Plasma potential modulated ion implantation system

Patent metadata

Field	Value
Publication number	US-9297063-B2
Application number	US-201213457451-A
Country	US
Kind code	B2
Filing date	Apr 26, 2012
Priority date	Apr 26, 2012
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

An ion implantation system including a plasma source, a mask-slit, and a plasma chamber. The plasma source is configured to generate a plasma within the plasma chamber in response to the introduction of a gas therein. The mask-slit is electrically isolated from the plasma chamber. A positive voltage bias is applied to the plasma chamber above a bias potential used to generate the plasma. The positive voltage bias drives the plasma potential to accelerate the ions to a desired implant energy. The accelerated ions pass through an aperture in the mask-slit and are directed toward a substrate for implantation. The mask-slit is electrically isolated from the plasma chamber and is maintained at ground potential with respect to the plasma.

First claim

What is claimed is:

1. An ion implantation apparatus, comprising:
a plasma chamber operable to produce a plasma, the plasma chamber defining a set of sidewalls and an end wall; and
an electrically conductive mask-slit disposed at a first end of the plasma chamber and electrically isolated from the plasma chamber, the mask-slit at a ground potential and positioned directly adjacent the plasma, the mask-slit further having an aperture configured to allow accelerated ions from the plasma to pass therethrough for implantation into a substrate disposed on a platen, and the mask-slit and the platen extending laterally beyond a plane defined by each of the set of sidewalls of the plasma chamber.

2. The ion implantation apparatus of claim 1 wherein the ions pass through the aperture of the mask-slit in response to a voltage bias applied to the plasma chamber.

3. The ion implantation apparatus of claim 2 wherein the voltage bias applied to the plasma chamber being configured to bias the plasma within the plasma chamber more positively than with respect to the mask-slit.

4. The ion implantation apparatus of claim 2 wherein the voltage bias applied to the plasma chamber being configured to bias the plasma within the plasma chamber more positively with respect to the mask-slit and the substrate.

5. The ion implantation apparatus of claim 1 wherein the mask slit is electrically isolated from the plasma chamber by an insulated spacer.

6. The ion implantation apparatus of claim 1 , wherein the mask-slit has a curved profile proximate the aperture to control a trajectory of the ions toward the substrate.

7. The ion implantation apparatus of claim 1 wherein the aperture is a first aperture, the mask-slit having a second aperture configured to direct ions from the plasma to pass therethrough toward the substrate.

8. The ion implantation apparatus of claim 1 wherein a plasma sheath is defined between the plasma within the chamber and the mask-slit, the ions from the plasma being accelerated across the sheath through the aperture of the mask-slit when the voltage bias is applied to the plasma chamber.

9. The ion implantation apparatus of claim 8 wherein the aperture has a width, a ratio is defined between the width and a thickness of the plasma-sheath to control directionality of the beam.

10. The ion implantation apparatus of claim 1 comprising a voltage source connected to the plasma chamber configured to supply the voltage bias to the plasma chamber, wherein the voltage source is pulsed defining a duty cycle having a pulse-ON period and a pulse-OFF period, the pulse-ON period configured to apply the voltage bias to the plasma chamber.

11. The ion implantation apparatus of claim 10 wherein the aperture is a first aperture and the bias voltage is a first bias voltage, the apparatus further comprising an electrically conductive beam gate disposed between the substrate and the mask-slit, the beam gate having a second aperture aligned with the first aperture and configured to be independently biased such that the beam gate receives a second bias voltage corresponding to the pulse-ON period of the voltage bias applied to the plasma chamber.

12. The ion implantation apparatus of claim 1 wherein the plasma chamber is maintained at a first pressure and an area defined between the mask-slit and the substrate is maintained at a second pressure, the first pressure being greater than the second pressure.

13. The ion implantation apparatus of claim 1 wherein the mask-slit includes a flexible portion capable of having a curved profile proximate the aperture to control a trajectory of the ions from the plasma toward the substrate.

14. A method of implanting a workpiece in an ion implantation system, comprising:
generating a plasma within a plasma chamber, the plasma chamber defining an end wall and a set of sidewalls;
applying an extraction voltage to the plasma chamber to accelerate ions from the plasma towards a platen securing the workpiece;
electrically isolating the plasma chamber from a mask-slit disposed between the plasma chamber and the workpiece, the mask-slit at a ground potential and positioned directly adjacent the plasma, and the mask-slit and the platen extending laterally beyond a plane defined by each of the set of sidewalls of the plasma chamber; and
applying a voltage bias lower than the extraction voltage to the mask-slit and the workpiece, the accelerated ions directed toward an aperture in the mask-slit during a portion of a pulsed extraction voltage.

15. The method of claim 14 further comprising controlling a trajectory of the ions toward the workpiece by providing the mask-slit with a curved profile proximate the aperture.

16. The method of claim 14 further comprising accelerating the-ions across a sheath defined between the plasma within the plasma chamber and the mask-slit during the portion of the applied extraction voltage.

17. The method of claim 14 further comprising flexing a portion of the mask-slit proximate the aperture to control a convergence of the ions toward the workpiece.

18. The method of claim 14 further comprising flexing a portion of the mask-slit proximate the aperture to control a divergence of the ions toward the workpiece.

19. The method of claim 14 wherein the aperture is a first aperture and the extraction voltage is a first bias voltage, the method further comprising applying a second bias voltage to an electrically conductive beam gate disposed between the workpiece and the mask-slit, the electrically conductive beam gate independently biased using a power source.

20. The method of claim 19 wherein the second bias voltage is applied to the beam gate corresponding to a portion of the pulsed extraction voltage portion applied to the plasma chamber.

Assignees

• Radovanov Svetlana B
• Benveniste Victor M
• Koo Bon-Woong
• White Richard M
• Daniels Kevin M
• Varian Semiconductor Equipment

Inventors

• Radovanov Svetlana B
• Benveniste Victor M
• Koo Bon-Woong
• White Richard M
• Daniels Kevin M

Classifications

• C23C16/042

  using masks · CPC title

• H01J2237/083

  Beam forming · CPC title

• H01J37/3171

  for ion implantation · CPC title

• H01J2237/0817

  Microwaves · CPC title

• H01J37/32357

  Generation remote from the workpiece, e.g. down-stream · CPC title