Isotopically Purified 12C Implantation Mask for Neutron Emission Control
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Solution Overview
Problem
High energy ion implantation processes using carbon-based mask materials result in significant neutron emission due to the presence of 13C isotopes, requiring thick neutron-absorbing shields and prolonged 'cooling off' periods for substrate handling.
Innovation Solution
Employing isotopically purified 12C carbon-containing materials for implantation masks, which significantly reduce neutron emission by minimizing the 13C concentration, thereby suppressing neutron yield during high energy ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If carbon-based mask materials (containing 13C isotope) are used for implantation masking, then the mask provides effective pattern definition and ion blocking, but significant neutron emission occurs during high energy ion implantation
Solution Approach 1:
The patent changes the isotopic composition parameter of the carbon material from natural abundance (1.1% 13C) to isotopically purified (≥99% 12C). This parameter change eliminates the nuclear reaction pathway that produces neutrons when 13C is struck by high energy ions, thereby resolving the contradiction between effective masking and neutron emission.
Solution Approach 2:
The patent employs a composite material approach by combining isotopically purified 12C carbon-containing material with traditional photoresist or hard mask materials. This creates a mask material that maintains the desired chemical and physical properties for effective pattern definition while eliminating the harmful neutron emission through isotopic purification.
2Object-affected harmful factors
If thick neutron-absorbing shields are installed in the implantation chamber to absorb emitted neutrons, then neutron radiation is reduced, but the device complexity and chamber space requirements increase
Solution Approach 1:
The patent extracts the neutron emission problem from the system by removing the 13C isotope from the mask material through isotopic purification. By taking out the problematic 13C component and replacing it with 12C, the source of neutron radiation is eliminated, making thick neutron-absorbing shields unnecessary and thereby reducing device complexity.
Solution Approach 2:
The patent converts the harmful neutron emission into a beneficial outcome by using isotopically purified 12C material that does not produce neutrons. This transformation eliminates the need for complex shielding structures while maintaining effective mask functionality, turning a harmful radiation problem into a safe operating condition.
3Ease of manufacture
If conventional carbon-based masks are used, then standard mask fabrication processes can be employed, but prolonged cooling off periods are required before substrate handling due to persistent neutron radiation
Solution Approach 1:
The patent changes the temporal parameter of the process by using isotopically purified 12C mask material that does not generate persistent neutron radiation. This parameter change eliminates the need for prolonged cooling off periods, allowing immediate substrate handling after implantation while maintaining compatibility with standard mask fabrication processes.
4Manufacturing precision
If high energy ions (above 2-3 MeV) are used for implantation, then deeper ion penetration and better doping profiles are achieved, but neutron emission from 13C in mask materials increases significantly
Solution Approach 1:
The patent changes the isotopic composition parameter of the mask material to isotopically purified 12C, which eliminates the energy-dependent neutron emission that occurs with 13C at high ion energies. This allows the use of high energy ions (above 2-3 MeV) for deeper penetration and better doping profiles without the penalty of increased neutron yield.
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 use of isotopically purified 12C materials in implantation masks reduces neutron emission, allowing for safer and more efficient high energy ion implantation processes without the need for extensive shielding and reduced substrate handling delays.
Implementation Method 1
The 13C isotope, when struck with sufficiently energetic ions, may be transformed by nuclear reaction, leading to radioactive decay via a neutron emission mechanism
Data Source
AI summary
A substrate assembly may include a substrate base; and a low emission implantation mask, disposed on the substrate base. The low emission implantation mask may include a carbon-containing material, the carbon-containing material comprising an isotopically purified carbon, formed from a 12C carbon isotope precursor.