Asymmetric Source and Drain Structures for FinFET Scalability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in integrated circuit fabrication lies in achieving efficient 3D scaling and device density enhancement while overcoming the limitations of conventional lithographic processes, particularly in forming terminals for vertically-oriented devices and managing the trade-off between feature size and spacing, as well as the complexity and cost of existing 3D integration techniques.
Innovation Solution
The implementation of asymmetric source and drain structures with deep source and shallow drain configurations, allowing for backside metal contact and front-side contact integration, respectively, along with advanced lithography and dual/quad patterning techniques, enables looser metal pitches and improved interconnect scalability, facilitating robust and high-performance fin, nanowire, or nanoribbon transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional symmetric source and drain structures are used, then fabrication process is simpler, but device performance and scalability are limited
Solution Approach 1:
The patent applies asymmetry by creating asymmetric source and drain structures where one source/drain structure has a first depth and the other has a second depth different from the first. This asymmetric configuration improves device performance by enabling better control over carrier flow and reducing short-channel effects, while the patent manages the increased complexity through systematic fabrication processes.
Solution Approach 2:
The patent implements local quality by selectively differentiating the source and drain regions with different depths and configurations. Each source/drain structure is locally optimized for its specific function, with the deeper structure providing enhanced control and the shallower structure facilitating easier contact access, thereby improving overall device performance without uniform complexity throughout.
2Ease of operation
If deep source and shallow drain structures are implemented, then access to source and drain regions is improved, but fabrication complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the source and drain formation into separate, staged processes. The first source/drain structure is formed with a first depth through initial etching and filling, then the second source/drain structure is formed with a second depth through subsequent selective removal and refilling. This segmentation enables improved access to different regions while managing fabrication complexity through systematic, multi-step processing.
Solution Approach 2:
The patent implements preliminary action by performing selective removal of portions of the first source/drain structure before forming the second source/drain structure. This preliminary modification creates the necessary conditions for subsequent asymmetric formation, enabling the deeper structure to be established first and then selectively reduced to create the shallower counterpart, thereby facilitating differential access.
3Area of stationary object
If conventional lithographic processes are used, then feature patterning is straightforward, but spacing between features must be large
Solution Approach 1:
The patent applies dimensionality change by transitioning from two-dimensional planar source/drain structures to three-dimensional asymmetric structures with different depths. This vertical differentiation allows features to be packed more closely in the lateral direction while maintaining adequate spacing through vertical separation, thereby increasing device density without compromising the necessary spacing between features for proper functionality.
Data Source
AI summary
Integrated circuit structures having asymmetric source and drain structures, and methods of fabricating integrated circuit structures having asymmetric source and drain structures, are described. For example, an integrated circuit structure includes a fin, and a gate stack over the fin. A first epitaxial source or drain structure is in a first trench in the fin at a first side of the gate stack. A second epitaxial source or drain structure is in a second trench in the fin at a second side of the gate stack, the second epitaxial source or drain structure deeper into the fin than the first epitaxial source or drain structure.