The implementation of
HfnormalO2
gate dielectrics in sub-
45nm
devices requires optimization of nanometer-thin
HfnormalO2
layers, deposited, e.g., by atomic layer deposition (ALD). In this work, we optimize ALD conditions such as precursor pulse time and deposition temperature for
HfnormalO2
layers with physical thicknesses below
2nm
. Additionally, we investigate intermediate treatments in the ALD reaction cycle, such as exposure to gas-phase moisture or remote plasma at low temperature and thermal anneals. Such intermediate treatments affect both growth-per-cycle (GPC) and Cl-impurity content of the
HfnormalO2
layers. The analysis of the process modifications allows a better understanding of the reaction mechanisms.
normalH2O
pulse times of
10s
must be applied to achieve saturation in GPC and Cl content. Using saturated
normalH2O
pulses decreases the gate leakage current in the sub-
1nm
equivalent oxide thickness (EOT) range. The GPC is enhanced from
∼1.8Hf∕nm2
for conventional ALD to
4Hf∕nm2
for intermediate plasma treatments at low temperature. Intermediate anneals reduce the Cl content by about two orders of magnitude. Sufficient hydroxylation of the
HfnormalO2
surface is one important factor controlling electrical properties in the sub-
1nm
EOT range. The reduction of the Cl content does not systematically improve the electrical properties.
we report on a highly efficient grating coupler between an optical fiber and a silicon photonic circuit. Using layers of Si/SiO2 as a Bragg mirror and amorphous Si we have measured a coupling efficiency of 69.5%.
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