Recent advances in the semiconductor industry have created an exigency for processes that allow to deposit and etch material in conformal matter in three-dimensional devices. While conformal deposition is achieved using atomic layer deposition (ALD), conformal etching can be accomplished by thermal atomic layer etching (ALE) which, like ALD, proceeds via a binary sequence of self-limiting reactions. This study explores ALE of TiO2 and ZrO2 using WF6 as a fluorinating agent, and BCl3, TiCl4, or SOCl2 as a co-reactant. The effect of co-reactant chemistry was studied using atomic force microscopy, in situ ellipsometry, and in vacuo Auger electron spectroscopy measurements along with thermodynamic modeling. All three co-reactants exhibited saturation and etch rates increasing with temperature. At 170 °C, TiO2 can be etched using WF6 with BCl3, TiCl4, or SOCl2, and the etching proceeds at 0.24, 0.18, and 0.20 nm/cycle, respectively. At 325 °C, ZrO2 ALE can occur using these same reactants, proceeding at 0.96, 0.74, and 0.13 nm/cycle, respectively. A higher temperature is needed for ZrO2 ALE versus TiO2 because the ZrCl4 product is less volatile than the corresponding TiCl4. During ZrO2 and TiO2 etching using BCl3 or TiCl4, boron oxide or titanium oxide intermediate layers, respectively, were formed on the surface, and they were subsequently removed by WF6. In contrast, for ALE of TiO2 using SOCl2, a similar intermediate layer is not observed. This study broadens the understanding of co-etchants role during thermal ALE and expands the range of reactants that can be used for vapor etching of metal oxides.

1.
M.
Toofan
and
J.
Toofan
,
Developments in Surface Contamination and Cleaning
(
Elsevier
,
New York
,
2015
), pp.
185
212
.
2.
K.
Nojiri
,
Dry Etching Technology for Semiconductors
(
Springer International
, Tokyo,
2015
).
3.
J. A.
Dagata
,
J. Vac. Sci. Technol. B
5
,
1495
(
1987
).
4.
F. I.
Chang
,
R.
Yeh
,
G.
Lin
,
P. B.
Chu
,
E. G.
Hoffman
,
E. J.
Kruglick
,
K. S. J.
Pister
, and
M. H.
Hecht
,
Proc. SPIE
2641
,
117
(
1995
).
5.
H. F.
Winters
and
J. W.
Coburn
,
Appl. Phys. Lett.
34
,
70
(
1979
).
6.
V.
Passi
,
U.
Sodervall
,
B.
Nilsson
,
G.
Petersson
,
M.
Hagberg
,
C.
Krzeminski
,
E.
Dubois
,
B.
Du Bois
, and
J. P.
Raskin
,
Microelectron. Eng.
95
,
83
(
2012
).
7.
A.
Witvrouw
,
B.
Du Bois
,
P.
De Moor
,
A.
Verbist
,
C. A.
Van Hoof
,
H.
Bender
, and
C.
Baert
,
Proc. SPIE
4174
,
130
(
2000
).
8.
V.
Lindroos
,
M.
Tilli
,
A.
Lehto
, and
T.
Motooka
,
Handbook of Silicon Based MEMS Materials and Technologies
(
Elsevier
,
New York
,
2010
).
9.
P. C.
Lemaire
and
G. N.
Parsons
,
Chem. Mater.
29
,
6653
(
2017
).
10.
Y.
Lee
,
C.
Huffman
, and
S. M.
George
,
Chem. Mater.
28
,
7657
(
2016
).
11.
R.
Steger
and
R.
Masel
,
Thin Solid Films
342
,
221
(
1999
).
12.
C. T.
Carver
,
J. J.
Plombon
,
P. E.
Romero
,
S.
Suri
,
T. A.
Tronic
, and
R. B.
Turkot
,
ECS J. Solid State Sci. Technol.
4
,
N5005
(
2015
).
13.
K. J.
Kanarik
,
S.
Tan
, and
R. A.
Gottscho
,
J. Phys. Chem. Lett
9
,
4814
(
2018
).
14.
K. J.
Kanarik
,
T.
Lill
,
E. A.
Hudson
,
S.
Sriraman
,
S.
Tan
,
J.
Marks
,
V.
Vahedi
, and
R. A.
Gottscho
,
J. Vac. Sci. Technol. A
33
,
020802
(
2015
).
15.
C.
Fang
,
Y.
Cao
,
D.
Wu
, and
A.
Li
,
Prog. Nat. Sci.: Mater. Int.
28
,
667
(
2018
).
17.
Y.
Lee
and
S. M.
George
,
ACS Nano
9
,
2061
(
2015
).
18.
Y.
Lee
,
J. W.
Dumont
, and
S. M.
George
,
Chem. Mater.
28
,
2994
(
2016
).
19.
A.
Fischer
,
A.
Routzahn
,
Y.
Lee
,
T.
Lill
, and
S. M.
George
,
J. Vac. Sci. Technol. A
38
,
022603
(
2020
).
20.
Y.
Lee
,
J. W.
Dumont
, and
S. M.
George
,
Chem. Mater.
27
,
3648
(
2015
).
21.
S.
Imái
,
T.
Haga
,
O.
Matsuzaki
,
T.
Hattori
, and
M.
Matsumura
,
Jpn. J. Appl. Phys.
34
,
5049
(
1995
).
22.
A. I.
Abdulagatov
and
S. M.
George
,
Chem. Mater.
30
,
8465
(
2018
).
23.
J. W.
DuMont
,
A. E.
Marquardt
,
A. M.
Cano
, and
S. M.
George
,
ACS Appl. Mater. Interfaces
9
,
10296
(
2017
).
24.
R.
Rahman
,
E. C.
Mattson
,
J. P.
Klesko
,
A.
Dangerfield
,
S.
Rivillon-Amy
,
D. C.
Smith
,
D.
Hausmann
, and
Y. J.
Chabal
,
ACS Appl. Mater. Interfaces
10
,
31784
(
2018
).
25.
J. A.
Murdzek
and
S. M.
George
,
J. Vac. Sci. Technol. A
38
,
022608
(
2020
).
26.
Y.
Lee
and
S. M.
George
,
J. Vac. Sci. Technol. A
36
,
061504
(
2018
).
27.
Y.
Lee
,
J. W.
DuMont
, and
S. M.
George
,
ECS J. Solid State Sci. Technol.
4
,
N5013
(
2015
).
28.
D. R.
Zywotko
and
S. M.
George
,
Chem. Mater.
29
,
1183
(
2017
).
29.
A.
Mameli
,
M. A.
Verheijen
,
A. J. M.
Mackus
,
W. M. M.
Kessels
, and
F.
Roozeboom
,
ACS Appl. Mater. Interfaces
10
,
38588
(
2018
).
30.
E.
Mohimi
,
X. I.
Chu
,
B. B.
Trinh
,
S.
Babar
,
G. S.
Girolami
, and
J. R.
Abelson
,
ECS J. Solid State Sci. Technol.
7
,
P491
(
2018
).
31.
Y.
Gong
,
K.
Venkatraman
, and
R.
Akolkar
,
J. Electrochem. Soc.
165
,
D282
(
2018
).
32.
N.
Toyoda
and
A.
Ogawa
,
J. Phys. D: Appl. Phys.
50
,
184003
(
2017
).
33.
W.
Xie
,
P. C.
Lemaire
, and
G. N.
Parsons
,
ACS Appl. Mater. Interfaces
10
,
9147
(
2018
).
34.
N. R.
Johnson
and
S. M.
George
,
ACS Appl. Mater. Interfaces
9
,
34435
(
2017
).
35.
Y.
Lee
and
S. M.
George
,
Chem. Mater.
29
,
8202
(
2017
).
36.
N.
Marchack
,
J. M.
Papalia
,
S.
Engelmann
, and
E. A.
Joseph
,
J. Vac. Sci. Technol. A
35
,
05C314
(
2017
).
37.
M.
Konh
,
C.
He
,
X.
Lin
,
X.
Guo
,
V.
Pallem
,
R. L.
Opila
,
A. V.
Teplyakov
,
Z.
Wang
, and
B.
Yuan
,
J. Vac. Sci. Technol. A
37
,
021004
(
2019
).
38.
J. C.
Gertsch
,
A. M.
Cano
,
V. M.
Bright
, and
S. M.
George
,
Chem. Mater.
31
, 3624 (
2019
).
39.
X.
Lin
,
M.
Chen
,
A.
Janotti
, and
R.
Opila
,
J. Vac. Sci. Technol. A
36
,
051401
(
2018
).
40.
K. C.
Chen
,
T. W.
Chu
,
C. R.
Wu
,
S. C.
Lee
, and
S. Y.
Lin
,
2D Mater.
4
,
034001
(
2017
).
41.
Y.
Lee
,
N. R.
Johnson
, and
S. M.
George
,
Chem. Mater.
32
,
5937
(
2020
).
42.
J.
Li
et al,
Materials (Basel)
13
,
771
(
2020
).
43.
M. R.
Aziziyan
,
H.
Sharma
, and
J. J.
Dubowski
,
ACS Appl. Mater. Interfaces
11
,
17968
(
2019
).
44.
H.
Zhu
,
X.
Qin
,
L.
Cheng
,
A.
Azcatl
,
J.
Kim
, and
R. M.
Wallace
,
ACS Appl. Mater. Interfaces
8
,
19119
(
2016
).
45.
W.
Lu
,
Y.
Lee
,
J. C.
Gertsch
,
J. A.
Murdzek
,
A. S.
Cavanagh
,
L.
Kong
,
J. A.
Del Alamo
, and
S. M.
George
,
Nano Lett.
19
,
5159
(
2019
).
46.
N. R.
Johnson
,
J. K.
Hite
,
M. A.
Mastro
,
C. R.
Eddy
, and
S. M.
George
,
Appl. Phys. Lett.
114
,
243103
(
2019
).
47.
A.
Ludviksson
,
M.
Xu
, and
R. M.
Martin
,
Surf. Sci.
277
,
282
(
1992
).
48.
H.
Zhou
,
Y.-C.
Fu
,
M. M. A.
Mirza
, and
X.
Li
, in
AVS 18th International Conference on Atomic Layer Deposition (ALD)
,
Incheon, Korea
, 29 July–1 August 2018 (AVS, New York,
2018
).
49.
V.
Sharma
,
T.
Blomberg
,
S.
Haukka
,
S.
Cembella
,
M. E.
Givens
,
M.
Tuominen
,
R.
Odedra
,
W.
Graff
, and
M.
Ritala
,
Appl. Surf. Sci.
540
,
148309
(
2021
).
50.
A.
Roine
,
T.
Kotiranta
,
H.
Eerola
, and
P.
Lamberg
,
HSC Chemistry Ver. 7.1
(
Oktukumpu Research Oy
,
Pori
,
2002
).
51.
E.
Lassner
and
W.-D.
Schubert
,
Tungsten: Properties, Chemistry, Technology of the Element, Alloys, and Chemical Compounds
(
Springer
,
Boston, MA
,
1999
).
52.
See supplementary material online for additional thermodynamic modeling data, measured film thickness values, AES spectra, and AFM images.

Supplementary Material

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