Air Gap Interconnects for Low Capacitance BEOL Reliability
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Solution Overview
Problem
Current interconnect structures in semiconductor device fabrication face challenges in achieving high reliability and reduced capacitance, particularly in the back-end-of-line (BEOL) metallization using low-k dielectric materials.
Innovation Solution
The method involves forming a sacrificial layer on a substrate, creating interconnect openings, filling them with a conductor, and then removing the sacrificial layer to create an air gap layer between the dielectric layer and the substrate, resulting in a conductive feature that extends through the air gap, which reduces the effective dielectric constant and enhances reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low-k dielectric materials are used in BEOL metallization, then capacitance is reduced, but reliability deteriorates due to crack propagation risks
Solution Approach 1:
The dielectric layer is segmented into multiple low-k dielectric layers separated by air gap layers. This segmentation prevents crack propagation across the entire interconnect structure by creating discontinuities in the dielectric path, thereby maintaining reliability while preserving the low capacitance benefits of low-k materials.
Solution Approach 2:
Air gap layers with porous or hollow structures are introduced between solid dielectric layers. These air gaps have permittivity near unity, significantly reducing the effective dielectric constant of the interconnect structure and thus lowering capacitance while providing crack propagation barriers.
2Loss of energy
If air gap layers are introduced to reduce capacitance, then device complexity increases
Solution Approach 1:
Air gap layers are formed as part of the dielectric layer deposition process itself, rather than as a separate subsequent step. The sacrificial layer is removed after dielectric deposition, creating air gaps in-situ. This preliminary integration reduces process complexity compared to forming air gaps through separate etching or deposition steps.
Solution Approach 2:
A sacrificial layer is used as an intermediary material that is deposited conformally with the dielectric layers, then removed to create air gaps. This intermediary approach simplifies the overall process by using a single sacrificial material system rather than requiring complex direct air gap formation techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively lowers the capacitance and improves the reliability of interconnect structures by creating an air gap layer with a permittivity near unity, reducing the risk of crack propagation and enhancing package-level reliability testing.
Implementation Method 1
creating an air gap layer with a permittivity near unity, reducing the risk of crack propagation
Data Source
AI summary
Interconnect structures and methods for forming an interconnect structure. A sacrificial layer is formed on a substrate and an interconnect opening is formed that extends vertically through the sacrificial layer into the substrate. The interconnect opening is filled with a conductor to form a conductive feature. After filling the interconnect opening with the conductor, a dielectric layer is formed on the sacrificial layer. After the dielectric layer is formed on the sacrificial layer, the sacrificial layer is removed to form an air gap layer arranged vertically between the dielectric layer and the substrate.