Grain Growth and Stress Relief in Thin Films

The effect of grain growth on stresses in films is discussed. Grain growth generally leads to stress relaxation when the film is under a compressive stress. When the initial grain size is below a critical value, grain growth can occur by normal boundary migration and generates a tensile stress in the plane of the film. Grain growth proceeds until a particular grain size is reached, at which the sum of the strain energy and surface energy is minimized. Further grain growth can occur if plastic flow relieves some of the strain energy. When the initial grain size is above the critical size, there is no minimum in the energy vs grain size relationship, and grain growth to infinite size can occur by normal boundary migration. In the presence of impurities, apparently anomalous intrinsic stresses in films may be produced.