Spacer-Defined Backside Etching for Gate and Source/Drain Alignment
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, existing etching processes struggle to achieve precise alignment and accuracy, leading to increased device density challenges and parasitic capacitance issues.
Innovation Solution
The implementation of self-aligned backside etching and trimming processes using spacers formed along semiconductor fins as masks, which allows for precise 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 processes are used for feature size reduction, then manufacturing simplicity is maintained, but manufacturing precision deteriorates
Solution Approach 1:
The patent applies preliminary action by forming spacer structures before the etching process. The spacers are deposited conformally on the fin structures and then anisotropically etched to create self-aligned masks that define the gate and source/drain regions. This preliminary spacer formation enables precise alignment without requiring additional lithography steps, resolving the contradiction between precision and complexity.
Solution Approach 2:
The patent implements self-service through self-aligned etching where the spacer structures automatically serve as etch masks. The spacers are positioned by the fin geometry itself, and the etch process uses the spacers to define the gate and source/drain regions without external alignment. This self-aligning mechanism achieves high precision while simplifying the overall process by eliminating separate alignment steps.
2Productivity
If feature size is reduced to increase device density, then device density improves, but manufacturing precision deteriorates
Solution Approach 1:
The self-aligned etching process allows the spacer structures to automatically define the etch boundaries based on the fin geometry. This self-service mechanism ensures that even as feature sizes are reduced to increase device density, the alignment precision is maintained because the spacers are positioned by the fins themselves rather than by separate lithography alignment steps.
3Object-generated harmful factors
If conventional etching processes are used, then process simplicity is maintained, but parasitic capacitance increases
Solution Approach 1:
The patent uses preliminary action by forming spacer structures that serve as self-aligned masks before the etching process. This enables precise definition of gate and source/drain regions, which reduces overlapping and parasitic capacitance. The spacers are deposited conformally and then anisotropically etched to create the necessary patterns without requiring additional lithography steps.
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.