typically less than 4,000 mm2) than the outer shape and is generally situated around the center of the mold-forming substrate. In general, there is a tendency that as the feature size of a pattern to be transferred becomes finer, the area where the pattern is formed becomes smaller.
The reason is that as the pattern feature size becomes finer, the accuracies required for mold-to-recipient substrate parallelism and pressure uniformity become higher; and if the area where the pattern is formed is smaller, these accuracies can be increased. On the other hand, the tendency that the outer shape of the mold is larger than the region where the pattern is formed is accounted for by the process of manufacturing a NIL mold. The NIL mold manufacture process generally includes a step of depositing a metal film by sputtering, a lithography step using an EB writer for transferring a desired fine pattern to the metal film, and a step of dry etching the patterned metal film and the recipient substrate surface. From the aspects of economy and feasibility, these steps often utilize in a share manner those equipment used in the traditional lithography technology. Accordingly, the size of a mold-forming substrate loaded on these equipment inevitably corresponds to the size of substrates used in the traditional lithography technology, leading to the tendency that the outer shape of the NIL mold is sized larger than the region where the pattern is formed.
In recent years, the photo (UV) nanoimprint lithography encounters an increasing demand to provide a mold with a finer size pattern or more complex pattern for transfer. From such a demand and for the above-mentioned reason, the flatness of a mold-forming substrate, especially the flatness of a region which is provided with a pattern and plays the substantial mold role is critical. As the pattern to be transferred is of finer size or more complexity, a stronger possibility arises that unless the surface is fully flat, a misalignment may occur between the pattern during the mold manufacture and the pattern during the transfer step, leading to pattern errors.