Effect of Process Temperature of Al₂O₃ Atomic Layer Deposition Using Accurate Process Gasses Supply System

Abstract

Al2O3 is one of the most expectancy high-k materials for high density on-chip metal-insulator-metal (MIM) capacitors as well as gate insulator for composed semiconductor power devices. In this paper, using the developed atomic layer deposition (ALD) process equipment with multiple oxidation methods and accurate process gas supply system adapted to high temperature usage, the impact of the process temperature on the electrical characteristics of Al2O3 films was investigated. It was found that the substrate material must not be oxidized at the trimethylaluminum (TMA) - oxidation step of ALD. An excessive high temperature may cause decomposition of TMA, so the process temperature should be controlled sufficiently low in order to obtain one layer TMA adsorbing on the wafer. However, this tends to cause lowering oxidation ability, so it is necessary to remove carbon in the Al2O3 films after the ALD. Post ALD process, such as post deposition anneal (PDA) is required.

Oxidizing Species Dependence of the Interface Reaction during Atomic-Layer-Deposition Process and Post-Deposition-Anneal

“…To define MIM area, SiO 2 films were deposited by atmospheric pressure chemical vapor deposition with SiH 4 and O 2 mixed gases at 400°C and the wet etching with the buffered HF was carried out. In both case, after the native oxide on active regions was removed by diluted HF (0.5%), Al 2 O 3 films were deposited by ALD (12,13). Here, ALD was carried out as follows.…”

“…In the case of the radical oxidation in ALD, it is suggested by XPS evaluation that the oxidizing reaction is occurred at the Al 2 O 3 /Si interface during ALD and Al x Si y O z layer is formed at the interface (12). In the former study, H 2 O oxidation at stage temperature of 75 °C was shown to be effective because oxidizing Si does not occur (12). However the oxidation ability of H 2 O is relatively low at such low temperature.…”

“…However the oxidation ability of H 2 O is relatively low at such low temperature. Therefore, it is required to introduce the post-deposition-annealing (PDA) to improve Al 2 O 3 film quality without oxidizing the interface (12,13).…”

Low Leakage Current Al2O3 Metal-Insulator-Metal Capacitors Formed By Atomic Layer Deposition at Optimized Process Temperature and O2 Post Deposition Annealing

“…However, the temperature of ALD is one of the important parameters in relation to the chemical reaction and the dissolution of supply gasses, such as trimethylaluminum (TMA) for Al 2 O 3 . A recent study reported that an excessive high temperature may cause the spontaneous decomposition of TMA and the substrate material must not be oxidized during the oxidation process [7]. In the former study, H 2 O oxidation at stage temperature of 75 °C was shown to be effective [7].…”

“…A recent study reported that an excessive high temperature may cause the spontaneous decomposition of TMA and the substrate material must not be oxidized during the oxidation process [7]. In the former study, H 2 O oxidation at stage temperature of 75 °C was shown to be effective [7]. However, the oxidation ability of H 2 O becomes low at such low temperature.…”