A novel patterning effect during high frequency laser micro-cutting of hard ceramics for microelectronics applications

- We study the occurrence of phase explosion in dielectrics with low thermal diffusivity compared to semiconductors.
- The periodicity of phase explosion in sapphire and glass is emphasized.
- Overlap ratio and pulse duration govern the mechanism behaviour.
- A relation was established between the phenomenon periodicity and the laser scribe depth.

This paper investigates the laser micro-cutting of wide band gap materials for microelectronics industry purposes. An ultraviolet (355 nm) diode-pumped solid-state (DPSS) nanosecond laser was used in this investigation. The laser energy varied from 7 to 140 μJ/pulse with typical frequencies from 40 to 200 kHz. The effect of pulse energy and scanning speed on the depth of the cutting street of α-Al2O3 and glass was studied. Typical depths of 200 μm were achieved on α-Al2O3 for 140 μJ/pulse, 40 kHz at 13 mm/s. SEM images showed periodic patterns produced by periodic explosive boiling that can influence the achieved depth. The shape, size and periodicity of the recast material depended on the feed rate and the laser beam frequency. This periodic removal mechanism seems to be specific to dielectrics since it was not observed for semiconductors such as silicon or silicon carbide.