Self-Aligned Subtractive Vias with Scaffolding Support
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Solution Overview
Problem
The formation of top vias in back-end-of-line (BEOL) interconnect structures faces challenges due to the structural instability of via hardmasks, leading to defects such as missing or unwanted vias and pattern collapse.
Innovation Solution
The use of a via hardmask supported by scaffolding provides structural stability, where the via hardmask material acts as both a hardmask for recessing metal lines and scaffolding to prevent collapse, ensuring self-aligned top vias are formed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If via hardmasks are made tall and narrow to achieve self-aligned top vias, then via alignment precision is improved, but structural stability deteriorates causing pattern collapse
Solution Approach 1:
A scaffolding structure made of via hardmask material is introduced as an intermediary element between the substrate and the via hardmask. This scaffolding provides mechanical support to the tall and narrow via hardmask, preventing pattern collapse while maintaining the via alignment precision achieved through the self-aligned process.
Solution Approach 2:
The via hardmask formation process is segmented into multiple steps: first forming the scaffolding structure, then forming the via hardmask on top of it. This segmentation allows the via hardmask to be supported during critical processing steps while maintaining its tall and narrow geometry for precise via alignment.
2Reliability
If via hardmasks are made tall to prevent interface formation between metal lines and top vias, then via isolation is improved, but structural stability worsens leading to pattern collapse
Solution Approach 1:
The scaffolding acts as a mediator that provides the necessary structural support to enable the formation of tall via hardmasks. This allows complete via isolation to be achieved without the via hardmask collapsing during the etching process.
Solution Approach 2:
The scaffolding is formed preliminarily before the via hardmask is deposited. This preliminary action provides a stable foundation that enables subsequent via hardmask formation to achieve the required height for proper via isolation.
3Manufacturing precision
If via hardmasks are made narrow to achieve precise via patterning, then patterning precision is improved, but structural stability deteriorates causing via hardmask collapse
Solution Approach 1:
The scaffolding serves as a mediator that compensates for the reduced structural stability inherent in narrow via hardmasks. By providing external support, the scaffolding enables the via hardmask to maintain its narrow geometry for precise patterning without collapsing.
Solution Approach 2:
The structure is segmented into two functional parts: the scaffolding that provides structural stability and the via hardmask that provides patterning precision. This segmentation allows each component to be optimized independently for its specific function.
Data Source
AI summary
Techniques for forming self-aligned subtractive top vias using a via hardmask supported by scaffolding are provided. In one aspect, a method of forming top vias includes: forming metal lines on a substrate using line hardmasks; patterning vias in the line hardmasks; filling the vias and trenches in between the metal lines with a via hardmask material to form via hardmasks and a scaffolding adjacent to and supporting the via hardmasks; removing the line hardmasks; and recessing the metal lines using the via hardmasks to form the top vias that are self-aligned with the metal lines. The scaffolding can also be placed prior to patterning of the vias in the line hardmasks. A structure formed in accordance with the present techniques containing top vias is also provided.