Laser induced reverse transfer of bulk Cu with a fs-pulsed UV laser for microelectronics applications

Laser Induced Reverse Transfer (LIRT) is a versatile technique as a single-step deposition method allowing the localized transfer of a variety of different metals and polymers on transparent, ultra-thin and stretchable substrates. Also referred to as laser induced backward transfer (LIBT), the process can be manipulated to transfer material from bulk materials to transparent targets, providing a direct method potentially sustainable to generate microelectronic circuitry. In this work, a fs-pulsed UV laser (343 nm) was employed for the first time to transfer electrically conductive copper tracks and layers from bulk Cu in the form of sheet metal onto ultra-clear soda lime glass slides with sub-micrometric thickness. The process development started from the selection of the materials for adequate energy transfer between the beam source and the donor/receiver combination. In the single-track study, the effect of donor/receiver gap was analyzed while tracks ranges with 5 to 233 nm thickness and 7 to 41 μm average width were produced. Based on the results, multi-track layer deposition was assessed by varying the overlap between the tracks. Functional demonstrator cases were produced. The work confirms the suitability of LIRT as a direct approach to create microelectric circuitry by using readily available and sustainable bulk Cu material.