Ruthenium Copper CMP Slurry Selectivity
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Solution Overview
Problem
Conventional chemical mechanical polishing compositions for semiconductor substrates with ruthenium and copper layers face challenges such as non-uniform removal rates and the formation of toxic ruthenium tetraoxide, along with galvanic attack issues due to differing reduction potentials, leading to undesirable non-uniformities and safety concerns.
Innovation Solution
A chemical mechanical polishing slurry composition comprising water, 0.1 to 25 wt% abrasive, 0.05 to 1 wt% sodium hypochlorite or potassium hypochlorite, 0.001 to 1 wt% copolymer of acrylic acid and methacrylic acid, 0.005 to 1 wt% copper corrosion inhibitor, and 0.0005 to 0.01 wt% poly(methylvinyl ether), with a pH of 8 to 12, is used in conjunction with a polishing pad and machine to achieve selective removal of ruthenium and copper while avoiding toxic byproducts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polishing compositions with strong oxidizing agents are used for ruthenium polishing, then ruthenium removal rate is improved, but toxic ruthenium tetraoxide gas is formed
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by using mild oxidizing agents (hypochlorite with E° = 0.89 V) instead of strong oxidizing agents, and controlling pH to be greater than 7, thereby eliminating toxic ruthenium tetraoxide formation while maintaining effective ruthenium removal
Solution Approach 2:
The patent converts the harmful strong oxidizing environment into a beneficial mild oxidizing environment that selectively removes ruthenium without forming toxic gases, while the mild conditions simultaneously protect copper from unwanted oxidation
2Productivity
If conventional polishing compositions with strong oxidizing agents are used, then ruthenium polishing is effective, but copper oxidizes quickly leading to non-uniform removal rates
Solution Approach 1:
The patent changes the oxidation potential parameter by selecting hypochlorite (E° = 0.89 V) as the oxidizing agent, which provides sufficient oxidation for ruthenium removal while being mild enough to prevent rapid copper oxidation, thereby achieving uniform removal rates across different materials
Solution Approach 2:
The polishing composition is designed to have different reactivity toward different materials (ruthenium vs. copper) by controlling the oxidizing strength and pH, creating selective chemical action that removes ruthenium effectively while preserving copper uniformity
3Adaptability or versatility
If polishing compositions are designed for different device configurations, then polishing performance varies, but formulation complexity increases
Solution Approach 1:
The patent creates a universal polishing composition formulation based on hypochlorite oxidizing agent and pH control that effectively polishes both ruthenium and copper-containing devices, eliminating the need for multiple specialized formulations for different device configurations
Solution Approach 2:
By establishing universal parameter ranges (pH > 7, hypochlorite concentration, presence of corrosion inhibitors), the patent enables a single formulation to adapt to various device configurations without requiring complex formulation changes
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 provides robust polishing performance across various device configurations with improved ruthenium to copper selectivity and reduced toxicity, ensuring uniformity and safety in semiconductor substrate processing.
Implementation Method 1
chemical mechanical polishing
Implementation Method 2
chemical mechanical polishing composition comprising... 0.05 to 1 wt% sodium hypochlorite or potassium hypochlorite
Implementation Method 3
copper may be subject to galvanic attack by ruthenium when polishing certain device configurations using conventional ruthenium polishing compositions
Data Source
AI summary
A method for chemical mechanical polishing of a substrate comprising ruthenium and copper is provided wherein the substrate is contacted with a polishing slurry containing an abrasive, hypochlorite, a copolymer of acrylic acid and methacrylic acid, benzotriazole, poly(methyl vinyl ether) and a non-ionic surfactant at a pH of 9 to 11.