Deep Via Contact Structure for Low-Resistance Nanosheet Transistors
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Solution Overview
Problem
The challenge in integrated circuit fabrication lies in reducing contact resistance and improving transistor performance, particularly in deep via structures, where conventional methods face limitations in scaling and lithographic processes, leading to trade-offs between feature dimension and spacing, especially as dimensions approach the 10 nanometer node.
Innovation Solution
The approach involves creating deep via structures with a conductive material that extends laterally beside epitaxial source or drain structures, using a process that includes recessing, isotropic etching to widen trenches, and refilling with metal, which reduces contact resistance and enhances transistor performance by increasing the contact critical dimension and improving the contact profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional lithographic processes are used to pattern features at smaller dimensions, then feature size can be reduced to increase device density, but the spacing between features becomes insufficient leading to manufacturing challenges
Solution Approach 1:
The contact structure is divided into two distinct components: a trench contact structure extending from the front surface, and a deep via structure extending from the back surface. These two segments meet within the substrate to form the complete contact, allowing each segment to be formed with adequate spacing using conventional lithography while achieving small overall contact dimensions
Solution Approach 2:
The contact structure is formed by transitioning from a single-sided (front surface only) approach to a dual-sided approach, utilizing both the front and back surfaces of the substrate. This dimensional change allows the contact to be constructed from two directions, enabling better control over feature spacing and reducing lithographic constraints
2Reliability
If deep via structures are formed with conventional methods, then contact resistance can be reduced, but the contact critical dimension and profile are compromised
Solution Approach 1:
The contact structure is segmented into a trench contact portion and a deep via portion, each optimized for its specific function. The trench contact provides a broad base with good critical dimension control, while the deep via extends vertically to reduce contact resistance, with each segment formed using appropriate process parameters
Solution Approach 2:
Different regions of the contact structure are given different properties: the trench contact portion has a wider cross-section optimized for lithographic patterning and mechanical stability, while the deep via portion has a narrower profile optimized for low resistance electrical connection, with each region's properties tailored to its specific requirements
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 method effectively reduces backside contact resistance and improves transistor performance by allowing for greater cell scaling and more efficient interconnects, enabling better performance and density in integrated circuits.
Implementation Method 1
isotropic etching to widen trenches
Implementation Method 2
refilling with metal
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Integrated circuit structures having deep via structures, and methods of fabricating integrated circuit structures having deep via structures, are described. An integrated circuit structure includes a plurality of horizontally stacked nanowires. A gate structure is over the plurality of horizontally stacked nanowires. An epitaxial source or drain structure (110A) is at an end of the plurality of horizontally stacked nanowires. A conductive trench contact structure (124) is vertically over the epitaxial source or drain structure. A conductive via (136) is vertically beneath and extends into the conductive trench contact structure. The conductive via has a first width beneath the epitaxial source or drain structure less than a second width laterally adjacent to the epitaxial source or drain structure.