Ultra Low-k Interconnects Erosion Mitigation via Barrier Layers
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Solution Overview
Problem
The reliability of metal interconnects in porous ultra low-k dielectrics is compromised due to severe erosion during etch-back, leading to 'fangs' or deep trenches, which expose metal and cause time-dependent dielectric breakdown and electromigration failures, as current methods fail to provide adequate liner coverage.
Innovation Solution
A thin metallic or dielectric layer is introduced underneath the line trench before liner deposition, preventing trench erosion and ensuring proper via embedment, and a method involving a blanket reactive ion etch process is used to remove the original dielectric interface and fill with a fresh ultra low-k dielectric layer, reducing debris and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blanket reactive ion etch process is used to remove the original dielectric interface and fill with a fresh ultra low-k dielectric layer, then debris is reduced and reliability is enhanced, but the process complexity and manufacturing steps increase
Solution Approach 1:
The patent applies preliminary action by performing a blanket reactive ion etch process before filling the ultra low-k dielectric layer. This etching step pre-cleans the interface and removes potential contamination sources, ensuring a clean substrate for the subsequent dielectric fill process, which ultimately improves interconnect reliability
Solution Approach 2:
The patent extracts and removes the original dielectric interface through the blanket reactive ion etch process. By taking out the potentially contaminated original interface layer, the process eliminates a source of debris and reliability issues, allowing a fresh ultra low-k dielectric layer to be deposited on a clean surface
2Speed
If porosity is introduced in insulators to reduce capacitance, then signal propagation delay is reduced, but electromigration lifetime of wide-line interconnects deteriorates due to severe erosion during etch-back
Solution Approach 1:
The patent applies beforehand cushioning by depositing a thin barrier layer before forming the ultra low-k dielectric layer. This barrier layer acts as a protective cushion during subsequent etch-back processes, preventing severe erosion of the porous dielectric material and protecting the underlying metal interconnects from exposure, thereby extending electromigration lifetime while maintaining the speed benefits of porosity
Solution Approach 2:
The patent uses composite materials by combining a thin barrier layer with the porous ultra low-k dielectric material. The barrier layer provides mechanical strength and erosion resistance, while the porous dielectric provides low capacitance, creating a composite structure that achieves both high speed signal propagation and long electromigration lifetime
3Reliability
If a thin barrier layer is deposited before ultra low-k dielectric to prevent erosion, then liner coverage is improved and reliability increases, but the device complexity and number of deposition steps increase
Solution Approach 1:
The patent applies local quality by depositing a thin barrier layer specifically at the interface where erosion occurs, rather than uniformly thickening the entire dielectric structure. This localized approach provides targeted protection where needed, improving liner coverage and reliability, while minimizing the addition of structural complexity and maintaining the overall simplicity of the interconnect architecture
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 significantly improves the yield and reliability of interconnects by preventing metal leakage and extending electromigration lifetime, while minimizing time-dependent dielectric breakdown and time-zero leakage failures.
Implementation Method 1
a thin layer formed on the dielectric layer, the thin layer separating the dielectric layer from the contact line
Implementation Method 2
a method involving a blanket reactive ion etch process is used to remove the original dielectric interface
Data Source
AI summary
A metal interconnect structure in ultra low-k dielectrics is described having a capped interconnect layer; an interconnect feature with a contact via and a contact line formed in a dielectric layer, where the via is partially embedded into the interconnect layer; and a thin film formed on the dielectric layer and separating the dielectric layer from the contact line. A method of fabricating the interconnect structure is also described and includes forming a first dielectric on a capped interconnect element; forming a thin film over the first dielectric; forming a second dielectric on the thin film; forming a via opening on the second dielectric, the thin film and extending into the first dielectric; forming a line trench on a portion of the second dielectric; and filling the via opening and the line trench with a conductive material for forming a contact via and a contact line, where the contact via is partially embedded in the interconnect element.