Extreme ultraviolet light sources for use in semiconductor lithography—state of the art and future development

Abstract

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 syste...

Characterization and optimization of the laser-produced plasma EUV source at 13.5 nm based on a double-stream Xe/He gas puff target

“…The miniaturization in electronics strongly depends on the EUV technology progress acquiring powerful EUV light sources [2]. Recently, a growing number of compact EUV plasma sources have been developed including laser-produced plasmas (LPP) [3,4]. The EUV source for exposure tools for high-volume manufacturing basically has to meet industrial requirements of power in-band (at 13.5 nm within 2% BW) and may not have an impact on the lifetime of the reflective optics.…”

“…The EUV source for exposure tools for high-volume manufacturing basically has to meet industrial requirements of power in-band (at 13.5 nm within 2% BW) and may not have an impact on the lifetime of the reflective optics. This power limitation leads to the demand on the EUV power into the half sphere of 400 W/2π in the laser-produced plasmas (LPP) case and of 1 kW/2π for gas discharge-produced plasmas (GDPP) [4]. To our knowledge, the highest EUV power (measured on intermediate focus (IF) point) of 104 W (115 W required) reached until now using the CO 2 laser with the pre-pulse was recently reported [5].…”

Mitigation of fast ions from laser-produced Sn plasma for an extreme ultraviolet lithography source

“…1 However, several challenges must be addressed before applying it to high volume manufacture ͑HVM͒; one of them is to develop an efficient, clean, and powerful EUV light source. 2 Laserproduced plasma has been one of the most promising EUV light source candidates. Because of the availability of optics, most of the efforts focus on in-band ͑2% bandwidth͒ 13.5 nm EUV light.…”

Next-generation lithography for 22 and 16 nm technology nodes and beyond

“…Adequate in-band EUV power supplied by these sources is the key to high volume-production throughput and low cost of ownership [18][19][20][21][22][23][24][25]. Because of the EUV absorption in gases, the source chamber, optical chamber, and wafer printing chamber are kept at the same vacuum level without filters, which necessitates strict debris and contamination control.…”