Self-Aligned Air Gaps in Back-End Interconnects
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Solution Overview
Problem
Integrated circuit structures face capacitive coupling issues due to closely spaced wiring lines, which slow down data transmission rates and increase energy consumption, and the use of air gaps to reduce this coupling is limited by misaligned vias and unlanded via issues, particularly in higher via density areas.
Innovation Solution
The formation of interconnect structures as monoliths of both wiring lines and vias, where the vias are self-aligned and exposed during trench formation, allowing for the introduction of air gaps between adjacent wiring lines, reducing the risk of unlanded vias and enhancing interconnect reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If air gaps are introduced between adjacent wiring lines to reduce capacitive coupling, then data transmission rates improve and energy consumption decreases, but unlanded vias can cause shorting or reduce shorting margin
Solution Approach 1:
The method performs preliminary alignment by forming via openings that are self-aligned to the wiring lines through the trench formation process. The vias are positioned before the air gap is fully established, ensuring they land correctly on the lower wiring lines and preventing unlanded via issues that would otherwise occur with air gap formation
Solution Approach 2:
The patent uses masks as intermediary elements to control the air gap formation process. The masks are strategically placed to prevent air gap formation in areas where vias are present, while allowing air gaps to form in regions where they are beneficial for reducing capacitive coupling. This intermediary approach reconciles the conflicting requirements of air gap benefits and via alignment safety
2Reliability
If masks are used to prevent air gap formation near vias, then unlanded via issues are avoided, but the implementation of air gaps is limited particularly in lower interconnect levels with higher via density
Solution Approach 1:
The via alignment process is made self-service through self-alignment mechanisms. The trench formation process automatically positions via openings relative to the wiring lines without requiring separate alignment steps or complex mask patterns. This self-aligning approach eliminates the need for masks in many cases and provides consistent via placement even in high-density areas
Solution Approach 2:
The patent changes the parameter of via opening formation from a separate photolithography step to an integrated part of the trench formation process. By forming via openings concurrently with trench formation using the same etch process, the method achieves precise via placement without requiring additional masks, thereby increasing adaptability to high via density scenarios
Data Source
AI summary
A method including patterning a thickness dimension of an interconnect material into a thickness dimension for a wiring line with one or more vias extending from the wiring line and introducing a dielectric material on the interconnect material. A method including depositing and patterning an interconnect material into a wiring line and one or more vias; and introducing a dielectric material on the interconnect material such that the one or more vias are exposed through the dielectric material. An apparatus including a first interconnect layer in a first plane and a second interconnect in a second plane on a substrate; and a dielectric layer separating the first and second interconnect layers, wherein the first interconnect layer comprises a monolith including a wiring line and at least one via, the at least one via extending from the wiring line to a wiring line of the second interconnect layer.