Titanium Nitride Source Layer for 3D NAND Memory
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Solution Overview
Problem
Conventional memory devices face challenges in maintaining low source resistance, which increases voltage drop and affects memory operations, especially as memory density increases, due to the use of tungsten silicide layers that have poor adhesion and allow dopant migration.
Innovation Solution
A titanium nitride (TiN) layer is introduced to replace conventional tungsten silicide layers, providing lower resistance, acting as a dopant migration barrier, and improving adhesion with other layers, thus reducing native oxide formation and maintaining lower capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If additional groups of strings of memory cells are added to increase memory density, then memory density is improved, but source resistance increases
Solution Approach 1:
The patent changes the material parameter of the source layer from conventional tungsten silicide to titanium nitride (TiN), which has inherently lower resistivity. This material substitution directly reduces source resistance while allowing continued scaling and density increases, resolving the contradiction between increasing memory density and maintaining low source resistance.
Solution Approach 2:
The patent employs a composite structure where TiN is integrated with doped polysilicon layers. The TiN provides low resistance and adhesion, while the doped polysilicon provides dopant reservoir functionality. This composite approach maintains the dopant migration barrier function while achieving lower overall source resistance, enabling higher density without compromising reliability.
2Ease of manufacture
If conventional tungsten silicide layers are used in the source, then manufacturing process is established, but adhesion is poor and dopant migration occurs
Solution Approach 1:
The TiN layer serves as an intermediary between the doped polysilicon source layer and the underlying substrate or other layers. It provides superior adhesion compared to tungsten silicide and acts as a diffusion barrier to prevent dopant migration into the substrate, while still being compatible with existing manufacturing processes through standard deposition techniques.
Solution Approach 2:
The patent changes the material composition parameter from tungsten silicide to titanium nitride, which fundamentally improves both adhesion properties and dopant migration resistance. This material parameter change maintains compatibility with established manufacturing processes while resolving the reliability issues associated with conventional materials.
3Quantity of substance
If source length is increased to accommodate more memory strings, then memory capacity is improved, but voltage drop increases
Solution Approach 1:
By changing the resistivity parameter of the source material to a lower value through TiN substitution, the patent reduces the voltage drop (I×R loss) that occurs over extended source lengths. This enables the source to span greater distances to accommodate higher density string arrangements without suffering excessive voltage drops that would compromise memory operation reliability.
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 TiN layer achieves lower resistance and capacitance, reduces dopant diffusion, and enhances adhesion, leading to improved memory device performance and increased memory density without voltage drop issues.
Implementation Method 1
acting as a dopant migration barrier, and improving adhesion with other layers
Implementation Method 2
The TiN layer achieves lower resistance and capacitance
Data Source
AI summary
Various embodiments include methods and apparatuses comprising methods for formation of and apparatuses including a source material for electronic devices. One such apparatus includes a vertical string of memory cells comprising a plurality of alternating levels of conductor and dielectric material, a semiconductor material extending through the plurality of alternating levels of conductor material and dielectric material, and a source material coupled to the semiconductor material. The source material includes a titanium nitride layer and a source polysilicon layer in direct contact with the titanium nitride layer. Other methods and apparatuses are disclosed.