Chemical, Structural, and Electrical Changes in Molecular Layer-Deposited Hafnicone Thin Films after Thermal...

Area of Science:

• Materials Science
• Thin Film Deposition
• Nanotechnology

Background:

• Molecular Layer Deposition (MLD) and Atomic Layer Deposition (ALD) are crucial techniques for fabricating thin films.
• Hafnium-based materials are of interest for various electronic applications.
• Understanding the impact of post-deposition annealing on MLD films is essential for property tuning.

Purpose of the Study:

• To investigate the effects of post-deposition annealing on molecular layer-deposited (MLD) hafnicone films.
• To compare the properties of annealed MLD hafnicone films with atomic layer-deposited (ALD) hafnia films.
• To explore the potential of annealing MLD films for creating materials with tailored low density and relative permittivity.

Main Methods:

• Deposition of hafnicone films using tetrakis(dimethylamido)hafnium (TDMAH) and ethylene glycol via MLD.
• Deposition of hafnia films using TDMAH and water via ALD at 120 °C.
• In situ X-ray reflectivity (XRR) and X-ray diffraction (XRD) to monitor thickness, density, and crystallization.
• Fourier transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) for chemical analysis.
• Measurement of dielectric constant and etch rate (CF4/O2).

Main Results:

• Annealing MLD hafnicone films to 400 °C resulted in a 70% thickness decrease and ~100% density increase, though density remained lower than ALD hafnia.
• Significant thickness reduction in hafnicone films occurred between 150 °C and 350 °C.
• Crystallization temperature for MLD hafnicone films (600 °C) was higher than for ALD hafnia films (350 °C).
• UV exposure during annealing did not significantly alter the chemistry of hafnicone films.
• Hafnicone films exhibited lower dielectric constants than hafnia films across the studied temperature range.
• The CF4/O2 etch rate of annealed hafnicone films was comparable to that of hafnia films.
• Thermal conductivity initially decreased (up to 250 °C) then increased (350 °C) with annealing, attributed to porosity and densification.

Conclusions:

• Post-deposition annealing is an effective strategy for tuning the properties of MLD hafnicone films.
• Annealed MLD hafnicone films offer a pathway to achieving low density and low relative permittivity.
• Hafnicone films demonstrate potential for applications requiring thin films with reduced dielectric properties.