Dielectric Properties of Multi-Layer High-K Polymer Composite Films
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Dielectric Properties of Multi-layer High-K Polymer Composite Films Wataru Sakai and C. K. Chiang Polymers Division, National Institute of Standards and Technology Gaithersburg, Maryland 20899-8541, US ABSTRACT The electrical properties of thin polymer films are key parameters in the design of both smaller and faster circuit devices in the microelectronics industry. In this study, we made a three-layer film structure, ABA’, to investigate the dielectric interaction between two high-K dielectric polymer thin films , A and A’, as a function of the thickness of the middle B layer. The Cole-Cole plot showed clear changes with the thickness of the middle B layer. The total capacitances were evaluated with a simple serial three capacitances model. This ABA' structure is thought to be very useful for studying mechanical and thermal properties of thin polymer film system. INTRODUCTION High dielectric constant (high-K) polymer films are crucial for the development of high-speed wireless communication equipment. High-K insulating films are particularly useful for distributing and storing the electric energy in the vicinity of devices operated at high frequencies (low RC time constant). Recently, Popielarz et al showed an empirical logarithmic mixing rule for two-phase composite materials in which high-K ceramic fillers are dispersed in a polymer matrix [1]. As the volume concentration of the high-K filler increased, the effective dielectric constant increased in the frequency region, 102 Hz to 1010 Hz. These phenomena were explained by sum of serial or parallel capacitance model and the rule has not been elucidated clearly. It is thought that the design and modify of interfacial interaction between these high-K particles may help in promote the dielectric constant of advanced polymer composites. [2]. In this study, we made a simple three-layered structure, ABA’, to investigate the dielectric interaction between two high-K dielectric polymer thin films using broad band dielectric measurement from 10-3 Hz to 107 Hz. The middle B layer of low-K polymer served as an interface layer to control the distance. Experimental results were also compared with the theoretical simulation and discussed. Since multi-layered polymer films are also a basic structure for many device applications, this study is also useful to understand the fundamental material science that occurs at thin film interfaces [3]. MATERIALS
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The high-K polymer for layer A and A’ was a cyanide resin (CR-S, Shin Etsu Chemical Co. Ltd) while low -K B layer was poly(styrene) (PSt, NIST SRM, No.705a) [4]. These polymers were used as received, without fur ther purification. The dielectric constants for CR-S and PSt were 20 and 2.5 at 1 kHz at 25°C, respectively.
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R = CH 2CH 2 CN or H
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EXPERIMENTS Sample Preparation Figure 1 shows the layer structure of sample. First, the bottom aluminum electrode was put on the glass substrate by vacuum deposition. Second, the first CR-S layer (A) was deposit
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