SiCOH (Carbon-doped Oxide, CDO) is the industry-standard low-k dielectric material — a modified form of SiO₂ where some Si-O bonds are replaced with Si-CH₃ groups, reducing the film density and polarizability to lower the dielectric constant to $kappa approx 2.5-3.0$.
What Is SiCOH?
- Composition: Silicon, Carbon, Oxygen, Hydrogen in an amorphous network.
- Deposition: PECVD using organosilicon precursors (DEMS, OMCTS).
- $kappa$ Tuning: More carbon (methyl groups) = lower $kappa$ but weaker mechanical properties.
- Porous SiCOH: Adding porosity pushes $kappa$ below 2.5 (ULK region).
Why It Matters
- Workhorse: Used in every advanced logic process from 90nm to 3nm.
- Compatibility: Integrates well with existing BEOL processes (etch, CMP, barrier deposition).
- Trade-off: Lower $kappa$ variants are increasingly fragile, requiring careful process optimization.
SiCOH is the backbone of modern BEOL — the engineered glass that insulates billions of copper wires running through every advanced processor.