Inverted Ferroelectric Pillar Capacitors for Higher DRAM Density
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Solution Overview
Problem
Existing pillar-type capacitors in DRAMs and embedded DRAMs face challenges in achieving high capacitance density due to their non-inverted structure, which requires additional dielectric isolation between adjacent capacitors, limiting their packing density.
Innovation Solution
The development of inverted pillar capacitors with a ferroelectric or antiferroelectric insulating layer, where the U-shaped capacitors open toward the substrate, eliminating the need for dielectric isolation between bottom electrodes and using shared top electrodes and insulating layers to isolate adjacent capacitors, thereby reducing the area required for each capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If non-inverted pillar capacitors are used, then the capacitor structure is simple to manufacture, but the capacitance density is limited due to required dielectric isolation between adjacent capacitors
Solution Approach 1:
The patent inverts the traditional capacitor structure by opening the U-shaped capacitor toward the substrate instead of away from it. This inversion eliminates the need for dielectric isolation between bottom electrodes of adjacent capacitors, as the bottom electrodes are now isolated by the shared top electrode and insulating layers. The inversion principle directly resolves the technical contradiction by enabling higher capacitance density without significantly complicating the manufacturing process.
Solution Approach 2:
The patent merges the isolation function into the shared top electrode structure. Instead of requiring separate dielectric isolation layers between adjacent capacitors, the top electrode and insulating layers serve dual purposes: they provide the capacitive function and simultaneously isolate adjacent bottom electrodes. This merging of functions reduces the area required for each capacitor while maintaining manufacturing simplicity.
2Reliability
If dielectric isolation is used between adjacent capacitors, then electrical isolation is achieved, but the area required for each capacitor increases
Solution Approach 1:
The top electrode and insulating layers perform multiple functions simultaneously: they form the capacitive structure and provide electrical isolation between adjacent bottom electrodes. This multi-functionality eliminates the need for additional dedicated isolation structures, reducing the total area required for each capacitor while maintaining reliable electrical isolation.
Solution Approach 2:
By inverting the capacitor structure, the isolation mechanism is reversed from the traditional approach. Instead of isolating bottom electrodes with dielectric material, the isolation is achieved through the shared top electrode structure, which naturally separates adjacent capacitors. This inversion reduces the required capacitor area while maintaining electrical isolation reliability.
3Ease of manufacture
If traditional pillar capacitor structure is used, then manufacturing process is straightforward, but packing density is limited
Solution Approach 1:
The inverted structure maintains manufacturing straightforwardness by using similar deposition and etching processes, while the geometric inversion enables higher packing density. The U-shaped capacitor opening toward the substrate allows adjacent capacitors to share top electrodes and insulating layers, reducing the pitch between capacitors and increasing the number of capacitors per unit area.
Solution Approach 2:
The patent utilizes the vertical dimension more effectively by inverting the capacitor orientation. This dimensional change allows the capacitors to pack more densely in the horizontal plane, as the isolation function is transferred to the shared top electrode structure rather than requiring horizontal separation. The result is higher packing density without significantly complicating the manufacturing process.
Data Source
AI summary
Inverted pillar capacitors that have a U-shaped insulating layer are oriented with the U-shaped opening of the insulating layer opening toward the surface of the substrate on which the inverted pillar capacitors are formed. The bottom electrodes of adjacent inverted pillar capacitors are isolated from each other by the insulating layers of the adjacent electrodes and the top electrode that fills the volume between the electrodes. By avoiding the need to isolate adjacent bottom electrodes by an isolation dielectric region, inverted pillar capacitors can provide for a greater capacitor density relative to non-inverted pillar capacitors. The insulating layer in inverted pillar capacitors can comprise a ferroelectric material or an antiferroelectric material. The inverted pillar capacitor can be used in memory circuits (e.g., DRAMs) or non-memory applications.