Powerful extreme ultraviolet (EUV) sources at 13.5 nm are a prerequisite for the economical operation of lithography scanners for semi-conductor manufacturing. These sources have been under development for more than 10 years. At the beginning, many source concepts were considered. Compact technologies like dense plasma focus or capillary Z-pinch discharges reached very rapidly fundamental limits as far as power scalability and lifetime were concerned. Other complex technologies-like synchrotrons-eventually dropped out of the race as well, exceeding by far the footprint and cost targets. Over time, the technology solidified toward the two source concepts: on one hand, the discharge produced plasmas (DPP), which eventually led to the development of the current laser-assisted discharge plasma (LDP); on the other hand, the laser-produced plasmas (LPP). All these technologies generate hot and dense plasmas of similar properties, which emit EUV radiations efficiently as a black body radiator or Planck emitter, in a pulsed manner. The plasma generation method, however, is quite different. DPP uses a pulsed high-voltage current discharge to generate plasma heating a gaseous or vaporized material up to temperatures close to 200,000°C. As for LPP, microscopic droplets of molten tin are fired through a vacuum chamber, individually tracked, vaporized by a pre-pulse laser, and eventually irradiated by a pulsed high-power infrared CO2 laser at 50 to 100 kHz, creating a high-temperature tin plasma, which radiates EUV light. In the case of LDP the plasma is generated between two rotating discs. Partially immersed in baths filled with liquid tin, the discs are wetted and covered with a thin layer of liquid tin. A pulsed laser beam focused on one of the discs evaporates a small amount of tin and generates a tin cloud between the two discs. Next a capacitor bank, which is connected to the discs via the liquid tin, discharges and converts the tin cloud into a plasma heated up to 200,000°C as well.
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 Moore's 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 customer's 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.
For industrial EUV (extreme ultra-violet) lithography applications high power extreme ultraviolet (EUV) light sources are needed at a central wavelength of 13.5 nm, targeting 32 nm node and below. Philips Extreme UV GmbH and XTREME technologies GmbH have developed DPP (Discharge Produced Plasma) Alpha tools which run in operation at several locations in the world. In this paper the status of the Alpha Sn-DPP tools as developed by Philips Extreme UV GmbH will be given. The Alpha DPP tools provide a good basis for the development and engineering of the Beta tools and in the future of the HVM tools. The first Beta source has been designed and first light has been produced. Engineering steps will folow to optimize this first generation Beta Sn-DPP source. HVM tools target EUV power levels from 200W to 500W in IF. In this paper we show that the power requried for HVM can be generated with Sn-DPP sources. Based on Alpha Sn-DPP sources we show that repetition frequency and generated EUV pulse energy is scalable up to power levels that match the HVM requirements.
In this paper, we report on the recent progress of the Philips Extreme UV source. The Philips source concept is based on a discharge plasma ignited in a Sn vapor plume that is ablated by a laser pulse. Using rotating electrodes covered with a regenerating tin surface, the problems of electrode erosion and power scaling are fundamentally solved.
Most of the work of the past year has been dedicated to develop a lamp system which is operating very reliably and stable under full scanner remote control. Topics addressed were the development of the scanner interface, a dose control system, thermo-mechanical design, positional stability of the source, tin handling, and many more.
The resulting EUV source-the Philips NovaTin(R) source-can operate at more than 10kW electrical input power and delivers 200W in-band EUV into 2π continuously. The source is very small, so nearly 100% of the EUV radiation can be collected within etendue limits. The lamp system is fully automated and can operate unattended under full scanner remote control. 500 Million shots of continuous operation without interruption have been realized, electrode lifetime is at least 2 Billion shots. Three sources are currently being prepared, two of them will be integrated into the first EUV Alpha Demonstration tools of ASML.
The debris problem was reduced to a level which is well acceptable for scanner operation. First, a considerable reduction of the Sn emission of the source has been realized. The debris mitigation system is based on a two-step concept using a foil trap based stage and a chemical cleaning stage. Both steps were improved considerably. A collector lifetime of 1 Billion shots is achieved, after this operating time a cleaning would be applied. The cleaning step has been verified to work with tolerable Sn residues. From the experimental results, a total collector lifetime of more than 10 Billion shots can be expected.
The paper describes recent progress in the development of the Philips's EUV source. Progress has been realized at many frontiers: Integration studies of the source into a scanner have primarily been studied on the Xe source because it has a high degree of maturity. We report on integration with a collector, associated collector lifetime and optical characteristics. Collector lifetime in excess of 1 bln shots could be demonstrated. Next, an active dose control system was developed and tested on the Xe lamp. Resulting dose stability data are less than 0.2% for an exposure window of 100 pulses. The second part of the paper reports on progress in the development of the Philips' Sn source. First, the details of the concept are described. It is based on a Laser triggered vacuum arc, which is an extension with respect to previous designs. The source is furbished with rotating electrodes that are covered with a Sn film that is constantly regenerated. Hence by the very design of the source, it is scalable to very high power levels, and moreover has fundamentally solved the notorious problem of electrode erosion. Power values of 260 W in 2p sr are reported, along with a stable, long life operation of the lamp. The paper also addresses the problem of debris generation and mitigation of the Sn-source. The problem is attacked by a combined strategy of protection of the collector by traditional means (e.g. fields, foiltraps... ), and by designing the gas atmosphere according to the principles of the well known halogen cycles in incandescent lamps. These principles have been studied in the Lighting industry for decades and rely on the excessively high vapor pressures of metal halides. Transferred to the Sn source, it allows pumping away tin residues that would otherwise irreversibly deposit on the collector.
The paper describes progress of the Philips’ hollow cathode triggered (HCT) gas discharge EUV source. The program
has been focussed on three major areas: (1) Studying the basic physics of ignition, pinch formation and EUV
generation. The paper reports on progress in this area and particularly describes the underlying atomic physics both for
Xe and Sn. (2) Discharge based on Sn. Results on overall efficiency more than 5 times the Xe efficiency are reported as
well as high frequency operation up to 6.5 kHz. This system shows all the necessary ingredients for scaling to
production power levels. (3) Integration of the Xe source in an alpha tool. Results on integration issues like electrode
life time, collector life time and dose control will be presented.
The paper describes recent progress on the development of an EUV source based on a hollow cathode triggered gas discharge (HCT). The principle of operation has been described in previous publications. When operated with Xe, a repetition frequency up to 4 kHz, conversion efficiency of 0.55% inband radiation in 2π and a pinch size below 3mm in length was demonstrated. Today's requirements on a commercial EUV source for volume production of wafers still exceed the current performance by large factors both in terms of output power and life time. This paper will discuss the roadmap to high power and will also show elements of the way to extended life time. Particular focus will be put onto the physical limits of Xe as radiator and the advantages of using Sn instead. It will be demonstrated that the spectral efficiency of Sn is a factor of 3 higher than Xe.
The paper describes the physical properties and recent technical advances of the hollow cathode triggered pinch device (HCT) for the generation of EUV radiation. In previous publications we have demonstrated continuous operation of the untriggered device at 1 kHz in pure Xe. The newer generations operate with a triggering facility which allows a wider parameter space under which stable operation is possible. Repetition frequencies of up to 4 kHz could be demonstrated. Many of the experiments are performed in repetitive bursts of variable lengths and spacing. This allows also to demonstrate that there is only little transient behavior upon switching on and off the source. Conversion efficiencies into the 2 percent frequency band around 13.5 nm are about 0.4 percent in 2p, comparable to the values reported from other groups. Another important parameter is the size of the light emitting region. Here we have studied the influence of electrode geometry and flow properties on the size, to find a best match to the requirements of the collection optics. A major problem for the design of a complete wafer illumination system is the out-of-band portion of the radiation. Especially the DUV fraction of the source spectrum is a concern because it is also reflected to some extend by the Mo-Si multilayer mirrors. We show that the source has a low overall non-EUV part of the emission. In particular, it is demonstrated that there is very little DUV coming out of the usable source volume, well below the specified level.