Semiconductor Isolation Structure for Lower Bit Line Capacitance
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Solution Overview
Problem
As dynamic random access memory (DRAM) integration density increases, the reduced spacing between adjacent bit lines in vertical gate-all-around (GAA) transistor structures leads to increased coupling capacitance, negatively impacting the electrical properties of the semiconductor structure.
Innovation Solution
The manufacturing method involves forming third trenches between adjacent initial bit lines, allowing for the creation of gaps in the second isolation layer when it is formed. These gaps reduce parasitic capacitance by utilizing air with a lower dielectric constant, thereby improving the electrical properties of the semiconductor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the spacing between adjacent bit lines is reduced to increase integration density, then the area occupied by each bit line decreases, but the coupling capacitance between adjacent bit lines increases
Solution Approach 1:
An isolation layer is introduced as an intermediary structure between adjacent bit lines. This isolation layer acts as a mediator that reduces the direct electromagnetic coupling between bit lines while maintaining their spatial proximity for high density. The isolation layer material properties can be optimized to provide appropriate dielectric characteristics that minimize coupling capacitance.
Solution Approach 2:
The isolation structure is applied locally between adjacent bit lines rather than uniformly throughout the entire device. This allows the bit lines to maintain close spacing in regions where isolation is not needed, while introducing dielectric material only in specific locations where coupling reduction is required, thereby achieving local optimization of both density and electrical performance.
2Productivity
If the isolation layer size is reduced to accommodate closer bit line spacing, then the integration density increases, but the parasitic capacitance between bit lines increases
Solution Approach 1:
The isolation structure extends into the vertical dimension beneath the bit lines, creating a three-dimensional isolation region. This vertical extension allows the isolation layer to effectively reduce parasitic capacitance without occupying additional lateral space, thereby maintaining high integration density while providing sufficient electrical isolation between adjacent bit lines.
Solution Approach 2:
The isolation structure employs composite material composition, combining different dielectric materials with complementary properties. This allows optimization of both the isolation effectiveness (reducing parasitic capacitance) and the spatial footprint (maintaining high density) by selecting materials with appropriate dielectric constants, breakdown voltages, and physical dimensions.
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 approach effectively reduces parasitic capacitance and minimizes electrical interference between semiconductor pillars connected to different bit lines, enhancing the overall electrical performance and integration density of the semiconductor structure.
Implementation Method 1
The relative dielectric constant of air in the gap is far smaller than that of the second isolation layer, thereby facilitating the reduction of parasitic capacitance between the adjacent initial bit lines
Data Source
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AI summary
Embodiments of the present disclosure provide a semiconductor structure and a manufacturing method thereof, which relate to the field of semiconductors. The method of manufacturing a semiconductor structure includes: providing a base; forming a plurality of first trenches extending along a first direction in the base, the first trenches forming the base into semiconductor layers arranged at intervals, and filling the first trenches with a first isolation layer; forming a plurality of second trenches extending along a second direction in the semiconductor layers and the first isolation layer, to form the semiconductor layers into a plurality of separate semiconductor pillars and initial bit lines located below the semiconductor pillars, a depth of the second trench being smaller than a depth of the first trench; forming third trenches parallel to the first trenches at positions lower than the second trenches, a width of the third trench being greater than a width of the second trench in a direction perpendicular to a side wall of the semiconductor pillar; and filling the second trenches and the third trenches with a second isolation layer, where a part of the second isolation layer in the third trenches has gaps.