Dielectric-Metal Stack for 3D Flash Memory
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Solution Overview
Problem
Current methods for forming 3D memory stacks face challenges such as polysilicon recess, silicidation, wet stripping of metals, nitride removal, and defect control, as well as conformal deposition of metals and metallic compounds, which hinder the development of efficient and reliable memory structures.
Innovation Solution
A method involving a sequence of forming dielectric, metallic, and metallic nitride adhesion layers using chemical vapor deposition or atomic layer deposition in a processing chamber, with specific gas mixtures and plasma enhancements, to create a stack of film layers for 3D memory devices, allowing for improved layer adhesion and integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polysilicon is used as conductive material for control gate, then the memory structure can be formed, but polysilicon recess and silicidation problems occur
Solution Approach 1:
The patent replaces polysilicon with metal materials (such as tungsten, cobalt, or copper) that can be deposited as thin films and selectively removed where not needed. This allows the use of a material that is easier to deposit but requires selective removal processes, effectively treating the metal as a temporary structure that is later disposed of in specific areas to avoid polysilicon-related defects.
Solution Approach 2:
The patent changes the material parameter from polysilicon to metal, and adjusts deposition parameters (using atomic layer deposition or chemical vapor deposition) to control film thickness and properties. This parameter change enables avoidance of polysilicon recess and silicidation while maintaining control gate functionality through alternative material properties.
2Reliability
If silicon nitride is used as charge trapping layer, then charge trapping function is achieved, but nitride removal with defect control becomes difficult
Solution Approach 1:
The patent segments the charge trapping function into multiple thin layers (such as multiple oxide layers or combinations of oxide and nitride layers) rather than using a single thick silicon nitride layer. This segmentation allows for easier removal or modification of individual layers while maintaining the overall charge trapping functionality through the collective effect of multiple layers.
Solution Approach 2:
The patent uses composite material structures combining different dielectric materials (oxides, nitrides, oxynitrides) in specific sequences and thicknesses to achieve charge trapping functionality. This composite approach allows optimization of both charge trapping performance and ease of removal, as different materials in the composite can be selectively removed or modified based on their individual properties.
3Reliability
If metals or metallic compounds are deposited in holes or channels, then charge storage is enabled, but conformal deposition presents challenges
Solution Approach 1:
The patent replaces traditional physical deposition methods with atomic layer deposition (ALD) or chemical vapor deposition (CVD) processes that use chemical reactions to deposit conformal metal or metallic compound layers. This substitution of deposition mechanism enables atomic-level control and uniform coverage on complex 3D structures, achieving conformal deposition that maintains charge storage functionality while eliminating deposition challenges.
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
This approach enhances process integration and layer adhesion, facilitating the formation of efficient 3D memory stacks with improved reliability and reduced defects, enabling the creation of smaller geometries with increased capacity at lower costs.
Implementation Method 1
forming a dielectric layer on the substrate, supplying one or more process gases suitable for forming a metallic layer into the processing chamber of the deposition reactor, forming a metallic layer on the dielectric layer
Implementation Method 2
forming a dielectric, metallic, and metallic nitride adhesion layers using chemical vapor deposition or atomic layer deposition in a processing chamber
Implementation Method 3
with specific gas mixtures and plasma enhancements, to create a stack of film layers for 3D memory devices
Data Source
AI summary
A method is provided for forming a stack of film layers for use in 3D memory devices. The method starts with providing a substrate in a processing chamber of a deposition reactor. Then one or more process gases suitable for forming a dielectric layer are supplied into the processing chamber of the deposition reactor forming a dielectric layer on the substrate. Then one or more process gases suitable for forming a metallic layer are supplied into the processing chamber of the deposition reactor forming a metallic layer on the dielectric layer. Then one or more process gases suitable for forming a metallic nitride adhesion layer are supplied into the processing chamber of the deposition reactor forming a metallic nitride adhesion layer on the metallic layer. The sequence is then repeated to form a desired number of layers.