High Purity Tin Refining for Semiconductor Alpha Ray Reduction
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Solution Overview
Problem
Current methods for reducing alpha particle radiation in tin used in semiconductor manufacturing are inefficient, costly, and do not achieve the necessary low alpha ray counts required for modern semiconductor devices, often requiring complex processes and high-cost materials without achieving the desired purity levels.
Innovation Solution
A method involving leaching tin with acid, using the leachate as an electrolytic solution, suspending adsorbents like titanium oxide or activated carbon to refine the tin, and performing electrolytic refining to achieve high purity tin with reduced U, Th, Pb, and Bi content, followed by melting and casting to stabilize the alpha ray count at 0.001cph/cm² or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional electrolytic refining is used to reduce alpha ray count, then lead concentration is reduced, but the alpha ray count remains above 0.005cph/cm² which is insufficient for modern semiconductor devices
Solution Approach 1:
The refining process is divided into multiple sequential stages: initial electrolytic refining to remove lead, followed by a second electrolytic refining stage to achieve ultra-low alpha ray counts. This segmentation allows each stage to target specific impurities and achieve cumulative purification效果
Solution Approach 2:
High purity sulfuric acid and hydrochloric acid are used as intermediary substances to create optimized electrolytic solutions. These intermediaries enable more effective ion separation and deposition, achieving lower alpha ray counts than conventional methods
2Productivity
If highly refined sulfuric acid and hydrochloric acid are used to achieve low lead concentration, then electrolysis efficiency improves, but the alpha ray count of 0.005cph/cm² is still not low enough for semiconductor applications
Solution Approach 1:
The patent implements continuous electrolytic refining without interruption, maintaining steady current density and optimized electrolyte composition throughout the process. This continuous action ensures complete removal of radioactive impurities without compromising production efficiency
Solution Approach 2:
The electrolysis parameters are precisely controlled and optimized: current density is maintained within specific ranges, electrolyte temperature and composition are continuously monitored. These parameter changes maximize purification efficiency while maintaining productive output
3Ease of manufacture
If conventional refining methods are used, then the process is simple and cost-effective, but the alpha ray count remains at 0.03cph/cm² or higher which is unacceptable for semiconductor devices
Solution Approach 1:
The manufacturing process is segmented into distinct refining stages, each with specific objectives and controlled parameters. This segmentation makes the complex ultra-purification process manageable and repeatable, balancing complexity with effectiveness
Solution Approach 2:
Specific parameter ranges are established for each refining stage (current density, temperature, electrolyte composition) to optimize the balance between process simplicity and purification effectiveness, achieving low alpha ray counts without excessive complexity
4Object-affected harmful factors
If tin is stored for 3 years after refining to reduce alpha dose, then the alpha ray count decreases, but the tin cannot be used commercially until 3 years have lapsed which is industrially inefficient
Solution Approach 1:
All purification actions are performed preliminarily during the manufacturing process itself. The multi-stage electrolytic refining removes radioactive impurities before the tin leaves the factory, eliminating the need for prolonged storage and enabling immediate commercial use
Solution Approach 2:
The patent converts the potential harm of radioactive impurities into a benefit by using controlled electrolytic processes that selectively remove these impurities. The harmful radioactive elements are transformed into removable ions that can be efficiently separated and eliminated
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 effectively reduces alpha ray counts to 0.001cph/cm² or less, ensuring high purity tin suitable for semiconductor devices by eliminating radioactive elements and reducing radiation interference, thereby minimizing soft errors in semiconductor devices.
Implementation Method 1
leaching tin with acid (sulfuric acid, for instance), using the obtained leachate as an electrolytic solution
Implementation Method 2
suspending an adsorbent of impurities in the electrolytic solution
Implementation Method 3
performing electrolytic refining using a raw material Sn anode so as to obtain high purity tin
Data Source
AI summary
Provided is high purity tin or tin alloy wherein the respective contents of U and Th are 5ppb or less, the respective contents of Pb and Bi are 1 ppm or less, and the purity is 5N or higher (provided that this excludes the gas components of O, C, N, H, S and P). This high purity tin or tin alloy is characterized in that the α ray count of high purity tin having a cast structure is 0.001 cph/cm2 or less. Since recent semiconductor devices are densified and are of large capacity, there is considerable risk of a soft error occurring due to the influence of the α ray from materials in the vicinity of the semiconductor chip. In particular, there are strong demands for purifying the soldering material or tin to be used in the vicinity of semiconductor devices, as well as for materials with fewer α rays. Thus, the present invention aims to provide high purity tin or tin alloy and the manufacturing method of such high purity tin by reducing the α dose of tin so as to be adaptable as the foregoing material.