Acidic CMP Slurry for Boron-Polysilicon Selective Removal
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Solution Overview
Problem
The challenge in the semiconductor industry is achieving high removal rates of boron-polysilicon layers while maintaining selectivity for silicon nitride and silicon oxide during chemical-mechanical planarization (CMP), as well as effectively polishing titanium nitride, which is crucial for advanced memory device fabrication.
Innovation Solution
A chemical-mechanical polishing composition comprising silica abrasive, an oxidizing agent, and water with a pH of about 2 or less is used, which includes colloidal silica particles with specific size and charge characteristics, and cerium ammonium nitrate as the oxidizing agent, to enhance the removal rates and selectivity of boron-polysilicon, silicon nitride, and titanium nitride layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polishing compositions are used to increase removal rate of boron-polysilicon, then removal rate improves, but selectivity for silicon nitride and silicon oxide deteriorates
Solution Approach 1:
The patent applies parameter changes by adjusting the pH of the polishing composition to be highly acidic (pH 0.5-2.0) and by optimizing the concentration ratios of oxidizing agents (cerium ammonium nitrate and ammonium persulfate) relative to fluoride ions. This specific parameter configuration enables differential chemical reactions that achieve high removal rates for boron-polysilicon while maintaining selectivity for silicon nitride and silicon oxide stopping layers.
Solution Approach 2:
The patent uses a composite polishing composition containing multiple active ingredients working synergistically: cerium ammonium nitrate (oxidizing agent), ammonium persulfate (oxidizing agent), hydrofluoric acid (fluoride source), and silica abrasive particles. This composite formulation creates a complex chemical environment that selectively attacks boron-polysilicon through combined oxidation and fluorination mechanisms while preserving other materials.
2Productivity
If polishing composition is optimized for high removal rate of boron-polysilicon, then productivity improves, but removal rate control for titanium nitride deteriorates
Solution Approach 1:
The patent achieves tunable removal rates for titanium nitride by adjusting the concentration of oxidizing agents and fluoride ions in the polishing composition. The ratio of oxidizing agent to fluoride ion concentration serves as a control parameter that can be optimized to achieve desired removal rates for titanium nitride while maintaining high removal rates for boron-polysilicon, providing adaptability for different device fabrication requirements.
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
This composition achieves high removal rates for boron-polysilicon and low removal rates for silicon nitride and titanium nitride, providing the necessary selectivity and polishing performance required for advanced memory device fabrication with improved substrate quality and reduced defects.
Implementation Method 1
The abrasive material may be incorporated into the polishing pad instead of, or in addition to, being suspended in the polishing composition
Implementation Method 2
contacting the surface with a polishing pad saturated with the polishing composition
Implementation Method 3
a chemical-mechanical polishing composition comprising: (a) a silica abrasive; (b) an oxidizing agent
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition comprising: (a) a silica abrasive; (b) an oxidizing agent; and (c) water, wherein the chemical-mechanical polishing composition has a pH of about 2 or less. The invention also provides a method of chemically-mechanically polishing a substrate, especially a substrate comprising a boron-doped polysilicon layer on a surface of the substrate, using said composition.