Delamination prediction in stacked back-end structure underneath bond pads

The thermo-mechanical reliability of integrated circuits (ICs) gains importance due to the reducing feature sizes and the application of new materials. This paper focuses on the delamination in the stacked back-end structure underneath bond pads. Current simulation tools predict this failure mode following a linear elastic fracture mechanics approach; whereas an interface damage mechanics (IDM) approach would be more appropriate to our opinion. The basics of IDM by cohesive zone modeling are outlined. The cohesive zone finite element under consideration is a two-dimensional (2D) linear element for small deformations with an exponential traction separation law. A 2D plane strain model represents a simplified microstructure underneath a bond pad. Several finite element (FE) meshes are constructed with gradually decreasing mesh sizes along the interfaces. Furthermore, two cohesive zone parameter sets are considered, one for 'weak' adhesion between the material layers and one for 'strong' adhesion. The simulations with the FE models demonstrate the capability of IDM to simulate the damage evolution, where several interfacial cracks develop simultaneously. The effect of mesh refinement is illustrated. It improves the convergence of the applied nonlinear solution procedure. Furthermore, the correlation between the adhesion strength and the complexity of the equilibrium path is shown. Finally the conclusions are drawn for the current research and recommendations are given for the further development of IDM applied to delamination prediction in IC back-end structures

[1]  P. Camanho,et al.  Mixed-Mode Decohesion Finite Elements for the Simulation of Delamination in Composite Materials , 2002 .

[2]  Satya N. Atluri,et al.  Computational methods in the mechanics of fracture , 1987, International Journal of Fracture.

[3]  O. van der Sluis,et al.  Novel Damage Model for Delamination in Cu/low-k IC Backend Structures , 2005, Proceedings Electronic Components and Technology, 2005. ECTC '05..

[4]  N. Chandra,et al.  Some issues in the application of cohesive zone models for metal–ceramic interfaces , 2002 .

[5]  M. Ortiz,et al.  FINITE-DEFORMATION IRREVERSIBLE COHESIVE ELEMENTS FOR THREE-DIMENSIONAL CRACK-PROPAGATION ANALYSIS , 1999 .

[6]  I. Scheider.  Simulation of cup-cone fracture in round bars using the cohesive zone model , 2001 .

[7]  V. Tomar,et al.  Bounds for element size in a variable stiffness cohesive finite element model , 2004 .

[8]  Mgd Marc Geers,et al.  Enhanced solution control for physically and geometrically non‐linear problems. Part II—comparative performance analysis , 1999 .

[9]  Mgd Marc Geers,et al.  ENHANCED SOLUTION CONTROL FOR PHYSICALLY AND GEOMETRICALLY NON-LINEAR PROBLEMS. PART I|THE SUBPLANE CONTROL APPROACH , 1999 .

[10]  M. Kanninen,et al.  Advanced Fracture Mechanics , 1986 .

[11]  W. Brocks,et al.  Simulation of cup cone fracture using the cohesive model , 2003 .

[12]  O. Allix,et al.  Some aspects of interlaminar degradation in composites , 2000 .

[13]  S. Pozder,et al.  Analysis of flip-chip packaging challenges on copper/low-k interconnects , 2003 .

[14]  W. Wunderlich.  Nonlinear Finite Element Analysis in Structural Mechanics , 1981 .

[15]  Guotao Wang,et al.  Chip-packaging interaction: a critical concern for Cu/low k packaging , 2005, Microelectron. Reliab..

[16]  R. Borst.  Numerical aspects of cohesive-zone models , 2003 .

[17]  L. L. Mercado,et al.  Analysis of flip-chip packaging challenges on copper low-k interconnects , 2003, 53rd Electronic Components and Technology Conference, 2003. Proceedings..

[18]  J. Heerens,et al.  Three-dimensional modeling of ductile crack growth: Cohesive zone parameters and crack tip triaxiality , 2005 .