O B Khristoforov

EUV sources using Xe and Sn discharge plasmas

This paper reports the basic results that have been obtained at the SRC RF TRINITI (the former Branch of the Kurchatov Institute of Atomic Energy). The work deals with the development of high power discharge produced plasma EUV sources that can meet the requirements of high volume manufacturing lithography tools. Solving the problem of extremely high thermal loads on the electrodes of a EUV source by moving away the electrode surfaces from the plasma and using both multi-discharge systems and rotating Sn-covered disc electrodes is discussed.

Development of high-power EUV sources for lithography

We report on the experimental status of the development of gas discharge produced plasma EUV sources for lithography based on the Z-pinch concept. The plasma size of approximately 1.3 mm X 1.5 mm has been matched to come close to the requirements resulting from the etendue of the optical system. The spatial stability of the plasma size as well as the plasma center is better than 15 percent standard deviation. The solid angle of emission is 1.8 sr, i.e. +/- 45 deg. The sources can be operated continuously at 1000 Hz repetition frequency and provide an EUV in-band power of 10 W in 1.8 sr. Spectral measurements providing in-band and out-of-band spectral distribution of the source are discussed.

High-power EUV sources for lithography: a comparison of laser-produced plasma and gas-discharge-produced plasma

Next generation semiconductor chip manufacturing using extreme ultraviolet (EUV) lithography requires a brilliant radiation source with output power between 50 W and 120 W in intermediate focus. This is about five to ten times higher power than that of current DUV excimer lasers used in optical lithography. Lifetime and cost of ownership however, need to be comparable to todays technology. In the present paper experimental results of both laser produced plasma and gas discharge produced plasma EUV source development at XTREME technologies - the EUV joint venture of Lambda Physik AG, Goettingen, and Jenoptik LOS GmbH, Jena, Germany - are presented. Source characterization has been performed with calibrated metrology tools for measurement of energy, power, size, spectra and stability of the EUV emission. The laser plasma investigations are performed with a 1st experimental facility comprising a commercial 40 W Nd:YAG laser coupled to a liquid xenon-jet target system, which was developed by XTREME technologies. The EUV in-band power emitted from the 0.25 mm diameter plasma into 2p solid angle is 0.2 W, the conversion efficiency amounts 0.5 percent. Estimated EUV emission parameters using a 500 W laser for plasma generation to be installed in spring 2002 are discussed. The gas discharge EUV sources described here are based on efficient Xenon Z-pinches. In the 3rd prototype generation the plasma pinch size and the available emission angle have been matched to the etendue of the optical system of 2-3 mm2. The solid angle of emission from the pinch of 1.3 mm x 1.5 mm amounts 1.8 sr. The Z-pinch EUV source can be operated continuously at 1000 Hz with an in-band output power of 10 W in 1.8 sr. This corresponds to 4.5 W in intermediate focus, if no spectral purity filter is needed. The power emitted into a solid angle of 2p sr is 35 W. Emission energy stability ranges between 1 percent and 4 percent standard deviation. Spectral, temporal as well as spatial emission characteristics of the discharge source in dependence on the gas discharge geometry have been evaluated. The potentials as well as limits for power scaling of the two technological source concepts are discussed.

Compact Z-pinch EUV source for photolithography

According to Sematech Internationals analysis extreme ultraviolet (EUV) photolithography is one of the most promising approaches for next generation lithography (NGL). The insertion point of NGL is likely at the 50 nm node. To establish EUV lithography all basic technologies have to be developed t material suppliers, source suppliers, coating manufacturers, optics, lens and tool manufacturers, mask houses, pellicle manufacturers and resist suppliers over the next years. To achieve the required throughput in production various concepts of EUV sources are currently under investigation. Here we discuss new results of design studies on gas discharge Z-pinch sources. Form the EUV source 1 W output power at 100 Hz repetition rate could be obtained in continuous operation. Pulse energy stability is 4% (sigma). In burst operation repetition rate of up to 400 Hz is possible with the current design.

Development of Linear Sequential Lateral Solidification Technique to Fabricate Quasi-Single-Crystal Super-Thin Si Films for High-Performance Thin Film Transistor Devices

Sequential Lateral Solidification (SLS) [1], and Single-Crystal Sequential Lateral Solidification (SCSLS) [2] techniques have been recently proposed by the Columbia University group in order to recrystallize amorphous silicon precursor films into layers with crystalline quality close to single-crystal films. These new methods facilitate superior quality and uniformity of Si films formed on low-temperature glasses compared to the conventional excimer-crystallization techniques. The methods have great significance for Thin Film Transistor (TFT) applications, especially for driver- and systemintegrated Liquid-Crystal Displays (LCDs). However, the new techniques, as previously demonstrated [1,2], have certain features that may be further improved. In particular, one notes that: (1) only a small part of the laser energy is actually used for crystallization; (2) if only a single beam is used, then the crystallization rate will be rather low; (3) in addition, previous results have used relatively thick films only.

Kilowatt-range high-repetition-rate excimer lasers

High-power operation of excimer lasers was investigated using UV-preionization schemes based on a dielectric surface creeping discharge. The design and operation of the high average power excimer laser systems are described. A large-aperture (10 X 7 cm2) XeCl laser with UV preionization can produce 10 J per pulse at a repetition rate of up to 100 Hz. When the aperture was decreased, the XeCl laser operated at repetition rates of up to 500 Hz and could produce average output power of more than 600 W.

High-average-power excimer lasers

A review of recent achievements and new tendencies in the development high energy, high repetition rate excimer lasers will be presented. The paper mainly focuses on the features of KrF, XeCl lasers with different combinations of output energy x pulse repetition frequency, for example: 1 J X 600 Hz (KrF); 3 J X 200 Hz or 10 J X 100 Hz (XeCl), which have been developed as candidates for industrial applications.

Discharge produced plasma source for EUV lithography

Extreme ultraviolet (EUV) radiation is seen as the most promising candidate for the next generation of lithography and semiconductor chip manufacturing for the 32 nm node and below. The paper describes experimental results obtained with discharge produced plasma (DPP) sources based on pinch effect in a Xe and Sn vapour as potential tool for the EUV lithography. Problems of DPP source development are discussed.

High-power gas-discharge EUV source

The results from studies aimed at creating a high-power high-repetition-rate gas-discharge EUV source based on xenon Z-pinch are presented. In a liquid-cooled EUV source prototype, an average output power of 10 W for the burst mode (∼1 s) and 5 W for continuous operation, emitted into a solid angle of 0.25 sr and 2% bandwidth around 13.5 nm is attained at a repetition rate of ∼1 kHz. Operating wavelength of the source corresponds to XeXI 13.5-nm ion emission band. It is experimentally shown that the size of the emitting hot plasma can be decreased to ∼2 mm without loss in the average output power. The radiation characteristics were determined by using standard techniques and calibrated metrology tools, which allowed a comparison of the absolute values of the measured parameters with the available data on other EUV sources developed for the next-generation lithography with a resolution of ∼50 nm. The attained level of an average EUV power of 10 W at λ=13.5 nm into the 0.25-sr solid angle and 2% bandwidth is one of the highest at the moment.

Prospects for high-power high-repetition-rate industrial excimer lasers

Recent progress in excirner laser technology developed at TRINITI is reported. The key of the technologT is a combination of simple reliable UV preionizer based on creeping discharge on surface of a sapphire plate and the compact highly efficient gas flow system. This technology allows to develop very compact, high power, high repetition rate models of excimer lasers capable to deliver stabilized average power up to 500W (XeC1, KrF), 250W (ArF) and realise pulse repetition rate of more then 5 kHz..