The source is an integral part of an extreme ultraviolet lithography (EUVL) tool. Such a source, as well as the EUVL tool, has to fulfil very high demands both technical and cost oriented. The EUVL tool operates at a wavelength of 13.5 nm, which requires the following new developments. The light production mechanism changes from conventional lamps and lasers to relatively high-temperature emitting plasmas. The light transport, mainly refractive for deep ultraviolet (DUV), should be reflective for EUV. The source specifications as derived from the customer requirements on wafer throughput mean that the output EUV source power has to be hundreds of watts. This in its turn means that tens to hundreds of kilowatts of dissipated power has to be managed in a relatively small volume. In order to keep lithography costs as low as possible, the lifetime of the components should be as long as possible and at least of the order of thousands of hours. This poses a challenge for the sources, namely how to design and manufacture components robust enough to withstand the intense environment of high heat dissipation, flows of several keV ions as well as the atomic and particular debris within the source vessel. As with all lithography tools, the imaging requirements demand a narrow illumination bandwidth. Absorption of materials at EUV wavelengths is extreme with extinguishing lengths of the order of tens of nanometres, so the balance between high transmission and spectral purity requires careful engineering. All together, EUV lithography sources present technological challenges in various fields of physics such as plasma, optics and material science.These challenges are being tackled by the source manufacturers and investigated extensively in the research facilities around the world.An overview of the published results on the topic as well as the analyses of the physical processes behind the proposed solutions will be presented in this paper.

https://iopscience.iop.org/article/10.1088/0022-3727/44/25/253001/pdf

Physical processes in EUV sources for microlithography

Offset in the ejection direction of target material droplets is corrected in order to stabilize EUV output in an EUV light source device. An extreme ultraviolet light source device includes a droplet generation device 110 that outputs target material droplets 101 towards a predetermined plasma emission point 103; a charging device 130 that charges the target material droplets 101; a trajectory correction device 140 that generates a force field in the trajectory to correct the travel direction of the charged target material droplets 101 a so that the charged target material droplets 101 a travel towards the plasma emission point 103; and a laser light source 150 that irradiates, at the plasma emission point 103, a laser beam onto the charged target material to generate plasma thereby.

Extreme ultraviolet light source device

A method for generating X- or EUV-radiation via laser plasma emission, in which at least one target (17) is generated in a chamber, and at least one pulsed laser beam (3) is focused on the target (17) in the chamber. The target is generated in the form of a jet (17) of a liquid, and the laser beam (3) is focused on a spatially continuous portion of the jet (17). An apparatus for generating X- or EUV-radiation via laser plasma emission according to the method comprises a means for generating at least one laser beam (3), a chamber, a means (10) for generating at least one target (17) in the chamber, and a means (13) for focusing the laser beam (3) on the target (17) in the chamber (8). The target-generating means (10) is adapted to generate a jet (17) of a liquid. The focusing means (13) is adapted to focus the laser beam (3) on a spatially continuous portion of the jet (17).

Method and apparatus for generating X-ray or EUV radiation

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, Gottingen 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.

https://iopscience.iop.org/article/10.1088/0022-3727/37/23/005/pdf

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

Spherical solid tin targets were illuminated uniformly with twelve beams from the Gekko XII laser system to create spherical plasmas, and the extreme ultraviolet (EUV) emission spectra from the plasmas were measured. The highest conversion efficiency of 3% to 13.5nm EUV light in 2% bandwidth was attained for an irradiance of around 5×1010W∕cm2. The experimental results were reproduced fairly well using a theoretical model taking the power balance in the plasma into consideration.

Characterization of extreme ultraviolet emission from laser-produced spherical tin plasma generated with multiple laser beams

As the demands of lithographic fabrication of computer chips push toward ever-decreasing feature sizes, projection extreme-ultraviolet (EUV) lithography becomes an increasingly attractive technology. The radiation source of choice for this approach is a laser plasma with a high repetition rate. We report an investigation of a new candidate laser plasma source for EUV lithography that is based on line emission from ice-water targets. This radiation source has the potential to meet all the strict requirements of EUV conversion, debris elimination, operation, and cost for a demonstration lithographic system.

New laser plasma source for extreme-ultraviolet lithography.

A high repetition-rate laser plasma target source system and lithography system is disclosed. The target source system comprises in a preferred embodiment a liquid tank source and freezer which freezes microscopic particles into crystal shapes which are projected by a nozzle jet from a high repetition rate liquid-droplet injector into the path of a flashing laser beam, which results in producing soft x-rays of approximately 13 nm. Uncollected and unshot target crystals are collected and reliquified by a heater source in order to be recycled back to the liquid tank source. Optionally an auxiliary source and detector system can be used to allow for instantaneous triggering of the laser beam. The target source system can be incorporated into well known EUV lithography systems for the production of wafer chips.

/pdf/water-laser-plasma-x-ray-point-source-and-apparatus-43k6t36p2j.pdf

Water laser plasma x-ray point source and apparatus

Mass-limited, debris-free laser-plasma EUV source

Laser‐produced plasmas are one of the most likely sources to be used for soft x‐ray projection lithography The characteristics of these sources are described in terms of the expected radiation efficiency within the illumination bandwidth of a lithographic system Measurements of the plasma particulate emission are described and techniques for interdicting this emission before it reaches the illumination optics are discussed The laser requirements are obtained for a lithographic system producing a wafer rate of 60, 6 in wafers per hour

/pdf/laser-produced-plasmas-for-soft-x-ray-projection-lithography-157d7ieiyy.pdf

Laser-produced plasmas for soft x-ray projection lithography

A high repetition-rate laser plasma target source system wherein ice crystals are irradiated by a laser and lithography system. The target source system comprises in a preferred embodiment a liquid tank source and freezer means which freezes microscopic particles into crystal shapes which are projected by a nozzle jet from a high repetition rate liquid-droplet injector into the path of a flashing laser beam, which results in producing soft x-rays of approximately 11.7 nm and 13 nm. Uncollected and unshot target crystals are collected and reliquified by a heater source in order to be recycled back to the liquid tank source. Optionally an auxiliary source and detector system can be used to allow for instantaneous triggering of the laser beam. The target source system can be incorporated into well known EUV lithography systems for the production of wafer chips.

/pdf/water-laser-plasma-x-ray-point-sources-2frxzyj15k.pdf

Feng Jin

Papers

New laser plasma source for extreme-ultraviolet lithography.

Water laser plasma x-ray point source and apparatus

Mass-limited, debris-free laser-plasma EUV source

Laser-produced plasmas for soft x-ray projection lithography

Water laser plasma x-ray point sources