SiON Interfacial Layer is a nitrogen-enriched variant of the SiO₂ interfacial layer — where nitrogen incorporation into the thin IL provides better resistance to boron penetration, slightly higher $kappa$, and improved reliability while maintaining good interface quality.

What Is SiON IL?

• Formation: Grow thin SiO₂ by chemical/thermal oxidation, then nitridize using plasma nitridation (decoupled plasma nitridation, DPN) or NH₃ anneal.
• N Content: ~10-30 atomic % nitrogen at the surface, graded toward pure SiO₂ at the Si interface.
• $kappa$: ~4.5-5.5 (slightly higher than SiO₂'s 3.9, reducing EOT contribution).

Why It Matters

• Boron Blocking: Nitrogen blocks boron diffusion from P+ poly gates (critical for PMOS, pre-HKMG era).
• EOT Reduction: Higher $kappa$ of SiON vs. SiO₂ allows a physically thicker IL for the same EOT.
• Reliability: Nitrogen improves NBTI (Negative Bias Temperature Instability) resistance.

SiON IL is the reinforced interface — adding nitrogen to the oxide bridge for better blocking, higher capacitance, and improved long-term reliability.