Thursday, January 7, 2021

Surface ligand removal in atomic layer deposition of GaN using triethylgallium

Here is a paper with really impressive results on Low Temperature GaN ALD using ABC-type pulsed sequence from Henrik Pedersen group Linköping University - They insert a step between triethylgallium and ammonia to improve the deposition.

To study how to enhance the ethyl ligand removal from the surface, an additional pulse was added between the TEG and NH3/Ar plasma. This made the ALD process into an ABC-type pulsed ALD process with TEG as A-pulse, the additional gas as the B-pulse and the NH3/Ar plasma as C-pulse.

Depositions were carried out in a Picosun R-200 atomic layer deposition tool without a load lock chamber and a operating pressure of 6 hPa.

Surface ligand removal in atomic layer deposition of GaN using triethylgallium
Journal of Vacuum Science & Technology A 39, 012411 (2021);
Petro Deminskyi, Chih-Wei Hsu, Babak Bakhit, Polla Rouf, and Henrik Pedersen

Gallium nitride (GaN) is one of the most important semiconductor materials in modern electronics. While GaN films are routinely deposited by chemical vapor deposition at around 1000 °C, low-temperature routes for GaN deposition need to be better understood. Herein, we present an atomic layer deposition (ALD) process for GaN-based on triethyl gallium (TEG) and ammonia plasma and show that the process can be improved by adding a reactive pulse, a “B-pulse” between the TEG and ammonia plasma, making it an ABC-type pulsed process. We show that the material quality of the deposited GaN is not affected by the B-pulse, but that the film growth per ALD cycle increases when a B-pulse is added. We suggest that this can be explained by the removal of ethyl ligands from the surface by the B-pulse, enabling a more efficient nitridation by the ammonia plasma. We show that the B-pulsing can be used to enable GaN deposition with a thermal ammonia pulse, albeit of x-ray amorphous films.

Prof. Henrik Pedersen in the lab.

Growth per cycle (GPC) for film deposition at different temperatures (a) and with different TEG pulse time (b).

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