Round and pleated blisters: interface delamination in thin film deposition

Electron beam deposition is widely used in microelectronics manufacturing due to its ability to fabricate high-purity thin films at elevated rates. However, the formation of blisters during this process – resulting from delamination between the film and substrate – can compromise film integrity and adversely affect device performance. This study investigates the mechanisms behind blister formation during the deposition of gold/titanium (Au/Ti) films on SiO2/Si substrates with a polymethyl methacrylate (PMMA) layer, a common configuration in electronics. Two distinct types of blisters are identified: round blisters and pleated blisters. Elemental analysis and in situ heating experiments revealed that round blisters originate from delamination at the Au-Ti-PMMA/SiO₂ interface, while pleated blisters result from delamination between the Au-Ti film and the PMMA layer. We provide a mechanics model that can quantify the energy required to delaminate the film-substrate interface and the strain within the blister regions. The results offer valuable perspectives on both the fabrication of thin films and the potential application of strain engineering, where controlled blistering may enhance the functional performance of thin films for use in advanced microelectronics.