Microsized subsurface modification of mono-crystalline silicon via non-linear absorption

Abstract

We introduce a novel method of optically inducing microsized subsurface structures using non-linear absorption of near infrared light in mono-crystalline silicon. We discuss the physical processes such as multi-photon absorption and self focussing in the material. The results presented in this paper demonstrate a new method of subsurface modifications in silicon and may open up novel avenues for optical devices embedded in silicon and optical process for the separation of wafers from their ingots.

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

“…However, no modifications could be created deeper inside silicon, when placing the focus inside the silicon layer [9]. Finally, evidence of subsurface damage was found in a recent study using an oil immersion objective with a numerical aperture of 1.25 [10]. However, despite the high numerical aperture, surface damage was reported [10].…”

“…Similar to dielectric materials, internal modifications could be applied for the inscription of optical devices [9,10]. As silicon is the material of choice for the production of integrated circuits, this may allow electronics and optical components to be integrated on a single chip [9].…”

“…Since multiphoton absorption depends on the square or higher powers of the intensity of the light, it allows for better confinement of the absorption of laser energy than can be achieved by merely focusing the beam. Recently, several authors studied the formation of subsurface modification in silicon using two-photon and three-photon absorption [9,10,17,18], in addition to studies that employed a photon energy near the band-gap of silicon [12,13,19]. The experimental conditions that were applied during these studies are listed in table 1.…”

Water-assisted pulsed Er:YAG laser interaction with silicon

“…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.…”

“…7,8 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. 8 To the best of the authors' knowledge, the Er:YAG laser processing of silicon has not been reported so far.…”