ald of scandium oxide from n,n’-diisopropylacetamidinato...
TRANSCRIPT
ALD of Scandium Oxide fromTris(N,N’-diisopropylacetamidinato)Scandium and Water
Philippe P. de Rouffignac, Roy G. Gordon Dept. of Chemistry and Chemical Biology, Harvard University, Cambridge, MA [email protected] (617) 495-4017
Scandium oxide is considered to be a high-k dielectric with good leakage properties. In combination with rare earth elements like dysprosium, gadolinium, and lanthanum, scandium produces ternary metal scandates that exhibit promising characteristics. These oxides have dielectric constants of ~22, have large bandgaps and high conduction band offsets with respect to silicon, remain amorphous to high temperatures, and are thermodynamically stable. Using ALD to deposit films for advanced MOSFET and DRAM applications is becoming more prevalent, and as such new ALD precursors and deposition methods are needed to have access to many different materials like the rare-earth scandates. In the first step towards synthesizing scandates it is necessary to have a fully developed scandium oxide ALD process.
Scandium oxide thin films were deposited using ALD from a new scandium precursor Sc(iPr2amd)3 and water. The precursor has sufficiently high volatility (0.04 torr at 100°C) and reacts with water to produce Sc2O3 with a minimal amount of carbon or nitrogen incorporation in the thin films. The growth rate of the film saturates at 0.7 Å/cycle and the ALD temperature window extends from 225°C to 300°C. The thickness is linear with the number of cycles and has an inhibition of 8-10 cycles on HF last silicon. The composition of the films was determined by Rutherford backscattering (RBS), and the crystallinity was determined by low-angle x-ray diffraction (XRD). The films were amorphous as-deposited, but were polycrystalline upon annealing at 600°C. Other characterization methods used include atomic force microscopy, spectroscopic ellipsometry, and cross-sectional high resolution transmission electron microscopy. Electrical measurements were made using either sputtered Pt contacts or in-situ ALD WN to form MIS and MIM capacitor structures. Capacitance-voltage and current-voltage curves were measured for films with various thicknesses. The dielectric constant was determined to be 13 with a leakage current density of less than 1 x 10-8 A/cm2 for a film with an EOT of 2.0nm.
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of S
cand
ium
Oxi
de fr
om
tris(
NN
’-diis
opro
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mid
inat
o)sc
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,Ndi
isop
ropy
lace
tam
idin
ato)
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hem
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and
Che
mic
al B
iolo
gy
Kev
in K
imR
oy G
ordo
n
App
licat
ions
and
Cha
ract
eris
tics
of S
c 2O
3
Sdi
Oid
Thi
Fil
Sca
ndiu
m O
xide
Thi
n Fi
lms:
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ycry
stal
line
abov
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0ºC
•Sta
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in d
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with
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ativ
ely
high
diel
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cco
nsta
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17•R
elat
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use
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rare
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etal
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ides
suc
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DyS
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and
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orG
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nG
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Har
vard
Uni
vers
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tmen
t of C
hem
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and
Che
mic
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Exc
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Har
vard
Uni
vers
ityD
epar
tmen
t of C
hem
istry
and
Che
mic
al B
iolo
gy
Ele
ctric
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rope
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Har
vard
Uni
vers
ityD
epar
tmen
t of C
hem
istry
and
Che
mic
al B
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-Dep
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= 16
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nm
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eale
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= 18
.7 ±
0.5
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±08
nm234 EOT (nm
IL
0.6
9 ±
.08
nm
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neal
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+ 0.
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= 0.
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Thic
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cons
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terfa
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laye
r.
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arva
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Dep
artm
ent o
f Che
mis
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ical
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lect
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ant (
from
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terfa
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de th
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rann
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cO
for a
nnea
led
Sc 2
O3
110
0.010.
1•L
eaka
ge is
low
er
than
equ
ival
ent S
iO2
film
s
1E5
1E-4
1E-3
(A/cm2)
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as
low
as
man
y ot
her h
igh-
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1E-7
1E-6
1E-5
J
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2.5
3.0
3.5
1E-8
EOT
(nm
)
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2
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arva
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Dep
artm
ent o
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Bio
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(nm
)
Sum
mar
yP
ure,
sel
f-lim
ited
Sc 2
O3.
1th
in fi
lms
wer
e gr
own
from
a n
ew p
recu
rsor
S
c(i P
r 2-M
e-am
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Ele
ctric
alpr
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ties
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lE
lect
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pro
perti
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re a
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ut n
ot id
eal.
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gro
wth
rate
.
Larg
e A
LD te
mpe
ratu
re w
indo
w <
275º
-350
º with
no
deco
mpo
sitio
n.
Ni
hibi
iH
Fl
ilif
No
inhi
bitio
n on
HF-
last
sili
con
surfa
ces.
Use
of A
LD S
c 2O
3to
dep
osit
mor
e co
mpl
ex te
rnar
y ox
ides
and
for
ilt
tili
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spec
ialty
coa
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app
licat
ions
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asib
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ith th
is ty
pe o
f pr
ecur
sor.
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arva
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Dep
artm
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f Che
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ical
Bio
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Dep
artm
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2.RE
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Region 2 Region 2
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x 10
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16
Nam
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Area
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Region 2 Region 2
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[vb1
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22244
540
538
536
534
532
530
528
526
524
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Bin
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6
540
538
536
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530
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Bin
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