Nano-scale patterning using the roll typed UV-nanoimprint lithography tool

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Abstract

Nanoimprint lithography is a promising technology to produce sub-100 nm half-pitch features on silicon wafers. To achieve nano-imprinting process, nano-imprinting lithography equipment must have required some multi-functional units which are imprinting head, self-alignment wafer stage, overlay and alignment system for multi-layer process, stamp with sub-100 nm half-pitch patterns, and anti-vibration unit, etc. Although imprinting process has many advantages in terms of low cost, high throughput and reproducibility, these imprinting technologies have a limitation to increase imprinting area and imprinting tool sizes. Also, air entrap phenomenon which is generated between the stamp and the resist surfaces during imprinting process is getting important parameter in the press type imprinting process. In order to get over these limitations and the air entrap and to fabricate large area product, such as above 8 in. wafer, display unit and multi-functional device, roll typed UV-nanoimprint lithography tool are certainly necessary. In this study, the roll typed UV-nanoimprint lithography tool which is can be loaded PDMS (polydimethylsiloxane), polycarbonate and PET film as soft stamp, is proposed.

Introduction

The contact-based nanoimprint lithography, such as thermal and/or UV-nanoimprint, has been well known as one of the next generation lithography alternatives. The nanoimprint lithography technology has the advantages in terms of process simplicity, low cost, high replication fidelity, and relatively high throughput, i.e. allowable wafer per hour [1], [3]. Especially, the UV-nanoimprint lithography (UV-NIL) process has advantages of the short imprinting time, low imprinting pressure, room temperature, and high throughput on the Si wafer by means of single step imprint lithography process (S-SIL) using large sized stamp that is the same size as the wafer, and by step and flash imprint lithography process (S-FIL) using chip sized stamp [4], [5]. The thermal nanoimprint lithography (TH-NIL) process can be used to fabricate nanopatterns with high aspect ratio on the large area of 6 in. or less. However, it has disadvantages of high temperature, high pressure and long process time due to repeated heating and cooling processes to fabricate nanoscale patterns. Recently, to minimize heating and cooling processing time, new heating and cooling method is developing by some researchers. Molecular Imprint Inc. and Suss MicroTec’s imprint processes are classified into step and repeat imprint process. Obducat and EVG’s imprint process are classified into single step imprint process. In case of the press typed UV-NIL, there are some allowable imprint size limitations due to stamp size, allowable imprinting pressure and air entrap phenomenon which is generated between the stamp and the resist surfaces during imprinting process. Compare of this, the roll typed UV-NIL has comparatively not much limitations which are allowable imprinting area due to the flexible roll stamp, low imprinting pressure due to line contact between the stamp and the substrate, and the air entrap phenomenon. Especially, according to increase in demand large area imprinting process above 8 in. wafer, the roll typed UV-NIL tools are to become important issues. Hewlett–Packard and VTT are recently developing the roll typed imprinting process using metal stamp.

In this study, the roll typed UV-NIL process and equipment using the flexible transparent thin stamp with sub-100 nm patterns is proposed in order to fabricate nanoscale patterns on the Si and plastic substrates. In case of plastic substrate, relatively high throughput can be obtained by continuous imprinting process. The flexible transparent stamps, such as PDMS (polydimethylsiloxane), polycarbonate and PET film are fabricated by Ni master with 100 nm patterns using the thermal nanoimprint equipment. These stamps are set-up on the transparent quartz cylinder of the UV-NIL tools (ANT-6R) which is manufactured by KIMM.

Section snippets

Thermal and roll typed UV-nanoimprint lithography tools

The flexible PDMS and polycarbonate film stamps what is called replica are fabricated from Ni master stamp with 100–300 nm linewidth patterns using thermal nanoimprint lithography tool (ANT-6T) as shown in Fig. 1a. The thermal NIL process is performed at the substrate using the large size stamp that is the same size as the wafer on the thermal NIL. The thermal NIL tool consists of an imprinting head unit, a passive compliance supporter for round-type wafer and any rectangle stamps, two of hot

Experimental

In the first step, in order to fabricate flexible polycarbonate stamp for the roll typed UV-nanoimprint lithography tools, the Ni stamp with 100–300 nm for blue ray disc and polycarbonate film had been loaded on the thermal NIL tool (ANT-6T), and then thermal imprinting process are done under about 180 °C and 25 bar for 10 min. Then, to fabricate the flexible PDMS stamps, the viscous PDMS pre-polymer solution (Dow Corning DC-184) is poured on the Ni stamp for blue ray disc master, and covered with

Conclusions

According to increase in demand large area imprinting process above 8 in. wafer, the roll typed UV-NIL tools are to become important issues. In this study, the roll typed UV-NIL process and equipment using the flexible transparent thin stamp with sub-100 nm patterns is proposed in order to fabricate nanoscale patterns on the 5 in. Si and plastic substrates. The fabricated flexible transparent stamps, such as PDMS (polydimethyl-siloxane), polycarbonate and PET film are set-up on the transparent

Acknowledgement

This research was supported by Center for Nanoscale Mechatronics and Manufacturing (CNMM), one of the 21st Century Frontier Research Programs, which are supported by Ministry of Science and Technology, KOREA.

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