i) IBS has been able to modify a production sputtering machine. A transfer of knowledge from the DPMT laboratory to an SME (IBS) with the scientific support of all the other partners of MULTISTRESS has allowed IBS to be able to produce multilayer coatings.
ii) An in situ - during annealing - stress measurement device has benn set up in MATOP. It allows the characterisation of the curvature of small samples (1cm2) from room temperature to 1000C under vacuum. It has been successfully applied to the study of stress relaxation in Ag/Ni multilayers.
iii) An in situ - during annealing - x-ray diffraction experiment has been set up in LMGP. It is operational to study the structure evolution of various samples up to 800 C under various atmospheres. The use of a curved detector with an angular aperture of 120 C allows rapid acquisition times. It has been successfully applied to the study of microstructure evolution in Ag/Ni multilayers.
iv) An insitu - during growth by sputtering - stress measurement set up has been installed in DPMT. This setup coupled with RHEED enables extensive studies of stress and strain evolution during growth. It has allowed the proper understanding of stress evolution in ultrathin Ni and Ag films.
v) During the MULTISTRESS project the theory for the Glancing Incidence X-ray Analysis (GIXA) technique has been further developed by Philips. The resulting algorithms have resulted in an analysis software which is available as a commercial prototype. This method has been proven helpful for the analysis of several layered materials.
All these experimental developments represent a long term output of this project. The equipment or software which have been set up will indeed in other research projects or will allow new market opportunities.
Objectives and content
A strong industrial need is foreseen for equipment and methods for the determination and the control of internal stress, strain and interfacial structure in metallic materials composed of many superposed layers of some nanometer thickness (metallic multilayers). The very high stress levels that are present in these materials are a major concern for the reliability of the devices composed of such multilayers (hyper-sensitive magnetic sensors, wear resistant coatings, etc.). on the other hand, most properties of multilayers are ruled by the quality of the interfaces of the layers. Therefore robust analytical tools have to be developed in order to study the interfacial structure (roughness, interdiffusion, lattice distortion, etc.) and methods have to be devised to control the quality of the multilayers.
The objective of this project is two-fold:
- To determine to which extent it is possible that stresses and the interfacial structure in multilayers can be tailored to their required values. - To determine whether X-ray reflectivity equipment is suited to determine the material parameters of interest.
This project is of interest for a multitude of industrial areas, the electronic industry, mechanical engineering, etc. It is expected that in the near future the application of metallic multilayers will steadily increase in a wide range of industrial products. Secondly, the project might result in a new application area for new, advanced X-ray analytical equipment.
The research approach will be the following: Test materials will be grown by sputtering, because of the flexibility and industrial potential of this technique. The stresses and strains will be measured at different scales by a combination of techniques (laser scanning, X-ray diffraction). Interface roughness and interdiffusion will be measured by X-ray reflectivity and Transmission Electron Microscopy. Different in-situ annealing experiments (laser scanning, X-ray diffraction, resistivity) will be performed in order to evaluate the thermal stability of the multilayers and the way in which stress relaxation in these structures will occur. The representativity of X-ray diffraction results for the parameters of interest will be determined.
Typical parameters of the multilayers to be studied are: stresses in the GPa range, strains in the 1% range, interface roughness in the range of 0.3 to 3 nanometers with lateral characteristic lengths of 30 nanometers to 3 micrometers and an interdiffusion layer thickness in the range of 0.2 to 5 nanometers.
This project involves five universities and two industrial partners of which one is an SME, all with unique and complementary knowledge. The consortium consists of developers, suppliers and end-users having not only all the knowledge to carry out the technical aspects of the project but also the capabitities to assess the economic importance of the results.
Funding SchemeCSC - Cost-sharing contracts
5656 AA Eindhoven
2628 AL Delft