Apparatus and method for reducing differential sputter rates

A method of removing material from an area of a target, the method comprising;

• directing an ion beam toward the area of the target to alter the morphology of the material;
• directing an ion beam toward the area of the target to remove material from the target;
• and
• directing an ion beam toward the area of the target to produce a predetermined topography at the target area,
• wherein altering the morphology of the material reduces the effects of the crystal structure of the material to allow uniform removal of the material.

An ion beam system for removing material from an area of a target, comprising:

• an ion source for providing ions;
• ion optical elements for forming ions from the ion source into a beam having a diameter and directing the beam toward an area on a target;
• a gas injection system for directing a precursor gas toward the target to form under bombardment of the ion beam a sacrificial layer,
• the ion optical elements and the gas injection system being adjusted to deliver ions and precursor gas at rates such that during each dwell period, a layer of decomposition products is formed, interacts with ion beam in etching the material, and is itself substantially removed so that etching of the material is substantially uniform over the area on the target with the decomposition products substantially removed.