Palladium Coating Thickness Measurement via Electrochemical Reduction
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Solution Overview
Problem
Current methods for measuring the thickness of palladium layers in microelectronic assembly processes, such as XRF, are inadequate for thin coatings due to poor energy resolution and require complex and expensive instrumentation, and are not suitable for odd geometries and small specimen areas typical of microelectronic devices.
Innovation Solution
A method and apparatus using electrochemical reduction to determine the thickness of palladium coatings by forming a palladium hydride with specific stoichiometry, allowing for absolute measurement of coating thickness through electrochemical charge analysis, which can be applied to any substrate and provides accurate results without the need for complex instrumentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If XRF method is used to measure palladium thickness, then measurement capability is provided, but the instrumentation becomes complicated and expensive
Solution Approach 1:
The patent replaces the complex XRF instrumentation system with a simple electrochemical measurement system. Instead of using x-ray fluorescence detection, the invention uses electrochemical reduction of protons to form palladium hydride, measuring only the electrical charge required for this transformation. This substitution of measurement mechanism dramatically simplifies the instrumentation while maintaining measurement capability.
Solution Approach 2:
The invention employs a simple, inexpensive electrochemical cell with basic electrodes and electrolyte solution rather than expensive, complex XRF instrumentation. The measurement system uses readily available materials and simple electrical measurement equipment, making the measurement process accessible and cost-effective.
2Measurement precision
If XRF method is used to measure palladium thickness, then measurement capability is provided, but the instrumentation becomes expensive
Solution Approach 1:
The invention employs a simple, inexpensive electrochemical cell with basic electrodes and electrolyte solution rather than expensive, complex XRF instrumentation. The measurement system uses readily available materials and simple electrical measurement equipment, making the measurement process accessible and cost-effective.
Solution Approach 2:
The patent replaces the complex XRF instrumentation system with a simple electrochemical measurement system. Instead of using x-ray fluorescence detection, the invention uses electrochemical reduction of protons to form palladium hydride, measuring only the electrical charge required for this transformation. This substitution of measurement mechanism dramatically simplifies the instrumentation while maintaining measurement capability.
3Measurement precision
If XRF method is used to measure palladium thickness, then measurement capability is provided, but it is difficult to apply to odd geometries and small specimen areas
Solution Approach 1:
The electrochemical measurement system is highly adaptable to various specimen geometries and sizes. The working electrode can be configured to contact the palladium coating on flat surfaces, curved surfaces, small areas, or irregular geometries. The electrolyte solution can be applied locally or immersively, making the method universally applicable to diverse microelectronic components regardless of their shape or size.
Solution Approach 2:
The measurement method allows for localized measurement of palladium coating thickness on specific areas of the specimen. The working electrode can be positioned to contact only the region of interest, and the electrolyte can be applied locally. This enables measurement on small specimen areas and irregular geometries where uniform coverage is not required.
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 an accurate, absolute measurement of palladium coating thickness, suitable for various substrates and geometries, with improved precision and reduced costs compared to existing techniques, enabling effective control of palladium layer thickness in microelectronic assembly processes.
Implementation Method 1
determining the electrical charge required to form a palladium hydride having a specific stoichiometry, preferably PdH0.58 (beta-phase), throughout the coating thickness by electrochemical reduction of protons from an electrolytic solution
Implementation Method 2
the coating thickness is determined from the anodic charge density required to anodically remove the palladium hydride by electrochemical oxidation
Data Source
AI summary
The thickness of a palladium coating on copper (or another substrate) is measured by passing a cathodic current through a predetermined area of the coating in contact with an electrolytic solution and measuring the potential as a function of time. Protons from the electrolytic solution are electrochemically reduced to palladium hydride at cathodic potentials less negative than required for evolution of hydrogen. As formation of the PdH0.58 beta-phase throughout the Pd coating is completed, the cathodic potential increases rapidly to a cathodic potential plateau corresponding to evolution of hydrogen gas on the PdH0.58 surface. This step in the cathodic potential provides an endpoint time for the measurement. The absolute thickness of the Pd coating is calculated from the integrated cathodic charge passed up to the endpoint time and the predetermined area of the coating in contact with the electrolytic solution.