Low-Profile Interconnects via Laser-Induced Forward Transfer

Abstract

Laser-induced backside wet etching (LIBWE) is a method for the precise etching and structuring of SiO2. In this study, LIBWE is performed by using ultrashort laser pulses with a pulse duration of τ = 500 fs and a wavelength of λ = 515 nm. Saturated aqueous KMnO4 solution is the absorbing liquid for the LIBWE process. The observed etching rate is approximately 10-3 nm/pulse, which is substantially lower than that in previous reports; it increases with increasing laser fluence. The initial etching rate decreases with higher pulse numbers until it approaches a stable value. After the LIBWE, the generated etching pits are partially covered by MnOx layers with thicknesses of tens of nanometers. However, at the etched SiO2 surface, two different laser-induced periodic surface structures (LIPSS) are found. In the center of the etching pits, LIPSS with a period of λHSFL ≈ (52 ± 2) nm are observed, whereas in the outer areas, LIPSS with a period of λLSFL ≈ (390 ± 20) nm are found. The etching mechanism for the LIBWE of SiO2 with aqueous KMnO4 solution is proposed to comprise laser-based heating, decomposition of KMnO4, and chemical etching of the SiO2 surface by the produced KOH.

Numerical modeling to predict threshold fluence for material ejection in Laser-Induced forward transfer of metals

“…Finally, the propelled material gets deposited on the receiver. It entails the competence to deposit an expansive range of materials, single-step printing of multi-layers, development of micro-tracks [1], microscale wires [2], and high aspect-ratio structures [3] to find significant applications in microelectronics [4,5] and bioprinting [6,7]. For high-quality printing, it is crucial to understand the ejection mechanisms and determine the corresponding laser parameters.…”