Spectroscopic-ellipsometric study of native oxide removal by liquid phase HF process

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Microelectromechanical systems (MEMS) fabrication requires pristine silicon (Si) surfaces.
• Hydrofluoric acid (HF) is commonly used for Si surface cleaning and etching.
• Understanding surface passivation is critical for device reliability.

Purpose of the Study:

• To investigate the effect of liquid-phase hydrofluoric acid (HF) cleaning on Si<100> surfaces using spectroscopic ellipsometry (SE).
• To characterize the hydrogen-terminated (H-terminated) Si surface as an equivalent dielectric layer.
• To assess the chemical stability and surface roughness after HF treatment.

Main Methods:

• Ex situ spectroscopic ellipsometry (SE) measurements were performed on Si<100> surfaces.
• Fourier transform infrared spectroscopy (FTIR) was used to study H-termination.
• Analysis of the H-terminated Si surface as an equivalent dielectric layer.

Main Results:

• SE analyses confirmed that a 20-second dip in 100:5 HF solution followed by rinsing passivates the Si<100> surface.
• The H-terminated Si surface demonstrated chemical stability.
• Surface roughness of the HF-etched Si<100> was quantified using SE.

Conclusions:

• Ex situ SE is a non-destructive technique for evaluating the passivation state of H-terminated Si<100> surfaces.
• HF cleaning effectively passivates Si surfaces for microelectromechanical systems applications.
• The H-terminated layer's stability and characteristics can be monitored using SE.