BEOL Trench-Via Structure With Dielectric Liner Against Via Blowout
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the formation of sloped via sidewalls due to excessive etching during the dual-damascene process, leading to potential shorting between vias and adjacent metal lines, which is exacerbated by the increasing density of metal lines in BEOL structures.
Innovation Solution
A dielectric liner is applied to the sidewalls and bottom of the via and trench openings to protect the corner regions during etching, using a dual-damascene process, and a metallic liner is used to connect the via to the metal line, with a higher dielectric constant than the surrounding layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If excessive etching is performed during the dual-damascene process to ensure complete removal of the etch-stop layer, then the via opening is fully formed, but the sidewalls become substantially sloped causing potential shorting between via and adjacent metal lines
Solution Approach 1:
A dielectric liner is deposited on the sidewalls of the via opening and trench opening before the etching process. This preliminary protective layer prevents corner erosion during etching, allowing the etch-stop layer to be completely removed while maintaining vertical sidewalls and preventing shorting between the via and adjacent metal lines
Solution Approach 2:
The dielectric liner acts as an intermediary protective layer between the etching process and the via/trench corners. It is selectively removed afterward using a self-assembled monolayer (SAM) that targets only the liner material, enabling clean removal without damaging the underlying structure
2Manufacturing precision
If a dielectric liner is added to protect corner regions during etching, then via blowout and corner erosion are prevented, but the process complexity increases
Solution Approach 1:
A self-assembled monolayer (SAM) is used to selectively remove the dielectric liner after it has served its protective function. The SAM automatically targets and removes only the liner material, eliminating the need for complex selective etching processes and reducing overall process complexity
Solution Approach 2:
The dielectric liner material is specifically chosen with different etch selectivity compared to surrounding materials. This parameter difference enables selective removal of the liner after etching, allowing the protective layer to be easily eliminated without affecting other structures
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 prevents corner erosion and via blowout, ensuring steeper sidewalls and reliable connections between metal levels, reducing the risk of shorting and enhancing the structural integrity of BEOL interconnects.
Implementation Method 1
a dielectric liner lining sidewalls of the via, the dielectric liner being absent at a bottom and a top of the via. The dielectric liner protects a corner between the trench and the via during an etch process of forming the structure
Implementation Method 2
a metallic liner lining a surface of the common conductive core of the trench and the via of the second metal level
Data Source
AI summary
Embodiments of present invention provide a method of forming a semiconductor structure. The method includes providing a first dielectric layer with a metal line in a first metal level; forming a second dielectric layer on top of the first dielectric layer; creating a trench opening over a via opening in the second dielectric layer; selectively forming a dielectric liner lining sidewalls and a bottom surface of the trench opening and lining sidewalls of the via opening; and filling the trench opening and the via opening with a conductive material to form a trench directly over a via with a common conductive core. A structure formed thereby is also provided.