A macroscopic model for focused-ion-beam-induced deposition

Abstract

A time-dependent model for focused-ion-beam-induced deposition is presented which explicitly takes the scanning strategy of the beam during deposition into account. The model differentiates between the contribution of the beam center and that of the beam wings, and contains all major experimental variables such as current density, focus size, scan speed, and frame time. The deposition rate has been measured for tungsten as a function of the major experimental variables. The model has been fitted to these data and is found to describe the various dependences very well. By use of the model inclusive of the parameters obtained from the fit, we can predict optimum deposition conditions. Furthermore, the model clarifies effects observed during deposition on the structured surface of an integrated circuit, such as redeposition of sputtered material and poor step coverage due to an impeded gas flow.