Plasma Flood Gun Filament Control for Stable Ion Implantation
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Solution Overview
Problem
Ion implantation in semiconductor wafer processing leads to wafer charging due to the buildup of positive charges, resulting in non-uniform doping and arcing defects, which existing technologies fail to mitigate effectively.
Innovation Solution
A plasma flood gun is used to flood electrons into the ion beam during implantation, with a filament resistance measurement system that adjusts the filament current to maintain operating temperature and reduce contamination, thereby extending the filament's useful life and improving the predictability of the plasma flood gun's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a plasma flood gun is used to neutralize wafer charging, then the uniformity of doping is improved, but the filament contamination increases and operational life decreases
Solution Approach 1:
The system incorporates a filament resistance measurement system that continuously monitors filament resistance and provides feedback to the control system. When resistance exceeds a threshold indicating contamination, the system automatically adjusts operational parameters or triggers maintenance, creating a closed-loop control that resolves the contradiction between maintaining doping uniformity and extending filament life
Solution Approach 2:
The system performs preliminary measurements of filament resistance before contamination severely impacts performance. By detecting resistance changes early in the contamination process, the system can take preventive actions such as adjusting plasma parameters or scheduling maintenance before the filament fails, thus extending operational life while maintaining doping quality
2Reliability
If the filament current is increased to maintain plasma generation, then the plasma flood gun effectiveness is improved, but the filament temperature increases and contamination accelerates
Solution Approach 1:
The system dynamically adjusts filament current based on real-time resistance measurements rather than using a fixed high current. The control system modulates current levels to maintain sufficient plasma generation for wafer charging neutralization while preventing excessive temperature rise that would accelerate contamination, thus resolving the contradiction between effectiveness and contamination
Solution Approach 2:
The system changes operational parameters (filament current, plasma power) based on measured filament resistance. As resistance increases due to contamination, the system adjusts parameters to maintain plasma effectiveness without further increasing filament temperature and contamination rate, transforming a static high-current operation into a dynamic adaptive 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 solution effectively neutralizes wafer charging, reduces contamination, and extends the operational life of the filament, leading to more consistent and reliable ion implantation processes.
Implementation Method 1
a filament to emit electrons based on a filament current induced in the filament to heat the filament to a temperature
Implementation Method 2
the plasma interacts with the ion beam to neutralize at least some of a positive charge buildup on the semiconductor wafer
Data Source
AI summary
A plasma flood gun includes a filament to emit first electrons based on a first filament current induced in the filament to heat the filament to a first temperature at a first time. The first electrons interact with an inert gas in an arc plasma chamber to generate a first plasma. A filament resistance meter measures a first filament resistance of the filament, in-situ, during generation of the first plasma. A filament current source adjusts, based on the first filament resistance, the first filament current induced in the filament at the first time to a second filament current induced in the filament at a second time to generate a second plasma in the arc plasma chamber at the second time.