The patterns of integrated circuits are created on wafers by lithography. The steps of this critical manufacturing process are listed in Table 1.1. Each step is discussed at length in later chapters of this book, but a brief description of each will be given here. Most of this book is devoted to photolithography, where optical methods are used to transfer the circuit patterns from master images, called masks or reticles, to the wafers. Photolithography is the method used for patterning nearly all integrated circuits fabricated today.
Adhesion promotion: The lithography process creates the patterns of integrated circuits in films of specialized materials called resists, which are coated on the wafers on which the circuits are made. Resists typically do not adhere properly to untreated surfaces of silicon and silicon-containing materials such as silicon dioxide and silicon nitride. To ensure proper adhesion, the wafer surfaces are treated prior to resist coating.
Resist coat: Resists are typically comprised of organic polymers applied from a solution. To coat the wafers with resist, a small volume of the liquid resist is first dispensed onto a wafer.