14nm FinFET

Device Context and Integration Rationale

The SiN hard mask etch in the FIN_PATTERN module is positioned after the sequential amorphous silicon and SiO2 hard mask etch steps to complete the vertical pattern transfer stack that ultimately defines fin critical dimensions and pitch fidelity for 14 nm FinFETs [A2].In this multilayer hard mask scheme, the SiN layer functions as the mechanically and chemically robust terminal mask that must be precisely opened to expose the underlying silicon fin…

• [High] Lateral SiN Undercut: Insufficient anisotropy in the plasma etch allows chemical reactions to proceed on sidewalls as well as horizontal surfaces, leading to lateral erosion of the SiN mask and subsequent fin width variation, which directly impacts electrostatic control in FinFETs [P1][T1].- [Medium] Over-Etch into Underlying Layers: Excessive etch continuation after SiN clearance results in unintended exposure or damage to underlying materials, arising from limited etch selecti…