Neutral beam technology — Defect-free nanofabrication for novel nano-materials and nano-devices

In the fabrication of semiconductor devices, reactive plasmas are widely used in key processes such as microfabrication, surface reforming and film deposition, and there are now demands for processing precision at the atomic layer level, and for deposition accuracy that allows the control of structures at the molecular level. However, in ultra-miniature nanoscale devices that will become the mainstream in the future, the use of plasma processes can cause serious problems such as abnormal etching and damage to insulation films by the accumulation of ions or electrons emitter from the plasma as shown in Fig. 1, or the formation of surface defects of over 10 nm in size by exposure to vacuum ultraviolet or other emissions.^1-4) In particular, since nanodevices have a large surface area compared with the bulk material, plasma processes can have a large effect on the electrical and chemical properties of devices due to process-induced defects caused by ultraviolet exposure, which has not caused a problem in conventional processes. Furthermore, since future nanodevices will require dimensional control of three-dimensional structures at the atomic layer level, it will be absolutely essential to control surface chemical reactions with high precision and selectivity at the atomic layer level. Neutral beam process technology (developed by S. Samukawa) has attracted attention as a way of solving these issues.^5-8) The neutral beam suppresses the incidence of charged particles and electromagnetic radiation onto the substrate, and is able to expose the substrate only to neutral particles with high kinetic energy, resulting in ultra-precise nanoprocessing that can suppress the formation of defects at the atomic layer level and control surface chemical reactions with high precision. This paper introduces the neutron beam generation technique developed by S. Samukawa, and discusses its application to nanoprocessing and nanodevices that have recently been vigorou- ly pursued.