Selective Silicon Carbide Polishing via Acidic Slurry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional chemical-mechanical polishing (CMP) techniques struggle to selectively remove silicon carbide from semiconductor wafers without also removing silicon dioxide, leading to poor polishing rates and manufacturing yields due to the hardness and chemical inertness of silicon carbide.
Innovation Solution
A CMP method using an aqueous polishing composition with particulate silica abrasive and an acidic buffering agent, maintaining a pH between 2 and 7, which selectively abrades silicon carbide at a higher rate than silicon dioxide, thereby enhancing the removal rate and selectivity for silicon carbide over silicon dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP techniques are used to remove silicon carbide, then the polishing process can proceed, but the removal rate is slow and silicon dioxide is also removed unintentionally
Solution Approach 1:
The patent applies parameter changes by adjusting the pH of the polishing composition to a specific range (2-7) and controlling the particle size distribution of the abrasive material. These parameter changes enable selective removal of silicon carbide while preserving silicon dioxide, resolving the contradiction between removal rate and selectivity.
Solution Approach 2:
The patent uses a composite abrasive system consisting of multiple particle size fractions (fine particles for selective chemical-mechanical action and coarse particles for mechanical abrasion). This composite approach enables simultaneous achievement of high removal rate and high selectivity by combining different mechanisms.
2Productivity
If the polishing composition is made more aggressive to increase silicon carbide removal rate, then productivity improves, but selectivity deteriorates and silicon dioxide is removed
Solution Approach 1:
The patent applies local quality by creating a multi-modal particle size distribution where fine particles (0.01-10 micrometers) provide selective chemical-mechanical action on silicon carbide, while coarse particles (10-100 micrometers) provide mechanical abrasion. Each particle size fraction performs a localized function that contributes to overall selectivity and productivity.
Solution Approach 2:
The patent controls the pH parameter within a specific range (2-7) to optimize the chemical activity of the polishing composition. This parameter control ensures that the composition is aggressive enough to remove silicon carbide rapidly but not so aggressive as to remove silicon dioxide, resolving the contradiction between productivity and harmful effects.
3Manufacturing precision
If the polishing composition is made gentle to preserve silicon dioxide, then selectivity improves, but the removal rate of silicon carbide becomes too slow
Solution Approach 1:
The patent employs a composite abrasive system with multiple particle size fractions that work synergistically. The fine particles ensure selectivity through chemical-mechanical action, while the coarse particles ensure adequate removal rate through mechanical abrasion. This composite approach resolves the contradiction between selectivity and productivity.
Solution Approach 2:
The patent applies preliminary action by using fine abrasive particles to chemically activate and pre-soften the silicon carbide surface before the coarse particles perform the main removal. This preliminary chemical action enables the subsequent mechanical abrasion to proceed rapidly while maintaining selectivity.
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 achieves a significantly higher removal rate for silicon carbide compared to silicon dioxide, with a selectivity ratio that can be tuned by adjusting pH, buffering agent concentration, and abrasive composition, resulting in improved manufacturing yields and selective removal of silicon carbide.
Implementation Method 1
Compositions and methods for chemical-mechanical polishing (CMP) of the surface of a substrate are well known in the art.
Implementation Method 2
The relative movement of the pad and substrate serves to abrade the surface of the substrate to remove a portion of the material from the substrate surface
Implementation Method 3
at least one acidic buffering agent providing a pH in the range of about 2 to about 7
Data Source
AI summary
The present invention provides a method for selectively removing silicon carbide from the surface of a substrate in preference to silicon dioxide. The method comprises abrading a surface of substrate with a polishing composition that comprises a particulate abrasive, at least one acidic buffering agent, and an aqueous carrier.