Cobalt Multilayer Word Lines for 3D Memory Warpage Reduction
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Solution Overview
Problem
Current three-dimensional memory devices face challenges with high tensile stress generated by tungsten, leading to device warpage, and require thicker metallic barrier layers, which can increase resistance and complexity in metal interconnects.
Innovation Solution
The use of cobalt as a softer metal with a thinner metallic barrier layer, deposited using precursor gases like bis(cyclopentadienyl)cobalt, to form electrically conductive layers with reduced resistance and stress, allowing for more efficient and scalable three-dimensional memory device fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tungsten is used as the metallic material in electrically conductive layers, then the device can achieve high strength and stability, but high tensile stress is generated leading to device warpage
Solution Approach 1:
The patent changes the metallic material parameter from tungsten to cobalt, which has different mechanical properties including lower tensile stress. This material substitution resolves the contradiction by maintaining electrical conductivity while reducing the stress that causes warpage, allowing the device to achieve both strength and shape stability.
2Shape
If thicker metallic barrier layers are used in electrically conductive layers, then stress and warpage can be reduced, but resistance increases and device complexity increases
Solution Approach 1:
The patent changes the metallic material parameter to cobalt, which inherently generates less tensile stress than tungsten. This allows the use of thinner metallic barrier layers while still controlling warpage, thereby reducing resistance and simplifying the device structure without compromising shape stability.
3Shape
If cobalt is used as the metallic material instead of tungsten, then stress and warpage are reduced, but the material selection becomes more specific and complex
Solution Approach 1:
The patent specifies cobalt as the metallic material parameter, which has favorable properties including lower tensile stress and compatibility with standard semiconductor fabrication processes. While this is a specific material choice, cobalt is a well-established material in the industry with成熟的 deposition and processing techniques, thereby reducing the actual complexity of implementation despite the specific material requirement.
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
Cobalt-based conductive layers provide comparable resistance to tungsten while reducing stress and warpage, enabling the creation of more reliable and efficient three-dimensional memory devices with improved scalability and performance.
Implementation Method 1
deposited using precursor gases like bis(cyclopentadienyl)cobalt
Data Source
AI summary
A memory stack structure including a memory film and a vertical semiconductor channel can be formed within each memory opening that extends through a stack including an alternating plurality of insulating layers and sacrificial material layers. After formation of backside recesses through removal of the sacrificial material layers selective to the insulating layers, a backside blocking dielectric layer may be formed in the backside recesses and sidewalls of the memory stack structures. A metallic barrier material portion can be formed in each backside recess. A metallic material portion is formed on the metallic barrier material portion. Subsequently, a metal portion comprising a material selected from cobalt and ruthenium is formed directly on a sidewall of the metallic barrier material portion and a sidewall of the metallic material portion and an overlying insulating surface and an underlying insulating surface.