Polysilicon CMP Slurry Without TMAH for High Selectivity
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Solution Overview
Problem
Commercially available polysilicon CMP slurries rely on tetramethylammonium hydroxide (TMAH), a hazardous and toxic chemical, for high removal rates, necessitating a TMAH-free alternative that maintains high polysilicon removal rates and selectivity to silicon oxide and silicon nitride layers while reducing environmental and health hazards.
Innovation Solution
A water-based chemical mechanical polishing composition containing silica abrasive particles, a nitrogen-containing polysilicon accelerator (such as amino acids or guanidine derivatives), and an alkali metal salt, with a pH range of 10 to 11, and minimal tetraalkylammonium salts, which provides high removal rates and selectivity without TMAH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TMAH is used as chemical accelerator, then polysilicon removal rate is improved, but environmental and health hazards increase
Solution Approach 1:
The patent changes the chemical composition parameters by replacing TMAH with alternative accelerators (amino acids, guanidine derivatives) and adjusts pH to 10-11 using alkali metal salts, achieving high removal rates without hazardous materials
Solution Approach 2:
The patent uses biodegradable, non-hazardous materials (amino acids, guanidine derivatives) that are environmentally friendly and can be safely disposed of, replacing persistent toxic chemicals
2Object-affected harmful factors
If TMAH-free composition is used, then environmental safety is improved, but polysilicon removal rate may decrease
Solution Approach 1:
The patent optimizes pH to 10-11 using alkali metal salts and selects specific accelerators (amino acids, guanidine derivatives) to achieve high polysilicon removal rates without TMAH
Solution Approach 2:
The patent introduces nitrogen-containing compounds (amino acids, guanidine derivatives) as intermediary substances that facilitate polysilicon removal through chemical interaction, replacing TMAH's function without its toxicity
3Quantity of substance
If alternative accelerator is used, then TMAH content is reduced, but selectivity to silicon oxide and silicon nitride may be affected
Solution Approach 1:
The patent carefully controls pH (10-11) and accelerator concentration to achieve high selectivity to silicon oxide and silicon nitride while maintaining low tetraalkylammonium salt content (<500 ppm)
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 high polysilicon removal rates and selectivity to silicon oxide and silicon nitride, while being environmentally friendly and reducing human health hazards, as it is substantially free of tetraalkylammonium compounds.
Implementation Method 1
about 0.1 to about 3 weight percent silica abrasive particles dispersed in the liquid carrier
Implementation Method 2
about 0.05 to about 1 weight percent of a polysilicon accelerator, the polysilicon accelerator selected from the group consisting of an amino acid, a guanidine derivative, and mixtures thereof
Implementation Method 3
an alkali metal salt. The composition comprises less than about 500 ppm by weight tetraalkylammonium salts and has a pH in a range from about 10 to about 11
Data Source
AI summary
A chemical mechanical polishing composition for polishing a substrate having a polysilicon layer includes a water based liquid carrier, a silica abrasive, an amino acid or guanidine derivative containing polysilicon polishing accelerator, and an alkali metal salt. The composition includes less than about 500 ppm tetraalkylammonium salt and has a pH in a range from about 10 to about 11.