Vacuum CMP With Ionic Liquid Slurry to Suppress Oxidation
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) in an atmospheric environment leads to unintended oxidation of substrate surfaces due to the formation of oxide films, which necessitates additional steps to remove these films, and the use of slurry in a vacuum atmosphere results in excessive polishing rates and loss of cooling effects.
Innovation Solution
A polishing apparatus and method that performs CMP in a vacuum atmosphere using an ionic liquid slurry, where the substrate and pad are pressed together and rotated, with a pressurizing head unit controlling the contact and rotation to suppress oxidation, and a quadrupole mass spectrometer monitors the processing end point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional CMP is performed in atmospheric environment, then polishing can be carried out with standard slurry, but unintended oxidation of substrate surface occurs due to oxide film formation
Solution Approach 1:
The patent performs CMP processing in a vacuum atmosphere instead of atmospheric environment. The processing chamber is evacuated to create a vacuum environment (typically 10^-3 to 10^-6 Pa), which eliminates oxygen and prevents oxidation of the substrate surface during polishing. This allows the substrate to be polished without forming unwanted oxide films that would require additional removal steps.
2Object-affected harmful factors
If slurry is used in vacuum atmosphere, then oxidation is suppressed, but polishing rate becomes excessive and cooling effect is lost
Solution Approach 1:
The patent changes the physical and chemical parameters of the slurry by using ionic liquids instead of conventional aqueous slurries. Ionic liquids have extremely low vapor pressure and do not evaporate in vacuum, allowing them to be used effectively in vacuum CMP. The ionic liquid composition can be tuned to achieve appropriate polishing rates and provide sufficient cooling through its thermal properties, thus controlling the polishing process in vacuum atmosphere.
3Object-affected harmful factors
If slurry is supplied in vacuum atmosphere, then oxidation is prevented, but slurry volatility increases causing processing difficulties
Solution Approach 1:
The patent changes the chemical composition of the slurry from conventional aqueous-based formulations to ionic liquid-based formulations. Ionic liquids have negligible vapor pressure even in vacuum conditions, eliminating evaporation and volatility problems. This parameter change in slurry composition allows for stable slurry supply and consistent polishing performance in vacuum atmosphere without the processing difficulties associated with volatile slurries.
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 suppresses unintended oxidation of substrate surfaces during polishing, maintaining appropriate polishing rates and cooling effects by using ionic liquids that are less volatile in a vacuum, allowing for efficient and controlled planarization without additional film removal steps.
Implementation Method 1
a quadrupole mass spectrometer monitors the processing end point
Implementation Method 2
a pressurizing head unit that is configured to pressurize the substrate holding unit or the pad holding unit, wherein one of the substrate holding unit and the pad holding unit is pressurized such that the substrate and the pad are in contact with each other
Implementation Method 3
the substrate and the pad are relatively rotated in a state where the slurry is supplied
Implementation Method 4
maintaining appropriate polishing rates and cooling effects by using ionic liquids that are less volatile in a vacuum
Implementation Method 5
the substrate and the pad are relatively rotated in a state where the slurry is supplied
Data Source
AI summary
A polishing apparatus includes: a processing container that is configured to provide a processing space in a vacuum atmosphere; a substrate holding unit that is configured to be disposed in the processing container and hold a substrate to be processed; a pad holding unit that is configured to be disposed to face the substrate holding unit and hold a pad; a slurry supply unit that is configured to supply a slurry which is an ionic liquid to a surface of the substrate or the pad; and a pressurizing head unit that is configured to pressurize the substrate holding unit or the pad holding unit, wherein one of the substrate holding unit and the pad holding unit is pressurized such that the substrate and the pad are in contact with each other, and the substrate and the pad are respectively rotated in a state where the slurry is supplied.