Polymer resist film

The irradiation of polymers is widespread in many industries. For example, microlithography is an essential process in the fabrication of integrated circuits that involves the modification of the solubility or volatility of thin polymer resist films by radiation. The sterilization by radiation of medical and pharmaceutical items, many of which are manufactured from polymeric materials, is increasing. This trend arises from both the convenience of the process and the concern about the toxicity of chemical sterilants. Information about the radiolysis products of natural and synthetic polymers used in the medical industry is required for the evaluation of the safety of the process. 

Thick organic polymer resist films are used for the conventional lithography. Their thicknesses are dozens to hundreds of nanometers. When a processing size becomes small and enters nanometer order in electron beam lithography, scattering of electrons in a resist causes various problems, such as the proximity effect. The variation in molecular mass of each molecule which forms the resist also reduces the resolution. If the ultrathin resist film of several nanometers thickness will be realized, the lithography of higher resolution will become possible. 

Individual microelectronic devices consist of numerous layers of carefully patterned thin films. Patterning depends upon the ability to define and draw a two-dimensional pattern on a wafer substrate. Currently, this ability depends on photolithography by optical projection, in which a polymer resist film is deposited on the wafer and subsequently exposed to ultraviolet... 

A new simple and reliable method for monitoring photoinduced acid generation in polymer films and in solutions of the kind used in 193 nm and deep-UV lithography was developed. By using N-(9-acridinyl)acetamide, a fluorescent acid-sensitive sensor, we have been able to study the effects of trifluoroacetic acid and photoacids generated from triphenylsulfonium hexafluoroantimonate on the spectral properties of the acid sensor in THF solution and in alicyclic polymer resist films exposed at 193 nm. In both cases a hypsochromic spectral shift and an increase in fluorescence intensity were observed upon protonation. This technique could find application in the study of diffiisional processes in thin polymer films. 

The plasma etch rates of nanocomposites, consisting of PMMA resists, impregnated with Ceo fullerenes, were compared with those of commercially available resists. " Fullerenes were found to be successful at improving the etch resistance under CF4 and CI2 reactive ion etch conditions. The basic idea of this concept is the reduction of free volume in the polymer resist film. This then results in improved mechanical and etch resistance. 

Fig. 1. The hthographic process. A substrate is coated with a photosensitive polymer film called a resist. A mask with transparent and opaque areas directs radiation to preselected regions of the resist film. Depending on resist characteristics, exposed or unexposed portions of the film are removed using a developer solvent. The resulting pattern is then transferred to the substrate surface and the resist is stripped.

Fuhy aromatic, thermally (up to 250°C) and hydrolyticahy resistant films of PODs have been reali2ed from polyhydra2ides (56). Films of these polymers are useful as seawater desalination membranes. 

Polymers are only marginally important in main memories of semiconductor technology, except for polymeric resist films used for chip production. For optical mass memories, however, they are important or even indispensable, being used as substrate material (in WORM, EOD) or for both substrate material and the memory layer (in CD-ROM). Peripheral uses of polymers in the manufacturing process of optical storage media are, eg, as binder for dye-in-polymer layers or as surfacing layers, protective overcoatings, uv-resist films, photopolymerization lacquers for repHcation, etc. 

The chemical name for such materials is poly(bisbenzimid-azobenzophenan-throlines) but they are better known as BBB materials. Such polymers have a Tg in excess of 450°C and show only a low weight loss after aging in air for several hundred hours at 370°C. Measurements using thermal gravimetric analysis indicate a good stability to over 600°C. The main interest in these materials is in the field of heat-resistant films and fibres. 

TiCU readily functionalizes hydrophilic polymers such as poly(vinyl alcohol), m-ciesol novolac and methacrylic acid copolymers as well as moderately hydrophobic polymers such as poly(methyl methacrylate), poly(vinyl acetate), poly(benzyl methacrylate) and fully acetylated m-cresol novolac. HCI4 did not react with poly(styrene) to form etch resistant films indicating that very hydrophobic films follow a different reaction pathway. RBS analysis revealed that Ti is present only on the surface of hydrophilic and moderately hydrophobic polymer films, whereas it was found diffused through the entire thickness of the poly(styrene) films. The reaction pathways of hydrophilic and hydrophobic polymers with HCI4 are different because TiCl is hydrolysed by the surface water at the hydrophilic polymer surfaces to form an etch resistant T1O2 layer. Lack of such surface water in hydrophobic polymers explains the absence of a surface TiC>2 layer and the poor etching selectivities. 

Resist systems may be more complicated than just a single polymer in a single solvent. They may be composed of polymer, polymer/dye, or polymer/polymer combinations (where the small molecule dye or additional polymer increases the radiation sensitivity of the resist film) with one or more solvents. The more complicated polymer/dye or polymer/polymer systems have the added possibilities of phase separation or aggregation during the non-equilibrium casting process. Law (16 I investigated the effects of spin casting on a... 

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