Residual stresses are a major factor in the reliable operation of multi-layer thin film structures. These stresses form due to various causes. Defect incorporation during deposition, rccrystallization, second-phase precipitation, coefficient of thermal expansion (CTE) mismatch, etc., can all cause the formation of residual stress fields. These stress fields can also change during the operation of the device, depending on the temperature excursions seen during the operation. Again, the stress change may be due to any of the factors listed above, brought about by the temperature excursions.
In this paper we examine the formation and relaxation of residual stresses in “blanket” Al, Cu and Ni films subjected to temperature cycling. Comparison of the stress dependency on temperature to the total retained strain (measured by a micro-grid technique) is then used to determine the location of plastic flow within the film.