Thermal Stability of ALD-HfO₂/GaAs Pretreated with Trimethylaluminium

Abstract

The simultaneous self-cleaning and passivation of an as-received GaAs substrate using trimethylaluminium (TMA) pretreatment before the atomic layer deposition (ALD) of HfO 2 was systematically investigated. The change of the interfacial characteristics was probed as a function of the number of treatment cycles and the post-deposition annealing temperature and related with various electrical properties of the HfO 2 film. The TMA pretreatment removed the Ga-and As-oxides more effectively than the ALD-HfO 2 process, which reduced the amount of frequency dispersion. In addition, compared to the As case, it showed more predominant suppression of both Ga out-diffusion and Ga-O bond formation, which is believed to have delayed the thermal degradation of the capacitance equivalent thickness (CET). The optimal number of TMA treatment exhibited the best thermal stability without increasing the as-deposited CET.

Passivation of Ge surface treated with trimethylaluminum and investigation of electrical properties of HfTiO/Ge gate stacks

“…Moreover, Ge oxide easily grows on Ge surface exposed to air for a very short time, even after chemical pretreatment with HF or HCl [11] .In recent years, it has been demonstrated that the native oxide on Ш-V semiconductors (GaAs, InSb, etc. ), InGaAs and Ge surfaces could be effectively "cleaned" through a ligand exchange mechanism between the atomic layer deposion (ALD) precursor and the interfacial native oxide [12][13][14][15][16][17][18] . For example, Al2O3 precursor -trimethylaluminum (TMA) can effectively minimize Ga and As oxides by the formation of volatile products such as AsCH and As[OCH(CH3)2]3 followed ligand exchange mechanism [12,13] .…”

“…), InGaAs and Ge surfaces could be effectively "cleaned" through a ligand exchange mechanism between the atomic layer deposion (ALD) precursor and the interfacial native oxide [12][13][14][15][16][17][18] . For example, Al2O3 precursor -trimethylaluminum (TMA) can effectively minimize Ga and As oxides by the formation of volatile products such as AsCH and As[OCH(CH3)2]3 followed ligand exchange mechanism [12,13] . And it achieves the effects of removal of thermal unstable oxide on GaAs surface and improvement of interface quality [12,13] .…”

“…For example, Al2O3 precursor -trimethylaluminum (TMA) can effectively minimize Ga and As oxides by the formation of volatile products such as AsCH and As[OCH(CH3)2]3 followed ligand exchange mechanism [12,13] . And it achieves the effects of removal of thermal unstable oxide on GaAs surface and improvement of interface quality [12,13] . Similarly, TMA can effectively remove native oxide on Ge surface and enhance interface and electrical properties of Ge-based MOS device [16][17][18] .…”

Comparison of the reactivity of alkyl and alkyl amine precursors with native oxide GaAs(100) and InAs(100) surfaces

“…However, from a basic research perspective there are several conflicting results that have created confusion as to the exact nature of the so-called "interface clean-up" reaction. For example, it was proven that native oxide removal through reactions with TMA was a first-contact effect [5,[16][17][18][19][20][21]. But for ALD processes that used alkylamine precursors the well-documented continuous removal of the III-V surface native oxides even after the surface had been covered with 2 nm or more of the growing film hinted at the existence of a more complex reaction mechanism [4,9,[22][23][24].…”

“…For that purpose we studied the interaction of the two types of precursors, alkyl-and alkyl amine, through an extended process temperature range from 200-300°C on native oxide-covered InAs(100) and GaAs(100). Most studies for the ALD of Al 2 O 3 on III-V compounds have been carried out at process temperatures of 300°C or above [5,[16][17][18][19][20][21]. The effectiveness of TMA at lower temperatures has been examined in only a few studies and, for the most part, these studies used substrates that were etched prior to deposition leaving only traces of the native oxides [19,29,30].…”