Transcript A Study of the Local Electric Property and the Behavior of

Studies on Local Electrical Properties and Annealing
Behaviors of High-κ Er2O3 Films
Haiyue Zhang, Wei Wang, Ting Ji, Zuimin Jiang
State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, PRC.
1. Introduction
Thermally grown silicon dioxide has been used as a gate dielectric in MOSFETs ever since the first working transistor was created in 1960. The progress in microelectronics over the
last decades is based on the high quality of SiO2 and its interface with silicon. However, gate oxide thickness has to be scaled down aggressively towards sub-1nm within the next decade.
The unacceptably high tunneling currents through such thin films present a fundamental scaling limit for SiO2. Therefore, alternative materials with a higher permittivity (high-k) are
currently investigated as replacements for SiO2. Unfortunately, most of these amorphous materials are not sufficiently stable….
One possible solution to these problems is the use of rare earth metal oxide. Recently, it was demonstrated that Erbium Oxide (Er2O3) films have excellent dielectric properties and
possess sufficient processing stability. Additionally, nanometer-scale electrical and topographical Conductive Atomic Force Microscopy (CAFM) measurements were performed directly on
the Er2O3 surface in an attempt to explain the observed macroscopic behavior.
3. Annealing in O2
2.Local Electric Property
FIG.3 Three high
dots were selected
and marked, namely
O1, O2 and O3.
4. Annealing in N2
FIG.7 Three high
dots were selected
and marked, namely
N1, N2 and N3.
FIG.1 Topography and electrical current map of Er2O3
surface measured by CAFM. High dots on topography
map were corresponded with leaky dots on current map.
FIG.2 Three consecutive scans on a certain area with bias of
-3.0V (above) and -6.0V (below) respectively. Neither on
topography or on electrical current map obvious change
were observed.
Oxygen %
As grown
9.7%
16.5%
2.4%
4.2%
Anneal in O2
12.1%
12.3%
12.6%
8.3%
FIG.11 SAES results of Er2O3 as grown (a),
anneal in O2 (b) and anneal in N2 (c)
Anneal in N2
18.2%
19.6%
3.8%
5.2%
FIG.4 Topography and electrical current map as grown(a),
after annealing at the temperature of 400℃ in Oxygen ambient
for 15min(b), 30min(c) and 45min(d) .
FIG.8 Topography and electrical current map after annealing
at the temperature of 400℃ in Nitrogen ambient for 15min(a),
30min(b), 45min(c) and 60min(d).
FIG.5 I-V measurements in the point-contact mode performed on
marked dots.
FIG.9 I-V measurements in the point-contact mode performed on
marked dots.
FIG.6 Diameters, heights and leaky voltage(Tunneling
current reaches 100pA) of the three marked dots.
FIG.10 Diameters, heights and leaky voltage(Tunneling
current reaches 100pA) of the three marked dots.
5.Composition and Structure
In FIG.11, the four
colors were the SAES
result of the surface of the
high dots, the surface of
plane area (green), the
inside of the high dots
(blue) and the inside of the
plane area (black).
The grain boundaries in
polycrystalline materials are known
to be more conductive as there exist
a large number of defects. This
difference could be a possible
interpretation of the various
electrical behaviors for either high
dots or plane area, as shown in
FIG.12
FIG. 12 Cross-sectional HRTEM image of Er2O3
film as grown
6.Conclusion
The local electric property and effect of thermal annealing on the electrical properties of thin Er2O3 film grown on Ge substrate was studied by Conductive Atomic Force Microscopy
(CAFM). It is observed in situ that the leaky dots on current map always relates to morphologically high dots. Such leaky dots perform improvement in their electrical properties, namely as
the reduction of the leaky current and the enhancement of the band gap, after annealed in O2. However, the samples annealed in N2 showed a different behavior. The result from SAES
demonstrated a lack of oxygen in the film especially the leaky point. Such lack could be complemented via a thermal anneal in Oxygen ambient, but not in Nitrogen ambient.