Design of resist materials

An example of the wavelength matching technique is apparent in the work of Taylor et. al. (58,59). Taylor and coworkers at Bell Laboratories have demonstrated very high sensitivity in 2,3-dichloropropyl acrylate-based resist systems for exposure to the palladium emission line. The sensitivity of these materials is in part the result of the high absorption cross section of chlorine for the palladium radiation. With the exception of apparent sensitivity perterbations that can be explained on the basis of unique absorption characteristics, there seem not to be new principles involved in the design of resist materials for ion beam or x-ray exposure. 

Approaches to the design of resist materials which incorporate chemical amplification have been directed toward three different areas ... 

As regards valves, diaphragm types are the most satisfactory but most valves have to withstand extremely turbulent conditions, and as with pumps, even the best designs need to be constructed of resistant materials, or be coated with a suitably durable material such as silastomer or neoprene. 

The photoresponsive properties of molecular glasses also have been applied in the design of resists for semiconductor lithography. In a resist, irradiation changes the solubility of the materials, making it more or less soluble (positive or negative resist, respectively). The search for new resist materials follows the development of lithographic techniques toward deep-UV and electron beam... 

The basic concepts employed in early photolithography, both in materials and processing, have been extrapolated to modern lithographic technologies including x-ray and electron beam. In the remainder of this book we will discuss in detail the fundamental principles of chemistry and physics as they apply to the design and use of resist materials. 

Three extensive introductory chapters by Everhart, Broers, and Bowden provide a solid foundation in the physics and chemistry of the lithographic process together with an overview of current resist systems. These 3 chapters, coupled with 20 chapters from outstanding radiation polymer chemists throughout the world, provide a firm basis for understanding the important fundamental concepts in radiation chemistry as applied to design, development, and application of resist materials. 

A detailed transport model for resist dissolution has been developed (169). In conjunction with standard ellipsometric equations describing multilayer films, the model provides quantitative agreement with the observed traces from the in situ ellipsometer. Model parameters are thus extracted, and their significance in terms of molecular structures of the system can be established. This model can then be extended for predictive purposes in the design and selection of resist materials. 

Over the past few years we have been interested in the design of new types of resist materials which generally possess high sensitivities due to structural features which allow for the occurrence of radiation initiated repetitive processes. The three main approaches we have investigated to-date all maximize the use of available protons through "chemical amplification" they are the following ... 

The properties of filled materials are eritieally dependent on the interphase between the filler and the matrix polymer. The type of interphase depends on the character of the interaction which may be either a physical force or a chemical reaction. Both types of interaction contribute to the reinforcement of polymeric materials. Formation of chemical bonds in filled materials generates much of their physical properties. An interfacial bond improves interlaminar adhesion, delamination resistance, fatigue resistance, and corrosion resistance. These properties must be considered in the design of filled materials, composites, and in tailoring the properties of the final product. Other consequences of filler reactivity can be explained based on the properties of monodisperse inorganic materials having small particle sizes. The controlled shape, size and functional group distribution of these materials develop a controlled, ordered structure in the material. The filler surface acts as a template for interface formation which allows the reactivity of the filler surface to come into play. Here are examples ... 

Several nanoscale multilayered materials have been prepared. Techniques of Rutherford backscatteiing, electron microscopy and microanalysis and other metallurgical tools have been used to investigate wear resistant, scratch resistant, microhardness, and spark erosion properties of these nanoscale multilayered materials. Preliminary results indicate that nanoscale multilayered materials with improved thermomechanical, properties can be synthesized for application in the EM gun system. Application of ion beam technology for the synthesis of gradient materials appears to have great potential for design of new materials with improved properties to be used in fabrication of many armament materials. 

Resists function by radiation-induced alteration of the solubility of the materials. There are two basic classes of resist materials, namely, negative and positive resists (see Fig. 4.5). Negative resists become less soluble on exposure to radiation i.e., the unexposed areas can be selectively removed by treatment with an appropriate developer solvent. Positive resists selectively undergo an increase in solubility on exposure, enabling the exposed regions to be selectively removed in the developer. Both types of resists are formulated from polymers designed to have physical and chemical properties consistent with semiconductor... 

Designing temperature-limited heat transfer equipment Lowering corrosion potential by use of resistant materials of construction... 

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