John Wyllie Coburn passed away peacefully in his home on 28 November 2018 in San Jose, California. A superb experimentalist, he designed and ran insightful, elegant, and groundbreaking studies that led to an understanding of plasma and ion-beam materials processing. Those developments have been crucial to the progress in nanoscience and nanotechnology that have transformed our lives in so many ways.
John was born on 9 November 1933 in Vancouver, British Columbia, and proudly maintained his Canadian citizenship throughout his life. He went to the University of British Columbia, from which he received a bachelor’s of applied science in engineering physics in 1956 and his master’s degree in theoretical physics two years later. At the University of Minnesota, under the guidance of William Peria, John earned his PhD in electrical engineering with a thesis on electron-stimulated desorption. During a postdoctoral year at Simon Fraser University, he studied Faraday rotation in europium-doped calcium fluoride.
In 1968 John joined the IBM Research Center in San Jose, where he worked for the next 25 years in close collaboration with Harold Winters and me. The order of the day was to gain better insight into key processes in the growth of sputtered elemental and compound thin films in low-density plasmas operated in different frequency and mean-free-path regimes. John’s first invaluable contribution was in plasma diagnostics, which for thin-film growth was primitive at the time. John built an electrostatic-extraction and mass-spectrometry facility capable of measuring neutral and ionic species and their kinetic-energy distribution at the surface of a thin film growing on a room-temperature substrate in a relatively low mean-free-path plasma environment.
John’s studies gave some of the first realistic insights of species that could participate in the nucleation, growth, and ultimate composition and structure of the sputtered films. Superimposing spatially defined diagnostic optical spectroscopies led to further understanding of the role of reactive, long-lived free radicals that arrived at the substrate. In the absence of meaningful data on many collisional processes in the plasma, those combined approaches proved to be invaluable in the context not only of elemental and compound inorganic thin-film growth but also of plasma etching and polymerization in halocarbon plasmas.
Undoubtedly, John’s most influential technical contribution was the seminal ultrahigh-vacuum ion-beam experiments he conducted with Winters. In 1979 they demonstrated quantitatively the unequivocal role kinetically energetic inert-gas ions play in dramatically enhancing the chemistry of fluorine atoms that interact with silicon surfaces compared with silicon oxide, silicon nitride, and silicon carbide surfaces. That phenomenon, loosely called reactive-ion etching, and advances in high-resolution lithography remain the backbone of nanoscale materials processing of multilayer thin-film assemblies used in high-density magnetic information storage systems and semiconductor microcircuitry. His work on halocarbon plasma polymerization greatly clarified the role of dielectric plasma-polymerized films in selective, directional etching, which is critical in obtaining high-resolution etching features.
After retiring from IBM in 1993, John spent a year as a Senior Distinguished US von Humboldt Scientist at the Fraunhofer Institute in Freiburg, Germany, and studied dry etching of III–V heterojunctions. Subsequently, he worked part-time as a senior research associate with David Graves’s group at the University of California, Berkeley. He continued to focus on plasma etching and reactive-ion etching mechanisms, with an emphasis on quantitatively measuring a more comprehensive set of discharge parameters simultaneously. That included, for example, determining the number density of all key species in the plasma, which led to a more realistic description of chemical reaction mechanisms.
John’s collaborative work with Graves’s group also led to a greater understanding of key surface processes encountered in many plasma-assisted etching environments—for example, the role of surface-catalyzed recombination of chemically active atoms or radicals to form relatively stable molecules on different surfaces.
John never seemed discouraged by the complexity of plasma systems; with rigorous, relatively straightforward approaches, he always managed to identify and experimentally clarify key dimensions of the problems at hand. Another dimension in which John excelled was his dedication to and effectiveness in relating advances in plasma and associated concepts in surface and thin-film science to broad audiences in the technology world.
All John’s areas of study are within the mission of AVS, originally the American Vacuum Society. John’s deep involvement with AVS began when he joined as a graduate student. Over the years he held almost every office, including president in 1988. The work of John and his lifelong colleague Winters was recognized by AVS with the 1993 John A. Thornton Memorial Award and with the 1994 creation of the John Coburn and Harold Winters Student Award in Plasma Science and Technology.
John is remembered by family, friends, and colleagues as a warm and caring person to everyone around him. His wry sense of humor enhanced our lives. I am proud to have been his friend and colleague throughout his career. He is greatly missed.
