通孔微结构对Cu/低-k应力诱生空洞的影响

Effect of Via Microstructure on Cu/low-k Stress-Induced Voiding

基于Cu的随动强化模型,采用有限元分析方法,对不同Cu/低-k通孔微结构中的应力情景进行模拟分析,探讨了因互连通孔和通孔阻挡层形成工艺的波动性,造成通孔高度、通孔沟槽深度和通孔底部阻挡层厚度的变化,以及这一变化对互连通孔和通孔底部互连应力诱生空洞的影响.结果表明:Cu/低-k互连中的通孔微结构效应,是影响互连应力和形成应力诱生空洞的重要因素.大高宽比的通孔结构更易因通孔高度变化而发生应力诱生空洞;通孔沟槽可以有效提高互连应力迁移的可靠性,但需要控制其深度;通孔底部阻挡层厚度对互连应力诱生空洞性能具有矛盾性,需要折中考虑.

Based on the kinematic hardening model of copper,the Cu stress in different Cu/low-k via microstructures are modeled and analyzed via the finite element method to explore the changes of via height,via gouging depth and barrier layer thickness at the via bottom due to the process variation of interconnected via and via barrier layer.Then,the corresponding interconnected via and bottom interconnection stress-induced voiding（SIV） varying with the changes are analyzed.The results indicate that the via microstructure effect of Cu/low-k interconnection is a dominated factor affecting the interconnection stress and the SIV,that the via with high aspect ratio is more susceptible to SIV due to height variation,that the via gouging with suitable depth effectively improves the reliability of stress migration,and that the interconnection SIV performance and the thickness of barrier layer at the via bottom should be compromised because there exists contradiction between the two factors.