Semiconductor Copper Interconnect Metal Cap Layer Electromigration
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Solution Overview
Problem
Copper interconnections in semiconductor structures face electromigration issues due to high migration mobility of copper atoms, leading to device instability and increased leakage current, which existing methods fail to adequately address.
Innovation Solution
A semiconductor fabrication method involving the formation of a metal barrier layer with a dense texture and uniform thickness on top of a copper metal layer, followed by conversion into a self-aligned metal cap layer using a silicon-containing gas, to prevent copper and silicon atom diffusion and enhance electromigration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper interconnection is used to replace aluminum interconnection, then electrical resistivity is reduced and electromigration resistance is improved, but copper atom diffusion into silicon and dielectric materials increases causing device instability
Solution Approach 1:
A metal barrier layer is introduced as an intermediary between the copper interconnection layer and the silicon/dielectric materials. This barrier layer prevents copper atoms from diffusing into the substrate while maintaining the low resistivity and electromigration resistance benefits of copper interconnections.
Solution Approach 2:
The patent uses a composite structure combining copper interconnection layer with a metal barrier layer. The composite material approach allows the system to benefit from copper's excellent electrical properties while the barrier layer provides protection against copper diffusion, resolving the contradiction between reliability improvement and harmful diffusion effects.
2Object-affected harmful factors
If copper atoms diffuse into semiconductor substrate or dielectric layer, then electromigration increases causing circuit failure, but the metal barrier layer needs to be dense and uniform to prevent this diffusion
Solution Approach 1:
The metal barrier layer is formed in advance before the copper interconnection layer is deposited. This preliminary action ensures that the barrier layer is already in place to prevent copper diffusion, and its uniformity is established before subsequent processing steps that might affect the copper layer.
Solution Approach 2:
The patent optimizes the parameters of the metal barrier layer including its thickness, composition, and density to achieve the right balance between preventing copper diffusion and maintaining manufacturability. By carefully controlling these parameters, the barrier layer becomes dense and uniform enough to prevent electromigration while remaining feasible to manufacture.
3Reliability
If a metal barrier layer is formed to prevent copper diffusion, then electromigration resistance is improved, but the fabrication process complexity increases
Solution Approach 1:
The formation of the metal barrier layer is merged with existing fabrication process steps such as sputtering or atomic layer deposition that are already used for other layers in the semiconductor structure. This integration reduces the overall process complexity by combining multiple functions into established process flows rather than introducing entirely new manufacturing steps.
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
The method effectively reduces electromigration and electrical resistance issues in semiconductor structures by forming a dense and uniform metal cap layer that prevents copper atom migration and silicon atom diffusion, thereby improving the reliability and performance of the semiconductor structure.
Implementation Method 1
converting the metal barrier layer to a metal cap layer by introducing a silicon-containing gas onto a surface of the metal barrier layer
Implementation Method 2
removing the portion of the metal layer formed above the top surface of the dielectric layer by polishing
Implementation Method 3
removing the metal oxide layer from the top surface of the metal layer
Data Source
AI summary
A method for fabricating a semiconductor structure includes providing a dielectric layer on a semiconductor substrate, forming an opening in the dielectric layer to expose a portion of the surface of the semiconductor substrate, forming a metal layer to fill up the opening, and removing the portion of the metal layer formed above the top surface of the dielectric layer by polishing. A metal oxide layer is formed on the surface of the metal layer after polishing. The method further includes removing the metal oxide layer from the top surface of the metal layer, forming a metal barrier layer on the top surface of the metal layer after the removal of the metal oxide layer to provide a more uniform thickness and a denser texture, and converting the metal barrier layer to a metal cap layer by introducing a silicon-containing gas onto a surface of the metal barrier layer.