Toshio Seki

Nano-Processing with Gas Cluster Ion Beams

Abstract This paper describes the fundamental principles and experimental status of gas cluster ion beam (GCIB) processing as a new technique with promise for practical industrial applications. A review is presented of the theoretical and experimental characteristics of new gas cluster ion bombardment processes and of related equipment development. The impacts of accelerated cluster ions upon substrate surfaces impart very high-energy densities in the impact regions of individual clusters and produce non-linear processes that are not present in the impacts of individual atomic ions. These unique bombardment characteristics are expected to facilitate new industrial applications that would not be possible by traditional ion beam processing. Among these are shallow ion implantation, high rate sputtering, surface cleaning and smoothing, and low-temperature thin film formation.

High‐Speed Nano‐Processing with Cluster Ion Beams

The gas cluster ion beam process has a high potential for material processing in nano‐technology devices, such as photonic crystals, thin film transistors (TFTs) and micro‐electromechanical systems (MEMS). In order to fabricate the devices, one needs to etch target materials with a high‐speed, low‐damage and ultra‐smooth process. Extremely high rate sputtering was realized by high‐energy cluster ion beam. We have been using this technique for poly‐Si TFTs. There are many hillocks on poly‐Si films formed by using a laser anneal technique, and they cause degradation of devices. When the laser crystallized poly‐Si film was irradiated with cluster ion beam, the higher hillocks could be etched selectively and the surfaces of poly‐Si films could be processed with low ion dose. High‐speed nano‐processing was realized by cluster ion beam.

Investigation of Damage with Cluster Ion Beam Irradiation Using HR-RBS

Cluster ion beam can process targets with shallow damage because of the very low irradiation energy per atom. However, it is needed to investigate the damage with cluster ion beam irradiation, because recent applications demand process targets with ultra low damage. The shallow damage can be investigated from depth profiles of specific species before and after ion irradiation. They can be measured with secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectroscopy (RBS). High resolution Rutherford backscattering spectroscopy (HR‐RBS) is a non destructive measurement method and depth profiles can be measured with nano‐resolution. The cluster ion beam mixing of thin Ni layer in carbon targets can be investigated with HR‐RBS. The mixing depth with cluster ion irradiation at 10 keV was about 10 nm. The mixing depth with cluster ion irradiation at 1 keV and 5 keV were less than 1 nm and 5 nm, respectively. The number of displaced Ni atoms with cluster ion irradiation was very larger than tha...