Cu互连应力迁移温度特性研究

提出了一种基于扩散-蠕变机制的空洞生长模型, 结合应力模拟计算和聚焦离子束分析技术研究了Cu互连应力诱生空洞失效现象, 探讨了应力诱生空洞的形成机制并分析了空洞生长速率与温度、应力梯度和扩散路径的关系. 研究结果表明, 在Cu M1互连顶端通孔拐角底部处应力和应力梯度达到极大值并观察到空洞出现. 应力梯度是决定空洞成核位置及空洞生长速率的关键因素. 应力迁移是空位在应力梯度作用下沿主导扩散路径进行的空位积聚与成核现象, 应力梯度的作用与扩散作用随温度变化方向相反, 并存在一个中值温度使得应力诱生空洞速率达到极大值. 关键词： Cu互连 应力迁移 应力诱生空洞 失效

The temperature characteristics of stress-induced voiding in Cu interconnects

A stress induced voiding model based on the Nabarro Herring mechanism has been proposed. The stress induced voiding phenomena in Cu interconnects have been studied by the FIB cross section technique and stress modeling. The driving force for the formation of stress induced voids has been investigated. The relationship between stress induced voiding, temperature, stress gradient and the dominant diffusion path are discussed. The results show that stress and stress gradient reach their peak values at the top surfaces of Cu M1 lines underneath the corner of the vials where voids are observed. Stress gradient shows crucial effect on the failure spot and the voiding rate. Stress migration is basically a diffusion and nucleation process of vacancies through the main diffusion path under the force of the stress gradient. The stress gradient and the diffusion terms vary oppositely with temperature and the maximum voiding rate is reached at a medium temperature.