Self-Aligned Via Formation with Spacer Masks for Precise Interconnects
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Solution Overview
Problem
The formation of metal hard mask layers for defining the sizes and positions of metal lines and vias in integrated circuits is prone to damage, leading to defects in these interconnect structures.
Innovation Solution
The use of mandrels and spacers in a double patterning process, where spacers are formed tall without increasing their lateral dimensions, allowing them to function effectively as etching masks for forming metal lines and vias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal hard mask layer is used for defining metal lines and vias, then the sizes and positions can be defined, but the hard mask layer may be damaged causing defects
Solution Approach 1:
The patent divides the patterning process into two separate steps using spacers: first forming mandrels, then forming spacers on mandrel sidewalls to create the final pattern. This segmentation allows each step to be optimized independently, improving both precision and reliability by avoiding the need for a separate hard mask layer that is prone to damage.
Solution Approach 2:
The spacers act as an intermediary structure between the mandrels and the final metal lines/vias. By using spacers as the primary patterning element rather than a hard mask layer, the process eliminates the reliability issue of hard mask damage while maintaining precise dimensional control through the self-aligned spacer formation.
2Reliability
If spacers are formed tall to function as etching masks, then etching effectiveness is improved, but lateral dimensions may increase
Solution Approach 1:
The patent transitions from controlling pattern dimensions in the lateral plane to controlling etching mask effectiveness in the vertical dimension. By forming tall spacers with sufficient height for effective etching while maintaining narrow lateral dimensions through self-aligned formation, the solution resolves the contradiction by operating in a different dimensional space.
Solution Approach 2:
The spacers are designed with different properties in different dimensions: tall height in the vertical direction for effective etching mask performance, and controlled narrow width in the lateral direction for precise pattern definition. This local differentiation of qualities allows simultaneous optimization of both etching effectiveness and dimensional control.
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.