Continuous Active Region for Semiconductor Transistor Layout
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Solution Overview
Problem
Conventional semiconductor designs require discontinuities (OD breaks) between n-type and p-type transistors to prevent defects, leading to poorer performance in edge transistors and inefficient use of chip space due to the Length of Oxide Definition (LOD) effect, which results in reduced design flexibility and increased real estate usage.
Innovation Solution
A continuous active region is formed over both n-type and p-type wells with gate structures disposed directly over the boundary between them, eliminating the need for OD breaks and allowing n-type and p-type source/drain features to share a channel region, thereby avoiding the LOD effect and reducing the area occupied by dummy transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discontinuities (OD breaks) are introduced between n-type and p-type transistors to prevent defects, then reliability is improved, but area of stationary object increases and device complexity increases
Solution Approach 1:
The patent removes the OD break (discontinuity) from the active region between n-type and p-type transistors. By extracting this isolation structure, the active region becomes continuous, eliminating the LOD effect and allowing edge transistors to be operational, thereby reducing wasted chip space while maintaining reliability through alternative defect prevention mechanisms
Solution Approach 2:
Instead of introducing discontinuities to prevent defects, the patent inverts the approach by using a continuous active region and placing gate structures directly over the boundary between n-type and p-type wells. This inversion eliminates the LOD effect and allows all transistors including edge transistors to be operational
2Reliability
If discontinuities (OD breaks) are introduced between n-type and p-type transistors, then defect prevention is improved, but design flexibility deteriorates
Solution Approach 1:
The patent inverts the conventional approach by eliminating OD breaks and using a continuous active region with gate structures positioned directly over the boundary between n-type and p-type wells. This enables greater design flexibility as all transistors can be operational without being constrained by LOD effect limitations
Solution Approach 2:
The continuous active region serves multiple functions: it provides a unified structure for both n-type and p-type transistors, enables edge transistors to be operational, eliminates the LOD effect, and allows flexible transistor placement and circuit design without requiring discontinuities
3Reliability
If OD breaks are used to separate n-type and p-type transistors, then reliability is improved, but productivity deteriorates due to increased real estate usage
Solution Approach 1:
The patent extracts the OD break structure from the design, creating a continuous active region that eliminates the LOD effect. This increases the effective transistor density and functional area, thereby improving productivity through more efficient chip space utilization
Solution Approach 2:
By inverting the conventional approach of using OD breaks for isolation, the patent achieves higher transistor density and better utilization of chip real estate, leading to improved productivity while maintaining reliability through the continuous active region structure
Data Source
AI summary
Semiconductor structures and methods are provided. A semiconductor structure according to an embodiment includes a substrate having an n well abutting a p well along a boundary. The semiconductor structure also includes a continuous active region over the n well and the p well, a plurality of gate structures over channel regions of the continuous active region, and one gate structure of the plurality of gate structures is disposed directly over the boundary. A portion of the channel region directly under the one gate structure is in direct contact with both an n-type source/drain feature over the p well and a p-type source/drain feature over the n well.