Ion Source Power and Flow Control for Enriched Dopant Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of enriched dopant gases in ion implantation processes leads to increased ion beam current, which destabilizes the ion source and shortens the ion source life due to tungsten deposits and the halogen cycle, requiring re-qualification of the ion implantation process and resulting in productivity loss.
Innovation Solution
Introducing enriched dopant gases at a flow rate sufficient to maintain stability and operating at a reduced total power level, specifically reducing the filament power and cathode temperature to control ionization efficiency and minimize tungsten deposits, while maintaining the same beam current as with non-enriched dopant gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If enriched dopant gas is used at the same flow rate as non-enriched dopant gas, then beam current increases and implant dosage efficiency improves, but ion source stability deteriorates and tungsten deposits increase
Solution Approach 1:
The patent changes the flow rate parameter of the enriched dopant gas from the conventional same-rate usage to a reduced flow rate (1-5 sccm range). This parameter change reduces the amount of fluorine introduced into the ion source chamber, thereby reducing tungsten deposits and halogen cycle activity while maintaining productivity benefits through the enriched isotope concentration
Solution Approach 2:
The patent modifies the operating conditions by reducing total power level and filament power when using highly enriched dopant gas. This parameter adjustment controls ionization efficiency to prevent excessive beam current that would destabilize the ion source, while still achieving required implant dosage through the enriched gas composition
2Productivity
If enriched dopant gas is used at the same flow rate as non-enriched dopant gas, then implant dosage efficiency improves, but ion source life decreases due to tungsten deposits
Solution Approach 1:
The patent reduces the flow rate parameter of enriched dopant gas to 1-5 sccm range, which introduces less fluorine into the ion source chamber. This reduces the rate of tungsten deposit formation and halogen cycle activity, thereby extending ion source life while maintaining implant dosage efficiency through the highly enriched isotope concentration (≥55% enrichment)
3Reliability
If total power level is reduced when using enriched dopant gas, then ion source stability improves and tungsten deposits decrease, but beam current may be affected
Solution Approach 1:
The patent reduces total power level and filament power parameters when using highly enriched dopant gas. This reduces ionization efficiency to compensate for the higher concentration of dopant atoms, thereby maintaining beam current within acceptable ranges while improving ion source stability and reducing tungsten deposits. The enriched gas composition allows this power reduction without sacrificing productivity
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 approach extends the ion source life, reduces tungsten deposits, and maintains the qualified beam current, thereby increasing productivity and yield without the need for re-qualification of the ion implantation process.
Implementation Method 1
Ionization of the dopant gas generates the ion species which can be subsequently implanted into a given workpiece
Implementation Method 2
isotopically enriched dopant gases can be utilized which will allow less overall gas to be introduced into the ion source chamber
Implementation Method 3
enriched dopant gas is a fluorine-containing gas, which is well known to etch walls of a tungsten ion chamber and form tungsten fluoride (WFx) species that can migrate to the hot source filament where tungsten can be deposited
Implementation Method 4
The ion implantation process is used in integrated circuit fabrication to introduce dopant impurities into semiconductor wafers
Data Source
AI summary
A novel process for using enriched and highly enriched dopant gases is provided herein that eliminates the problems currently encountered by end-users from being able to realize the process benefits associated with ion implanting such dopant gases. For a given flow rate within a prescribed range, operating at a reduced total power level of the ion source is designed to reduce the ionization efficiency of the enriched dopant gas compared to that of its corresponding non-enriched or lesser enriched dopant gas. The temperature of the source filament is also reduced, thereby mitigating the adverse effects of fluorine etching and ion source shorting when a fluorine-containing enriched dopant gas is utilized. The reduced levels of total power in combination with a lower ionization efficiency and lower ion source temperature can interact synergistically to improve and extend ion source life, while beneficially maintaining a beam current that does not unacceptably deviate from previously qualified levels.