Resist materials polyimides

Trilevel Schemes. Trilevel processing (6, 7) requires planarization of device topography with a thick layer of an organic polymer, such as polyimide or a positive photoresist that has been baked at elevated temperatures ( hard baked ) or otherwise treated to render it insoluble in most organic solvents. An intermediate RIE barrier, such as a silicon dioxide, is deposited, and finally, this structure is coated with the desired resist material. A pattern is delineated in the top resist layer and subsequently transferred to the substrate by dry-etching techniques (Figure 3). 

The polyimide class of polymers are known to possess a high degree of thermal stability. They decompose in an inert atmosphere around 500°C and in air about 400°C as indicated by thermo-gravimetric analysis (1). Because of the great thermal stability of 2,4,6-triphenyltriazine (2J (decomposes above 486°C), copolymerization of this compound with imides should lead to enhanced heat resistant materials in the form of triaryl-s-triazine ring (TSTR) cross-linked (XL) polyimides. 

It was found that the incorporation of POSS slightly reduces the glass transition temperature (Tg) of Kapton polyimide, however, the Tg values of POSS-PIs are well above the temperatures experienced by materials in LEO. The CTE of POSS-PIs is similar to the CTE of commercial Kapton H . A new SC-POSS monomer imparts about the same AO resistance to polyimides as the MC-POSS monomer. The modulus, Tg, and CTE of SC-POSS-PIs were determined before and after exposure to atomic oxygen, and are comparable to the values of these properties for Kapton H . 

Polyether-b-polyimide-b-siloxane copolymer with low MW PEI impact-resistant materials with excellent processability and HDT Durfee Rock, 1993... 

Resist materials based on photoimageahle polyimides have also been reported eontaining polyamie aeids to which photopolymerizable units have... 

As implied from the Materials section, the more corrosion-resistant materials will require more aggressive etchants than easy-to-corrode materials. Thus, ceramics and glasses are usually etched in etchants containing the toxic and hazardous etchant hydrofluoric acid (HF), certain polymers such as polyimide are etched in... 

Plasticization behaviour induced by condensable gases and vapours (e.g. carbon dioxide, hydrocarbons and other organic vapours) in polymer membranes is stiQ a painful problem in polymeric membrane-based gas separation applications [27,28]. Recently, novel hyperbranched polyimides were prepared from telechelic polyimides and an attempt was made to improve its gas separation performance and physical stability by obtaining plasticization-resistant materials [29-33] (see e.g. Chapters 4, 6 and 7 of this book). 

Syntheses.—The principal use to which polyimides are put is in the production of high-temperature-resistant materials. This is still a comparatively new field and the balance of papers on this topic has been towards the synthesis and properties of the polyimides, while notably little work has appeared on the mechanism of the polymerization process or on the morphology of the polymer. Nevertheless an attempt has been made to describe polyimide formation in terms of an equilibrium process. ... 

An important issue in the construction of humidity sensors is the selection of materials. Among the polymeric humidity-sensitive materials, polyimides represent a good choice because they exhibit excellent thermal stability, low dielectric constant, and low equilibrium moisture content. Conversely, polyimides are highly resistant to irradiation and are mechanically strong and chemically stable in the presence of most common contaminants. 

It is well known that sol-gel method is suitable for preparing organic-inorganic hybrid materials. This technique can be apphed to fabrication of heat-resistant polyimide-Si02 hybrids (Kakimoto, 1991). Si02 components improve the heat-resistance of polyimide polymers. 

The often hot nature of exhaust gases leads to the frequent use of PTFE/Teflon as the material for bag media, as well as the newer Tefaire (a needlefelted blend of 25% glass and 75% Teflon fibres). Other temperature resistant materials include a range of polyimide fibres, especially for minerals processing and cement production exhausts. 

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