Band-bending at buried SiO2/Si interface as probed by XPS

Area of Science:

• Surface Science
• Materials Science
• Semiconductor Physics

Background:

• The SiO2/Si interface is crucial for semiconductor device performance.
• Understanding charge dynamics at this interface is essential for device stability and efficiency.
• Direct probing of buried interfaces can be challenging.

Purpose of the Study:

• To investigate photoinduced shifts in core-level binding energies at SiO2/Si interfaces.
• To determine the influence of silicon type (p-type vs. n-type) on these photoinduced shifts.
• To correlate observed shifts with the charge state of the interface.

Main Methods:

• Utilizing X-ray photoelectron spectroscopy (XPS) to analyze Si2p, O1s, and C1s core-level spectra.
• Examining samples with varying oxide layers (thermal/anodic) and organic coatings on p- and n-Si wafers.
• Employing multiple illumination sources to induce photoeffects.

Main Results:

• Significant photoinduced shifts (0.2–0.5 eV) were observed for p-type Si samples.
• Substantially smaller shifts (<0.1 eV) were detected for n-type Si samples.
• Shifts were independent of oxidation method, oxide thickness, organic layer type, and light source color.

Conclusions:

• The observed photoinduced shifts are indicative of the charge state of the SiO2/Si interface.
• This phenomenon provides a method to probe even buried interfaces (up to 20 nm oxide thickness).
• The distinct behavior between p-type and n-type silicon highlights differences in interface charge dynamics.