Source/Drain Contact Plug Layout for Lower Transistor Resistance
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Solution Overview
Problem
In semiconductor devices, insufficient contact between gate structures and source/drain layers leads to increased contact resistance, hindering effective signal transfer.
Innovation Solution
The semiconductor device incorporates a substrate with specific source/drain patterns and channel patterns, along with gate structures and contact plugs, designed to enhance contact integrity and reduce resistance by varying the height and depth of the contact plugs and source/drain layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact plug structures are used to connect gate structures and source/drain layers, then device fabrication is simplified, but contact resistance increases due to insufficient contact
Solution Approach 1:
The source/drain structure is divided into multiple layers (first source/drain layer, second source/drain layer, third source/drain layer) with different depths and conductivity type impurities. This segmentation allows each layer to serve specific functions: the first layer provides shallow contact, the second layer extends deeper for additional contact area, and the third layer provides deep contact, collectively reducing contact resistance while maintaining manageable fabrication complexity through systematic layering
Solution Approach 2:
Different regions of the source/drain structure are assigned different properties: the first source/drain layer contains first conductivity type impurities, the second source/drain layer contains second conductivity type impurities, and the third source/drain layer contains first conductivity type impurities again. This local quality variation creates optimized contact regions at different depths with appropriate conductivity characteristics for their specific contact functions
2Reliability
If contact plug depth is increased to improve contact resistance, then contact resistance decreases, but manufacturing precision requirements increase
Solution Approach 1:
Instead of using a single deep contact plug that would require precise depth control, the structure is segmented into three contact plugs at different depths (first, second, and third source/drain layers). Each contact plug can be formed with more relaxed depth precision requirements since they work collectively, with the shallowest plug providing initial contact and deeper plugs providing additional contact area without requiring each individual plug to achieve perfect depth alignment
Solution Approach 2:
The contact structure transitions from a single-dimensional (single depth level) approach to a multi-dimensional approach by stacking contact plugs vertically at different depth levels. This dimensional change allows the system to achieve equivalent or superior contact performance through distributed contact areas at multiple depths rather than relying on a single precisely-controlled deep contact interface
Data Source
AI summary
A semiconductor device may include a substrate, a first source/drain pattern and a second source/drain pattern spaced apart in a first direction on the substrate, a height from an upper surface of a central portion of the first source/drain pattern to an upper surface of the substrate in a vertical direction is lower than a height from an upper surface of an edge of the first source/drain pattern to the upper surface of the substrate, a plurality of channel patterns connecting between the first source/drain pattern and the second source/drain pattern, and the plurality of channel patterns stacked to be spaced apart from each other, a gate structure surrounding the plurality of channel patterns and extending in a second direction, and a contact plug extending in the vertical direction from an upper surface of the first source/drain pattern, and the contact plug connected to the first source/drain pattern.