Laminated HZO on InAs: A study of as-deposited ferroelectricity

Sammanfattning: As the limits of transistor feature size scaling is reaching its saturation, new innovations are needed to prevent performance loss. High performance transistors on the III/V semiconductor platform implemented with ferroelectric oxides might in the future satisfy this demand. But the integration of ferroelectrics on materials such as InAs degrades the substrate and other vital components from the high processing temperatures required to achieve orthorhombic crystallinity. In this master thesis, new engineering strategies have been explored to improve the thermal budget of ferroelectric hafnium zirconium oxide (HZO) implemented on InAs. This was realized through integration of atomic layer deposition (ALD) grown oxides in primarily metal-oxide-semiconductor capacitor (MOSCAP) devices using conventional nano-processing techniques. The MOSCAPs were later characterized by standard current-voltage (IV) measurements and the positive-up negative-down (PUND) technique in order to determine the oxide quality, and especially any ferroelectric behaviour. Ferroelectricity was found in both MOSCAP and metal-insulator-metal capacitor (MIMCAP) structures with the highest as-deposited remanent polarization on InAs at 6.6 µC/cm2 and 12.2 µC/cm2 in the MIM stack. The highest remanent polarization among the MOSCAPs was found in a scaled sample at 6.4 nm, which outperformed samples with similar, but thicker oxides. IV-sweeps also revealed suspected ferroelectric tunnel junction (FTJ)-like behaviour in MOS devices. An annealing study was conducted to investigate if enhanced remanent polarization could be achieved by performing RTP on as-deposited samples. This yielded a remanent polarization of 14.5 µC/cm2 after post-process anneal at 450 °C for 300 s. As-deposited ferroelectric HZO offers new paths for integration of the emerging material in temperature sensitive processes, but requires further research to maximize its potential.