Standard Cell Trench Isolation for Larger Active Regions
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Solution Overview
Problem
As technologies scale smaller, standard cell track heights decrease, reducing the active region area in integrated circuits and leading to issues such as electromigration/voltage drop, timing degradation, design rule compliance violations, defects, and performance problems when attempting to increase active region area through power rail width reduction, signal metal width reduction, and contact size reduction.
Innovation Solution
The integration of a trench isolation structure that electrically isolates active regions and gate electrodes, with conductive straps coupling them, allowing for maximized active region area and height by forming trench isolation post-gate electrode formation, thereby optimizing transistor characteristics without requiring metal width or contact size reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If standard cell track height is reduced to scale smaller, then device size decreases, but active region area decreases leading to performance degradation
Solution Approach 1:
The trench isolation structure extends vertically through the substrate, utilizing the third dimension (depth) to achieve electrical isolation. This allows active regions to be positioned closer together in the horizontal plane while maintaining proper isolation, effectively increasing the usable active region area within the same footprint without compromising device performance.
Solution Approach 2:
The substrate is divided into isolated regions by the trench isolation structure, creating separate active regions that can be independently optimized. This segmentation allows each active region to be maximized in area while maintaining electrical isolation, resolving the contradiction between compact device size and sufficient active region area.
2Area of stationary object
If power rail width is reduced to increase active region area, then active region area increases, but electromigration and voltage drop issues occur
Solution Approach 1:
The trench isolation structure acts as an intermediary element that enables proper spacing and isolation between active regions. This allows power rails to maintain sufficient width for reliable current carrying while still maximizing the active region area, as the trench isolation provides the necessary electrical separation without requiring excessive spacing.
3Area of stationary object
If signal metal width and spacing are reduced to increase active region area, then active region area increases, but timing degradation and design rule violations occur
Solution Approach 1:
By utilizing vertical isolation through the trench structure, the design gains freedom in the horizontal plane to maintain proper metal spacing and width for timing and DRC compliance while maximizing active region area. The third-dimensional isolation eliminates the need for excessive horizontal spacing.
4Area of stationary object
If contact size is reduced to increase active region area, then active region area increases, but defects and performance issues arise
Solution Approach 1:
The trench isolation creates well-defined, isolated active regions with clear boundaries. This segmentation allows for optimized contact placement and sizing within each isolated region, ensuring adequate contact area for reliable electrical connection while maximizing the overall active region area available for transistor formation.
Data Source
Figure 1
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Figure 3A
AI summary
A standard cell or integrated circuit (IC) structure includes a substrate including a first active region and a second active region. A first gate electrode is over the first active region; and a second gate electrode over the second active region. A trench isolation electrically isolates the first active region and the first gate electrode from the second active region and the second gate electrode. First ends of the first active region and the first gate electrode abut a first sidewall of the trench isolation and first ends of the second active region and the second gate electrode abut a second, opposing sidewall of the trench isolation. A conductive strap extends over an upper end of the trench isolation and electrically couples the first gate electrode and the second gate electrode.