Intrinsic stresses which arise during the chemical vapor deposition (CVD) of diamond were controlled by multistep processing. Film stresses (thermal and intrinsic) were measured with the bending plate method. The thermal stresses are compressive and arise due to the mismatch in thermal expansion coefficient between the film and substrate. The dominant intrinsic stresses are tensile and evolve during the deposition process. These stresses increase with deposition time. An intermediate step consisting of annealing the film when the diamond crystallites are only partially coalesced reduces the intrinsic stress by more than 50%. Annealing at longer growth times (i.e., after complete coalescence) does not produce large reductions in intrinsic stress. Our results are consistent with stress generation due to the formation of nonequilibrium grain boundary structures. The intermediate annealing step does not produce a large, direct stress reduction; instead, it alters the film microstructure in some subtle way which reduces stress generation during subsequent growth.

The role of intrinsic stresses in diamond films is examined. The films were deposited on (100) Si substrates by microwave plasma-enhanced chemical vapor deposition. The total internal stresses (thermal and intrinsic) were measured at room temperature with the bending plate method. The thermal stresses are compressive and arise due to the mismatch in thermal expansion coefficient of film and substrate. The intinsic stresses were tensile and evolved during the deposition process. These stresses increased with increasing deposition time. A 12 hour intermediate annealing treatment was found to reduce the tensile stresses considerably. The annealing treatment is most effective when the diamond crystallites are undergoing impingement and coalescence. This is consistent with the theory that the maximum tensile stresses are associated with grain boundary energetics.