Hybrid focused-flood ion beam system and method

In an ion beam microfabrication system of the type having a means for supporting a substrate upon which an electrical circuit is to be fabricated, an ion beam source, a focusing lens positioned to focus the beam emerging from the source to a first crossover, a mass separator positioned to remove undesired particles from the beam, a first accelerating lens positioned in the vicinity of the first beam crossover to accelerate the beam, a final accelerating lens positioned to further accelerate and focus the beam to a small spot on the substrate, and means for deflecting the spot over the substrate in a desired pattern, the improvement comprising:

• means for positioning a mask in close proximity to the substrate,
• a control lens capable of being switched between actuated and de-actuated states, the control lens being positioned between the first and final accelerating lenses to focus the beam from the first accelerating lens to a second crossover in the vicinity of the final accelerating lens focal point when the control lens is actuated, thereby causing the final accelerating lens to substantially flood a portion of the mask and underlying substate, and to pass the beam to the final accelerating lens without substantial change when the control lens is de-actuated, thereby permitting the final accelerating lens to focus the beam to a small spot on the substrate, and
• a switch means for selectively switching the control lens between actuated and de-actuated states.

A method of forming an integrated circuit, comprising the steps of:

• forming an divergent ion beam,
• focusing the beam to a small spot on a substrate during a focused beam mode, and deflecting the focused beam over a portion of the substrate in a desired pattern,
• positioning a circuit pattern mask between the beam and the substrate, and altering the beam collimation during a flooded beam mode so that the beam substantailly floods at least a portion of the mask to establish a mask pattern on the underlying substrate, and
• selecting between the focused and flooded beam operating modes.

A method of forming an integrated circuit, comprising the steps of:

• forming a divergent ion beam,
• focusing the beam to a first crossover,
• removing undesired particles from the beam,
• providing a first acceleration to the beam without substantially altering its collimation, and
• selecting between focused beam and flooded beam operating modes,
• the focused beam operating mode comprising the steps of providing a final acceleration to the beam, focusing the beam to a small spot on a substrate, and deflecting the focused beam over a portion of the substrate in a desired pattern, and
• the flooded beam operating mode comprising the steps of focusing the beam to a second crossover, providing a final acceleration to the beam after said scond crossover, focusing the beam after said second crossover to a substantially collimated cross-section, and positioning a circuit pattern mask betwen the collimated beam and the substrate to establish a mask pattern on the underlying substrate.