3D Memory Bit Line Stacking to Reduce Capacitance Pitch Limits
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Solution Overview
Problem
As memory devices shrink, the pitch between adjacent bit lines decreases, increasing capacitance and reducing device performance.
Innovation Solution
A three-dimensional memory device is designed with bit lines located in different vertical levels, increasing the effective bit line pitch between laterally adjacent bit lines, and methods are employed to form such a structure by bonding semiconductor dies with vertically offset bit lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If memory devices are shrunk to increase integration density, then device size is reduced, but pitch between adjacent bit lines decreases causing increased capacitance and reduced device performance
Solution Approach 1:
The patent transitions from a planar bit line arrangement to a three-dimensional configuration where bit lines are positioned at different vertical levels (first bit lines at a first vertical level, second bit lines at a second vertical level). This vertical stacking increases the effective pitch between laterally adjacent bit lines, reducing capacitance and improving device performance while maintaining high integration density through the vertical dimension.
2Area of stationary object
If bit lines are positioned closer together to increase integration density, then area utilization is improved, but capacitance between bit lines increases reducing device performance
Solution Approach 1:
The patent utilizes the vertical dimension to separate bit lines into different levels, allowing lateral compression for high area utilization while maintaining adequate vertical spacing to reduce capacitance. The first and second bit lines are positioned at different vertical levels, creating effective pitch separation that reduces capacitive coupling despite close lateral proximity.
3Ease of manufacture
If multiple bit lines are positioned at the same vertical level to simplify manufacturing, then process complexity is reduced, but effective pitch between bit lines is limited reducing device performance
Solution Approach 1:
The patent segments the bit line structure into multiple vertical levels, with first bit lines positioned at a first vertical level and second bit lines positioned at a second vertical level. This segmentation allows each level to be optimized independently while collectively achieving higher effective pitch and reduced capacitance, resolving the trade-off between manufacturing complexity and device performance.
Data Source
AI summary
A semiconductor structure includes a three dimensional memory device containing drain regions having top surfaces in a first horizontal plane, first bit lines electrically connected to a first subset of the drain regions, and second bit lines electrically connected to a second subset of the drain regions. The second bit lines are located above the first bit lines.