Figure 7 Annealing temperature dependences of sheet resistance, carrier
concentration and Hall mobility of the IHfO:H films prepared with 0.8 %
H2 concentration.
As can be seen from Figure 7, the Hall mobility of the IHfO:H films
increases rapidly from the as-deposited 41.48
cm2V-1s-1 to
102.92 cm2V-1s-1with an annealing temperature of 200 °C. However, as the annealing
temperature is keep increasing to 250 °C, the Hall mobility decreases.
The annealing temperature dependence of mobility seems to be consistent
with that of the crystallinity, as shown in Figure 6, which implies the
possible relationship between the rise of the mobility and the reduced
grain boundary scattering.29 However, the carrier
concentration does not increase with the annealing temperature, but
shows an opposite tendency as depicted in Figure 7, although it is
generally believed that crystallization could promote the activation of
dopants.35 The significant decrease of carrier
concentration with annealing temperature, which actually determines the
change of sheet resistance, represents the reduced concentration of
doping impurity. The weakened ionized impurity scattering and the
improved crystallinity together lead to the improvement of the mobility
of the IHfO:H films. The slight decrease of the mobility and the average
grain size at the annealing temperature of 250 °C are probably related
to the escaping of the hydrogen. 34,35