Morphological characterization of various kinds of materials in femtosecond laser micromachining

Abstract

We are developing applications of femtosecond-laser ablation to the practical material processing such as cutting, drilling, dicing and turning. In this work, we have observed the morphology of ablation traces formed on the surfaces of various materials to investigate the influence of physical properties of work materials on the machining preciseness. Ti:sapphire laser pulses (2 790 nm, r= 160 fs, f'= 10 Hz, E = 0.6 1.2 mJ/pulse) were focused on the samples, insulators (silica glass and PMMA), semiconductor (Si), and metals (Cu and Al), fixed on a PC-controlled X-Y stage and moved one-dimensionally at a scan rate of 5.5 111 pm/sec. Grooves with well-defmed edge were observed on the insulators which have low thermal conductivity. In the case of the metallic materials having relatively high thermal conductivity, molten walls were observed near the edge of the grooves. It is considered that mainly thermal conductivity plays an important role in characteristics of the ablation morphology.

Development of dicing technique for thin semiconductor substrate using temporally shaped femtosecond laser

“…Against this background, we have been developing a processing technique based on ablation by irradiation of pulse lasers [22][23][24]. In particular, we see great promise in the use of femtosecond lasers which can reduce the influence of heat on the substrate by injecting the energy into the material within a period much shorter than the nanosecond lasers which are used for conventional laser cutting processes.…”

“…We have already reported our experimental results using a silicon substrate 50 µm thick [22,23], intended to develop a new dicing technique for such thin silicon substrates. Generally, a smaller cutting width is better for sharp cutting.…”

Effects of femtosecond laser ablation on Vitrovac 6025X

“…However, at nanosecond laser ablation, Kawahara et al (2002) have suggested that thermal stresses may be introduced. This increases the material coercivity and reduces the permeability.…”

Time-Resolving Image Analysis of Drilling of Thin Silicon Substrates with Femtosecond Laser Ablation

“…Thus, we have developed a new dicing technique for such a thin silicon substrate, utilizing a photo machining process with a femtosecond laser. [23][24][25] We have already reported that the ablation induced by the femtosecond laser is very promising for dicing thin silicon substrates and clarified the influences of laser conditions, such as pulse duration and fluence, on cutting morphologies. [23][24][25] Although the thermal effect can be reduced considerably in the processing of silicon with the femtosecond laser compared with that in the case of using a nanosecond laser, it has not necessarily been removed completely.…”