Atomic Layer Deposition for Superconducting Qubits

Superconducting NbN thin films deposited by plasma ALD with RF substrate bias

Superconducting metal nitrides exhibit superconducting behaviour at high critical temperatures (Tc) and achieve better performance in quantum devices because they have less lossy native oxides than typical sputtered superconducting materials. We've developed a plasma-enhanced ALD process to deposit high quality, high Tc NbN for superconducting devices.

• RF bias enables stress control to achieve minimal room temperature resistivity
• Low room temperature resistivity correlates to higher superconducting transition temperature (T_c)
• The only method for conformal coating of vertical TSVs with superconducting thin films
• 9 K  T_c measured at Oxford Instruments:
  • For ~45 nm NbN film deposited at 250°C
  • Room temperature ρ = 139 µΩcm; Tc = 12.9 K
• Higher temperature process possible resulting in higher T_c

Conformal, leak-free & low-pinhole tunnel barriers by plasma-enhanced ALD

Combine the benefits of plasma ALD (PE-ALD) with the capability of clustering systems to other technologies and unlock unique capabilities.

Key advantages of plasma ALD of Al₂O₃:

• Higher breakdown voltage
• Lower leakage current
• Low pinhole
• Very smooth films for minimum noise
• Higher density
• Atomic thickness precision
• Faster growth per cycle
• Low C & H content
  
  

Remove amorphous native oxide prior to growing high-quality PE-ALD of Al₂O₃ by either:

• Using in-situ pre-clean based on a nitriding/reducing plasma
• Clustering to an ALE or metal etch module