Physics / mechanism
Chemical Mechanical Planarization (CMP) removes material from a wafer surface via simultaneous chemical etching and mechanical abrasion. A rotating wafer is pressed against a polishing pad flooded with slurry—abrasive nanoparticles (typically silica or ceria, 50–200 nm) suspended in a pH-controlled chemical solution. Material removal follows Preston’s equation: MRR = k × P × v, where pressure and velocity are the primary control levers. Target planarity: <1 nm Ra across 300 mm wafers. CMP is mandatory at STI, ILD, metal interconnect, and high-k/metal gate steps. Leading equipment: Applied Materials Reflexion, Ebara, Entegris (consumables). Global CMP consumables market ~$3B; equipment ~$2B.
Competitive landscape
CMP competes with dry etch-back planarization (inferior global planarity) and electrochemical mechanical planarization (eCMP, lower pressure for soft metals like Cu). Adjacent approaches: atomic layer etching for sub-nm removal, stress-engineered films that self-planarize, sacrificial spin-on dielectrics. For advanced nodes and photonics, eCMP is gaining ground for damage-sensitive III-V or low-k surfaces.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.