Effect of molecular orientation on the dielectric properties of spin‐coated polyimide films

Abstract

SYNOPSISThe effect of molecular orientation on the dielectric properties of spin-coated polyimide films has been studied in situ for pyromellitic dianhydride with 4,4'-oxydianiline ( PMDA/ ODA) and biphenyldianhydride with p-phenylenediamine (BPDA/PPD) . The degree of molecular orientation is characterized by the optical anisotropy between the in-plane and the through-plane refractive indices. The through-plane dielectric properties are measured by fabricating parallel-plate capacitors directly onto the silicon substrate. Both the birefringence and the dielectric constant of PMDA/ODA polyimide vary with film thickness; however, these properties are independent of film thickness for BPDA/PPD films. T o confirm that the measured dielectric constant obtained from the parallel-plate structures is free from a significant edge effect, finite element modeling of the electrostatic potential within the dielectric is performed. Models for both isotropic and anisotropic dielectric properties indicate that the fringing effects are indeed negligible for the film thicknesses examined. Thus, the changes observed in the measured dielectric constant are attributed to the variations in the molecular orientation. The optical anisotropy observed for the polyimides suggests a corresponding dielectric anisotropy in the films. An estimation using the Maxwell relation indicates that the dielectric anisotropy at lo5 Hz is 0.31 for PMDA/ ODA and 0.85 for BPDA/PPD.

Thermal diffusivity of aromatic polyimide thin films by temperature wave analysis

“…A large variety of chemical structures of aromatic polyimide have been developed for industrial applications with a detailed study of physical properties [17][18][19] that have shown the anisotropy in refractive indices, 3,4,35,42,[44][45][46][47][48][49][50][51] dielectric constant, mechanical prop-erties, and thermal expansion coefficients, 3,4,6-12,42-51 depending on the details of the process by which they were made. However, there is not enough necessary basic data of thermal transport of aromatic polyimide because the typical methods require an advanced technique when applied to thin and transparent polymeric films with low thermal conductivity and diffusivity.…”

Interfacial sliding in Cu/Ta/polyimide high density interconnects as a result of thermal cycling

“…3, 4 The orthotropic nature of the elastic and thermal expansion properties is attributed to the alignment of the polyimide chains in the plane of the film. 5,6 This paper reports on the use of an atomic force microscope (AFM) to study deformation in a single level Cufra/polyimide HDIC as a result of the imidization thermal cycle. The surface topography of HDICs fabricated with two different polyimides was Ta h = l )tm measured at room temperature before and after heating to 350~ in nitrogen.…”

Low Dielectric Materials for Microelectronics

“…These structural characteristics give rise to excellent mechanical and thermal properties in the form high modulus (8-10 GPa) and high Tg (350 to 400 o C) [10]. However, the rigid chain structure causes the PI chains to align preferentially parallel to the substrate, especially when deposited as thin films, which results in anisotropic properties [11][12][13][14][15][16][17][18]. For example, while the out-of-plane k value of BPDA-PDA is 3.1, the more important in-plane value is >3.5 [14].…”