An extreme ultraviolet (EUV) light source produces high-temperature, high-density plasma to take out the EUV beam in the wavelength region of 10 to 15 nm. Two methods are used for producing plasma: the Laser-Produced Plasma (LPP) method and the Discharge-Produced Plasma (DPP) method. The EUV beam exiting from the plasma is collected by the collection optics, passes through a point called the intermediate focus, and illuminates a reflection-type mask after it has been reshaped by the illumination optics. The EUV beam reflected by the mask is exposed by the projection optics to form a pattern on photoresist that is coated on a wafer surface. (See figure 1.)
Today, EUV lithography technology is still in the laboratory stage; a number of engineering issues must be solved before it can be used for the production of semiconductor devices. In particular, the power of the light source has reached only about 40 to 50 W, attainable for a short period of time. A light source with power at a level of 100 W, and capable of operating for several months without maintenance, is expected to be put into practical use within the next 3 years.

Figure 1. Conceptual Diagram of an EUV Lithography Tool
(Source: Courtesy of EUVA ₂₎

< References >

1. “Present Status and Future of EUV (Extreme Ultra Violet) Light Source Research,” J. Plasma Fusion Res., Vol. 79, No. 3 (March 2003) [219-2621].
2. EUV Website: http://www.euva.or.jp/index.html