Post-CMP Cleaning Composition for Ceria Residue Removal
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Solution Overview
Problem
Ceria-based CMP slurries are difficult to remove from microelectronic device wafers due to oppositely charged zeta potentials, leading to residues that cause short circuits and increased electrical resistance.
Innovation Solution
A cleaning composition comprising a reducing agent, chelating agent, amino(C6-C12 alkyl)alcohol, and water with a pH of less than about 8, effectively removing ceria residues from dielectric wafer surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ceria-based CMP slurry is used for polishing, then polishing speed and planarization quality are improved, but residue removal becomes difficult due to oppositely charged zeta potentials
Solution Approach 1:
The cleaning composition uses pH adjustment (maintained below 8) to alter the electrostatic interaction between ceria particles and substrate surfaces. By controlling the pH environment, the zeta potential of ceria particles is modified to reduce attraction to negatively charged surfaces, enabling effective removal while maintaining polishing performance
Solution Approach 2:
The cleaning composition introduces intermediary chemicals including chelating agents (such as EDTA or DTPA) and reducing agents (such as hydroquinone or ascorbic acid) that mediate the interaction between ceria particles and substrate surfaces. These intermediaries form complexes with ceria or modify surface charges, facilitating particle removal without direct mechanical force
2Reliability
If ceria particles remain on wafer after CMP, then electrical reliability deteriorates due to short circuits and increased resistance, but removing them becomes difficult
Solution Approach 1:
The cleaning composition employs intermediary substances including surfactants and chelating agents that act as mediators between ceria particles and the cleaning solution. These intermediaries reduce the adhesion strength between particles and substrate by forming competitive complexes or modifying surface energy, enabling effective removal of electrically harmful residues
Solution Approach 2:
The composition utilizes controlled pH conditions (pH < 8) to change the electrostatic parameters of the system. This pH control modifies the zeta potential of both ceria particles and substrate surfaces, reducing attractive forces and enabling removal of particles that would otherwise cause electrical failures
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 composition achieves improved ceria removal on poly silicon substrates, reducing residues by at least 85-99% without damaging the substrate, preparing a clean surface for further processing.
Implementation Method 1
a reducing agent
Implementation Method 2
a chelating agent
Data Source
AI summary
The invention provides compositions useful in post-CMP cleaning operations where ceria is present. In one aspect, the invention provides a composition comprising a reducing agent; a chelating agent; an amino(C6-C12 alkyl)alcohol; and water; wherein the composition has a pH of less than about 8. The compositions of the invention were found to show improved ceria removal on, for example, poly silicon (poly Si) substrates. Also provided is a method for cleaning a microelectronic device substrate using such compositions and a kit comprising, in one or more containers, selected components of the compositions.