Guard Ring Structure for Etch CD Uniformity

The patent applies preliminary action by forming a planarization layer and guard ring structure before the lithography patterning process. This pre-preparation creates a uniform surface topology that eliminates topography-induced CD variations during subsequent lithography steps, directly resolving the contradiction between proceeding with fabrication on uneven surfaces and achieving CD uniformity.

The patent merges multiple functions into the guard ring structure: it serves as both a planarization element (creating uniform surface topology) and a process constraint (defining patterning boundaries). This consolidation achieves CD uniformity improvement while minimizing the addition of separate processing steps, balancing fabrication precision with process complexity.

The guard ring structure acts as an intermediary that confines and controls the flowable planarization material. By providing physical boundaries, the guard ring ensures the material flows only to where needed and maintains precise dimensional control during deposition, eliminating the material control challenges that would otherwise arise from using flowable planarization materials.