Paper EM-TuA9
The Effect of “Self-Cleaning” ALD Growth on the Electrical Properties of Metal/ High- κ /GaAs and Metal/high-κ/Ge Metal/ MOS Capacitors

Tuesday, November 10, 2009, 4:40 pm, Room B1

The ideas of using high-κ dielectrics as gate oxide and high mobility semiconductor as channel material are promising means of prolonging the scaling of CMOS technology to post Silicon era. However, it has been extremely challenging to produce a high quality oxide/channel interface that yields sufficient device performance for future CMOS. The unwanted chemical species such as residue native oxide, surface carbon, and hydro-carbon can result in defect states at the interface or inside dielectrics. These states can enhance carrier scattering and degrade device threshold voltage. Several recent studies, including ours, showed that, above certain temperature, volatile metal-organic precursors such as TMA can chemically react with the native oxides on the GaAs or InGaAs surface, result in effective removal of native oxide species, and chemically clean interface. This effective is known as the “self-cleaning” ALD growth. Previous studies are largely based on in situ XPS and MEIS measurements on ALD grown samples at various stages during the first few cycles. In this work, we will report on the effect of “self-cleaning” ALD growth and post ALD forming gas annealing on the electrical properties of metal/Al₂O₃/GaAs MOS capacitors. We found the combination of the two treatments can significantly enhance the device C-V characteristics. Our preliminary results showed that frequency dispersion of ~2% per decade in the accumulation capacitance and interface state density (D_it) of ~5x10¹² eV^-1 can be achieved. We also correlated the electrical result with XPS and MEIS studies of the ALD grown Al₂O₃ films and as well as electronic structure at Al₂O₃/GaAs interface. We will also report on the “self-cleaning” growth study of high-κ (Al₂O₃ and HfO₂) on Ge substrate and corresponding electrical result on MOS-CAPs.