It is well known that photolithography method has been widely used to form a fine pattern on substrates. The photolithography has merits in that it enables to imprint fine patterns in an even and stable way, but it has to undergo several-step processes (resin coating, thermal treatment, light exposure, development, cleansing, etching, etc.). Those complicated processes require expensive equipments in each step, make it difficult to control because of the margin in each process, and consume huge processing time to form patterns. They eventually become major problems causing an increase in manufacturing costs and a reduction in productivity.
Of the several methods developed to overcome the limitations of the prior photolithography methods, imprint lithography has been acknowledged to be a next-generation lithography technology. The imprint lithography technology makes it possible to fabricate a fine structure in an inexpensive and effective way, in which a stamp embossed with a fine structure is placed on the surface of a resist which has been spin coated or dispensed onto a substrate and pressed to transfer the fine structure.
Early imprint technology used a method of applying high pressure to the surface of a substrate coated by the resist under high temperature of not less than glass transition temperature and then cooling down and separating it. While this method has advantages in that the process is comparatively easy and it uses inexpensive equipments, it still requires long processing time and high pressure. In particular, since it requires high temperature as well as high pressure, there is a possibility that the substrates may be damaged and separation between the molds and the substrates may be difficult.
In the case of a resin mold using polydimethylsiloxane (PDMS), which is a typical silicon-type polymeric elastomer used for the prior resin molds, it can be easily in even contact with a substrate surface to form a pattern thereon because polydimethylsiloxane is an elastomer, it can be readily separated from the substrate surface after the pattern is formed because polydimethylsiloxane shows low adhesion to the resist surface coated thereby owing to its low surface energy, and it makes easy the absorption of a solvent due to its high gas permeability resultant to its 3-dimensional mesh structure. However, it may be readily deformed due to its low mechanical intensity and further, it may be deformed by swelling even in general organic solvents due to its low chemical resistance and its release and wettability may be deteriorated so that it has considerable restrictions on the selection of polymers and solvents to be used for pattern formation.
Fluorine-type resins have been proposed to compensate the drawbacks of those silicon-type resins. However, while the fluorine-type resins show excellent chemical resistance, release performance, and mechanical properties, their applications are significantly restricted because of their reduced wettability due to excessive release performance, their low compatibility with other substances including silicon resins, low transmittance and low adhesion to supporting substrates.
Urethane or acryl resins used for the existing resin molds have considerably low chemical resistance and release performance and thus, their commercial applications are severely limited in terms of low durability and productivity for commercial use.
The existing resin molds were often subject to additional surface treatment subsequent to the resin mold formation so as to enhance their release performance, chemical resistance and wettability, but the physical property enhancement through those attempts did not last long or made no significant difference.
USPTO Backgrounds
USPTO Backgrounds