CMP Slurry Composition for High SiN:TEOS Selectivity
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Solution Overview
Problem
Existing chemical mechanical polishing (CMP) slurries face challenges in efficiently polishing surfaces with tungsten (W), tetraethyl orthosilicate (TEOS)/SiO2, and silicon nitride (SiN), particularly in maintaining robustness against TEOS removal and achieving high SiN:TEOS removal rate selectivity.
Innovation Solution
The use of a polishing slurry comprising an anionic modified colloidal silica abrasive, a SiN polishing rate enhancer, and an anionic surfactant, with a specific electrical conductivity range of 100 μS/cm to 350 μS/cm and a pH of about 4 to 5, enhances the polishing efficiency and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP slurries are used, then polishing can be performed, but SiN:TEOS removal rate selectivity is insufficient and TEOS dishing occurs
Solution Approach 1:
The patent changes the chemical parameters of the CMP slurry by using anionic modified colloidal silica abrasive with specific surface charge characteristics and controlling pH in the range of 2.0-4.0. These parameter changes create electrostatic repulsion between the abrasive particles and TEOS, reducing TEOS removal rate while maintaining SiN removal rate, thereby achieving high SiN:TEOS selectivity greater than 50:1 and preventing TEOS dishing
Solution Approach 2:
The patent employs a composite slurry system combining anionic modified colloidal silica abrasive, pH buffer, and surfactant. The anionic modification of the colloidal silica creates a composite material with tailored electrostatic properties that selectively interact with SiN while repelling TEOS, achieving the required removal rate differential
2Productivity
If high abrasive concentration is used, then polishing efficiency improves, but slurry stability and control become difficult
Solution Approach 1:
The patent optimizes the abrasive concentration parameter to within 0.5-5.0 wt% and controls pH within 2.0-4.0, creating a stable operating window where the anionic colloidal silica maintains colloidal stability through electrostatic repulsion while providing sufficient polishing efficiency. The pH buffer system maintains composition stability throughout the polishing process
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 solution achieves a high SiN:TEOS removal rate selectivity, with a ratio greater than 40:1, and provides increased robustness against TEOS removal, even in the presence of WO42−, thereby minimizing TEOS dishing and maintaining polishing efficiency.
Implementation Method 1
chemical mechanical polishing (CMP)
Implementation Method 2
anionic surfactant
Data Source
AI summary
The present technology generally relates to compositions and methods for polishing surfaces comprising a metal and a dielectric film material. Embodiments include methods for polishing a surface comprising W, TEOS/SiO2 and SiN, comprising applying a polishing slurry comprising an abrasive, a SiN polishing rate enhancer, and an anionic surfactant, and methods of buffering a metal oxide salt in a CMP slurry to obtain an increased robustness against TEOS removal comprising polishing a surface comprising a metal and TEOS by applying a polishing slurry comprising an anionic modified colloidal silica abrasive and an anionic surfactant.