Tapered COAG Contacts for Sub-10 nm Gate Isolation
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Solution Overview
Problem
Conventional integrated circuit fabrication processes face challenges in scaling to sub-10 nanometer nodes due to variability and limitations in forming contacts over active gate regions, leading to issues such as defect modes, yield degradation, and inefficient use of layout space.
Innovation Solution
The implementation of contact over active gate (COAG) structures with tapered gates or trench contacts, which involve recessing gates and trench contacts, and using inner spacers to increase edge placement error margins, enabling contacts to be formed directly over active gates without shorting adjacent regions, and utilizing self-align trench contact flows to improve etch selectivity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication processes are used for scaling, then existing process infrastructure can be maintained, but manufacturing precision and reliability deteriorate at sub-10 nanometer nodes due to variability
Solution Approach 1:
The gate structure serves as its own alignment reference for contact formation. The contact opening is self-aligned to the gate, using the gate's physical structure (sidewalls, top surface) as the positioning reference, eliminating the need for separate alignment processes and reducing variability
Solution Approach 2:
The gate is recessed and prepared with specific structural features (sidewall angle, top surface geometry) before contact formation. This preliminary structuring creates optimal conditions for subsequent contact opening and filling, ensuring precision at sub-10nm nodes
2Area of stationary object
If contacts are formed over active gate regions, then layout space efficiency improves, but risk of shorting adjacent regions increases
Solution Approach 1:
Dielectric spacers are introduced as intermediary structures between the contact opening and adjacent gate regions. These spacers physically separate the contact from neighboring gates, preventing shorting while allowing the contact to be positioned over the active gate region for space efficiency
Solution Approach 2:
The gate structure is given different local properties: the contact region has a recessed top surface with specific sidewall angles, while other regions maintain standard gate geometry. This local differentiation enables precise contact formation without affecting adjacent regions
3Reliability
If tapered gates or trench contacts are implemented, then contact formation reliability improves, but device complexity increases
Solution Approach 1:
Multiple functions are merged into the gate recess structure: it serves as both the gate electrode support and the alignment reference for contact formation. The sidewalls of the recess provide both structural integrity and the geometric reference needed for self-aligned contact opening
Solution Approach 2:
The contact formation process is segmented into distinct stages: gate recess preparation, spacer formation, contact opening, and metal filling. Each stage is optimized independently, allowing complex structures to be built through manageable sequential steps
Data Source
AI summary
Contact over active gate (COAG) structures with a tapered gate or trench contact are described. In an example, an integrated circuit structure includes a plurality of gate structures above a substrate, wherein individual ones of the plurality gate of structures have thereon a conductive cap between sidewall spacers. A plurality of conductive trench contact structures is alternating with the plurality of gate structures, wherein individual ones of the plurality of conductive trench contact structures have thereon a conductive cap between sidewall spacers. A conductive structure is in direct contact with the conductive cap and sidewall spacers on one of the plurality of gate structures or with the conductive cap and sidewall spacers on one of the plurality of conductive trench contact structures.