7nm FinFET

In the shallow trench isolation (STI) module, the Pad Oxide Growth step serves as a critical mechanical and chemical intermediary between the bare silicon substrate and the subsequent Silicon Nitride (SiN) hardmask deposition [T1]. Following the pre-clean process, the bare silicon wafer is exposed and highly susceptible to process-induced damage [A1]. During the STI process, the SiN film acts as a robust mask for subsequent silicon trench etching [P2]. However, SiN films possess high intrinsic…

• [High] Stress-Induced Active Area Defects: If the pad oxide is grown too thin, it fails to effectively act as a strain buffer between the highly stressed SiN hardmask and the silicon substrate [P2]. This unbuffered mechanical stress propagates into the active silicon region, altering the local band structure and degrading carrier mobility [A1]. Under extreme stress gradients, this can culminate in the nucleation of irreversible crystalline dislocations within the fin body *(Engineering Pra…