AFM - Atomic force microscope

For 4 inch wafer inspection in the cleanroom.

The atomic force microscope (AFM) probes the surface of a sample with a sharp tip, a couple of microns long and often less than 100 Å in diameter. The tip is located at the free end of a cantilever that is 100 to 200 μm long. Forces (10−8−10−6 N) between the tip and the sample surface cause the cantilever to bend, or deflect. A detector measures the cantilever deflection as the tip is scanned over the sample, or the sample is scanned under the tip. The measured cantilever deflections allow a computer to generate a map of surface topography. AFMs can be used to study insulators and semiconductors as well as electrical conductors.

Characteristics of the cantilever
  • Microscopic spring of length » 100 μm
  • The tip has a radius of R » 10 nm
  • The force constant k=0.01-0.5 N/m
  • Cantilevers are produced with microlithography
    This is one of the things we can do at ALSION.

    Contact (repulsive) mode: The tip makes soft "physical contact" with the sample, the tip is attached to the end of a cantilever with a low spring constant (lower than the effective spring constant holding the atoms of the sample together), the contact force causes the cantilever to bend to accommodate changes in topography.

    Non−contact / intermittent contact: The AFM cantilever is vibrated near the surface of a sample with spacing on the order of tens to hundreds of angstroms for non−contact or touching of the surface at lowest deflection for intermittent contact ("tapping mode").

    Phase mode: compare phase of driving signal and cantilever response is compared
    This gives information on elastic modulus of the surface material.

    Our instrument from Veeco accepts samples up to 200 mm for semiconductor wafers, lithography masks, magnetic media, CDs/DVDs, biomaterials. The Dimension 3100 performs all the major SPM techniques to measure surface characteristics. Company link

    Atomic force microscope (JPK NanoWizard)
    It is situated in our microscopy lab. The instrument allows microscopy in liquids and is situated on an inverted fluorescence microscope.

    Additional options compared to Veeco Dimension 3100: Force distance curve measurements; heatable sample stage; EFM (electrical scanning microscopy).

    Top and bottom optical inspection is possible.

     Company link