Extreme ultraviolet light sources for use in semiconductor lithography—state of the art and future development
Extreme ultraviolet light sources for use in semiconductor lithography—state of the art and future development
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DOI：
10.1088/0022-3727/37/23/005
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发表时间：
2004-12
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影响因子：
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通讯作者：
U. Stamm
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作者：
U. Stamm
本文概述了由Lambda Physik AG、Göttingen和JENOPTIK LOS GmbH，德国耶拿的合资企业Xtreme Technologies的极端紫外线(EUV)光源的开发现状和计划。给出了气体放电产生的等离子体(GDPP)和激光产生的等离子体(LPP)这两种EUV光源的主要技术的结果。GDPP EUV光源采用Z-Pinch原理，具有高效的滑动放电预电离。第一批商业气体放电源的原型已经集成到极紫外光微步进器中，极紫外光功率为35W，功率为2π锶。这些源配备了碎片过滤器，该过滤器支持在1 kHz重复频率下超过1亿个脉冲的光学寿命。放电系统本身的部件实现了相同的寿命。基于氙气的高功率放电源的发展，通过采用多孔金属冷却技术，将200W的极紫外光功率转换为2π的锶固体角，连续工作，重复频率为4.5kHz。考虑到1.8Sr源集热组件的实验验证损耗，可用的中间聚焦(IF)功率为22W。可用的中频功率取决于EUV扫描仪光学系统的拉伸度。对于EUV发射等离子体的当前尺寸，拉伸接受系数可能低于0.5。因此，目前使用的1.8Sr集电镜的中频功率可能在10W左右，因此，以锡为发射体的Z-Pinch放电源已被开发为一种更有效的替代氙气燃料的源。锡源的转换效率(CE)是氙气的两倍。在仅4.5π的重复频率下，获得了400W的2 kHzsr极紫外光功率。可用的中频功率为44 W。评估TiN源性能的评估揭示了利用现有技术实现大批量制造(HVM)功率规范的潜力。由于LPP EUV光源等离子体尺寸小，热管理简单，因此被研究作为GDPP光源的替代品，以获得足够的功率用于EUV光刻HVM。这些光源使用氙气喷射靶系统和高功率脉冲激光作为Xtreme技术公司开发的等离子体激励驱动器。在2π的立体角范围内，激光功率转化为极紫外光功率的最大CE为1.0%。实验中，当激光功率为0.7kW时，以2π的锶固体角在13.5 nm处产生了7W的极紫外光辐射。直径0.5 mm的小源体积将允许5sr的大收集角。相应的可用中频功率估计为2.3W，安装的1.2kW激光驱动器的全功率为10W极紫外光功率为2πsr。使用现有的驱动器激光技术，具有TiN靶标的LPP源估计可获得近10W的中频功率。GDPP和LPP源仍在争夺用于EUV光刻的HVM源技术。这些技术中的每一项都有自己的挑战。EUV扫描仪光学系统拉长的优化潜力肯定会影响HVM源技术的任何决定。
This paper gives an overview of the development status and plans of extreme ultraviolet (EUV) light sources at XTREME technologies, a joint venture of Lambda Physik AG, Göttingen and JENOPTIK LOS GmbH, Jena, Germany. Results for gas discharge-produced plasma (GDPP) and laser-produced plasma (LPP), the two major technologies in EUV sources, are presented. The GDPP EUV sources use the Z-pinch principle with efficient sliding-discharge pre-ionization. First prototypes of commercial gas discharge sources with an EUV power of 35 W in 2π sr have already been integrated into EUV microsteppers. These sources are equipped with a debris-filter which supports an optics lifetime exceeding 100 million pulses at 1 kHz repetition rate. The same lifetime was achieved for the components of the discharge system itself. The progress in the development of high-power discharge sources based on xenon resulted in an EUV power of 200 W into a 2π sr solid angle, in continuous operation, at 4.5 kHz repetition rate, by implementation of porous-metal cooling technology. The available intermediate focus (IF) power is 22 W taking into account experimentally verified losses in a 1.8 sr source collector module. The usable IF power depends on the etendue of the optical system of the EUV scanner. For the current size of the EUV emitting plasma the etendue acceptance factor may be below 0.5. The currently usable IF power with 1.8 sr collector mirror may therefore be about 10 W. Z-pinch discharge sources with Sn as the emitter have been developed as a more efficient alternative to xenon fuelled sources. Tin sources showed a conversion efficiency (CE) that was double that of xenon. EUV power of 400 W in 2π sr has been generated at only 4.5 kHz repetition rate. The available IF power is 44 W. Estimates evaluating the tin source performance reveal the potential for achieving high-volume manufacturing (HVM) power specification by using existing technology. Because of their small plasma size and the rather simple thermal management in the EUV generator the LPP EUV sources are investigated as alternatives to GDPP sources to achieve sufficient power for HVM with EUV lithography. These sources use xenon-jet target systems and high-power pulsed lasers as plasma excitation drivers developed at XTREME technologies. The maximum CE from laser power into EUV in-band power is 1.0% into a solid angle of 2π. Experimentally, 7 W EUV radiation is generated at 13.5 nm in a 2π sr solid angle with 0.7 kW laser power on the target. The small source volume of <0.5 mm diameter will allow large collection angles of 5 sr. The corresponding usable IF power is estimated to be 2.3 W. With the full power of the installed 1.2 kW laser driver 10 W EUV power in 2π sr is expected. LPP sources with tin targets are estimated to achieve nearly 10 W IF power with existing driver laser technology. GDPP and LPP sources still compete for the technology of HVM sources for EUV lithography. Each of these technologies has its challenges. The optimization potential of the etendue of the optical system of EUV scanners will certainly influence any decision for a HVM source technology.