Single Diffusion Break Structure for Compact Transistor Isolation
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Solution Overview
Problem
The semiconductor industry faces challenges in efficiently using precious real estate on semiconductor chips due to the large footprint of dummy transistors required for forming diffusion breaks, leading to waste of space as existing methods do not optimize the separation and isolation of transistors effectively.
Innovation Solution
A semiconductor structure and method that involves forming transistors with a diffusion break between them, where the diffusion break is narrower than the transistor gates, and using a conformal layer and anisotropic etching to create a more efficient separation of source/drain regions, allowing for a smaller footprint and effective isolation without relying on dummy gate locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dummy transistor is used to form a diffusion break, then the separation and isolation of transistors is achieved, but the chip real estate is wasted due to the large footprint of the dummy transistor
Solution Approach 1:
The patent extracts the diffusion break formation from the dummy transistor structure. Instead of using a complete dummy transistor, the invention forms a diffusion break by selectively removing the epitaxial source/drain region and substrate in a targeted manner, isolating only the necessary separation function while eliminating the unnecessary transistor components that waste space.
Solution Approach 2:
The patent segments the diffusion break formation process into distinct steps: forming the conformal layer, selectively removing portions between specific transistors, and creating the diffusion break. This segmentation allows for precise control over where diffusion breaks are formed, enabling space optimization by placing breaks only where needed rather than using entire dummy transistor structures.
2Area of stationary object
If the diffusion break width is reduced to save space, then the chip real estate usage is improved, but the isolation effectiveness may be compromised
Solution Approach 1:
The patent applies local quality by forming conformal layers with specific thicknesses tailored to local requirements. The first conformal layer has a thickness matching the epitaxial source/drain region thickness, while the second conformal layer has a different thickness to achieve the desired diffusion break depth. This localized thickness control ensures effective isolation even with reduced diffusion break width.
Solution Approach 2:
The patent transitions from controlling isolation primarily in the horizontal dimension (diffusion break width) to controlling it in the vertical dimension (diffusion break depth). By using conformal layers of specific thicknesses and selectively removing material to create vertically-defined diffusion breaks, the invention achieves effective isolation with a smaller horizontal footprint, thus saving chip real estate.
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 enables a more efficient use of chip real estate by reducing the footprint of diffusion breaks and optimizing transistor separation, allowing for denser device scaling without increasing the overall size of the chip.
Implementation Method 1
forming a conformal layer between the first and second transistors and between the second and third transistors, the conformal layer fully filling a gap between the first and second transistors and partially filling a gap between the second and third transistors
Implementation Method 2
removing a portion of the conformal layer between the second and third transistors in an anisotropic etching process to expose a portion of the epitaxial source/drain region underneath thereof; removing the exposed portion of the epitaxial source/drain region and a portion of a substrate underneath thereof to create an opening
Data Source
AI summary
Embodiments of present invention provide a semiconductor structure. The semiconductor structure includes a first transistor, a second transistor, and a third transistor separated by their respective source/drain regions; and a diffusion break between the second transistor and the third transistor, wherein a first distance between a center of a gate of the first transistor and a center of a gate of the second transistor is more than half of a second distance between the center of the gate of the second transistor and a center of a gate of the third transistor. A method of manufacturing the semiconductor structure is also provided.