"An Atomic View of ALD of Dielectrics and Wafer Cleaning of III-V Semiconductors Using STM"
Dr. Andrew Kummel, Univ. of California, San Diego
Scaling of gate oxides on MOSFETs requires nucleating oxide ALD in every unit cell of the semiconductor channel surface without disrupting the semiconductor surface (high mobility) while eliminating dangling bond states (low Dit). The reaction of trimethyl aluminum (TMA) on different reconstructions of InAs(0 0 1) and InGaAs(0 0 1) surfaces were investigated using in-situ STM, in-situ scanning tunneling spec-troscopy (STS), in-situ XPS, and density functional theory (DFT) allowing both wafer cleaning and ALD nucleation to be studied at the atomic level. (1) A method has been developed to hydrogen clean and anneal air exposed IIII-V surfaces to restore them to the order and cleanliness of MBE grown samples. For InGaAs(100), control of the processing conditions allows selection of the As or In/Ga rich reconduction. (2) To scale gate oxides on InGaAs, the ALD oxide growth must by nucleated in each unit cell while avoiding oxidation of the substrate. On the In/Ga-rich InGaAs(100)-4x2 a method has been developed in which TMA spontaneously forms an un-pinned ordered, dense monolayer ideal for EOT oxide scaling and high mobility. On the As-rich InGaAs(100)-4x2, a method has been developed to form an unpinned ordered monolayer over a very large process range. (3)The most common oxidant for gate dielectrics on III-V is H2O. STM experiments have shown that although H2O can displace surface As atoms, the As remain unoxidized so postdeposition annealing can restore the As atoms to their ideal unit cell locations.
Andrew Kummel received his undergraduate degree in Chemical Engi-neering from Yale University and his Ph.D. degree in chemistry from Stanford University. Since 1988 he has been a faculty member at the University of California, San Diego and is currently a Professor in the De-partment of Chemistry and BioChemistry, an affiliated faculty member in NanoEngineering as well as Materials Science and Engineering, and the Assistant Director of the UCSD Moores Cancer Center for Engineering and Physical Sciences. His group is currently performing research in the areas of atomic imaging of wafer cleaning and gate oxide deposition via ALD on advanced semiconductors, density functional theory molecular dynamics (DFTMD) of amorphous oxide/semiconductor interfaces, sur-face chemistry of chemical sensors, and nanoparticle ultrasound imaging agents and automated imaging software for cancer detection and ther-apy. His group has published over 120 journal articles including the first reports of atomic imaging of gate oxide deposition on III-V and Ge semi-conductors with oxide ALD.