The STI Liner Oxidation step follows anisotropic trench etching and cleaning, serving as the critical interface preparation before subsequent CVD dielectric fill T1.In the 40nm CMOS Image Sensor (CIS) process flow, this step repairs plasma-induced lattice damage on the trench sidewalls and bottoms generated during the preceding reactive ion etch phase A2.Furthermore, growing this thin thermal oxide provides a pristine silicon-dielectric interface that minimizes interface trap states, which are a