DRAM Isolation Structure With Shielding Layer Against Word Line Leakage
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Solution Overview
Problem
The increasing reduction of feature dimension in DRAM devices leads to smaller distances between word lines, causing leakage that affects nearby memory cells and results in information loss and reduced product yields due to continuous access of the same word line address.
Innovation Solution
A semiconductor structure is developed with a shielding layer located in the isolation structure, which shields the electric field at the bottom of the word line, reducing electron adsorption and inhibiting leakage path formation, thereby alleviating leakage and maintaining memory cell integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the distance between word lines is reduced to increase memory density, then the layout area is reduced, but leakage occurs affecting nearby memory cells
Solution Approach 1:
A shielding layer is introduced as an intermediary component between adjacent word lines. This shielding layer, positioned within the isolation structure, acts as a mediator that blocks the harmful electric field interaction between word lines, preventing leakage while allowing the word lines to remain in close proximity for high density.
Solution Approach 2:
The shielding layer is selectively positioned only in specific regions where leakage problems occur, namely within the isolation structure between word lines. This localized approach addresses the harmful interaction only where needed, without affecting the overall high-density layout or requiring changes to the entire word line structure.
2Speed
If word line switching is performed continuously to access memory, then data access speed is improved, but leakage causes information loss in nearby memory cells
Solution Approach 1:
The shielding layer serves as a protective intermediary that prevents the electric field from switching word lines from coupling into nearby memory cells. This allows continuous word line switching for fast access without the harmful side effect of information loss in adjacent cells.
Solution Approach 2:
The shielding layer is pre-positioned in the isolation structure before word line switching operations occur. This preliminary protective structure prevents the harmful coupling effect before it can occur, allowing aggressive switching sequences without information loss.
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 shielding layer effectively prevents leakage and information loss in memory cells, enhancing product yields by reducing electron adsorption and maintaining the integrity of memory cells during word line switching.
Implementation Method 1
a shielding layer located in the isolation layer, wherein the word line structures are located above the shielding layer
Data Source
AI summary
A semiconductor structure includes a substrate and word line structures. An isolation structure is formed in the substrate, and the isolation structure defines active areas in the substrate. The isolation structure includes a trench formed in the substrate, an isolation layer filled in the trench, and a shielding layer located in the isolation layer. The word line structures are located in the substrate, pass through the isolation structure and the active areas, and are located above the shielding layer.