Hybrid Source Electrode Contact Via for 3D Memory Warpage Reduction
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently forming contact via structures that minimize substrate warpage and reduce contact resistance, particularly in the formation of monolithic NAND string memory devices with alternating layers of insulating and conductive materials.
Innovation Solution
A method involving the formation of a stack with alternating insulating and sacrificial layers, followed by the creation of memory openings and the deposition of conductive materials, including a doped semiconductor and metallic fill materials, to form a contact via structure within a trench, with a horizontal inner metallic layer spacing the conductive portions, thereby reducing stress and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact via structure is formed in a trench through the stack to reduce contact resistance, then electrical connectivity is improved, but substrate warpage increases due to stress concentration
Solution Approach 1:
The contact via structure is segmented into multiple conductive material portions (first conductive material portion, second conductive material portion, third conductive material portion) separated by dielectric material layers. This segmentation distributes the stress along the vertical axis rather than concentrating it in a single continuous conductive path, thereby reducing substrate warpage while maintaining electrical connectivity.
Solution Approach 2:
The contact via structure uses composite materials consisting of alternating conductive material portions and dielectric material layers. This composite structure provides both electrical connectivity (through the conductive portions) and mechanical stress management (through the dielectric portions that act as stress relief layers), resolving the contradiction between low contact resistance and minimal substrate warpage.
2Adaptability or versatility
If alternating layers of insulating and conductive materials are formed to create monolithic NAND string memory devices, then device functionality is achieved, but structural complexity increases leading to manufacturing difficulties
Solution Approach 1:
The alternating layers are segmented into distinct functional units where conductive material portions serve as memory elements and dielectric material portions serve as isolation and stress management layers. This segmentation allows for systematic fabrication processes and simplifies the manufacturing of complex monolithic NAND string memory devices by breaking down the structure into repeatable units.
Solution Approach 2:
Different regions of the contact via structure have different material compositions tailored to local requirements: conductive material portions provide electrical pathways where needed, while dielectric material portions provide isolation and stress relief in other regions. This local differentiation achieves the required memory device functionality while managing overall structural complexity.
3Stability of the object's composition
If conductive material portions are vertically spaced by dielectric material portions in a contact via structure, then substrate warpage is reduced, but contact resistance increases due to additional interfaces
Solution Approach 1:
The parameters of the conductive material portions (such as their dimensions, composition, or doping levels) are optimized to ensure low contact resistance at each interface, while the dielectric material portions are designed with appropriate thickness and material properties to provide sufficient stress relief. By carefully adjusting these parameters, the structure achieves both warpage reduction and acceptable contact resistance despite the presence of multiple interfaces.
Data Source
AI summary
The metallic material content of a contact via structure for a three-dimensional memory device can be reduced by employing a vertical stack of a doped semiconductor material portion and a metallic fill material portion. A backside contact via can be filled with an outer metallic layer, a lower conductive material portion, an inner metallic layer, and an upper conductive material portion to form a contact via structure such that one of the lower and upper conductive material portions is a doped semiconductor material portion and the other is a metallic fill material portion. The doped semiconductor material generates less stress than the metallic fill material per volume, and thus, the contact via structure can reduce stress applied to surrounding regions in the three-dimensional memory device.