Self-Aligned Via Formation Using Spacers for Precise Interconnect Patterning
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Solution Overview
Problem
The formation of metal lines and vias in integrated circuits is challenged by the damage of metal hard mask layers, leading to defects in these interconnect structures.
Innovation Solution
The use of mandrels and spacers in a double patterning process, where spacers are formed on the sidewalls of mandrels and used as etching masks to define the dimensions of metal lines and vias without increasing their lateral dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a metal hard mask layer is used to define the sizes and positions of metal lines and vias, then the dimensions and positions can be defined, but the hard mask layer may be damaged causing defects in metal lines and vias
Solution Approach 1:
The patent introduces an intermediary material layer between the mandrel and the metal hard mask layer. This intermediary layer serves as a protective buffer that prevents damage to the metal hard mask layer during subsequent processing steps, while still allowing the mandrel-spacer structure to define the precise dimensions and positions of metal lines and vias.
Solution Approach 2:
The patent segments the patterning process into multiple stages: first forming mandrels, then forming spacers on mandrel sidewalls, and using this segmented structure as the definition template for metal lines and vias. This segmentation allows the metal hard mask layer to be applied later in the process, reducing its exposure to damaging conditions while maintaining dimensional precision.
2Manufacturing precision
If spacers are formed on mandrel sidewalls to define metal line dimensions, then precise dimensions can be achieved without increasing lateral dimensions, but the process complexity increases due to double patterning
Solution Approach 1:
The spacers are formed through a self-aligned process where the spacer material is deposited conformally on the mandrel sidewalls and then anisotropically etched. This self-aligned formation automatically positions the spacers with precise dimensions without requiring additional lateral dimension adjustments, and the spacers themselves serve as the etching mask for defining metal line patterns.
Solution Approach 2:
The patent transitions from two-dimensional lithographic patterning to three-dimensional spacer-based patterning. By forming vertical spacers on mandrel sidewalls and using their lateral projections to define metal line dimensions, the process achieves precise dimensional control through vertical structure formation rather than lateral lithographic patterning.
Data Source
AI summary
A method includes forming a first mandrel and a second mandrel over a dielectric layer, and forming a first spacer and a second spacer on the first mandrel and the second mandrel, respectively. The first spacer and the second spacer are next to each other with a space in between. The dielectric layer is etched to form an opening in the dielectric layer, with the opening being overlapped by the space, and with the first spacer and the second spacer being used as a part of an etching mask in the etching. A conductive material is filled into the opening. A planarization process is performed on the conductive material.