Chemistry Seminar - Chemical Strategies for Monolayer Doping

Chemical Strategies for Monolayer DopingXavier ThompsonChemistry MS CandidateSchool of Chemistry and Materials Science, RITAdvisor: Dr. Scott WilliamsAbstract:Ultra-shallow field effect transistor junctions fabricated outside of a cleanroom environment by using chemical monolayer doping will be presented. The technique could provide several advantages over conventional doping techniques such as ion implantation and two-step diffusion. Self-assembled monolayers of dopant molecules form by a hydrosilylation reaction which is hindered by the presence of oxygen. A custom glass chamber was designed to fit 6-inch diameter wafers with an air-tight seal, and with ports for the flow of argon, a reflux column, and a thermometer. A wafer can be submerged, in this chamber, under a solution of active dopant molecule in a high boiling point solvent, and heated for 2 hours. During this time, the monolayer forms and the chamber keeps the solution in and oxygen out. The improved oxygen purging capabilities of the chamber, over previous equipment, yields higher dopant concentrations in the silicon and greater control over the temperature of the reaction. Following functionalization, the samples were capped with 50 nm of SiO_2 deposited by plasma enhanced chemical vapor deposition, then annealed to enable the diffusion and electrical activation of dopant atoms into the substrate. Characterizations included electrical testing of sheet resistance and depth profiling of dopant atoms using Secondary Ion Mass Spectroscopy (SIMS). This new chamber provides a good environment for testing novel dopant designs. Two new boron containing molecules were designed and synthesized, and one previously known phosphorus dopant was synthesized in house to yield lower sheet resistance results than the commercial counterpart. Combining the advantages gained from the chamber and novel dopant molecules, this work represents progress in the development of the monolayer doping technique and thus an advancement in the fabrication of next generation devices.Speaker Bio:Xavier Thompson received his BS in Economics from the Rochester Institute of Technology in May of 2018. He joined RIT’s Master’s program in Chemistry in Spring of 2019. His research interests include synthetic chemistry and photovoltaics. His hobbies include cooking, singing too loudly, and longboarding.