Fabrication characteristics of a line-and-space pattern and a dot pattern on a roll mold by using electron-beam lithography

Abstract

IntroductionNanoscale fabrication techniques with a high throughput are needed for the low-cost fabrication of devices of the next generation. One such technique is ultraviolet (UV) nanoimprint lithography (UVNIL) (Haisma et al., 1996), which uses a mold with nanopatterns in conjunction with a UV-curable resin. The process of UVNIL is simple: first, the UV-curable resin is dropped onto a mold and pressed against a transfer substrate. Secondly, the resin is cured by exposure to UV light. Consequently, either the mold or the substrate must be transparent. The mold is then released from the substrate, leaving a duplicate of the nanopattern on the transfer substrate. By means of these simple steps, UVNIL can be used to fabricate nanoscale patterns.Roll-to-roll UVNIL (RTR-UVNIL) (Mikami et al., 1994;Ahn et al., 2006;Ahn and Guo, 2008), in which a roll mold is used, has the potential for even greater throughput, because in RTR-UVNIL, the nanopattern can be transferred continuously at high speeds; for example, Yoshikawa et al. (2013) achieved a speed of 18 m/min. Furthermore, the force necessary to release the mold from the substrate in the RTR-UVNIL process is smaller than that in a planar NIL process; furthermore, the roll mold is in linear contact with the substrate, whereas large-scale planar NIL processes require high pressures and heavy machinery. Patterns on large areas can therefore be produced more efficiently by RTR-UVNIL. However, difficulties exist in the fabrication of roll molds.A roll mold for RTR-UVNIL is typically prepared by attaching planar replica molds onto a roll substrate. This produces a roll mold with seams that reduce the yield of the product. A seamless roll mold can be fabricated by mechanical or laser cutting (Sekkat and Kawata, 2014), but it is difficult to achieve a resolution of less than 100 nm. Self-organized structures, such as those produced by anodic oxidation of aluminum (Masuda et al., 1997), have no seams, and fine pattern sizes can be fabricated by these techniques; however, it is difficult to produce patterns with a Abstract Roll-to-roll nanoimprint lithography (RTR-NIL) has received considerable attention because it permits large-area nanopatterning with both high resolution and high throughput. However, the application of RTR-NIL is restricted by difficulties in fabricating nanoscale roll molds. Seamless roll molds are especially desirable, because the presence of seams reduces the yield of the imprinted product. We have previously developed a technique producing seamless molds by direct writing with an electron beam onto a rotating cylindrical substrate. We have now developed a method for fabricating fine patterns on roll molds for RTR-NIL by using electron-beam lithography (EBL) with a positive-type electron-beam resist and an aluminum roll as a substrate, which is rotated in a scanning electron microscope. The electron beam is focused at a single point on the surface of the roll mold and the dot pattern is produced by switching the beam on and off. Dot and line-and-space p...

Fabrication System for Large-Area Seamless Nanopatterned Cylinder Mold Using the Spiral Laser Interference Exposure Method

“…In recent years, nanotechnology has developed rapidly with a focus on developing cost-effective methods for the fabrication of nanoscale patterns for large areas [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Nanoimprint lithography (NIL) is a low-cost and largearea processing method for fabricating nanopatterns.…”

“…The wrapping process inevitably results in a seam; consequently, it is difficult to implement a continuous roll-to-roll imprinting process. Hence, various researchers have studied the direct patterning process on cylinders without wrapping using electron beam lithography [6][7][8][9][10], photolithography [12][13][14], and ablation using a pulsed laser [15,16]. Electron beam lithography can produce precise nanopatterns; however, this process is implemented in a high-vacuum environment, which is expensive and technically difficult to establish.…”

Nanopatterning on the cylindrical surface using an E-beam pre-mapping algorithm

“…Careful tuning has also been investigated for application to various other materials, such as biological cells and soft polymers [8][9][10]. Figure 1 illustrates several milestone achievements of various lithography methodologies developed by utilizing many diverse aids, such as laser, x-ray, UV, near-field scanning optical microscopy, self-assemble monolayer, dip-pen, and so on [22][23][24][25][26][27][28][29][30]. Among them, and as recently achieving the reliable nanoscale patterning of sub-50 nm resolution [31][32][33][34][35], E-beam lithography has now been a primary workhorse in semiconductor device manufacturing that especially requires ultrafine pattering, for example, very large-scale integrated circuit (VLSI) production.…”