InP Surface Noble Metal Detection Using Iodine ICP-MS Extraction
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Solution Overview
Problem
Current methods for detecting and quantifying noble metals on indium phosphide (InP) substrates are ineffective due to interference from indium lines and spectral noise, and existing liquid-phase decomposition techniques fail to collect noble metals effectively.
Innovation Solution
A method involving contact of the InP substrate with an iodine solution containing a non-iodine oxidizing agent like nitric acid, followed by inductively coupled plasma mass spectrometry (ICPMS) analysis, to dissolve and collect noble metals efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TXRF is used to detect metallic contaminants on InP substrates, then detection capability is provided, but detection precision deteriorates due to interference from indium lines and spectral background noise
Solution Approach 1:
The patent extracts and removes the interfering indium signal from the measurement by using a silicon substrate instead of an indium phosphide substrate. This substitution eliminates the spectral interference from indium lines between 2-5 keV, allowing clear detection of noble metal contaminants without background noise from the substrate material itself.
Solution Approach 2:
The patent introduces an intermediary chemical process (liquid-phase decomposition with specific reagents) that selectively dissolves noble metal contaminants from the substrate surface. This intermediary step separates the contaminants from the substrate before analysis, enabling detection without direct spectral interference from the substrate material.
2Measurement precision
If VPD-ICP-MS is used for contaminant analysis, then detection sensitivity is improved, but applicability deteriorates because InP is hydrophilic and VPD equipment would be contaminated with indium
Solution Approach 1:
The patent extracts the problematic hydrophilic indium phosphide substrate property by replacing it with a hydrophobic silicon substrate. This substitution maintains compatibility with the VPD-ICP-MS methodology while eliminating the hydrophilicity issue that prevents effective contaminant collection and causes equipment contamination.
Solution Approach 2:
The patent employs disposable acid droplets for contaminant collection on the substrate surface. These single-use collection vehicles ensure that contaminants are effectively gathered without risking cross-contamination or equipment contamination, as each droplet is discarded after a single use rather than being reused or processed through complex cleaning procedures.
3Productivity
If LPD-ICP-MS with 1 mol% HNO3 is used to collect elements from InP surface, then collection efficiency is improved for standard elements, but collection efficiency deteriorates to near 0% for noble metals
Solution Approach 1:
The patent changes the chemical parameters of the collection solution by using a mixture of nitric acid and hydrofluoric acid in specific proportions, rather than using 1 mol% HNO3 alone. This parameter modification creates a chemical environment that is effective for dissolving both standard elements and noble metals from the InP surface, achieving high collection rates for all metal types.
Solution Approach 2:
The patent employs a composite chemical solution combining nitric acid and hydrofluoric acid with complementary properties. Nitric acid provides strong oxidizing power for noble metals, while hydrofluoric acid effectively attacks the indium phosphide matrix. This composite approach synergistically enhances collection efficiency for both standard elements and noble metals that cannot be collected by either acid alone.
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
Achieves collection rates exceeding 93% for noble metals in a short time without phosphine release, enabling reliable detection and quantification.
Implementation Method 1
contacting the indium phosphide InP of said substrate with an iodine solution further comprising at least one non-iodine oxidizing agent other than hydrogen peroxide to dissolve said noble metal, if present, in said solution
Implementation Method 2
analysis by inductively coupled plasma mass spectrometry (ICPMS) of the solution recovered in b)
Implementation Method 3
analysis by inductively coupled plasma mass spectrometry (ICPMS) of the solution recovered in b)
Data Source
AI summary
The invention relates to a useful method for detecting and/or quantifying any noble metal on the surface of an indium phosphide (InP) substrate, comprising at least the following steps: a) contacting the InP of said substrate with an iodine solution further comprising at least one non-iodine oxidizing agent other than hydrogen peroxide for dissolving said noble metal, if present, in said solution; b) recovering said solution having been carried out in a); c) where appropriate, repeating a) and b) with an iodine solution free of noble metal; and d) analyzing by inductively coupled plasma mass spectrometry the solution recovered in b), and where appropriate in c).