Observation of a Si surface sputtered by an ion irradiation system using a prototype compact cluster ion source

Abstract

A prototype compact cluster ion source has been developed using a metal cluster complex as a low damage-sputtering source, since clusters are said to be effective for so-called “lateral sputtering”. Using a metal cluster complex ion gun the Si surface was successfully sputtered with high sputtering yield, and yet resulting in reasonably smooth surface for a sputtered depth of 10 nm. Using the prototype compact cluster ion source, an ion beam containing metal cluster complexes of Os 3(CO) 12 was generated with an acceleration energy of 10 keV and total fluence, N CB, of 5.2 × 10 12 ions ( I ave = 0.050 nA, time = 278 min). From the results of AFM and SEM measurements, the sputtered Si surface was found to be reasonably smooth for a sputtering depth of ∼ 10 nm. The sputtered Si portion was found to be a truncated (elliptical) cone. The volume was estimated to be 3.2 × 10 −9 cm 3, i.e., N Si, the number of removed Si atoms was about 1.6 × 10 14. Thus the sputtering yield, N Si/ N CB, was estimated to be as large as 30. Surface state characterization and contamination were investigated using XPS (X-ray photoelectron spectroscopy) and AES (Auger electron spectroscopy), showing there was no Os on the sputtered Si surface. These results show that this ion irradiation system using a prototype compact cluster ion source is capable of high rate sputtering resulting in a smooth sputtered surface without deposition, showing the possibility for small penetration depth leading to low damage sputtering, in other words, lateral sputtering due to simultaneous multi-atom bombardment.