s1_Nanoprinting in Metal and Ceramics

Nanoprinting in Metal and Ceramics

S. W. Pang, W. H. Juan, J. A. Bride, S. Baskaran, N. Taylor, J. W. Halloran, and M. O’Donnell

University of Michigan, Ann Arbor, Michigan 48109-2122, USA

T. Tamamura, M. Nakao, and A. Ozawa
NTT, Atsugi, 243-01, Japan

H. Masuda

Tokyo Metropolitan University, Tokyo, 192-03, Japan

Nanostructures in Al were generated by printing with hard SiC molds. This nano-printing technology replaces the lithography and the etching or deposition processes to produce patterns directly in metal. Dots, short lines, and long lines were formed in the SiC molds by electron beam lithography and reactive ion etching (RIE). High aspect ratio features as small as 40 nm with depth up to 840 nm were patterned in the SiC molds. By pressing the SiC mold onto the Al substrate at room temperature, nanostructures in the SiC mold were reproduced accurately and uniformly in Al. Large arrays of nanostructures down to 40 nm were printed in Al with similar results for dots, short lines, and long lines. Using atomic force microscopy to analyze the cross sections of the SiC molds and printed Al nanostructures, depth dependence on feature size was observed. This nano-printing technology simplifies the processes for generating nanostructures with high throughput and high uniformity.

We have fabricated ceria-zirconia ceramics by making simple surface impressions onto soft ceramic green tapes using a plasma-etched polyimide pattern as a micromold. Closely spaced arrays of 25-µm-high lines could be fabricated having widths as fine as 9 µm. Smaller lines adhered to the polyimide mold. Features as fine as 4 µm can be made as isolated lines. This method should be applicable for micromolding any ceramic material available as a sufficiently tine powder.

Electron beam lithography and RIE were used to generate patterns in the SiC molds. Figure 1 shows arrays of dots defined and etched in SiC. The etch depth was 800 nm for 100 nm wide dots, resulting in dots with high aspect ratio of 8:1 in SiC.

Figure 1. Scanning electron micrograph of dots formed in the SiC molds. The dots were 800 nm deep and 100 nm wide.

To print directly on the Al substrate, the SiC mold was placed upside down on the Al and a hydraulic press was used to press the two together at room temperature. Figure 2 shows uniform array of 40 nm dots printed on Al. A pressure of 1 ton for 3 min over the 6x7 mm² SiC mold was used for nanoprinting.

Figure 2. 40 nm dots printed in Al using 1 ton pressure for 3 min. The area of the SiC molds was 42 mm².

The printed feature size and depth in Al were analyzed by atomic force microscopy. The printed depth in Al is shown in Figure 3 for various spacing widths. SiC molds with etch depths of 230, 400, and 840 nm were used for printing.

Figure 3. Printed Al depth as a function of feature spacing for SiC molds with depths of 230, 400, and 840 nm.

Figure 4 is the ceramic replica of the polyimide test pattern, which resulted in ceramic lines, varying from 7.5 to 22 µm wide, separated by 7 µm spaces.

Figure 4. Ceria-zirconia ceramic replica of the polyimide test pattern, after sintering at 1500 ^oC.

Figure 5 shows a 9-µm-tall wall 4 µm wide structure in ceria-zirconia with smooth surface and vertical sidewall.

Figure 5. Isolated wall of ceria-zirconia, 4 µm wide by 9 µm tall, micromolded from a polyimide pattern.

References

Last Updated: November 19, 2007

E-Mail: pang@umich.edu

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