Multi-grid ion beam source for generating a highly collimated ion beam

A method of tuning a focus grid potential in an ion beam source, the ion beam source being capable of generating a substantially collimated ion beam that sends ions toward a target along an axis extending between a plasma source and the target, the method comprising:

• providing an extraction grid spaced downstream from the plasma source along the axis and substantially normal to the axis, the extraction grid having a positive electrical extraction potential;
• providing an acceleration grid spaced downstream from the extraction grid along the axis between the extraction grid and the target and substantially normal to the axis, the acceleration grid having a non-positive electrical acceleration potential;
• providing a focus grid spaced downstream from the acceleration grid along and substantially normal to the axis between the acceleration grid and the target to focus the ions exiting the acceleration grid into a substantially collimated ion beam along the axis, the focus grid having an electrical focus potential;
• providing a shield grid spaced downstream from the focus grid along and substantially normal to the axis between the focus grid and the target;
• the shield grid having an electrical shield potential;
• detecting an angle of divergence of the ion beam;
• and
• altering the electrical focus potential until the detected angle of divergence of the ion beam is minimized.

An ion beam source for generating a substantially collimated ion beam sending ions toward a target along an axis extending between a plasma source and the target, the ion beam source comprising:

• an extraction grid spaced downstream from the plasma source along the axis and substantially normal to the axis, the extraction grid having a positive electrical extraction potential;
• an acceleration grid spaced downstream from the extraction grid along the axis between the extraction grid and the target and substantially normal to the axis, the acceleration grid having a non-positive electrical acceleration potential, the electrical extraction potential and the electrical acceleration potential operating in combination to extract the ions from the plasma source;
• a focus grid spaced downstream from the acceleration grid along and substantially normal to the axis between the acceleration grid and the target to focus the ions exiting the acceleration grid by changing momentum of the ions along the axis;
• and
• a shield grid spaced downstream from the focus grid along and substantially normal to the axis between the focus grid and the target to locate a neutralization plane near the shield grid.

A method of generating a substantially collimated ion beam sending ions toward a target along an axis extending between a plasma source and the target, the method comprising:

• applying a positive electrical extraction potential to an extraction grid spaced downstream from the plasma source along the axis and substantially normal to the axis;
• applying a non-positive electrical extraction potential to an acceleration grid spaced downstream from the extraction grid along the axis between the extraction grid and the target and substantially normal to the axis, the electrical extraction potential and the electrical acceleration potential operating in combination to extract the ions from the plasma source;
• applying an electrical focus potential to a focus grid spaced downstream from the acceleration grid along and substantially normal to the axis between the acceleration grid and the target to focus the ions exiting the acceleration grid by changing momentum of the ions along the axis;
• and
• applying an electrical shield potential to a shield grid spaced downstream from the focus grid along and substantially normal to the axis between the focus grid and the target to locate a neutralization plane near the shield grid.

A grid optics system for extracting ions from a plasma source and propelling the ions toward a target in a substantially collimated ion beam directed along an axis extending between the plasma source and the target, the grid optics system comprising:

• extracting means for extracting the ions from the plasma;
• focusing means for focusing the ions exiting the extracting means by changing momentum of the ions along the axis, the focusing means being positioned between the extracting means and the target;
• and
• shielding means for locating a neutralization plane near the shielding means, the shielding means being positioned between the focusing means and the target.