ALD HfO2, Al2O3, and PECVD Si3N4 as MIM Capacitor Dielectric for GaAs HBT Technology

Characterization was performed on 60 nm +/3 nm films of atomic layer deposition (ALD) hafnium dioxide (HfO2) and aluminum oxide (Al2O3), and plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (Si3N4) as MIM capacitor dielectric for GaAs HBT technology. The capacitance density of MIM capacitor with ALD HfO2 (2.73 fF/m 2 ) and Al2O3 (1.55 fF/m 2 ) is significantly higher than that with PECVD Si3N4 (0.92 fF/m 2 ). However, the breakdown voltage of the ALD HfO2 (34 V) and Al2O3 (41 V) is lower than that of PECVD Si3N4 (73 V). Additionally, the PECVD Si3N4 leakage current density is significantly lower than that of ALD HfO2 and Al2O3. As the temperature was increased from 25 o C to 150 o C, the leakage current of all films increased. The capacitance of ALD Al2O3 and HfO2 films was observed to change slightly, when the applied voltage was varied from -5 V to +5 V. No significant change in capacitance was seen for all three films, when the frequency was increased from 1 kHz to 1 MHz. The extracted quality factor at 1 GHz of the MIM capacitor with ALD HfO2 and Al2O3 is lower than that with PECVD Si3N4 by about 50%. These results show that the three films have different advantages, are suitable for, and can be used as MIM capacitor dielectric for GaAs HBT technology. The capacitor dielectric can be selected based on the specific electrical requirements, application, and operating conditions of the GaAs IC design.