THE MOLECULAR MEASURING MACHINE

To help meet the measurement needs of industries preparing to manufacture future generations of nanoelectroni c devices and circuits, the National Institute of Standards and Technology (NIST) has designed and built an instrument—ca lled the Molecular Measuring Machine (M 3 )—with the goal of measuring with one nanometer combined standard uncertainty the positions of features located anywhere within a 50 mm by 50 mm area. Achieving this capability for M 3 has required the development and integration of many forefront technologies: atomic-resolution scanning probes, high-accuracy interferometry for displacement measurements, and precision nanomotion generation. These have been combined in a controlled environment featuring ultra-high vacuum, acoustic and seismic vibration isolation, and millidegree-stability temperature control. In one demonstration of its capabilities, using the scanning tunneling microscope probe, M 3 imaged an array of laser-focused , atomically deposited chromium lines over a 5 μm by 1 mm area. An analysis of the image data yielded an average line spacing of 212.69 nm with an estimated expanded uncertainty of 0.01 nm, coverage factor, k, of two. This is based on a point-to-point expanded uncertainty of 50 nm (k = 2) for a 1 mm length measurement. In another measurement, the scanning tunneling microscope probe was able to continuously track a holographicall y-produced grating surface for 10 mm, counting out 49,996 lines and measuring an average line spacing of 200.01 nm with an expanded uncertainty of 0.01 nm (k = 2). This grating is now being used as a reference standard in the production of a spectrometer for the space-borne Advanced X-ray Astrophysics Facility being built by the National Aeronautics and Space Administration. Currently M 3 is undergoing a series of modifications . The motion actuators and guides are being refined, additional environmental and position sensors are being added, and a new machine controller system is being developed. These improvements should enable the capability for point-to-point measurements approaching the original goal. In addition to its measurement functions, M 3 can also serve as a tool for exploring methods of manufacturing mechanical and electrical structures in the nanometer-size range.