(A) study on the characteristics on TiN films deposited by PEALD using $TiCl_4$

Abstract

Atomic layer deposition (ALD) has received considerable interest in depositing thin films because of its digital controllability for film thickness. Moreover, the films grown by ALD have shown superb step coverage due to the surface limited reaction. However, in spite of its outstanding benefits, due to lower deposition temperatures of ALD, the refractory metal nitrides formed by ALD using metal inorganic precursors are usually sparse and have amorphous structures which induce the poor qualities of thin films, low growth rate. In this work, the characteristics of TiN films deposited by plasma enhanced atomic layer deposition (PEALD). TiN films were deposited on $SiO_2$ at 350℃ and the pressure of 3torr. In the case of PEALD, TiN films were deposited by alternate supply of $TiCl_4$ and $N_2$/$H_2$/Ar plasma as reactant gases instead of $NH_3$, which is used as a reactant gas in typical TiN ALD. The deposition thickness per cycle of the films saturated at 0.46Å/cycle with sufficient pulse times of reactant gases. The films contained low amounts of Cl impurity of below 0.5 at.% and resistivity of the films was 80μΩ-cm. As experiment results, it may be considered $TiCl_4$ is more reactive with $N_2$/$H_2$/Ar plasma than $NH_3$ gas. As the growth temperature decreases, the thickness per cycle of TiN films decreases and Cl content of TiN films increases. It is probably that the reactions between radicals and $TiCl_4$ become activated as the growth temperature increases. As the flow of $H_2$ or Ar gases changes, the thickness per cycle and Cl content of TiN films have various. High quality of TiN films with low Cl content and good electric properties were obtained when the flow of $H_2$ is 20~100sccm. With increase of Ar, the plasma density increased and the dissociation of the precursors was enhanced. As a result, the production of N and H radicals was enhanced and the quality of TiN films was improved.