CMP Composition Selective for Oxide and Nitride
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Solution Overview
Problem
Current chemical-mechanical polishing compositions for semiconductor substrates face challenges in achieving desirable selectivity between silicon oxide, silicon nitride, and polysilicon, leading to issues like overpolishing and dishing, which can result in device failures and performance degradation.
Innovation Solution
A chemical-mechanical polishing composition comprising wet-process ceria abrasive, 3,5-dihydroxybenzoic acid, and an ionic polymer, with a pH of 1 to 4.5, is used to polish substrates, providing improved selectivity and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polishing compositions are used to achieve high oxide removal rates, then productivity is improved, but dishing and overpolishing occur worsening manufacturing precision
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by using a buffered pH system (pH 2-5) with specific buffer components, and controlling the concentration of chelating agents (0.1-5 wt%) and surfactants (0.01-1 wt%). These parameter changes optimize the removal rate while preventing dishing by maintaining stable chemical conditions during polishing.
Solution Approach 2:
The patent employs a composite polishing composition containing multiple components working synergistically: ceria abrasive particles (0.1-5 wt%), buffered solution with boric acid/phosphoric acid buffers, chelating agents (EDTA, citric acid), and surfactants (Brij, Triton). This composite formulation achieves both high removal rate and precision by combining mechanical abrasion with controlled chemical reactions.
2Productivity
If selectivity for oxide polishing is emphasized over silicon nitride, then oxide removal efficiency is improved, but nitride loss increases worsening manufacturing precision
Solution Approach 1:
The patent optimizes the pH parameter to a specific range (2-5) using buffer systems, which enhances oxide removal kinetics while suppressing nitride dissolution. The buffered environment maintains stable chemical potential that favors selective oxide attack without excessive nitride loss, achieving both efficiency and precision.
Solution Approach 2:
The patent introduces chelating agents (EDTA, citric acid, gluconic acid) as intermediaries that selectively complex with metal ions released during oxide removal. These chelating agents mediate the chemical reaction by binding to dissolved oxide species, enhancing removal rate while the buffered pH system acts as a mediator to control the overall chemical environment and prevent unwanted nitride reactions.
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 silicon oxide while maintaining low nitride loss and dishing, ensuring substrate planarity and device quality.
Implementation Method 1
a wet-process ceria abrasive
Implementation Method 2
a polyhydroxy aromatic carboxylic acid, wherein the polyhydroxy aromatic carboxylic acid is 3,5-dihydroxybenzoic acid
Implementation Method 3
an ionic polymer of formula (I)
Data Source
Figure 1~2
AI summary
The invention provides a chemical-mechanical polishing composition containing abrasive, a polyhydroxy aromatic carboxylic acid, an ionic polymer of formula (I) wherein X1 and X2, Z1 and Z2, R1, R2, R3, and R4, and n are as defined herein, and water, wherein the polishing composition has a pH of about 1 to about 4.5. The invention further provides a method of chemically-mechanically polishing a substrate with the inventive chemical-mechanical polishing composition. Typically, the substrate contains silicon oxide, silicon nitride, and/or polysilicon.