Surface erosion by highly-charged ions

Abstract

Interaction of single- and highly-charged ions (HCI) with solid surfaces is a key factor for the development of extreme ultra-violet lithography (EUVL) source devices. To understand the mechanisms of surface erosion by ion bombardment, molecular dynamics (MD) simulation models of hollow atom formation, charge neutralization, electric field screening, surface sputtering and crater formation were developed. These models were applied to studies of erosion of Au, W and Si surfaces irradiated by singly-charged Xe+ ions. Surface erosion of a Si(100) surface by low energy HCI bombardment has been modeled by studying interactions of slow Xeq+ ions. Further development and application of the MD methods to erosion of conductive surfaces by HCIs is analysed. The sputtering yield of insulators and semiconductors by HCI impacts significantly increases with the charge state of the ion and leads to surface roughening via crater formation for higher charge states. This phenomenon has been studied based on the mechanisms of “Coulomb explosion” and “thermal spike”. The calculated sputtering yields of various surfaces bombarded by low energy single-charged Xe+ ions and highly-charged Xeq+ ions are compared with available experimental data.