Stacked Memory Array Termination Structure for Contact Alignment
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Solution Overview
Problem
The formation of stacked memory arrays faces challenges in terminating access openings to prevent dielectric removal and metal shorts between memory cell blocks, leading to stress relief and movement of semiconductor structures, which complicates the alignment of data line contacts and reduces memory cell density.
Innovation Solution
The approach involves forming termination openings concurrently with contact openings and creating a sacrificial material to isolate blocks of memory cells without forming T-intersections, thereby preventing dielectric removal and metal shorts, and using additional openings to access dielectrics for replacement with metal, ensuring proper alignment and increased memory cell density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If access openings are formed through the stack to enable dielectric removal and metal formation, then memory cell formation is enabled, but stress relief occurs causing movement of semiconductor structures and misalignment of data line contacts
Solution Approach 1:
The access openings are segmented into two distinct segments: a first segment that provides access to dielectrics for removal and metal formation, and a second segment that terminates at a termination structure. This segmentation allows the opening to fulfill its access function while being blocked from causing stress relief that would lead to misalignment.
Solution Approach 2:
A termination structure acts as an intermediary element that blocks the access opening. This termination structure prevents the opening from extending through the entire stack, thereby blocking stress relief and preventing movement of semiconductor structures and misalignment of data line contacts, while still allowing the opening to provide necessary access for dielectric removal and metal formation.
2Ease of manufacture
If access openings extend through the entire stack, then complete access to dielectrics is achieved, but electrical shorts between adjacent blocks of memory cells occur
Solution Approach 1:
The access opening is divided into two segments with the second segment blocked by a termination structure. This segmentation allows dielectric access in the first segment while preventing continuous metal formation through the termination structure in the second segment, thereby avoiding electrical shorts between adjacent memory cell blocks.
Solution Approach 2:
The termination structure serves as an intermediary barrier within the access opening that permits dielectric removal and metal formation in the first segment while blocking continuous metal extension into the second segment. This prevents electrical shorts between adjacent blocks of memory cells while maintaining necessary access for manufacturing.
3Reliability
If T-intersections are formed to terminate access openings, then dielectric removal is prevented, but the process complexity increases and manufacturing difficulty arises
Solution Approach 1:
The problematic T-intersection geometry is extracted and replaced with a simpler termination structure that blocks the access opening. This termination structure achieves the same functional outcome of preventing dielectric removal and metal formation while eliminating the manufacturing complexity associated with forming T-intersections.
Data Source
AI summary
A termination opening can be formed through the stack alternating dielectrics concurrently with forming contact openings through the stack. A termination structure can be formed in the termination opening. An additional opening can be formed through the termination structure and through the stack between groups of semiconductor structures that pass through the stack. In another example, an opening can be formed through the stack so that a first segment of the opening is between groups of semiconductor structures in a first region of the stack and a second segment of the opening is in a second region of the stack that does not include the groups of semiconductor structures. A material can be formed in the second segment so that the first segment terminates at the material. In some instances, the material can be implanted in the dielectrics in the second region through the second segment.