Scholarly article on topic 'High Throughput Fabrication Process for Polymer MEMS using Molding and Printed Pattern Transfer'

High Throughput Fabrication Process for Polymer MEMS using Molding and Printed Pattern Transfer Academic research paper on "Materials engineering"

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Procedia Engineering
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Keywords
{polymer-MEMS / nano-imprinting / "vacuumless process" / "in mold decollation"}

Abstract of research paper on Materials engineering, author of scientific article — K. Kurihara, S. Takamatsua, T. Kobayashi, H. Takagi, R. Maeda

Abstract We propose a new MEMS fabrication method utilizing a mold replication process and a pattern transfer on the screen-printed film. The polymer MEMS device was fabricated in fabrication characteristic with a high-throughput and all vacuum less process. By combination of replication process and the screen-printed film with a stacking layer of silver electrode ink/ polymer-piezoelectric PVDF material/ silver electrode ink, piezoelectric cantilevers were fabricated at one replication process. The MEMS device was fabricated in replication time as short as 30 second. The signals were corresponded to the deformations of the cantilever. We consider that the process has a potential to attain MEMS device production in low-cost and wide device-area.

Academic research paper on topic "High Throughput Fabrication Process for Polymer MEMS using Molding and Printed Pattern Transfer"

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Procedia Engineering

ELSEVIER

Procedia Engineering 25 (2011) 876 - 879

www.elsevier.com/loeate/procedia

Proc. Eurosansors XXV, Saptambar 4-7, 2811, Athens, Graaca

High Throughput Fabrication Process for Polymer MEMS using Molding and Printed Pattern Transfer

K. Kuriharaa, S. Takamatsua, T. Kobayashia, H. Takagia and R. Maedaa

a National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan

We propose a new MEMS fabrication method utilizing a mold replication process and a pattern transfer on the screen-printed film. The polymer MEMS device was fabricated in fabrication characteristic with a high-throughput and all vacuum less process. By combination of replication process and the screen-printed film with a stacking layer of silver electrode ink/ polymer-piezoelectric PVDF material/ silver electrode ink, piezoelectric cantilevers were fabricated at one replication process. The MEMS device was fabricated in replication time as short as 30 second. The signals were corresponded to the deformations of the cantilever. We consider that the process has a potential to attain MEMS device production in low-cost and wide device-area.

© 2011 Published by Elsevier Ltd.

Keywords: polymer-MEMS, nano-imprinting, vacuumless process, in mold decollation

l.Introduction

MEMS device is important part to produce the new concept of application such as mobile phone, car-electronics, mobile projector and so on. The devices are basically produced by semiconductor process, which require the high-cost apparatus and many process steps such as lithography, a thin-film deposition and an etching. Therefore, the fabrication cost is one of problematic point to leach to new concept of MEMS application. From the reason, alternative fabrication method is required to allow the low-cost wide-area MEMS devices. To overcome such cost, size and structure-limitation, the devices based on polymer materials have been developed [1-3]. The polymer-based device is expected to realize low-cost wide-area fabrication because of easily produced. However, the process still contained the vacuum processes such as electrode deposition and ICP-RIE etching and the device size and structure were still limited. To resolve such problems, X. Y. Liu et al. have been proposed new concept of MEMS fabrication

Abstract

1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.12.215

method by electrode printing and paper-based membrane [4]. The fabrication concept was attained low-cost and high-throughput fabrication due to the vacuumless process. In addition, there is a possibility to attain wide-area MEMS devices. Therefore, if the fabrication concept could form the 3-dimensional MEMS membrane by vacuumless process, the new concept of MEMS devices could be produced. In this paper, we propose a new fabrication concept utilized a mold replication process and a pattern transfer process from the printed functional layer in order to form the 3-dimensional MEMS membrane.

2. MEMS Fabrication Concept by replication and pattern transfer process

Figure 1 shows the fabrication concept of the MEMS devices utilizing the metallic mold and printed functional film. The fabrication concept employs in mold decollation (IMD) techniques for MEMS device fabrication. IMD techniques were widely employed for production of customer electronic [5]. The mold is employed for The 3-dimentional MEMS membrane formation. The shape of the mold is reversed from structure of the MEMS membrane. The mold could be fabricated by conventional semiconductor process or machining tool. In contrast, the film is employed for functional layer transportation to MEMS membrane while the replication process. The film was consisted with a functional layer, removal layer and the substrate film. The functional layers with an electrode ink and a piezoelectric material are printed by a screen-printing or a gravies-printing method. In the replication step, the fabrication concept could be adapted replication method of nano-imprinting method, injection molding method

Fig. 1: Concept of the MEMS device fabrication by mold replication and pattern transfer process 3. MEMS Fabrication by UV nano-imprinting method

Fig. 2 shows the details of developed fabrication process using UV nano-imprinting method. At first, the mold and the printed functional film was prepared. The mold was fabricated by fine machining process. in contrast, the film was printed by screen printing method. The stacking layer on the film was consisted with the removal layer/ a silver ink / a piezoelectric PVDF / a silver ink as shown in fig.3. For the printing process, the electrode and polymer-piezoelectric material was form by all vacuumless process and the method achieve wide-area and low-cost fabrication. Next, the mold was filled with a UV resin, and capped by the film then UV light was irradiated. The irradiation time was evaluated to be about 30 second. After polymer solidification, the film was separated from the mold. Then, the functional layer on the film was transferred onto the MEMS membrane.

K Kurihara et al./Procedia Engineering25(2011) 822- 879

Fig. 2:Polymer MEMS fabrication process by Fig. 3: Film with functional layers prepared by mold replication and pattern transfer screen-printing

4. Results and discussion

Figure 4 shows a one of example of the fabricated MEMS structure. Since the fabrication process was employed the mold replication process and the film with functional layer, the 3-dimentional MEMS membrane was allowed by only one replication process. Figure 4 (a) and (b) shows an optical mirror and a cantilever, respectively. In the case of the optical mirror as shown in fig.4 (a), the area for mirror was 5x5 mm2. The thickness of the mirror was 500 ^m. The width of the spring was 300 ^m and the thickness was 50 ^m. In the case of the cantilever as shown in fig.4 (b), the cantilever part of the width and the length were 2 mm and 6 mm, respectively, and the cantilever part of the thickness was 50 ^m. The weight at the end of the cantilever had a shape of a spherical lens with radius of 500 ^m. Using the film with the functional layer of silver-ink/ PVDF/ silver-ink, the functional layer was transferred to MEMS membrane. Thus, the several sharp of the 3-dimentional MEMS structure was allowed by replication process.

Fig. 4: Fabricated MEMS devices by mold cantilever with a lens.

Figure 5 shows the resonant frequency characteristic of the cantilever device as shown fig.4 (b). A signal was swept from 1 to 500 Hz. The applied voltage was varied from 25 to 130 V. A resonant frequency was evaluated to be 212.5 Hz and the Q factor was estimated to be 13.8 when the thickness of the cantilever was 50 ^m. when changing the shape of mold structure, the thickness of cantilever was decreased to 30 ^m. then, the resonant frequency was decreased to be 106 Hz. Thus, the resonance frequency could be controlled by sharp of mold structure. Figure 6 shows the transitional charge output when the sensor was flicked. Signals corresponding to the deformations of the cantilever were observed. We consider that it can be applied to the energy harvesting or touch sensor devices. In conclusion, MEMS devices were fabricated by mold replication process only, and also the fabrication method was attained in all vacuumless condition. We believe that new MEMS applications will be emerge by the developed low-cost fabrication process.

0.15 0.13 0.11

---ov ----25V -65 V -------IOOV -130V -

\ j JAW

100 200 300 400

Frequency (Hz)

lou ched lou ched » 31.6 pQ ! V r

> is r > r f

200 ms

Time (ms)

Fig. 5: Resonance frequency property when the voltage signal was swept from 0 Hz to 500 Hz.

Fig. 6: Transitional charge output when the sensor was flicked.

Acknowledgements

This research is granted by the Japan Society for the Promotion of Science (JSPS) through the "Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program)," initiated by the Council for Science and Technology Policy (CSTP).

References

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Vol.11 pp.2189-2196, 2011

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