Discharge- and laser-produced plasma (DLPP) devices are being used as light sources for Extreme Ultraviolet (EUV) generation. A key challenge for both, DPP and LPP, is achieving sufficient brightness to support the throughput requirements of nanometrology tools. To simulate the environment of a hybrid DLPP device and optimize EUV output, we have developed an integrated HEIGHTS-DLPP computer simulation package. The package integrates simulation of two evolving plasmas (DPP & LPP) and includes modeling of a set of integrated self-consistent processes: external power source and plasma energy balance, plasma resistive magnetohydrodynamics (MHD), plasma heat conduction, detailed radiation transport (RT), and laser absorption and refraction. We simulated and optimized DLPP devices using Xe gas as a target material. We synchronized the external circuit parameters, chamber gas parameters and laser beam temporal and spatial profiles to achieve maximum EUV output. The full 3D Monte Carlo scheme was integrated for detailed RT and EUV output calculations in Xe using more than 3600 spectral groups. The modeling results are in good agreement with Julich Forschungszentrum experimental data. Theoretical models, developed and integrated in HEIGHTS package, showed wide capabilities and flexibility. The models and package can be used for optimization of the experimental parameters and settings, investigation of DLPP devices with complex design, analyzing the impact of integrated spatial effects and working timeline arrangement on the final EUV output, and EUV source size, shape and angular distribution.
EUV source power is critical for advanced lithography, for achieving economical throughput performance and also for minimizing stochastic patterning effects. Power conversion efficiency can be increased by recycling plasma-scattered laser radiation and other out-of-band radiation back to the plasma via retroreflective optics. Radiation both within and outside of the collector light path can potentially be recycled. For recycling within the collector path, the system uses a diffractive collection mirror that concomitantly filters all laser and out-of-band radiation out of the EUV output. In this paper we review the optical design concept for power recycling and present preliminary plasma-physics simulation results showing a potential gain of 60% in EUV conversion efficiency.
Laser produced plasmas (LPPs) are currently a promising source of an efficient extreme ultraviolet (EUV) photon source production for advanced lithography. Optimum laser pulse parameters with adjusted wavelength, energy, and duration for a simple planar or spherical tin target can provide 2% to 3% conversion efficiency (CE) in laboratory experiments. Additional effects such as targets with complex geometry and tin-doped targets using prepulsing of laser beams can significantly increase CE. Recent studies showed that such improvements in an LPP system are due to reduction in laser energy losses by decreasing photons transmission (higher harmonic of Nd:yttrium-aluminum-garnet laser) or photons reflection (for CO2 laser). Optimization of target heating using prepulses or ablating low-density and nanoporous tin oxide can further improve LLP sources by creating more efficient plasma plumes and, as a result, increase CE, the most important parameter for EUV sources. We investigated the combined effects of prepulsing with various parameters and different target geometries on EUV conversion efficiency and on energetic ions production. The much higher reflectivity of CO2 laser from a tin target leads to two possible ways for system improvement using prepulses with shorter laser wavelengths or using more complex targets geometries with special grooves as developed previously by the authors.
Laser produced plasmas (LPP) is currently a promising source of an efficient extreme ultraviolet (EUV) photon source
production for advanced lithography. Optimum laser pulse parameters with adjusted wavelength, energy, and duration
for simple planar or spherical tin target can provide 2-3% conversion efficiency (CE) in laboratory experiments. These
values are also in good agreement with modeling results. Additional effects such as targets with complex geometry and
tin-doped targets using pre-pulsing of laser beams can significantly increase CE. Recent studies showed that such
improvements in LPP system are due to reduction in laser energy losses by decreasing photons transmission (higher
harmonic of Nd:YAG laser) or photons reflection (for CO2 laser). Optimization of target heating using pre-pulses or
ablating low-density and nanoporous tin oxide can further improve LLP sources by creating more efficient plasma
plumes and as a result increasing CE, the most important parameter for EUV sources. The second important challenge in
developing LPP devices is to decrease fast ions and target debris to protect the optical collection system and increase its
lifetime.
We investigated the combined effects of pre-pulsing with various parameters and different target geometries on EUV
conversion efficiency and on energetic ions production. The much higher reflectivity of CO2 laser from a tin target leads
to two possible ways for system improvement using pre-pulses with shorter laser wavelengths or using more complex
targets geometries with special grooves as developed previously by the authors.
Efficient laser systems are essential for the realization of high volume manufacturing in extreme ultraviolet lithography
(EUVL). Solid-state Nd:YAG lasers usually have lower efficiency and source suppliers are alternatively investigating
the use of high power CO2 laser systems. However, CO2 laser-produced plasmas (LPP) have specific characteristics and
features that should be taken into account when considering them as the light source for EUVL. The analysis of recent
experimental and theoretical work showed significant differences in the properties of plasma plumes produced by CO2
and the Nd:YAG lasers including EUV radiation emission, source formation, debris generation, and conversion
efficiency. The much higher reflectivity of CO2 laser from liquid, vapor, and plasma of a tin target results in the
production of optically thinner plumes with higher velocity and in a better formation of plasma properties (temperature
and density values) towards more efficient EUV source. However, the spikes in the temporal profiles of current CO2
laser will additionally affect the properties of the produced plasma. We have developed unique combination of state-of-the-art experimental facilities (CMUXE Laboratory) and advanced computer simulation (HEIGHTS) package for
studying and optimizing various lasers, discharge produced plasmas (DPP), and target parameters as well as the optical
collection system regarding EUV lithography. In this work, detailed characteristics of plasmas produced by CO2 and
Nd:YAG lasers were analyzed and compared both experimentally and theoretically for optimizing EUV from LPP sources. The details of lower overheating of plasma produced by CO2 laser are given with time and explain how to utilize the high reflectivity of such lasers in plasmas produced in different target geometries to significantly enhance the conversion efficiency of EUV radiation.
Extreme ultraviolet (EUV) lithography devices that use laser-produced plasma (LPP), discharge-produced plasma (DPP), and hybrid devices need to be optimized to achieve sufficient brightness with minimum debris generation to support the throughput requirements of high-volume manufacturing lithography exposure tools with a long lifetime. Source performance, debris mitigation, and reflector system are all critical to efficient EUV collection and component lifetime. Enhanced integrated models continue to be developed using the High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) computer package to simulate EUV photon emission, debris generation, and transport in both single and multiple laser beam interaction systems with various targets. A new Center for Materials under Extreme Environments (CMUXE) was recently established to benchmark HEIGHTS models for various EUV-related issues. The models being developed and enhanced were used to study the effect of plasma hydrodynamics evolution on the EUV radiation emission for planar and spherical geometry of a tin target and explain the higher conversion efficiency of a planar target in comparison to a spherical target. HEIGHTS can study multiple laser beams, various target geometries, and pre-pulses to optimize EUV photon production. Recent CMUXE and other experimental results are in good agreement with HEIGHTS simulation.
Extreme ultraviolet (EUV) lithography devices that use laser produced plasma (LPP), discharge produced plasma (DPP),
and hybrid devices need to be optimized to achieve sufficient brightness with minimum debris generation to support the
throughput requirements of High-Volume Manufacturing (HVM) lithography exposure tools with long lifetime. Source
performance, debris mitigation, and reflector system are all critical to efficient EUV collection and component lifetime.
Enhanced integrated models are continued to be developed using HEIGHTS computer package to simulate EUV
emission at high power and debris generation and transport in multiple and colliding LPP. A new center for materials
under extreme environments (CMUXE) is established to benchmark HEIGHTS models for various EUV related issues.
The models being developed and enhanced include, for example, new ideas and parameters of multiple laser beams in
different geometrical configurations and with different pre-pulses to maximize EUV production. Recent experimental
and theoretical work show large influence of the hydrodynamic processes on EUV generation. The effect of plasma
hydrodynamics evolution on the EUV radiation generation was analyzed for planar and spherical geometry of a tin target
in LPP devices. The higher efficiency of planar target in comparison to the spherical geometry was explained with better
hydrodynamic containment of the heated plasma. This is not the case if the plasma is slightly overheated. Recent
experimental results of the conversion efficiency (CE) of LPP are in good agreement with HEIGHTS simulation.
Current devices for EUV lithography combine both laser and discharge physics to achieve sufficient brightness with
minimum debris generation to support the throughput requirements of High-Volume Manufacturing (HVM) lithography
exposure tools with long lifetime. Source performance, Debris mitigation, and reflector system are critical to efficient
EUV collection and component lifetime. Integrated models are developed to simulate EUV emission at high power and
debris generation and transport in hybrid EUV devices. The models being developed include, for example, new ideas
and parameters of laser beams in discharge devices. In addition, optimization of source parameters, combination
magnetic fields and gas jet parameters to significantly reduce the debris, and mirror surface conditions to enhance the
reflectivity of EUV. Source optimization studies include full 3-D simulation of laser interaction with tin targets
followed by discharge simulation to produce the optimum EUV photons. Initial simulations show that for HVM devices
a combination of source optimization, innovative debris mitigation system, and understanding debris/mirror interaction
is required to achieve the lifetime needed.
Physical models are developed to investigate the following conditions relevant to discharge-produced plasma (DPP) devices under development for extreme ultraviolet (EUV) lithography: gaseous jet propagation in the chamber, removal of neutral particles with a gaseous jet, and deviation of charged particles with a magnetic field. Several geometries of the mitigation systems are considered for removing debris during the EUV lithographic process. The design of a mitigation system is proposed and simulated with the computer models. The behavior of Xe, Li, and Sn debris in Ar and He jets is simulated by using the high energy interaction with general heterogeneous target systems (HEIGHTS) integrated package. Final energy and local distributions are calculated using experimental debris data from current EUV facilities.
Both Laser and Discharge produced plasma (LPP and DPP) are being used as a light source for EUV lithography. A key
challenge for the EUV radiation plasma devices is achieving sufficient brightness to support the throughput requirements
of High-Volume Manufacturing lithography exposure tools. One method for improving source brightness is to simulate
the source environment in order to optimize the EUV output. An integrated model for the description of hydrodynamics
and optical processes in DPP and LPP devices has been developed and integrated into the HEIGHTS-EUV computer
simulation package. Model development consisted of several main tasks: plasma evolution and magnetohydrodynamic
(MHD) processes; detailed photon radiation transport, and physics of plasma/electrode interactions in DPP devices,
scattering processes of the neutral and charged particles of plasma. Advanced numerical methods for the description of
magnetic compression and diffusion in 2D and 3D geometries are used in the HEIGHTS package. Radiation transport of
both continuum and lines is taken into account with detailed spectral profiles in the EUV region. Monte Carlo methods
are used for the modeling of the radiation transport processes, laser radiation absorption, and the debris particles
behavior in magnetic field.
Discharge produced plasma (DPP) devices are being used as a light source for Extreme Ultraviolet (EUV) Lithography. A key challenge for DPP is achieving sufficient brightness to support the throughput requirements of exposure tools for high-volume manufacturing lithography. An integrated model is being developed to simulate the environment of the EUV source and optimize the output of the source. The model describes the hydrodynamic and optical processes that occur in DPP devices. It takes into account plasma evolution and magnetohydrodynamic processes as well as detailed photon radiation transport. The total variation diminishing scheme in the Lax-Friedrich formulation for the description of magnetic compression and diffusion in a cylindrical geometry is used. Several models are being developed for opacity calculations: a collisional radiation equilibrium model, a self-consistent field model with Auger processes, and a non-stationary kinetic model. Radiation transport for both continuum and lines with detailed spectral profiles is taken into account. The developed models are being integrated into the HEIGHTS-EUV computer simulation package. Preliminary results of a numerical simulation of xenon gas hydrodynamics and EUV radiation output are presented for various plasma conditions.
Discharge-produced plasma (DPP) devices have been proposed as a light source for EUV lithography. A key challenge for DPP is achieving sufficient brightness to support the throughput requirements of exposure tools for high-volume manufacturing lithography. To simulate the environment of the EUV source and optimize the output of the source, an integrated model is being developed to describe the hydrodynamic and optical processes that occur in DPP devices. The model includes both plasma evolution and magnetohydrodynamic processes as well as detailed photon radiation transport. The total variation diminishing scheme in the Lax-Friedrich formulation for the description of magnetic compression and diffusion in a cylindrical geometry is used. Several models are being developed for opacity calculations: a collisional radiation equilibrium model, a self-consistent field model with Auger processes, and a nonstationary kinetic model. Radiation transport for both continuum and lines with detailed spectral profiles are taken into account. The developed models are integrated into the HEIGHTS-EUV computer simulation package. Preliminary results of a numerical simulation of xenon gas hydrodynamics and EUV radiation output are presented for various plasma conditions.
Discharge produced plasma (DPP) devices have been proposed as a light source for EUV lithography. A key challenge for DPP is achieving sufficient brightness to support the throughput requirements of exposure tools for high-volume manufacturing lithography. To simulate the environment of the EUV source and optimize the output of the source, an integrated model is being developed to describe the hydrodynamic and optical processes that occur in DPP devices. The model includes both plasma evolution and magnetohydrodynamic processes as well as detailed photon radiation transport. The total variation diminishing scheme in the Lax-Friedrich formulation for the description of magnetic compression and diffusion in a cylindrical geometry is used. Several models are being developed for opacity calculations; a collisional radiation equilibrium model, a self-consistent field model with Auger processes, and a non-stationary kinetic model. Radiation transport for both continuum and lines with detailed spectral profiles are taken into account. The developed models are integrated into the HEIGHTS-EUV computer simulation package. Preliminary results of a numerical simulation of xenon gas hydrodynamics and line radiation output are presented for various plasma conditions.
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