Yusuke Teramoto

Development of Xe‑and Sn‑fueled high‑power Z‑pinch EUV source aiming at HVM

Discharge-produced plasma (DPP) based EUV source is being developed at Gotenba Branch of EUVA Hiratsuka R&D Center. Among the several kinds of discharge scheme, Z-pinch is employed in our source. An all-solid-state magnetic pulse compression (MPC) generator is used to create a Z-pinch plasma. Low inductance MPC generator is capable of producing a pulsed current with over 50 kA of peak amplitude and about 100 ns of pulse duration at 7 kHz of pulse repetition frequency. In order to obtain sufficient output radiation power, tin-containing gas is being used as well as xenon. Due to the high spectral efficiency of tin, demonstrated EUV output power reached 645 W/2πsr within 2% bandwidth around 13.5 nm. A novel scheme of fuel gas supply led to as good output energy stability as xenon can achieve. Using a nested grazing-incidence collector, EUV power at intermediate focus point which is defined as an interface to the exposure tool reached 42 W with 3.3 mm2sr of etendue.

Cable guns as a plasma source in a plasma opening switch

The characteristics of a plasma generated by cable plasma guns have been studied by a laser interferometer. Cable plasma guns are frequently used as a plasma source in plasma opening switches. In our experiments, the plasma source consists of eight coaxial cable guns mounted on the outer electrode of concentric coaxial electrodes. The reproducibility of the gun in subsequent shots is found to be better than 10%, and the gun-to-gun difference is less than 15%. Assuming a symmetry of eight guns, the contour maps of the electron plasma density are plotted as functions of time. The plasma density becomes maximum near the gun nozzle and near the inner coaxial electrode. The plasma density is low in the area between the coaxial electrodes during the early time of the discharge. At a later time, the plasma fills the space between the two guns more uniformly. Still photographs of the plasma luminosity show a good correspondence with the plasma density plots which were taken 10 /spl mu/s after the discharge initiation. The plasma gun system is designed for use in a 400-kA inductive voltage adder with the inductive energy storage system.

Tin DPP Source Collector Module (SoCoMo): Status of Beta products and HVM developments

For industrial EUV (extreme ultra-violet) lithography applications high power EUV light sources are needed at a central wavelength of 13.5 nm. Philips Extreme UV GmbH, EUVA and XTREME technologies GmbH have jointly developed tin DPP (Discharge Produced Plasma) source systems. This paper focuses in the first part on the results achieved from the Alpha EUV sources in the field. After integration of power upgrades in the past, now the focus is on reliability and uptime of the systems. The second part of this paper deals with the Beta SoCoMo that can be used in the first pre-production scanner tools of the lithography equipment makers. The performance will be shown in terms of power at Intermediate Focus, dose stability and product reliability but also its reachable collector lifetime, the dominant factor for Cost of Operation. In the third part of the paper the developments for the high volume manufacturing (HVM) phase are described. The basic engineering challenges in thermal scaling of the source and in debris mitigation can be proven to be solvable in practice based on the Beta implementation and related modeling calibrated with these designs. Further efficiency improvements required for the HVM phase will also be shown based on experiments. The further HVM roadmap can thus be realized as evolutionary steps from the Beta products.

All-solid-state triggerless repetitive pulsed power generator utilizing a semiconductor opening switch

The repetitive pulsed power generator was constructed with the semiconductor opening switch (SOS) realizing the pulse compression by inductive energy storage scheme. For the preliminary pulse compression, the magnetic pulse compression system was employed. The saturable inductors and transformers transferred the stored electrical energy from the primary storage capacitor to the SOS compressing the pulse. For the final stage of the generator, the SOS was used. At the time when the SOS interrupts the current, the inductive energy stored in the circuit inductance is quickly released and transferred to the load. By tuning the current fed to the SOS, the amplitude and pulse width of the generated voltage at the 300-/spl Omega/ resistive load were 150 kV and 60 ns, respectively. The SOS allows the decrease in size, hence cost of the generator, and improves the reproducibility and reliability under the repetitive operation. Moreover, the system does not require gas discharge-based spark-gap switches or semiconductor closing switches accompanying an external trigger source, and can operate at 60 pps. Such all solid configuration and exclusion of possibility of miss-firing provide easy-to-use generator system and long lifetime.

Development of Sn-fueled high-power DPP EUV source for enabling HVM

Discharge-produced plasma (DPP)-based EUV source is being developed at Gotenba Branch of EUVA Hiratsuka R&D Center. A high-repetition-rate high voltage power supply (HVPS) was developed and put into operation on the magnetic pulse compression (MPC)-driven DPP source, enabling 8-kHz operation with 15 J/pulse of maximum charging energy and 0.11 % of stability. SnH4 gas was used as a fuel gas in order to obtain high conversion efficiency. SnH4-fueled Z-pinch source demonstrated EUV power of 700 W/2&pgr;sr within 2 % bandwidth around 13.5 nm. Using a nested grazing-incidence collector, EUV power at the intermediate focus which is defined as an interface to the exposure tool reached 62 W with 3.3 mm2sr of etendue. Tin deposition rate on the collector surface, which is the concern in any tin-fueled EUV sources, was decreased by four orders of magnitude as a result of debris-shield development. Cleaning processes were also developed to enhance total lifetime of the collector. A sequence of intentional deposition and cleaning process for the ruthenium grazing-incidence mirror sample was repeated 13 times. By measuring reflectivity of the mirror, it was confirmed that halogen cleaning process worked very effectively and did not get the mirror damaged after such a long-term cleaning experiment.

Tin DPP source collector module (SoCoMo) ready for integration into Beta scanner

As the traditional techniques used in optical photolithography at 193 nm are running out of steam and are becoming prohibitively expensive, a new cost-effective, high power EUV (extreme ultra-violet) light source is needed to enable high volume manufacturing (HVM) of ever shrinking semiconductor devices. XTREME technologies GmbH and EUVA have jointly developed tin based LDP (Laser assisted Discharge Plasma) source systems during the last two years for the integration of such sources into scanners of the latest and future generations. The goals of the consortium are 1) to solve the wavelength gap - the growing gap between the printed critical dimensions (CD) driven by Moores Law and the printing capability of lithographic exposure tools constrained by the wavelength of the light source - and 2) to enable the timely availability of EUV light sources for high volume manufacturing. A first Beta EUV Source Collector Module (SoCoMo) containing a tin based laser assisted discharge plasma source is in operation at XTREME technologies since September 2009. Alongside the power increase, the main focus of work emphasizes on the improvement of uptime and reliability of the system leveraging years of experience with the Alpha sources. Over the past period, a cumulated EUV dose of several hundreds of Mega Joules of EUV light has been generated at the intermediate focus, capable to expose more than a hundred thousand wafers with the right dose stability to create well-yielding transistors. During the last months, the entire system achieved an uptime - calculated according to the SEMI standards - of up to 80 %. This new SoCoMo has been successfully integrated and tested with a pre-production scanner and is now ready for first wafer exposures at a customers site. In this paper we will emphasize what our innovative concept is against old type of Xe DPP and we will present the recent status of this system like power level, uptime and lifetime of components as well. In the second part of the paper the EUV source developments for the HVM phase are described. The basic engineering challenges are thermal scaling of the source and debris mitigation. Feasibility of the performance can be demonstrated by experimental results after the implementation into the beta system. The feasibility of further efficiency improvement, required for the HVM phase, will also be shown. The objectives of the HVM roadmap will be achieved through evolutionary steps from the current Beta products.

High-repetition-rate MPC generator-driven capillary Z-pinch EUV source

Discharge-produced plasma (DPP) based EUV source have been studied and developed at EUVA/Gotenba Branch. Among the several kinds of discharge scheme, a capillary Z-pinch has been employed in our source. An all-solid-state magnetic pulse compression (MPC) generator was used to create a Z-pinch plasma. Low inductance MPC generator provides a pulsed current with about 17 kA of peak amplitude and 350 ns of pulse duration, and allows 2-kHz continuous operation. A water-cooled discharge head was coupled with the MPC generator. In order to evaluate the source performance, electrical energy input to the discharge, EUV radiation power, radiation spatial profile, pinhole image and spectra were observed. 54.4 W/2%BW of 13.5-nm EUV output was achieved at 2-kHz operation. Through the radiation profile measurement and pinhole-camera observation, spatial image of EUV radiation was understood.

High-power and high-repetition-rate EUV source based on Xe discharge-produced plasma

Discharge-produced plasma (DPP) based EUV source have been studied and developed at EUVA/Gotenba Branch. Among the several kinds of discharge scheme, a capillary Z-pinch has been employed in our source. An all-solid-state magnetic pulse compression (MPC) generator was used to create a Z-pinch plasma. Low inductance MPC generator provides a pulsed current with about 52 kA of peak amplitude and 120 ns of pulse duration, and allows 7-kHz operation. A water-cooled discharge head was coupled with the MPC generator. In order to evaluate the source performance, electrical energy input to the discharge, EUV radiation power, radiation spatial profile, plasma image and spectra were observed. In-band EUV power into usable solid angle obtained at 7 kHz was 93 W/2%BW. By using nested grazing-incidence collector, EUV power at intermediate focus obtained was 19 W/2%BW.

Development of Xe-filled capillary discharge extreme-ultraviolet radiation source for semiconductor lithography

An EUV radiation source development with discharge-produced plasma (DPP) has been started in Gotenba branch of EUVA Hiratsuka R&D center. For the early stage of the development, fundamental characteristics of DPP including current, voltage, EUV energy and spectrum in EUV region were studied. A capillary of which the inner diameter was 2.3 mm, and Xe gas were used as a source to be expected in-band EUV radiation from magnetically-compressed Z-pinch plasma. An all-solid-state magnetic pulse compression generator was employed, which can deliver the current of 14 kA into the capillary load with the rise time of approximately 500 ns. In-band EUV energy and spectroscopic measurements were carried out. It was found that the in-band EUV energy increased with increasing the current amplitude and/or pressure of filled Xe gas. The highest in-band EUV energy obtained was 8 mJ per unit solid angle.

Unstable Behavior in Exploding Wire Array

Although considerable investigations have been reported on z-pinches to achieve nuclear fusion, little attention has been given from the point of view of how a wire array consisting of many parallel wires explodes. In this paper, the unstable behavior of a wire array is investigated. The instability occurs by the deviation from the homogeneous current flow through many wires. The expressions discriminating between the stability and the instability are derived. Using the resistivity variation of the wire, the unstable behavior during the explosion of the wires is predicted and the strength of the tendency to an unstable behavior is evaluated. The unstable region on a map of resistivities is independent of the wire number while the strength of the tendency to the unstable behavior depends on the wire number.