Polyimide thin films, dielectric

The dielectric properties of two different thermoset films derived from bis-benzocyclobutene monomers were described. The dielectric constant was 2.65 + 0.1. The dissipation factor was below 0.001 above 1.0 kHz. These values are significantly lower than those reported for polyimide thin films. Therefore, the BCB films described in this work are attractive candidates for interlevel dielectrics in dense multilevel interconnection structures. 

W. Jang, D. Shin, S. Choi, S. Park, H. Han, Effects of internal linkage groups of fluorinated diamine on the optical and dielectric properties of polyimide thin films. Polymer 48 (7)(2007) 2130-2143. 

As with silicon, polyimide has also been used in IC fabrication processes. Polyimide is used as a dielectric and encapsulant because it provides good planarization, electrical insulation, and resistance to solvents. Polyimide thin films are patterned using standard microfabrication processes such as photolithography and reactive ion etching both photosensitive and nonphotosensitive formulations are available. 

To obtain a measure of the dielectric constant and anisotropy of thin films, the refractive index of thin film samples was measured. It has been shown that the measured dielectric constant is approximately the square of the refractive index at 633 nm wavelength [the actual relationship is roughly e (refractive index) -i- 02.] and the anisotropy is obtained from the difference between the in-plane and out-of-plane refractive index [97]. The measured anisotropy of foamed polyimides is lower than that observed for non-foamed polyimides. In addition, a drop in refractive index of the samples was observed upon foaming. The polyimide PMDa/3FDA has a measured dielectric constant of ca. 2.9 at 70 °C. A foamed sample of PMDA/3FDA derived from copolymer 6f showed a drop in dielectric constant of 2.3 [97]. 

The last 20 years have seen enormous progress in the development of high-performance fluoropolymers. Fluorine-containing polyimides stand out as one of the few types of materials that simultaneously possess outstanding thermal stability and mechanical properties, low dielectric permittivity, and thin-film processability. This combination of properties makes them ideal for use as high-performance insulators in electronic devices. 

PFMB can be used to prepare aromatic polyimides that display solubility in ketone, ether, and polar aprotic solvents. This unusual solubility can be utilized in die facile preparation of thin films that display anisotropy in their structures and properties. The anisotropy in the optical properties of the films makes them promising candidates for use as compensation layers in liquid-crystal displays. Their low dielectric constants and CTEs in combination with their outstanding thennal and thermooxidative stabilities make diem candidates for dielectric layers in microelectronics applications. 

Here, 41 indicates the thin film transistors, 51 the substrate, 43 a dielectric layer, 49 polysilicon gates, 50 gate electrodes, 55 contact plugs, 56 bottom electrodes, 53 the planarization layer, 54 the mercury cadmium telluride layer and 57 the top electrode layer. The planarization layer is formed from silicon oxide, silicon nitride, silicon oxide nitride or from a polyimide. The planarization layer may be formed as a double or triple layer. 

Polyimides have excellent dielectric strength and a low dielectric constant, but in certain electrolyte solutions they can electrochemically transport electronic and ionic charge. Haushalter and Krause (5) first reported that Kapton polyimide films derived from 1,2,4,5-pyromellitic dianhydride (PMDA) and 4,4 -oxydianiline (ODA) undergo reversible reduction/oxidation (redox) reactions in electrolyte solutions. Mazur et al., (6) presented a detailed study of the electrochemical properties of chemically imidized aromatic PMDA- derived polyimides and model compounds in nonaqueous solutions. Thin films of thermally... 

Dielectric Characterization of Water in Polyimide and Poly(amide—imide) Thin Films... 

J.O. Simpson, A.K. StClair, Fundamental insight on developing low dielectric constant polyimides. Thin Solid Films 308-309 (1997) 480-485. 

Mathews DA (1963) Review of the lithium chloride radiosonde hygrometer. In Proceedings of the conference on humidity and moisture, vol VI, Washington, DC, pp 219-227 Matsuguchi M, Sadaoka Y, Sakai Y, Kuroiwa T, Ito A (1991) A capacitive-type humidity sensor using cross-linked poly(methylmethacrylate) thin films. J Electrochem Soc 138 1862-1865 Matsuguchi M, Sadaoka Y, Nosaka K, Ishibashi M, Sakai Y, Kuroiwa T, Ito A (1993) Effect of sorbed water on the dielectric properties of acetylene-terminated polyimide resins and their application to a humidity sensor. J Electrochem Soc 140 825-829... 

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