TY - JOUR
T1 - Thermal atomic layer etching of copper by sequential steps involving oxidation and exposure to hexafluoroacetylacetone
AU - Mohimi, Elham
AU - Chu, Xiaoqing I.
AU - Trinh, Brian B.
AU - Babar, Shaista
AU - Girolami, Gregory S.
AU - Abelson, John R.
N1 - Publisher Copyright:
© The Electrochemical Society
PY - 2018
Y1 - 2018
N2 - We describe an atomic layer etching (ALE) method for copper that involves cyclic exposure to an oxidant and hexafluoroacetylacetone (Hhfac) at 275 ◦ C. The process does not attack dielectrics such as SiO 2 or SiN x , and the surface reactions are kinetically self-limiting to afford a precise etch depth that is spatially uniform. Exposure of a copper surface to molecular oxygen, O 2 , a weak oxidant, forms a -0.3 nm thick layer of Cu 2 O, which is removed in a subsequent step by exposure to Hhfac. The etch reaction involves disproportionation of Cu(hfac) intermediates, such that -0.09 nm copper is removed per cycle. Exposure of copper to ozone, a stronger oxidant, affords -15 nm of CuO; when this oxidized surface is exposed to Hhfac, 8.4 nm of copper is removed per cycle. The etch products, Cu(hfac) 2 and H 2 O, are efficiently pumped away; H 2 O, a poor oxidant, does not attack the bare Cu surface. The roughness of the copper surface increases slowly over successive etch cycles. Thermochemical and bulk etching data indicate that this approach should work for a variety of other metals.
AB - We describe an atomic layer etching (ALE) method for copper that involves cyclic exposure to an oxidant and hexafluoroacetylacetone (Hhfac) at 275 ◦ C. The process does not attack dielectrics such as SiO 2 or SiN x , and the surface reactions are kinetically self-limiting to afford a precise etch depth that is spatially uniform. Exposure of a copper surface to molecular oxygen, O 2 , a weak oxidant, forms a -0.3 nm thick layer of Cu 2 O, which is removed in a subsequent step by exposure to Hhfac. The etch reaction involves disproportionation of Cu(hfac) intermediates, such that -0.09 nm copper is removed per cycle. Exposure of copper to ozone, a stronger oxidant, affords -15 nm of CuO; when this oxidized surface is exposed to Hhfac, 8.4 nm of copper is removed per cycle. The etch products, Cu(hfac) 2 and H 2 O, are efficiently pumped away; H 2 O, a poor oxidant, does not attack the bare Cu surface. The roughness of the copper surface increases slowly over successive etch cycles. Thermochemical and bulk etching data indicate that this approach should work for a variety of other metals.
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U2 - 10.1149/2.0211809jss
DO - 10.1149/2.0211809jss
M3 - Article
AN - SCOPUS:85059933871
SN - 2162-8769
VL - 7
SP - P491-P495
JO - ECS Journal of Solid State Science and Technology
JF - ECS Journal of Solid State Science and Technology
IS - 9
ER -