• Coordinateur : Lynda Chehami, HDR
• Duration: 01/03/2022 - 31/08/2025
• Budget : 172 400 euros

Project description: Layer-on-Substrate (LOS) structures are the seat of many degradations related to both manufacturing defects during the growth of thin films (thickness inhomogeneity, lack of adhesion of the layer to the substrate) up to extreme cases such as the deformation of the wafer, and/or the creation of cracks and delaminations. Faced with these problems, in particular, bonding problems, the microelectronics industry is constantly looking for techniques to characterize the bonding quality of wafer assemblies of electronic chips. We propose here, within the framework of the ANR DACLOS project, a non-destructive inspection method based on an original approach called acoustic field correlation to image this type of defects.
Objectives : The originality of the DACLOS project is to study the propagation of high frequency diffuse Rayleigh wave patterns in inhomogeneous LOS and their interaction with possible defects. The physical principle is based on proper processing of random high frequency elastic wave fields.
This ‘’jump” in frequency from (10-30 kHz) to approximately (10-30 MHz) for the DWC technique presents a double challenge: 1) creating an artificial high frequency diffuse noise and, 2) elaborating new mathematical algorithms for 2D LOS NDT&E from Rayleigh waves. Recently, it is shown that the Rayleigh dispersion is still exploitable when the layer thickness is 100 times smaller than the wavelength. Consequently, the proposed method will allow performing 2D LOS NDT&E with sparse measurement sources for LOS thickness smaller than the wavelength of the instrument operation.

• The proposed method will allow performing 2D LOS NDT&E for LOS thickness smaller than the wavelength of the instrument operation;
• Implementing of DWC for LOS evaluation based on SAW-IDTs allows full 2D characterization with low number of IDTs sources.
• Due to the use of contact IDTs, there is no limitation on layer’s material type. For example, this concerns transparent or fragile layers often causing difficulties when using other measurement methods such as “laser-ultrasound”
• Using a laser vibrometer for detecting diffuse waves permits to obtain a high density of information. Therefore, several signal processing based on matrix imaging algorithms can be applied and consequently retrieve significant information about the state of health of the LOS samples.

CONTACT :

Dr. Lynda CHEHAMI
IEMN site de Valenciennes, Groupe TPIA
Université Polytechnique des Hauts de France
F-59313 Valenciennes cedex 9
Tel : +33(0)3 27 51 11 87
Lynda.chehami@uphf.fr