Multi-photon absorption enhancement by dual-wavelength double-pulse laser irradiation for efficient dicing of sapphire wafers

Abstract

The evidence of multi-photon absorption enhancement by the dual-wavelength double-pulse laser irradiation in transparent sapphire was demonstrated experimentally and explained theoretically for the first time. Two collinearly combined laser beams with the wavelengths of 1064 nm and 355 nm, inter-pulse delay of 0.1 ns, and pulse duration of 10 ps were used to induce intra-volume modifications in sapphire. The theoretical prediction of using a particular orientation angle of 15 degrees of the half-wave plate for the most efficient absorption of laser irradiation is in good agreement with the experimental data. The new innovative effect of multi-photon absorption enhancement by dual-wavelength double-pulse irradiation allowed utilisation of the laser energy up to four times more efficiently for initiation of internal modifications in sapphire. The new absorption enhancement effect has been used for efficient intra-volume dicing and singulation of transparent sapphire wafers. The dicing speed of 150 mm/s was achieved for the 430 μm thick sapphire wafer by using the laser power of 6.8 W at the repetition rate of 100 kHz. This method opens new opportunities for the manufacturers of the GaN-based light-emitting diodes by fast and precise separation of sapphire substrates.

Spatial zigzag evolution of cracks in moving sapphire initiated by bursts of picosecond laser pulses for ultrafast wafer dicing

“…The maximum dicing speed of 300 mm s À1 for 430 mm thick sapphire achieved in this research using burst mode irradiation (9 ps, 5.5 W, 100 kHz) 2 times exceeded closest dicing speed of 150 mm s À1 achieved for the sapphire wafer with same thickness using picosecond dual-wavelength double-pulse irradiation (10 ps, 6.8 W, 100 kHz) patented 59 and reported in our previous work. 27 The enhancement of dicing speed by the factor of 2 using less powerful laser and the much simpler experimental setup is a promising result for industrial stealth dicing application by bust mode picosecond laser. Dicing speed achieved in our work was 6 times higher than the speed of 50 mm s À1 recorded by sub-picosecond Bessel beam (0.9 ps, 7.0 W, 100 kHz).…”

“…In the rst dicing scenario, using a tightly focused Gaussian beam with its related limited Rayleigh length the non-inclined modications with small modication height are formed, thus, several passes through the material are needed what limits the total dicing speed by the same factor. 27 In the second dicing scenario, using nondiffracting Bessel beams, modications over the whole height of the wafer are formed. However, by having a modication made by a single pulse, taking place overall height of wafer, the second modication feels previous modication and affects the propagation of the Bessel beam from top to bottom of the wafer.…”

“…However, several passes of laser beam translation at different depths are oen needed to break rather thick wafers. [24][25][26][27] That limits the total speed of the stealth dicing for thick material. Another promising technique is lamentbased machining, which offers the self-reconstruction of focal spot over long distances.…”

“…[34][35][36][37][38][39] To our knowledge, there is no scientic work in the literature reporting Bessel beam with picosecond pulse duration capable to induce volume modications in the bulk of sapphire. Stealth dicing of sapphire has been investigated for a variety of different pulse durations of femtoseconds, 40 picoseconds, 24,27 and nanoseconds. 41 However, there is no scientic work found in the literature for the stealth dicing of sapphire by using bursts of laser pulses.…”

Laser ablation of silicon with THz bursts of femtosecond pulses: an experimental and theoretical investigation

“…BM processing has been found to be beneficial for many applications like e.g. surface structuring [13][14][15][16] , multi-photon absorption enhancement 17 , and laser milling 9,10,18 . Despite the recent advances, there are still open questions on the physical mechanisms that come into play and influence the laser-matter interaction, when bursts of ultrashort pulses are used instead of single pulses, the latter known as normal pulse mode (NPM) irradiation.…”