Flash Memory Stack Structure Using Metal Silicides Against Oxidation
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Solution Overview
Problem
Conventional semiconductor memory devices with tungsten metal layers require additional barrier and protection layers to prevent oxidation, increasing process complexity and reducing yield due to tungsten's reactivity at high temperatures.
Innovation Solution
Replacing tungsten with metal silicides, such as titanium silicide or cobalt silicide, which have similar conductivity and thermal budget tolerance but are less reactive, eliminating the need for barrier and protection layers and simplifying the stack structure and fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If tungsten is used in the film stack, then the thermal budget tolerance is improved, but the device complexity increases due to the need for barrier and protection layers
Solution Approach 1:
The patent extracts and removes the barrier layers and protection layers from the film stack structure by replacing tungsten with metal silicide. This elimination of unnecessary layers directly reduces device complexity while preserving the thermal budget tolerance needed for high-temperature processing.
Solution Approach 2:
The patent changes the material parameter from tungsten to metal silicide, which fundamentally alters the oxidation resistance characteristics. This parameter change allows the structure to maintain thermal budget tolerance without requiring additional protective layers, thereby simplifying the overall film stack.
2Object-affected harmful factors
If barrier layers and protection layers are added to protect tungsten, then the oxidation resistance is improved, but the manufacturing precision decreases due to increased process complexity
Solution Approach 1:
The patent removes the barrier layers and protection layers from the structure by substituting tungsten with metal silicide. This extraction eliminates the need for complex deposition and etching processes associated with these layers, thereby improving manufacturing precision through reduced process variability.
Solution Approach 2:
The patent employs metal silicide, which inherently provides oxidation resistance without requiring additional protective layers. This material substitution eliminates the need for complex multi-layer structures, simplifying the manufacturing process and improving precision by reducing the number of process steps.
3Quantity of substance
If tungsten layers are used, then the conductivity is improved, but the loss of substance increases due to tungsten oxidation
Solution Approach 1:
The patent converts the potential harm of oxidation into a benefit by using metal silicide, which forms a stable, self-protecting oxide layer. This transformation eliminates continuous tungsten oxidation and material loss, improving material utilization efficiency while maintaining electrical conductivity.
Solution Approach 2:
The patent changes the material composition from tungsten to metal silicide, which fundamentally alters the oxidation behavior. This parameter change reduces material loss by preventing uncontrolled oxidation, thereby improving the quantity of functional material retained in the device.
4Object-affected harmful factors
If additional barrier and protection layers are implemented, then the oxidation protection is improved, but the productivity decreases due to increased process steps
Solution Approach 1:
The patent extracts and eliminates the barrier layers and protection layers by replacing tungsten with metal silicide. This removal of unnecessary layers reduces the number of fabrication steps, directly improving manufacturing efficiency and productivity.
Solution Approach 2:
The patent merges the functions of conductivity, thermal budget tolerance, and oxidation resistance into a single metal silicide layer. This consolidation eliminates the need for separate barrier and protection layers, reducing process steps and enhancing productivity.
Data Source
AI summary
Memory devices and methods of forming the same are provided. A memory device of the present disclosure includes a bottom dielectric layer, a gate structure extending vertically from the bottom dielectric layer, a stack structure, and a dielectric layer extending between the gate structure and the stack structure. The stack structure includes a first silicide layer, a second silicide layer, an oxide layer extending between the first and second silicide layers, a channel region over the oxide layer and extending between the first and second silicide layers, and an isolation layer over the second silicide layer. The first and second silicide layers include cobalt, titanium, tungsten, or palladium.