Multi-Work-Function Gate Layout for STI Kink Effect Mitigation
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Solution Overview
Problem
Modern integrated chips face performance degradation due to leakage currents and the kink effect caused by divots in shallow trench isolation structures, which affect threshold and sub-threshold voltages, leading to unpredictable device behavior.
Innovation Solution
A transistor device with a gate structure comprising multiple gate electrode regions of different work functions, where the source and drain regions have smaller widths than the channel region, and the gate structure extends over the channel region to separate it from the isolation structure edges, mitigating the impact of divots and dopant diffusion on threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the channel region is placed close to the isolation structure edges to increase device density, then the device functionality is improved, but the kink effect and threshold voltage instability increase due to divots and dopant diffusion
Solution Approach 1:
The patent introduces a gate structure as an intermediary element that extends over the channel region and overlaps with the isolation structure. This gate structure acts as a mediator that electrically isolates the channel region from the divots and dopant diffusion at the isolation structure edges, thereby maintaining threshold voltage stability while allowing the channel to be positioned close to the isolation structure for high device density.
Solution Approach 2:
The patent utilizes vertical stacking by extending the gate structure in the vertical dimension over the channel region and overlapping with the isolation structure. This dimensional approach allows the channel to be positioned close to the isolation structure edges in the horizontal plane while the gate structure provides protective overlap in the vertical dimension, resolving the contradiction between density and stability.
2Reliability
If the gate structure extends over the channel region to mitigate divot effects, then the threshold voltage stability is improved, but the device complexity increases
Solution Approach 1:
The gate structure performs multiple functions simultaneously: it provides the primary gate control for the transistor operation and extends over the channel region to mitigate the kink effect and threshold voltage instability. By making the gate structure multi-functional, the patent avoids adding separate protective structures, thereby reducing overall device complexity while maintaining threshold voltage stability.
3Reliability
If the source and drain regions are made smaller than the channel region, then the kink effect is reduced, but the device area increases
Solution Approach 1:
The patent applies local quality by making the source and drain regions smaller than the channel region width. This creates a configuration where the channel region extends beyond the source and drain regions, providing a wider effective channel that reduces the kink effect. The local variation in dimensions optimizes electrical performance while managing device area.
Data Source
AI summary
An integrated chip comprises a substrate, an isolation structure and a gate structure. The isolation structure is disposed in the substrate and enclosing an active region in the substrate. The active region comprises a source region and a drain region separated by a channel region along a first direction. The gate structure is disposed over the channel region and comprising a first gate electrode region and a second gate electrode region arranged one next to another laterally along a second direction perpendicular to the first direction. The first gate electrode region has a first composition, and the second gate electrode region has a second composition different than the first composition.