Modulator for plasma-immersion ion implantation

A plasma immersion ion implantation system, comprising

• an implantation chamber defining a chamber interior receivable of ion plasma and at least one workpiece for ion treatment;
• a support arranged in said chamber interior for positioning the at least one workpiece within said chamber interior such that an implantation surface of the at least one workpiece is exposed to ion plasma;
• a voltage generator in electrical communication via a resistor and a capacitor with said support for applying electrical pulses for attracting ions to said support, said capacitor having a first pole coupled to said support and a second pole;
• and
• a modulator for modulating the electrical pulses applied to said support, said modulator comprising:
• an electrode arranged in said chamber interior and electrically coupled to said second pole of said capacitor;
• shielding means for shielding said electrode from the ion plasma in said chamber interior;
• and
• a pulse generator connected to said shielding means for generating negative voltage pulses which isolate said electrode from electron conduction with the plasma when present and whereby conduction between the electrode with the plasma occurs when the negative voltage pulses are not present.

A method for implanting plasma ions into a workpiece, comprising the steps of:

• arranging the workpiece on a support in an interior of a plasma-containing implantation chamber;
• electrically coupling the support to a high voltage source via a resistor and a capacitor, the capacitor having a first pole coupled to the support;
• and
• modulating the flow of high voltage from the high voltage source to the support by:
• exposing an electrode in the implantation chamber;
• electrically connecting the electrode to the second pole of the capacitor;
• arranging a grid around the electrode;
• connecting a pulse generator capable of generating negative voltage pulses to the grid such that when the negative voltage pulses are applied to the grid, the electrode is shielded from conduction with plasma in the implantation chamber;
• and
• controlling the pulse generator such that the electrode is alternatingly shielded from conduction with the plasma when negative voltage is applied to the grid by the pulse generator or in electrical contact with the plasma when the negative voltage is not applied to the grid by the pulse generator.