cross-section sem

Cross-section SEM images a cleaved or FIB-cut wafer edge to reveal layer structures, film thicknesses, feature profiles, and subsurface defects. **Preparation**: **Cleave**: Break wafer through region of interest. Quick but imprecise location. **FIB (Focused Ion Beam)**: Mill precise cross-section at exact location of interest using Ga+ beam. Much more precise. **Imaging**: SEM images the exposed cross-section face. Shows all layers in profile view. **Information**: Film thicknesses, sidewall angles, undercut, notching, voids, grain structure, interface quality, defect morphology. **Resolution**: Nanometer-scale features visible. Modern FIB-SEM achieves <1nm resolution. **3D profile**: Shows feature shape that top-down SEM cannot - sidewall angle, footing, bowing, retrograde profiles. **Failure analysis**: Primary technique for investigating process defects, yield issues, and reliability failures. **TEM prep**: FIB used to prepare thin lamellae (<100nm thick) for transmission electron microscopy. **Destructive**: Cleaving or FIB milling destroys the measured area. Cannot be done inline on production wafers. **Site-specific**: FIB enables targeting exact features or defects. Navigate to coordinates from defect inspection tools. **Dual-beam FIB-SEM**: Combined FIB and SEM in one tool. Mill with ion beam, image with electron beam simultaneously. **Artifacts**: FIB milling can introduce artifacts (curtaining, redeposition, Ga implantation). Careful technique minimizes these.