Trigger Effect in Thick Precursor Films for Laser Direct Patterning of Copper
摘要
In this study, we investigated the effect of amine concentration in the copper precursor solution on the laser direct patterning (LDP) of copper using a modified 3D printer platform. Furthermore, the “trigger effect” in thick precursor films exceeding the 405 nm laser wavelength was characterized. We found that while an increase in monoethanolamine (MEA) concentration can lead to the formation of Cu(OH)2 complexes, the primary impact of excessive amine is a significant increase in precursor viscosity. This viscosity change results in thicker patterned films, ranging from 65 nm to 123 nm. Despite these variations in thickness, all copper patterns exhibited excellent electrical performance, with resistivities between 5.8 and 6.5 µΩ·cm—approximately 3.6 times that of bulk copper. Using UV-vis spectra and Fresnel equation-based reflectance simulations, we analyze the effect of moisture adsorption on copper pattern formation. Our results show that when the optical-thermal coupling is optimized at specific thicknesses, it facilitates effective energy absorption and triggers thermal decomposition in thick films. These findings show good agreement with the periodic appearing and disappearing of copper patterns observed as air exposure time varies.