1. Field of the Invention
The present invention relates to nanoimprint technology, and more particularly, to a method of fabricating a nanoimprint mold which is essential to nanoimprint technology.
2. Description of the Related Art
Representative nanolithographic techniques for creating nanostructures with dimensions of less than 100 nm include electron beam (E-beam) lithography (EBL), focused ion beam lithography (FIBL), nanoimprint lithography (NIL), and deep UV (DUV) lithography. Recently, next-generation lithographic techniques such as extreme UV (EUV) lithography, X-ray lithography, hologram lithography, and laser interference lithography (LIL) have been developed.
EBL or FIBL with a resolution of several nanometers (nm) has disadvantages in that accelerated electrons or ions are greatly affected by the conductivity or structure of a substrate, and throughput is low due to raster or vector scanning.
DUV or EUV lithography which is mainly used in a semiconductor fabrication process and can generate wafer-scale patterns over a large area in a single step has disadvantages in that manufacturing equipment is expensive, costs of a photomask are high, and it is difficult to use a flexible substrate or material which is affected by a developer used for pattern formation after exposure.
X-ray lithography which is considered as next generation lithography can provide a diffraction limited resolution of several nanometers, which is higher than that of optical lithography and similar to that of the EBL or FIBL. However, the X-ray lithography is not suitable for forming patterns over a large area because it uses a very large synchrotron as an X-ray source and it is difficult to increase the size of the X-ray source.
LIL which is often used in forming repetitive patterns such as gratings can be easily applied to a large area, is rarely affected by the characteristics of a substrate, and can be achieved at low cost. Despite the advantages, the LIL cannot be widely used because it is difficult to form various patterns and requires strict overlay accuracy while performing a process of forming multi-layers.
Imprint lithography for forming patterns using a mold is largely divided into a thermal method and a UV curing method. The imprint lithography can be applied to a general semiconductor substrate, such as a silicon substrate, a plastic substrate requiring a low temperature process, and also to a non-conductive glass or quartz substrate.
Recently developed nanoimprint lithography has become an attractive alternative to hot embossing lithography because of its easy control of pressure or temperature, and particularly, UV nanoimprint lithography can produce patterns even at room temperature and under normal pressure.
However, the UV nanoimprint lithography requires a transparent substrate or mold which is generally formed of quartz. It is difficult to form sub-100 nm fine patterns over a large area of the quartz mold or substrate, thereby increasing manufacturing costs.