Reduction of intrinsic stresses during the chemical vapor deposition of diamond

Intrinsic stresses which arise during the chemical vapor deposition (CVD) o f diamond were controlled by multistep processing. Film stresses (thermal a nd intrinsic) were measured with the bending plate method. The thermal stre sses are compressive and arise due to the mismatch in thermal expansion coe fficient between the film and substrate. The dominant intrinsic stresses ar e tensile and evolve during the deposition process. These stresses increase with deposition time. An intermediate step consisting of annealing the fil m when the diamond crystallites are only partially coalesced reduces the in trinsic stress by more than 50%. Annealing at longer growth times (i.e., af ter complete coalescence) does not produce large reductions in intrinsic st ress. Our results are consistent with stress generation due to the formatio n of nonequilibrium grain boundary structures. The intermediate annealing s tep does not produce a large, direct stress reduction; instead, it alters t he film microstructure in some subtle way which reduces stress generation d uring subsequent growth.