  Energy exchanges due to chemical reactions between a silicon surface and a
SF6 plasma were directly measured using a heat flux microsensor (HFM). The
energy flux evolution was compared with those obtained when only few reactions
occur at the surface to show the part of chemical reactions. At 800 W, the
measured energy flux due to chemical reactions is estimated at about 7
W.cm\^{-2} against 0.4 W.cm\^{-2} for ion bombardment and other contributions.
Time evolution of the HFM signal is also studied. The molar enthalpy of the
reaction giving SiF4 molecules was evaluated and is consistent with values
given in literature.
