Boron-Polysilicon CMP Composition for High Selectivity Polishing
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Solution Overview
Problem
Existing polishing compositions struggle to achieve high removal rates and selectivity for boron-polysilicon layers, while also requiring precise control over the removal rates of silicon nitride, silicon oxide, and titanium nitride in the fabrication of advanced memory devices.
Innovation Solution
A chemical-mechanical polishing composition comprising α-alumina, silica, ferric ion, and organic acid, with a pH of 2 to 4, along with optional nitrogen-containing compounds and surfactants, is used to polish substrates, providing high removal rates for boron-polysilicon and low removal rates for silicon nitride and silicon oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polishing compositions are used, then polishing can be performed, but high removal rate for boron-polysilicon cannot be achieved
Solution Approach 1:
The polishing composition uses pH as a critical parameter, maintaining a pH of 2-4 to optimize the removal rate of boron-doped polysilicon while controlling the removal rates of other materials. This parameter change enables high productivity for boron-polysilicon removal while maintaining selectivity for stopping layers.
Solution Approach 2:
The polishing composition combines multiple components including abrasive particles, ferric ion, organic acid, and nitrogen-containing compounds in a synergistic formulation. This composite approach enables simultaneous achievement of high removal rate for boron-polysilicon and controlled removal rates for silicon nitride and silicon oxide, resolving the contradiction between productivity and selectivity.
2Productivity
If high removal rate for boron-polysilicon is achieved, then productivity improves, but control over removal rates of silicon nitride and silicon oxide becomes difficult
Solution Approach 1:
The composition maintains pH between 2-4, which is optimized to enhance removal rate of boron-doped polysilicon while simultaneously suppressing excessive removal of silicon nitride and silicon oxide stopping layers, thus achieving both high productivity and manufacturing precision.
Solution Approach 2:
Ferric ion acts as an intermediary in the polishing composition, facilitating selective chemical-mechanical removal of boron-polysilicon while having minimal impact on silicon nitride and silicon oxide, thereby enabling differential removal rates for different materials in the film stack.
3Manufacturing precision
If selectivity for boron-polysilicon is enhanced, then manufacturing precision improves, but removal rate may be reduced
Solution Approach 1:
By optimizing pH to the range of 2-4 and adjusting concentrations of ferric ion and organic acid, the composition achieves a balance where selectivity for boron-polysilicon is enhanced without sacrificing removal rate, unlike conventional compositions that must trade one for the other.
Solution Approach 2:
The synergistic combination of multiple polishing agents including abrasive particles, ferric ion, organic acid, and nitrogen-containing compounds creates a composition that simultaneously achieves high selectivity for boron-polysilicon and maintains high removal rate, resolving the typical trade-off between these parameters.
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 removal rates for boron-polysilicon and low removal rates for silicon nitride and silicon oxide, enhancing the fabrication process of advanced memory devices by ensuring selective polishing.
Implementation Method 1
chemical-mechanical polishing composition comprising: (a) an abrasive selected from α-alumina, silica, and a combination thereof, (b) ferric ion, an organic acid, or a combination thereof
Implementation Method 2
moving the polishing pad and the chemical mechanical polishing composition relative to the substrate to abrade at least a portion of a surface of the substrate
Implementation Method 3
contacting the substrate with the polishing pad and the chemical-mechanical polishing composition, and moving the polishing pad
Data Source
AI summary
The invention provides a method of chemically mechanically polishing a substrate, especially a substrate comprising boron-doped polysilicon, comprising contacting the substrate with a chemical-mechanical polishing composition comprising an abrasive selected from α-alumina, silica, and a combination thereof, ferric ion, an organic acid, or a combination thereof, and water. The invention also provides a chemical-mechanical polishing composition comprising α-alumina, a nitrogen-containing compound selected from a zwitterionic homopolymer at, a monomeric ammonium salt, and a combination thereof, an organic acid, and water. The invention further provides a chemical-mechanical polishing composition comprising silica, an organic acid, ferric ion, and water.