Fabrication of high-performance copper circuits using laser-induced forward transfer with large receiving gaps based on beam modulation technology

Laser-induced forward transfer (LIFT) technology has been widely used to print 2D/3D structural patterns in the micron level of metals due to its contactless and maskless advantages. Still, it cannot meet the practical needs of the industry due to its drawbacks, such as low efficiency and a small receiving gap. This study proposes a new LIFT by modulating a Gaussian beam into an Arc beam using a liquid crystal on silicon spatial light modulator (LCOS-SLM) to achieve stable preparation of high-performance Cu circuits at large receiving gaps. First, the laser-induced monomer transfer modes of Gaussian beams and arc beams are studied. Then the effects of laser energy density, scanning velocity, and reception gap on the microcircuits prepared by Gaussian beam laser-induced forward transfer (GB-LIFT) and Arc beam laser-induced forward transfer (AB-LIFT) are studied systematically, and suitable process parameters are found. The transfer process of action of AB-LIFT is revealed. Under the optimized process parameters, the flight distance of AB-LIFT is up to 120 μm, which is about twice that of GB-LIFT, when the laser energy density is 1.94 μJ, and the scanning velocity is 3 mm/s. And the height of the microcircuit can be controlled by the number of depositions. It is demonstrated that the AB-LIFT can achieve stable transfer with large receiving gaps and efficiently prepare continuous Cu circuits with high bonding strength and low resistance. The minimum resistivity (7.46 μΩ∙cm) obtained by selecting optimized process parameters is about 4 times that of Cu bulk (1.76 μΩ∙cm). The application of the AB-LIFT method based on the beam modulation technique in microcircuit defect repair is verified.