Nanomechanical characterization of polymer using atomic force microscopy and nanoindentation

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Nanomechanical characterization of polymer using atomic force

microscopy and nanoindentation

Te-Hua Fang

a

, Win-Jin Chang

b,

*, Sung-Lin Tsai

a

a_{Department of Mechanical Engineering, Southern Taiwan University of Technology, Tainan 710, Taiwan, ROC} b_{Department of Mechanical Engineering, Kun-Shan University of Technology, Tainan 710, Taiwan, ROC}

Received 1 July 2004; received in revised form 23 September 2004; accepted 6 October 2004 Available online 2 December 2004

Abstract

The nanomechanical characteristics of polycarbonate (PC) polymer were investigated by atomic force microscope (AFM) and nanoindentation. Scratching, wear properties, hardness and Young’s modulus were obtained. The relationships between scribing feed and speed, surface depth and roughness and applied load were also investigated. The results indicated that as the applied load was increased, the furrow depth and the surface roughness increased. When the scribing feed was increased, the depth and roughness decreased. Increasing the furrow speed also decreased the surface roughness. The applied load is more significant than the scribing speed on the material removal rate. In addition, the Young’s modulus and hardness of the polycarbonate material were 1.8 and 0.2 GPa, respectively.

Keywords: Hardness; Nanotribology; Atomic force microscopy; Nanoindentation; Polymer

1. Introduction

Since atomic force microscope (AFM) development in 1986[1], it has become a very powerful tool for studying the surface characterization of diverse materials on a micro- and nanoscale level [2–4]. Nowadays, electronic elements are continuing to become shorter and smaller in their dimen-sions. The conventional optical and electron-beam litho-graphy technique for processing the task becomes more and more difficult, due to the constraint of the physical limitations. Therefore, the development of the next generation of lithography techniques is very important to the microelectronic engineering research and development field.

AFM-base nano-lithography technique has a very high potential for nanofabrication. The main merit of the AFM-based lithographic technique is that, the machined scale of the structure is solely determined by the geometry of the AFM probe[5,6]. In addition, the machining resolution of the nanostructure produced by this technique is superior to

other conventional lithography techniques[7,8]. The AFM-based lithographic technique can bring the resolution of fabrication technology to a nano-meter scale and not only help support the research on low-dimensional physics but also the fabrication of electronic devices such as nano-wires, nano-dots and single electron transistors [9]. To increase the understanding of the AFM-based lithogra-phy technique, it is necessary to perform further research.

In order to study the AFM-based lithography technique and to understand the machining characteristics of this method, scribing experiments and nanoindentation tests were conducted on polycarbonate materials [10]. The working parameters included the scribing feed and the speed, the load applied to the cantilever, and their effects on the surface depth, the surface roughness and the material removal rate. In addition, the hardness and Young’s modulus of the material were also measured.

2. Experimental procedure

Line and multiple furrows scribing was performed on the specimens and then the topographic properties of

Microelectronics Journal 36 (2005) 55–59

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the applied load, scribing speed, scribing feed, surface depth and roughness were investigated. The hardness and Young’s modulus values of the polycarbonate(PC) material were also measured. Based on this study, the following results were obtained:

1. Increasing the furrow speed will decrease the furrow depth, while increasing the applied load will increase the depth.

2. Increasing the furrow speed or applied load also increased the surface roughness.

3. The material removal rate during furrowing is primarily influenced by the applied load instead of the furrow speed.

4. As the scribing feed was increased, the furrow depth and the surface roughness decreased.

5. Young’s modulus and hardness of a polycarbonate PC material were 1.8 and 0.2 GPa, respectively, and are independent of the indentation depth or the applied load.

Acknowledgements

This work was partially supported by the National Science Council of Taiwan, under Grant Nos. NSC91-2218-E218-001 and NSC91-2212-E-218-007.

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[12] T.H. Fang, W.J. Chang, Microelectron. Eng. 65 (2003) 231. Fig. 8. The relationship between Young’s modulus and hardness at different

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