High-k Stack Width Overlap for LDD Protection
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Solution Overview
Problem
The existing semiconductor structures face issues with undesired saturation current and threshold voltage due to a gap between the high-k stack and the lightly doped drain (LDD), which also damages the interface layer during LDD implanting, degrading the breakdown voltage.
Innovation Solution
A semiconductor structure is designed with a high-k stack width greater than the gate region width, allowing the high-k stack to overlap the LDD and protect the interface layer, thereby reducing the gap and improving saturation current and threshold voltages, while the seal spacer region mitigates interfacial layer growth and protects the dummy poly region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal spacer region is used to protect the dummy poly region and mitigate interfacial layer growth, then the dummy poly region is protected and interfacial layer growth is reduced, but dopants are blocked from being implanted into certain areas of the substrate, creating a gap between the HK stack and LDD
Solution Approach 1:
The patent inverts the conventional approach by making the HK stack wider than the gate region, allowing the HK stack to extend laterally beyond the gate edges. This inversion enables the HK stack to reach under the seal spacer region and overlap with the LDD, thereby eliminating the gap that would otherwise be created by the seal spacer's protective function.
Solution Approach 2:
The patent utilizes the lateral dimension by increasing the HK stack width beyond the gate region width. This dimensional change allows the HK stack to extend in the lateral direction under the seal spacer and overlap with the LDD, solving the gap problem without compromising the seal spacer's protective function in the vertical dimension.
2Manufacturing precision
If the HK stack width is increased to overlap the LDD and improve saturation current and threshold voltages, then saturation current and threshold voltages are improved, but the gate region width becomes smaller relative to the HK stack width
Solution Approach 1:
The patent segments the device into distinct functional regions with different width characteristics. The HK stack is segmented to have a wider base that extends under the gate, while the gate region maintains its conventional width. This segmentation allows each region to be optimized independently for its specific function.
Solution Approach 2:
The patent applies local quality by giving different widths to different parts of the device structure. The HK stack has a larger width at its base compared to its top width, and this local variation in dimensions allows the stack to overlap the LDD while maintaining appropriate gate control in the upper region.
3Reliability
If the seal spacer region blocks dopants during LDD implanting, then the dummy poly region is protected, but an undesired saturation current and threshold voltage are caused due to the gap between LDD and HK stack
Solution Approach 1:
The patent employs preliminary action by designing the HK stack with an extended width before the LDD implantation process. This pre-configured geometry allows the HK stack to be positioned in advance to overlap with the LDD implantation region, ensuring proper dopant placement and eliminating the gap that would cause undesired electrical characteristics.
Data Source
AI summary
One or more embodiments of techniques or systems for forming a semiconductor structure are provided herein. In some embodiments, a semiconductor structure includes a substrate, a first lightly doped drain (LDD), a second LDD, an interface layer (IL), a high-k stack, a gate region, a dummy poly region, a first hard mask (HM) region, a second HM region, and a seal spacer region. The HK stack has a HK stack width and the gate region has a gate region width that is less than or substantially equal to the HK stack width. Because of the increased width of the HK stack, some of the HK stack likely overlaps some of the first LDD or the second LDD. In this manner, a saturation current and a threshold voltage associated with the semiconductor structure are improved. The increased width of the HK stack also protects more of the IL during LDD implanting.