Self-aligned via formation using hard mask alignment
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Solution Overview
Problem
Current semiconductor fabrication methods for forming self-aligned vias to conductive lines are prone to alignment errors and require additional costly lithography steps, leading to issues like higher via resistance, shorting, and electrical opens.
Innovation Solution
A method involving the formation of a hard mask adjacent to the conductive line, followed by a second dielectric layer with via openings that land partially on the hard mask to self-align the via, eliminating the need for extra lithography steps and alignment features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional masking and etching steps are used to self-align vias to conductive lines, then alignment precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The hard mask layer is formed to automatically define the via alignment position through its geometric relationship with the conductive line, eliminating the need for separate alignment features. The via opening is formed to land on the hard mask, which self-aligns the via to the conductive line without requiring additional lithography steps or complex masking procedures.
Solution Approach 2:
The hard mask layer is formed in advance between the conductive lines before via formation. This preliminary action establishes the alignment reference for subsequent via openings, allowing the via to be self-aligned to the conductive line without requiring real-time alignment adjustments or additional lithography steps.
2Manufacturing precision
If additional lithography steps are added to achieve self-alignment, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The alignment function is merged into the hard mask layer formation step that already exists in the process flow. Instead of adding separate lithography steps for alignment, the hard mask serves dual purposes: as an etch stop layer and as an alignment reference, combining multiple functions into a single process step.
Solution Approach 2:
The hard mask layer automatically provides alignment functionality through its predetermined position relative to the conductive line. The via opening process uses the hard mask as a self-aligning reference, eliminating the need for additional lithography steps and maintaining high fabrication throughput while achieving precise via alignment.
3Device complexity
If via openings are formed without hard mask, then manufacturing complexity is reduced, but manufacturing precision deteriorates
Solution Approach 1:
The hard mask layer acts as an intermediary element between the conductive line and the via opening. It provides a physical reference structure that mediates the alignment process, allowing the via to be precisely positioned relative to the conductive line without requiring complex lithography alignment procedures.
Solution Approach 2:
The hard mask layer provides self-aligning functionality through its predetermined geometric relationship with the conductive line. The via opening process inherently aligns to the hard mask, which in turn aligns to the conductive line, creating a self-aligning system that achieves high precision without adding process complexity.
Data Source
AI summary
A method of forming a via and a wiring structure formed are disclosed. The method may include forming a conductive line in a first dielectric layer; forming a hard mask adjacent to the conductive line after the conductive line forming; forming a second dielectric layer over the hard mask; and forming a via opening to the conductive line in the second dielectric layer. The via opening lands at least partially on the hard mask to self-align the via opening to the conductive line. A via may be formed by filling the via opening with a conductor.