Plasma Immersion Ion Implanter Control Phase Overlap
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Solution Overview
Problem
Ion implanters in plasma immersion mode face issues with rapid decrease in implantation current due to sheath growth, leading to unstable acceleration voltage and contamination risks, necessitating a method to stabilize and neutralize positive charges on the substrate.
Innovation Solution
A method involving a control module with a substrate power supply and plasma power supply, including an initialization phase for stabilizing substrate voltage, an activation phase for igniting plasma, an extinction phase for deactivating plasma, and a neutralization phase with a relaxation phase where the plasma supply is inactivated to neutralize positive charges, followed by a cancellation step to activate plasma supply and stabilize implantation parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the plasma supply is activated during the neutralization phase, then positive charges on the substrate are neutralized effectively, but the implantation current decreases rapidly due to sheath growth
Solution Approach 1:
The control method segments the operation into distinct phases: implantation phase, relaxation phase, and neutralization phase. During the neutralization phase, the plasma supply is activated only after the substrate voltage has stabilized, separating the charge neutralization function from the implantation function to avoid current decrease
Solution Approach 2:
The method introduces a relaxation phase before the neutralization phase, where the substrate voltage is stabilized first. This preliminary action ensures that when plasma is activated for neutralization, the sheath thickness is controlled and implantation current does not decrease rapidly
2Manufacturing precision
If the substrate voltage is stabilized before plasma activation, then implantation parameters remain constant, but the overall process time increases
Solution Approach 1:
The control method uses periodic pulsed operation where the substrate supply and plasma supply are activated in alternating phases. The substrate voltage is stabilized during the implantation phase, then plasma is activated during the neutralization phase, creating a periodic cycle that maintains precision while managing time
Solution Approach 2:
The method maintains continuous useful action by overlapping the relaxation phase with the implantation phase and ensuring minimal idle time between cycles. The substrate voltage stabilization occurs during the implantation phase itself rather than as a separate preparatory step
3Productivity
If the plasma supply remains active during voltage stabilization, then ion implantation can proceed continuously, but the acceleration voltage becomes unstable
Solution Approach 1:
The operation is segmented into distinct phases where plasma activation is separated from voltage stabilization. During the implantation phase, substrate voltage is stabilized first; only after stabilization is achieved is plasma activated for the neutralization phase, ensuring voltage stability while maintaining implantation continuity across cycles
Solution Approach 2:
The method performs preliminary voltage stabilization during the implantation phase before activating plasma. This preliminary action ensures that when plasma is introduced, the acceleration voltage is already stable, preventing voltage fluctuations that would occur if plasma were activated simultaneously with voltage application
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 stabilizes the implantation parameters, reduces contamination risks, and effectively neutralizes positive charges, maintaining constant substrate voltage and improving the ion implantation process by overlapping the relaxation and neutralization phases.
Implementation Method 1
an ion implanter in plasma immersion mode
Implementation Method 2
polarizing it in negative voltage... in order to create a electric field capable of accelerating the ions from the plasma to the substrate
Implementation Method 3
an ionic sheath around the substrate. The potential difference responsible for the acceleration of the ions towards the substrate is found at the terminals of this sheath
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a method of controlling an ion implanter comprising a plasma power supply (AP) and a substrate power supply (PS), said substrate power supply comprising: . - an electricity generator (HT), . - a first switch (SW1) connected between the generator and the output terminal of said substrate power supply, . - a second switch (SW2) connected between the output terminal and a neutralising terminal, method comprising an implantation phase (A-D) and a neutralisation phase (E-H). This method also comprises a relaxation phase (C-F) which overlaps the implantation phase and the neutralisation phase, relaxation phase during which the plasma power supply is inactivated. Furthermore, the neutralisation phase comprises a preliminary step (E-F) to close the second switch, said preliminary step being followed by a cancellation step (F-G) to activate the plasma power supply (AP). Figure to be published: figure 4.