Method for ultra-shallow etching using neutral beam processing based on gas cluster ion beam technology

A method for controlled shallow etching of a surface of a substrate comprising the steps of:

• providing a reduced pressure chamber comprising an inert gas therein;
• forming a gas cluster ion beam comprising gas cluster ions within the reduced pressure chamber;
• accelerating the gas cluster ions to form an accelerated gas cluster ion beam along a beam path within the reduced pressure chamber;
• promoting fragmentation and/or dissociation of at least a portion of the accelerated gas cluster ions along the beam path;
• removing charged particles from the beam path to form an accelerated neutral beam along the beam path in the reduced pressure chamber;
• holding the substrate in the beam path;
• treating a portion of a surface of the substrate by forming an oxygen layer in the surface portion irradiating the portion with the accelerated neutral beam to form a shallow modified layer with an internal floor on the irradiated portion of the surface, the shallow modified layer, overlying unmodified substrate beneath;
• terminating the irradiation treatment and then chemically etching the surface including the irradiated surface portion and adjacent surface area having the shallow modified layer after stopping the irradiating with the accelerated neutral beam, to preferentially remove material in the shallow modified layer on the surface, with a higher etch rate than for unmodified surface portions;
• wherein the etching stops at the unmodified substrate, the internal floor serving as an etch stop.