Self-Aligned Backside Etch for Source/Drain and Gate Precision
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, existing etching and trimming processes face challenges in achieving precise alignment and reducing parasitic capacitance, leading to increased device density and performance limitations.
Innovation Solution
The implementation of self-aligned backside etching and trimming processes using spacers formed along the sidewalls of semiconductor fins as masks, allowing for accurate etching of gate structures and epitaxial source/drain regions, accompanied by the introduction of low-k dielectric materials and air gaps to reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching and trimming processes are used, then manufacturing simplicity is maintained, but manufacturing precision deteriorates due to alignment challenges at reduced feature sizes
Solution Approach 1:
The spacer structures serve as self-aligned masks that automatically define the etching boundaries. The spacers are formed conformally on the sidewalls of the fins, and their thickness directly determines the etch depth and pattern dimensions, eliminating the need for separate alignment steps and photoresist processing.
Solution Approach 2:
The spacer structures are formed in advance before the actual etching and trimming operations. These pre-formed spacers act as masks that guide subsequent etching steps, ensuring precise alignment without requiring real-time adjustment or complex alignment procedures during the etching process.
2Quantity of substance
If feature sizes are reduced to increase device density, then device density improves, but manufacturing precision deteriorates due to alignment difficulties
Solution Approach 1:
The self-aligned spacer process inherently provides the precision needed for reduced feature sizes. The spacers are deposited conformally and their dimensions are controlled by deposition thickness rather than lithographic patterning, enabling precise feature definition at scales where conventional lithography alignment becomes problematic.
Solution Approach 2:
The invention transitions from planar 2D patterning to 3D vertical structures. The spacers extend vertically along the fin sidewalls, and the etching process exploits this third dimension to achieve precise lateral patterning. The vertical spacer thickness controls the horizontal feature dimensions, effectively using vertical deposition to achieve horizontal precision.
3Reliability
If conventional dielectric materials are used, then manufacturing simplicity is maintained, but parasitic capacitance increases limiting device performance
Solution Approach 1:
Low-k dielectric materials are selectively placed in specific regions where parasitic capacitance is problematic, such as between adjacent fins and in interconnect regions. The dielectric constant varies locally - low-k materials are used where capacitance reduction is needed, while standard materials may be used in other regions, optimizing performance without uniformly increasing complexity.
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 enables the reduction of feature sizes, increases device density, and improves performance by enhancing the accuracy of etching and trimming processes, while also minimizing parasitic capacitance through the use of low-k dielectric materials and air gaps.
Implementation Method 1
a spacer layer is deposited over the structures
Implementation Method 2
a spacer layer is deposited over the structures
Implementation Method 3
The gate structures and the epitaxial source/drain regions may be etched using a self-aligned backside process
Data Source
AI summary
Methods of performing backside etching processes on source/drain regions and gate structures of semiconductor devices and semiconductor devices formed by the same are disclosed. In an embodiment, a semiconductor device includes a first transistor structure; a first interconnect structure on a front-side of the first transistor structure; and a second interconnect structure on a backside of the first transistor structure, the second interconnect structure including a first dielectric layer on the backside of the first transistor structure; a contact extending through the first dielectric layer to a source/drain region of the first transistor structure; and first spacers along sidewalls of the contact between the contact and the first dielectric layer, sidewalls of the first spacers facing the first dielectric layer being aligned with sidewalls of the source/drain region of the first transistor structure.