Immersion Lithography Product Introduction Schedule

Nikon Corporation (Head office: Chiyoda-ku, Tokyo; President: Teruo SHIMAMURA) is pleased to announce that it has completed capability studies on fundamental technologies related to immersion lithography for exposure tools.

Semiconductor tool manufacturers have accelerated research and development to keep pace with increasingly faster and denser semiconductor devices. In the lithography field, advancements are being made to develop next-generation exposure tools, while plans are also being put forward to use ArF exposure tools with current leading-edge technologies in lithography processes that support even greater device miniaturization. In particular, the realization of an ArF exposure tool using immersion technology is a groundbreaking method as it enables high resolution with minimal change of the various processes, and therefore is greatly anticipated by many semiconductor manufacturers.

Nikon started the basic development for this technology early on, and as a result of a half year of feasibility studies, found no showstopper that might prevent its realization. It was consequently decided to move ArF immersion lithography to the development stage with a view toward productization. For the future, the company is aiming to launch mass production at an early timing based on the schedule given below.

By being the world's first to develop and productize immersion lithography technology, Nikon will be contributing to the development of the semiconductor industry by making further miniaturization of semiconductor devices possible, and simultaneously providing efficient facility investments for semiconductor manufacturers.

Overview of Product Introduction Schedule

Immersion Lithography Technology

Stepper resolution is normally expressed as resolution = k (process coefficient) × λ (light source wavelength) / NA (numerical aperture: brightness of the projection lens), where a shorter light source wavelength and a higher projection lens NA produces a higher resolution. NA is derived from NA = n × sinθ, where n is the refractive index of the medium through which the exposure light passes, and θ is the angle the exposure light forms. Normal exposure is processed in air, and in that case n = 1. In immersion lithography, by contrast, a liquid that has a refractive index that is greater than 1 is introduced between the projection lens and the wafer. In terms of the definition of the projection optics NA, the n increases in the equation NA = n sinθ. With the same angle of incidence, the minimum resolution can be reduced (improved) by a factor of 1/n (equivalent to an n-fold increase in lens NA). On the other hand, if it is the same NA as in a conventional system, because θ becomes small, the depth of focus can increase (improve) n-fold. In an immersion lithography exposure system using an ArF laser as the light source, deionized water with an index of refraction of 1.44 is introduced between the projection lens and the wafer. Although this method is used conventionally in microscopes, only in recent years has serious research started for applications to immersion lithography exposure tools.

Nikon started this development jointly with Tokyo Electron Limited (Head office: Minato-ku, Tokyo; President: Kiyoshi SATO) in June, 2003.

• Nikon and TEL Agree on Joint Development of Liquid Immersion Technology
• Tokyo Electron Limited