Development of Control Method for Residual Stress in Thin Film by Ultrasonic Substrate Vibration

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In this study, an excellent and simple method for controlling the residual stress is proposed. Here, substrate vibration that is independent of the deposition condition is used. In this process, only substrates are vibrated by PZT during the deposition. The changes of residual stress are tested on TiN,Ti,Cu,Al,Si and C films. Further more, the relationship between residual stress and the mechanical properties such as wear life hardness and elastic coefficient are clearly shown. The mechanism for change of residual stresses was also investigated by the observations of microstructures in films.1)The residual stresses of the crystalline films were changed upon the substrate vibration that was controlled by the bias voltage2)Changing residual stress was independent on film thickness and crystal stricture of the substrate3)The hardness values decreased when the residual stress was changed from compressive to tensile for both Ti and TiN films.4)The wear life was improved when the residual stress was decreased for both Ti and TiN films.5)The grain size decreased and the gap between adjacent crystals at the point of coalescence increased with an increase of vibration amplitude. This is because the decrease in grain size stimulates the development of tensile stress caused by crystallite coalescence while an increasing gap in the columnar structure causes contraction in the film enhancing tensile stress.6)This method was applied to CN films with TiN interlayer. The residual stress of CN/TiN film was decreased and the CN films showed strong adhesive strength.