Three-Dimensional Surface Treatment of MoS₂ Using BCl₃ Plasma-Derived Radicals

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Device Physics

Background:

• Next-generation gate-all-around field-effect transistors (FETs) require uniform high-k dielectric films on two-dimensional transition metal dichalcogenide (TMDC) semiconductors.
• Existing surface treatments often cause damage or are unsuitable for three-dimensional (3D) structures, hindering uniform atomic layer deposition (ALD) on inert TMDC surfaces.
• Molybdenum disulfide (MoS₂) is a promising TMDC material for advanced FET channels.

Purpose of the Study:

• To develop a 3D-compatible, damage-free surface treatment for MoS₂.
• To enable uniform ALD of ultrathin high-k dielectric films on functionalized MoS₂ surfaces.
• To demonstrate the effectiveness of the pretreatment for fabricating functional FET devices.

Main Methods:

• Functionalization of MoS₂ surfaces using BCl₃ plasma-derived radical treatment.
• Atomic layer deposition (ALD) of an ultrathin Al₂O₃ film on treated MoS₂.
• Microstructural analysis (e.g., TEM), spectroscopy (OES, XPS), and device electrical measurements (FETs).

Main Results:

• Achieved complete coverage of a ~2 nm Al₂O₃ film on planar MoS₂ surfaces.
• Demonstrated applicability to 3D structures using suspended MoS₂ channels.
• Confirmed negligible damage to MoS₂ via Raman, PL, and electrical measurements.
• Successfully fabricated and operated a top-gated FET with a ~5 nm Al₂O₃ dielectric.

Conclusions:

• BCl₃ plasma-derived radicals effectively functionalize MoS₂ surfaces for uniform ALD nucleation.
• The developed radical treatment is a damage-free method suitable for both 2D and 3D TMDC structures.
• This pretreatment is crucial for realizing high-performance FETs with TMDC channels and ALD high-k dielectrics.