| dc.description | Materials with higher dielectric constant than SiO2 (~ .4.0), called as high-k
materials, are of great demand for CMOS transistors and DRAM capacitors.
Aluminum oxide (Al2O3) has many interesting properties, such as high dielectric
constant (~9.7), high band gap (8.9 eV) and band offset (conduction band ~
2.8eV, valence ~ 3.2 eV), high thermal and chemical stability, high dielectric
strength (15 MV/cm), high radiation resistance, stable interface with Si, low
bulk defect density, high crystallization temperature (~ 1200 C) and could be
a potential candidate to replace SiO2 as a gate dielectric. Extensive work has
been done on high-k metal oxides to reduce the leakage current and improve the
gate capacitance. However, the lack of understanding of nucleation and growth
mechanism of the ultra-thin films of Al2O3 on different surfaces is one the main
bottle neck in achieving the low leakage. Atomic layer deposition (ALD) is one
the state-of-the-art thin film growth technique know for layer-by-layer atomic
growth. It is believe that the growth thin films by ALD will able meet the low
leakage current requirement of micro- and nano-electronic devices.
In the present study, in order to understand the growth mechanism (nucleation
process and growth modes), structural, microsctructural, electrical, and
dielectric properties of Al2O3 thin films by ALD, one set of thin films was grown
with different pulse cycles on Si(111) substrates and another set of thin films
of 100 nm thick was grown on different orientation of Si substrates, such as
Si(100), Si(110), and Si (111). Structural, microstructural, electrical, and dielectric
measurements were carried out using X-ray diffraction, X-ray photoelectron
spectroscopy (XPS) atomic force microscopy (AFM), current-voltage characterization
and dielectric measurements.X-ray diffraction studies showed the amorphous nature of thin films. AFM
and XPS analysis revealed that the films grown with 1 and 2 pulsing cycles
showed discrete nucleation and island-like growth, which is contrary to common
perception that the pulsing one cycle will result the growth of one atomic
layer. The current-voltage characteristics showed rectifying like behavior. The
dielectric measurements that the films have low dielectric loss up to 1 MHz. | |
