Next-generation advanced packages exhibiting smaller feature sizes, tighter pitches, embedded structures or interposers rely on high precision structuring of thin organic layers beyond the limitations of conventional photolithography. Excimer laser ablation as a dry, single-step process eliminates the need for conventional, wet chemistry based photolithography and applies to most types of organic dielectrics.
Specifically, excimer laser mask imaging delivers unmatched placement accuracy of essential structures such as trenches for redistribution layers and micronsize vias accurately connecting contact pads. The short wavelength of excimer lasers provides excellent depth control when opening an embedded metal contact pad. The high pulse energy and high power of the excimer laser supports high processing rates.
While the short 308 nm wavelength of the excimer laser provides highest precision via direct bond breaking of the polymer material, throughput scaling is achieved via stabilized output power levels extending up and beyond 500 Watts. Sidewall angles of blind vias are controllable by adjusting the applied laser energy density and pulse number. In this work, the structuring capabilities of 193, 248 and 308 nm wavelength excimer lasers in build-up films as to taper angle variations, achievable via diameters, layer-selectivity and ablation rates will be elucidated.