Polishing Composition Selective Silicon Nitride Rate
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Solution Overview
Problem
Conventional polishing liquids for semiconductor manufacturing fail to selectively polish silicon compounds like silicon nitride or silicon dioxide while limiting the polishing rate of elemental silicon, such as polysilicon, due to poor washing efficiency and residual nonionic additives.
Innovation Solution
A polishing composition comprising abrasives, an organic acid, and its conjugate base, with a pH range that controls the polishing rate of elemental silicon, using silica with immobilized organic acid and specific salt forms to enhance dispersion stability and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional polishing liquid containing nonionic additive is used, then silicon compound can be polished, but washing efficiency is poor and nonionic additive remains after polishing
Solution Approach 1:
The invention removes the nonionic additive component from the polishing liquid formulation entirely, replacing it with an ionic surfactant system that provides both polishing and washing functions without leaving harmful residues on the polysilicon surface
Solution Approach 2:
The invention changes the chemical nature of the surfactant from nonionic to ionic (specifically anionic or cationic surfactants), which fundamentally alters the washing properties and eliminates the residue problem while maintaining polishing effectiveness
2Productivity
If polishing liquid is designed to polish silicon compound quickly, then silicon compound polishing rate increases, but elemental silicon polishing rate is not sufficiently limited
Solution Approach 1:
The invention optimizes the pH range of the polishing liquid to be between 2.0 and 6.0, which creates a chemical environment that selectively attacks silicon compounds (nitride, oxide) while significantly reducing the etching rate of elemental silicon (polysilicon), thereby achieving high selectivity
Solution Approach 2:
The invention uses a composite formulation combining ionic surfactant, organic acid, and abrasive particles that work synergistically to achieve differential polishing rates between silicon compounds and elemental silicon, with the ionic surfactant providing both dispersion and selective chemical interaction
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 effectively limits the polishing rate of elemental silicon while allowing for high-rate polishing of silicon compounds, improving washing efficiency and reducing surface defects.
Implementation Method 1
an organic acid and a conjugate base of the organic acid... the polishing composition may have a value of pH that is equal to or higher than a value smaller than the value of pKa of the organic acid by 1.0 unit and that is equal to or lower than a value larger than the value of pKa by 1.5 units
Implementation Method 2
abrasives... the abrasives may be silica with an organic acid immobilized to a surface of the silica
Implementation Method 3
the abrasives may be silica with an organic acid immobilized to a surface of the silica
Data Source
AI summary
There are provided a polishing composition and a method for polishing capable of, when a substrate including polysilicon is polished, limiting the polishing rate of the polysilicon, and selectively polishing a silicon compound other than the polysilicon, such as silicon nitride. The polishing composition used includes abrasives, an organic acid and a conjugate base of the organic acid.