Abstract
Amorphous LaAlO3 films were deposited on hydrogen-terminated silicon substrates by atomic layer deposition (ALD) at 300 oC. The precursors were lanthanum tris(N,N'-diisopropylformamidinate), trimethylaluminum (TMA) and water. Capacitance-voltage measurements made on ALD MoN/LaAlO3/Si stacks showed humps especially at low frequencies. They were effectively removed by O2 treatment at 300 o C without affecting the dielectric constant (κ~15). The O2 treatment can be carried out either after deposition of a LaAlO3 film, or after each ALD cycle. The O2 treatment also lowered the leakage current from 80 mA cm-2 to 1 mA cm-2 for EOT = 1.3 nm. This indicates that oxygen vacancies are the main defects in as-deposited LaAlO3. Oxygen treated LaAlO3 is one of the best candidates for future high-κ dielectric material due to its low leakage, low defect density and abrupt interface with silicon.
Highlights
Since the introduction of metal oxide semiconductor (MOS) field-effect transistors (FETs) as the centerpiece of microelectronic devices, scaling down of transistor size has continued to improve transistor performance
The thickness for gate dielectric layers specified in the ITRS roadmap has become so small that the leakage current density would be too high if SiO2based films were used as gate dielectrics [1]
The C-V curves measured from MOS capacitors with an 8.3 nm thick as-deposited LaAlO3 layer at different frequencies (10 kHz, 100 kHz, 1 MHz) are shown Figure 1 (a)
Summary
Since the introduction of metal oxide semiconductor (MOS) field-effect transistors (FETs) as the centerpiece of microelectronic devices, scaling down of transistor size has continued to improve transistor performance. In this letter, we suggest O2 annealing during or after LaAlO3 deposition to decrease the leakage current and reduce the trap density in the film.
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