[15p-318-1~11] CS.4 7. Code-sharing Session: Beam Technology and Nanofabrication

▼ [15p-318-9] Imaging plate analysis of extreme ultraviolet light (EUV) from tin laser-produced plasmas

〇(P)Christopher Stephen Musgrave¹, Takehito Murakami¹, Teruyuki Ugomori², Kensuke Yoshida², Shinsuke Fujioka², Hiroaki Nishimura², Hironori Atarashi^3,1, Tomokazu Iyoda¹, Keiji Nagai¹ (1.Tokyo Inst. of Tech, 2.Osaka Univ., 3.Okayama Univ.)

Keywords:X-ray detectors, Extreme Ultraviolet (EUV), Laser-produced plasmas

For the production of the next generation of integrated circuits, Extreme Ultraviolet Lithography (EUVL) of 13.5 nm light is becoming more exciting. EUV is produced on the ablation of tin metal by an intense laser pulse (typically 10¹⁰ W/cm²). High volume manufacturing (HVM) capabilities are now approaching, however for HVM to be cost-efficient the power at the intermediate focus must be greater than 240 W. Improvements to current EUVL sources have been extensive, all resulting with greatly increased powers at the intermediate focus (now up to 100 W). Therefore, there is still a directive for light source improvement. Our research has focused on obtaining better information about the EUV light across a large angular distribution. This is in contrast to other techniques (faraday cups, grazing incidence spectrometers), which can only obtain information at singular points. A better understanding the EUV light across a large angular distribution could influence light source design in areas such as target type or laser pulse lengths etc. To achieve this, we used flexible films composed of BaFBr:Eu called phosphor imaging plates (IPs). IPs photoluminesce when exposed to EUV light and other high energy species, and observe all angles of interest simultaneously. The IPs can then be read and is translated into intensity vs angle information. In this work, we ablated a planar tin target with a 1064 nm Nd:YAG lasers (intensity 10¹⁰ and 10¹¹ W/cm²), with IPs at angles from 20-90 degrees relative to the point of ablation. We obtained IP data with high-space resolution (0.2 degrees) along with grazing incidence spectrometer (5-20 nm grate) data. In addition, the IPs were set at two different distances from the tin target (103 mm and 200 mm). The laser conversion efficiency at 2% bandwidth of 13.5 nm (1.1%) was calculated with increased accuracy by using the cosine-fitting values of the IP data. Finally, we provide a practical assessment of using imaging plates, including disclosure of a damage issue.