Accelerated neutral atom beam (ANAB) technology for nanoscale surface processing

Many difficulties and limitations of surface processing by traditional ion beam techniques are associated with the electrical charges that are fundamental to ion acceleration. Flux neutralization approaches used to minimize space charge repulsion effects and neutralization methods employed to avoid surface charge accumulation and damage phenomena complicate the use of ion beams in many situations, particularly so as device dimensions approach nano-scale. It has long been recognized that simplified fabrication processes and superior nano-level processing capabilities would be possible if process beams comprised of only neutral atoms having adequate and controllable energies could be generated. The obstacle to creating such beams has always been the problem of how to remove all electrical charges from a beam of ionized atoms after acceleration. This paper describes a method known as Accelerated Neutral Atom Beam (ANAB) in which energetic neutral atoms are produced by causing large numbers of neutral atoms to be released from the individual gas clusters within a stream of high energy gas cluster ions and then using an electrostatic field to eliminate residual charged species from the beam. The ANAB technique provides high flux collimated beams of energetic neutral atoms that have average energies which are controllable from less than 10 eV per atom to more than 100 eV per atom, a range found to be ideal for many nano-scale surface modification actions. Available neutral beam species include virtually any element or molecule that exists as a gas at room temperature. ANAB processes are useful for precise sputtering, nano-level surface smoothing, extremely shallow doping, highly selective etching, ultra-thin film deposition, surface passivation, various surface specific molecular transformations, and for a range of other ultra-shallow surface actions. Due to its highly collimated nature, ANAB offers excellent performance for nano-scale patterning and for uniform depth processing of structural geometries with varied aspect ratios. ANAB is being employed in a number of areas, including medical implants, other medical and biological devices, optics, MEMS, semiconductors, and metrology.