Two-photon–induced internal modification of silicon by erbium-doped fiber laser

Abstract

Three-dimensional bulk modification of dielectric materials by multiphoton absorption of laser pulses is a well-established technology. The use of multiphoton absorption to machine bulk silicon has been investigated by a number of authors using femtosecond laser sources. However, no modifications confined in bulk silicon, induced by multiphoton absorption, have been reported so far. Based on results from numerical simulations, we employed an erbium-doped fiber laser operating at a relatively long pulse duration of 3.5 nanoseconds and a wavelength of 1549 nm for this process. We found that these laser parameters are suitable to produce modifications at various depths inside crystalline silicon.

Water-assisted pulsed Er:YAG laser interaction with silicon

“…However, beyond 0.96 J, it was observed that the Er:YAG laser interacted with silicon assisted by a water layer and was thermally damaged. For systematic investigation, we set the pulse energy to the maximum (1.16 J) and used pulse numbers of 1, 3,4,6,8,12,14,15,16,18,20, and 22. The whole experiment was repeated three times.…”

“…Recently, subsurface modification of silicon by 1.55 lm lasers was reported, where nonlinear light absorption was utilized. 7,8 Sreenivas et al used an 800 fs laser at 1.55 lm to induce subsurface damage by initiating twophoton absorption and self-focusing. 7 Similarly, Verburg et al reported that silicon subsurface modification was achieved by using a 3.5 ns laser with a wavelength of 1.549 lm via two-photon absorption.…”

“…7 Similarly, Verburg et al reported that silicon subsurface modification was achieved by using a 3.5 ns laser with a wavelength of 1.549 lm via two-photon absorption. 8 To the best of the authors' knowledge, the Er:YAG laser processing of silicon has not been reported so far. The Er:YAG laser, which has a wavelength of 2.94 lm, has an even smaller absorption coefficient than the CO 2 laser, and has a much smaller free carrier absorption cross section because it is proportional to wavelength squared (k 2 ).…”

Ultrafast-laser dicing of thin silicon wafers: strategies to improve front- and backside breaking strength

“…In both cases, wavelength, pulse duration, and focusing conditions are typically chosen such that the absorption takes place mainly inside the volume of the wafer [10,13]. In the first example, the laser acts as volume heat source that generates a stress field which causes the wafer to crack [10,11].…”

“…In the first example, the laser acts as volume heat source that generates a stress field which causes the wafer to crack [10,11]. In the case of stealth dicing [12,13], pulsed laser light is focused tightly below the surface to generate a defect inside the volume. To separate the dies, the crack or the defects can be guided by translating the beam across the wafer.…”