Editing Photolithography (section)

== History ==

In the 1820s, [[Nicephore Niepce]] invented a [[Photography|photographic]] process that used [[Bitumen of Judea]], a natural asphalt, as the first [[photoresist]]. A thin coating of the bitumen on a sheet of metal, glass or stone became less soluble where it was exposed to light; the unexposed parts could then be rinsed away with a suitable solvent, baring the material beneath, which was then chemically etched in an acid bath to produce a printing plate. The light-sensitivity of bitumen was very poor and very long exposures were required, but despite the later introduction of more sensitive alternatives, its low cost and superb resistance to strong acids prolonged its commercial life into the early 20th century.

In 1940, Oskar Süß created a ''positive'' photoresist by using [[diazonaphthoquinone]], which worked in the opposite manner: the coating was initially insoluble and was rendered soluble where it was exposed to light.<ref>{{cite journal |author=Willson |first=C. G. |last2=Dammel |first2=R. R. |last3=Reiser |first3=A. |year=1997 |editor1-last=Tarascon-Auriol |editor1-first=Regine G |title=Photoresist materials: a historical perspective |journal=[[Proc. SPIE 3049|Advances in Resist Technology and Processing XIV]] |volume=3049 |page=28 |bibcode=1997SPIE.3049...28W |doi=10.1117/12.275826 |s2cid=136616549}}</ref> In 1954, Louis Plambeck Jr. developed the Dycryl polymeric letterpress plate, which made the platemaking process faster.<ref>{{cite web | title=Lithography | url=http://www.lib.udel.edu/ud/spec/exhibits/color/lithogr.htm}}</ref> Development of photoresists used to be carried out in batches of wafers (batch processing) dipped into a bath of developer, but modern process offerings do development one wafer at a time (single wafer processing) to improve process control.<ref name="Levinson-2005">{{cite book | url=https://books.google.com/books?id=EjMpqEy07bsC&dq=photolithography+track+system&pg=PA80 | title=Principles of Lithography | isbn=9780819456601 | last1=Levinson | first1=Harry J. | date=2005 | publisher=SPIE Press }}</ref>

In 1957 Jules Andrus patented a photolitographic process for semiconductor fabrication, while working at Bell Labs.<ref>{{Cite patent|number=US3122817A|title=Fabrication of semiconductor devices|gdate=1964-03-03|invent1=Jules|inventor1-first=Andrus|url=https://patents.google.com/patent/US3122817A/en}}</ref><ref name=":0">{{Cite journal |last=Stein |first=Eric |date=2018-01-01 |title=Fiction in the Integrated Circuit |url=https://www.academia.edu/40272048 |journal=TWU Master's Thesis |pages=49–50}}</ref> At the same time Moe Abramson and Stanislaus Danko of the US Army Signal Corps developed a technique for printing circuits.<ref name=":0" />

In 1952, the U.S. military assigned [[Jay W. Lathrop]] and James R. Nall at the [[National Bureau of Standards]] (later the [[Harry Diamond Laboratories|U.S. Army Diamond Ordnance Fuze Laboratory]], which eventually merged to form the now-present [[United States Army Research Laboratory|Army Research Laboratory]]) with the task of finding a way to reduce the size of electronic circuits in order to better fit the necessary circuitry in the limited space available inside a [[proximity fuze]].<ref name="Lathrop-2013">{{Cite journal|title=The Diamond Ordnance Fuze Laboratory's Photolithographic Approach to Microcircuits - IEEE Journals & Magazine|journal=IEEE Annals of the History of Computing|volume=35|pages=48–55|language=en-US|doi=10.1109/MAHC.2011.83|year=2013|last1=Lathrop|first1=Jay W.|s2cid=2562671}}</ref> Inspired by the application of photoresist, a photosensitive liquid used to mark the boundaries of rivet holes in metal aircraft wings, Nall determined that a similar process can be used to protect the germanium in the transistors and even pattern the surface with light.<ref name="Weightman-2015">{{Cite book|title=Eureka: How Invention Happens|last=Weightman|first=Gavin|publisher=Yale University Press|year=2015|isbn=978-0300192087|pages=[https://archive.org/details/eurekahowinventi0000weig/page/178 178–179]|url=https://archive.org/details/eurekahowinventi0000weig/page/178}}</ref> During development, Lathrop and Nall were successful in creating a 2D miniaturized hybrid integrated circuit with transistors using this technique.<ref name="Lathrop-2013" /> In 1958, during the IRE Professional Group on Electron Devices (PGED) conference in Washington, D.C., they presented the first paper to describe the fabrication of transistors using photographic techniques and adopted the term "photolithography" to describe the process, marking the first published use of the term to describe semiconductor device patterning.<ref name="Weightman-2015" /><ref name="comus2018">{{Cite web|url=http://www.computerhistory.org/events/bio/Jay,Lathrop|title=Jay W. Lathrop {{!}} Computer History Museum|website=www.computerhistory.org|language=en|access-date=2018-06-18}}</ref>

Despite the fact that photolithography of electronic components concerns etching metal duplicates, rather than etching stone to produce a "master" as in conventional lithographic printing, Lathrop and Nall chose the term "photolithography" over "photoetching" because the former sounded "high tech."<ref name="Lathrop-2013" /> A year after the conference, Lathrop and Nall's patent on photolithography was formally approved on June 9, 1959.<ref>{{Cite book|title=Makers of the Microchip: A Documentary History of Fairchild Semiconductor|last=Lécuyer|first=Christophe|publisher=The MIT Press|year=2010|isbn=978-0262014243}}</ref> Photolithography would later contribute to the development of the first semiconductor ICs as well as the first microchips.<ref name="Lathrop-2013" />