Gettering is the process of trapping metallic impurities (Fe, Cu, Ni, Cr, Co) away from electrically active device regions on the wafer front side by creating preferential trapping sites on the wafer backside or in the bulk, preventing these contaminants from degrading device performance through increased junction leakage, reduced carrier lifetime, and gate oxide integrity failures. Gettering types: (1) intrinsic gettering (IG—oxygen precipitates in the wafer bulk serve as trapping sites; CZ-grown silicon contains 10-20 ppma interstitial oxygen that precipitates during thermal cycling into SiOx precipitates and associated defects; a denuded zone of 20-50μm near the surface is kept precipitate-free by high-temperature surface outward diffusion of oxygen, while the bulk contains dense precipitates that trap metals), (2) extrinsic gettering (EG—intentional backside damage or deposition creates trapping sites; methods include backside mechanical damage (sandblasting), polysilicon backside deposition, phosphorus backside diffusion, and ion implant damage). Metal contamination effects: (1) iron—forms deep-level traps increasing junction leakage; Fe-B pairs degrade minority carrier lifetime; specification typically < 10¹⁰ cm⁻² for advanced logic, (2) copper—fast diffuser; precipitates at dislocations creating shorts and leakage; most problematic contaminant in modern fabs, (3) nickel—causes stacking faults and haze defects during oxidation. Gettering thermal process: typical IG recipe includes (1) high-temperature nucleation dissolution (1100-1200°C, 2-4 hours—dissolves small oxygen clusters and creates denuded zone), (2) low-temperature nucleation (650-750°C, 4-16 hours—nucleate oxygen precipitates in bulk), (3) precipitation growth (1000-1050°C, 4-16 hours—grow precipitates to effective gettering size). Modern device processing thermal cycles often provide sufficient precipitation without a dedicated gettering thermal step. Gettering effectiveness is verified by minority carrier lifetime measurements (μ-PCD), surface photovoltage (SPV), or TXRF/VPD-ICPMS metal analysis.