(A) study on the characteristics of TaN films deposited by ALD using hydrogen plasma

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 organic precursors are usually sparse and have amorphous structures which induce the poor qualities of thin films. In this work, the characteristics of TaN films deposited by conventional atomic layer deposition (ALD) and its application using hydrogen plasma have been examined. TaN films were deposited on $SiO_2$ at 260°C and the pressure of 1torr. In the case of conventional ALD, TaN films were deposited by alternate supply of TBTDET and $NH_3$ as reactant gases. The deposition thickness per cycle of the films saturated at around 1.1Å/cycle with sufficient pulse times of reactant gases. The films contained rather high amount of carbon impurity of above 10 at. % and their resistivity was very high. Accordingly, the new ALD technique by using plasma was developed. TaN films were deposited by plasma enhanced atomic layer deposition using hydrogen radicals as a reducing agent instead of $NH_3$. The deposition thickness per cycle of the films saturated at around 0.78Å/cycle with sufficient pulse times of reactant gases. The TaN films have an excellent resistivity with about 400μΩㆍcm, the lower resistivity than ever reported that in TaN CVD. In addition, they show no aging effect after a long period of exposure to air and perfect film step coverage on holes with an aspect ratio of 10:1. As the plasma pulse time increases, the crystallinity of the films increases, the carbon contents decreases. However, carbon content in the films increases from 16% to 35% with the increases of the plasma power from 50W to 100W. Carbon atoms exist as the constituent of TaC. In order t...