Physico-chemical mechanisms of adhesion and debonding at the various surfaces and interfaces of semiconductor devices, integrated circuits and microelectromechanical systems are systematically examined, starting from chip manufacturing and traversing the process stages to the ultimate finished product. Sources of intrinsic and thermal stresses in these devices are pointed out. Thin film ohmic contacts to the devices call for careful attention. The role of an adhesion layer in multilayer metallization schemes is highlighted. In packaged devices, sites facing potential risks of delamination are indicated. As MEMS devices incorporate moving parts, there are additional issues due to adhesion of suspended structures to surfaces in the vicinity, both during chip fabrication and their subsequent operation. Proper surface treatments for preventing adhesion together with design considerations for overcoming stiction pave the way to reliable functioning of these devices. Adhesion–delamination issues in microelectronics and MEMS continue to pose significant challenges to both design and process engineers. This paper is an attempt to survey the adhesion characteristics of materials, their compatibilities and limitations and look at future research trends. In addition, it addresses some of the techniques for improved or reduced adhesion, as demanded by the situation. The paper encompasses fundamental aspects to contemporary applications.

https://iopscience.iop.org/article/10.1088/0022-3727/44/3/034004/pdf

Adhesion–delamination phenomena at the surfaces and interfaces in microelectronics and MEMS structures and packaged devices

Overview of wire bonding using copper wire or insulated wire

http://www.mate.tue.nl/mate/pdfs/7125.pdf

Cohesive zone modeling for structural integrity analysis of IC interconnects

Peridynamics is a theory of continuum mechanics employing a nonlocal model that can simulate fractures and discontinuities (Askari et al. J Phys 125:012---078, 2008; Silling J Mech Phys Solids 48(1):175---209, 2000). It reformulates continuum mechanics in forms of integral equations rather than partial differential equations to calculate the force on a material point. A connection between bond forces and the stress in the classical (local) theory is established for the calculation of peridynamic stress, which is calculated by summing up bond forces passing through or ending at the cross section of a node. The peridynamic stress and the constitutive law in elasticity are used for the derivation of one- and three-dimensional numerical micromoduli. For three-dimensional discretized peridynamics, the numerical micromodulus is larger than the analytical micromodulus, and converges to the analytical value as the horizon to grid spacing ratio increases. A comparison of material responses in a three-dimensional discretized peridynamic model using numerical and analytical micromoduli, respectively, is performed for different horizons. As the horizon increases, the boundary effect is more conspicuous, and the errors increase in the back-calculated Young's modulus and strains. For the simulation of materials of Poisson's ratios other than 1/4, a pairwise compensation scheme for discretized peridynamics is proposed. Compared with classical (local) elasticity solutions, the computational results by applying the proposed scheme show good agreement in the strain, the resultant Young's modulus and Poisson's ratio.

Discretized peridynamics for linear elastic solids

Facing the challenge of designing for Cu/low-k reliability

Analysis of Cu/low-k bond pad delamination by using a novel failure index

For the development of state-of-the-art Cu/low-k CMOS technologies, the integration and introduction of new low-k materials are one of the major bottlenecks due to the bad thermal and mechanical integrity of these materials and the inherited weak interfacial adhesion. Especially the forces resulting from packaging related processes such as dicing, wire bonding, bumping and molding are critical and can easily result in cracking, delamination and chipping of the IC back-end structure if no appropriate measures are taken. This paper presents a methodology for optimizing the thermo-mechanical reliability of bond pads by using a 3D multi-scale finite element approach. An important characteristic of this methodology is the use of a novel energy-based failure index, which allows a fast qualitative comparison of different back-end structures. The usability of the methodology will be illustrated by the comparison of three different bond pad structures.

In this paper, we study the dissection of arterial layers by means of a stiff, planar, penetrating external body (a ‘wedge’), and formulate a novel model of the process using cohesive zone formalism. The work is motivated by a need for better understanding of, and numerical tools for simulating catheter-induced dissection, which is a potentially catastrophic complication whose mechanisms remain little understood. As well as the large deformations and rupture of the tissue, models of such a process must accurately capture the interaction between the tissue and the external body driving the dissection. The latter feature, in particular, distinguishes catheter-induced dissection from, for example, straightforward peeling, which is relatively well-studied. As a step towards such models, we study a scenario involving a geometrically simpler penetrating object (the wedge), which affords more reliable comparison with experimental observations, but which retains the key feature of dissection driven by an external body, as described. Particular emphasis is placed on assessing the reliability of cohesive zone approaches in this context. A series of wedge-driven dissection experiments on porcine aorta were undertaken, from which tissue elastic and fracture parameters were estimated. Finite element models of the experimental configuration, with tissue considered to be a hyperelastic medium, and evolution of tissue rupture modelled with a consistent large-displacement cohesive formulation, were then constructed. Model-predicted and experimentally measured reaction forces on the wedge throughout the dissection process were compared and found to agree well. The performance of the cohesive formulation in modelling externally driven dissection is finally assessed, and the prospects for numerical models of catheter-induced dissection using such approaches is considered.

https://pure.tue.nl/ws/files/58968764/1_s2.0_S1751616117301017_main.pdf

Simulation of arterial dissection by a penetrating external body using cohesive zone modelling

For the development of state-of-the-art Cu/low-k CMOS technologies, the integration and introduction of new low-k materials are one of the major bottlenecks due to the bad thermal and mechanical integrity of these materials and the inherited weak interfacial adhesion. Especially the forces resulting from packaging related processes such as dicing, wire bonding, bumping and molding are critical and can easily result in cracking, delamination and chipping of the IC back-end structure if no appropriate measures are taken. This paper presents a methodology for optimizing the thermomechanical reliability of bond pads by using a 3D multi-level Finite Element approach. An important characteristic of this methodology is the use of a novel energy-based damage model, which allows a fast qualitative comparison of different back-end structures. The usability of the methodology will be illustrated by the comparison of three different bond pad

Novel Damage Model for Delamination in Cu/low-k IC Backend Structures

https://pure.rug.nl/ws/files/128995761/1_s2.0_S0965997820300855_main.pdf

R.M.J. Voncken

Papers

Analysis of Cu/low-k bond pad delamination by using a novel failure index

Analysis of Cu/low-k bond pad delamination by using a novel failure index

Simulation of arterial dissection by a penetrating external body using cohesive zone modelling

Novel Damage Model for Delamination in Cu/low-k IC Backend Structures

FlexMM: A standard method for material descriptions in FEM