Thermal atomic layer etching of crystalline aluminum nitride using sequential, self-limiting hydrogen fluoride and Sn(acac){sub 2} reactions and enhancement by H{sub 2} and Ar plasmas

Journal Article · Thu Sep 15 04:00:00 EDT 2016 · Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films

DOI:https://doi.org/10.1116/1.4959779· OSTI ID:22592847

Johnson, Nicholas R.; Sun, Huaxing; Sharma, Kashish ^[1]

---

1. Department of Chemistry and Biochemistry, University of Colorado at Boulder, Colorado 80309 (United States)

Thermal atomic layer etching (ALE) of crystalline aluminum nitride (AlN) films was demonstrated using sequential, self-limiting reactions with hydrogen fluoride (HF) and tin(II) acetylacetonate [Sn(acac){sub 2}] as the reactants. Film thicknesses were monitored versus number of ALE reaction cycles at 275 °C using in situ spectroscopic ellipsometry (SE). A low etch rate of ∼0.07 Å/cycle was measured during etching of the first 40 Å of the film. This small etch rate corresponded with the AlO{sub x}N{sub y} layer on the AlN film. The etch rate then increased to ∼0.36 Å/cycle for the pure AlN films. In situ SE experiments established the HF and Sn(acac){sub 2} exposures that were necessary for self-limiting surface reactions. In the proposed reaction mechanism for thermal AlN ALE, HF fluorinates the AlN film and produces an AlF{sub 3} layer on the surface. The metal precursor, Sn(acac){sub 2}, then accepts fluorine from the AlF{sub 3} layer and transfers an acac ligand to the AlF{sub 3} layer in a ligand-exchange reaction. The possible volatile etch products are SnF(acac) and either Al(acac){sub 3} or AlF(acac){sub 2}. Adding a H{sub 2} plasma exposure after each Sn(acac){sub 2} exposure dramatically increased the AlN etch rate from 0.36 to 1.96 Å/cycle. This enhanced etch rate is believed to result from the ability of the H{sub 2} plasma to remove acac surface species that may limit the AlN etch rate. The active agent from the H{sub 2} plasma is either hydrogen radicals or radiation. Adding an Ar plasma exposure after each Sn(acac){sub 2} exposure increased the AlN etch rate from 0.36 to 0.66 Å/cycle. This enhanced etch rate is attributed to either ions or radiation from the Ar plasma that may also lead to the desorption of acac surface species.

• OSTI ID: 22592847
• Journal Information: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films Journal Issue: 5 Vol. 34; ISSN 0734-2101; ISSN JVTAD6
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
42 ENGINEERING
ALUMINIUM
ALUMINIUM FLUORIDES
ALUMINIUM NITRIDES
DESORPTION
ELLIPSOMETRY
ETCHING
FILMS
FLUORINE
HYDROGEN
HYDROGEN FLUORIDES
ION EXCHANGE
LAYERS
LIGANDS
PLASMA
PRECURSOR
REACTION KINETICS
SURFACES
THICKNESS
TIN
TIN COMPOUNDS