(A) study on the atomic layer deposition of Ru and $RuO_2$ thin films

Abstract

Ru and $RuO_2$ thin films are one of the most promising candidates and have been taken great interest for an electrode material in dynamic random access memory (DRAM) because of their good electrical conductivity, oxygen diffusion barrier property, and good dry etchability. In this study, atomic layer deposition (ALD) of Ru and $RuO_2$ thin films was investigated for the first time using $Ru(EtCp)_2$ $[Ru(C_{5}H_{4}C_{2}H_{5})_2]$ as a metal precursor and $O_2$ as a reactant gas. The film growth mechanism was also studied in terms of $Ru(EtCp)_2$ precursor adsorption and $O_2$ partial pressure. Ru or $RuO_2$ film was deposited depending on the amount of $Ru(EtCp)_2$ precursor adsorption at given $O_2$ partial pressure. That is, small adsorption of metal precursor resulted in $RuO_2$ film formation. Also, Ru and $RuO_2$ films were deposited depending on $O_2$ partial pressure. In some given metal precursor adsorption, $RuO_2$ was formed when $O_2$ partial pressure was higher than a certain critical value. Therefore, Ru and $RuO_2$ film deposition could be digitally controlled by changing $O_2$ partial pressure, as well as $Ru(EtCp)_2$ precursor adsorption. Ru film having resistivity of about 15 μΩㆍcm was deposited with the saturated deposition rate of 0.15 nm/cycle and digital thickness control. $RuO_2$ film with 70 μΩㆍcm was also deposited by changing process condition. Deposited Ru and $RuO_2$ films had different density of impurities. In Ru film, 2.90 at% Carbon and 0.58 at% Hydrogen were detected. But, Hydrogen impurity of 3.70 at% was only detected in $RuO_2$ film. Density of these impurities was, however, decreased below the detection limit of ERD-TOF after annealing in oxygen ambient. Oxygen diffusion barrier property of deposited films was evaluated by heat treatment in $O_2$ or Ar ambient. Ru thin film was seriously agglomerated by oxidation in $O_2$ ambient. Single $RuO_2$ thin film deposited on Si substrate was also agglomerated when annealing tem...