Polishing Liquid Selectivity via Onium Salt Zeta Potential
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing chemical mechanical polishing (CMP) methods face challenges in achieving high selectivity for silicon oxide over silicon nitride while minimizing defects such as scratches on the polishing surface, particularly when using polishing liquids with colloidal silica.
Innovation Solution
A polishing liquid comprising colloidal silica and an onium salt with a cation, where the onium salt content is greater than 0.01% by mass, and the zeta potential of colloidal silica is 15 mV or more, along with a pH of 2 to 4 and electrical conductivity of 10 μS/cm, is used to enhance selectivity and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If polishing liquid including colloidal silica is used to increase polishing speed for silicon nitride, then polishing speed for silicon nitride is improved, but selectivity of silicon oxide polishing with respect to silicon nitride becomes small and defects are generated on polishing target surface
Solution Approach 1:
The patent changes the chemical parameters of the polishing liquid by adding an onium salt containing a cation, which modifies the zeta potential of colloidal silica to 15 mV or more. This parameter change enables selective polishing of silicon oxide over silicon nitride while maintaining high polishing speed and reducing defects on the polishing target surface
Solution Approach 2:
The patent creates a composite polishing liquid system by combining colloidal silica with an onium salt. This composite formulation achieves synergistic effects where the onium salt enhances the polishing performance and selectivity without compromising the base colloidal silica's polishing capability
2Speed
If polishing liquid including colloidal silica is used to increase polishing speed for silicon nitride, then polishing speed for silicon nitride is improved, but defects are generated on polishing target surface
Solution Approach 1:
The patent adjusts the zeta potential parameter of colloidal silica to 15 mV or more through the addition of onium salt. This parameter optimization reduces harmful defects on the polishing target surface while preserving the high polishing speed capability for silicon nitride
3Speed
If polishing liquid including colloidal silica is used, then polishing speed for silicon oxide can be increased, but selectivity of silicon oxide polishing with respect to silicon nitride becomes small
Solution Approach 1:
The patent optimizes the chemical parameters by introducing an onium salt that raises the zeta potential of colloidal silica to 15 mV or more. This parameter adjustment enables the polishing liquid to achieve both high polishing speed for silicon oxide and high selectivity with respect to silicon nitride simultaneously
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 configuration significantly improves the selectivity of silicon oxide polishing over silicon nitride, reduces defects like scratches, and maintains the temporal stability of the polishing liquid.
Implementation Method 1
a zeta potential of the colloidal silica measured in a state where the colloidal silica is present in the polishing liquid is 15 mV or more
Data Source
AI summary
A polishing liquid is used for chemical mechanical polishing and includes colloidal silica; and an onium salt containing a cation, in which a content of the onium salt is more than 0.01% by mass, a zeta potential of the colloidal silica measured in a state where the colloidal silica is present in the polishing liquid is 15 mV or more, an electrical conductivity is 10 μS/cm or more, and a pH is 2 to 4.