Self-Aligned Lateral Contacts for Buried Power Rail Scaling
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Solution Overview
Problem
Buried or backside power rail configurations in integrated circuits face challenges such as increased contact layers leading to taller stacks and higher electrical resistance due to overlay errors, limiting the scaling of memory and logic cells.
Innovation Solution
The formation of self-aligned lateral contacts, where a first trench contact is aligned with a gate structure and a second trench contact has non-contiguous portions with a shorter height, providing an electrical pathway and connecting to an underlying power rail, reducing the need for stacked configurations and minimizing overlay errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stacked contact configurations are used to connect to buried power rails, then connectivity is achieved, but electrical resistance increases and critical dimensions must be larger
Solution Approach 1:
The patent transitions from a vertical stacked contact configuration to a lateral contact configuration. The lateral contact extends horizontally along the power rail at a reduced height, providing an alternative dimensional pathway that reduces the number of vertical interfaces and associated resistance, while maintaining electrical connectivity to the buried power rail.
2Reliability
If multiple contact layers are used to reach buried power rails, then power delivery is enabled, but device complexity increases
Solution Approach 1:
The patent extracts the lateral contact portion from the stacked contact structure. Instead of requiring multiple vertical contact layers to reach the power rail, a lateral contact segment is introduced that connects to the power rail horizontally, reducing the number of required contact layers and simplifying the overall contact architecture.
3Manufacturing precision
If larger critical dimensions are used for contacts and vias, then manufacturing is easier, but cell size scaling is limited
Solution Approach 1:
By introducing the lateral contact configuration, the patent reduces the vertical height requirement of contacts while maintaining connectivity. This dimensional change allows for smaller critical dimensions in the vertical direction, enabling further scaling of cell size without compromising manufacturing feasibility, as the lateral extension provides the necessary contact length.
Data Source
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AI summary
Techniques to form self-aligned lateral contacts. In an example, a first trench contact contacts a source or drain region of a transistor. A second trench contact includes non-contiguous first and second portions, each portion having a top surface that is co-planar with a top surface of the first trench contact as well as a top surface of the gate structure. A sidewall of the second trench contact is self-aligned to, and interfaces with, a sidewall of the first trench contact. A via extends from the first portion of the second trench contact to an underlying power rail. In some cases, the second portion of the second trench contact extends over a source or drain region of another transistor, without contacting that source or drain region. The fly-over portion of the second trench contact has a maximum height that is shorter than a maximum height of the first trench contact.