Air Gap Dielectric Capping for BEOL Interconnect Reliability
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Solution Overview
Problem
Current Cu-based interconnect structures in semiconductor devices face reliability issues due to a mechanically weak interface at the cap/dielectric/barrier interface, leading to diffusion of conductive material into the dielectric, which degrades circuit reliability and increases process complexity.
Innovation Solution
The introduction of an air gap within the dielectric material between the diffusion barrier and the capping layer, which enhances mechanical strength and dielectric breakdown resistance, is achieved through existing interconnect processing steps without additional cost or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous dielectric material is used between the diffusion barrier and capping layer, then the dielectric material provides electrical insulation, but the interface remains mechanically weak and prone to conductive material diffusion
Solution Approach 1:
The dielectric layer is segmented into two distinct parts: a first dielectric material directly contacting the conductive material and diffusion barrier, and a second dielectric material forming the capping layer. This segmentation creates a controlled interface architecture that improves mechanical strength while preventing conductive material diffusion through the engineered boundary between the two dielectric materials.
2Ease of manufacture
If the diffusion barrier is made thinner to reduce process complexity, then manufacturing is easier, but conductive material can more easily diffuse into the dielectric
Solution Approach 1:
The first dielectric material acts as an intermediary layer between the diffusion barrier and the second dielectric material. This intermediary structure provides an additional protective boundary that enhances diffusion prevention capabilities, allowing the diffusion barrier itself to be optimized for manufacturing ease while the overall system maintains high reliability through the layered dielectric architecture.
3Speed
If copper interconnects are used to increase signal transmission speed, then performance improves, but mechanical weakness at interfaces and diffusion issues arise
Solution Approach 1:
The patent employs a composite dielectric structure with two different dielectric materials, each potentially having different mechanical and electrical properties. This composite approach allows optimization of the interface region for mechanical strength and diffusion resistance, thereby supporting the use of copper interconnects for high-speed signaling while mitigating the reliability issues associated with copper diffusion and interface weakness.
Data Source
AI summary
A semiconductor interconnect structure is provided that includes a new capping layer/dielectric material interface which is embedded inside the dielectric material. In particular, the new interface is an air gap that is located in the upper surface of a dielectric material that is adjacent to a conductive region or feature. The air gap may be unfilled, partially filled or completely filled with either a dielectric capping layer or an upper dielectric material. The presence of the air gap in the upper surface of the dielectric material that is adjacent to the conductive region or feature provides a new interface that has a high mechanical strength and thus the resultant structure is highly reliable. Moreover, the new interface provided in the present invention has a high dielectric breakdown resistance which is important for future technology extendibility. Moreover, it is noted that the new interface is provided utilizing processing steps that are compatible with existing interconnect technology without added cost.