Cu互连应力迁移失效有限元分析

Finite Element Analysis of Stress Migration Failure in Cu Interconnects

为研究铜互连系统中各因素对残余应力及应力迁移失效的影响,建立了三维有限元模型,用ANSYS软件分析计算了Cu互连系统中的残余应力分布情况,并对比分析了不同结构、位置及层间介质材料的互连系统中的残余应力及应力梯度。残余应力在金属线中通孔正下方M2互连顶端最小,在通孔内部达到极大值,应力梯度在Cu M2互连顶端通孔拐角底部位置达到极大值。双通孔结构相对单通孔结构应力分布更为均匀,应力梯度更小。结果表明,空洞最易形成位置由应力和应力梯度的大小共同决定,应力极大值随通孔直径和层间介质介电常数的减小而下降,随线宽和重叠区面积的减小而上升。应力梯度随通孔直径、层间介质介电常数和重叠区面积的减小而下降,随线宽减小而上升。

Residual stress distribution in Cu interconnects was analyzed using three-dimension finite element model to study the structure effect of stress migration failure.Different interconnect structures including various via diameter,line width,overlap area,and dielectric material were investigated to analyze structural effects on residual stress and stress gradient.Stress reaches the maximum value inside the via,and reaches the minimum value at the top of M2 underneath the via.Stress gradient achieves the peak value at the top surface of M2 under the corner of the via.Stress gradient was smaller and stress distribution was more uniform in Cu interconnect with double-via structure.The results indicate that voiding position is affected by both the stress and the stress gradient.Residual stress decreases as the via diameter or the dielectric constant of ILD decreasing,and increases as the line width or the overlap area increasing. Stress gradient decreases as the via diameter,the dielectric constant of ILD or the overlap area decreasing,and increase as the line width increasing.