(A) study on the deposition mechanism and characteristics of $Al_2O_3$ films deposited by atomic layer deposition using TMA and IPA

Abstract

$Al_2O_3$ is considered as the most promising alternative to $SiO_2$ for a gate dielectric materials in future Si-based integrated circuits owing to its high dielectric constant and low leakage current. In this study, amorphous $Al_2O_3$ films on p-Si(100) at 250 ℃ have been successfully grown by atomic layer deposition (ALD) using $Al(CH_3)_3$ [trimethylaluminum: TMA] and $C_3H_8O$ [isopropylalcohol: IPA]. TMA is a conventional Al precursor but IPA isn``t conventional O precursor. Even though $H_2O$ is a conventional oxygen precursor to deposit $Al_2O_3$ using ALD, in this thesis, IPA was used to oxygen precursor. The main reason of IPA selection will be discussed in later. The film growth kinetics were studied using the concept of ALD and also excellent film characteristics were confirmed. The ALD temperature range for $Al_2O_3$ using TMA and IPA was between 230 ℃ ∼ 290 ℃. In order to acquire the best ALD condition for $Al_2O_3$ deposition using TMA and IPA at 250 ℃, $P_{TMA}$=0.01 torr, $P_{IPA}$=0.1 torr, the behaviors of deposition thickness/cycle with TMA pulse time and deposition thickness/cycle with IPA pulse time have been investigated. The set of minimum pulse times to get the fully saturated deposition thickness/cycle was (TMA pulse =2s,IPA pulse = 1s) and also, at the optimal condition, the fully saturated deposition thickness/cycle was around 0.8 Å/cycle, which corresponds to 0.37 ML (monolayer)/cycle. Also, refractive index of $Al_2O_3$ films has 1.61 ∼ 1.62. The refractive index of $Al_2O_3$ films were affected by IPA pulse time but not affected by TMA pulse time. Also, an ideal linear relationship between the number of cycles and the film thickness was confirmed. The compositions of deposited films were investigated by x-ray photoelectron spectroscopy (XPS) and also, the carbon incorporations into the films were analyzed by secondary ion mass spectroscopy (SIMS). The results of these studies shows almost stoichiometric $Al_2O_3$ films...