Asymmetric Source/Drain Recess for Backside Source Contact Alignment
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Solution Overview
Problem
As technology nodes shrink, it becomes increasingly difficult to accurately align backside source contacts in field-effect transistors (FETs), leading to performance degradation and fabrication challenges.
Innovation Solution
The method involves forming asymmetric source and drain structures by extending the recess for the source structure deeper into the substrate, creating a dummy source contact, and then replacing it with a real source contact during backside processing, thereby improving alignment and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If technology nodes are shrunk to increase functional density, then production efficiency and cost are improved, but manufacturing precision and alignment accuracy deteriorate
Solution Approach 1:
The patent applies preliminary action by forming a dummy source contact region before the actual source contact formation. This dummy region serves as a placeholder that guides subsequent alignment processes, ensuring that when the real source contact is formed, it can be accurately aligned to the source device despite the challenges of scaled dimensions. The dummy contact is formed in advance to establish a reference point for alignment.
Solution Approach 2:
The dummy source contact region acts as an intermediary element between the patterning process and the final source contact formation. It provides a temporary structure that facilitates accurate alignment during manufacturing, serving as a mediator that bridges the gap between the scaled-down feature sizes and the precision requirements of contact alignment.
2Manufacturing precision
If asymmetric source and drain structures are formed with extended recess depth, then source contact alignment is improved, but device structure complexity increases
Solution Approach 1:
The patent directly applies asymmetry by creating asymmetric source and drain structures where the source region has an extended recess depth compared to the drain region. This asymmetric design allows the source contact to be formed with improved alignment to the source device, while the drain structure maintains a shallower recess. The asymmetry is intentionally introduced to solve the alignment problem specific to the source contact.
Solution Approach 2:
The extended recess depth is applied locally only to the source region where it is needed for alignment purposes, rather than uniformly to both source and drain structures. This local modification allows the source contact to achieve better alignment without unnecessarily complicating the overall device structure or affecting the drain region.
Data Source
AI summary
According to one example, a method includes performing a first etching process on a fin stack to form a first recess and a second recess at a first depth, the first recess and the second recess on opposite sides of a gate structure that is on the fin stack. The method further includes depositing inner spacers within the first recess and the second recess. The method further includes, after depositing the inner spacers, performing a second etching process to extend a depth of the first recess to a second depth. The method further includes forming a dummy contact region within the first recess, forming a source structure within the first recess on the dummy contact region, and forming a drain structure within the second recess.