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Simulation results showing the spatial variation of plasma parameters: electron temperatures (Te), axial velocity (Vz), conductivity (σ) and mean charge state (<Z>) at the moment of discharge breakdown for the ps- and ns-laser.
Source publication
Extreme ultraviolet (EUV) light generation by hybrid laser-assisted vacuum arc discharge plasmas, utilizing Sn-coated rotating-disc-electrodes, was investigated. The discharge was initiated by localized ablation of the liquid tin coating of the cathode disc by a laser pulse. The laser pulse, at 1064 nm, was generated by Nd:YAG lasers with variable...
Citations
... Beyene et al. showed that the trigger laser energy and pulse duration affect EUV CE and spectral efficiency in the LDP system. 19 Since the plasma state just before starting the discharge influences EUV emission, high-intensity or short-pulse laser irradiation can increase the number of emitted tin ions or the ion charge state. ...
Laser-assisted discharge-produced plasma (LDP) is one of the ways to generate extreme ultraviolet (EUV) light used in the semiconductor manufacturing processes. This light source uses a pulsed laser and a high-current pulsed electrical discharge to make a high-temperature and high-density tin plasma. One of two rotating disk electrodes, of which surfaces are coated by liquid tin (Sn), is irradiated by the laser to produce tin plasma. The plasma propagates from one electrode (cathode) to the other (anode) and ignites an electrical breakdown between the electrodes. The low-inductance circuit connected to the electrodes provides a current of approximately 15 kA and 150 ns to the tin plasma. The plasma implodes due to its own magnetic pressure, and EUV radiation is emitted from the resultant hot and dense plasma. High-speed ions are also emitted from the plasma and limit the lifetime of the mirror used to collect the EUV light. We need to maximize the light emission and minimize the ion emission. The role of the laser is essential in the LDP EUV source not only to ignite the discharge but also to condition the initial plasma. It influences EUV energy, EUV brightness, and emitted ion speed distribution of the plasma. The experiment suggested that laser intensity higher than 25 GW/cm² produced high EUV brightness and low emitted ion speed.
... 在30 eV, 10 18 cm -3 左右. 2016年, Tsygvintsev等 [14] 模拟发现在LDP的电流上升初期和中期分别存在 着Z箍缩和微箍缩两种机制, 两者共同影响EUV 的产生. 2016年, Beyene等 [15] 采用Z* code对皮 秒和纳秒激光诱导圆盘电极放电进行模拟, 该研究 发现皮秒激光诱导放电形成的等离子体的温度、轴 向速度、电导率和电离度均要高于纳秒情况, EUV 辐射功率更强. ...
Extreme ultraviolet (EUV) light source is an important part of EUV lithography system in semiconductor manufacturing. The EUV light source requires that the 4p⁶4dⁿ-4p⁵4dⁿ⁺¹ + 4dⁿ⁻¹4f transitions of Sn8+~13+ ions emit thousands of lines which form unresolved transition arrays near 13.5 nm. Laser-induced discharge plasma is one of the important technical means to excite target into an appropriate plasma condition. Laser-induced discharge plasma has a simple structure and a low cost. It also has important applications in mask inspection, microscopic imaging, and spectral metrology. In the design and production process, there are many factors that can influence the conversion efficiency, such as current, electrode shape, and laser power density. The simulation method is a convenient way to provide guidance for optimizing the parameters. In this paper, a completed radiation magneto-hydrodynamic model is used to explore the dynamic characteristics of laser-induced discharge plasma and its EUV radiation characteristics. To improve the accuracy, a more detailed global equation of state model, an atomic structure calculation model including relativistic effect and a collision radiation model are proposed simultaneously. The simulation reconstructs the discharge process effectively, which is divided into five stages in the first half cycle of current, including expansion of laser plasma, column formation of discharge plasma, diffusion of discharge plasma, contraction of discharge plasma, and re-diffusion of discharge plasma. It is revealed that the pinch effect during the current rising time exerts a significant influence on the generation of EUV radiation. The conversion efficiency of EUV radiation is still low under our existing conditions, and hopefully a higher rising rate of current can improve the conversion efficiency in the future work.
... 在30 eV, 10 18 cm -3 左右. 2016年, Tsygvintsev等 [14] 模拟发现在LDP的电流上升初期和中期分别存 在Z箍缩和微箍缩两种机制, 两者共同影响EUV 的产生. 2016年, Beyene等 [15] 采用Z* code对皮 秒和纳秒激光诱导圆盘电极放电进行模拟, 该研究 发现皮秒激光诱导放电形成的等离子体的温度、轴 向速度、电导率和电离度均要高于纳秒情况, EUV 辐射功率更强. ...
Laser induced discharge plasma is one of the important technical means for extreme ultraviolet light source. In this paper, a radiation magneto-hydrodynamic model based on a global equation of state model, an atomic structure calculation model and a collision radiation model is proposed to simulate the dynamic characteristics of laser induced discharge plasma and its extreme ultraviolet radiation characteristics. The simulation reproduced the pinch phenomenon during the discharge process, and the conversion efficiency of extreme ultraviolet light obtained was consistent with the experiment result.
... [10] In 2011, Banine et al. compared the EUVemitting plasma characteristics such as spectra, formation of the plasma, and associated debris production in LDP source and LPP source. [11] In 2012, Schriever et al. illustrated that LDP was a simpler concept than LPP, indicating its advantages in the key technologies, such as power delivery and target material delivery. [12] Generally speaking, the conversion efficiency (CE) of Xe-GDPP needs to be improved and the cost of LPP is too high, but the Sn-LDP has the features of low cost, simple structure, reliable stability, high wallplug efficiency, and high target utilization efficiency. ...
Extreme ultraviolet (EUV) source produced by laser-induced discharge plasma (LDP) is a potential technical means in inspection and metrology. A pulsed Nd:YAG laser is focused on a tin plate to produce an initial plasma thereby triggering a discharge between high-voltage electrodes in a vacuum system. The process of micro-pinch formation during the current rising is recorded by a time-resolved intensified charge couple device camera. The evolution of electron temperature and density of LDP are obtained by optical emission spectrometry. An extreme ultraviolet spectrometer is built up to investigate the EUV spectrum of Sn LDP at 13.5 nm. The laser and discharge parameters such as laser energy, voltage, gap distance, and anode shape can influence the EUV emission.
... Pawlowski et al. hold a patent on the concept of using rotating wheels, covered with liquid tin, to produce EUV light from a laserassisted discharge plasma (LDP). In LDP sources, ∼ ns laser pulse impact (also ∼ ps pulses have been studied by Beyene et al. [11] for this purpose) ignites a first plasma, as well as a corresponding splash, between the rotating wheels serving as electrodes. These wheel electrodes subsequently discharge and produce a hot and dense tin plasma [12]. ...
The splash created by intense laser pulse impact onto a liquid tin layer is studied experimentally using time-delayed stroboscopic shadowgraphy. An 8-ns infrared (1064 nm) laser pulse is focused onto a deep liquid tin pool. Various laser spot sizes (70, 120, and 130 μ\upmum in diameter) and various laser pulse energies (ranging 2.5–30 mJ) are used, resulting in laser fluences of ∼ 10–1000 J/cm2 inducing pronounced splashing. Specifically, we study the time evolution of the splash crown-width. The crown width expansion velocity is found to be linearly dependent on the laser energy, and independent of the focal spot size. A collapse of all crown width evolution data onto a single master curve confirms that the hydrodynamic evolution of our laser-impact-induced splash is equivalent to droplet-impact-induced splashing. Laser-impact splashing is particularly relevant, e.g. for high-brightness laser-assisted discharge-produced plasma and laser-produced plasma sources of extreme ultraviolet light for nanolithography.
... After years of research, DPP light source has developed into a laser induced discharge plasma (LDP) light source [6]. Since 2003, Phillips and XTREME Technologies GmbH [7] set up a new kind of LDP source, LDP has made great progress especially after using the Sn-coated rotating disc electrodes [8]. LDP combines the advantages of high stability of DPP and power scalability of laser-produced plasma (LPP) [9]. ...
... The conversion efficiency of EUV radiation is roughly estimated. The conversion efficiency (CE) was defined as the ratio of the sum of photon energy Q EUV (with a central wavelength of 13.5 nm and a bandwidth of 2%) to the sum of laser energy Q laser and capacitive storage energy Q discharge , as shown in Eq. (8). ...
In this paper, a CO2 laser induced discharge plasma extreme ultraviolet (EUV) source experimental device was established. The optical emission spectroscopy was used to diagnose the characteristics of the plasma, and the evolution of electron temperature and electron density with time was obtained. The influence of discharge voltage on plasma parameters was analyzed and discussed. The EUV radiation characteristics of the plasma were investigated by self-made grazing incidence EUV spectrometer. The EUV radiation intensity and conversion efficiency were discussed.
... Due to the high convention efficiency of 13.5 nm emission, Sn has been widely used as an extreme ultraviolet (EUV) source [4]. Two types of EUV sources are used for EUVL, which are laser-produced plasma (LPP) [5,6] and laser-triggered discharge plasma (LTD) [7]. The LTD source has the features of being a low-cost system, high repetition rate, selective spectral wavelength according to target, potential high repetition-rate operation, and precise timing controllability of a light pulse. ...
... The latter studies the EUV spectra generated by picosecond and nanosecond laser triggering under different laser energy. It reports that ps-triggering is better in order to get a higher EUV conversion efficiency and narrower spectral profiles [7]. Moreover, the effect of current rise time, electrical energy, and inter-electrode distance are also reported [16,17]. ...
... The LTD plasma is optically thin when comparing it with the LPP plasma [7]. In this way, the opacity effect is ignored. ...
The effect of laser-current delay on extreme ultraviolet emission by laser-triggered discharge-plasma has been investigated. Typical waveforms for current, voltage, laser signals, and X-ray signals have been compared. Theoretical tin spectra were simulated among the electron temperature ranges from 10 to 50 eV to compare with the experimental results. The results show that longer laser-current delay time is propitious to increase the steady-state time of plasma at high temperatures, and it increases the intensity and spectral purity of 13.5 nm emission in 2% band. The 13.5 nm radiation intensity increases about 120% with the delay increasing from 0.7 to 5 μs, and the extreme ultraviolet (EUV) emission conversion efficiency (CE) increases from 0.5% to 1.1%.
... Due to the high convention efficiency of 13.5 nm emission, Sn has been widely used as an extreme ultraviolet (EUV) source [4]. Two types of EUV sources are used for EUVL, which are laser-produced plasma (LPP) [5,6] and laser-triggered discharge plasma (LTD) [7]. The LTD source has the features of being a low-cost system, high repetition rate, selective spectral wavelength according to target, potential high repetition-rate operation, and precise timing controllability of a light pulse. ...
... The latter studies the EUV spectra generated by picosecond and nanosecond laser triggering under different laser energy. It reports that ps-triggering is better in order to get a higher EUV conversion efficiency and narrower spectral profiles [7]. Moreover, the effect of current rise time, electrical energy, and inter-electrode distance are also reported [16,17]. ...
... The LTD plasma is optically thin when comparing it with the LPP plasma [7]. In this way, the opacity effect is ignored. ...
... After the laser shot, the plasma state changes with time. The expansion process of pre-plasma induced by the laser affects the subsequent pinch process and the radiant properties of the pinch [19]. Different laser-current delays lead to changes in the Z-pinch process. ...
... At this time, there are mainly Gd 17+~G d 20+ ions in the plasma. The LTD plasma is optically thin compared with the LPP plasma from early research [19], so opacity effects are ignored, as well as the effects of satellite emission. Figure 7 shows the theoretical Gd spectra as a function of electron temperature and wavelength between the electron temperatures 40 and 140 eV, and the theoretical spectra are convolutions of a Gaussian instrumental function. ...
... Figure 7 shows the theoretical Gd spectra as a function of electron temperature and wavelength between the electron temperatures 40 and 140 eV, and the theoretical spectra are convolutions of a Gaussian instrumental function. The LTD plasma is optically thin compared with the LPP plasma from early research [19], so opacity effects are ignored, as well as the effects of satellite emission. Figure 7 shows the theoretical Gd spectra as a function of electron temperature and wavelength between the electron temperatures 40 and 140 eV, and the theoretical spectra are convolutions of a Gaussian instrumental function. ...
We demonstrate the beyond extreme ultraviolet (BEUV) emission by a laser-triggered discharge source with the laser-current delay between 0.6 µs and 3 µs. The spectra at different electron temperatures are simulated theoretically, and the spectra at different laser-current delays are measured experimentally. The theoretical and experimental results show that the lower vapor velocity at longer laser-current delay time is beneficial for increasing the steady-state time of plasma at high temperature, thereby increasing the output intensity and spectral purity of 6.76 nm. The radiation intensity of 6.76 nm (0.6% bandwidth) increases about 240% when the delay increases from 0.6 to 3 μs.
The extreme ultraviolet (EUV) lithography technology, which is required for high-end chip manufacturing, is the first of 35 "neck stuck" key core technologies that China is facing currently. The EUV source with high conversion efficiency is an important part of EUV lithography system. The experiment on dual-pulse irradiated Gd target is carried out to realize the stronger 6.7 nm EUV emission output. Firstly, we compute the contribution of transition arrays of the form 4p–4d and 4d–4f from their open 4d subshell in charge states Gd¹⁸⁺–Gd²⁷⁺, and transition arrays of the form 4d–4f from their open 4d subshell in charge states Gd¹⁴⁺–Gd¹⁷⁺ on the near 6.7 nm EUV source. Subsequently, the experimental results of the dual pulse laser irradiated Gd target show that the intensity of 6.7 nm peak EUV emission decreases first, then increases and drops again due to the plasma density decreasing gradually when the delay time between the pre-pulse and main-pulse increases from 0–500 ns. The strongest intensity of 6.7 nm peak EUV emission is generated when the delay time is 100 ns. At the same time, the spectrum efficiency is higher when the delay time is 100 ns, which is 33% higher than that of single pulse laser. In addition, the experimental results show that the half width of EUV spectrum produced by dual pulse in the delay between 10–500 ns is narrower than that of signal laser pulse due to the fact that the method of dual pulse can suppress the self-absorption effect. The half width is the narrowest when the delay is 30 ns, which is about 1/3 time of EUV spectrum width generated by a single pulse. At the same time, the narrowing of Gd EUV spectrum improves the spectral utilization efficiency near 6.7 nm wavelength (within 0.6% bandwidth).
