Studies of Parylene C Microfibrous Thin Films Electrical Properties

Abstract

Parylene C is known for its flexibility, transparency, biocompatibility, and dielectric reliability. Parylene C is, hence, researched for use as a gate dielectric in transistors and capacitors for flexible electronics as well as for nano/microelectromechanical system applications [1-3]. In this study, we use metal–insulator–metal (MIM) capacitor structures to examine the electrical characteristics of columnar microfibrous thin films (µFTFs) of Parylene C prepared using oblique-angle physicochemical deposition [4,5], whereby a collimated vapor Parylene C is directed at an angle χv with respect to the exposed face of a planar substrate. The values of χv used were 30°, 60°, and 90°. We found that the low-frequency relative permittivity of the columnar µFTF increases with χv. This is explained in terms of the porosity as a function of χv, the porosity being higher for lower χv. Leakage current and charge deep-level transient spectroscopy (Q-DLTS) measurements at temperatures in the 230–470 K range and at frequencies in the 1–1000 kHz range were used to evaluate the dielectric integrity of the columnar µFTFs. Observed capacitance transients and Q-DLTS peaks in temperature were analyzed to uncover carrier traps located in the Parylene C bulk and at the metal/Parylene C interfaces in the MIM structures. The variations of DC and AC conductivities can be explained in terms of charge transport mechanisms involving thermionic emission and electron hopping. W. T. Wondmagegn, N. T. Satyala, I. Mejia-Silva, D. Mao, S. Gowrisanker, H. N. Alshareef, H. J. Stiegler, M. A. Quevedo–Lopez, and B. E. Gnade, Thin Solid Films, 519(13), 4313–4318 (2011).T. Trantidou, D. J. Payne, V. Tsiligkiridis, Y.-C., Chang, C. Toumazou, and T. Prodromakis, Sensors and Actuators B: Chemical, 186(1), 1–8 (2013).B. Park B., K-J. Im, K. Cho, and S. Kim, Organic Electronics, 9(5), 878–882(2008).C. Chindam, N. M. Wonderling, A. Lakhtakia, O. O. Awadelkarim, and W. Orfali, Applied Surface Science, 345(1), 145–155 (2015).Khawaji, I. H., Chindam, C., Orfali, W., Awadelkarim, O. O., Lakhtakia, A. ECS Transactions, 69(5), 113-119 (2015).