10 - Lithography

Abstract

The extraordinary progress and success of optical lithography using ultraviolet (UV) light in the development and production of microelectronic devices and integrated circuits (IC) are truly phenomenal. Lithography, the printing of patterns on surfaces, is both a driving force and a bottleneck in semiconductor manufacturing. Optical lithography provided IC manufacturing with the unique combination of high-volume production, high precision, and low-cost fabrication. Semiconductor IC fabrication is based on the wafer (usually, silicon wafer) fabrication process, involving hundreds of processing steps and including several photolithographic cycles. A simplified processing sequence consists of the deposition of some form of a thin film on a wafer (oxide, polysilicon, and metal); mask image transfer in the resist using photolithography; etching the developed pattern into the deposited film; some other form of wafer processing such as ion implantation, dopant diffusion, or substrate etching; and removal of the previous resist layer and preparation for the next sequence.