Tin-Silver Electrodeposition Solution Monitoring via Dual-Step Titration
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Solution Overview
Problem
Current methods for monitoring silver ion and complexing agent concentrations in tin-silver electrodeposition solutions are either unsafe, complex, or expensive, posing challenges for maintaining uniform manufacturing quality in semiconductor devices.
Innovation Solution
A dual-step titration method involving a precipitating agent and a metallic salt is used to precipitate silver ions and complexing agents, allowing for accurate measurement of their concentrations through endpoint determination, facilitated by a controlled apparatus with sensors for potential, conductivity, or electrochemical responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If atomic absorbance spectroscopy (AAS) is used to measure silver ion concentration, then measurement capability is provided, but the method requires use of an open flame which is not suitable for use inside a semiconductor fabrication facility
Solution Approach 1:
The patent replaces the mechanical/thermal system of AAS (open flame atomization) with an electrochemical system (voltammetric measurement). The silver ion concentration is measured through electrochemical reactions at an electrode surface rather than thermal atomization, eliminating the need for open flames while maintaining measurement capability
Solution Approach 2:
The patent introduces an intermediary substance (complexing agent or precipitating agent) that mediates the measurement process. These agents form complexes or precipitates with silver ions that can be measured electrochemically, serving as a safe intermediary between the silver ions and the measurement system
2Extent of automation
If inductively coupled plasma spectroscopy (ICP) is used to measure silver ion concentration, then automated measurement is achieved, but expensive and bulky analyzer equipment coupled with a pre-dilution system is required
Solution Approach 1:
The patent employs simple, inexpensive consumable items such as test strips or single-use electrodes that can be discarded after one measurement. This eliminates the need for expensive, complex, and bulky ICP analyzers while maintaining automated measurement capability through simple operational procedures
Solution Approach 2:
The patent extracts the essential measurement function from the complex ICP system and implements it through a simplified electrochemical approach. By taking out only the necessary measurement capability and removing unnecessary complexity, the system achieves automation without requiring expensive equipment
3Measurement precision
If high performance liquid chromatography (HPLC) is used to measure complexing agent concentration, then measurement capability is provided, but the method is expensive and complicated and requires use of flammable and hazardous solvents such as methanol or acetonitrile
Solution Approach 1:
The patent replaces the complex mechanical HPLC system with a simpler electrochemical measurement system. The complexing agent concentration is determined through electrochemical reactions that do not require flammable solvents, eliminating safety hazards while maintaining measurement capability
Solution Approach 2:
The patent uses simple, inexpensive test strips or electrodes for measuring complexing agent concentration, replacing the expensive and complicated HPLC system. These disposable items eliminate the need for hazardous solvents while providing sufficient measurement accuracy
4Measurement precision
If free complexer titration is used to measure complexing agent concentration, then measurement capability is provided, but the method requires two separate analysis steps which compounds the likelihood of error, increases overall analysis time, and consumes large amounts of chemicals
Solution Approach 1:
The patent merges the measurement of free complexer and bound complexer into a single simultaneous measurement step. By using an electrochemical method that detects total complexing agent concentration directly, the patent eliminates the need for separate analysis steps, reducing time and chemical consumption while maintaining measurement accuracy
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 method provides a safe, simple, and cost-effective means to accurately monitor silver ion and complexing agent concentrations, enhancing process control and maintaining consistent electrodeposition quality.
Implementation Method 1
adding a precipitating agent (X−) having a predetermined concentration to the electrodeposition solution to cause a reaction between at least a portion of the precipitating agent (X−) and substantially all of the silver ions (Ag+) such that the substantially all of silver ions (Ag+) are precipitated out from the electrodeposition solution as a precipitant (AgX)
Implementation Method 2
adding a metallic salt (Me+) of predetermined concentration to the electrodeposition solution to cause a reaction between at least a portion of the metallic salt (Me+) and substantially all of the precipitating agent (X−) remaining in the electrodeposition solution that did not react with the silver ions (Ag+); measuring the first endpoint of the silver ion (Ag+) back titration
Implementation Method 3
further adding metallic salt (Me+) of predetermined concentration to the electrodeposition solution to cause a reaction between at least a portion of the metallic salt (Me+) and substantially all of the complexing agent in the electrodeposition solution; and measuring the second endpoint of the complexing agent titration
Data Source
AI summary
The present disclosure relates to methods of monitoring the concentrations of silver ion and complexing agent in tin-silver (SnAg) electrodeposition solutions, and analysis and process control using such methods. Methods can include adding a precipitating agent to an electrodeposition solution including at least tin ions, silver ions, and complexing agent to cause a reaction between at least a portion of the precipitating agent and substantially all of the silver ions (to precipitate silver ions as a precipitant); adding a metallic salt to the electrodeposition solution to cause a reaction with substantially all of the remaining precipitating agent; measuring the endpoint of the silver ion back titration; further adding metallic salt to cause a further reaction with the complexing agent; and measuring the endpoint of the complexing agent titration.