Wafer process positive photoresist

Figure 9.28 The basic steps in conventional photolithography. The approach begins with deposition of a photoresist material on the surface of a wafer coated with a layer to be patterned. This process is for a positive photoresist that increases its solubility when exposed to light (arrows) [step (b)]. The photoresist development step removes the exposed resist. The problem when patterning organic materials is step (e) in which the surface is typically exposed to an oxygen plasma that would remove both the photoresist and the organic layer to be patterned.

During the component fabrication process, CFC-113 and TCA are widely nsed for cleaning surfaces and for stripping negative photoresist. Nonhalogenated solvents are often nsed for stripping positive resist. Following fabrication, the chips are tested for defects and the wafers cnt into individual chips. 

Figure 17.10 shows the process sequence of the hydrophilic overlayer (HOL) process. First, a chemically amplified or non-chemically amplified positive-tone photoresist comprising hydrophobic polymer and appropriate PAG is coated to a nominal thickness on an appropriate substrate such as a silicon wafer, followed by a soft bake to dry out the nonaqueous solvent. Next, the photoresist film is exposed to radiation of appropriate wavelength to generate photoacid from the PAG. Then the exposed film is again baked (called PEB) at the standard temperature to enhance the diffusion of the photoacid and thermolysis of the acid-labile protecting groups of the polymers. 

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