Mechanism of controlled crack formation in thin-film dielectrics

Thin films on substrate may crack due to tensile residual stress taking a mud crack like pattern. The pattern can be controlled by prescribing stress raisers that initiate, and arresters that terminate, cracks at desired locations. Here, we describe the mechanism by which stresses are amplified in plasma-deposited films. Stress raisers in the form of narrow slits or features with sharp corners are reactive ion etched in silicon. Plasma deposition of thin films on these stress raisers causes a nonconformal coverage leading to the formation of narrow voids within the slits. On annealing, the voids amplify the stress and initiate cracks through the thickness of the film.