There are largely two technologies for fabricating a nano pattern on a substrate. One is electronic beam lithography in which lithography is performed using an electronic beam, followed by etching. The other is imprinting in which a nano pattern is transferred onto a substrate using a stamp.
In the electronic beam lithography, mainly, a nanometer pattern is formed on an electronic resist (ER) and then etched to fabricate a final pattern. Meanwhile, in the imprinting, an organic nano pattern is formed on the substrate using a stamp made of silicon or crystal. The substrate for forming the pattern thereon is limited to a rigid substrate such as a semiconductor or glass substrate. This is because the rigid substrate is not deformed or wrecked during etching or heat treatment.
Of the aforesaid technologies, the electronic beam lithography necessarily entails heat treatment due to characteristics of the electron resist (ER). Therefore, this technology does not allow use of a plastic sheet made of e.g., polymer having a thickness of 1000 micro meter or less.
Also, in the case of imprinting, mostly, the substrate needs to be very superior in surface roughness to have a nanometer pattern formed thereon, even though there may be some differences depending on the type of equipment.
Accordingly, a problem with the imprinting is that the nano pattern cannot be formed on a substrate having a thickness less than a predetermined level. For example, in a case where Imprio series of MII corp., is employed, a substrate having a surface roughness of 10 micrometer or less does not ensure a nano pattern to be formed stably and repeatedly.
Consequently, the nano pattern cannot be directly imprinted on a plastic substrate whose surface roughness is relatively higher than the semiconductor substrate or glass substrate, where the nanao pattern can be formed.
However, the nano pattern may have to be formed on the plastic substrate. Here, as the most common method, the nano pattern may be formed by one of the aforesaid two technologies, that is, electronic beam lithography for forming the nano pattern on the semiconductor substrate made of e.g., silicon or the imprinting.
Thereafter, with the semiconductor substrate serving as a master, the plastic substrate is heated to a melting point or more to be melted. Then, the melted substrate is poured into the master to form a pattern. Subsequently, temperature is lowered and the master is etched or destroyed to fabricate a nano pattern on the plastic substrate.
Alternatively, another metal master having a pattern reversed with respect to that of the pre-made master is manufactured by electroplating the pre-made master with a metal such as Ni. Then in an identical process as above, a plastic substrate is heated and melted to be poured into the metal master, thereby forming a pattern. Subsequently, the metal master is cooled, and then etched and destroyed to form a nano pattern. A process of forming the nano pattern on the plastic substrate by metal mold injection as described above is not cost-efficient due to considerably high manufacturing costs of a metal mold. Besides, the molding process involves a heating process to require expensive molding equipment, thereby increasing manufacturing and maintenance costs.