  The switching dynamics of current-biased
Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ intrinsic Josephson junctions (IJJs)
was studied to clarify the effect of d-wave superconductivity and the stack
structure on the switching properties. High quality IJJs were fabricated, and
then the temperature dependence of the switching probability distribution was
measured for the first and second switchings. Although the standard deviation
of the distribution detected for both switchings showed similar saturation
characteristics with decreasing temperature, the temperature at saturation was
about 13 times higher for the second switching than for the first switching.
The properties of the first switching can be explained in terms of a
conventional underdamped JJ, that is, macroscopic quantum tunneling below the
crossover temperature, and thermal activation with quality factor of 70$\pm$20
above the crossover temperature. In contrast, the relatively higher effective
temperature for the second switching evaluated from the switching probability
distribution suggests a dominant thermal activation process under the influence
of the self-heating effect even at sufficiently low temperature.
