Direct evidence of flat band voltage shift for TiN/LaO or ZrO/SiO₂ stack structure via work function depth profiling

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Controlling electrical properties of semiconductor devices is crucial for performance.
• Metal-oxide-semiconductor (MOS) stacks are fundamental components in modern electronics.
• Tuning the flat band voltage (VFB) is essential for device optimization.

Purpose of the Study:

• To demonstrate controlled flat band voltage (VFB) shifts in TiN/(LaO or ZrO)/SiO2 stack structures.
• To investigate the mechanisms behind VFB shifts, including metal diffusion and silicate formation.
• To explore work function modulation via doping for potential applications.

Main Methods:

• Fabrication of TiN/(LaO or ZrO)/SiO2/Si stack structures.
• Transmission electron microscopy (TEM) for analyzing metal diffusion.
• Energy dispersive spectroscopy (EDS) line profiling for silicate formation.
• Auger electron spectroscopy (AES) for work function measurement and depth profiling.

Main Results:

• Demonstrated controllable VFB shifts in the studied stack structures.
• Confirmed metal (La, Zr) diffusion into TiN and silicate formation at the interface.
• Showcased direct work function modulation as a function of La/Zr doping concentration.
• Developed an analytical method for interface dipole determination via work function depth profiling.

Conclusions:

• Metal doping and interface silicate formation are effective methods for controlling VFB in TiN-based gate stacks.
• Work function engineering is achievable through controlled doping in these structures.
• The proposed analytical method provides a pathway for understanding interface properties.