Gate Stack WSix WSiN Hybrid Structure Crack Mitigation
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Solution Overview
Problem
Gate stacks with tungsten silicide (WSix) material suffer from cracking due to volume shrinkage and tensile stress during thermal treatment, affecting the reliability of the gate structure, especially in areas with topography.
Innovation Solution
A hybrid WSix/WSiN stack structure is introduced, where a tungsten silicon nitride (WSiN) layer acts as a stress stabilization layer and crack propagation barrier, deposited on top of the WSix material to mitigate cracking, and can be further enhanced with additional WSix layers, stabilizing the structure and preventing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a tungsten silicide (WSix) material tier is deposited to fill topography variations in gate stacks, then the gate structure can accommodate topography and maintain planarity, but the WSix material develops cracking due to volume shrinkage and tensile stress during thermal treatment
Solution Approach 1:
The gate stack is segmented into multiple material tiers: a first WSix material tier deposited conformally on the gate structure, and a second WSix material tier deposited to fill topography variations. This segmentation allows each layer to serve specific functions - the first layer provides stress management while the second layer achieves planarity, preventing cracking in the overall structure.
Solution Approach 2:
Different regions of the gate stack receive different material treatments tailored to local requirements. The conformal WSix layer is applied in areas requiring stress control, while additional WSix material is deposited specifically in regions with topography variations needing planarity correction. This localized approach optimizes both crack prevention and surface flatness.
2Stability of the object's composition
If thermal treatment is applied to the gate stack, then the WSix material undergoes volume shrinkage and stress relief, but this process induces cracking in the WSix material tier
Solution Approach 1:
A cap layer is deposited beforehand on the WSix material tier before thermal treatment. This cap layer acts as a cushion that prevents crack formation during the thermal treatment process by accommodating volume shrinkage and stress relief, thereby protecting the WSix material from cracking while still allowing necessary stress relaxation.
Solution Approach 2:
The gate stack employs a composite structure combining WSix material with a cap layer material that has complementary properties. The cap layer material is selected to have appropriate mechanical and thermal characteristics that complement the WSix, creating a composite system where the cap layer protects the WSix from thermal-induced cracking while allowing stress relief.
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
The hybrid WSix/WSiN stack structure significantly reduces crack formation and propagation, achieving a crack-free gate stack that maintains reliability even under thermal treatment, suitable for use in advanced memory technologies like 3D NAND flash memory.
Implementation Method 1
a tungsten silicon nitride (WSiN) layer acts as a stress stabilization layer and crack propagation barrier, deposited on top of the WSix material
Data Source
AI summary
Some embodiments disclose a gate stack having a gate (e.g., polysilicon (poly) material) horizontally between shallow trench isolations (STIs), a tungsten silicide (WSix) material over the gate and the STIs, and a tungsten silicon nitride (WSiN) material on a top surface of the WSix material. Some embodiments disclose a gate stack having a gate between STIs, a first WSix material over the gate and the STIs, a WSiN interlayer material on a top surface of the first WSix material, and a second WSix material on a top surface of the WSiN interlayer material. Additional embodiments are disclosed.