Hi,

 I want to know what are some useful softwares in which I can simulate multilayer coatings in terms of thermal (CTE mismatch) stresses, and stresses due to contact type loading. I am looking for softwares that are easy to use by a person like me who has an experimental background, does not have exposure to using Abaqus, but can use softwares like Matlab.

 Thank you in advance for your suggestions.

Regards,

Sudhir

This is a fully funded research project at the University of Waterloo, Canada. The objective is to construct a PECVD and a UV cure chambers for porous dielectric thin film depositions. In addition to building chambers, the candidate will conduct experiments in thin film fracture and small scale deformation. Please email your CV to tttsui@uwaterloo.ca

Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated circuits. However, the porosity and pore structure of these low-k dielectric materials also strongly affects other important material properties besides their dielectric constant.

Many studies on the thin film/substrate structure and its failure mechanism were reported in recent years. The direct experimental results of thin film/substrate structure by scanning electron microscopy (SEM) presents an intriguing problem:there exists a buckling failure mechanism at the lateral edge of metal film under pure bending. The qualitative theoretical analysis has been done on such buckling failure of thin film/substrate structure. The experimental results and theoretical analysis are helpful to understand the extrinsic stresses or deformations that are induced by external physical effects. Accepted by Appl. Phys. Lett.

Elastic stress driven morphological instabilities in thin films have been studied extensively: see Jesson et al, J. Elect. Mat., 26, 9, pp., 1039-1047 (1997), for example, for a nice micrograph of rippling in Si-Ge system and a schematic of the explanation for the rippling. In the case of multilayer films, it is also well known that there could be  post-growth morphological changes, and the layer geometry as well as the number of layers play a crucial role apart from the elastic constants in these changes; see the studies on a Gadolinia-Silica system by Sahoo et al for example -- Appl. Surf. Sci., 252, pp. 1520-1537 (2005). In addition, there is also experimental evidence to show that in the case of multilayer films, there could be strong interactions between different layers of films:  see the studies on Si/Ge multilayers by B Rahmati et al, Appl. Phys. A, 62, pp. 575-579 (1996), for example.  Finally, Sridhar et al (Acta Mater., 45, 7, pp. 2715-2733 (1997)), using a linear stability analysis, showed that in embedded single and multilayer films, there could be two dominant modes of break-up, namely, symmetric and anti-symmetric.

The linear stability analyses of the type used by Sridhar et al, however, are not ideal for a detailed quantitative study of the effect of elastic interactions and volume fraction; further, such analyses are also not meant for the study of long term evolution and final break-up of thin films. In a paper of ours (Chirranjeevi et al--submitted to Acta Materialia), we study elastic stress driven morphological instabilities and consequent break-up of thin film assemblies using a phase field model.

This symposium is part of the Spring 2008 ACS National Meeting and Exposition , to be held at New Orleans, Louisiana, from Sunday, April 6 to Thursday, April 10, 2008.

Organizers: Christopher M. Stafford (NIST), Adam J. Nolte (NIST), Rui Huang (UT Austin)

Sponsors: ACS Division of Polymeric Materials: Science and Engineering (PMSE) and National Science Foundation

Technical Program:

I want to simulate a thin circular film in xy plane. The force is in z direction. I wanna get the deflecton of the film using ANSYS.

The material is linear, but the deformation is geometrically nonlinear. Also, I consider only stretching behavior, which means that

the bending effect is totally neglected.

Which element I should choose?

Thanks in advance!! 

H. Mei, Y. Pang, and R. Huang, International Journal of Fracture 148, 331-342 (2007).

Following a previous effort published in MRS Proceedings, we wrote a journal article of the same title, with more numerical results. While the main conclusions stay the same, a few subtle points are noted in this paper.

First, instead of using the approximate formula by Ye, Suo and Evans (1992), we calculate the energy release rate of interfacial delamination emanating from the channel crack exclusively by the finite element method. We found that the approximate formula is not accurate in several cases.

Position available / thin film and surface mechanics

“Surface du Verre et Interfaces”, a joint CNRS/Saint-Gobain research laboratory in Paris, is hiring a research scientist to strengthen its activities on thin films mechanics. For more information:

http://www.saint-gobain-recherche.com/svi/en/pages/StaffPositions.htm

Hi,

I found in polymer books and some literatures that mechanical properties of polymer improve with the increase of their radius of gyration or end-to-end distance for a fixed molecular weight. I, however, could not find any experimental evidence or any physical explanation. 

It will be a great help to me if anyone refer me some literatures that explains the connection between these two parameters.

 Thanks,

Ashfaq Adnan

Recently, there have been many strain gradient theories that are used for the interpretation of size effect at the micron and submicron length scales. The basic idea of these theories is the introduction of a first, or second (or both) gradients of strain or any internal state variable in the governing equations of classical theories.

Channeling cracks in low-k dielectrics have been observed to be a key reliability issue for advanced interconnects. The constraint effect of surrounding materials including stacked buffer layers has been studied. This paper analyzes the effect of interfacial delamination on the fracture condition of brittle thin films on elastic substrates. It is found that stable delamination along with the growth of a channel crack is possible only for a specific range of elastic mismatch and interface toughness. An effective energy release rate is defined to account for the influence of interfacial delamination on both the driving force and the fracture resistance, which can be significantly higher than the case assuming no delamination.

For the polymer-supported metal thin films that are finding increasing applications, the critical strain to nucleate microcracks ( εc ) should be more meaningful than the generally measured rupture strain. In this paper, we develop both electrical resistance method and microcrack analyzing method to determine εc of polymer-supported Cu films simply but precisely. Significant thickness dependence has been clearly revealed for εc of the polymer-supported Cu films, i.e., thinner is the film lower is εc . This dependence is suggested to cause by the constraint effect of refining grain size on the dislocation movability.

A postdoctoral research associate position is available starting July 2007 in the area of multiscale modeling of the micro/nano- mechanics of thin films and coatings for micro/nano- electromechanical system applications. Qualified candidate must possess a PhD in Mechanical Engineering, Materials Science, or other science/engineering departments with focus on multiscale modeling or thin film mechanics. Computational modeling experience in atomistic simulation techniques and continuum model, experience in scientific programming, and familiarity with UNIX/Linux operating systems are highly desirable. Interested applicants should send application materials by mail or email to:

see the post.