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采用有限元分析方法模拟铜互连系统中的热应力分布,模拟了在铜互连不同位置处应力诱生空洞前后应力的分布及其变化,研究互连中应力诱生空洞可能的生长位置及其几何形状。结果表明,互连中的应力分布呈明显的各向异性,水平方向上的应力梯度显著大于垂直方向。互连系统中的张应力在M1顶端通孔两侧出现极大值。在M1顶端通孔两侧的空洞生长可以有效释放互连张应力,且随着空洞尺寸的增大张应力不断减小甚至发生向压应力的转变。从能量角度分析,应力诱生空洞释放的应变能提供了空洞在生长过程中克服能量势垒所需要的能量。模拟结果表明,椭圆空洞在生长过程释放更多的弹性能,空洞在生长过程中逐渐由圆形向椭圆转变,更有利于空洞的生长。
The thermal stress distribution in copper interconnection system was simulated by finite element analysis (FEM), the distribution and change of stress before and after stress induced voids at different locations of copper interconnection were simulated, and the possible growth location of stress induced voids in interconnection and Its geometry. The results show that the stress distribution in the interconnection is obviously anisotropic, and the stress gradient in the horizontal direction is significantly larger than that in the vertical direction. The tensile stress in the interconnection system appears to be maximum on either side of the M1 top via. Cavity growth on both sides of the through hole at the top of M1 can effectively release the interconnected tensile stress, and the stress decreases or even changes to the compressive stress as the cavity size increases. From an energy perspective, the strain energy released by stress-induced cavities provides the energy required to overcome the energy barrier in the growth of voids. The simulation results show that the elliptical cavity can release more elastic energy during growth, and the cavity gradually changes from circular to elliptical during growth, which is more conducive to the growth of hollow.