Dummy Bit Line MOS Capacitor for Open Bit Line Structures
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Solution Overview
Problem
In semiconductor devices with an open bit line structure, the presence of dummy cells increases chip size due to unnecessary overhead, as they are not actively used as memory cells and occupy space that could be utilized more efficiently.
Innovation Solution
The dummy cells are repurposed as MOS capacitors by forming a stacked structure of a polysilicon layer and a metal layer, including tungsten, with a dielectric layer such as silicon oxide or high-k materials, to function as capacitors, thereby reducing chip area and improving noise characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If dummy cells are arranged in the outermost memory cell block to maintain open bit line structure, then the memory cell density is maximized, but the chip size increases due to unnecessary overhead from dummy cells that cannot act as memory cells
Solution Approach 1:
The patent applies multi-functionality by enabling dummy cells to serve dual purposes: maintaining the open bit line structure connectivity and functioning as MOS capacitors for noise filtering. This is achieved by forming a capacitor structure within the dummy cell region, including a first electrode (dummy bit line), a dielectric layer, and a second electrode (reference potential line), allowing the same physical structure to fulfill both structural and functional roles.
Solution Approach 2:
The patent converts the harmful effect of dummy cells occupying unnecessary chip area into a beneficial function by transforming them into operational MOS capacitors. The previously wasted dummy cell region now provides noise filtering capability, improving signal integrity while utilizing the same physical space, thus converting a structural necessity into a functional asset.
2Adaptability or versatility
If dummy cells occupy space in the outermost memory cell block, then the open bit line structure is maintained, but the effective chip area is reduced due to overhead from non-functional cells
Solution Approach 1:
The dummy cells maintain compatibility with the open bit line structure while simultaneously providing capacitive functionality. The first electrode connects to the dummy bit line preserving the open bit line architecture, while the capacitor structure formed by the dielectric layer and second electrode provides noise filtering, thus serving multiple functions within the same structural framework.
Solution Approach 2:
The previously non-functional dummy cell space is transformed into a beneficial capacitive element that enhances signal quality. The overhead area that was merely structural now provides active noise filtering functionality, improving the effective utilization of chip area while maintaining structural requirements.
3Area of stationary object
If dummy cells are used as MOS capacitors by forming stacked structure of polysilicon layer and metal layer with dielectric layer, then chip area is reduced and noise characteristics are improved, but device complexity increases
Solution Approach 1:
The capacitor structure uses standard polysilicon and metal layers that are already part of the existing fabrication process, allowing the dummy cells to function as MOS capacitors without requiring entirely new process steps. The dielectric layer is formed between existing conductive layers, integrating the capacitive function into the existing device architecture.
Solution Approach 2:
The existing dummy cell structure and surrounding infrastructure (bit lines, contacts, fabrication layers) are utilized to create the capacitor function without requiring separate dedicated structures. The dummy bit line serves as the first electrode, and the reference potential line serves as the second electrode, allowing the system to serve itself by repurposing existing elements.
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
This approach effectively utilizes the previously unnecessary dummy cell area as MOS capacitors, reducing chip size and enhancing capacitance, thus improving the semiconductor device's performance and efficiency.
Implementation Method 1
a first electrode including a channel region and a storage node contact of a dummy cell; a dielectric layer disposed over a portion of the channel region; and a second electrode disposed over the dielectric layer
Data Source
AI summary
A MOS capacitor, a method of fabricating the same, and a semiconductor device using the same are provided. The MOS capacitor is arranged in an outermost cell block of the semiconductor device employing an open bit line structure. The MOS capacitor includes a first electrode arranged in a semiconductor substrate, a dielectric layer arranged on a semiconductor substrate, and a second electrode arranged on the dielectric layer and including a dummy bit line.