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

本研究提出了一种简单易行的控制残余应力的方法。这里，使用与沉积条件无关的衬底振动。在这个过程中，只有衬底在沉积过程中被PZT振动。测试了TiN、钛、铜、铝、硅和碳膜的残余应力变化。此外，还清楚地显示了残余应力与磨损寿命、硬度、弹性系数等力学性能的关系。通过对薄膜中残余应力的观察，探讨了薄膜中残余应力变化的机理。1)在偏压控制下，薄膜的残余应力发生变化。2)残余应力的变化与薄膜厚度和衬底的晶体结构无关。3)当残余应力由压应力变为拉应力时，TiN薄膜的硬度值下降。4)TiN薄膜和Ti薄膜的残余应力降低，磨损寿命提高。5)随着振动幅度的增大，薄膜的晶粒尺寸减小，结合点的相邻晶体间距增大。这是因为晶粒尺寸的减小刺激了由微晶聚结引起的拉应力的发展，而柱状结构中间隙的增大导致薄膜收缩，从而提高了拉应力。6)将该方法应用于具有TiN中间层的CN薄膜。CN/TiN薄膜的残余应力降低，具有较强的结合强度。

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.