Discontinuous Seal Ring Contacts to Reduce 3D Memory Misalignment
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Solution Overview
Problem
The scaling of planar memory cells to smaller sizes faces challenges due to process and fabrication limitations, leading to density constraints and increased costs, while 3D memory architectures introduce new issues with lengthy seal ring structures that cause tilting, stress, and bubble formation during deposition, affecting yield and circuit integrity.
Innovation Solution
Implementing seal ring discontinuous contact structures, such as seal ring via structures with discrete seal ring TSC portions, to reduce tilting and stress issues, and minimize bubble formation by using a discontinuous via process instead of continuous trenches, thereby improving alignment and reducing critical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous trench process is used to form the seal ring body portion, then the seal ring provides complete protection and containment, but the lengthy structure causes tilting issues and stress leading to misalignment and open circuit failures
Solution Approach 1:
The continuous seal ring trench is divided into multiple discrete segments or discontinuous portions. Each segment is formed separately, allowing independent alignment and reducing cumulative tilting errors. The segmentation breaks the lengthy continuous structure into manageable units that are less prone to stress-induced misalignment while maintaining the overall protective function through distributed containment.
2Reliability
If a continuous trench process is used, then the seal ring provides complete protection, but the process results in dishing profiles that accumulate gases and form bubbles isolating contact structures
Solution Approach 1:
The continuous trench is segmented into discrete portions with gaps between them. This segmentation prevents the formation of long continuous dishing profiles that trap gases during annealing. The broken structure allows gas escape paths and eliminates the confined spaces where bubbles would accumulate and isolate contact structures.
Solution Approach 2:
The harmful continuous dishing profile is extracted or eliminated by using discontinuous trench segments. The segmentation removes the condition (continuous length) that enables gas accumulation and bubble formation, thereby extracting the source of the harmful effect while retaining the protective seal ring function.
3Reliability
If the seal ring body portion is made lengthy to provide complete enclosure, then protection is improved, but stress and tilting angles increase causing misalignment
Solution Approach 1:
The lengthy continuous seal ring is divided into multiple shorter discrete segments. Each segment provides localized protection and containment, while the distributed arrangement maintains overall enclosure effectiveness. The segmentation reduces the length of individual structures, thereby reducing stress accumulation and tilting angles in each segment.
Solution Approach 2:
The seal ring protection is transitioned from a single continuous linear structure to a multi-dimensional distributed array of segments. This dimensional change allows the protective function to be achieved through spatial distribution rather than continuous length, reducing the problematic length parameter while maintaining containment effectiveness through geometric arrangement.
Data Source
AI summary
In certain aspects, a semiconductor device includes a first semiconductor layer, a first semiconductor structure formed on the first semiconductor layer including a main chip region, and seal ring discontinuous contact structures formed in a seal ring region enclosing the main chip region. Each seal ring discontinuous contact structure includes a seal ring body portion and a through silicon contact (TSC) portion penetrating through the first semiconductor layer and coupled to the seal ring body portion.