3D Memory Backside Contact Via Structure With Tapered Nitride Liner
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in effectively forming composite backside metal fill structures that ensure reliable electrical connectivity and structural integrity, particularly in the context of three-dimensional vertical NAND strings with one bit per cell.
Innovation Solution
The formation of a three-dimensional memory device involves creating a backside trench fill structure with a backside trench insulating spacer and a backside contact via structure, comprising a first metal layer, a metallic nitride liner, and a core fill conductive material, which includes a tapered metallic nitride liner to enhance electrical connectivity and structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple metal fill structure is used in the backside trench, then the manufacturing process is simpler, but the electrical conductivity and structural integrity are insufficient
Solution Approach 1:
The patent applies composite materials by creating a multi-layer backside contact via structure comprising a metallic nitride liner layer and a metal fill layer. This composite structure provides both the electrical conductivity needed for reliable connectivity and the structural integrity required for mechanical stability, resolving the contradiction between simple structure and reliable electrical connection.
Solution Approach 2:
The backside contact via structure is segmented into multiple functional layers: a metallic nitride liner layer for adhesion and barrier functions, and a metal fill layer for electrical conductivity. This segmentation allows each layer to optimize its specific function while collectively achieving reliable electrical connectivity without excessive overall complexity.
2Reliability
If a uniform metallic nitride liner is deposited in the backside trench, then the deposition process is simpler, but the electrical connectivity at different depths is non-uniform
Solution Approach 1:
The patent implements local quality by creating a tapered metallic nitride liner where the liner thickness varies with depth in the backside trench. The liner is thicker at deeper levels and thinner at upper levels, optimizing electrical connectivity and adhesion at each depth zone. This non-uniform local structure resolves the contradiction between simple uniform deposition and effective electrical connectivity.
3Reliability
If the metal fill layer extends to the top surface, then the electrical connectivity is maximized, but the structural integrity and stress control are compromised
Solution Approach 1:
The metal fill layer is configured with local quality by extending to the top surface only in specific regions rather than uniformly across the entire backside trench. This selective extension maximizes electrical connectivity where needed while maintaining structural integrity in other regions, resolving the contradiction between maximized connectivity and maintained strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the electrical conductivity and structural integrity of the memory device by providing a robust backside trench fill structure, ensuring reliable contact and improved performance of the memory elements.
Implementation Method 1
nitriding the first metal layer to form a second metallic nitride liner
Data Source
AI summary
A three dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers located over a substrate; memory stack structures vertically extending through the alternating stack; and a backside trench fill structure. The backside trench fill structure includes a backside trench insulating spacer and a backside contact via structure. The backside contact via structure may include a tapered metallic nitride liner and at least one core fill conductive material portion. Alternatively, the backside contact via structure may include a tungsten nitride liner, a metallic nitride liner other than tungsten nitride, and at least one core fill conductive material portion.