  Massive scalar fields are considered in the gravitational field produced by a
Schwarzschild black hole with a global monopole in $f(R)$ gravity. The exact
solution of the radial part of the Klein-Gordon equation in this background is
obtained and is given in terms of the general Heun functions. We apply the
properties of the general Heun functions to study the Hawking radiation and the
resonant frequencies of scalar particles.
