FinFET Source/Drain Epi Growth on Thinned Fin Structures
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Solution Overview
Problem
The formation of diamond-shaped epi semiconductor material in FinFET devices leads to increased fin pitches, causing electrical shorts and reduced product yields due to its large lateral width, and the conductive source/drain contact structure only contacts the upper surfaces, resulting in higher contact resistance.
Innovation Solution
A method involving forming a gate around an initial fin structure, trimming it to reduce size, and growing conformal epi semiconductor material on the thinned fin portion, with a conductive source/drain contact structure wrapped around it to ensure full surface contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diamond-shaped epi semiconductor material is formed on fins, then the epi material provides necessary conductivity and structural integrity, but the large lateral width causes electrical shorts between adjacent fins and reduces product yields
Solution Approach 1:
The fin structure is segmented into two distinct portions: a first portion with a first crystallographic orientation and a second portion with a second crystallographic orientation. This segmentation allows different epi growth behaviors in different regions, enabling the lateral width of epi material to be controlled and reduced while maintaining necessary conductivity. The segmentation of crystal orientations directly addresses the technical contradiction by allowing precise control over epi material dimensions.
Solution Approach 2:
Different crystallographic orientations are assigned to different portions of the fin structure. The first portion has a first crystallographic orientation that promotes epi growth with a first lateral width, while the second portion has a second crystallographic orientation that promotes epi growth with a second, smaller lateral width. This local quality variation enables the epi material to have reduced lateral width in critical areas, preventing electrical shorts while maintaining conductivity where needed.
2Productivity
If fin pitch is reduced to increase device density, then more fins can be packed on the chip, but the large lateral width of diamond-shaped epi material makes area scaling difficult and increases the chance of merger between adjacent epi materials
Solution Approach 1:
The fin structure is divided into portions with different crystallographic orientations, enabling different epi growth characteristics in different regions. This segmentation allows the lateral width of epi material to be controlled and reduced, enabling smaller fin pitches and higher device density without the risk of epi material merger between adjacent fins.
Solution Approach 2:
The crystallographic orientation parameter is changed between different portions of the fin structure. By varying this fundamental parameter, the lateral width of the resulting epi material is controlled, allowing for reduced dimensions that enable area scaling and higher device density while preventing unwanted merger effects.
3Ease of manufacture
If conductive source/drain contact structure only contacts upper surfaces of epi material, then fabrication is simpler, but contact resistance is higher
Solution Approach 1:
The contact structure is extended from a two-dimensional surface contact into the third dimension by wrapping around the epi material. This dimensional transition enables the contact to access multiple surfaces of the epi material, reducing contact resistance while maintaining fabrication feasibility through a systematic wrapping process.
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 reduces the lateral width of the epi material, minimizing the chance of electrical shorts and enabling smaller fin pitches, while ensuring comprehensive contact and reduced resistance.
Implementation Method 1
performing a fin trimming process on the exposed portion of the initial fin structure so as to produce a reduced-size fin portion... forming a conformal epi semiconductor material on the reduced-size fin portion
Data Source
AI summary
One illustrative method disclosed includes, among other things, forming a gate around an initial fin structure and above a layer of insulating material, and performing a fin trimming process on an exposed portion of the initial fin structure in the source/drain region so as to produce a reduced-size fin portion positioned above a surface of a layer of insulating material in the source/drain region of the device, wherein the the reduced-size fin portion has a second size that is less than the first size. In this example, the method also includes forming a conformal epi semiconductor material on the reduced-size fin portion and forming a conductive source/drain contact structure that is conductively coupled to and wrapped around the conformal epi semiconductor material