Gas Injection System (GIS)

The multi-GIS is used in conjunction with the Zeiss Crossbeam 550 for a multitude of purposes.
photo of inside of XB550

Introduction

Gas Injection System (GIS) provides precursor reactive gas sources to reduce charging effect from both electron and ion beams, to assist in enhanced etching, to reduce the curtaining effect on the cross sections generated by FIB milling, and to locally reduce the charging effect on non-conductive samples etc.

Deposition

  • On the system here at PEMC, three different materials can be deposited using either the ion beam or the electron beam, which are platinum (Pt), carbon (C) and tungsten (W).
  • Generally this is used to protect the sample and reduce curtaining effects on the cross-section during ion beam milling.
  • Almost any shape can be deposited, either using the shapes and text provided by the software or importing an image, which would then be converted to a binary image.
  • It can also be used to deposit conductive pathways in microelectronics.

FIB deposition
Before and after charge compensation

Charge compensation

  • The gas injection system (GIS) produces a localised gas cloud (nitrogen) just above the surface of the sample to neutralise charge.
  • Acts in a similar way to low vacuum mode in other SEMs, but only in a localised area above the sample.
  • The presence of the gas increases the mean free path of the incoming electrons.
  • The gaseous atoms become positively ionised and neutralises the negatively charged sample surface.
  • The gas cloud also ‘absorbs’ some of the emitted electrons to reduce charging.

Enhanced milling

  • The fifth gas that is available to use in this system in xenon fluoride, which is a corrosive to enhance ion beam milling.
  • Generally this gas is used to enhance the ion beam etching for silicon and silicon-based samples, such as semiconductors.
  • Additionally the xenon fluoride gas can be used to enhance the ion beam milling for all materials, but to a lesser extent compared with silicon materials.

xenon fluoride etching comparison

Available equipment