DRAM Capacitor Lower Electrode Stress Mitigation
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Solution Overview
Problem
The increase in capacitance value in DRAM capacitors, achieved by stacking electrodes, leads to thermal and mechanical stresses that cause strain differences between the surface and interior of the electrode, potentially deteriorating the capacitor structure due to the narrowing gap between cells.
Innovation Solution
Incorporating a ductile supporter within the trench of the lower electrode, made of materials like Ti0.5W0.5N or carbon nanotubes, to mitigate stress and prevent physical deterioration, while maintaining the capacitance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the height of the stack type storage structure is increased to increase capacitance, then the cell capacitance increases, but the aspect ratio between lower length and height increases and thermal and mechanical stresses cause strain differences leading to electrode deterioration
Solution Approach 1:
The lower electrode is divided into two functional parts: a brittle material portion providing electrical conductivity and a ductile material portion providing mechanical support. This segmentation allows each part to fulfill its specific function without compromising the other, resolving the contradiction between achieving high capacitance through increased height and maintaining electrode structural integrity under stress.
Solution Approach 2:
The lower electrode uses a composite structure combining brittle and ductile materials. The brittle material (e.g., TiN, TaN) provides excellent electrical conductivity for high capacitance, while the ductile material (e.g., tungsten, molybdenum) provides mechanical strength to withstand thermal and mechanical stresses, thereby maintaining reliability in tall capacitor structures.
2Quantity of substance
If the height of the stack type storage structure is increased to increase capacitance, then the cell capacitance increases, but the gap between cells is narrowed making manufacturing more difficult
Solution Approach 1:
By segmenting the lower electrode into brittle and ductile material portions, the structure gains mechanical stability that facilitates precise gap control between adjacent cells during manufacturing, even as capacitor height increases for higher capacitance.
Solution Approach 2:
The invention changes the material parameter (ductility) of part of the lower electrode, which alters the mechanical behavior during fabrication processes. This enables better control over cell spacing and gap dimensions while maintaining the increased capacitor height needed for high capacitance.
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 ductile supporter effectively cushions lateral stress, preventing the lower electrode from collapsing and enhancing the reliability of the semiconductor device by maintaining structural integrity under thermal and mechanical loads.
Implementation Method 1
the ductile supporter effectively cushions lateral stress, preventing the lower electrode from collapsing and enhancing the reliability of the semiconductor device by maintaining structural integrity under thermal and mechanical loads
Data Source
AI summary
Provided is a semiconductor device and a method for fabricating the same. The semiconductor device includes an interlayer insulating layer formed on a semiconductor substrate, a metal contact plug penetrating the interlayer insulating layer, a cylindrical lower electrode formed on the metal contact plug and including a first metal and a trench, a supporter formed in the trench and including a second metal that is different from the first metal, a dielectric layer formed on the lower electrode and the supporter and an upper electrode formed on the dielectric layer.