PROCEEDINGS OF SPIE SPIEDigitalLibrary.org/conference-proceedings-of-spie Novel EUV mask absorber evaluation in support of next-generation EUV imaging Vicky Philipsen, Kim Vu Luong, Karl Opsomer, Christophe Detavernier, Eric Hendrickx, et al. Vicky Philipsen, Kim Vu Luong, Karl Opsomer, Christophe Detavernier, Eric Hendrickx, Andreas Erdmann, Peter Evanschitzky, Robbert W. E. van de Kruijs, Zahra Heidarnia-Fathabad, Frank Scholze, Christian Laubis, "Novel EUV mask absorber evaluation in support of next-generation EUV imaging," Proc. SPIE 10810, Photomask Technology 2018, 108100C (10 October 2018); doi: 10.1117/12.2501799 Event: SPIE Photomask Technology + Extreme Ultraviolet Lithography, 2018, Monterey, California, United States Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 01 Nov 2019 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use
Novel EUV mask absorber evaluationin support of next-generation EUVimaging
Vicky Philipsen, Kim Vu Luong, Karl Opsomer, ChristopheDetavernier, Eric Hendrickx, et al.
Vicky Philipsen, Kim Vu Luong, Karl Opsomer, Christophe Detavernier, EricHendrickx, Andreas Erdmann, Peter Evanschitzky, Robbert W. E. van deKruijs, Zahra Heidarnia-Fathabad, Frank Scholze, Christian Laubis, "NovelEUV mask absorber evaluation in support of next-generation EUV imaging,"Proc. SPIE 10810, Photomask Technology 2018, 108100C (10 October2018); doi: 10.1117/12.2501799
Event: SPIE Photomask Technology + Extreme Ultraviolet Lithography, 2018,Monterey, California, United States
Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 01 Nov 2019 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use
Novel EUV mask absorber evaluation in support of next-generation EUV imaging
Vicky Philipsen1,*, Kim Vu Luong1,2, Karl Opsomer1, Christophe Detavernier3, Eric Hendrickx1,
Andreas Erdmann4, Peter Evanschitzky4, Robbert W.E. van de Kruijs5, Zahra Heidarnia-Fathabad5, Frank Scholze6, Christian Laubis6
1 imec, Kapeldreef 75, B-3001 Leuven, Belgium
2 KU Leuven, Department of Materials Engineering, Belgium 3 University of Ghent, Cocoon, Department of Solid State Sciences, Belgium
4 Fraunhofer IISB, Schottkystr. 10, 91058 Erlangen, Germany 5 University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
In next-generation EUV imaging for foundry N5 dimensions and beyond, inherent pitch- and orientation-dependent effects on wafer level will consume a significant part of the lithography budget using the current Ta-based mask. Mask absorber optimization can mitigate these so-called mask 3D effects. Thin metal absorbers like Ni and Co have been experimentally investigated due to their high EUV absorption, but they pose challenges on the current technology of subtractive mask patterning [1]. A simulation study of attenuated EUV phase shift masks has identified through multi-objective optimization superior imaging solutions for specific use cases and illumination conditions [2].
Evaluating novel EUV mask absorbers evolves on two levels, demonstrating (1) improvements from lithographic perspective and (2) compatibility with the full mask supply chain including material deposition, absorber patterning, scanner environment compatibility and mask lifetime. On the lithographic level, we have identified regions based on the material optical properties and their gain in imaging performance compared to the reference Ta-based absorber. Within each improvement region we engineered mask absorber materials to achieve both the required imaging capabilities, as well as the technical requirements for an EUV mask absorber. We discuss the material development of Te-based alloys and Ag-based layered structures, because of their high EUV extinction. For the attenuated phase shift materials, we start from a Ru-base material, due to its low refractive index, and construct Ru-alloys. On the experimental level, we examined our novel mask absorber materials against an initial mask absorber requirement list using an experimental test flow. Candidate materials are evaluated on film morphology and stability through thermal, hydrogen, EUV loading, and chemical cleaning, for their EUV optical constants by EUV reflectometry, as well as preliminary for selective dry etch.
The careful mask absorber evaluation, combining imaging simulations and experimental material tests, allowed us to narrow down to promising combinations for novel EUV mask absorbers. Keywords: EUV mask absorber, mask 3D effects, absorber characterization, rigorous mask 3D lithography simulation
1. INTRODUCTION Over the recent years the knowledge has grown and spread on mask-induced imaging effects, experimentally observed in EUV lithography for N5 dimensions and beyond, with the current EUV mask [1-9]. More precisely, the current Ta-based absorber is at its limit for imaging extendibility. Thinning down below 50nm Ta-based absorber thickness will reduce the amount of absorbed light, reduce the NILS and increase best focus variation through pitch [10,11]. Although the current Ta-based mask has proven benefits from mask technology point, the imaging performance towards next technology nodes can benefit from mask optimization. The industry needs to reconsider the EUV mask concept as a mitigation of mask-induced imaging effects (by balancing the diffraction for all features and pitches simultaneously).
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Different conto changing tthe etched mudifficult. Todtechnology ninitiate a masimulations a
In Section 2 wreference Ta-and we demoSection 4 sumselection.
In this Sectioresults onto timprovementdifferent mas
2.1 Material
When we lootheir EUV opresponse in ri
Figure 1 EUEUV absorpt
From TaBN absorber thickrefraction indand in the oth
2.2 Imaging
We studied thequivalent N5our calibratedillumination compared to c
ncepts have bethe multilayerultilayer mirro
day, the focus nodes. This beask absorber and experimen
we motivate t-based mask fonstrate our exmmarizes the
2. on we highligthe material opt. In the seconk absorber n&
l space vs. re
ok for alternatiptical propertigorous lithog
UV n&k space ion, phase ma
as starting pokness reductiodex of the mather direction to
g performanc
he imaging pe5 dedicated bud and experimsettings at NAcandidate abs
een introducedr mirror materor mask [14,1of the industrecame clear ichange [16].
ntal absorber m
the choice of for typical N5 xperimental e
e main findin
IMAGINGght the benefitptical propert
nd sub-Section&k. This leads
ference TaBN
ive mask absoties, n&k, as graphic simula
with TaBN aatching to vacu
oint we can ion and conseqterial allows io increase the
e of n&k regi
erformance ofuilding block
mentally validaA0.33 and seorber material
d over the recrials to Ru/Si15]. Realizingry is on novelin the 2018 iIn this pape
material tests,
alternative mabuilding bloc
evaluation megs of this pap
G GAIN IN t of a mask aty space. In thn we dive dee us to the iden
N mask absor
orber materialthese are - to
ators. Figure 1
as the diamonduum and inten
improve to mquently smallein one directioe contrast, whe
ions vs. refer
f various masks using the rigated mask Moelected featurels at 32nm thi
ent years, from[13] over em these mask cl mask absorbimec organizeer we report of potential n
ask absorberscks at NA0.33ethodology floper and point
EUV MASKabsorber chanhe first sub-Seeper into the sntification of m
rber
s from an imaogether with t plots the EUV
d and three pontional phase s
materials with er shadowing eon to reduce ten enhancing
rence TaBN m
k absorbers ingorous mask 3o/Si multilayee types and rickness with n
m tuning the Mmbedding the aconcepts in prber as the mosed forums gatthe careful e
novel EUV ma
s based on the. Section 3 de
ow using our ts to a path f
K ABSORBge by projectection we idenimulation resumaterials with
aging perspectthe absorber tV n&k space w
ossible n&k reshifting.
higher EUV effect due to ithe phase defothe phase shif
mask absorbe
n the three reg3D simulator er mirror modranges. The 6n&k combinati
Mo/Si multilaabsorber in throduction wort realistic impthering the E
evaluation, coask absorbers.
eir imaging peetails out the mengineered, nforward in th
BER CHANGting a wide rantify n&k regiults of foundr
h predicted im
tive, we reprethickness - acwith the meas
egions for nov
extinction coits increased Eormation, wheft character of
erformance comask absorbernovel EUV mahe absorber m
GE ange of imagiions of interery N5 building
maging gain.
sent the materccountable fosured values fo
vel absorber m
oefficient, whiEUV absorptioen n is matchef the material.
ated in FigureV (Synopsys) in [19]. Tablece TaBN masented in Table
eriodicity [12]mirror [3] and
ment turned outowards futureupply chain toorous imaging
ompared to ther requirementsask absorbers
material down
ing simulationst for imagingg blocks using
rial options byor the imagingfor TaBN [17]
materials: high
ich allows foron. Tuning theed to vacuum
1 for foundry[18] includinge 1 depicts thesk absorber ise 1 (c).
, d
ut e o g
e s s. -
n g g
y g .
h
r e
m,
y g e s
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30 40 50
30 40 50i 60 70
Pitch [nm]
-I
60 70Pitch [nm]
32
28rr094
V refractive ind
1
N
50 60
Pitch [i
I
+Trench --o-CH - Que
70 80 9
nm]
tFrl.lcil
.....40
F Trench - DipY
r CH - Quasar4
- --ttattataatt
80 90
-s- s
F Trench - DipY
.-CH - Quasar4
SO 90
tTrench
"WiliesimbM
70 80 9
nm]
10
5
0
-5
10
-15
-2030 40
Table 1 (a) Irigorous imag
Figure 2 MaNA0.33 as inerror; Left-bo
Illumination sging simulatio
(a)
ask 3D sensitndicated by thottom: NILS; R
settings at 0.3ons.
tive imaging he legend in eRight-bottom
33NA, (b) fea
(b)
metrics usingeach plot. Lef: Two bar CD
ature types th
g the 60nm Tft-top: best fo
D asymmetry th
hrough pitch,
TaBN referencocus variation hrough focus.
and (c) mask
ce mask for fthrough pitch
k absorber n&
(c)
features and ih; Right-top:
&k used in the
llumination aTelecentricity
e
at y
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Qs4!
0.1
d 0.09
w 0.080.07
ac 0.06
-° 0.050.04
ti 0.03D 0.023 0.01
0
0.86 OS
- CH - Best Foc
8 0.9 0.92
n, EUV refrac
8 0.9 0.92
n, EUV ref rac
:H - max. telece
:us range
TaB
0.94 0.96 0.9e
Live Index
inm NILS
0.94 0.96 0.99
Give index
ocus range
DofaBN
4 0.96 0.98
. Index
asymmetry
4 0.96 0.98
a Index
Qs45 -C
0.1F., 0.09
.t 0.08
3 0.07c 0.06-O 0.05Vf0.04agi 0.03
j 0.02Lu 0.01
0
0.86 0.81
5 - CH - pitch40
P c
8 0.9 0.92 i
n, EUV refrac
0.1
v 0.09'9 0.08á 0.078 0.06
0.05VS 0.04ti 0.03
D 0.02
x 0.010
0.86 OS
Qs4!
ntricity error
asTaBN
0.94 0.96 0.9E
five Index
Trench - Best Fr
MEN'Mr--n--
0 9 0.92 0.9,
n, EUV refractive
4 0.96 0.98
, index
t2nm NILS
Jras
ecentr. error
jla BN
4 0.96 0.98
index
rench - max. tel
oa
1
0.9 0.92 0.94
n, EUV refractive
>itch32nm 2Bar
MMMr1MLaMMMMgaMMMMM0 9 0.92 0.9.
n, EUV refractive
0.10.090.080.070.060.050.040.030.020.01
0
0.86 0.88
Quasar45-'
Trench pitch:
0 9 0.92 0.94
n, EUV refractive
DipoleY90 - p
0.1
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
0.86 0.88
DipoleY90 -Tr
0.1
0.090.080.070.060.050.040.030.020.01
0
0.86 0.88
0.10.090.080.070.060.050.040.030.020.01
0
0.86 0.88
Quasar45 -
Figure 3 n&60nm TaBN a
&k plots with tabsorber mask
the change in k. The imagin
the imaging ng metric, feat
metric of the
ture type and i32nm n&k a
illumination aabsorber maskat NA0.33 as in
k compared tondicated abov
o the referenceve the plots.
e
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The imaging settings are thCD asymmetrbest focus thasymmetry thcompared to telecentricity metrics by chcircle symbocircle refers tis the value on&k space wiA region of inbe attributed vacuum regiovacuum causNILS. This fiobjective optbased mask. TaBN due ttelecentricity phase matchidetermines thgeneral impro
Figure 4 n&TaBN.
Within each oreside in the RuRe is positdetail in the n
Mask absorbeneeds to fulfimanufacturinmore extensivsub-Sections.
metrics sensithe best focus ry through foc
hrough pitch ahrough focusthe referenceerror and tw
hanging the abls is relative to a deterioratof the largest ith expected imncreased NILto a destruct
on of the masses a more profinding supporimization led A region of
to stronger Eerrors and tw
ing of the abhe optimal n&ovement.
&k plot indica
of these regioregion of higtioned in the
next Section.
er change is afil a diversity ng, mask fabricve list can be .
tive to mask 3variation, thecus. Figure 2 amounts to 40s at the smale mask implie
wo bar CD asybsorber materito the referen
tion of the merelative impromaging impro
LS can be obsetive interferensk. Moreover,onounced warts earlier worto the improvsmaller best
EUV absorptiwo bar CD asybsorber materi&k region, al
ating three reg
ons we enginegh extinction attenuated ph
3. EUVa complex anof requiremencation and qufound in [20]
3D effects evae NILS, the teshows the im
0nm, while thllest pitch ofes that the Nymmetry throial with respecnce TaBN. Thetric comparedovement. Comovement comperved for matence of (incre, the decrease
aveguide effecrk [2] where aved imaging ofocus range ton over a smymmetry throuial to the surlthough increa
gions with ex
ered and charcoefficient. N
hase shifting re
V MASK Ad difficult pronts to guarantalification, an]. Table 2 list
aluated throughelecentricity er
maging behaviohe maximum f 32nm exten
NILS needs toough focus nect to the referehe green colod to the behavmbining all thpared to the reerials with a rasingly) phased refraction ict for the ligha co-optimizatof an attenuatthrough pitch maller absorbugh focus canrrounding vacasing the ext
xpected impro
racterized poteNi3Al and TaTegion. Figure
BSORBER ocess in the mtee success th
nd mask use pts the requirem
h pitch for therror (i.e., patteor using the 60telecentricity
nts to 48mrado increase, wheed to decreasence is plottedor implies anvior of the refhe imaging reeference maskrefraction indese shifted lighindex contras
ht in the vacution of mask ed phase shiftcan be found
ber thickness n be found at acuum. The weinction coeffi
oved imaging
ential EUV mTe2 exhibit a
4 illustrates t
REQUIREMmask making hroughout theose various re
ments we inve
e three featureern shift throu0nm TaBN reerror reaches
d. Improving hile the best fse. The relativd in n&k plotsimprovement
ference mask. sults allows u
k. The resultinex n smaller tht in the absot between the
uum spaces anmaterial and
fting mask comd at higher ex
minimizing a refraction ineight given toicient k comp
performance
mask absorber refraction indthe n&k of th
MENTS technology, s
e complete EUequirements oestigated in m
e types and twugh focus), aneference masks -13mrad and
the imagingfocus range, ve change of in Figure 3. T
t of the metricAlso indicate
us to identify ng plot is showthan that of Taorber area ane absorber mand a further inillumination t
mpared to the xtinction coefthe phase im
ndex n close to each optimpared to TaBN
compared to
materials. Agdex approachihe materials st
since the candUV mask life on the candidamore details in
wo illuminationnd the two bar
k. The range od two bar CD
g performancethe maximumeach of these
The size of thec, while a reded in each ploregions in the
wn in Figure 4aBN. This can
nd light in theaterial and thencrease of thethrough multireference Ta
fficient k thanmpact. Lowerto 1 due to theization metricN points to a
the reference
g, Ni and PtTeing one, whiletudied in more
didate materiacycle. Blank
ate absorber. Athe following
n r f
D e
m e e d
ot e
4. n e e e --n r e c a
e
e e e
al k A g
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Table 2 Inve
Character
Film morp
Optical co
Mask dur
Mask patt
3.1 Film mo
Single metal formation [1alloying. Ag-based layextinction cocrystallizationadhesive layestructure, witdiffractometrsurface rougroughness, Anm, and are lsize Ag to naratio of Ag toAg/Cu multil
Figure 5 (a) crystallinity.
Alloying the film poly-cryimprovement50% Te due shifting materTo increase thmicroscope (confirmed by
estigated mask
rization
phology
onstants
rability
terning
orphology
films deposi,20]. In the a
yered structureoefficients at n and islandiner, such as Teth individual
ry (XRD) (seeghness with pAg/Cu multilayless prone to oanometer size o Cu can be flayers provide
e of the largesm of full layerd by using anmulti-layered
m with X-rayg, coupled to aystallinity andghness of 0.25om nanometergure 5(b). Theer, and as suchmaterial.
how very low
h to reduce theand imaging
s with at leasenuated phase
ission electrontTe, which isC.
-r
st r n d y a d 5 r e h
w
e g st e
n s
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We investigaquasi-amorph350°C, whichthe full absorAs-depositedThis crystallielements, suc[21-22].
Figure 6 Top
3.2 EUV opt
The EUV opinduced imagnm) are condII storage rinin the wavelethe engineererigorous litho
Figure 7 EUV(b) Ni3Al film
ated the feasibhous morpholh will be discurber layer. d Ru-alloys exine phase remch as N and P
p: TEM image
tical properti
ptical propertiging effects. Educted in the lug [17]. The ob
ength range, aed alloys is eographic simul
V reflectance m and (c) Ru3R
bility of Ta-telogy of as-depussed in more
xhibit a high dmains the sam, might reduce
(a)e of as-deposit
ies
ies of the maEUV reflectanubrication freebtained surfac
as well as the essential to colation (cf. Sec
(a)
(in log10 scalRe film on Si
elluride. The posited Ta-Te
e detail in Sec
degree of polyme towards 50e the crystalli
ted (a) PtTe, (
ask absorber nce measureme EUV reflectce plot, presenthickness of torrectly prediction 2.2).
le) as functionsubstrate.
IS-XRD meae alloy. A chtion 3.3.1. Fu
y-crystallinity00°C, based nity, by break
(b)(b) TaTe2, and
material and ments throughtometer of PTnted for three the individualict the imagin
(b)n of waveleng
asurements anhange in backurthermore, the
y, visible in thon the IS-XR
king the Ru cr
d (c) Ru3Re fil
its thicknessh incidence anB at the soft Xalloys in Figu
l layers in the ng impact of
gth and inciden
nd TEM imagkground intense presence of
he TEM imagRD measuremrystal lattice th
lm. Bottom: c
s determine itngle and waveX-ray radiomeure 7, is fittedfilm. The accthese potenti
nce angle of a
ge in Figure 6sity can be doxygen is det
ge of Ru3Re iments. Doping
hrough their s
(c) orresponding
ts ability to melength (frometry beamline d to provide thcurate n&k mial mask abso
(c) a ~30nm thick
6(b) prove thedetected abovetected through
in Figure 6(c)g with smallersize difference
IS-XRD plot.
mitigate maskm 10 nm to 16
at the BESSYhe n&k values
measurement oorber films in
k (a) PtTe film
e e h
). r e
.
k 6 Y s f n
m,
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3.3 Absorbe
During normoperation. Aparticles. Weenvironment films allows u
3.3.1 The
The temperat
We quantifiedKissinger anapresented in beyond the ty
Under thermaat different ttellurides a sistabilize the T
Figure 8 (a) Lfor (b) TaTe2
From the theduring typica
3.3.2 Wet
The candidatemask cleaninin a beaker wthickness loseach surface Ni3Al in bothrespectively.
Next, the PtT(ICP-MS) to in both aqueo
er durability
mal mask usagdditionally, th
e have a testinand in soluti
us to make a p
rmal stability
ture of the ma
d the lifetime alysis [23]. FoFigure 8(a). A
ypical mask lif
al loading the temperatures, ignificant Te Te better than
(a) Lifetime untiland (c) PtTe
ermal stabilityal mask therma
t conditions
e mask absorbng: (1) de-ioniwith the solutis, rougheningelement. Alu
h tested aqueo
Te film is chardetermine the
ous solutions a
ge in the fabhe mask nee
ng methodologons of the caproper absorbe
y
sk in the scan
of the candidor the PtTe filAt a constantfetime in a fab
alloy might sas shown in loss is detectethe Ta-telluri
l recrystallizatfilm.
y tests on the al conditions (
ber must stay zed water (DIions for ~24 hg or density chuminum metalous solutions.
racterized by e rate of mateafter three diff
b the mask abeds to withstagy in place toandidate mateer selection.
ner or in stora
date absorber flm we extrapot temperature b.
suffer from maFigure 8 (b-
ed at 500°C. Aide, where som
tion of PtTe f
engineered a(i.e., below 15
stable duringIW) at pH 5.7hours. After vhange. The stl reacts underTaTe2 and Pt
the highly senerial loss in eaferent time du
bsorber mustand several w assess the thrial films. Th
age will vary,
films by calcuolated the lifet
of 80°C the
aterial loss. F-c). Te becomAt a temperat
me Te loss is n
(b)film vs. tempe
absorber films50°C).
typical mask7, (2) 1% NH4visual inspectitability of the r both acidic atTe are more s
nsitive techniach aqueous surations.
t stay unalterwet conditionermal stability
his stability qu
but it may no
ulating the recrtime until recrPtTe film wi
or the TaTe2 ames volatile jture of 250°Cnoticed.
erature. Te los
s we learned
k cleaning. We4OH at pH 11ion the films aalloys in wet
and alkalic costable in the s
que of inductolution. Figur
red in scannens, when cleay as well as thuantification
t impact the m
rystallization rystallization ll recrystalliz
and PtTe filmust above 40
C the noble me
ss measured a
that PtTe and
e selected two.4. First the sare measured t conditions donditions, whsolutions due t
tively coupledre 9(a) shows
er conditions aned for remhe stability unof the engine
material morph
activation eneat different tee after 450 y
ms the Te loss 00°C and theretal telluride P
(c) at different the
d TaTe2 will
o solutions curamples are fuby XRR to d
depends on thhich impacts thto the stability
d plasma massthe measured
under normamoving surface
nder hydrogeneered absorber
hology.
ergy through aemperatures asears, which is
was measuredrefore in bothPtTe seems to
ermal loadings
stay unaltered
rrently used inully submerseddetermine filme reactivity ohe reaction oy of Ta and P
s spectrometryd Te dissolved
al e n r
a s s
d h o
s
d
n d
m f f
Pt
y d
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Figure 9 (a) D(b) Calculated
From the slopand less thanperform an im
3.3.3 Scan
In the scannethese operatioHowever, theTherefore, wehydrogen clebackscatterinintact after ~telluride PtTe
Figure 10 Re
The individuaconditions to is required totest in an irrcombined EUthe films afte
Dissolved Te d Te loss rate
pe through timn 1nm in 1% Nmaging sensiti
nner conditio
er the mask, anon conditionse absorber me conducted a
eaner [20]. Thg spectrometr
~24 hours H* e seems to bin
elative elemen
al H* test withpure H* envi effectively as
radiation chamUV power denr EUV+H2 ex
measured byper full day in
me we calculaNH4OH. The ivity study in
ons
nd thus the ms hydrogen ramaterial is noa first assessmhe elemental ry (RBS) and exposure, wh
nd the Te stron
ntal content af
h the novel abironment are tssess the impamber at the bnsity and H2 gxposure by X-r
(a)y ICP-MS in tn two differen
ate the Te dissquantificationa next stage.
mask absorber adicals (H*) cot allowed to
ment by exposicontent of ththe relative ch
hile the telluringer in the bul
fter more than
bsorber films ptoo aggressiveact of combineamline of Pgas pressure [ray photoelect
two different nt aqueous sol
solution after n of absorber
material, is excan be formed form volatiling our alloy fhe films beforhanges are ploides lose Te clk than the Ta
24 hours H*
provides a roue compared toed high EUV TB where the[24]. Our inititron spectrosc
aqueous solutlutions.
a full day of material loss
xposed to higd and these Hle contaminanfilms to a strore and after eotted in Figurcontent due toa-telluride.
exposure as d
ugh estimate oo the actual scpower and H2e PtTe films ial results in Fcopy (XPS).
(b) tions after thr
submersion tos after multipl
gh EUV powerH* can react wnts or to cha
ong H* environexposure was re 10. The Ni3o reaction to H
determined by
of possible intecanner conditi2 atmosphere.were exposed
Figure 11 are
ree different ti
o be less the 0le mask clean
r in H2 envirowith the absoange its filmnment in imecdetermined b
3Al and Ru3ReH*. Again, th
RBS.
eractions. Howions. A dedica We performed to variable obtained by
ime durations
0.4nm in DIWns allows us to
onment. Underorber material
m morphologyc’s EUV Techby Rutherforde films remainhe noble meta
wever, the tesated test setuped a feasibility
conditions ocharacterizing
s.
W o
r l. y. h d n al
st p y f g
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Figure 11 Noconditions.
Two groups ooxidized Te psurface to meThese initialenvironment,conditions an
3.4 Absorbe
To emphasisapproaches. Sbe considered
3.4.1 Sub
Mask absorbeetching procesputtering canwork [1] wecomponent ofand to demon
In a first etchmaterial film and the TaTe
(a)Figure 12 Cr(c) PtTe film
ormalized XPS
of results canpeaks at the Ptetallic Te, resu results indic but the samp
nd matching to
er patterning
s the importaSubtractive pad a disruptive
tractive patte
er patterning ess. By formin pattern thro
e experienced f this etch tec
nstrate volatile
hing test a 1µin an RIE too
2 film.
) ross-section SEon Si substrat
S spectra of T
n be observedtTe surface, wulting in equalcate the sensples need addo actual scann
ance of absoratterning is thmanner for th
erning
is typically acing volatile coough thin met
the challengchnique by usie formation w
µm thick pattol. The cross-s
EM images afte and with a
Te3d peaks fro
: the referencwhile a combinl Te-oxide andsitivity of thditional charaer conditions
rber patterninhe traditional whe mask makin
chieved with ompounds, thtal layers anisges of metal ping halogen-bith the elemen
terned resist fsection SEM i
(bfter chemical 1µm thick res
om the referen
e PtTe film anation of EUVd metallic Te pe materials t
acterization tois ongoing.
ng we assessway of patternng technology
reactive ion ehe etching is msotropically, bpatterning thr
based plasma ontal componen
film is used aimages in Fig
)etch in haloge
sist pattern on
nce and five P
and the PtTe fV and H2 gas speaks. to the combi quantify its
ed experimenning the mask
y.
etching (RIE),material selec
but it is not exrough RIE etonly, without nts of the abso
as mask for thgure 12 illustra
en-based plasmtop.
PtTe films exp
films only expseems to reduc
ined exposureimpact. Furth
ntally the feak absorber, wh
, which is a cctive. The phyxtremely matetching. Now a carrier gas
orber alloy.
he chemical eate the outcom
ma of ~30nm
posed to diffe
posed to EUVce the Te-oxid
e of EUV pher optimizati
asibility of twhile additive p
chemically assysical etchingerial selectivewe focus on to reduce the
etching of theme for the pur
(c) thick (a) Te, (
erent EUV+H
V show strongde on the PtTe
power and Hion of the tes
wo patterningpatterning can
sisted physicag by ion beame. From earlier
the chemicaphysical etch
e ~30nm thickre Te, the PtTe
(b) TaTe2, and
2
g e
2 st
g n
al m r
al h,
k e
d
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The pure Te removed in tmaterials aresidewalls andas we also ob
High-k metaldevelopment
3.4.2 Add
Because subtrdisruptive appSince our siman EUV masusing a dielec
We start withsidewall and sidewall defincontrollable wFigure 13 (bFurthermore, template is reshows a fullyadvantage of create amorphthe compatibi
Figure 13 Sicobalt ASD; (
In this paper wexperimental thickness witthese improvEUV absorpt
film is isotrothe chemical e patternable d from residuebserved for Ni
ls, like Ni anis needed to s
ditive pattern
ractive metal proach of met
mulation studysk is capped wctric template
h sacrificial paedge of the
nition. In a neway on the opb) the trenche
the Ru cappemoved to rey amorphous f the additive hous metal paility with mas
(a) mplified flow(c) Co pattern
we proposed nbehavior in E
th improved mement regionstion and ther
pically etchedetch process.in a subtract
es in the remoetch [1].
nd Pt, are disolve these pa
ning
patterning potal-on-metal ay converges towith Ru, whicthrough meta
atterning in a dfinal metal f
ext step the Apen Ru metal es in the temping layer is sult in the fincobalt patternpatterning tec
atterns on the sk size, e.g., in
w for metal-onn after templat
novel EUV mEUV lithograpmask induceds, we engineerefore will su
d in the plasm This is a strtive way. Ho
oved trenches,
fficult to etchatterning challe
ses challengesarea selective do high-k metalsch is a metal, al electroless d
dielectric layefeatures. The ASD is perfor
areas in betwmplate are filnot damaged
nal Co metal n, as crystallizchnique, whilRu cap of the
n terms of thic
n-metal ASDte removal.
4.mask absorbersphy conditionsd imaging effeered novel mauffer less fro
ma and is therrong indicatio
owever, the Pwhich is typi
h selectivelyenges.
s on selectivitdeposition (As as candidatewe can grow
deposition [26
er (e.g., SiO2).dielectric pa
rmed where thween the templled with cob
d by additive absorber pattzation is confle Co PVD ise multilayer mckness uniform
(b)D on 200nm p
CONCLUSs based on a cos. We identifieects comparedask absorbers.om best focus
refore likely eon that alloys Pt-telluride saical for metal
with known
ty and chemicSD) for mask
e mask absorbw in a control6]. The flow is
. The quality oatterning enabhe metal (i.e.,plate. In our ebalt without
patterning, cern. Charactefined by the d
poly-crystallmirror. Furthermity and defec
pitch equal lin
SION ombined asseed EUV n&kd to the curren The PtTe alls variations.
etchable by Rwith Te and
mple suffers etching with
chemistries.
cal volatility opatterning pu
ber materials, alable way me
s exemplified i
of the templatbles further C the mask ab
example cobalCo deposition
contrary to eterization of thdielectric temline. Additive r optimizationctivity.
nes/spaces. (a
ssment of theiregions for mnt Ta-based mloy and Ag-baNiAl and Ta
IE. The Ta-ted other chemi
from fences limited volati
Direct metal
f metal elemeurpose [25]. and the multiletal selectivelyin Figure 13.
te pattern will CD/pitch scalisorber materilt ASD is perfn on top of tching. In thehe Co ASD in
mplate. This ispatterning ha
n is required t
(c)a) Template p
ir imaging permask absorbersmask absorberased multilayeaTe alloys m
elluride is alsocally etchableon the resis
le byproducts
l etch process
ents, we took a
layer mirror oy on metal by
determine theing with goodal) grows in aformed and inthe template
e last step then this example an additionaas potential toto demonstrate
patterning; (b)
rformance ands around 32nmr. For each oer have a high
match at EUV
o e st s,
s
a
f y
e d a n e. e e
al o e
)
d m f h V
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wavelength their phase close to vacuum resulting in reduced telecentricity errors and two bar CD asymmetry through focus. The RuRe alloy is put forward as potential attenuated phase shifting material for EUV masks expected to increase NILS at reduced dose-to-size with the proper mask-illumination optimization.
We presented the experimental testing methodology geared to address several essential mask absorber requirements to allow for a material down-selection. Our testing flow assesses the durability of the film morphology under different thermal, EUV, hydrogen, and cleaning conditions, typical for mask environment. We found that the most interesting materials from lithographic perspective pose challenges on traditional mask etching technology. Adapting towards etchable materials creates a trade-off in material durability and subtractive patterning. Therefore, we introduced the concept of additive patterning for mask absorbers.
Our next goal is to find solutions – through collaborative efforts – for the absorber patterning challenges of the proposed novel mask absorber materials.
5. ACKNOWLEDGEMENTS
This project has received funding from the Electronic Component Systems for European Leadership Undertaking under grant agreement number 662338. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme and Netherlands, France, Belgium, Germany, Czech Republic, Austria, Hungary, Israel. The authors are grateful to Dr. I. Pollentier and Dr. J. Rip for their assistance in the durability testing. Dr. L. Souriau is acknowledged for his etch support and expertise. For metrology support we thank N. Vandenbroeck, P. Jaenen, Dr. T. Conard, Dr. I. Hoflijk, and Dr. J. Meersschaut (imec). Area selective deposition of Co was made possible thanks to K. Vandersmissen and Dr. BT Chan (imec). We appreciate the support of Dr. G. McIntyre, Dr. K. Ronse, Dr. S. Van Elshocht (imec), and Prof. Dr. M. Heyns (KU Leuven).
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