Jointly organised by SIMTech (Singapore Institute of Manufacturing Technology), NMC (National Metrology Centre) and OPSS (Optics and Photonics Society of Singapore), this lecture will discuss on-going work at the US NIST (National Institute of Standards and Technology) by leveraging atomic force microscopy (AFM) to develop methods and calibration standards for nanometer-scale linewidth and step height metrology. The properties of linewidth and step height are of growing importance to the function and specification of semiconductor devices – as well as other nano-devices – with sub-40 nm dimensions. The ability to manufacture ever-smaller linewidths leads to semiconductor elements with increased performance and improved storage density. However, control of linewidth requires accurate measurement to determine whether manufacturing specifications are being met. NIST has developed physical standards for linewidth known as the Single-Crystal Critical-Dimension Reference Material (SCCDRM). The standards consist of silicon chips whose surfaces contain six calibrated lines having widths ranging from about 70 nm to about 225 nm. These lines are fabricated using directional etching techniques, which produce vertical sidewalls and uniform widths. The lines have been measured by critical dimension atomic force microscopes whose probe-tip offsets are determined by use of high-resolution transmission electron microscopy. The uncertainty of the calibrated linewidths is as low as ±1 nm (k = 1). This uncertainty has been recently supported by independent experimental comparisons (R. Dixson and N.G. Orji, Proc. SPIE 6518, 2007). Step heights in the nanometer range provide a source of calibration in the z-direction for AFMs used to measure surface roughness and step heights at their highest levels of resolution. Traceable, commercially available, step-height standards may be obtained with heights as low as 8 nm. For calibration of smaller steps, NIST has performed measurements of the 0.3 nm lattice-based step height on the Si (111) crystal surface with an uncertainty of ± 4 pm (k = 1). This independent result has been considered together with the value derived from results from X-ray diffraction of bulk silicon and other results from X-ray and electron diffraction to provide a recommended calibration value of the Si (111) step height of 312 pm ± 12 pm, which is then useful for calibrating atomic force microscopes working at their highest levels of magnification. Subsequently, a documentary standard was published by the American Society for Testing and Materials, ASTM E2530-06, which describes the calibration procedure. In addition, in collaboration with the National Aeronautics and Space Administration (NASA) Glenn Research Center (J.A.Powell et al. Materials Science Forum 483-485, 2005), NIST has developed a similar procedure for calibration and use of lattice-based, 1 nm step-height standards fabricated from SiC.
About the Speaker
Dr Theodore Vorburger is a Guest Researcher and Former Group Leader of the Surface and Microform Metrology Group in the Precision Engineering Division at the National Institute of Standards and Technology. This group is responsible for surface roughness and step height calibrations, which underpin the U.S. measurement system for surface finish, and for traceable linewidth measurements using critical dimension atomic force microscopes. A co-leader of a project to develop standard bullets and standard casings for forensics laboratories, Dr Vorburger has also led the development of a calibrated atomic force microscope for calibrations of surface nano-scale length specimens, the development of atom-based step height standards for calibration of atomic force microscopes, and the development of a light scattering system for measuring surface roughness, and has collaborated in the development of the world’s first sinusoidal-roughness Standard Reference Materials. He is a member and former Chair of the American Society of Mechanical Engineers Standards Committee B46 on the Classification and Designation of Surface Qualities and a Subject Matter Expert for the equivalent Working Group under the International Organisation for Standardisation (ISO). He has been working in Surface Metrology since 1976 and is the author or co-author of more than 200 publications in the fields of surface metrology, nanometrology, surface physics, atomic physics, chemical physics, and automated measurements. Between March 2007 and April 2008, he worked on detail as Acting Deputy Director of the Center for Nanoscale Science and Technology, a new organisational unit of NIST. He holds a B.S. degree from Manhattan College and an M.S. and PhD from Yale University, all in Physics.
10.00am Public Lecture by Dr Theodore Vorburger
Who Should Attend
Managers, engineers, academic staff and researchers from semiconductor, electronics, optics, equipment and precision engineering related companies, research institutes, university and polytechnics.
Pre-registration for the lecture is necessary. Seats are reserved on a first-come, first-served basis. To reserve a place, please register online.
For technical enquiries:
Dr Fang Zhongping, Senior Scientist, Precision Measurements Group, Email: zpfang@SIMTech.a-star.edu.sg
For registration & general enquiries:
Alice Koh, Email: firstname.lastname@example.org; Connie, Email: Bahsh@scei.a-star.edu.sg