Nanometer Step Height Standard

Sest, Inc. engineer in collaboration with NASA Glenn Research Center and Ohio Aerospace Institute (OAI) scientists, have developed a greatly improved diagnostic tool to evaluate and verify the operation and calibration of scanning probe microscopy (SPM) instruments used for measuring nanoscale objects meeting a vitally important need for the nanotechnology field that is expected to grow dramatically over the next decade.

The Nanometer Step Height Standard (Nanometer SHS) is a calibration standard chip made of single-crystal SiC. The small SiC chip contains an array of over a hundred step pyramids like those shown in the highly magnified atomic force microscope image.

Each side of the nanoscale step pyramid features regularly spaced steps nearly one micrometer apart with atomically flat terraces between step risers of either 0.5 or 1.0 nanometers in height, as chosen during fabrication. These step heights are around 10 times smaller than those of previous standards for scanning probe microscopy (SPM) instrument calibration.

The height of the steps is directly linked to the height of the SiC atomic crystal structure, which is a well-known physical constant. Therefore, the SiC Nanometer SHS beneficially avoids the expensive and time-consuming requirement for previous standards to be individually calibrated and certified by the National Institute of Standards and Technology (NIST).

The nanoscale step structures are produced on the top surfaces of commercial SiC wafers using conventional microelectronics photolithographic patterning and reactive ion etching processes, followed by high temperature (> 1000 °C) SiC epitaxial growth and etching pioneered by the Glenn research team. This process enables hundreds of Nanometer SHS chips to be mass-produced from a single SiC wafer, which should greatly increase the availability and affordability of precision SPM calibration for micro- and nano-technologies worldwide.