Laser-Induced-Plasma-Assisted Ablation and Metallization on C-Plane Single Crystal Sapphire (c-Al2O3)

Abstract

Laser-induced-plasma-assisted ablation (LIPAA) is a promising micro-machining method that can fabricate microstructure on hard and transparent double-polished single crystal sapphire (SCS). While ablating, a nanosecond pulse 1064 nm wavelength laser beam travels through the SCS substrate and bombards the copper target lined up behind the substrate, which excites the ablating plasma. When laser fluence rises and is above the machining threshold of copper but below that of SCS, the kinetic energy of the copper plasma generated from the bombardment is mainly determined by the laser fluence, the repetition rate, and the substrate-to-target distance. With a lower repetition rate, SCS becomes metallized and gains conductivity. When micro-machining SCS with a pulsed laser are controlled by properly controlling laser machining parameters, such as laser fluence, repetition rate, and substrate-to-target distance, LIPAA can ablate certain line widths and depths of the microstructure as well as the resistance of SCS. On the contrary, conductivity resistance of metalized sapphire depends on laser parameters and distance in addition to lower repetition rate.

High aspect ratio sapphire micromachining by ultraviolet laser‐induced plasma‐assisted ablation (LIPAA)

“…These ions create electron‐hole pairs on the backside surface, which enhances the absorption of said surface 9,26 . The laser energy can now be absorbed directly by this surface and ablate the substrate surface simultaneously with the target plasma 10 . In order to study the importance of these mechanisms, the evolution of the depth and the quality of LIPAA engraving is studied in relation to the gap distance, fluence, number of pulses, overlap percentage, frequency, and pulse width.…”

“…Lu et al. have achieved 35‐µm wide 20‐µm deep engravings 10 and ultraviolet (UV) LIPAA by Sugioka et al. and Li et al both reach 200‐nm deep features 11,12 .…”

Hybrid laser precision engineering of transparent hard materials: challenges, solutions and applications

“…In this study, electroplating can significantly enhance the conductivity and adhesive strength of the electrode. The conductivity of the metal film generated by LIPAA has been systematically investigated 44,67 . The resistivity is highly dependent on the LIPAA processing parameters, such as scanning speed, target-substrate distance, repetition rate, and laser fluence, which means that the resistivity can be precisely tuned by adjusting the processing parameters.…”

Laser machining of transparent brittle materials: from machining strategies to applications

“…The technology was studied by many researchers [41][42][43] . There are two main processing methods, one is that there is a gap distance between the absorber and the target 44 , and the other is that the absorber is direct contact with the target for processing 45 . Pan and co-workers 46 studied the fabrication of micro-texture channel on glass by laser-induced plasma-assisted ablation.…”