The research group led by Dr. Toshihisa Tomie of The Advanced Semiconductor Research Center (ASRC) of the National Institute of Advanced Industrial Science and Technology (AIST) has developed an innovative extreme ultraviolet (EUV) radiation source technology for EUV lithography, which is expected to be applied to the future production of semiconductors. The conversion efficiency from excitation energy to EUV radiation will be as high as 3%.
The R&D work was carried out as a part of the “New Generation Semiconductor Device Process Basic Technology Program: R&D Project of Basic Technology for EUV Exposure System”, entrusted from the New Energy and Industrial Industry Development Organization (NEDO), and jointly implemented by AIST and the Technology Research Association: EUV Exposure System Technology Development Organization (EUVA).
The elementary line width of semiconductor device is now 90nm (1nm = 1/1,000,000,000m), and is expected to be reduced to 45nm around 2010 which will be mass produced by EUV lithography. A plasma EUV source is regarded as the most promising source of EUV radiation, and a heated competition is underway over the world. The top priority issue for implementing EUV lithography is to upgrade the EUV power extensively. The present result is to give a fine prospect for solving this problem and to provide a great stride toward the realization of EUV lithography.
In the existing plasma EUV source, xenon gas is used for the target, but recently tin-target has been attracting attention because of its potential of high conversion efficiency. With a solid target, however, it is difficult to get high frequency repetitive supply of target material indispensable for securing high output level, and involves a problem of ejecting enormous amount of particles as large as tens of nanometers to damage the optical system. The new plasma EUV source technology developed by the ASRC-AIST has successfully solved these problems by using fine particle cluster of tin as target materials. Furthermore, conditions for ensuring high conversion efficiency were theoretically identified and a demonstrating experiment proved conversion efficiency four times as high as that of tin plate target.