Silicon Dopant Gas Mixture for Ion Source Erosion Control
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Solution Overview
Problem
The existing silicon ion implantation processes using silicon tetrafluoride (SiF4) face limitations in generating high beam current due to the potential for ion source component damage and reduced life, as higher energy inputs required for increased ionization can lead to chemical erosion and deposition of W-containing deposits, compromising the ion source's ability to sustain plasma and generate Si+ ions.
Innovation Solution
A silicon-based dopant gas composition comprising a first silicon-based species, such as SiF4, combined with a second species having a higher ionization cross-section, like Si2H6, which allows for increased beam current without degrading the ion source, by maintaining or reducing the operating arc voltage and minimizing component degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the operating arc voltage is increased to generate more Si+ ions from SiF4, then the beam current is improved, but the ion source components suffer from chemical erosion and deposition of W-containing deposits, reducing ion source life
Solution Approach 1:
The patent changes the chemical composition parameter of the dopant gas from pure SiF4 to a mixture containing SiF4 and Si2H6. This parameter change allows the system to achieve high beam current through the higher ionization cross-section of Si2H6 without requiring increased arc voltage, thereby avoiding the chemical erosion and tungsten deposit formation that would otherwise reduce ion source life.
Solution Approach 2:
The patent uses a composite dopant gas composition combining SiF4 and Si2H6 in specific proportions. This composite approach leverages the complementary properties of both gases: SiF4 provides stable plasma generation while Si2H6 contributes higher ionization efficiency, achieving both high beam current and extended ion source life simultaneously.
2Quantity of substance
If the energy input to the ion source is increased to ionize more SiF4, then more Si+ ions are generated for higher beam current, but the tungsten chamber walls are more rapidly etched and eroded by active fluorine
Solution Approach 1:
The patent modifies the dopant gas composition parameter to include Si2H6 alongside SiF4. This change enables the system to generate sufficient Si+ ions through the superior ionization characteristics of Si2H6 without increasing energy input, thereby reducing the production of active fluorine that would otherwise erode the tungsten chamber walls.
3Use of energy by moving object
If the arc chamber temperature increases during ion implantation, then more SiF4 can be ionized, but active fluorine more rapidly etches and erodes the tungsten chamber walls, causing cathode deposition of W-containing deposits
Solution Approach 1:
The patent changes the dopant gas composition to include Si2H6, which has a higher ionization cross-section than SiF4. This parameter change allows the system to maintain high ionization efficiency at lower arc chamber temperatures, thereby reducing the rate of tungsten wall erosion and the subsequent deposition of W-containing deposits on the cathode.
Solution Approach 2:
The patent converts the potentially harmful high-temperature operation into a beneficial low-temperature process by utilizing Si2H6's higher ionization efficiency. The energy that would otherwise heat the chamber and accelerate tungsten erosion is instead used more efficiently for ionization, transforming a harmful thermal effect into a beneficial ionization process.
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 composition enhances beam current and extends ion source life by reducing fluorine-induced erosion and deposition, maintaining stability and throughput while avoiding premature filament failure, thus improving the overall efficiency and productivity of silicon ion implantation.
Implementation Method 1
An ion-source filament is used to ionize the dopant gas source into the various dopant ionic species. The ions produce a plasma environment within the ion chamber.
Implementation Method 2
The ions produce a plasma environment within the ion chamber.
Implementation Method 3
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.
Implementation Method 4
The desired dopant ionic species of the beam penetrate the surface of the semiconductor wafer to form a doped region of a certain depth with desired electrical and/or physical properties.
Implementation Method 5
as the walls of the arc chamber increase in temperature during a typical ion implant process, active fluorine that is released from SiF4 can more rapidly etch and erode the tungsten chamber walls
Data Source
AI summary
A novel composition, 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.