Composite Dielectric Capacitor Structure for Lower DRAM Leakage
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Solution Overview
Problem
Capacitor structures in DRAMs experience significant leakage current due to electron migration, which affects their performance.
Innovation Solution
A dielectric layer is formed with a first amorphous layer that maintains an amorphous structure after annealing, and a high dielectric constant layer is formed by crystallizing an initial dielectric constant layer, reducing electron transport and enhancing dielectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional dielectric layer is used in the capacitor structure, then the dielectric constant can be maintained, but electron migration occurs causing large leakage current
Solution Approach 1:
The dielectric layer is constructed as a composite structure with a first amorphous layer (hafnium silicate or aluminum titanate) and a high dielectric constant layer (crystallized initial dielectric constant layer). This composite structure combines the electron-blocking properties of amorphous materials with the high dielectric constant of crystalline materials, thereby reducing leakage current while maintaining capacitance performance.
Solution Approach 2:
Different regions of the dielectric layer are assigned different functions: the first amorphous layer in contact with the electrode serves to block electron migration and reduce leakage, while the high dielectric constant layer provides the necessary capacitance. This local differentiation of material properties optimizes both leakage current and dielectric performance.
2Reliability
If the dielectric layer is annealed to improve dielectric properties, then crystallization can occur increasing dielectric constant, but electron migration increases causing larger leakage current
Solution Approach 1:
The dielectric layer is segmented into two distinct layers with different crystallographic structures and functions. The first amorphous layer remains amorphous after annealing to block electron migration, while the initial dielectric constant layer is crystallized to provide high dielectric constant. This segmentation allows each layer to undergo appropriate thermal treatment without compromising the other's function.
Solution Approach 2:
The material composition parameters are optimized to achieve differential response to annealing. The first amorphous layer is composed of hafnium silicate or aluminum titanate with specific composition ratios that maintain amorphous structure after annealing, while the initial dielectric constant layer is formulated to crystallize upon annealing, thereby achieving opposite structural changes under the same thermal conditions.
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 method reduces leakage current and improves the performance of the capacitor structure by inhibiting electron migration and increasing dielectric constant.
Implementation Method 1
the first amorphous layer maintaining an amorphous structure after annealing
Implementation Method 2
the high dielectric constant layer being formed by crystallizing an initial dielectric constant layer after annealing
Implementation Method 3
electron migration is unlikely to occur in an amorphous structure, therefore the first amorphous layer can inhibit electron transport
Data Source
AI summary
A preparation method for the capacitor structure includes: forming a dielectric layer on a first electrode, wherein, the dielectric layer includes a first amorphous layer and a high dielectric constant layer which are stacked, the first amorphous layer maintaining an amorphous structure after annealing, and the high dielectric constant layer being formed by crystallizing an initial dielectric constant layer after annealing; and forming a second electrode on the dielectric layer. Since the first amorphous layer remains an amorphous structure after annealing, electron transport can be suppressed, thereby reducing the leakage current of the capacitor structure.