  In this paper, we are concerned with the boundary controllability of heat
equation with dynamic boundary conditions. More precisely, we prove that the
equation is null controllable at any positive time by means of a boundary
control supported on an arbitrary subboundary. The proof of the main result
combines a new boundary Carleman estimate and some regularity estimates for the
adjoint system, with an explicit dependence with respect to the final time.
This technique allows us to overcome a new difficulty that arises when
absorbing a normal derivative term.
