Ultra-short pulsed laser ablation of silicon nitride layers: Investigation near threshold fluence

Heinrich, G.; Wollgarten, Markus; Bähr, M.; Lawerenz, A.

doi:10.1016/j.apsusc.2012.10.122

Cited by 6 publications

(7 citation statements)

References 6 publications

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“…These defects are always detectable in the case of lift-off. 7,19 That means the laser pulse energy deposition in the silicon in the spot center is too low to melt it. Thus, the SiN x layer has to absorb almost the entire laser pulse energy by the already suggested absorption mechanism: Avalanche ionization induced by seed electrons from silicon 26 is forming ionization in highly absorbing electron-hole plasma.…”

Section: Discussionmentioning

confidence: 99%

“…These defects are always detectable when less laser fluence is used for a selective structuring by a lift-off. 7,19 Therefore, the direct laser ablation mechanism could even be a possible way to ablate entire dielectric layers without damaging the underlying silicon crystal (question 3).…”

Section: Discussionmentioning

confidence: 99%

“…3,[11][12][13][14] Instead of "lift-off," the terms "induced laser ablation," 15 "indirect laser ablation," 16 or "confined laser ablation" 17 are also used in the literature. As laser sources, UV fs/ps lasers, 7,18 VIS fs/ps lasers, 18,19 and IR fs/ps lasers 20,21 have been applied at low intensities. For the lift-off process, the laser pulse energy is mainly absorbed by the silicon substrate and not or very little in the transparent dielectric layer.…”

mentioning

confidence: 99%

“…As a result of the material expansion within a time of a few picoseconds, a pressure wave (also sound or shock wave in literature 22,23 ) is generated at the layer interface, causing the dielectric layer to bulge and initiating its lift-off due to high mechanical stress. 19 The silicon crystal is damaged due to heat and pressure wave induced defects like dislocations 7 or amorphization beneath the dielectric layer. 19 These defects are mainly generated due to fast resolidification (cooling rate about 10 13 K/s (Ref.…”

mentioning

confidence: 99%

“…19 The silicon crystal is damaged due to heat and pressure wave induced defects like dislocations 7 or amorphization beneath the dielectric layer. 19 These defects are mainly generated due to fast resolidification (cooling rate about 10 13 K/s (Ref. 24)) of the thin molten silicon volume.…”

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confidence: 99%

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Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Rapp

Heinrich

Wollgarten

et al. 2015

Journal of Applied Physics

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In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deeper understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN x ) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm 2 and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN x layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN x island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates. V C 2015 AIP Publishing LLC.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Rapp

Heinrich

Wollgarten

et al. 2015

Journal of Applied Physics

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Modelling picosecond and nanosecond laser ablation for prediction of induced damage on textured SiN_x/Si surfaces of Si solar cells

Shen

Hsiao

Wang

et al. 2021

Progress in Photovoltaics

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This study investigated the laser‐induced damage arising from 266 and 532 nm laser ablation of SiNx films on alkaline textured Si surfaces with nanosecond and picosecond pulse durations using a combination of optical‐thermal simulations and measurements of carrier recombination current density. Simulations predict that the melting depth is limited to within 150 nm of the SiNx/Si surface after 266 nm ps laser irradiation due to the greater absorption in both the SiNx and Si resulting in more direct ablation, while temperatures exceeding the melting temperature of Si are predicted to extend up to 1000 nm into the Si substrate with 532 nm ps pulses leading primarily to spallation. Ablation of the SiNx by 266 nm ps irradiation is predicted to be more homogeneous on smaller sized pyramids due to the increased absorption of double‐bounce reflected light on the pyramid faces. This finding has implications for applications requiring uniform ablation of dielectrics on textured Si surfaces. Ablation of SiNx by the longer wavelength 532 nm ps pulses also increases carrier recombination compared to that incurred with 266 nm ps pulses due to the increased melting depth. Longer ns pulses result in less steep temperature gradients and, for 266 nm pulses, an increased melting depth compared to ps pulses. Consequently, shorter ps UV pulses are preferred for SiNx ablation on Si surfaces due to their reduced laser damage penetration, whereas the less steep temperature gradients resulting from ns 532 nm pulses are beneficial for laser doping to form selective emitters.

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Selective femtosecond laser structuring of dielectric thin films with different band gaps: a time-resolved study of ablation mechanisms

2016

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Ultra-short pulsed laser ablation of silicon nitride layers: Investigation near threshold fluence

Cited by 6 publications

References 6 publications

Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Modelling picosecond and nanosecond laser ablation for prediction of induced damage on textured SiN_x/Si surfaces of Si solar cells

Selective femtosecond laser structuring of dielectric thin films with different band gaps: a time-resolved study of ablation mechanisms

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Ultra-short pulsed laser ablation of silicon nitride layers: Investigation near threshold fluence

Cited by 6 publications

References 6 publications

Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Modelling picosecond and nanosecond laser ablation for prediction of induced damage on textured SiNx/Si surfaces of Si solar cells

Selective femtosecond laser structuring of dielectric thin films with different band gaps: a time-resolved study of ablation mechanisms

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Modelling picosecond and nanosecond laser ablation for prediction of induced damage on textured SiN_x/Si surfaces of Si solar cells