Photomasks are defect-free optical templates - the printing masters for the fabrication of integrated circuits (ICs). When IC feature sizes fall below the exposure tool's source wavelength, photomask fabrication becomes difficult: very strict mask critical dimension (CD) and feature placement specifications, intensive capital equipment investment, unique raw materials and applications, and special expertise requirements for photomask fabrication technologists are necessary to fabricate modern microelectronics. Thus the rapid recent growth of the field and the need for this book. This text details the science and technology of industrial photomask production, including fundamental principles, industrial production flows, technological evolution and development, and state-of-the-art technologies. Focusing on industrial applications rather than pure science, the goal of the book is to provide a comprehensive reference for any engineer developing microelectronic manufacturing processes.