Polyimides thin film properties

VDP of polyimides is usually performed in vacuum (pressures <10 Pa). Just as in any CVD process, the deposition parameters greatly influence the properties of the polyimide thin films. The effect of a few notable ones viz., substrate temperature and the relative fluxes of the precursor vapors is the focus of the next section. 

The post deposition processing parameters (curing temperature, time) have a profound impact on the thermal properties of polyimide thin films. It has been observed that, films cured at around 300°C for 1 hour exhibit markedly superior thermal stability as compared to those that were not cured." ° Cured PMDA-ODA... 

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. 

Hamciuc C., Carja I.-D., Hamciuc E., Vlad-Bubulac T., and Ignat M. Phthalonitrile-containing aromatic polyimide thin films with nano-actuation properties. Polym. Adv. Technol. 24 no. 2 (2013) 258-265. 

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. 

Davis GC, Heath BA, Gildenblatt G (1984) Polyimide-siloxane properties and characterization for thin film. Electronic Applications in Ref 1 847-869... 

Polvimide-Metal Interfaces. Several technological applications including semiconductor packaging and metallization demand a reliable and durable adhesion properties of the metal films. In the development of multilayer devices consist of alternating layers of metal and polyimides several reliable techniques are needed to study both thin films and their interfaces. The usefulness of the nuclear scattering techniques to study the metallization and the associated interfacial elemental diffusion processes under the effects of various temperature and humidity treatments on the metal-polyimide systems, such as Al, Cu, N, and Au on Du Pont Kapton type H have already been reported (21., 22.). Only a couple of examples are presented here to illustrate the ERD application. 

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... 

Metal thin films deposited on polymers are widely used in various industrial domains such as microelectronics (capacitors), magnetic recording, packaging, etc. Despite much attention that has been paid in the recent literature on the adhesive properties of metals films on polyimide (PI)( 1 - 5 ) and polyethyleneterephtalate (PET)((L) it appears that a better knowledge of the metal/polymer interface is needed. In this paper we focus ourself on the relationship between the adhesion and the structural properties of the aluminum films evaporated (or sputtered) on commercial bi-axially stretched PET (Du Pont de Nemours (Luxembourg) S.A.). A variety of treatment (corona, fluorine,etc.) have been applied in order to improve the adhesion of the metallic layer to the polymer. The crystallographic... 

Stresses in solvent based coatings arise from the differential shrinkage between the thin film coatings and the corresponding substrates. These stresses are due to volume changes associated with solvent evaporation, chemical reaction (i.e. cyclization in polyimide formation) and differences in thermal expansion coefficients of the coating and substrate (4>5). The level of residual stress depends on the material properties such as modulus, residual solvent content and crosslinking (5) and its thermal-mechanical history. 

In general, polyimides exhibit a high refractive index typically between 1.6 and 1.7 and hence can be of definite practical interest particularly as antireflection coatings. Also, similar to parylene thin films, polyimides exhibit anisotropic optical properties. The reported values of refractive index of polyimides were n = 1.653 and n = 1.624 before curing and... 

Aromatic polyimide films of varying thickness were prepared to study the effect of the thickness on the refractive indices. Figure 6 shows that the refi active indices are fairly independent of the film thickness in the range of 1 pm to 15 pm for 6FDA-PFMB. For thicknesses above 15 pm, the difference between the in-plane and out-of-plane refractive indices ( and ) gradually decreases with increasing the film thickness. This indicates that the thin film linear optical properties gradually approach the bulk properties which should be three-dimensionally isotropic. 

Given the birth of MEMS from the IC industry, the dominant material used in the early devices was silicon. The use of silicon as a substrate and structural material, and the use of polysilicon as a thin film structural material, has continued to the present day for several reasons. The microfabrication techniques for silicon are highly developed and flexible, the microfabrication equipment has been designed for silicon, the properties of silicon are very well known and can be tightly controlled, silicon has excellent mechanical properties, and silicon has an insulating native oxide that can be used as a sacrificial layer. Other thin film materials that are commonly used in MEMS include silicon nitride, metals, and conventional polymers, such as polyimide. 

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