Resist materials basic principles

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. 

Hardness refers to the resistance of steel to indentation. The three important methods to determine the hardness are (1) the Brinell test, (2) the Vickers test, and (3) the Rockwell test. All these methods use the same basic principle wherein a ball or a pointed indenter is forced onto the material surface under a given load and the area of indentation thus created is measured. The Brinell test uses a 10-mm-diameter tungsten ball indenter under a load of 29,420 N. The Rockwell C hardness test uses a diamond cone indenter under a load of 1471 N. The Vickers test uses a diamond pyramid indenter, and the load varies. The greater the hardness of a material, the smaller the area of indentation. 

The basic principles used here are not new, of course horizontal units of this type have been used for many years in the paper-making industry, fit the latter, however, the filtered material is highly porous and constitutes a small resistance to filtration and dewatering processes. It follows that the hi -speed paper machine requires only a small pressure diflferential for the separation of fibres. 

There are numerous instruments to evaluate a material s resistance to surface wear or scratch damage. To undo stand the available options, the following desaibes the basic principle of commonly used instruments. The results fiom these testers are usually not equivalent, and caution must be taken when making any conparison of the data. 

Compounding alters the chemical and thermal resistances of the basic ma-terials-almost invariably reducing it, so that the finished sheet has less chemical resistance and often a lower thermal limit than the resin before compounding. But the principle reasons for selecting these materials in the first place are based on these same or better chemical resistances and higher thermal limits. Therefore, in a few cases, some of these materials, in the uncompounded state, are calendered or molded in a composite layer on the exposed side of the sheet or molded part, so that the compounded side may be used for bond to anchor the lining to the substrate while the side with better resistance is exposed to the corrosive environment. 

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