Focused Ion Beams

1. Fabrication of a perforated filter from a 300nm thick silicon oxide membrane comparable in scale to the kidneys' endothelial cytoplasm

1. Load the as-prepared membrane into the FIB chamber. The membranes are often prepared by professionals (when creating Wheatstone bridges) and can be acquired at semiconductor fabrication sites. To prepare one yourself, photolithography must be used. The details of this process can be seen in the photolithography video of the "Bioengineering Collection" on the JoVE website. NOTE: Be certain to wear nitrile gloves when handling the sample or when coming in contact with any internal components of the FIB/SEM. The environment must be kept very clean and free of any skin oils.
2. Turn the focused ion beam and electron gun on and adjust the sample to achieve the coincident-eucentric point. This is the point where the area of interest (the membrane) is in the line of electrons and ions for tilt angles ranging from 0-54 degrees.

3. Adjust the ion beam current and accelerating voltage of the FIB to 30kV and 100pA and focus on an area close to the area to be milled. Draw a matrix of circles through the FIB milling program of a diameter around 50nm with a center to center distance of 150nm (see Figure 1).
4. Change to electron beam and image the area at an accelerating voltage of 5kV.

Figure 1: FIB milled holes in silicon oxide membrane creating particle filter.

2. Milling a logo on a hair

1. Put a hair strand on a microscope stub using carbon tape
2. Gold/Carbon coat the hair strand using a sputter coater. This tool coats the sample in a few nanometers of a conductive material so it can be imaged/sputtered with minimal charging artifacts.
3. Turn the focused ion beam and electron gun on and adjust for the coincident-eucentric point.
4. Adjust the ion beam current and accelerating voltage to 30kV with a 100pA aperture, respectively, and focus on an area of about 15um x 15um close to the area to be milled.
5. Load the pattern/logo to be milled as a bitmap and adjust the beam current and accelerating voltage and start the milling.
6. Change to electron beam and image the area. This is shown in Figure 2.

Figure 2: "Happy Holidays" milled on a spider web with FIB.