Interconnect Structure with Coplanar Dielectric Cap for Reliability
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Solution Overview
Problem
Conventional interconnect structures face reliability issues due to electromigration (EM) and time-dependent dielectric breakdown (TDDB) in copper interconnects, with metal cap layers causing residual metal residues that can lead to electrical shorts and decreased reliability.
Innovation Solution
The interconnect structure features a metal cap layer directly on a conductive feature embedded in a dielectric layer, with a thicker dielectric cap layer that is coplanar with the metal cap layer's bottom surface, preventing residual metal from extending onto the dielectric layer and thus reducing electrical shorts. This structure includes a method of forming the interconnect by depositing a dielectric cap layer first, exposing the conductive feature, and then selectively forming a thinner metal cap layer that does not extend onto the dielectric surface, ensuring the dielectric cap layer remains thicker and acts as a barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metallic capping layer is used to improve EM resistance, then EM resistance is significantly enhanced, but metallic residues are left on the dielectric surface causing electrical shorts
Solution Approach 1:
The patent extracts the harmful metallic residues from the dielectric surface by introducing a dielectric cap layer that prevents metal diffusion onto the dielectric. The metal cap layer is formed only on the conductive feature surface, and the dielectric cap layer is subsequently deposited to cover any potential metal residues, effectively removing the harmful effect of metal contamination from the dielectric surface.
Solution Approach 2:
The patent introduces a dielectric cap layer as an intermediary between the metal cap layer and the dielectric layer. This intermediate dielectric layer acts as a barrier that prevents direct contact between metal residues and the dielectric, eliminating the harmful effect of metallic residues while preserving the EM protection benefits of the metal cap layer.
2Reliability
If a dielectric capping layer is deposited directly on metal to reduce EM and TDDB, then EM and TDDB are reduced, but a pre-clean process is required that damages the surrounding dielectric material
Solution Approach 1:
The patent performs the dielectric cap layer deposition as a preliminary action before any potential pre-clean process. By depositing the dielectric cap layer first on the as-deposited metal surface, the need for a pre-clean process is eliminated, thus avoiding damage to the surrounding dielectric material while still achieving the desired atomic bonding for EM and TDDB protection.
Solution Approach 2:
The patent inverts the conventional sequence by depositing the dielectric cap layer before performing any cleaning operations. Instead of cleaning the metal surface first and then depositing the dielectric cap, the dielectric cap is deposited on the as-deposited metal surface, reversing the traditional approach and eliminating the harmful pre-clean step.
3Reliability
If the dielectric cap layer is made thicker to prevent metal residue extension, then electrical shorts are reduced, but the overall structure complexity increases
Solution Approach 1:
The patent merges the dielectric cap layer function with the existing dielectric layer structure. The dielectric cap layer is deposited to a thickness greater than the metal cap layer, and its bottom surface is substantially coplanar with the bottom surface of the metal cap layer, integrating smoothly with the existing structure without adding significant complexity.
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 configuration significantly reduces electrical shorts and enhances the reliability of interconnects by breaking continuity between adjacent conductive features, improving both EM and TDDB reliability compared to conventional structures.
Implementation Method 1
a metal cap layer directly on a conductive feature embedded in a dielectric layer
Implementation Method 2
a dielectric cap layer directly on the dielectric layer... provides improved EM and TDDB reliabilities
Implementation Method 3
The dielectric cap layer is thicker than the metal cap layer and has a bottom surface that is substantially coplanar with a bottom surface of the metal cap layer... breaking continuity between adjacent conductive features
Data Source
AI summary
An improved interconnect structure including a dielectric layer having a conductive feature embedded therein, the conductive feature having a first top surface that is substantially coplanar with a second top surface of the dielectric layer; a metal cap layer located directly on the first top surface, wherein the metal cap layer does not substantially extend onto the second top surface; a first dielectric cap layer located directly on the second top surface, wherein the first dielectric cap layer does not substantially extend onto the first top surface and the first dielectric cap layer is thicker than the metal cap layer; and a second dielectric cap layer on the metal cap layer and the first dielectric cap layer. A method of forming the interconnect structure is also provided.