Journal
ACS NANO
Volume 9, Issue 2, Pages 2061-2070Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn507277f
Keywords
atomic layer etching; Al2O3; sequential exposures; thermal reactions; quartz crystal microbalance; X-ray reflectivity; atomic layer deposition
Categories
Funding
- National Science Foundation [CHE-1306131]
- Department of Energy through the DOE-BATT program
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1306131] Funding Source: National Science Foundation
Ask authors/readers for more resources
The atomic layer etching (ALE) of Al2O3 was demonstrated using sequential, self-limiting thermal reactions with tin(II) acetylacetonate (Sn(acac)2) and hydrogen fluoride (HF) as the reactants. The Al2O3 samples were Al2O3 atomic layer deposition (ALD) films grown using trimethylaluminum and H2O. The HF source was HF-pyridine. Al2O3 was etched linearly with atomic level precision versus number of reactant cycles. The Al2O3 ALE was monitored at temperatures from 150 to 250 degrees C. Quartz crystal microbalance (QCM) studies revealed that the sequential Sn(acac)2 and HF reactions were self-limiting versus reactant exposure. QCM measurements also determined that the mass change per cycle (MCPC) increased with temperature from -4.1 ng/(cm(2) cycle) at 150 degrees C to -18.3 ng/(cm(2) cycle) at 250 degrees C. These MCPC values correspond to etch rates from 0.14 angstrom/cycle at 150 degrees C to 0.61 angstrom/cycle at 250 degrees C based on the Al2O3 ALD film density of 3.0 g/cm3. X-ray reflectivity (XRR) analysis confirmed the linear removal of Al2O3 and measured an Al2O3 ALE etch rate of 0.27 angstrom/cycle at 200 degrees C. The XRR measurements also indicated that the Al2O3 films were smoothed by Al2O3 ALE. The overall etching reaction is believed to follow the reaction Al2O3 + 6Sn(acac)(2) + 6HF 2Al(acac)3 + 6SnF(acac) + 3H(2)O. In the proposed reaction mechanism, the Sn(acac)2 reactant donates acac to the substrate to produce Al(acac)3. The HF reactant allows SnF(acac) and H2O to leave as reaction products. The thermal ALE of many other metal oxides using Sn(acac)(2) or other metal beta-diketonates, together with HF, should be possible by a similar mechanism. This thermal ALE mechanism may also be applicable to other materials such as metal nitrides, metal phosphides, metal sulfides and metal arsenides.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available