Simulation And Experimental Study On Residual Stresses In HFCVD Diamond Films

In this paper, the study is carried out on the residual stresses in diamond film prepared by hot filament chemical vapor deposition (HFCVD). The stress of diamond film includes the thermal stress and intrinsic stress. The finite element analysis (FEA) model is set up to invenstigate the distribution and variation of the thermal stress. The intrinsic stress is measured by XRD method and its generating mechanism is discussed in detail. The main contents and results in this paper are as follows:1. The thermal stress variation in diamond film during its cooling process is studied by using of Ansys. The FEA model is built up successfully. It is shown that the simulation results have good consistence with the experimental results.2. Based on the FEA model, the study is carried out on the effect of deposition parameters on the thermal stress. The result shows the film thickness, initial substrate temperature distribution and cooling speed have a great influence on the thermal stress but the film radius has not. All results will provide the basis for estimating and controlling the thermal stress of diamond film.3. Using C++ language, interface software is developed for input of the parameters used in FEA model, so that the parametric simulation of the thermal stress in HFCVD diamond film can be realized.4. The experimental research is carried out on the intrinsic stress in the paper. The diamond films are prepared in HFCVD system at different conditions. The effect of methane concentration, atmospheric pressure, substrate temperature and grid voltage on the intrinsic stress in the diamond film are studied in details by XRD,SEM and Raman. In the range of the deposition parameters used, the total residual stress and the intrinsic stress in diamond are all compressive stress. The increasing of methane concentration results in the increasing of the value of the total residual stress and the intrinsic stress, but the increasing of atmospheric pressure and substrate temperature both result in their decreasing. On the other hand, the increasing of grid voltage results in their increasing first and their decreasing later. The mechanism of the intrinsic stress is also discussed in detail.