TSOM
Through-Focus Scanning Optical Microscopy (TSOM) is an imaging method that produces nanometer-scale three-dimensional measurement sensitivity using a conventional bright-field optical microscope. TSOM has been introduced and maintained by Ravikiran Attota{{Cite web |url=https://www.nist.gov/pml/div683/grp03/rattota.cfm |title=Dr. Ravikiran Attota |access-date=2017-07-13 |archive-date=2016-06-16 |archive-url=https://web.archive.org/web/20160616183517/http://www.nist.gov/pml/div683/grp03/rattota.cfm |url-status=dead }} at NIST. It was given an R&D 100 Award in 2010.{{Cite web|url=http://www.rdmag.com/Awards/RD-100-Awards/2010/08/Bringing-out-of-focus-into-the-picture/|title = Research & Development World}} In the TSOM method a target is scanned through the focus of an optical microscope, acquiring conventional optical images at different focal positions. The TSOM images are constructed using the through-focus optical images. A TSOM image is unique under given experimental conditions and is sensitive to changes in the dimensions of a target in a distinct way, which is very well applicable in nanoscale dimensional metrology. The TSOM method is alleged to have several nanometrology{{Cite web | url=https://www.nist.gov/pml/div683/grp03/upload/tsom-ravikiran-attota.pdf | title=Nanoscale Measurements With TSOM* Optical Method | first=Ravikiran | last=Attota | website=www.nist.gov}}{{Cite web| author1=Ravikiran Attota | author2=Ronald G. Dixson | author3=Andras E. Vladár | title=Through-focus scanning optical microscopy | website=www.spiedigitallibrary.org| date=2011-06-01 | url=http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1265236 | doi=10.1117/12.884706}}{{cite journal | last1 = Attota | first1 = R. | last2 = Bunday | first2 = B. | last3 = Vartanian | first3 = V. | year = 2013 | title = Critical dimension metrology by through-focus scanning optical microscopy beyond the 22 nm node | journal = Appl. Phys. Lett. | volume = 102 | issue = 22| page = 222107 | doi = 10.1063/1.4809512 | bibcode = 2013ApPhL.102v2107A | doi-access = free }}{{cite journal | last1 = Attota | first1 = R. | last2 = Dixson | first2 = R.G. | year = 2014 | title = Resolving three-dimensional shape of sub-50 nm wide lines with nanometer-scale sensitivity using conventional optical microscopes | journal = Appl. Phys. Lett. | volume = 105 | issue = 4 | page = 043101 | doi = 10.1063/1.4891676 | bibcode = 2014ApPhL.105d3101A | doi-access = free }}{{cite journal | last1 = Attota | first1 = R. | last2 = Kavuri | first2 = P.P. | last3 = Kang | first3 = H. | last4 = Kasica | first4 = R. | last5 = Chen | first5 = L. | year = 2014 | title = Nanoparticle size determination using optical microscopes | journal = Appl. Phys. Lett. | volume = 105 | issue = 16| page = 163105 | doi = 10.1063/1.4900484 | bibcode = 2014ApPhL.105p3105A | doi-access = free }}{{cite journal | last1 = Kang | first1 = H. | last2 = Attota | first2 = R. | last3 = Tondare | first3 = V. | last4 = Vladar | first4 = A.E. | last5 = Kavuri | first5 = P. | year = 2015 | title = A method to determine the number of nanoparticles in a cluster using conventional optical microscopes | journal = Appl. Phys. Lett. | volume = 107 | issue = 10| page = 103106 | doi = 10.1063/1.4930994 | bibcode = 2015ApPhL.107j3106K }} applications ranging from nanoparticles to through-silicon-vias (TSV).
The National Institute of Standards and Technology, USA, produced a short {{YouTube | CIDjkH1L95M }} on the TSOM method.