Houyem Hafdi

Ambient pressure XPS studies of atomic layer deposition of AlN show that formation of AlO _x hinders formation of AlN.

Gallium nitride (GaN) is a wide-bandgap semiconductor that forms a cornerstone in several electronic devices in modern society, such as light-emitting diodes and chargers for computers and phones. Gallium production...

Gallium nitride (GaN) is a commonly used semiconductor owing to its high chemical and thermal stability, which makes it suitable for various applications in modern electronics. GaN film deposition is favored by atomic layer deposition (ALD) with triethylgallium (TEG) and ammonia (NH3) plasma as precursors. However, the surface reaction pathways of TEG under ALD conditions have not been experimentally evaluated. In this study, the surface chemistry of GaN films deposited on Si (100) during ALD with TEG and NH3 with and without plasma activation as precursors was investigated using mass spectrometry. The results suggest that the surface chemistry of the deposition process mainly consists of ethyl ligand elimination upon the TEG pulse, followed by ligand exchange during NH3 pulsing to form ethane (C2H6) as a reaction by-product on an NH2-terminated surface.

We explored the surface chemistry in ALD of AlN from tris-dimethylamido aluminum (Al(NMe₂)₃) and ammonia using mass spectrometry. We suggest surface mechanisms involving β-hydride elimination and ligand decomposition, as well as ligand exchange.

Dialkylamido compounds, such as tris-dimethylamido aluminum (TDMAA, Al(NMe2)3) and tetrakis-dimethylamido titanium (TDMAT, Ti(NMe2)4) are interesting precursors for depositing nitrides using atomic layer deposition (ALD) due to their high volatility and reactivity at low temperatures. In this study, we explored surface chemistry using mass spectrometry and discovered that the surface mechanisms involved β-hydride elimination and ligand decomposition, as well as transamination and hydrogenation reactions which facilitate ligand exchange. This is mainly based on the -N(Me)2 and HN(Me)2 detected during both TDMAA and NH3 pulses, and CH4 signals detected during the NH3 pulse stage. The expected reductive elimination of the two dimethylamido ligands, via a direct nitrogen-nitrogen coupling reaction was not observed, suggesting that it is less thermodynamically favorable compared to reduction by NH3. Arrhenius analysis between 150 and 300 °C found activation energies (Ea) = 27-30 kJmol-1 and pre-exponential factors (A) = 3-5 s-1 suggesting for the reaction between TDMAA and NH₃.

Aluminum nitride (AlN) is a semiconductor with a very wide band gap and a potential dielectric material. Deposition of thin AlN films is routinely done by several techniques, including atomic layer deposition (ALD). In this study, we deposited AlN using ALD with trimethylaluminum (TMA) as the Al precursor and ammonia (NH₃) with and without plasma activation as the N precursor in the temperature range from 100 to 400 °C while monitoring the surface reactions using mass spectrometry. Our results, combined with recent quantum chemical modelling, suggest that the surface chemistry of the deposition process is chemisorption of TMA followed by reductive elimination of the methyl groups to render mono methyl aluminum species. The NH₃ chemisorption is done by ligand exchange to form CH₄ and an –NH₂ terminated surface.

Aluminum nitride (AlN) is a semiconductor with a very wide band gap and a potential dielectric material. Deposition of thin AlN films is routinely done by several techniques, including atomic layer deposition (ALD). In this study, we deposited AlN using ALD with trimethylaluminum (TMA) as the Al precursor and ammonia (NH3) with and without plasma activation as the N precursor in the temperature range from 100 to 400 °C while monitoring the surface reactions using mass spectrometry. Our results, combined with recent quantum chemical modelling, suggest that the surface chemistry of the deposition process is chemisorption of TMA followed by reductive elimination of the methyl groups to render mono methyl aluminum species. The NH3 chemisorption is done by ligand exchange to form CH4 and an -NH2 terminated surface.