Interconnect CMP with Protected Noble Metal Liner Removal
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Solution Overview
Problem
Chemical mechanical polishing (CMP) struggles to efficiently remove noble metal liners from interconnect structures without damaging other metal layers, leading to short-circuit or open-circuit issues due to their inertness and mechanical hardness.
Innovation Solution
A method involving a first CMP operation to expose the noble metal liner, followed by a mixture of a strong oxidant and a protective composition to selectively remove the liner while protecting the underlying conductive layer, and a second CMP operation to remove the conductive layer, allowing for separate removal of the liner and conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CMP is used to remove noble metal liners, then the liner removal efficiency is improved, but the conductive layer is damaged due to the inertness and mechanical hardness of noble metals
Solution Approach 1:
The removal process is segmented into two distinct operations: first removing the noble metal liner, then removing the conductive layer. This segmentation allows each operation to be optimized independently, preventing damage to the conductive layer during liner removal.
Solution Approach 2:
The noble metal liner is removed as a preliminary action before conducting the CMP operation on the conductive layer. This preliminary removal eliminates the hard, inert material that would otherwise interfere with and damage the conductive layer during subsequent polishing.
2Manufacturing precision
If CMP is used to planarize interconnect structures, then surface flatness is improved, but selective removal of different metal layers becomes difficult
Solution Approach 1:
The planarization process is segmented into multiple CMP operations, each targeting a specific layer. The first operation removes the noble metal liner to a first depth, and the second operation removes the conductive layer to a second depth, enabling selective removal while achieving surface flatness.
Solution Approach 2:
Different polishing conditions and parameters are applied locally to different layers during the CMP process. The polishing slurry composition, pressure, and speed are optimized for each specific metal layer being removed, allowing selective removal while maintaining overall surface flatness.
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 short-circuit and open-circuit issues by allowing for the precise removal of noble metal liners without damaging the conductive layers, resulting in a flush and functional interconnect structure.
Implementation Method 1
a mixture of a strong oxidant and a protective composition to selectively remove the liner
Implementation Method 2
form a protecting layer over the conductive layer during the etching of the liner
Implementation Method 3
The relative movement of the polishing pad and the wafer surface coupled with the reactive chemicals in the abrasive slurry allows CMP to level the wafer surface by means of both physical and chemical actions
Implementation Method 4
an abrasive slurry containing both abrasive particles and reactive chemicals is applied to the polishing pad
Data Source
AI summary
A method for CMP includes following operations. A metal stack is received. The metal layer stack includes at least a first metal layer and a second metal layer, and a top surface of the first metal layer and a top surface of the second metal layer are exposed. A protecting layer is formed over the second metal layer. A portion of the first metal layer is etched. The protecting layer protects the second metal layer during the etching of the portion of the first metal layer. A top surface of the etched first metal layer is lower than a top surface of the protecting layer. The protecting layer is removed from the second metal layer.