Nested 3D Memory Word Line Contacts for Easier Deep Etching

The patent implements nested WL contact structures where inner WL contacts are positioned within outer WL contacts. This nesting arrangement allows multiple contact structures to share a common etching pathway, effectively reducing the aspect ratio that each individual contact must traverse. The inner contacts benefit from the broader opening provided by outer contacts, making etching feasible for deep contacts in high-density 3D memory arrays.

The patent transitions from a single-dimensional contact approach to a multi-dimensional nested contact architecture. By arranging contacts in nested concentric patterns across multiple dimensions, the design allows deeper contacts to be reached through shared etching paths, effectively distributing the etching burden and reducing the effective aspect ratio for each individual contact.

The patent merges multiple WL contact structures into nested configurations where outer contacts provide broader openings that accommodate inner contacts. This merging allows the outer contacts to serve dual purposes: providing structural support and creating enlarged etching pathways for inner contacts. The result is improved etching ease for deep contacts without requiring proportional increases in the overall memory array footprint.

By nesting contacts within contacts, the patent enables inner contacts to utilize the enlarged opening created by outer contacts. This nesting strategy allows critical dimensions to be effectively increased for deep contacts without expanding the lateral footprint of the memory array, as the nested structure fits within the existing contact envelope.

The patent employs preliminary self-aligned formation of nested contact structures. Outer contacts are formed first, establishing reference structures that guide subsequent formation of inner contacts. This sequential, self-aligned approach reduces the need for high-precision independent alignment steps, as each contact is positioned relative to previously formed contacts rather than requiring absolute positioning precision.

The nested contact structure utilizes self-aligned formation processes where outer contacts automatically define the positioning framework for inner contacts. The structure serves its own alignment function, with each contact level providing reference for the next, thereby reducing dependency on external alignment precision mechanisms and enabling higher density arrangements.