Comparative study and characterization of atomic layer deposition Al2O3 films as metal-insulator-metal capacitor dielectric for GaAs hetero-junction bipolar transistor technology

Abstract

Atomic layer deposition (ALD) aluminum oxide (Al2O3) films have been deposited using trimethyl aluminum (TMA) and H2O, and using TMA and H2O with O3 as precursors, and were characterized and evaluated as a metal-insulator-metal (MIM) capacitor dielectric in GaAs hetero-junction bipolar transistor (HBT) technology. The results show that the capacitor with 60 nm of ALD Al2O3 capacitor dielectric films deposited using TMA and H2O and deposited using TMA, H2O, and O3 resulted in a capacitance density of 1.36 × 10−15–1.37 × 10−15 F/μm2, and a dielectric constant of 9.2–9.3. The capacitance density of the capacitor using these films increased by 2.3%–3.0%, when the temperature was increased from 25 to 125 °C. No significant change in capacitance density of these ALD films was observed when the applied voltage was varied from −5 to +5 V. However, the 60 nm ALD aluminum oxide film deposited using the TMA, H2O, and O3 has significantly higher breakdown voltage (46 V) compared to the ALD aluminum oxide film deposited using TMA and H2O only (38.4 V). Furthermore, the leakage current density of the ALD Al2O3 from TMA, H2O, and O3 is significantly lower compared to that of ALD Al2O3 from TMA and H2O (5.6 × 10−8 A/cm2 vs 8.9 × 10−6 A/cm2 at 5 MV/cm). As the temperature was increased from 25 to 125 °C, the breakdown voltage of both films decreased, while the leakage current marginally increased. Additionally, as the capacitor area is increased, the leakage current also increased, while no change in breakdown voltage is observed.