Characterization of atomic layer deposition HfO₂, Al₂O₃, and plasma-enhanced chemical vapor deposition Si₃N₄ as metal–insulator–metal capacitor dielectric for GaAs HBT technology Available to Purchase

Characterization was performed on the application of atomic layer deposition (ALD) of hafnium dioxide (HfO₂) and aluminum oxide (Al₂O₃), and plasma-enhanced chemical vapor deposition (PECVD) of silicon nitride (Si₃N₄) as metal–insulator–metal (MIM) capacitor dielectric for GaAs heterojunction bipolar transistor (HBT) technology. The results show that the MIM capacitor with 62 nm of ALD HfO₂ resulted in the highest capacitance density (2.67 fF/μm²), followed by capacitor with 59 nm of ALD Al₂O₃ (1.55 fF/μm²) and 63 nm of PECVD Si₃N₄ (0.92 fF/μm²). The breakdown voltage of the PECVD Si₃N₄ was measured to be 73 V, as compared to 34 V for ALD HfO₂ and 41 V for Al₂O₃. The capacitor with Si₃N₄ dielectric was observed to have lower leakage current than both with Al₂O₃ and HfO₂. As the temperature was increased from 25 to 150 °C, the breakdown voltage decreased and the leakage current increased for all three films, while the capacitance increased for the Al₂O₃ and HfO₂. Additionally, the capacitance of the ALD Al₂O₃ and HfO₂ films was observed to change, when the applied voltage was varied from −5 to +5 V, while no significant change was observed on the capacitance of the PECVD Si₃N₄. Furhermore, no significant change in capacitance was seen for these silicon nitride, aluminum oxide, and hafnium dioxide films, as the frequency was increased from 1 kHz to 1 MHz. These results show that the ALD films of Al₂O₃ and HfO₂ have good electrical characteristics and can be used to fabricate high density capacitor. As a result, these ALD Al₂O₃ and HfO₂ films, in addition to PECVD Si₃N₄, are suitable as MIM capacitor dielectric for GaAs HBT technology, depending on the specific electrical characteristics requirements and application of the GaAs devices.