**6. Acknowledgment**

332 Recent Advances in Nanofabrication Techniques and Applications

designed for use with the TIEGATM process as well as the LIGA process, PTFE was only exposed to the X-ray domain. Therefore, the etching rate and processing depth were low.

Because the PCT technique successfully provided PMMA 3-D structures, we adapted the PCT technique to expose PTFE while the stage was in motion. Fabrication of 3-D PTFE microstructures using other techniques has also been reported, including 3-D PMMA structures (Nakamura and Tabata, 2006; Nishi et al., 1999). Figure 23 shows 3-D PTFE structures fabricated using the PCT technique with a triangular mask pattern. Figure 23A shows a structure in which the PTFE surface temperature was 140°C, and Figure 23B shows a structure in which the PTFE surface temperature was 200°C. As shown in the figure, higher PTFE temperatures correspond to enhanced surface roughness. Figure 24 shows the target forms and 3-D PTFE structures fabricated using the PCT technique with other mask

(A) (B)

(A) (B)

Fig. 23. 3-D PTFE structures fabricated using the PCT technique with a triangular mask pattern; (A) PTFE surface temperature was 140°C; and (B) PTFE surface temperature was

Fig. 24. Target forms and 3-D PTFE structures fabricated using the PCT technique with other mask patterns; (A) is utilizing sine-curved mask pattern; and (B) is utilizing semicircular

MEMS devices have attracted much attention, and further studies are needed to realize their full potential. In fabrication technology, an elemental technology, microfabrication, developed primarily using a semiconductor process, is in high demand. Recently, MEMS devices have diversified, and microfabrication technologies for the production of highaspect-ratio and 3-D structures are in demand. This article described the fabrication of 3-D

**4.4 3-D Fabrication of PTFE** 

patterns.

200°C

mask pattern

**5. Conclusions** 

microstructures utilizing SR lithography.

We would like to express our sincere gratitude to our supervisor, Prof. Toshiaki Ohta who is head of SR Center of Ritsumeikan University.

We would like to thank Dr. Hiroshi Ueno, Dr. Sommawan Khumpuang, Mr. Kazuya Fujioka, Mr. Shinya Fujinawa, and Mr. Shunsuke Kajita for providing us with useful data. We would like to thank Dr. Yasukazu Yamamoto and Mr. Hiroyuki Ikeda for their technical assistance.
