CMP combines chemical etching and mechanical abrasion to create atomically flat surfaces, essential for multi-layer device fabrication where surface topography must be controlled to within nanometres.
Metal CMP
Copper damascene CMP removes overburden Cu and stops precisely on the barrier layer, the key step in BEOL interconnect and RDL fabrication. Also: Al, W, Ta, and TiN planarization for MEMS electrodes, contact metals, and gate electrodes. Endpoint detection by eddy current (on Cu) or optical reflectometry prevents over-polish into the barrier layer. Cu dishing within wide lines and SiO₂ erosion between closely spaced lines are measured and reported post-CMP.
Insulator CMP (SiO₂/SiN)
Oxide and nitride planarization for shallow trench isolation (STI) fill, pre-bonding surface preparation, and interlayer dielectric (ILD) planarization between metal layers. Excellent within-wafer uniformity across 12-inch substrates. Low defectivity slurry chemistries minimize scratch density on STI oxide, critical for maintaining gate oxide integrity adjacent to STI edges.
Polymer CMP (Polyimide/BCB)
CMP of polyimide, BCB, and other organic dielectric layers used in RDL fabrication and advanced packaging. Planarises polymer passivation layers after cure and patterning to enable subsequent Cu metallisation and lithography. BCB CMP is particularly critical for fan-out FOWLP where multi-layer polymer RDL requires each layer to be perfectly flat before the next layer is coated.
Pre-Bonding CMP
Ultra-precise CMP immediately before wafer bonding, achieving <0.5nm Ra surface roughness required for direct fusion bonding (Si-Si) and Cu-Cu hybrid bonding. Surface roughness and flatness are verified by AFM before the wafer pair proceeds to bonding. Even a single surface particle or scratch can create a void in the bond interface that propagates during annealing, pre-bonding CMP is the most defect-sensitive CMP application we perform.
Optical Grade Polishing
Sub-Ångström surface polishing for fused silica, quartz, sapphire, and calcium fluoride optical substrates. Required for high-power laser optics, UV photomask substrates, and precision mirror blanks where any surface micro-roughness increases scatter loss and reduces laser damage threshold. Polishing slurry, pad conditioning, and process parameters are different from semiconductor CMP, this is precision optics grinding, not standard semiconductor polishing.
Custom Slurry Formulations
Custom CMP slurry formulations are available for non-standard applications: SiC polishing slurry for power device wafer preparation (SiC is among the hardest semiconductor materials, standard Si slurries do not work), Si wafer mirror polishing slurry, and custom oxide slurries for specific ILD materials. Custom slurry development typically requires 2–4 weeks of process qualification on monitor wafers before production use.