Internal Stress and Atomic Transportation in Thin Film and Line Structure

为了研究大规模集成电路（LSI）材料中Al和Cu在高温区的原子迁移特性，采用X射线热应力原位测量和光学、电子学方法对Al和Cu薄膜的表面形貌进行了观察。< 111 >在所有的情况下，无论RF功率，Ar气体压力和溅射时间的沉积状态下的残余应力是拉伸。利用X射线衍射技术对试样在室温至200 ℃、300 ℃和400 ℃的加热和冷却循环下进行了原位热应力测量。当温度升高到100 ℃时，薄膜中的张应力几乎降到零，之后在每个热循环中，应力水平没有明显变化，直到达到最高温度。在冷却阶段，薄膜中的应力转变为拉伸应力，但在初始阶段增加速率较小，在低温区的最后阶段增加速率较大。这是由于晶界扩散、表面扩散和体扩散的能力。另一方面，由于Al或Cu薄膜表面沉积的保护膜对原子输运的限制，AlN或TiN薄膜覆盖的薄膜在热循环过程中的热应力变化较大，SEM和AFM观察表明，在加热阶段和冷却阶段分别形成了小丘和空洞。此外，在加热阶段的表面粗糙度的变化和再结晶的外观观察原位激光显微镜调查。

In order to investigate the property of atomic migration in high temperature region of aluminum and copper for the materials used in LSI technology, in-situ X-ray thermal stress measurement and optical as well as electronic observations of surface morphology of Al and Cu films.Al and Cu films deposited on a glass or a Si substrate by RF sputtering had strong < 111 > preferred orientation. Residual stress in an as-deposited state was tensile in all the case regardless of the RF power, Ar gas pressure and sputtering time. An in-situ thermal stress measurement was made by X-ray diffraction technique on the specimens under the heating and cooling cycles between RT and 200℃, 300℃, and 400℃. The tensile stress in the films almost diminished to zero level by increasing temperature to 100℃ and after that there was no significant change in the stress level up to the maximum temperature in each thermal cycle. In the cooling stage, the stress in the film changed to tensile but the increasing rate was small in the initial stage and became large in the final stage of low temperature range. It is due to the ability of grain boundary diffusion, surface diffusion and body diffusion. On the other hand, the variation of the thermal stress in films covered by thin AlN or TiN film was large during the thermal cycles because of the constraining of the atomic transportation by the protective film deposited on the surface of Al or Cu film.From SEM and AFM observations, it was cleared that hillocks and voids develop in the heating stage and cooling stage, respectively. Furthermore, the change in surface roughness and the appearance of recrystallization were observed in the heating stage by the in-situ laser microscopic investigation.