Bit Line Contact Structure with Diffusion Barrier
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Solution Overview
Problem
In DRAM devices, the diffusion of dopants from doped polysilicon bit line contacts into non-doped polysilicon dielectric films leads to increased bit line capacitance and resistance, causing performance issues.
Innovation Solution
A bit line contact structure is implemented using a doped polysilicon film filled in a bit contact hole, with a silicon nitride film and silicon dioxide film double protection layer to prevent dopant diffusion, ensuring minimal dopant migration and maintaining the non-doped polysilicon's conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a doped polysilicon is used as bit line contact and non-doped polysilicon is used as dielectric film, then the bit line contact can be formed with good conductivity, but dopant diffusion occurs from doped polysilicon to non-doped polysilicon causing increased bit line capacitance and resistance
Solution Approach 1:
A liner film (silicon nitride or silicon oxide) is introduced as an intermediary barrier layer between the doped polysilicon bit line contact and the non-doped polysilicon dielectric film. This liner film physically blocks the diffusion path of dopants while allowing the bit line contact to maintain its conductivity function.
Solution Approach 2:
The bit line contact structure is segmented into multiple functional layers: the doped polysilicon contact region, the liner film barrier region, and the non-doped polysilicon dielectric region. This segmentation isolates the dopant source from the victim region while preserving electrical connectivity where needed.
2Object-affected harmful factors
If dopant diffusion is prevented by adding protection layers, then bit line capacitance and resistance are maintained at low values, but the manufacturing process becomes more complex
Solution Approach 1:
The liner film serves as a thin intermediary barrier that adds minimal structural complexity while effectively preventing dopant diffusion. Compared to thick barrier layers or complex patterning schemes, the liner film approach adds only a single thin-film deposition step.
Solution Approach 2:
The solution changes the material parameter of the interface between doped and non-doped polysilicon by introducing a liner film with different chemical composition (silicon nitride or silicon oxide). This parameter change creates a diffusion barrier without significantly altering the overall device geometry or requiring additional processing steps.
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 solution effectively prevents dopant diffusion, maintaining low bit line capacitance and resistance, thereby enhancing the performance and reliability of DRAM devices.
Implementation Method 1
A bit line contact structure is implemented using a doped polysilicon film filled in a bit contact hole, with a silicon nitride film and silicon dioxide film double protection layer to prevent dopant diffusion
Data Source
AI summary
Disclosed herein is a method that includes: forming a composite layer, the composite layer comprising first and second insulative materials and a first polysilicon layer that is between the first and second insulative materials, forming a hole in the composite layer, the hole penetrating through the composite layer to define respective edge portions of the first and second insulative materials and the first polysilicon layer, and converting the edge portion of the first polysilicon layer into third insulative material so that the third insulative material is between the respective edges of the first and second insulative materials.