Island-Shaped Bit Line Junctions Reduce Coupling Capacitance
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Solution Overview
Problem
As semiconductor devices become more integrated, the reduction of transistor channel lengths leads to short channel effects, and the formation of vertical channel transistors increases coupling capacitance between bit lines, causing noise and improper data reading due to adjacent bit line activation.
Innovation Solution
The semiconductor device incorporates buried bit lines with island-shaped bit line junction regions, connected through one side contacts, and a capping layer, which reduces coupling capacitance by separating bit line junction regions and using materials like titanium nitride, polysilicon, or cobalt layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vertical channel transistor structure is formed to achieve smaller device dimensions, then device integration density is improved, but coupling capacitance between bit lines increases causing noise and improper data reading
Solution Approach 1:
The bit line junction region is divided into multiple separated island-shaped regions instead of a continuous structure. These island regions are spatially segmented and isolated from each other, reducing the overlapping area with adjacent bit lines and thereby decreasing coupling capacitance while maintaining connection to the buried bit line through one-side contacts
Solution Approach 2:
The bit line junction region transitions from a planar two-dimensional structure to a three-dimensional island structure with vertical extent. By forming islands at different depths and positions, the structure utilizes the third dimension to reduce lateral overlap with adjacent bit lines, effectively reducing coupling capacitance
2Productivity
If channel length is reduced to increase integration density, then device size is improved, but short channel effects such as DIBL, hot carrier effect, and punch-through occur
Solution Approach 1:
The transistor structure transitions from planar to vertical channel configuration. The channel extends vertically through the substrate rather than horizontally at the surface, allowing shorter lateral dimensions for higher density while maintaining adequate vertical channel length to suppress short channel effects
3Ease of operation
If buried bit line is activated to read data, then data access is enabled, but adjacent buried bit line may also be activated causing noise in sense amplifier
Solution Approach 1:
The bit line junction region is segmented into isolated island regions that are selectively connected to specific buried bit lines. This segmentation ensures that when one buried bit line is activated, only its corresponding island regions are affected, preventing capacitive coupling from activating adjacent bit lines and reducing noise in the sense amplifier
Data Source
AI summary
A technology is a semiconductor cell and a semiconductor device capable of reducing the coupling capacitance between adjacent bit lines by forming a bit line junction region in a separated island shape when forming a buried bit line, thereby improving characteristics of the semiconductor devices. The semiconductor cell includes a transistor including a gate and a gate junction region, a plurality of buried bit lines disposed to intersect the gate, and a plurality of bit line junction regions, each bit line junction region having an island shape formed between the buried bit lines and connected to the buried bit line.