Ion Implantation Extraction Electrode Voltage Modulation
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Solution Overview
Problem
Ion implantation systems face contamination issues due to deposits on electrodes and insulators, leading to decomposition and release of particles that contaminate the ion beam and workpieces during the semiconductor fabrication process.
Innovation Solution
The system modulates the voltage between the extraction and suppression electrodes to induce a controlled arc discharge, removing deposits from the electrode surfaces and mitigating contamination along the ion beamline and on wafers by selectively modulating the suppression voltage during workpiece transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the suppression electrode is biased to a negative potential to prevent electrons from being drawn into the ion source, then electron suppression is improved, but deposits accumulate on the electrode surfaces causing contamination
Solution Approach 1:
The suppression electrode voltage is modulated periodically between a suppression voltage (negative potential) and a discharge voltage (ground or positive potential). During implantation, the suppression voltage prevents electron draw-in. During non-implant periods, the discharge voltage creates arc discharges that remove deposits. This periodic switching resolves the contradiction by alternating between the two opposing requirements.
Solution Approach 2:
The voltage parameter of the suppression electrode is dynamically changed between two states: a negative suppression voltage during ion implantation to prevent electron draw-in, and a ground or positive discharge voltage during non-implant periods to enable arc discharge and deposit removal. This parameter change allows the same electrode to fulfill both conflicting functions at different times.
2Stability of the object's composition
If the extraction electrodes are kept stationary to maintain stable ion beam extraction, then extraction stability is improved, but deposits accumulate on the electrode surfaces
Solution Approach 1:
While maintaining physical stationarity of the extraction electrodes for stable ion beam extraction, the system applies periodic voltage modulation during non-implant periods to create controlled arc discharges. This removes deposits without requiring mechanical movement, thus preserving extraction stability while eliminating deposit accumulation.
3Object-generated harmful factors
If voltage modulation is applied to remove deposits during non-implant periods, then contamination is reduced, but energy is consumed during the modulation process
Solution Approach 1:
The system converts the harmful arc discharge phenomenon (which can cause uncontrolled contamination) into a beneficial cleaning mechanism by deliberately applying controlled voltage modulation during non-implant periods. The energy that would otherwise be wasted or cause problems is harnessed to remove deposits, transforming a potential harm into a useful function.
Solution Approach 2:
The voltage modulation for deposit removal is performed in advance during non-implant periods, before the next ion implantation cycle begins. This preliminary cleaning action ensures that electrodes are free of deposits before the next implantation, preventing contamination without interfering with the actual implantation 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
This approach effectively reduces particle contamination by removing deposits from the electrodes, ensuring cleaner ion beams and preventing contamination of workpieces during the ion implantation process.
Implementation Method 1
the suppression voltage is modulated, thereby inducing a current flow or an arc discharge through the extraction assembly to remove deposits on surfaces
Implementation Method 2
A filament is supported within the tubular body and emits electrons that heat the endcap through electron bombardment, thereby thermionically emitting ionizing electrons into the gas confinement chamber
Data Source
AI summary
A method is disclosed for reducing particle contamination in an ion implantation system, wherein an ion beam is created via the ion source operating in conjunction with an extraction electrode assembly. A cathode voltage is applied to the ion source for generating ions therein, and a suppression voltage is applied to the extraction assembly for preventing electrons in the ion beam from being drawn into the ion source. The suppression voltage is selectively modulated, thereby inducing a current flow or an arc discharge through the extraction assembly to remove deposits on surfaces thereof to mitigate subsequent contamination of workpieces. An improvement to an ion implantation system is also disclosed in accordance with the foregoing, wherein a controller is configured to selectively modulate a voltage between a predetermined voltage and a predetermined suppression voltage generally concurrent with the transferring of the workpiece, thereby inducing a current flow or an arc discharge through the extraction electrode assembly to remove deposits on surfaces thereof to mitigate subsequent contamination of workpieces.