DB235 Focused Ion Beam (FIB) Laboratory

The instrument is an FEI Strata 235DB dual-beam FIB/SEM, containing both a focused Ga+ ion beam column ("Magnum") and a high resolution field emission scanning electron ("Sirion") column. The utility of the columns is enhanced by the ability to selectively deposit Pt or insulator with either of the two beams and rapidly etch many insulating materials using XeF2. Further, there is an Omniprobe® micromanipulator within the chamber that can measure electrical properties as well as position devices with nanoscale precision. The instrument is located in the Stanford Nanocharacterization Laboratory, on the first floor of McCullough Building, Room 105.

Capabilities:

• Imaging: Secondary electrons or ions produced by the incoming electron or Ga+ beams are collected to form an image of the sample. Five different detectors (including a STEM detector) give users tremendous flexibility in achieving the proper imaging conditions for their sample.
  • Ion column
    • Accelerating voltage: 10 – 30 kV
    • Resolution: 7 nm
  • Electron column
    • Accelerating voltage: 0.2 – 30 kV
    • Resolution: 3 nm
• Milling/Etching: The FIB can locally etch the sample surface with submicron precision. Many variables and material properties affect the sputtering rate of a sample. These include beam current, sample density, sample atomic mass, and incoming ion mass. The main ion species used at SNL is Ga+. Additionally, Insulator Enhanced Etching (IEE) using XeF2 is available. When the gas is introduced near the surface of the sample during milling, the sputtering yield can increase depending on the chemistry between the gas and the sample. This results in less redeposition and more efficient milling.
  
• Deposition: Conductive or insulator material can also be deposited with the aid of a gas in close proximity to the sample surface. Our system is equipped to deposit either metal (Pt) or insulator (combined tetraethyl orthosilicate (TEOS) and water vapor). These materials can be deposited with either the ion or electron beam.
  
• Micromachining: The FIB can be utilized for micro- and nano-structural creation and/or modification. This can be accomplished by taking advantage of FIB's capability to very precisely remove material (via physical sputtering or using beam induced chemistry for enhancing material removal rate), to deposit material (using beam induced chemistry), to provide localized ion implantation, and to locally induce sample structural damage.
  
• Microchemical analysis: Element mapping and energy dispersive X-ray spectrometry (EDS) are available.
  
• Orientation imaging: Advanced diffraction and crystallographic analysis capabilities, based on electron backscatter diffraction (EBSD), are an integral part of our FIB system.
  
• Nanoscale manipulation: Capable of nanoscale manipulation of TEM membranes or other samples with an Omniprobe micromanipulator. This probe can also be used for localized electronic measurements.

Restrictions on samples

The sample material must be able to withstand a high vacuum environment without outgassing. It must be clean. It may be attached to the sample holder using any suitable SEM vacuum-quality adhesive. The sample must be electrically grounded to the sample holder to minimize sample charging. If the sample is nonconductive (plastic, fiber, polymer, or other substance with an electrical resistance greater than 1E10 ohms), the sample may be coated with a 200 – 300 Å layer of carbon or other conductor. Rough surfaced samples must be evenly coated from every direction. Biological, cloth and powder samples may require carbon or other conductive painting on portions of the sample that are hard to coat. The workstation can accommodate up to 150 mm (6") wafers.

Training and Service

FIB training is available on an as-needed basis. Basic training for inexperienced FIB users requires a minimum of three two-hour sessions (see training page for more detailed info). Additional training in specific FIB techniques (i.e., TEM sample preparation) is available on an as-needed basis following basic training. FIB users with prior experience will be trained at the level required.

FIB service may be available for projects where extensive instrument training is not practical. However, users must generally make or provide their own FIB-ready samples.

(information from FEI and NCEM)