A focused ion beam system with a retarding mode objective lens

Abstract

Emerging focused ion beam application (FIB) require that the incident ion range and lateral scattering be variable. It is desirable that the energy change required to alter the ion range produce a minimal variation of the incident beam diameter and current. A new FIB system with an energy range from 5 to 70 keV has been developed to meet these requirements. In order to produce a low energy fine ion beam with a high current density we have designed a column with two objective lens elements in tandem. The first element is a conventional einzel lens while the second is a retarding mode immersion lens. This immersion lens can also be operated as a short working distance einzel lens during high energy operation. In this paper the construction of the ion optical system and its performance are discussed. Initial results from ion induced secondary electron images demonstrates 100 nm resolution and a 20 nm resolution at 69 keV.