Multilayer DRAM Lower Electrode Structure for Leakage Control
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Solution Overview
Problem
As semiconductor devices become increasingly integrated, the challenge lies in enhancing charge storage capacity and reducing leakage characteristics in DRAM structures, particularly in maintaining the integrity of lower electrodes to prevent inclination and contact with adjacent electrodes.
Innovation Solution
The semiconductor device incorporates a lower electrode with multiple layers, including a first layer, a second layer, and a third layer, where each layer has a distinct material, and the third layer's sidewall is concave and spaced apart, allowing for adjusted heights to prevent the inner layer from being etched and the outer layer from inclining, thus maintaining separation between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the lower electrode is formed as a single layer, then the manufacturing process is simple, but the outer layer may incline and contact adjacent electrodes during etching of open regions
Solution Approach 1:
The lower electrode is divided into multiple layers (first layer, second layer, and third layer) with different materials and functions. The first layer contacts the substrate, the second layer is positioned between the first and third layers, and the third layer forms the outer surface. This segmentation prevents the outer layer from inclining during etching while maintaining manufacturing feasibility through standardized multi-layer deposition processes.
Solution Approach 2:
The lower electrode employs composite material structure where each layer is made of different materials optimized for its specific function. The first layer uses a material with high adhesion to the substrate, the second layer provides structural support, and the third layer uses a material with appropriate etching characteristics. This composite approach prevents inclination of the outer layer during etching while maintaining ease of manufacture through established material systems.
2Stability of the object's composition
If the lower electrode height is increased to prevent inclination, then the outer layer remains stable, but the charge storage capacity decreases
Solution Approach 1:
By segmenting the electrode into multiple layers, the height of individual layers can be optimized independently. The first layer provides stable contact with the substrate, the second layer maintains structural stability, and the third layer optimizes charge storage capacity. This segmentation allows the outer layer to remain stable without requiring excessive overall height, thereby preserving charge storage capacity.
Solution Approach 2:
The invention changes the parameter distribution across different layers by assigning different thicknesses and material properties to each layer. The first layer has optimized adhesion properties, the second layer has optimized mechanical strength, and the third layer has optimized charge storage properties. This parameter optimization allows stability to be achieved without compromising charge storage capacity.
3Quantity of substance
If the lower electrode is made wider to increase charge storage, then the charge storage capacity increases, but the leakage current increases due to closer spacing of adjacent electrodes
Solution Approach 1:
The electrode structure is segmented into multiple layers with the third layer forming the outer surface that defines the effective width. By controlling the thickness and material properties of each layer, the effective width can be optimized to maximize charge storage capacity while maintaining appropriate spacing between adjacent electrodes to minimize leakage current.
Solution Approach 2:
The composite material structure allows different layers to serve different functions: the first layer provides stable substrate contact, the second layer provides structural support, and the third layer optimizes both charge storage capacity and leakage characteristics. The material selection for each layer is optimized to achieve the desired balance between width for charge storage and spacing for leakage prevention.
4Manufacturing precision
If the third layer sidewall is made concave to improve alignment, then the electrode alignment improves, but the manufacturing precision requirements increase
Solution Approach 1:
The concave sidewall is implemented only in the third layer, while the first and second layers maintain simple vertical sidewalls. This segmented approach improves alignment precision at the critical outer surface without requiring complex structures throughout the entire electrode. The multi-layer segmentation allows the concave feature to be isolated to where it is most beneficial for alignment.
Solution Approach 2:
The concave sidewall geometry is applied locally to the third layer only, where it provides the most significant alignment improvement. The first and second layers maintain simple cylindrical or rectangular cross-sections. This local application of complexity achieves the desired alignment precision while minimizing overall device complexity.
Data Source
AI summary
A semiconductor device includes a substrate, first and second supporter patterns spaced vertically from the substrate, the second supporter pattern being spaced vertically from the first supporter pattern, a lower electrode hole extending vertically on the substrate, a lower electrode inside the lower electrode hole, contacting a sidewall of the first and second supporter patterns, the lower electrode including a first layer along a portion of a sidewall and bottom surface of the lower electrode hole, a second layer between the first layers, and a third layer on an upper surface of the first and second layers, the first and second layers including a material different from the second layer, and a sidewall of at least a portion of the third layer being concave toward the third layer, overlapping the second layer in the vertical direction, and being spaced apart from the second layer in the vertical direction.