S1-1

EUV Light Source Development for Next Generation Lithography
リソグラフィ用 EUV 光源開発
Koichi Toyoda
豊田浩一
Extreme Ultraviolet Lithography System Development Association
技術研究組合極端紫外線露光システム技術開発機構 （EUVA）

Abstract The main technological challenge of future extreme ultraviolet (EUV) light source is the required average power of 115W
at the intermediate focus. High repetition rate plasma sources both discharge produced plasma and laser produced plasma are very
promising to face this challenge. Source is the most essential part of future Extreme Ultraviolet Lithography apparatus. This paper
describes the present status and critical issues of high power EUV light source development. There have been put a lot of effort toboth LPP and DPP EUV light sources. In order to obtain an innovative technology for EUV source, it should be noted the important
collaboration of EUVA project with Leading project. This collaboration will benefit the understanding the underlying physicalprocesses and should lead to the high volume manufacturing (HVM) goal.

1. Introductionthat with a Sn GDPP it would be possible to get the required

Extreme ultraviolet lithography (EUVL) is the main candidate

photons at IF. But we have not solved the debris problem yet

for the next generation lithography to be introduced at theand this can be a showstopper.

45nm node. The EUV light source power is very highdemanding output power of 115W and the energy stability of0.3%.

This paper describes the present status and critical

3. ＥＵＶ Power at Source and Intermediate Focus (IF)At EUVL symposium at Miyazaki, power ofSn-GDPP

issues of high power EUV light source development. In orderwere reported to be 257 W / 50 W at source / IF respectively

to obtain an innovative technology for EUV source, it shouldfrom Philips Extreme, 700 W / 60 W from Cymer and 400W /be noted the important collaboration of EUVA project with50-75 W from Xtreme technologies.

Leading Project of MEXT （Ministry of Education, Culture,Xe-LPP were 9.1W / 4 W were from EUVA and 7 W / 2.3 W

Sports, Science and Technology）.

from Xtreme technologies and 7 W / 3 W from PowerLase.

2. EUV Light Sources

４. Target Materials

Whereas the power ofIn 1988, a synchrotron radiation (SR) was used as thePhilips estimated in Xe case fast ion generation and electrodelithography light source in a pioneer work o ｆ the EUV

erosion are five times as large as those of Sn. In addition

lithography

conversion efficiency and collection efficiency of Sn are larger

carriedoutinJapan(1).

FortheHVM

semiconductor industry application, very high demanding

than those of Xe.

output power of 115W and the energy stability of 0.3% areestimated that Xe is limited to about 15W.

γ-toolrequired. Two kinds of EUV sources of LPP and DPP havespecifications are only achievable with Sn source!

Sn is thebeen studied to fulfill these requirements. Comparing thesemost promising candidate as fuel (target) material for thesources, LPP source has the advantages, such as a large solid

generation of light at 13.5nm in sources in next step EUV

angle of about 5sr to be realized at the collector mirror, thelithography.

lower

extendedplasma(GPP) and laser produced plasma (LPP) sources.

component/collector mirrors lifetime and the high repetition

Compared with Xe, Sn has the advantages of less out-of bandrate operation for improved dose accuracy.

emission yielding in much higher conversion efficiency into thedebris

production

resultinginIt has been shown

Therefore as is shown in Table 1, it was

Xe is presently used in most gas discharge

13.5nm emission（2）. However, debris problem is not solved

6. Ion Damage Analysis on EUV Collector Mirrors

yet.

Collector mirror lifetime evaluation and damage prevention areimportant technical challenges for the EUV light source
development. Related future collector lifetime considerations,

Table 1 Limits of power scaling of DPP (Philips)(3)MaterialXeSn

fast ions from liquid jet xenon plasma measurement were madeconversion efficiency (% of 2Pi)

0.5

2

for the first time at EUVA.

pinch size (mm)2<1measurement combined with an electrostatic energy analyzer

collector opening (sr)1.83(ESA) was used. In Fig.1, typical ESA signals are shown.

collector + mitigation efficiency (%)

50

40

Though up to Xe5+ ions are observed, Xe2+ is the maincollection efficiency (% of 2 Pi)

20

45

observed charge state.(4)limit of power input (kW)3030inband power limit 2nd focus (W)15108

A time-of-flight (TOF)

7. Exposure Tool ApplicationsIn 2002, an early prototype of the Philips hollow cathodedischarge plasma source was installed in an experimental setup

0

Xe 5+
-0.1

at the ASML EUV laboratory in Veldhoven.

Xe 1+

Xe 4+
Xe 3+

roughly 0.2 W in-band EUV at intermediate focus of the source

Ekin / Z = 1 keV

and condenser.(5).First prototype GDPP sources of XTREME

Xe 2+

technologies of the type XTS-35 with 35W power in 2 pai sr-0.2
MCP signal (arb. units)

The source emits

Xe 1+

2 keV

have been integrated into micro-exposure tools (MET) from-0.3

Exitech, UK. Experience of integration as well as data about
3 keV

component and optics lifetime will be presented near future (6).

-0.4

References

Xe 1+4 keV(1) H. Kinoshita et al:”SoftX-ray reduction lithography using

-0.5

Xe 1+

multiplayer mirrors”, J. Vac. Sci. Technol., B7 (Nov/Dec

5 keV
-0.6
6 keV

1989)1648-1651.

Xe 1+

Xe 1+

(2) J.Ringling et al:”Development Status of high power Tin gas-0.70510152025time (µs)

Fig. 1 Typical ESA signal with an 8-ns, 100-mJ laser5. Collaboration with MEXT Leading Project
A five-year long project for LPP EUV Light source
development has been started as a Leading Project promotedby MEXT. The project aims at understanding physics of EUV
for practical use in collaboration with METI project (EUVA).
The project includes high performance laser development,
plasma experiments, theory and simulation and target
fabrication and providing database and guideline.

discharge Produced Plasma Sources for Next Generation EUV
Lithography”, 3rd Int’l EUVL Symp.（2004）.
(3) J.Pankert:"Philips EUV Lamp: Status and Roadmap”, EUV
Source Workshop (Antwerp) (2003).
(4) H.Komori etal:"Ion damage analysis on ＥＵＶ collectormirrors", Proc. SPIE Vol. 5374 Pt.2(2004) 839.
(5) H.Meiling et al:”The EUV Program at ASML”,Proc. SPIE
Vol.5037 Pt.1 (2003)24-35.
(6) U. Stamm et al: ”EUV source development at XTREME
technologies”, 3rd Int’l EUVL Symp.,So02 （2004）.