Isotopically-Enriched Boron Compounds for Ion Implantation
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Solution Overview
Problem
Current boron implantation processes in semiconductor manufacturing face limitations due to low B+ beam current, resulting from the difficulty in ionizing boron trifluoride (BF3), which leads to reduced throughput and increased maintenance needs, especially at lower implantation energies where the blow-out effect is more pronounced.
Innovation Solution
The use of isotopically-enriched boron-containing compounds, such as B2F4, which are ionized to generate boron ions with higher efficiency, improving beam current and reducing maintenance requirements by forming isotopically enriched ionic species that enhance ion implantation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If boron trifluoride (BF3) is used as feed gas for ion implantation, then the process is widely established and compatible with existing equipment, but the ionization efficiency is very low (only about 15% fragmentation and 30% conversion to B+), resulting in low beam current and reduced throughput
Solution Approach 1:
The patent changes the chemical composition parameters of the feed gas from conventional BF3 to alternative boron-containing compounds such as B2F4, B2H6, and their isotopically enriched variants. These alternative compounds have different molecular structures and bonding characteristics that facilitate easier ionization and higher beam current generation, directly addressing the low ionization efficiency problem while maintaining compatibility with existing ion implantation equipment
Solution Approach 2:
The patent employs feed gases that are consumed in the ionization process to generate high beam current, accepting that the gas is depleted and requires periodic replacement. This approach prioritizes short-term high productivity (beam current) over long-term gas utilization efficiency, effectively trading gas consumption for improved ionization performance and throughput
2Productivity
If higher source gas flow and arc power are applied to increase beam current, then the ionization efficiency improves, but the decomposition of BF3 increases leading to boron residue deposition and clogging of the ion source
Solution Approach 1:
The patent converts the harmful decomposition behavior of boron-containing feed gases into a beneficial process by selecting compounds that decompose in a controlled manner to produce desirable boron species for implantation. The alternative feed gases (B2F4, B2H6) are designed to decompose into reactive intermediates that facilitate ionization without forming excessive problematic residues, thus transforming the decomposition issue from a harm into a useful ionization mechanism
Solution Approach 2:
The patent introduces intermediate chemical species through the decomposition of alternative feed gases that serve as mediators between the source gas and the final boron ions. These intermediates (such as BF2, B2F6) facilitate the ionization process more efficiently than direct BF3 ionization, reducing the need for excessive arc power and minimizing harmful residue formation while maintaining high beam current
3Ease of operation
If conventional BF3 feed gas is used, then the equipment operation is simple, but the low ionization efficiency requires increased arc power consumption to maintain adequate beam current
Solution Approach 1:
The patent changes the chemical parameters of the feed gas to alternative boron-containing compounds that require lower arc power for ionization. This parameter change maintains operational simplicity while significantly reducing energy consumption, as the alternative gases ionize more readily than BF3, allowing the same beam current to be achieved with lower arc power settings
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-enriched boron compounds significantly improves beam current levels, reducing the need for increased source gas flow and arc power, thereby increasing the efficiency and longevity of the ion source while minimizing decomposition and clogging issues.
Implementation Method 1
ionizing the compound to generate boron ions
Implementation Method 2
The ions of the beam penetrate the surface of the substrate to form a region of desired conductivity
Data Source
Figure 1
AI summary
An isotopically-enriched, boron-containing compound comprising two or more boron atoms and at least one fluorine atom, wherein at least one of the boron atoms contains a desired isotope of boron in a concentration or ratio greater than a natural abundance concentration or ratio thereof. The compound may have a chemical formula of B2F4. Synthesis methods for such compounds, and ion implantation methods using such compounds, are described, as well as storage and dispensing vessels in which the isotopically-enriched, boron-containing compound is advantageously contained for subsequent dispensing use.