Lithography

Lithography is big business--multi billions of dollars in 1990-and the most single important step in the manufacture of semiconductor devices and chips. Manufacturing of a typical DRAM chip involves at least 20 separate lithography exposure sequences. DRAM products are the prime drivers of progress in the semiconductor industry requiring evolutionary change by a factor of 2 each six years--i.e., lithography dimensions shrink 0.7X each 3 years with the introduction of a new DRAM chip having 4X as many bits as the previous product and thus over 2 memory chip generations spanning at most six years, dimensions of minimum feature sizes decrease 2X! For the lithographic system--exposure tool, imaging resist, and pattern transfer process--to keep pace with this formidable driver, the DRAM chip, is a challenge. Lithography is not by any means static. This paper discusses the challenges in--tooling: thruput, resolution, overlay and chip size;--materials: for tooling such as glasses for deep UV lenses, resist systems;--the integration of tools, materials, and processes into the lithographic system. Examples of how optical, e-beam, and x-ray lithography can meet the challenges of the late 1990's and into 201X will be cited.