(US5855678-A)      A fluidised bed reactor (10) comprises:    (a) first reaction zone (34) containing a fluidised bed of particles comprising a coating source material, and a means for heating it (40);    (b) first gas inlet (20) for introducing a motive stream of reactive gas into the reactor in an upward direction;    (c) substrate zone (34) above the fluidised bed and a means for heating the substrate (44) such that its temperature is less than the bed zone; and    (d) gas outlet (46) located above the bed zone and below the substrate zone and in close proximity to the surface of the substrate to be coated.    For silicon deposition onto a silicon wafer the particles are Si fluidised by a stream of HCl gas but a range of metals and halogen compounds can be used. The reactor enables high rates of deposition and a highly homogenous coating by modifying the boundary layer formed between the gasified reactive gas stream and the substrate. The boundary layer is minimised by the presence of an exhaust outlet placed in close proximity to the centre of the surface of the substrate and / or the presence of a gas inlet capable of injecting a tangential stream of gas which results in a swirling radial flow of reactive gas.    USE -   CVD of polysilicon thin film.    ADVANTAGE -   The deposition rate is increased and the thin film is homogenous.    (EP979316-A1)      A fluidised bed reactor (10) comprises:    (a) first reaction zone (34) containing a fluidised bed of particles comprising a coating source material, and a means for heating it (40);    (b) first gas inlet (20) for introducing a motive stream of reactive gas into the reactor in an upward direction;    (c) substrate zone (34) above the fluidised bed and a means for heating the substrate (44) such that its temperature is less than the bed zone; and    (d) gas outlet (46) located above the bed zone and below the substrate zone and in close proximity to the surface of the substrate to be coated.    For silicon deposition onto a silicon wafer the particles are Si fluidised by a stream of HCl gas but a range of metals and halogen compounds can be used. The reactor enables high rates of deposition and a highly homogenous coating by modifying the boundary layer formed between the gasified reactive gas stream and the substrate. The boundary layer is minimised by the presence of an exhaust outlet placed in close proximity to the centre of the surface of the substrate and / or the presence of a gas inlet capable of injecting a tangential stream of gas which results in a swirling radial flow of reactive gas.    USE -   CVD of polysilicon thin film.    ADVANTAGE -   The deposition rate is increased and the thin film is homogenous.