The ArF laser for the next generation multiple-patterning immersion lithography supporting green operations and leading edge processes

Multiple patterning ArF immersion lithography has been expected as the promising technology to meet tighter leading edge device requirements. The most needed features for the next generation lasers are improvement of device yield, the prevention against rare resource shortage and the reduction of operational costs in multiple-patterning lithography [1] [2]. To support these requirements, GT65A provides the functions of tighter E95 bandwidth stability, lower E95 bandwidth and tunable E95 bandwidth to enhance chip yields [3] [4]. Furthermore, in the prevention against rare resource shortage and the reduction of operational costs, GT65A realizes helium-free operation in a line narrowing module (LNM) and the reduction of neon consumption in a chamber [5]. A faster actuator equipped with the movable lens enables shot average of E95 bandwidth stability to be within ±5 fm to more rapidly adjust laser beam wavefront. More stable spectral bandwidth stability leads to improve CD uniformity. New designed LNM realizes 200 fm of lower E95 bandwidth, because it suppresses thermal wavefront deformation in optical elements and mechanical components. Lower E95 bandwidth improves image contrast and enhances exposure latitude. The combination of a faster actuator and new LNM enables tunable E95 bandwidth to vary from 200 to 450 fm at less than time intervals of a wafer lot exchange, six seconds. This enhances imaging margins by optimizing E95 bandwidth of light sources according to individual scanners. New LNM additionally enables helium-free operation to lower E95 bandwidth in spite of nitrogen purge with higher refractive index variation to temperature. The employment of a new LNM can avoid helium supply risk and saves helium consumption of 80 kL/year/unit. Gas recycling system saves by about 92% of neon consumption in ArF laser. Similarly, the recycling system saves about 85% of neon consumption in KrF laser too. These functions with GT65A improve chip yield and process margins, and support sustainable high volume manufacturing (HVM).