Cobalt Conductive Layers for 3D Memory Stress Reduction
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Solution Overview
Problem
Three-dimensional memory devices face challenges with high tensile stress generated by tungsten, leading to device warpage, and require thicker metallic barrier layers for deposition, which increases resistance and complexity.
Innovation Solution
The use of cobalt as a softer metal with thinner metallic barrier layers, deposited using precursor gases like bis(cyclopentadienyl)cobalt, reduces resistance and stress, enabling efficient formation of electrically conductive layers within three-dimensional memory structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten is used for conductive layers, then electrical conductivity is maintained, but high tensile stress causes device warpage
Solution Approach 1:
The patent changes the material parameter from tungsten to cobalt, which fundamentally alters the stress characteristics while maintaining electrical conductivity. Cobalt exhibits lower tensile stress compared to tungsten, thereby resolving the warpage issue while preserving the electrical performance required for memory device operation.
2Reliability
If tungsten is used, then comparable resistivity is achieved, but thicker metallic barrier layers are required increasing resistance and complexity
Solution Approach 1:
The patent changes the conductive material parameter from tungsten to cobalt, which enables the use of thinner metallic barrier layers. This parameter change reduces both the barrier layer thickness and the overall resistance, simplifying the device structure while maintaining comparable resistivity for effective memory operation.
3Stress or pressure
If cobalt is used instead of tungsten, then stress and barrier layer thickness are reduced, but deposition process complexity increases
Solution Approach 1:
The patent replaces the conventional physical vapor deposition method with chemical vapor deposition using organometallic precursor gases. This substitution enables cobalt deposition through chemical reactions rather than physical processes, achieving the desired stress reduction and thinner barrier layers while maintaining manufacturability through well-established CVD techniques.
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 deposition allows for a metal interconnect structure with lesser resistance and reduced stress, improving the fabrication of three-dimensional memory devices by using thinner barrier layers and maintaining comparable resistivity to tungsten.
Implementation Method 1
Each of the electrically conductive layers is formed by depositing at least a cobalt portion within a respective backside recess
Data Source
AI summary
A memory film and a semiconductor channel can be formed within each memory opening that extends through a stack including an alternating plurality of insulator layers and sacrificial material layers. After formation of backside recesses through removal of the sacrificial material layers selective to the insulator layers, a metallic barrier material portion can be formed in each backside recess. A cobalt portion can be formed in each backside recess. Each backside recess can be filled with a cobalt portion alone, or can be filled with a combination of a cobalt portion and a metallic material portion including a material other than cobalt.