Source/Drain Epitaxy Structure for Larger Contact Plug Landing Areas
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Solution Overview
Problem
The complexity of processing and manufacturing of FinFETs increases with the scaling down of Integrated Circuit (IC) technology, particularly in forming source/drain regions with adequate landing areas for contact plugs while maintaining uniformity and controlling lateral growth.
Innovation Solution
A two-step epitaxy process is employed to grow semiconductor strips with straight-and-vertical edges, followed by a second epitaxy process that grows source/drain regions both vertically and horizontally, resulting in large landing areas for contact plugs without significant lateral expansion of the source/drain regions, and improving uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a conventional single-step epitaxy process is used to grow source/drain regions, then the process is simple and fast, but the landing areas for contact plugs are insufficient and uniformity is poor
Solution Approach 1:
The epitaxy process is divided into two distinct steps: a first epitaxy step that grows an initial semiconductor layer with controlled orientation, and a second epitaxy step that grows the final source/drain region with enlarged landing area. This segmentation allows each step to be optimized for its specific function, resolving the contradiction between process complexity and landing area quality.
Solution Approach 2:
The first epitaxy step performs a preliminary action by growing an initial semiconductor layer with specific crystal orientation and properties. This preliminary layer serves as a foundation that enables the second epitaxy step to achieve large landing areas with good uniformity, thereby resolving the contradiction by preparing the structure in advance.
2Area of moving object
If the epitaxy process is extended to grow larger landing areas, then the landing area increases, but the lateral growth of source/drain regions increases significantly
Solution Approach 1:
The patent applies different growth conditions and parameters to different regions and steps: the first epitaxy step uses conditions that promote vertical growth with controlled lateral expansion, while the second epitaxy step uses conditions that enlarge the landing area horizontally. This local quality control allows large landing areas without excessive lateral growth of the entire source/drain region.
Solution Approach 2:
The patent controls the dimensional growth by using crystal orientation control in the first epitaxy step to limit lateral growth, then utilizing the second epitaxy step to expand the landing area in the horizontal plane. This dimensional management resolves the contradiction between landing area size and source/drain lateral size.
3Productivity
If the epitaxy growth rate is increased to improve productivity, then the production efficiency increases, but the uniformity of source/drain regions deteriorates
Solution Approach 1:
The epitaxy process is segmented into two steps with different growth rates: the first epitaxy step uses a controlled, moderate growth rate to ensure uniformity and proper crystal orientation, while the second epitaxy step can use a higher growth rate to quickly achieve the desired landing area size. This segmentation resolves the contradiction between productivity and uniformity by applying different growth rates at different stages.
Solution Approach 2:
The first epitaxy step performs a preliminary action with controlled growth rate to establish uniform crystal structure and orientation. This preliminary uniform growth enables the second step to proceed at higher speed without sacrificing overall uniformity, thus resolving the contradiction between productivity and manufacturing precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the landing areas for contact plugs, reduces contact resistance, and improves the uniformity and performance of FinFETs by controlling the growth rates and edge orientations of the epitaxy layers.
Implementation Method 1
performing a first epitaxy process to grow a first semiconductor layer... performing a second epitaxy process to grow a second semiconductor layer on the first semiconductor layer
Data Source
AI summary
A method includes forming a gate stack on a first portion of a semiconductor fin, removing a second portion of the semiconductor fin to form a recess, and forming a source/drain region starting from the recess. The formation of the source/drain region includes performing a first epitaxy process to grow a first semiconductor layer, wherein the first semiconductor layer has straight-and-vertical edges, and performing a second epitaxy process to grow a second semiconductor layer on the first semiconductor layer. The first semiconductor layer and the second semiconductor layer are of a same conductivity type.