Silicon Dopant Gas Composition for Ion Beam Current
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Solution Overview
Problem
The existing silicon ion implantation processes using silicon tetrafluoride (SiF4) face limitations in achieving higher beam current without compromising ion source life, as increased energy input can damage ion source components and reduce their lifespan.
Innovation Solution
A unique silicon-based dopant gas composition combining SiF4 with a second species, such as disilane (Si2H6), which has a higher ionization cross-section, allows for increased beam current without degrading the ion source, by operating at lower arc voltages and reducing component degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the energy input to the ion source is increased to generate more Si+ ions, then the beam current is improved, but the ion source components are damaged and lifespan is reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the dopant gas from pure SiF4 to a mixture containing Si2H6 and SiF4. This parameter change allows the system to achieve the same or higher beam current at lower arc voltages, thereby reducing the damaging energy input to ion source components while maintaining productivity
Solution Approach 2:
The patent uses a composite dopant gas composition combining Si2H6 and SiF4. The Si2H6 component has higher ionization cross-section and produces fewer reactive fluorine ions, while SiF4 provides stable silicon ion source. This composite approach balances beam current generation with ion source protection, resolving the contradiction between productivity and reliability
2Productivity
If the arc voltage is increased to ionize more SiF4, then the beam current is improved, but the tungsten chamber walls are etched and eroded more rapidly
Solution Approach 1:
The patent changes the dopant gas composition to include Si2H6, which alters the plasma chemistry in the ion source. This parameter change reduces the concentration of active fluorine ions that cause chemical erosion, allowing higher beam current operation without excessive chamber wall damage
Solution Approach 2:
The patent converts the potentially harmful high-energy plasma environment into a beneficial process by using Si2H6, which modifies the plasma composition to reduce erosive fluorine ions while maintaining or enhancing silicon ion production. The higher ionization cross-section of Si2H6 turns what would be excessive energy input into an efficient ionization process
3Productivity
If the beam current is increased to improve throughput, then the productivity is improved, but the ion source components are more susceptible to deposition and performance degradation
Solution Approach 1:
The patent changes the dopant gas composition to Si2H6-SiF4 mixture, which modifies the plasma chemistry to reduce deposition of tungsten-containing deposits on the cathode. This parameter change allows sustained high beam current operation without the performance degradation that would limit throughput
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 composition enhances beam current and extends ion source life by maintaining stability and reducing beam glitching, thereby improving throughput and productivity in silicon ion implantation processes.
Implementation Method 1
An ion-source filament is used to ionize the dopant gas source into the various dopant ionic species
Implementation Method 2
The desired dopant ionic species of the beam penetrate the surface of the semiconductor wafer to form a doped region
Data Source
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AI summary
A dopant gas composition, a system and method thereof for improving beam current during silicon ion implantation are provided. The silicon ion implant process involves utilizing a first silicon-based co-species and a second species. The second species is selected to have an ionization cross-section higher than that of the first silicon-based species at an operating arc voltage of an ion source utilized during generation and implantation of active silicon ions species. The active silicon ions produce an improved beam current characterized by maintaining or increasing the beam current level without incurring degradation of the ion source when compared to a beam current generated solely from SiF4.