Metal Interconnect Cap Layer Thickness for Continuous Via Conductors
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Solution Overview
Problem
The copper dual damascene process in semiconductor fabrication often results in discontinuous copper metal lines near the bottom of via conductors and trench conductors due to etching, affecting device performance.
Innovation Solution
A method involving forming a first metal interconnection in an IMD layer, a cap layer, and a second IMD layer, followed by a first etching process to create an opening, a plasma treatment to remove polymers, and a second etching process to refine the cap layer, resulting in a cap layer with multiple thicknesses and maintaining continuity, allowing for air gaps and improved electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a standard etching process is used to form openings in the dual damascene process, then the opening can be formed efficiently, but the cap layer becomes discontinuous at the bottom of via conductors and trench conductors, affecting device performance
Solution Approach 1:
A planarization layer is formed over the first inter-metal dielectric layer before the etching process. This preliminary action protects the cap layer during etching, preventing discontinuities while allowing efficient opening formation. The planarization layer is subsequently removed after serving its protective function.
Solution Approach 2:
The planarization layer acts as an intermediary protective layer between the etching process and the cap layer. It mediates the interaction by absorbing the harmful effects of etching on the cap layer, thereby maintaining cap layer continuity while enabling efficient etching of the inter-metal dielectric layer.
2Reliability
If the cap layer thickness is increased to ensure continuity, then reliability improves, but the fabrication process complexity increases
Solution Approach 1:
The protective function is segmented from the cap layer itself and assigned to a separate planarization layer. This allows the cap layer to maintain its original thickness without requiring increased thickness for protection, thereby avoiding additional fabrication complexity while ensuring reliability.
Solution Approach 2:
By introducing the planarization layer as an intermediary, the system protects the cap layer without modifying the cap layer's intrinsic properties or thickness. This intermediary approach solves the reliability issue without increasing fabrication process complexity.
3Reliability
If the cap layer is made thicker to prevent electrical migration, then device reliability improves, but the manufacturing precision requirements increase
Solution Approach 1:
The electrical migration protection function is segmented from the cap layer and assigned to the planarization layer. This allows the cap layer to maintain precise, thin dimensions without compromising reliability, thereby reducing manufacturing precision requirements while still preventing electrical migration.
Solution Approach 2:
The planarization layer serves as an intermediary that provides electrical migration protection without requiring the cap layer to be thicker. This intermediary approach maintains strict thickness control of the cap layer while achieving the desired reliability.
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 enhances the reliability of metal interconnects by maintaining a continuous cap layer with varying thicknesses, reducing electrical migration effects and improving device performance.
Implementation Method 1
performing a plasma treatment process
Data Source
AI summary
A metal interconnect structure includes a first metal interconnection in an inter-metal dielectric (IMD) layer on a substrate, a second metal interconnection on the first metal interconnection, and a cap layer between the first metal interconnection and the second metal interconnection. Preferably, a top surface of the first metal interconnection is even with a top surface of the IMD layer and the cap layer is made of conductive material.