The Combination of Direct and Confined Laser Ablation Mechanisms for the Selective Structuring of Thin Silicon Nitride Layers

Rapp, Stephan; Heinrich, G.; Domke, Matthias; Huber, Heinz P.

doi:10.1016/j.phpro.2014.08.011

Cited by 11 publications

(9 citation statements)

References 22 publications

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“…This assumption is supported by the investigation of the final ablation state: The SiN x layer is completely removed in the rim due to the selective lift-off, 2 whereas the lift-off is prevented in the center and the transition region due to direct laser absorption in the SiN x layer. 25,26 This combination of confined laser ablation at the rim and direct laser ablation in the center is related to the Gaussian spatial intensity distribution of the pump pulse having its highest intensity in the spot center (see threshold determination in Sec. III A).…”

Section: Discussionmentioning

confidence: 99%

“…Energy deposition is then caused by non-linear absorption at higher intensities. 25 Recently reported results show that besides the lift-off a partial direct ablation of dielectric silicon nitride (SiN x ) layers with IR laser pulses is feasible at fluences well above threshold. 26 In that work, the ablation of thin SiN x layers was investigated for IR laser pulses with pulse durations in the hundred femtosecond regime and fluences from 600 mJ/cm 2 to about 1500 mJ/cm 2 .…”

mentioning

confidence: 99%

“…The SiN x layer was selectively structured and only partially ablated by direct laser ablation in this area. 25 Due to the Gaussian fluence profile of the applied laser pulses, a combination of direct laser ablation in the center and confined laser ablation in the rim is observed. The thickness of the remaining SiN x layer increases with increasing radius from the center to the abrupt end at the lift-off area ( Figure 1, right side).…”

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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%

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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“…The environmental aspect of avoiding chemical process steps is also a crucial factor in many industries. USP laser structuring of thin films has already been investigated by many research groups, mainly focusing on the ablation of monolayers on semiconductor or glass substrates [14][15][16][17][18] .…”

Section: Introductionmentioning

confidence: 99%

Ultrashort pulse selective laser ablation of multi-layer thin film systems

Sassmannshausen

Mooraj²,

Kratz

2023

Laser-Based Micro- And Nanoprocessing XVII

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An experimental study on selective single pulse ablation of a SiO2/Si3N4-multilayer thin film system on fused silica substrate using ultrashort pulsed laser radiation with wavelengths of 343 nm, 515 nm and 1030 nm is presented. The effect of a NiCr metal interlayer and the influence of its thickness in the range of 0.5 -3 nm on the ablation behavior are investigated. Clean delamination can be achieved in thin film systems including a metal layer. A decreasing ablation threshold with decreasing laser wavelength is observed for the dielectric materials SiO2 and Si3N4. In contrast, the ablation threshold of the metal layer shows a negligible influence of the wavelength. However, a significant influence of the metal layer thickness on the ablation threshold is found, causing a decrease of the threshold fluence from 0.81 J/cm² for a NiCr layer thickness of 0.5 nm to 0.09 J/cm² for 3 nm thickness using IR laser radiation. The quality regarding the precision of ablation crater edges depends on the ablation mechanism. In the case of direct ablation due to absorption in the upper layer, a thermal effect is observed in the form of an ablation crater edge characterized by ridges of molten material. If there is a layer with a higher ablation threshold on top of the thin film stack, precise ablation with clean crater edges is caused by confined ablation due to absorption in the underlying layers.

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“…This is due to its high-quality polished surface (typically few nm for commercial Si wafers) and well-known infrared (IR) femtosecond (fs) laser-matter interaction physics [Bonse 2001, Gnilitskyi 2016. Multiple studies focused on ablation mechanisms and precise removal of up to a few hundred nanometers (nm) SiO 2 layer from the Si wafer have been performed with ns [Mangersnes 2010], ps [Herman 2009], but mostly by fs laser pulses [Rapp 2013, Rapp 2014, Rublack 2011a, McDonald 2007. There is also a strong dependence of the ablation mechanisms on wavelength [Hermann 2010], pulse duration [Rublack 2011b] and layer thickness [Hermann 2010].…”

Section: Introductionmentioning

confidence: 99%

Laser Induced Damage Threshold of Silicon With Native and Artificial Sio2 Layer

Sládek¹,

Mirza²

2019

MM SJ

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Spot size measurements of a 260 fs, 1030 nm focused spatially Gaussian pulsed laser beam were performed on a Silicon surface with native and thermally grown SiO 2 layers using a widely known method of evaluating laser beam energy dependent damage area. Single pulse laser induced damage thresholds of both samples were also measured. Modification of the thermally grown SiO 2 layer was analyzed in detail using optical, confocal and scanning electron microscopy. Restrictions in Gaussian beam spot size measurements on the samples with transparent coatings and several observable thresholds are discussed.

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The Combination of Direct and Confined Laser Ablation Mechanisms for the Selective Structuring of Thin Silicon Nitride Layers

Cited by 11 publications

References 22 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

Ultrashort pulse selective laser ablation of multi-layer thin film systems

Laser Induced Damage Threshold of Silicon With Native and Artificial Sio2 Layer

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