DRAM Capacitor Structure With Common Top Cell Plate
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Solution Overview
Problem
The challenge in dynamic random access memory (DRAM) devices is to maintain sufficient storage node capacitance while increasing circuit density, as scaling down integrated circuits requires larger capacitor cell plates to counter parasitic capacitance and noise, which is difficult to achieve with traditional two-transistor memory cells.
Innovation Solution
A capacitor structure with a pair of electrically separated electrodes sharing a common top cell plate is developed, formed through specific fabrication steps involving patterned photoresist, hemispherical grain silicon formation, and planarization to create individual storage node electrodes and a common top cell plate, enhancing capacitance without increasing die size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional two-transistor memory cell structures are used, then circuit density can be increased, but storage node capacitance becomes insufficient due to parasitic capacitance and noise
Solution Approach 1:
The capacitor structure is divided into multiple electrodes (first electrode, second electrode, third electrode, fourth electrode) arranged in a stacked configuration. This segmentation allows each electrode to contribute to the overall capacitance, enabling sufficient storage node capacitance to be achieved within a compact footprint that supports high circuit density.
2Reliability
If capacitor cell plates are made larger to maintain sufficient capacitance, then storage node capacitance is improved, but circuit density decreases
Solution Approach 1:
The capacitor structure transitions from a planar configuration to a three-dimensional stacked configuration with multiple electrodes arranged vertically. This dimensional change allows the capacitor to achieve sufficient capacitance without increasing the lateral footprint, thereby maintaining high circuit density while meeting capacitance requirements.
3Quantity of substance
If more memory cells are packed into the same die size, then circuit density increases, but charge storage capability per cell is reduced
Solution Approach 1:
The capacitor electrodes are nested in a stacked configuration where multiple electrodes are arranged in layers (first electrode with second electrode, third electrode with fourth electrode). This nesting allows maximum utilization of vertical space, enabling sufficient capacitance to be achieved within a compact cell area that supports high memory cell density.
Data Source
AI summary
A capacitor structure for a semiconductor assembly and a method for forming same are described. The capacitor structure comprises a pair of electrically separated capacitor electrodes and a capacitor electrode being common to only the pair of electrically separated capacitor electrodes.