Interconnect CMP with Protective Layer for Noble Metal Liner Removal
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) methods face challenges in removing noble metal liners from interconnect structures without damaging other metal layers, leading to issues like short circuits and open circuits due to the inertness and mechanical hardness of these metals.
Innovation Solution
A two-step CMP process is employed, where a first composition with a strong oxidant is used to selectively remove the noble metal liner while a second composition forms a protecting layer over the conductive metal layers, allowing for the separate removal of the liner and conductive layer without damaging the copper layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single CMP process is used to remove noble metal liners, then the liner removal is attempted, but the inertness and mechanical hardness of noble metals cause damage to other metal layers leading to short circuits and open circuits
Solution Approach 1:
The patent divides the CMP process into two separate sequential steps: (1) a first CMP process using a first slurry to remove the noble metal liner, and (2) a second CMP process using a second slurry to remove the conductive layer. This segmentation allows each process to be optimized for its specific target material, preventing damage to other metal layers while achieving complete liner removal.
Solution Approach 2:
The patent employs different slurry compositions tailored to specific removal needs: the first slurry contains abrasive particles and chemicals optimized for removing noble metal liners, while the second slurry is optimized for removing conductive layers. This local quality approach ensures precise control over what each CMP step removes without affecting other structures.
2Manufacturing precision
If CMP is used to planarize interconnect structures, then a flush surface is achieved, but the inertness of noble metal liners prevents their complete removal without damaging underlying copper layers
Solution Approach 1:
The patent performs a preliminary CMP step using the first slurry to remove the noble metal liner before attempting to remove the conductive layer. This preliminary action prepares the surface by eliminating the inert liner material that would otherwise protect underlying structures from complete removal in subsequent CMP steps.
Solution Approach 2:
The patent changes key parameters between the two CMP steps: using different slurry compositions, abrasive particle sizes, and process conditions optimized for each removal task. The first CMP uses parameters suitable for noble metal removal, while the second CMP uses parameters optimized for conductive layer removal, enabling precise control over the planarization process.
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 mitigates the issues of short and open circuits by allowing for the precise removal of noble metal liners while protecting the conductive layers, resulting in a flush and functional interconnect structure.
Implementation Method 1
a first composition with a strong oxidant is used to selectively remove the noble metal liner
Implementation Method 2
a second composition forms a protecting layer over the conductive metal layers
Data Source
AI summary
A method for CMP includes following operations. A first metal layer and a second metal layer are formed in a dielectric structure. The second metal layer is formed over a portion of the first metal layer. A first composition is provided to remove a portion of the first metal layer. A second composition is provided to form a protecting layer over the second metal layer. The protecting layer is removed to expose the second metal layer. A CMP operation is performed to remove a portion of the first metal layer, a portion of the second metal layer and a portion of the dielectric structure.