Silicon-Phosphorus Composite Fabrication via Molten Mixing
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Solution Overview
Problem
Existing methods for combining silicon and phosphorus to form composite materials face challenges such as inhomogeneous powders due to segregation, high impurity levels, and difficulty in achieving high phosphorus concentrations, which are essential for semiconductor applications and cancer treatment.
Innovation Solution
A method involving heating silicon and phosphorus to specific temperature ranges to form a molten composite, with controlled phosphorus vaporization and contact with silicon, followed by atomization to produce a powder with uniform chemical composition and low impurity levels, utilizing silicon as a thermal insulator to manage temperature differences and minimize phosphorus loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phosphorus is introduced into silicon by ion implantation to achieve high concentrations, then phosphorus concentration increases, but manufacturing complexity and process steps increase
Solution Approach 1:
The invention changes the physical state parameters of both silicon and phosphorus to molten phase, enabling direct mixing and combination. By heating silicon to 1420°C and phosphorus to 417°C respectively, both materials become liquid, allowing phosphorus to be uniformly distributed in silicon without complex ion implantation processes, achieving high phosphorus concentration through simple mixing
Solution Approach 2:
The invention creates a composite material system where molten phosphorus is mixed with molten silicon to form a homogeneous alloy. This composite approach allows direct combination of elements in desired proportions, achieving high phosphorus concentration (up to 10^20 atoms/cm³) through material composition rather than complex doping processes
2Quantity of substance
If red phosphorus is brought into contact with molten silicon to combine, then phosphorus can be incorporated, but phosphorus vaporizes due to low boiling point, causing loss and containment difficulty
Solution Approach 1:
The invention changes phosphorus from solid state to molten state by heating to 417°C, increasing its volatility control and enabling it to be contained and mixed with molten silicon. The molten phase allows phosphorus to be handled as a liquid metal rather than a vaporizing solid, reducing uncontrolled loss
Solution Approach 2:
The invention employs an inert atmosphere (argon or nitrogen) during the mixing process to prevent phosphorus oxidation and reduce vaporization loss. The inert gas environment suppresses phosphorus vapor escape and prevents unwanted chemical reactions, allowing complete incorporation of phosphorus into silicon
3Ease of manufacture
If silicon and phosphorus are melted and cast to form alloys, then composite material can be produced, but non-silicon elements segregate during casting, causing inhomogeneous powders
Solution Approach 1:
The invention uses periodic stirring or agitation during the molten state to prevent segregation. By continuously or periodically mixing the molten silicon-phosphorus alloy before solidification, uniform distribution of phosphorus throughout the silicon matrix is maintained, preventing segregation and ensuring homogeneous composition in the final powder
Solution Approach 2:
The invention performs mixing and homogenization while both materials are in molten state before solidification occurs. This preliminary mixing action ensures uniform distribution of phosphorus atoms in silicon liquid, preventing subsequent segregation during cooling and casting, and guaranteeing composition homogeneity in the final product
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 produces a composite material with high phosphorus concentrations and low impurity levels, ensuring homogeneity and suitability for semiconductor applications and cancer treatment, particularly in brachytherapy using 32P radionuclides.
Implementation Method 1
diffusion of the impurity into the silicon from a source that is spatially separate from the silicon
Implementation Method 2
heating at least part of a sample of phosphorus in such a manner that phosphorus vapour is generated
Implementation Method 3
utilizing silicon as a thermal insulator to manage temperature differences and minimize phosphorus loss
Data Source
AI summary
The present invention concerns new methods of fabricating a silicon material comprising phosphorus. The methods allow high levels of phosphorus to be combined with the silicon. In one aspect of the invention a sample of phosphorus is surrounded with a sample of silicon. At least some of the phosphorus is then vaporised and caused to interact with the silicon.