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

Abstract

AbstractThe ultraviolet laser‐induced plasma‐assisted ablation performed in this article can attain deep and high‐quality engravings in sapphire without necessitating volatile solutions or expensive equipment such as high‐power ultrashort‐pulsed lasers. The dominant mechanism of ablation is discovered to be from the direct ablation of excited sapphire surfaces and not from the plasma generated from the target material. Only an initial deposition from the target is needed to initiate the direct ablation. Note that 20‐µm wide, 30‐µm deep channel and hole features with a surface roughness (Sa) of .65 µm are achieved at an etching rate of .3 µm per pulse without the need for extensive cleaning. Engravings can reach up to 150‐µm depths at a maximum tapering angle of 5° until the shrinking absorbent surface vanishes, and 500‐µm wide 430‐µm deep topside through‐cutting is achieved. This study characterizes the morphology of direct laser ablation of transient absorbent sapphire surfaces. This method demonstrates the potential for the low‐cost rapid engraving of high aspect ratio features in transparent sapphire substrates.