Following Mid Vertical Grid Deposition and W CMP, the wafer presents a planarized surface with exposed mid-grid metal and dielectric regions (Engineering Practice).The Upper Vertical Grid Barrier Deposition step prepares the interface for the subsequent Upper Vertical Grid Deposition by providing an essential adhesion and diffusion-blocking layer A2.Unlike the Ta-based Bottom Barrier (step #254) which often lines high-aspect-ratio deep trench isolation directly contacting the silicon substrate,